Topics in Coal Geochemistry Short Course

Allan Kolker, Ph.D. Research Geologist U.S. Geological Survey Eastern Energy Resources Science Center Reston, Virginia [email protected]

U.S. Department of the Interior U.S. Geological Survey Global Coal Production and Use Review of Basic Coal Data Toward Global Emissions Standards SESSION I Session 1 Topic 1 GLOBAL COAL PRODUCTION AND USE

1.1-1 Global Coal Production and Export Producción y exportaciones mundiales de carbón

COAL PRODUCERS COAL EXPORTERS Producer Mt % of world Producer Mt total Australia 389 China 3,242 44.6 Indonesia 367 India 708 9.7 Russian Federation 147 United States 672 9.2 Colombia 83 Australia 503 6.9 South Africa 76 Indonesia 460 6.3 United States 46 Russian Federation 365 5.0 Mongolia 26 South Africa 257 3.5 Kazakhstan 26 Germany 176 2.4 Canada 24 Poland 131 1.8 DPR of Korea 21 Kazakhstan 98 1.3 Others 8 Colombia 91 1.3 Total 1,213 Canada 60 0.8 Rest of the World 506 7.0 World 7,269 99.8

Production data by country, includes steam coal, coking coal, lignite, and recovered coal, production in million tonnes (Mt), 2016 provisional data. Source: IEA, 2017, http://www.iea.org/publications/freepublications/publication/key-world-energy-statistics- 2017.html.

1.1-2 World Coal Proved Reserves Reservas probadas de carbón en el mundo Rank Country Total Reserves (Mt) Rank distribution

1. United States 237,295 All 2. Russian Federation 157,010 All 3. China 114,500 All 4. Australia 76,400 Bituminous, lignite 5. India 60,600 Bituminous, lignite 6. Germany 40,548 Lignite 7. Ukraine 33,873 Bituminous, sub-bituminous 8. Kazakhstan 33,600 Bituminous, lignite 9. South Africa 30,156 Bituminous 10. Indonesia 28,017 Sub-bituminous 11. Serbia 13,411 Lignite 12. Colombia 6,746 Bituminous 13. Brazil 6,630 Sub-bituminous 14. Canada 6,582 All 15. Poland 5,465 Bituminous, lignite

Source: World Energy Council, 2013 http://www.worldenergy.org/wp-content/uploads/2013/10/WER_2013_1_Coal.pdf.

1.1-3 Electricity from Coal Generación de energía eléctrica usando carbón

• France is lowest due to 100 Percent Electricity from Coal (2013) reliance on nuclear power. Source: World Bank 80 • Colombia, Canada each

Mongolia have significant hydro- SouthAfrica 60 Poland electric power and rely on China Kazakhstan India coal for only about 10% of 40

Australia their electric power. Indonesia World

20 Federation Russian • U.S. fraction slightly below Japan Colombia,Canada Turkey United States United

France world average. 0 • Countries with high Source: World Bank, 2013 reliance on coal (e.g., http://data.worldbank.org/indicator/EG.ELC.COAL.ZS. Poland, South Africa) lack alternatives. 1.1-4 Colombian Coal Production Producción colombiana de carbón

Colombia coal production and exports by year in Coal production for La Guajira (Guajira) thousand tonnes (kt). and Cesar compared to other Source: International Energy Agency, 2016 departments of Colombia (Other), in http://www.iea.org/statistics/statisticssearch/report/?country tonnes. =Colombia&product=coal. Source: World Coal, 2011 http://www.srk.com/files/File/UK%20PDFs/ 1.1-5 WorldCoal_Feb2011.pdf Coal Fields of Colombia Yacimientos colombianos de carbón

Cerrejón La Loma

Source: Tewalt and others, 2006 1.1-6 Colombia – Power Generation by Source Fuentes colombianas de energía

Generation in gigawatt hours (GWh). Source: International Energy Agency, 2016. 1.1-7 U.S. Coal Production (1980 – 2015) Producción de carbón de Estados Unidos

Source: U.S. Energy Information Administration, 2016 1.1-8 U.S. Coal Basins Cuencas carboníferas en Estados Unidos

Powder River Appalachian

Illinois

Source: East, 2013, USGS Open-File Report 2012-1205 1.1-9 U.S. Coal Production by Coal Basin Producción carbonífera de EE.UU. por cuenca

600 • Production declining in 500 Appalachian Basin and

400 Powder River Basin, the two largest producers. 300 Powder River Basin Appalachian Basin Illinois Basin • Production increasing 200 (through 2013) or steady 100

Coal production, millions of tons millions short production, Coal in Illinois Basin due to Source: U.S. Energy Information Agency 0 low transportation costs 2004 2006 2008 2010 2012 2014 2016 Year and increased use of FGD scrubbers in nearby Source: U.S. Energy Information Administration, 2016 power stations.

1.1-10 U.S Electric Power Sector (1980 – 2015) Generación de energía eléctrica en EE.UU.

In the U.S., gas-fired power generation has replaced some of the coal-fired capacity:

Coal

Natural Gas Nuclear

Source: U.S. Energy Information Administration, 2016 1.1-11 U.S Electric Power Generation (1990 – 2040) Generación de energía eléctrica en EE.UU.

2015 U.S. Energy Mix Coal – 33% Nat. Gas – 33% Nuclear – 20% Renewable – 13% Hydro – 6% Wind – 4.7% Biomass – 1.6% Solar – 0.6% Total ------99%

Source: U.S. Energy Information Administration, 2016, https://www.eia.gov/forecasts/aeo/pdf/0383(2016).pdf. 1.1-12 U.S. Power Generation by Region Generación de energía eléctrica en EE.UU. por regiones

Source: U.S. Energy Information Administration, 2016 1.1-13 U.S. Shale Gas Production (2007 – 2014) Producción de gas de lutita en EE.UU.

Source: U.S. Energy Information Administration, 2016 1.1-14 USGS Shale Gas Studies Gas de lutita en EE.UU.: bibliografía • U.S. Energy Information Administration projects continued increase in U.S. shale gas production from 2020 to 2040. • USGS fundamental studies of pore structure in gas shales to better understand gas occurrence and distribution. • Sampling and analysis of wastewater produced with oil and gas wells (produced water) and related environmental studies. • Can we see chemicals from hydraulic fracturing in wastewater produced from gas wells?

1.1-15 Carbon Capture and Storage Captura y almacenamiento de carbono

• Geologic carbon storage addressed in USGS assessment of storage capacity in underground saline reservoirs. • The regions with the largest storage resources are the Coastal Plains (mostly in Gulf Coast, 65%); Rocky Mountains and N. Great Plains (9%); and Alaska (9%; mostly North Slope). Power Generation • Related questions- – Environmental risks of storing CO2 in underground reservoirs?

– Potential for CO2 leakage, its impacts to drinking water, and induced seismicity? – Largest storage capacity not near greatest concentration of coal-fired powerplants. Source: USGS, 2013, Circular 1386 1.1-16 https://pubs.usgs.gov/circ/1386/ Summary – Topic 1: Global Coal Production and Use Resumen – Tema 1: Producción y consumo de carbón • Colombia is the 11th largest coal producer and the 4th largest exporter of coal in the world. • Coal production and exports have increased by about a factor of four in the last 20 years. • In Colombia only about 10% of electricity comes for coal which is among the lowest in the world. • Colombian coals are produced for export without preparation due to their low ash and sulfur contents. • Colombian coals are also much below world average contents of mercury.

1.1-17 Summary – Topic 1: Global Coal Production and Use Resumen – Tema 1: Producción y consumo de carbón • U.S. is the 3rd largest coal producer and the 6th largest coal exporter in the world. • U.S. coal production increased steadily until the mid-2000s, but has now begun to decline. • Currently, about 33% of U.S. electric power generation comes from coal, which is slightly below the world average and has decreased from about 50% in the last decade. • With discovery of large shale gas resources in the U.S., coal- fired generating capacity has been replaced by gas-fired generation. • The USGS has completed a national assessment of underground storage capacity for CO2.

1.1-18 References – Topic 1: Global Coal Production and Use Referencias – Tema 1: Producción y uso de carbones

East, J.A., 2013, Coal fields of the conterminous United States—National Coal Resource Assessment updated version: U.S. Geological Survey Open-File Report 2012–1205, one sheet, scale 1:5,000,000, https://pubs.usgs.gov/of/2012/1205/.

International Energy Agency [IEA], 2016, Colombia—Coal for 2015: International Energy Agency statistics search web page, accessed October, 17, 2016, at http://www.iea.org/statistics/statisticssearch/report/?country=Colombia&product=coal.

International Energy Agency [IEA], 2017, Key World Energy Statistics 2017: Paris, International Energy Agency, 97 p., accessed September 20, 2017, at http://www.iea.org/publications/freepublications/publication/key-world-energy-statistics.html-2017.

Tewalt, S.J., Finkelman, R.B., Torres, I.E., and Simoni, F., 2006, World coal quality inventory—Colombia, chap. 5 of Karlsen, A.W., Tewalt, S.J., Bragg, L.J., and Finkelman, R.B., eds., World Coal Quality Inventory—South America: U.S. Geological Survey Open-File Report 2006–1241, p. 132–157. [Also available at https://pubs.usgs.gov/of/2006/1241/Chapter%205-Colombia.pdf. [Note: Trace element data contained in this report, excluding mercury, are subject to revision.]

U.S. Energy Information Administration [EIA], 2016, Annual energy outlook 2016 with projections to 2040: Washington, D.C., U.S. Energy Information Administration, 256 p., accessed May 18, 2017, at https://www.eia.gov/forecasts/aeo/pdf/0383(2016).pdf.

U.S. Geological Survey [USGS], 2013, National Assessment of Geologic Carbon Dioxide Storage Resources—Results: U.S. Geological Survey Circular 1386, 41 p. [Also available at , https://pubs.usgs.gov/circ/1386/.]

World Bank, 2013, Electricity production from coal sources (% of total): The World Bank website, accessed October 28, 2016, at http://data.worldbank.org/indicator/EG.ELC.COAL.ZS.

World Coal, 2011, Coal in Colombia web page: World Coal website, accessed October 28, 2016, at https://www.worldcoal.com/coal/10022011/coal_in_colombia/.

World Energy Council, 2013, Coal, chap. 1 of World Energy Resources: London, World Energy Council, p. 1.1–1.32, accessed November 2, 2016, at http://www.worldenergy.org/wp-content/uploads/2013/10/WER_2013_1_Coal.pdf.

1.1-19 Session 1 Topic 2 REVIEW OF BASIC COAL DATA

1.2-1 Some Basic Points About Coal Generalidades sobre carbones

• Coal rank: Lignite, sub-bituminous, bituminous, anthracite, listed in order of increasing rank. • Generally, heating value increases and moisture decreases with increasing rank. • Noncombustible mineral matter in coal is referred to as ash or as mineral matter. Ash content is important in determining coal combustion characteristics and element mass-balance. • Generally, trace element concentrations in coal are greater in ash than in the organic fraction.

1.2-2 Coal – A Complex Natural Resource Carbón – Un complejo recurso natural • Circular 1143 (2003) is a good introduction to coal science. • Publication reviews coal quality and coal use in the U.S. with sections on coal origins, coal formation, mineral matter in coal, and health effects. Source: Schweinfurth, S.P., 2003, USGS Circular 1143, https://pubs.usgs.gov/circ/c1143/index.html.

1.2-3 Important ASTM Methods for Coal Normas ASTM para carbones

Method What it Does • D2234, 4596 Sample collection • How to collect coal samples. • D2013 Sample preparation • Grinding of coal for analysis. • D5865 Calorific value • Gives heating value of coal. • D3172 Proximate analysis • Gives percent ash, fixed carbon, moisture, volatiles. • D3176 Ultimate analysis • Gives percent ash, and total C, H, N, O, and S. • D2492 Forms of Sulfur • Gives amount of S in pyrite, as organic S, or as sulfate. • D388 Rank Classification • Classifies coal according to fixed carbon and heating value Source: ASTM International 2017a-j, http://www.astm.org (D5865 and D3172). 1.2-4 ASTM Coal Rank (ASTM D388) Calidades ASTM de carbones

• Rank classification is based on coal heating value (HV) or fixed carbon (FC) if FC is greater than 69%. • HV is adjusted to a mineral matter-free (MMF) basis. • FC is adjusted to a dry, MMF basis. • Most Colombian coals are high volatile bituminous.

Source: East, 2013 USGS Open-File Report 2012-1205, from ASTM D388 1.2-5 Example of ASTM D388 Rank Classification Ejemplo de clasificación ASTM D388

As-received determination for four Colombian coal samples (in percent except HV) Sample Formation/Bed Ash Moisture Fixed Sulfur Heating Heating (A) (M) Carbon (S) Value Value (FC) (HV) (HV) (Btu/lb) (MJ/kg) IGM Guaduas 5.86 0.85 60.26 0.73 14,690 34.2 1077 IGM Cerrejón 75 1.01 3.66 49.15 0.47 13,770 32.0 0073C IGM Cerrejón 115 0.53 3.89 55.76 0.63 13,520 31.4 0067C IGM Cerrito y 2.92 12.81 43.22 0.58 10,610 24.7 1238 Cienaga de Oro Source: Tewalt and others, 2006

FORMULAE (ASTM D388)* Values adjusted for ASTM D388 Rank determination Sample Formation/Bed FC (Dry HV (Moist HV (Moist ASTM Rank Fixed Carbon (FC) Dry-MMF: MMF) MMF, MMF, 100(FC-0.15S)/(100-(M + 1.08A + 0.55S)) Btu/lb) MJ/kg) IGM Guaduas 65.08 15,711 36.5 High Volatile A Heating Value (HV) Moist-MMF, Btu/lb: 1077 Bituminous 100(Btu-50S)/(100- (1.08A + 0.55S)) IGM Cerrejón 75 51.67 13,935 32.4 High Volatile B 0073C Bituminous To convert Btu/lb to MJ/kg, multiply by IGM Cerrejón 115 58.48 13,614 31.7 High Volatile B 0.0023255 0067C Bituminous *Assumes no S as sulfate IGM Cerrito y 51.52 10,962 25.5 High Volatile C 1238 Cienaga de Oro Bituminous or 1.2-6 Subbituminous A Coal Sampling Muestreo de carbones • ASTM D4596 Standard • Used to sample an entire Practice for Collection of coal bed. Top, bottom, and Channel Samples of Coal in partings are commonly a Mine. included. • ASTM D2234 Standard • Used for general sampling Practice for Collection of a run of mine coals or from a Gross Sample of Coal. stopped belt. Sample across entire belt if moving Collecting a or stopped. channel sample of coal using ASTM Sources: Schweinfurth, 2003, USGS Circular 1143; D4596. Golightly and Simon, 1989, USGS Bulletin 1823

1.2-7 Sampling Coal Ash Muestreo de cenizas • ASTM methods are not available for geochemical sampling of ash. • Collect fly ash samples in cans or rigid jars having a sealable airtight lid. • Collect from front, middle, and rear ESP hoppers. • Collect economizer fly ash and bottom ash if available. • Avoid putting hot ash directly into plastic containers!! Source: James Hower, Sampling University of Kentucky fly ash hoppers 1.2-8 Forms of Sulfur (ASTM D2492) Distintos tipos de azufre • Sulfur in coal has three forms- organic, pyritic, and sulfate. • Total sulfur is determined in D4239. • D2492 determines pyritic sulfur and sulfate sulfur. Organic sulfur is calculated by the difference as (total sulfur) – (pyritic sulfur + sulfate sulfur). • Freshly collected samples of unweathered coal should have little or no sulfate sulfur.

1.2-9 Examples of Sulfur Forms (ASTM D4239 + D2492) Ejemplos de distintos tipos de azufre South African Power Station Feed Coal (Low-Sulfur Coal; as-received basis) Sample KFC 2B Total Sulfur (%) 0.69 • Proportions of pyritic and Sulfate Sulfur 0.06 organic sulfur in coal are Pyritic Sulfur 0.31 Organic Sulfur (by difference) 0.32 highly variable.

U.S. Illinois Basin • In coal preparation, (High-Sulfur Coal; as-received basis) pyritic sulfur is reduced Samples IL-1 Raw IL-8 Cleaned Total Sulfur (%) 5.39 2.37 while organic sulfur is Sulfate Sulfur 0.01 0.01 retained. Pyritic Sulfur 4.46 0.88 Organic Sulfur (by difference) 0.92 1.48 • As organic fraction is Heating value (Btu/lb) 7,141 11,745 increased, so is heating Ukraine coal from outcrop value. in abandoned mine (as-received basis) Sample N-4A • Sulfate sulfur is minimal Total Sulfur (%) 3.08 Sulfate Sulfur 0.39 in unweathered samples; Pyritic Sulfur 1.37 Organic Sulfur (by difference) 1.32 higher in samples from outcrop. 1.2-10 Summary – Topic 2: Review of Basic Coal Data Resumen – Tema 2: Nociones básicas sobre carbones • Standardized analysis and reporting methods for coal quality parameters are available using ASTM methods. • Important parameters include mineral matter (ash) content, heating value, fixed carbon, sulfur content, and moisture. • Heating value and (or) fixed carbon expressed on a dry, ash- free basis determines ASTM coal rank. • Low rank coals have low heating values and high moisture contents. • Higher rank coals have higher heating values and lower moisture contents. • Sulfur forms include organic, pyritic, and sulfate. Proportions of organic and pyritic vary; sulfate is low in fresh coal samples and higher in weathered samples. 1.2-11 References – Topic 2: Review of Basic Coal Data Referencias – Tema 2: Fundamentos sobre carbones

ASTM International, 2017a, ASTM C618-17, Standard specification for coal fly ash and raw or calcined natural pozzolan for use in concrete: ASTM International website, accessed October 16, 2017, at https://www.astm.org/Standards/C618.htm. ASTM International, 2017b, ASTM D388-17, Standard classification of coals by rank: ASTM International website, accessed November 1, 2017, at https://www.astm.org/DATABASE.CART/HISTORICAL/D388-17.htm. ASTM International, 2017c, ASTM D2013/D2013M-12, Standard practice for preparing coal samples for analysis: ASTM International website, accessed October 19, 2017, at https://www.astm.org/Standards/D2013.htm. ASTM International, 2017d, ASTM D2234/D2234M-17, Standard practice for collection of a gross sample of coal: ASTM International website, accessed October 19, 2017, at https://www.astm.org/Standards/D2234.htm. ASTM International, 2017e, ASTM D2492-02(2012), Standard test method for forms of sulfur in coal: ASTM International website, accessed October 20, 2017, at https://www.astm.org/Standards/D2492.htm. ASTM International, 2017f, ASTM D3172-13, Standard practice for proximate analysis of coal and coke: ASTM International website, accessed October 20, 2017, at https://www.astm.org/Standards/D3172.htm. ASTM International, 2017g, ASTM D3176-15, Standard practice for ultimate analysis of coal and coke: ASTM International website, accessed October 19, 2017, at https://www.astm.org/Standards/D3176.htm. ASTM International, 2017h, ASTM D4239-17, Standard test method for sulfur in the analysis sample of coal and coke using high-temperature tube furnace combustion: ASTM International website, accessed October 24, 2017, at https://www.astm.org/Standards/D4239.htm. ASTM International, 2017i, ASTM D4596-09 (2015), Standard practice for collection of channel samples of coal in a mine: ASTM International website, accessed October 24, 2017, at https://www.astm.org/Standards/D4596.htm. ASTM International, 2017j, ASTM D5865-13, Standard test method for gross calorific value of coal and coke: ASTM International website, accessed October 24, 2017, at https://www.astm.org/Standards/D5865.htm. East, J.A., 2013, Coal fields of the conterminous United States—National Coal Resource Assessment updated version: U.S. Geological Survey Open-File Report 2012–1205, one sheet, scale 1:5,000,000. [Also available at https://pubs.usgs.gov/of/2012/1205/. Golightly, D.W., and Simon, F.O., eds., 1989, Methods for sampling and inorganic analysis of coal: U.S. Geological Survey Bulletin 1823, 72 p. [Also available at https://pubs.usgs.gov/bul/b1823/. Schweinfurth, S.P., 2003, Coal—A complex natural resource: U.S. Geological Survey Circular 1143, 39 p. [Also available at https://pubs.usgs.gov/circ/c1143/.] Tewalt, S.J., Finkelman, R.B., Torres, I.E., and Simoni, F., 2006, World coal quality inventory—Colombia, chap. 5 of Karlsen, A.W., Tewalt, S.J., Bragg, L.J., and Finkelman, R.B., eds., World Coal Quality Inventory—South America: U.S. Geological Survey Open-File Report 2006–1241, p. 132–157. [Also available at https://pubs.usgs.gov/of/2006/1241/Chapter%205-Colombia.pdf. [Note: Trace element data contained in this report, excluding mercury, are subject to revision.]

1.2-12 Session 1 Topic 3 TOWARD GLOBAL EMISSIONS STANDARDS

1.3-1 Paris Agreement on Climate Change Acuerdo de Paris sobre cambio climático • Paris Agreement adopted on 12 December, 2015. Every country is expected to have a plan to reduce carbon emissions. • Plans will be revisited every 5 years and countries are required to monitor their progress in reducing carbon emissions using a specified uniform approach. • Agreement goes into effect 30 days after at least 55 signers representing an estimated 55% of emissions ratify the treaty. • Currently (Nov., 2017), 197 parties have signed the agreement and it has been ratified or accepted by 169 countries. • 55/55 status was reached on 5 October, 2016 so the agreement went into effect on 4 November, 2016. • June 1, 2017, U.S. President announces intent to withdraw from the Paris Agreement. Source: United Nations, 2017, http://unfccc.int/paris_agreement/items/9485.php. 1.3-2 Limiting U.S. Carbon Emissions Reducción de emisiones por carbones en EE.UU. • U.S. EPA Clean Power Plan (CPP, 2015) limits power plant carbon pollution. • National emissions standards with some flexibility in State approaches to compliance. • Benefit in emissions reduction and health impacts. • 32% carbon reduction goal relative to 2005 emissions by a 2030 time frame. • October, 2017, EPA proposes repealing the CPP following Executive order calling for its review. Source: U.S. Environmental Protection Agency, 2015 https://www.epa.gov/cleanpowerplan. 1.3-3 Minamata Convention on Mercury Tratado de Minamata sobre mercurio

• 2013 global treaty to protect human health and the environment from the adverse effects of mercury. • Controls anthropogenic release of mercury and limits other mercury uses. • Includes a ban on new mercury mines, phase-out of existing ones, controls on air emissions, and regulation of mercury used in artisanal and small-scale gold mining. • 128 countries are signatory with 84 ratifications (min. 50). • Treaty entered into force on 16 August, 2017. Source: United Nations Environment Programme (UNEP), 2016 Minamata Convention on Mercury, http://mercuryconvention.org/.

1.3-4 U.S. EPA Mercury and Air Toxics Standards (MATS) Normas sobre contaminación atmosférica en EE.UU.

• Standards limit emissions of mercury, other trace elements (Be, Cr, Mn, Co, Ni, As, Se, Sb, and Pb), and acid gasses, including HF and HCl. • Standards apply to coal- and oil-fired generating units ≥ 25 megawatts. • MATS implementation went into effect in 2016.

Source: U.S. EPA, 2011a, https://www.epa.gov/mats.

1.3-5 Rationale For U.S. EPA MATS Justificación de las normas

• Power plants are the largest source of U.S. mercury emissions. • People are exposed to mercury by eating contaminated fish. • Other toxic metals from power plants, such as arsenic, chromium and nickel, can cause cancer. • EPA estimates that implementation of MATS will have health benefits avoiding: 4,200 to 11,000 premature deaths 4,700 nonfatal heart attacks Source: U.S. EPA , 2011a 2,600 hospitalizations for respiratory https://www.epa.gov/mats and cardiovascular diseases Source: U.S. EPA, 2011b, https://www3.epa.gov/ttn/ecas/regdata/RIAs/matsriafinal.pdf.

1.3-6 Rationale For U.S. EPA MATS Justificación de las normas Sources of U.S. Mercury Emissions Industrial 1990 Emissions 2005 Emissions Percent Reduction 2016 Status Category (tons per year) (tons per year) Power Plants 59 53 10% Not Regulated

Municipal Waste 57 2 96% Regulated Combustors Medical Waste 51 1 98% Regulated Incinerators

Source: U.S. EPA, 2011a https://www.epa.gov/mats

Source: Kolker and others, 2012.

Map Showing U.S Fish Consumption Advisories for Mercury (2010) 1.3-7 Summary – Topic 3: Global Emissions Standards Resumen – Tema 3: Normas sobre emisiones

• Global emissions limits for CO2 through the Paris Agreement, and mercury, through the Minamata Convention, are being adopted. • Conditions for ratification the Paris Agreement have been met, but after ratifying the Agreement, the U.S. announced its intent to withdraw from the Paris Agreement. The Agreement allows flexibility in the approach each country may take to reduce their CO2 emissions. • The Minamata Convention has now entered into force. The Convention includes limits on primary mercury production, mercury used in gold mining, and mercury emissions from coal. The U.S. was the first country to ratify the Minamata Agreement and remains a party to the Convention. • The U.S. EPA has introduced plans to limit U.S. carbon and mercury emissions from coal combustion by its Clean Power Plan and its Mercury and Air Toxics Standards, respectively. The MATS standards are being implemented at U.S. utility power stations, but the EPA has now proposed repealing the Clean Power Plan.

1.3-8 References – Topic 3: Global Emissions Standards Referencias – Tema 3: Normas sobre emisiones

Kolker, A., Quick, J.C., Senior, C.L., and Belkin, H.E., 2012, Mercury and halogens in coal—Their role in determining mercury emissions from coal combustion: U.S. Geological Survey Fact Sheet 2012–3122, 6 p. [Also available at https://pubs.usgs.gov/fs/2012/3122/.]

United Nations Environment Programme [UNEP], 2016, Minamata Convention on Mercury: United Nations Environment Programme website, accessed November 14, 2016 at http://mercuryconvention.org/.

United Nations [Framework Convention on Climate Change], 2017, Paris Agreement web page: United Nations Framework Convention on Climate Change website, accessed November 13, 2017, at http://unfccc.int/paris_agreement/items/9485.php.

U.S. Environmental Protection Agency [EPA], 2011a, Mercury and air toxics standards (MATS) web page: EPA website, accessed November 15, 2016, at https://www.epa.gov/mats.

U.S. Environmental Protection Agency [EPA], 2011b, Regulatory impact analysis for the final mercury and air toxics standards: Research Triangle Park, North Carolina, U.S. Environmental Protection Agency Office of Air Quality Planning and Standards, Health and Environmental Impacts Division, EPA–452/R–11– 011, 510 p., accessed -November 15, 2017, at https://www3.epa.gov/ttn/ecas/regdata/RIAs/matsriafinal.pdf.

U.S. Environmental Protection Agency [EPA], 2015, The clean power plan web page: EPA website, accessed November 7, 2017, at https://archive.epa.gov/epa/cleanpowerplan.html.

1.3-9 Trace Elements in Coal Trace Elements in Fe-Disulfides Introduction to Mercury in Coal SESSION 2 Session 2 Topic 1 TRACE ELEMENTS IN COAL

2.1-1 Why Study Trace Elements in Coal? Justificación del estudio de elementos traza • Differences in coal quality affect operation of coal-fired utility power stations and their emissions. • An understanding of trace-metal distribution in coal is needed to: – Predict powerplant emissions. – Predict element behavior in coal preparation. – Control release of metals from coal and coal combustion materials to groundwater. – Minimize health consequences of coal use.

2.1-2 Effects of Inorganic Substances on Coal Utilization Efectos de compuestos químicos en la combustión

Element Effect • Sodium • Boiler Fouling • Iron • Boiler Slagging • Chlorine • Corrosion; Mercury Capture • Silicon • Erosion of Combustors (Quartz)

2.1-3 Mode of Occurrence Concept Modo de ocurrencia de los elementos químicos

• Definition- Understanding the chemical form of an element present in coal. • Importance- Determines element behavior during coal combustion and potential for removal. Determines environmental impact, technological behavior and byproduct potential. Can provide information on geologic history.

2.1-4 Element Modes of Occurrence Modo de ocurrencia de los elementos químicos

Organic Association Inorganic Association (Maceral) (Mineral) • Ionic bound to maceral • Solid solution (e.g., As • Covalent bound to for S in pyrite; Cr in illite/smectite; Cd in maceral sphalerite) • Moisture • Essential Structural Constituent (e.g., Galena [PbS])

2.1-5 Generalized Minerals in Coal Presencia de minerales en carbones

Major constituents Trace constituents

• Quartz: (SiO2) • Quartz: None measured • Clays: • Clays: Kaolinite (Al2Si2O5(OH)4) Kaolinite: None measured Illite-smectite (K,Al,Si,Fe,Mg) Illite-smectite: Cr, V • Fe-disulfides: • Fe-disulfides: As, Hg, Se, Sb, Ni. Pyrite, marcasite (both FeS2) Arsenopyrite (FeAsS) very rare. • Carbonates: Calcite (CaCO3) dolomite • Carbonates: Divalent alkaline earths (Ca,Mg), ankerite (Ca,Fe,Mg,Mn), (Sr, Ba).

siderite (FeCO3) • Trace phases: Are sources of their • Trace phases: Chalcopyrite (CuFeS2), respective constituents. No common sphalerite (ZnS), galena (PbS), Cd trace phase but present at percent

clausthalite (PbSe), zircon (ZrSiO4), level in sphalerite. All but PbSe are allanite (Ca,REE,Al,Fe,Si). common in rocks. Sources: Finkelman, 1981; Kolker and Finkelman, 1998; Finkelman and others, 2018

2.1-6 Minor/Trace Phases Elementos menores y elementos traza

Formula or Mineral Major Components Minor Elements Galena (PbS) Sphalerite (ZnS) Cd Chalcopyrite (CuFeS2) Clausthalite (PbSe) Crandallite Group (Ca, Al, P) Ba, Sr, REE Monazite (REE, P) Th Xenotime (YPO4) REE Apatite (Ca, P) REE Zircon (ZrSiO4) U, Pb, Th Rutile (TiO2) Barite (BaSO4) Feldspars (Ca, Na, K, Al, Si) Micas (K, Fe, Mg, Ti, Al, Si) Zeolites (Ca, Na, K, Al, Si)

2.1-7 Metals in Coal Elementos metálicos en carbones

• Emissions of Sb, As, Be, Cd, Cr, Co, Pb, Hg, Mn, Ni, Se regulated under EPA Mercury and Air Toxics Standards. • As, Sb, Se, Cd, Hg, Co, Pb commonly have a sulfide association in bituminous coals. • Mn, Cr, Ni, Be can have mixed associations: Cr, Ni in illite-smectite clays and organics Mn in carbonates, clays, and organics Be in silicates (clays) and possibly organics • Mineral-associated elements can be reduced by coal preparation (washing).

2.1-8 How to Study Trace Elements in Coal Cómo estudiar elementos traza

Bulk Methods Microanalysis Whole Sample Specific Minerals • X-Ray Diffraction- Minerals in • Scanning Electron Microscope bulk coal after low-temp. (SEM)- Texture and distribution of combustion of organics. minerals in coal individually. • Chemical Analysis- Element • Electron microprobe- Most distribution, e.g., by ICP-MS. abundant elements in individual • Selective leaching- Element minerals. forms (species) inferred from • Laser Ablation ICP-MS and Ion leaching behavior. Microprobe- Trace elements in • X-ray absorption fine structure individual minerals. (XAFS)- Element species • Transmission Electron determined directly by structure Microscope (TEM)- Minerals in of X-ray absorption edge. coal individually at very fine scale. 2.1-9 About Moisture Humedad

• Generally, heating value increases and moisture decreases with increasing rank. Need to know moisture content to accurately express elemental concentrations in coal. • Moisture contents range from about 2% in bituminous coals to as much as 30% in low rank coals. Perfect analyses determined on a dry basis can be off by as much as 30% if moisture is not taken into account. • Moisture content can change if samples are not analyzed promptly after collection.

2.1-10 Arsenic in Coal Arsénico

• Arsenic is a persistent toxin that occurs in trace amounts in rocks, sediments, and coal. • All coals contain some arsenic. Arsenic contents vary considerably by coal basin. • In bituminous coals, arsenic occurs primarily in pyrite, with lesser amounts in organic portions of coal. • A small fraction of arsenic present in coal is emitted to the atmosphere during coal combustion. Direct exposure to arsenic in coal may • Source: Kolker and others, 2006a, occur where coal is used in the home for USGS Fact Sheet 2005-3152 cooking and heating. https://pubs.usgs.gov/fs/2005/3152/

2.1-11 Leaching Procedure for Coal Samples Lixiviación de carbones

4-step leaching procedure for: 1) Ion-exchangeable organic-bound 2) Acid-soluble salts 3) Silicates 4) Sulfides

Source: Palmer and others, 1998, Proceedings, International Pittsburgh Coal Conference

2.1-12 Selective Leaching of Arsenic in U.S. Coals Lixiviación de arsénico en carbones en EE.UU.

Coal Rank Sub- • Results from selective Bituminous Bituminous leaching studies of bulk coal show a Acids

predominant pyritic HNO3 (nitric acid leached) association. HF • Pyritic association is less pronounced in HCl two low-rank coals. • Unleached fraction interpreted to be arsenic in the organic portion of coal. Source: Palmer and others, 1998, Proceedings, International Pittsburgh Coal Conference

2.1-13 Arsenic Oxidation Oxidación del arsénico

• Over time arsenic in coal Pyrite in Coal undergoes oxidation to an 3- 2500 2070 arsenate (AsO4) form that is analogous to sulfate (SO )2-. 2000 1570 4 1500 • What happens when pyrite is 1000 440 enriched in As? As (ppm) 500 150 200 • Experimental study over 18 0 months comparing behavior of five U.S. bituminous coals Springfield having different extents of PittsburghPittsburgh #2 Alabama #1 LM-1Alabama TP-1 arsenic substitution in pyrite. Mean values for As in pyrite based on • Monitoring of arsenic species quantitative electron microprobe analysis of by As-XANES, a spectroscopic about 100 analysis points per sample. method. Source: Kolker and Huggins, 2007 Applied Geochemistry

2.1-14 Spontaneous Arsenic Oxidation in Coal Oxidación espontánea del arsénico Air Dry Samples Monitoring by As-XANES 40 LM-1 4 30 TP-1 As-Pyrite Pittsburgh No. 1 • Arsenate forms 3.5 Arsenate Air-Dry: All Stages 20 Spfld As: 85% pyrite; 15% arsenategradually with Pitts 1 3 10 % Arsenate Pitts 2 Stage 3 2.5 time under dry 0 As: 89% pyrite; 11% arsenate 0 2 4 6 8 10 12 14 16 18 2 conditions. Stage 2 Months 1.5 • Under wet Norm. Absorption Norm. 1 conditions, As: Stage93% pyrite; 1 7% arsenate Air Wet Samples 0.5 arsenate forms 100 0 much more LM-1 -40 -20 0 20 40 60 80 100 80 rapidly. TP-1 Energy, eV 60 Spfld 40 Pitts 1

% Arsenate 20 Source: Kolker and Huggins, 2007 Pitts 2 0 Applied Geochemistry 0 2 4 6 8 10 12 14 16 18 Months

2.1-15 Selective Leaching vs. XAFS for Arsenic Species Dos técnicas para el análisis de arsénico • Proportion of arsenic in the arsenate form was compared using synchrotron As XANES (XAFS) vs. selective leaching. • Leaching arsenate fraction obtained by combining arsenic leached in the HCL and HF fractions. • Both methods give similar arsenate proportions and show progressive increase with time. Source: Huggins and others, 2002, Energy and Fuels 2.1-16 Selective Leaching of Arsenic in U.S. Coals Lixiviación de arsénico en carbones de EE.UU. Coal Rank Sub- • Results from selective Bituminous Bituminous leaching studies of bulk coal show a predominant pyritic Acids association. HNO3 • Pyritic association is less HF pronounced in two low- rank coals. HCl • Un-leached fraction interpreted to be arsenic in the organic portion of coal. • HF + HCl fraction interpreted as the arsenate fraction. Source: Palmer and others, 1998, Proceedings, International Pittsburgh Coal Conference

2.1-17 Summary – Topic 1: Trace Elements in Coal Resumen – Tema 1: Elementos traza en carbones • Trace elements can have an organic, an inorganic, or a combined association, but in bituminous coals, the inorganic (mineral) association is predominant. • Bulk analysis gives the total amount of an element present in all associations. • Direct (e.g., microanalysis, spectroscopic methods) or indirect (e.g., selective leaching) methods are needed to determine element mode of occurrence in coal.

2.1-18 Summary – Topic 1: Trace Elements in Coal (continued) Resumen – Tema 1: Elementos traza en carbones • Arsenic commonly occurs in trace amounts in coal. • A portion of the arsenic present in coal is emitted during coal combustion and some is retained in coal combustion products. • Arsenic occurs primarily in pyrite in bituminous coals with a greater portion or organic-associated arsenic in low rank coals. • Arsenic in coal undergoes oxidation to arsenate similar to sulfur oxidation to sulfate.

2.1-19 References – Topic 1: Trace Elements in Coal Referencias – Tema 1: Elementos traza en carbones

Finkelman, R.B., 1981, Modes of occurrence of trace elements in coal: U.S. Geological Survey Open-File Report 81–99, 315 p. [Also available at https://pubs.er.usgs.gov/publication/ofr8199.]

Finkelman, R.B., Palmer, C.A., and Wang, P., 2018, Quantification of the modes of occurrence of 42 elements in coal: International Journal of Coal Geology, v. 185, p. 138–160, accessed September 11, 2018, at https://doi.org/10.1016/j.coal.2017.09.005.

Huggins, F.E., Huffman, G.P., Kolker, A., Mroczkowski, S.J., Palmer, C.A., and Finkelman, R.B., 2002, Combined application of XAFS spectroscopy and sequential leaching for determination of arsenic speciation in coal: Energy and Fuels, v. 16, no. 5, p. 1167–1172. [Also available at https://doi.org/10.1021/ef0200166.]

Kolker, A., and Finkelman, R.B., 1998, Potentially hazardous elements in coal—Modes of occurrence and summary of concentration data for coal components: Coal Preparation, v. 19, nos. 3–4, p. 133–157. [Also available at https://doi.org/10.1080/07349349808945578.]

Kolker, A., Palmer, C.A., Bragg, L.J., and Bunnell, J.E., 2006a, Arsenic in coal: U.S. Geological Survey Fact Sheet 2005–3152, 4 p. [Also available at https://pubs.usgs.gov/fs/2005/3152/.]

Kolker, A., and Huggins, F.E., 2007, Progressive oxidation of pyrite in five bituminous coal samples—An As XANES and 57Fe Mössbauer spectroscopic study: Applied Geochemistry, v. 22, no. 4, p. 778–787. [Also available at https://doi.org/10.1016/j.apgeochem.2006.10.006.]

Palmer, C.A., Mroczkowski, S.J., Finkelman, R.B., and Crowley, S.S., 1998, The use of sequential leaching to quantify the modes of occurrence of elements in coals in Proceedings, Fifteenth Annual International Pittsburgh Coal Conference, September 14–18, 1998, Pittsburgh, Pennsylvania, USA: Pittsburgh, Pa., Annual International Pittsburgh Coal Conference, CD-ROM, 47-p .

2.1-20 Session 2 Topic 2 TRACE ELEMENTS IN FE-DISULFIDES IN COAL

2.2-1 Why Study Fe-Disulfides (FeS2) in Coal? Justificación del estudio de disulfuros de hierro • Fe-disulfides (pyrite, marcasite) are common minerals in coal, controlling the distribution of As, Hg, Se, etc., especially in bituminous coals. A source of air and water pollutants. • Knowing the distribution of minor elements in pyrite can help optimize strategies for coal preparation. • Minor element variation shows differences resulting from changes in fluid chemistry during diagenesis. • Minor element substitution can influence the stability of Fe- disulfides, affecting the rate of pyrite oxidation and formation of acid mine drainage (AMD).

2.2-2 Compilation of minor elements in Fe-disulfides in coal Elementos traza en disulfuros de hierro en carbones Sulfide Co Ni Cu Zn As Se Sb Hg Pb Method Pyrite dl - 1.5% dl - 0.20 % EPMA Pyrite dl - 3.5% EPMA Pyrite to 4.5% EPMA Pyrite dl - 2,300 dl - 4,500 dl - 4.9 % dl - 1,000 EPMA Pyrite dl – 0.16% dl – 0.16% dl – 0.16% dl – 0.04% dl – 2.68% dl – 0.06% dl - 0.04% EPMA Pyrite 0.02 – 1.03% – 0.04% – dl – 0.47% EPMA1 0.12% 5.76% 0.12% Pyrite dl – 0.29% 0.03% – dl – 0.79% dl – 0.05% dl – 0.92% dl – 0.14% EPMA 1.37% Pyrite 0 - 30 0 - 160 dl – 1.73% dl - 590 dl - 140 dl – 104 dl - 18 LA ICP-MS2 Pyrite 46 36 12 227 LA ICP-MS Pyrite dl - 161 dl - 375 dl - 214 dl - 31 dl – 1.2% dl - 250 dl - 39 dl - 1962 Micro-PIXE3 Pyrite 125 - 4,500 15 - 4,750 11 - 532 42 - 171 20 - 5,520 PIXE4 Pyrite dl- 4,510 15 - 3,420 11 - 321 20 - 5,520 PIXE Pyrite 7 - 3,260 19 - 1.3 % 0 - 1,250 4 - 2,930 SXRF Pyrite dl - 968 dl - 29 LA ICP-MS5 Pyrite 13.8 – 23.1 227 – 32.2 - 45 2.5 -2.5 INAA 1,210 Marcasite 4.8 51 dl 1.6 LA ICP-MS Marcasite 25 - 2,740 30 - 3.4 % 2 - 452 43 - 4,100 SXRF 1Ding and others, 2001 Southwestern Guizhou Province, China 2Diehl and others, 2004 Warrior field, Black Warrior Basin, Alabama, USA From Kolker, 2012, Int. J. of Coal Geology; 3Hower and others, 2008 Manchester coal bed, eastern Kentucky, USA values in ppm and (or) wt. % 4Hickmott, 1993 L. Kittanning, U. Freeport, Menefee, and Fruitland coals, USA 5Kolker and others, 2006b Ohio 5/6/7, Illinois #6, and Pittsburgh coals, USA 2.2-3 Substitution of Minor Elements in FeS2 Sustitución de elemetos traza en FeS2

Substitution for Fe2+ Substitution for S- • Co2+, Ni2+, Cu2+, Zn2+ • As-, Se-, Sb-, etc. • Poor fits: Pb2+, *Hg2+, etc. • Coupled substitution: As3+ and Au+ Other trivalent plus monovalent combinations Source: Deditius and others, 2008, Geochimica et. Cosmochimica Acta

*Oxidation state of Hg is assumed to be Hg2+, but is uncertain.

2.2-4 Generations of Iron Disulfides in Coal Formación de disulfuros de hierro en carbones

• Multiple generations are commonly present and each may show minor element variation. • Framboidal pyrite is always the earliest generation, commonly overgrown by subhedral pyrite. • Cleat- or vein-filling pyrite are the latest pyrite generations as shown by crosscutting relations and compositional differences.

2.2-5 Framboids and their Overgrowths Desarrollo de estructuras cristalinas

Backscattered Electron (BSE) Images 1 2

3 10 µm 50 µm 20 µm 4 5 6

20 µm 10 µm 50 µm

1) Staunton Formation, Indiana, USA; 2) Pittsburgh, West Virginia, USA Source: Kolker, 2012 3)Donets Basin, Ukraine; 4) Staunton Formation, Indiana, USA International Journal 5) Donets Basin, Ukraine; 6) Illinois #6, Indiana, USA of Coal Geology 2.2-6 Alabama, USA Warrior Basin Coal Carbones en la cuenca Warrior, Alabama, EE.UU. Warrior Basin is enriched in arsenic:

B Arsenic enrichment seen in: A. Subhedral framboid overgrowths Wavelength–dispersive electron microprobe element maps B. Oscillatory-zoned aresenian pyrite C. Cleat pyrite Source: Goldhaber and others, 2003 Typically, framboidal pyrite is arsenic poor Arsenic in Ground Water

2.2-7 Donetsk-Makeevka District, Ukraine Distrito Donetsk-Makeevka, Ucrania Donetsk is enriched in Hg and As:

BSE As values in weight percent

Source: Kolker and others, 2009 Wavelength–dispersive electron microprobe element maps International Journal of Coal Geology

2.2-8 As and Se Enrichment in Fe-disulfides Enriquecimiento en As y Se de disulfuros de hierro

Wavelength–dispersive electron microprobe element maps: A B As As A. Alabama, USA B. Ukraine C. Alabama, USA D. West Virginia, USA 20 µm As E. West Virginia, USA F. Ukraine D E F

Source: Kolker, 2012 International Journal of Coal Geology 50 µm As 50 µm Se 50 µm As

2.2-9 Nickel Enrichment in Framboids Enriqueciento en niquel

A B

20 µm Ni BSE 10 µm Ni

C A. Pittsburgh Coal, Appalachian Basin, West Virginia, USA B. Raccoon Creek Group Coal, Illinois Basin, Indiana, USA C. H10 Middle Coal Bed, Donets Basin, Ukraine

Source: Kolker, 2012 International Journal of Coal Geology 20 µm Ni

2.2-10 Summary – Topic 2: Fe-Disulfides in Coal Resumen – Tema 2: Disulfuros de hierro en carbones

• Fe-disulfides in coal contain trace elements of environmental interest such as As, Se, Ni, and Hg. • Multiple generations of Fe-disulfides are common. Framboidal pyrite is always the earliest generation and cleat (fracture-filling) pyrite is latest. • Different Fe-disulfide generations may have different trace element characteristics. Framboidal pyrite is commonly Ni rich but As poor. • Overgrowths on framboidal pyrite may be As or Se enriched, especially if coals have interacted with fluids enriched in these elements. • Removal of Fe-disulfides in coal preparation will help reduce the concentrations of harmful elements such as As and Se.

2.2-11 References – Topic 2: Trace Elements in FeS2 Referencias – Tema 2: Elementos traza en FeS2

Deditius, A.P., Utsunomiya, S., Renock, D., Ewing, R.C., Ramana, C.V., Becker, U., and Kesler, S.E., 2008, A proposed new type of arsenian pyrite—Composition, nanostructure and geological significance: Geochimica et Cosmochimica Acta, v. 72, no. 12, p. 2919–2933. [Also available at https://doi.org/10.1016/j.gca.2008.03.014.]

Diehl, S.F., Goldhaber, M.B., and Hatch, J.R., 2004, Modes of occurrence of mercury and other trace elements in coals from the warrior field, Black Warrior Basin, northwestern Alabama: International Journal of Coal Geology, v. 59, nos. 3–4, p. 193–208., [Also available at https://doi.org/10.1016/j.coal.2004.02.003.]

Ding, Z., Zheng, B., Long, J., Belkin, H.E., Finkelman, R.B., Chen, C., Zhou, D., and Zhou, Y., 2001, Geological and geochemical characteristics of high arsenic coals from endemic arsenosis areas in southwestern Guizhou Province, China: Applied Geochemistry, v. 16, nos. 11–12, p. 1353–1360. [Also available at https://doi.org/10.1016/s0883- 2927(01)00049-x.]

Goldhaber, M.B., Lee, R.C., Hatch, J.R., Pashin, J.C., and Treworgy, J., 2003, Role of large scale fluid-flow in subsurface arsenic enrichment, in Welch, A.H., and Stollenwerk, K.G., eds., Arsenic in ground water: Boston, Kluwer Academic Publishers, p. 127–164. [Also available at https://doi.org/10.1007/0-306-47956-7_5.]

Hickmott, D.D ., 1993, PIXE microanalysis of Fe-sulfides: Comparison of eastern and western coals: in Michaelian, K.H., ed., Proceedings of the International Conference on Coal Science, Banff, Alberta, Canada, September 1993, p. 648-651. [also available at https://www.osti.gov/biblio/10182263-seventh-international-conference-coal-science- proceedings.]

Hower, J.C., Campbell, J.L., Teesdale, W.J., Nejedly, Z., and Robertson, J.D., 2008, Scanning proton microprobe analysis of mercury and other trace elements in Fe-sulfides from a Kentucky coal: International Journal of Coal Geology, v. 75, no. 2, p. 88–92. [Also available at https://doi.org/10.1016/j.coal.2008.03.001.]

Kolker, A., Senior, C.L., and Quick, J.C., 2006b, Mercury in coal and the impact of coal quality on mercury emissions from combustion systems: Applied Geochemistry, v. 21, no. 11, p. 1821–1836. [Also available at https://doi.org/10.1016/j.apgeochem.2006.08.001.]

Kolker, A., Panov, B.S., Panov, Y.B., Landa, E.R., Conko, K.M., Korchemagin, V.A., Shendrik, T., and McCord, J.D., 2009, Mercury and trace element contents of Donbas coals and associated mine water in the vicinity of Donetsk, Ukraine: International Journal of Coal Geology, v. 79, no. 3, p. 83–91. [Also available at https://doi.org/10.1016/j.coal.2009.06.003.]

Kolker, A., 2012, Minor element distribution in iron disulfides in coal—A geochemical review: International Journal of Coal Geology, v. 94, p. 32–43. [Also available at https://doi.org/10.1016/j.coal.2011.10.011.]

2.2-12 Session 2 Topic 3 INTRODUCTION TO MERCURY IN COAL

2.3-1 Mercury in Coal Mercurio en carbones • Mercury in Fe-disufides and organics are the most common Hg forms in bituminous coals; organic association is more common in low rank coals. • There are few direct determinations of Hg in pyrite on a grain scale, primarily by laser-ablation ICP-MS. • Presence of Hg in Fe-disulfides is indicated by selective leaching studies and correlation of Hg with pyrite proxies such as Fe content or pyritic sulfur. • Differences in trace element content of different pyrite forms, as seen for As, are likely for Hg.

2.3-2 U.S Coal Databases: Mercury Results Mercurio en bases de datos de EE.UU.

From: Kolker and others, 2012 2.3-3 Mercury in World Export Coals Mercurio en carbones de exportación • Meij and te Winkel (2009) Compared Hg Mercury and As in coals 27 imported to the Netherlands. 13 • World averages for bituminous coals1:

Hg = 0.10 ± 0.01 ppm Arsenic As = 9.0 ± 0.7 ppm 13 • Colombian coal is well below average for Hg 27 and As, similar to Australian export coal. 1Ketris and Yudovich, 2009, Int. J. Coal Geol. Source: Meij and te Winkel, 2009, Int. J. Coal Geol.

2.3-4 Mercury in Iron Disulfides Mercurio en disulfuros de hierro

• Detection limit generally below electron microprobe detection on individual grains and XAFS on whole coal. • Limited microanalysis determinations, for example, by laser-ablation ICP-MS. • Presence of Hg indicated by selective leaching studies and by correlation of bulk mercury with proxies such as iron or pyritic sulfur. • Imaging showing generational changes in composition, such as that seen for arsenic and selenium, is generally not available.

2.3-5 Hg-rich coals in Ukraine vs. U.S. Illinois Basin coals Carbones con alto contenido de Hg en Ucrania y EE.UU. • Whole-coal samples have similar pyritic sulfur but much different Hg contents. • Impurities in pyrite differ: Pyrite-rich coals ≠ Hg-rich. • Coals formerly produced at Nikitovka Hg-mines have extreme Hg contents due to presence of cinnabar (HgS).

Kolker and others, 2009 – Ukraine and Bragg and others, 1997, COALQUAL - Herrin #6 and Springfield #5 Illinois Basin coals.

2.3-6 Summary – Topic 3: Introduction to Hg in Coal Resumen – Tema 3: Fundamentos de Hg en carbones

• Pyrite is most common mercury mode of occurrence in bituminous coals. Organic-hosted mercury is more likely in low rank coals. • Mercury content of pyrite varies. Can have high pyrite coals with only moderate mercury contents (e.g., U.S. Illinois Basin) and high mercury coals with only moderate pyrite contents (e.g., Donets Basin, Ukraine). • Mean mercury content of U.S. coals used for power generation (0.11 to 0.12 ppm) is close to the world average for Hg (0.10 ± 0.01 ppm). • Hg and As contents of exported Colombian coals are below world averages for both elements.

2.3-7 References – Topic 3: Intro. to Hg in Coal Referencias – Tema 3: Hg en carbones: fundamentos

Bragg, L.J., Oman, J.K., Tewalt, S.J., Oman, C.J., Rega, N.H., Washington, P.M., and Finkelman, R.B., 1997, U. S. Geological Survey coal quality (COALQUAL) database; ver. 2.0: U.S. Geological Survey Open-File Report 97–134, CD-ROM. [Also available at https://pubs.er.usgs.gov/publication/ofr97134.]

Ketris, M.P., and Yudovich, Ya.E., 2009, Estimations of clarkes for carbonaceous biolithes—World averages for trace element contents in black shales and coals: International Journal of Coal Geology, v. 78, no. 2, p. 135–148. [Also available at https://doi.org/10.1016/j.coal.2009.01.002.]

Meij, R., and te Winkel, B.H., 2009, Trace elements in world steam coal and their behavior in Dutch coal-fired power stations—A review: International Journal of Coal Geology, v. 77, nos. 3–4, p. 289–293. , [Also available at https://doi.org/10.1016/j.coal.2008.07.015.]

2.3-8 Mercury and Halogens in Coal Improving Mercury Capture Measuring Ambient Mercury and Fine Particulate Matter SESSION 3 Session 3 Topic 1 MERCURY AND HALOGENS IN COAL

3.1-1 Mercury in Coal - Session 2 Review Mercurio en carbones: revisión de la Sesión 2 • Mercury in Fe-disufides and organics are the most common Hg forms; organic association is more common in low rank coals. • There are few direct determinations of Hg in pyrite on a grain scale, primarily by laser-ablation ICP-MS. • Presence of Hg in Fe-disulfides is indicated by selective leaching studies and correlation of Hg with pyrite proxies such as Fe content or pyritic sulfur. • Differences in trace element content of different pyrite forms, as seen for As, are likely for Hg.

3.1-2 Halogens in Coal – Cl, F, Br, I Halógenos en carbones: Cl, F, Br, I

Good Bad • Halogens in sufficient • Too high concentrations of amounts promote capture alkalis and halogens in coal of mercury from power can cause boiler fouling, station flue gas by forming boiler tube deposits, and mercury-halogen complexes. corrosion of boiler components. • These complexes are easier to capture in power station air pollution control devices than elemental mercury present in the boiler.

3.1-3 Mercury and Halogens in Coal Mercurio y halógenos en carbones

• U.S. fish consumption advisories have driven efforts by the EPA to limit emissions of mercury and other toxic substances from coal-fired utility power stations. • USGS studies show the impact of coal quality on mercury emissions from coal combustion. • Halogens in coal (e.g., Cl, F, Br) help reduce the fraction of Hg emitted by promoting its capture. • But halogen emissions are also regulated as acid gasses under EPA MATS.

Kolker and others, 2012, USGS Fact Sheet 2012-3122 https://pubs.usgs.gov/fs/2012/3122/ 3.1-4 Halogens in U.S. Coals Halógenos en carbones de EE.UU.

• Bromine is 1-4% of Cl content on a weight basis. • Iodine contents are typically ≤ Br. • Fluorine is ≤ Cl.

U.S. county-average Cl and Br contents (USGS data). Kolker and others, 2012, modified from Vosteen and others, 2010.

3.1-5 a. Chlorine in Coal by Rank and Origin (162 coal-producing counties) Rank Dependence of Halogens Halógenos y calidad de carbones

Results show U.S. county-average Cl and

Br contents with ASTM b. Bromine in Coal by Rank and Origin (115 coal-producing counties) coal rank and origin. Cl data from 1999 EPA ICR; Br results from USGS COALQUAL.

Source: Kolker and Quick, 2015

3.1-6 Mode of Occurrence of Halogens in Coal Halógenos y su forma de ocurrencia en carbones

• Cl and Br K-edge XANES (X-Ray Absorption Near-Edge Structure) spectra show an association with coal macerals but not bound as organo- halogen compounds. • Cl and Br are primarily associated with coal moisture and are loosely bound to maceral surfaces or retained in pore spaces. Source: Huggins and Huffman, 1995, Fuel

3.1-7 Geologic Factors Influencing Coal Halogen Contents Dependencia entre factores geológicos y halógenos • Rank- Halogen contents increase with rank for low-rank and bituminous coals. • Depth- Halogen contents increase with depth or paleo (stratigraphic) depth. • Groundwater chemistry- Deep basin fluids are more saline and have higher halogen contents. • Geologic structures- Proximity to structures such as faults that have acted as conduits for saline or hydrothermal fluids.

3.1-8 Chlorine in U.S. Coal Cloro en carbones de EE.UU.

Powder River Basin

Appalachian Northern Basin

Illinois Basin Central Example 1 lbs Chlorine per Billion Btu Southern 3 - 25 25 - 50 50 - 75 75 - 100 100 - 200 200 - 326 U.S. County Averages 1999 EPA ICR Data, Source: Quick and others, 2005 U.S. EPA, 2003 3.1-9 Example 1: U.S. Illinois Basin Ejemplo 1: La cuenca de Illinois, EE.UU.

Chicago • 1964 study in Illinois motivated by fouling and corrosion of boilers by coals with high alkali chloride contents. • Recognized that the highest Cl Shallow Deep contents were found in the deepest coals and that Cl in coal was correlated with Cl Source: Gluskoter and Rees, 1964 in groundwater.

3.1-10 Chlorine in U.S. Coal Cloro en carbones de EE.UU.

Powder River Basin

Appalachian Northern Basin

Illinois Basin Central Example 2

lbs Chlorine Southern per Billion Btu 3 - 25 25 - 50 50 - 75 75 - 100 100 - 200 U.S. County Averages 200 - 326 1999 EPA ICR Data, Source: Quick and others, 2005 U.S. EPA, 2003 3.1-11 Example 2: Chlorine Variation with Depth Ejemplo 2: Cloro versus profundidad Age/depth Age Formation Number of Mean Cl Samples (ppm) Lower Permian (?) Dunkard Group 44 162 Upper Pennsylvanian Monongahela Formation 73 477

Upper Pennsylvanian Conemaugh Formation 41 828

Middle Pennsylvanian Allegheny Formation 709 1,097

Middle Pennsylvanian Kanawha Formation 36 1,408

Lower Pennsylvanian New River Formation 56 1,503

Central Appalachian Basin, USA Source: Bragg and others, 1991 3.1-12 Mercury in South African Feed Coals Mercurio en carbones de Sudáfrica • 2014 USGS study in cooperation with Eskom and United Nations Environment Programme (UNEP). • Eskom provided USGS a suite of 42 feed coal samples including all 13 operating coal-fired utility power stations in South Africa. • Eskom also provided 8 density separates of Highveld #4 coal. • Study helps show mercury content of coal used for power generation in South Africa and the potential for mercury reduction. Source: Kolker and others, 2014, USGS Open-File 2014-1153 3.1-13 https://pubs.usgs.gov/of/2014/1153/ Mercury Distribution by Power Station Fluctuaciones en el contenido de mercurio • Hg contents vary by 600 power station due to Eskom Feed Coals 500 n = 42 differences in coal supply. 400 • Mean Hg content of 42 300 South African feed Matimba S.A. Feed Coals

Hg (ppb) Hg coals is about 4x that of 200 typical export coals. U.S. Feed Coals 100 S.A. Export Coals • Matimba station # 11

0 burns washed 1 2 3 4 5 6 7 8 9 10 11 12 13 Waterburg coals; Power Station Number others use partly washed or unwashed Source: Kolker and others 2014, USGS Open-File 2014-1153 https://pubs.usgs.gov/of/2014/1153/ coals.

3.1-14 Impact of Coal Preparation on Mercury Impacto de la preparación sobre el mercurio

• Reduces mineral matter and sulfur associated with minerals such as pyrite. • Increases energy content by concentrating organic fractions. • Mercury reduction varies typically 0-35% on a concentration basis, higher on equivalent energy basis. • Potential for mercury reduction depends on the fraction of mercury present as pyrite vs. organic association and efficiency of washing process.

3.1-15 South African Highveld #4 Coal Carbón sudafricano Highveld #4 • Highveld #4 coal is being tested to produce low ash, washed export coal. • Remaining fractions are used for power generation, unless export yield is low, then run-of-mine or de- stoned (discard fraction removed) coal is burned. • Density separates simulate the behavior of Highveld #4 coal during coal washing. • The separation process is effective in concentrating pyrite in the high-ash, higher density fractions.

Source: Kolker and others, 2017b 3.1-16 Density Separates Separación de acuerdo a la densidad

South Africa Highveld #4 Coal • More pyrite is present F = Float S = Sink in separates taken at 1.4 to 2.0 is density of liquids higher densities. • Raw coal ~35% ash, 0.29 ppm Hg. • Export product 11.5% ash, 0.06 ppm Hg. • Results show pyritic mercury association confirmed by laser ablation ICP-MS.

Source: Kolker and others, 2017b, Int. J. Coal Geology 3.1-17 Pyrite by Laser Ablation ICP-MS Espectrometría de piritas

South Africa Highveld #4 Coal 20 microns 15 25 microns 64.5 ppm • Results show As, 10

Hg are (ppm) Hg enriched in 5 pyrite. 0 • Element 0 20 40 60 80 100 120 140 160 contents 400 20 Microns 25 Microns are highly 691 ppm 983 ppm variable on 300 a grain 200 scale. As(ppm) 100

Pyrite 0 0 20 40 60 80 100 120 140 160 Backscattered Electron Image Analysis Number

Source: Kolker and others, 2017b, Int. Journal Coal Geol. 3.1-18 Coal Products Predicted from Density Separates Productos de separaciones por densidad

Product Samples Ash Hg As Se Approx. averaged (wt. %) (ppm) (ppm) (ppm) cut point Export 1.4F 11.5 0.06 0.5 0.5 Cut at 1.4

De-stoned 1.4F-1.9F 26.6 0.24 1.4 1.0 Cut at 1.9

Middling 1.5F-1.9F 29.7 0.27 1.5 1.1 1.4 to 1.9

Run-of-mine 14F-2.0S 35.2 0.29 2.0 1.1 No washing

Middling + 1.5F-2.0S 38.6 0.32 2.2 1.2 > 1.4 Used in South Africa South in Used generation for power discard

Stone (discard) 2.0F, 2.0S 60.9 0.46 3.8 1.4 > 2.0

Source: Kolker and others, 2017b, Int. J. Coal Geol.

3.1-19 Summary − Topic 1: Mercury and Halogens in Coal Resumen − Tema 1: Mercurio y halógenos

• Coal preparation is an effective means of reducing mercury input to the boiler where mercury-specific controls are lacking. • Halogens in coal (e.g., Cl, F, Br) help reduce the fraction of Hg emitted by promoting its oxidation and capture. • Halogen content is a function of coal rank, depth of burial, and (or) proximity to geologic structures, allowing saline or hydrothermal fluids to interact with coal. • Br/Cl ratio of many commercial coals ranges from 0.01 to 0.04, regardless of rank. On a mass basis, Br is more effective than Cl in promoting Hg oxidation and capture.

3.1-20 References − Topic 1: Mercury and Halogens in Coal Referencias − Tema 1: Mercurio y halógenos Bragg, L.J., Finkelman, R.B., and Tewalt, S.J., 1991, Distribution of chlorine in United States coal, in, Stringer, J., and Banerjee, D.D., eds., Chlorine in coal— Proceedings of an international conference: Amsterdam, Elsevier, Coal science and technology series v. 17, p. 3–10.

Gluskoter, H.J., and Rees, O.W., 1964, Chlorine in Illinois coal: Illinois State Geological Survey Circular 372, 23 p. [Also available at https://www.ideals.illinois.edu/bitstream/handle/2142/35156/chlorineinillino372glus.pdf?sequence=2.]

Huggins, F.E., and Huffman, G.P., 1995, Chlorine in coal—An XAFS spectroscopic investigation: Fuel, v. 74, no. 4, p. 556–569. [Also available at https://doi.org/10.1016/0016-2361(95)98359-m.]

Kolker, A., Senior, C.L., and van Alphen, C., 2014, Collaborative studies for mercury characterization in coal and coal combustion products, Republic of South Africa (ver. 2.0, May 2016): U.S. Geological Survey Open-File Report 2014–1153, 48 p. [Also available at https://pubs.usgs.gov/of/2014/1153/.]

Kolker, dA., Q an uick, J.C., 2015, Mercury and halogens in coal, in Granite, E.J., Pennline, H.W., and Senior, C., eds., Mercury control for coal-derived gas streams: Weinheim, Germany, Wiley-VCH, p. 13–44. [Also available at https://doi.org/10.1002/9783527658787.ch2.]

Kolker, A., Senior, C., van Alphen, C., Koenig, A., and Geboy, N., 2017b, Mercury and trace element distribution in density separates of a South African Highveld (#4) coal—Implications for mercury reduction and preparation of export coal: International Journal of Coal Geology, v. 170, p. 7–13, accessed September 26, 2016, at https://doi.org/10.1016/j.coal.2016.02.002.

Quick, J.C., Tabet, D.E., Wakefield, S., and Bon, R.L., 2005, Optimizing technology to reduce mercury and acid gas emissions from electric power plants— Final report, August 1, 2003 to October 31, 2005: Salt Lake City, Utah, The Utah Geological Survey, prepared for the U.S. Department of Energy, Contract DE-FG26-03NT41901, 43 p., [Also available at https://doi.org/10.2172/876545.]

U.S. Environmental Protection Agency [EPA], 2003, Coal analysis results in Electric utility steam generating units section 112 rule making: EAP web page, accessed November 9, 2017, at https://www.epa.gov/ttn/atw/combust/utiltox/utoxpg.html.

Vosteen, B.W., Winkler, H., and Berry, M.S., 2010, Native halogens in coals from USA, China and elsewhere—Low chlorine coals need bromide addition for enhanced mercury capture, in Proceedings, 2010 Power Plant Air Pollutant Control Mega Symposium: Power Plant Air Pollutant Control Mega Symposium 2010, 8th, Baltimore, Maryland, USA, 30 August–2 September 2010, Pittsburgh, Pa., Air & Waste Management Association, v. 2, session 4C, Paper no. 103, p. 1174–1242.

3.1-21 Session 3 Topic 2 IMPROVING MERCURY CAPTURE

3.2-1 Factors that Influence Mercury Capture Factores que contribuyen a la captura de mercurio

• COAL QUALITY • Coal rank • Coal mercury content • Coal halogen content • Coal sulfur content • PLANT OPERATIONS • Type and positioning of air pollution control devices. • Unburned carbon in particulate fraction.

• NOx control (post-combustion, SCR). • Mercury-specific controls.

Sources: UNEP, 2011; Senior, 2015

3.2-2 Impact of Chlorine on Mercury Capture1 Influencia del cloro en captura de mercurio

• Figure shows predicted impact of Cl on Hg capture for various controls. • Results are Optimal Range calculated for U.S. county averages from 1999 EPA ICR data and published best-fit equations for each control technology.

Sources: Quick and others, 2005; Kolker and others, 2006b 1With conventional air pollution control devices (APCDs) 3.2-3 Role of Halogens in Mercury Capture Papel de los halógenos en la captura de mercurio Cartoon showing gas phase and gas-particle reactions in the boiler. • Halogens promote oxidation of elemental mercury to form mercury-halogen complexes or mercury bound to particles. • These forms are easier to capture than gaseous elemental mercury. Source: Kolker and others, 2012, USGS Fact Sheet 2012-3122 https://pubs.usgs.gov/fs/2012/3122/

3.2-4 Improving Mercury Capture1 Mejoras en la captura de mercurio

• Coal selection and coal washing: Can reduce contents of elements bound in pyrite such as Hg. Ash, Hg, and S contents of Colombian coals are generally low and coals are not washed. • Optimize operating conditions: Lowering air preheater exit temperature can increase the amount of unburned carbon, improving Hg capture. This change may effect boiler Effect of ash unburned carbon efficiency and may impact (LOI) on % Hg removal across marketing of ash for other uses. ESP air pollution controls.

1 Source: Senior and Johnson, 2005 With Conventional Emission Controls Energy and Fuels

3.2-5 Improving Mercury Capture1 Mejoras en la captura de mercurio • Addition of Fabric Filters (FFs): FFs are generally more efficient than electrostatic precipitators (ESPs) in removing mercury. FFs can be added within an existing ESP unit or by bypassing the ESP with a separate FF unit. • Use of sorbents: Addition of sorbents can improve mercury capture. For low Cl coals, such as Colombian export coals, addition of halogens (Cl, Br) to the fuel or the boiler will improve Hg capture. Injection of activated carbon upstream from particulate controls is a common approach to increasing Hg capture. Less Effect of coal Cl on % elemental Hg sorbent is required if the unit has an FF at inlet to particulate controls instead of an ESP. Source: Senior and Johnson, 2005 Energy and Fuels

1With Conventional Emission Controls 3.2-6 Improving Mercury Capture1 Mejoras en la captura de mercurio

• Addition of Flue-Gas Desulfurization (FGD): FGD scrubbers remove gaseous oxidized Hg with an efficiency of 90% or higher. The cost of adding FGD is probably too high to be justified on the grounds of Hg removal alone. However, if future regulations require reductions in the

emissions of SO2 and FGDs are installed, there will be additional Wet FGD System reduction in Hg emissions. Source: Babcock and Wilcox, 2014 1With Conventional Emission Controls http://www.babcock.com/

3.2-7 Kendal and Duvha Power Stations, South Africa Centrales termoeléctricas de Kandal y Duvha, Sudáfrica

• 2010 UNEP, Eskom, EPA, South Case Study Africa collaborative study to measure mercury stack emissions for each station using EPA methods1. • Samples of feed coal and fly ash were also collected by EPA from each boiler unit. • Coal and fly ash samples were obtained by USGS and studied as part of 2012 UNEP, Eskom, USGS 1Scott, 2011, UNEP Project Report, collaborative study of all 13 South http://www.unep.org/ African coal-burning power 2Kolker and others, 2014, stations2. USGS Open-File 2014-1153 https://pubs.usgs.gov/of/2014/1153/

3.2-8 Kendal and Duvha Power Stations, South Africa Centrales termoeléctricas de Kendal y Duvha, Sudáfrica

Mercury Mass Balance, Kendal and Duvha Power Station, South Africa Power Unit Air Pollution Avg. Hg. In Avg. Hg. In Fly Emissions Avg. % Emissions Station Number Controls Feed Coal ash (ppm) Hg, μg/m3 @ 3% Percent oxidized (ppm) 2+ O2 Hg (Hg ) Duvha 1 Fabric Filter 0.14 0.18 13.81 89% 2 Fabric Filter 0.18 0.63 4.65 73% 3 Fabric Filter 0.16 0.68 4.09 88% 4 ESP 0.28 0.13 35.49 56% 5 ESP 0.21 0.21 29.01 54% 6 ESP 0.26 0.19 40.37 55% Kendal 1 ESP 0.18 0.09 39.20 70% 2 ESP 0.22 0.09 43.45 54% 3 ESP 0.20 0.06 49.13 52% 4 ESP 0.18 0.15 46.03 52% 5 ESP 0.36 0.08 39.47 48% 6 ESP 0.35 0.03 46.34 54%

Source: Kolker and others, 2014; Scott, 2011

3.2-9 Kendal and Duvha Power Stations, South Africa Centrales termoeléctricas de Kendal y Duvha, Sudáfrica

Hg in Feed Coal and Fly Ash Hg Capture Efficiency by Unit

400 Mill Feed Coals Kendal Duvha 300

200 Hg (ppb) Hg

100

0 1 2 3 4 5 6

800 Fly Ashes Kendal Duvha 600

400 Hg (ppb) Hg

200

0 1 2 3 4 5 6 Boiler Unit

Source: Kolker and others, 2014 3.2-10 Kendal and Duvha Power Stations, South Africa Centrales termoeléctricas de Kendal y Duvha, Sudáfrica

• Capture efficiency for Hg varies by utility boiler according to setup and operating conditions. • Duvha units 1-3 equipped with fabric filters have a much higher capture efficiency for Hg than units with ESPs, as shown by: 1) Total Hg in flue gas 2) Percent Hg2+ in flue gas 3) Hg captured in fly ash. • Hg capture efficiency in Kendal station and in Duvha units 4-6 equipped with ESPs is typically < 20%.

Source: Kolker and others, 2014 3.2-11 Improving Mercury Capture Mejoras en la captura de mercurio • UNEP 2010 Guidance Document for reducing mercury emissions from coal-burning powerplants. • Recommendations and best practices for improving mercury capture generally without mercury-specific controls. • Approaches range from inexpensive to more cost intensive. Source: UNEP, 2011, http://www.unep.org/

3.2-12 Summary- Topic 2: Improving Hg Capture Resumen−Tema 2: Captura de mercurio • In the boiler, Hg is present as elemental Hg that is difficult to capture using conventional air pollution controls (e.g., ESPs). • Halogens in coal or in added sorbents convert some of the Hg to oxidized species that can be captured from flue gas by air pollution controls. • Unburned carbon in ash and (or) activated carbon-based sorbents also effect Hg capture. • Fabric filters are more efficient than ESPs in capturing mercury. • FGD, if added to reduce sulfur emissions, will also improve Hg capture. 3.2-13 References − Topic 2: Improving Mercury Capture Referencias − Tema 2: Mejoras en captura de mercurio Babcock and Wilcox, 2014 , Wet flue gas desulfurization (FGD) systems, Babcock and Wilcox website, accessed November 15, 2016, at http://www.babcock.com/products/- /media/886ef4754dd8400b8a22876ad5292eda.ashx.

Quick, J.C., Tabet, D.E., Wakefield, S., and Bon, R.L., 2005, Optimizing technology to reduce mercury and acid gas emissions from electric power plants—Final report, August 1, 2003 to October 31, 2005: Salt Lake City, Utah, The Utah Geological Survey, prepared for the U.S. Department of Energy, Contract DE-FG26-03NT41901, 43 p., [Also available at https://doi.org/10.2172/876545.]

Scott, G., 2011, Reducing mercury emissions from coal combustion in the energy sector in South Africa—Final project report: Geneva, Switzerland, United Nations Environmental Programme and South African Department of Environmental Affairs, 18 p. [Also available at https://www.unenvironment.org/resources/report/reducing- mercury-emission-coal-combustion-energy-sector-south-africa.]

Senior, C., 2015, Mercury behavior in coal combustion systems in, Granite, E.J., Pennline, H.W., and Senior, C., eds., Mercury emissions control—For coal-derived gas streams: Weinheim, Germany, Wiley-VCH, p. 111–131.

Senior, C.L., and Johnson, S.A., 2005, Impact of carbon-in-ash on mercury removal across particulate control devices in coal-fired power plants: Energy and Fuels, v. 19, no. 3, p. 859–863. [Also available at https://doi.org/10.1021/ef049861+.]

United Nations Environment Programme [UNEP], 2011, Process optimization guidance for reducing mercury emissions from coal combustion in power plants: Geneva, Switzerland, United Nations Environment Programme, Division of Technology, Industry and Economics, Chemicals Branch, 94 p. [Also available at http://www.unep.org/chemicalsandwaste/Mercury/GlobalMercuryPartnership/Coalcombustion/ProcessOptimizationGuidanceDocument/tabid/4873/Default.aspx.]

3.2-14 Session 3 Topic 3 MEASURING AMBIENT MERCURY AND FINE PARTICULATE MATTER

3.3-1 Speciation of Ambient Mercury Especiación del mercurio en la atmósfera

• Coal-fired power stations are among the largest point-source emitters of ambient atmospheric Hg. • Operationally defined species: Elemental Mercury (Hgo) Reactive Gaseous Mercury (RGM) Particulate Mercury (Hgp) • RGM (also known as gaseous oxidized Hg) includes all charged Hg species (e.g., HgCl2(g)); HgP includes all Hg bound to particulates. • Hgo is the dominant Hg form in the atmosphere and has a long residence time, resulting in global Hg transport. • RGM has a shorter residence time and is deposited locally to regionally.

• Atmospheric residence time of Hgp varies depending on size, composition, and solubility of particles.

3.3-2 USGS Mobile Mercury Lab Laboratorio para análisis de mercurio del USGS Mercury Analyzer • Near continuous Hgo, RGM, HgPM2.5 measurements in the field with trapping of Hg species and analysis by cold vapor atomic fluorescence. • Mobile lab can also measure fine particulate mass (PM2.5), and gaseous SO2, NOx, and O3. • Separate PM collectors are needed to collect PM2.5 for analysis, including trace USGS Mobile Mercury Laboratory elements. Source: Kolker and others, 2007 USGS Fact Sheet 2007-3071 3.3-3 Ambient Mercury and Fine Particulate Matter Mercurio y partículas atmosféricas en suspensión

Particulate samplers on rooftop. Particulates are collected on filters Instrument controls in Mobile Lab. and extracted for analysis.

3.3-4 Ambient Mercury, Woods Hole, Massachusetts Mercurio en la atmósfera de Woods Hole, MA

Study Area: Woods Hole, Massachusetts, USA

Source: Kolker and others, 2013, Atmospheric Environment

3.3-5 Hg Species and Other Gases, Woods Hole Mercurio y otros gases en la atmósfera de Woods Hole

in ppbV o O3 [Good = 0 to 50] Hg [Unhealthy = 151 to 200]

NOx HgPM2.5

RGM SO2

Date Source: Kolker and others, 2013 3.3-6 Distinguishing Sources of Ambient Mercury Fuentes de contaminación atmosférica con mercurio

• Ambient mercury species defined as elemental mercury (Hgo), reactive gaseous mercury (RGM), and particulate mercury (Hgp). • Monitoring of mercury species, fine particulate matter, and ancillary gasses can help distinguish mercury sources.

• Correlation of RGM with SO2 and (or) NOx peaks indicates plumes from coal combustion such as in powerplants.

• Lack of corresponding SO2 and (or) NOx peaks indicates non-coal sources, such as chlor-alkali plants. • Use of elemental mercury in small-scale gold mining generates no RGM, Hgp, or corresponding ancillary gases. Sources: Edgerton and others, 2006; Kolker and others, 2008, 2010 3.3-7 Trace Elements in PM2.5 Elementos traza en PM-2.5

Source Typical Elements • Crustal (natural source) • Al, Ti, La, Ce, REE, Y, Fe, Zr • Marine (natural source) • Na, Mg, Ca, Sr, Cl

• Coal Combustion • Ni, V, Mo, Sb, As, Hg, Cr, Se (anthropogenic source)

• Metal Smelting • Pb, Zn, Cu, Cd (anthropogenic source)

Anthropogenic source is indicated where ratio Sources: Duce and others, 1975; anthropogenic element/crustal element Pacyna and Pacyna, 2001 ≥ 10 times crustal proportion for these elements. Song and others, 2001

3.3-8 Trace Elements in PM2.5 Trazas y PM-2.5 Crustal Al Ce Fe Ti Y Cs La Mn Rb Sc U Factorization analysis indicates four probable Marine Mg Na source categories at Woods Sr Ca K Hole site.

(Percent of PM2.5 mass): Smelter(?) 1) Crustal (18.4%) Pb Cd Zn 2) Marine (23.1%) 3) Metal smelter? (13.0%) 4) Energy generation (45.5%) Energy Mo P Sb V As Ba Cu Ni Source: Kolker and others, 2013, Atmospheric Environment

3.3-9 Summary − Topic 3: Ambient Mercury and Fine Particulates Resumen − Tema 3: Mercurio y partículas en suspensión

• Operationally defined species: Elemental Mercury (Hgo); Reactive Gaseous Mercury (RGM); Particulate Mercury (Hgp)

• RGM includes all charged Hg species; HgP includes all Hg bound to particulates. • RGM has local to regional sources such as power stations and chlor- alkali plants. RGM from combustion sources is present in plumes with other gaseous species such as SO2 and NOx. • Hgo has long residence times leading to global transport. As a result, there are fish consumption advisories for Hg in remote areas of the United States where there are no local Hg sources.

• EPA regulations limit U.S. PM2.5 concentrations based on average mass concentrations. USGS and others have used trace elements in PM2.5 to distinguish source input. Coal combustion sources are indicated by Ni, V, Mo, Sb, As, Cr, etc., in addition to Hg.

3.3-10 References − Topic 3: Ambient Mercury and Fine Particulates Referencias − Tema 3: Mercurio y partículas microscópicas

Duce, R.A., Hoffman, G.L., and Zoller, W.H., 1975, Atmospheric trace metals at remote northern and southern hemisphere sites—Pollution or natural?: Science, v. 187, no. 4171, p. 59–61. [Also available at https://doi.org/10.1126/science.187.4171.59.]

Edgerton, E.S., Hartsell, B.E., and Jansen, J.J., 2006, Mercury speciation in coal-fired power plant plumes observed at three surface sites in the southeastern U.S.: Environmental Science and Technology, v. 40, no. 15, p. 4563–4570. [Also available at https://doi.org/10.1021/es0515607.]

Kolker, A., Engle, M.A., Krabbenhoft, D.P., and Olson, M.L., 2007, Investigating atmospheric mercury with the U.S. Geological Survey mobile mercury laboratory: U.S. Geological Survey Fact Sheet 2007–3071, 4 p. [Also available at https://pubs.er.usgs.gov/publication/fs20073071.]

Kolker, A., Engle, M.A., Orem, W.H., Bunnell, J.E., Lerch, H.E., Krabbenhoft, D.P., Olson, M.L., DeWild, J.F., and McCord, J.D., 2008, Mercury, trace elements, and organic constituents in atmospheric fine particulate matter, Shenandoah National Park, Virginia, USA: A combined approach to sampling and analysis: Geostandards and Geoanalytical Research, v. 32, no. 3, p. 279–293. [Also available at https://doi.org/10.1111/j.1751-908x.2008.00913.x.]

Kolker, A., Olson, M.L., Krabbenhoft, D.P., Tate, M.T., and Engle, M.A., 2010, Patterns of mercury dispersion from local and regional emission sources, rural Central Wisconsin, USA: Atmospheric Chemistry and Physics, v. 10, no. 1, p. 4467–4476. [Also available at https://doi.org/10.5194/acpd-10-1823-2010.]

Kolker, A., Engle, M.A., Peucker-Ehrenbrink, B., Geboy, N.J., Krabbenhoft, D.P., Bothner, M.H., and Tate, M.T., 2013, Atmospheric mercury and fine particulate matter in coastal New England—Implications for mercury and trace element sources in the northeastern United States: Atmospheric Environment, v. 79, p. 760–768. [Also available at https://doi.org/10.1016/j.atmosenv.2013.07.031.]

Pacyna, J.M., and Pacyna, E.G., 2001, An assessment of global and regional emissions of trace metals to the atmosphere from anthropogenic sources worldwide: Environmental Reviews, v. 9, no. 4, p. 269–298. [Also available at https://doi.org/10.1139/er-9-4-269.

Song, X.-H., Polissar, A.V., and Hopke, P.K., 2001, Sources of fine particle composition in the northeastern US: Atmospheric Environment, v. 35, no. 31, p. 5277–5286 [Also available at https://doi.org/10.1016/s1352-2310(01)00338-7.]

3.3-11 Introduction to Coal Ash Trace Elements in Coal Ash Beneficial Uses of Coal Ash Coal Ash Environmental Issues SESSION 4 Session 4 Topic 1 INTRODUCTION TO COAL ASH

4.1-1 Coal Combustion Products (CCPs) Productos de la combustión del carbón

• Coal combustion products are produced in large quantities during coal combustion for power generation. • Coal combustion products consist primarily of fly ash, bottom ash, and, in plants with flue-gas desulfurization (FGD), sludge from FGD scrubber. • In 2016, 52% of U.S. coal fly ash was beneficially used, primarily in construction. • Classification of coal ash for construction purposes is based on its major element composition, expressed as the sum of SiO2 Fly ash backscattered electron + Al2O3, + Fe2O3 vs. other major image, 1000x, USGS Reston labs. constituents. • These characteristics are a function of the chemistry, rank, and mineralogy of the feed coal. Source: American Coal Ash Association, not dated https://www.acaa-usa.org/ 4.1-2 Coal Combustion Products (CCPs) Productos de la combustión del carbón

Diagram showing typical range of CCPs generated in a coal-fired powerplant equipped with an electrostatic precipitator (ESP) and flue-gas desulfurization scrubber (FGD).

FGD

Bottom Fly Ash Source: Deonarine and others, 2015 Ash USGS Fact Sheet 2015-3037 4.1-3 https://pubs.usgs.gov/fs/2015/3037/ ASTM C618 Fly Ash Classification Clasificación de cenizas de acuerdo a ASTM C618

• Class C – “cementitious” = more calcium rich.

SiO2 + Al2O3 + Fe2O3 ≥ 50% • Class F – “pozzolanic” = more aluminosilicate rich.

SiO2 + Al2O3 + Fe2O3 ≥ 70% • Each class has different properties for use in concrete.

Source: ASTM International C618-17, 2017a http://www.astm.org.

4.1-4 In the Boiler En el horno • Peak temperatures in PC boilers generally ~1,700 °C. • Temperature in flue gas is reduced to ~200 °C within seconds. • Some boilers (e.g., fluidized bed) have lower operating temperatures.

Source: Senior, 2015, Chap. 7, in Mercury Control for Coal-derived Gas Streams 4.1-5 Mineral Transformations in Powerplants Transformación de minerales por combustión Coal Fly Ash

• Quartz (SiO2) • Quartz (beta form) • Clays • Aluminosilicates Mullite Al Si O Illite-smectite 6 2 13 • Aluminosilicate glass Kaolinite Al (Si O )(OH) 4 4 10 8 • Ca, Mg phases (Class C ash) • Carbonates Ca-aluminosilicates

Calcite (CaCO3) Anhydrite (CaSO4) Lime (CaO); Periclase (MgO) Siderite (FeCO3) • Fe oxides (pyrite breakdown) Ankerite Ca(Mg,Fe,Mn)(CO3)2 Hematite (Fe2O3) Pyrite (Marcasite; FeS2) • Magnetite (Fe3O4)

4.1-6 Examples of Fly Ash Constituents Ejemplos de partículas en suspensión

Glassy Cenosphere Mullite [reflected light] [SEM]

Partially Combusted Magnetite [reflected light] Coal [reflected light]

Source: James Hower, Univ. of Kentucky 4.1-7 Fly Ash Petrography Petrografía de partículas en suspensión Inorganic Organic

• Neoformed [formed in the • Neoformed [formed in the boiler] boiler] – isotropic coke – Glass, 70 to >90% of most FA – anisotropic coke – Mullite (Al6Si2O13) – Spinel (magnetite) • Coal (or fuel) derived • Coal derived – inertinite – Quartz – petroleum coke

4.1-8 Fly Ash Microanalysis Backscattered Electron Images (BSE) Microanálisis Fe- • Backscattered electron image (BSE) Oxide is a function of mean Glass atomic number. • BSE shows BSE BSE distribution of glassy areas and Fe-oxides in ash sample. Wavelength-dispersive Electron Microprobe Elemental Maps • Wavelength- dispersive electron microprobe map shows distribution of specific elements. • Maps shows that Ni is concentrated in Fe- oxide phases relative to glass. Ni Ni 4.1-9 Fly Ash Microanalysis Microanálisis de partículas en suspensión

BSE Fe Ca

Al Si

50 µm Backscattered electron imaging (BSE, above) and wavelength- dispersive elemental mapping (right) shows composition. Source: Kolker and others, 2017a 4.1-10 Summary − Topic 1: Introduction to Coal Ash Resumen − Tema 1: Fundamentos de cenizas de carbón • Coal ash consists of material formed during coal combustion and uncombusted material from coal remaining after coal combustion. • Ash constituents include glass, residual minerals such as quartz, new-formed minerals such as mullite, and unburned carbon. • Coal ash is classified by its major constituents. Bulk composition of fly ash from low-rank coals differs from that of bituminous coals. • ASTM classification of coal ash for construction purposes is based on its properties and the sum of SiO2 + Al2O3, + Fe2O3. These components are largely a function of the chemistry, rank, and mineralogy of the feed coal. • Coal quality parameters determine ash chemistry. Reactions during coal combustion involve high temperature breakdown of clays and carbonates, and oxidation of pyrite.

4.1-11 References – Topic 1: Introduction to Coal Ash Referencias – Tema 1: Fundamentos de cenizas

American Coal Ash Association, not dated, Coal combustion products production & use statistics—ACAA 2015 production and use charts: American Coal Ash Association website, accessed November 17, 2016, at https://www.acaa-usa.org/Portals/9/Files/PDFs/2015-Survey_Results_Charts.pdf.

Deonarine, A., Kolker, A., and Doughten, M.W., 2015, Trace elements in coal ash: U.S. Geological Survey Fact Sheet 2015–3037, 6 p. [Also available at https://pubs.usgs.gov/fs/2015/3037/.

Kolker, A., Scott, C., Hower, J.C., Vazquez, J.A., Lopano, C.L., and Dai, S., 2017a, Distribution of rare earth elements in coal combustion fly ash, determined by SHRIMP–RG ion microprobe: International Journal of Coal Geology, v. 184, p. 1–10, accessed October 30, 2017, at https://doi.org/10.1016/j.coal.2017.10.002.

Senior, C., 2015, Mercury behavior in coal combustion systems in, Granite, E.J., Pennline, H.W., and Senior, C., eds., Mercury emissions control—For coal- derived gas streams: Weinheim, Germany, Wiley-VCH, p. 111–131.

4.1-12 Session 4 Topic 2 TRACE ELEMENTS IN COAL ASH

4.2-1 Trace Elements in Coal Ash Elementos traza en cenizas de carbones

• At boiler temperatures, minerals in feed coal melt, react, or undergo phase transformations, with redistribution of major and trace elements. • Trace metal content of ash is controlled by minor constituents in minerals from the coal such as clays, the presence of trace phases, and boiler conditions. • Volatile elements such as mercury and selenium are partitioned into the gas phase during coal combustion and are emitted or condense on ash particles. • Refractory elements such as zirconium and the rare earths are retained in the ash. • Element concentrations in fly ash are higher than in feed coals due to mass reduction, capture, and retention of gas phase constituents.

4.2-2 Behavior of Elements During Coal Combustion Volatilidad de los elementos en la combustión

Very Volatile

Not Volatile

Source: Ratafia-Brown, 1994, Fuel Process. Technol. 4.2-3 From the Flue Gas Gases de combustión

• Capture of elements from the gas phase occurs as the flue gas cools, primarily by adhering of constituents onto ash particle surfaces. Hg and Se are the most volatile and the proportion these elements captured is lowest (or emitted is highest). • Highest trace metal concentrations occur in the finest size fractions of ash. These fractions have the greatest surface area with which to capture volatiles from the gas phase. • Most elements are associated with inorganic fly ash constituents, but as shown in the section on Hg capture, Hg has an affinity for residual unburned carbon.

4.2-4 Element Enrichment in Coal Ash Enriquecimiento de elementos en las cenizas

Fly Ash

Coal

Plot showing element enrichment in three U.S. coal fly ash samples, in relation to average element contents in U.S. coals (Bragg and others, 1997). Source: Deonarine and others, 2015 USGS Fact Sheet 2015-3037 https://pubs.usgs.gov/fs/2015/3037/

4.2-5 Variation in Fly Ash Chemistry Fluctuaciones químicas de las partículas • Concentrations of many volatile trace elements vary within the ash-collection system.

• Flue -gas temperature and ESP Inlet ESP Outlet particle size decrease away from the boiler, resulting in greater element capture. • Arsenic, lead and other elements tend to be more highly concentrated in back rows of electrostatic precipitators (ESP). Source: Keith Holbert Arizona State University

4.2-6 Fly Ash Chemistry – Arsenic Arsénico y partículas en suspensión • Example showing arsenic variation in a ESP Hoppers ESP hoppers in a (ppm) powerplant in Kentucky, USA. Front • Diagram shows arsenic enrichment in hoppers toward the rear of the ESP array. Rear • Powerplant is burning medium sulfur, high volatile A bituminous coal. Source: James Hower, University of Kentucky, unpublished data, 2004

4.2-7 Fly Ash Chemistry – Mercury Mercurio y partículas en suspensión

• Example showing (ppm) mercury variation in ESP hoppers in a powerplant in Kentucky, USA. • Diagram shows mercury enrichment in hoppers toward the rear of the ESP array. • Powerplant is burning a single-seam/single- mine coal burned at a 220-MW utility boiler.

Source: Mardon and Hower, 2004, Int. J. Coal Geology

4.2-8 Mercury Capture Captura de mercurio • On average, ~36% of mercury in feed coal is retained in coal ash in U.S. power stations. • In high-temperature regions of the boiler, only gaseous elemental mercury is present. • As the flue gas cools to ~150 to 250 oC, some elemental mercury is converted to oxidized gas-phase mercury and particulate mercury, which are much more readily captured in coal ash. • Mercury capture can be increased if halogens are present in the feed coal or if unburned carbon is present in coal ash. • Sorbents containing halogens or activated carbon can be added to increase Hg capture.

Source: Kilgroe and others, 2002, EPA-600/R-01-109 4.2-9 Summary – Topic 2: Trace Elements in Coal Ash Resumen − Tema 2: Elementos traza en cenizas • Elements such as arsenic, mercury, and selenium are partitioned into the gas phase, with capture occurring primarily by adhering onto ash particle surfaces as the flue gas cools or is emitted. • Highest trace metal concentrations occur in the finest size fractions of ash at the rear of ESP arrays. • Mercury and selenium are especially volatile, with the smallest fractions of the amount present in feed coal retained in the fly ash. • Refractory elements such as the rare earths do not enter the gas phase and are retained in the ash.

4.2-10 References – Topic 2: Trace Elements in Coal Ash Referencias – Tema 2: Elementos traza en cenizas

Deonarine, A., Kolker, A., and Doughten, M.W., 2015, Trace elements in coal ash: U.S. Geological Survey Fact Sheet 2015–3037, 6 p. [Also available at https://pubs.usgs.gov/fs/2015/3037/.

Kilgroe, J.D., Sedman, C.B., Srivastava, R.K., Ryan, J.V., Lee, C.W., and Thorneloe, S.A., 2002, Control of mercury emissions from coal-fired electric utility boilers—Interim report including errata dated 3–21–02: National Risk Management Laboratory and Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency EPA–600/R–01–109. [Also available at https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P10071NU.TXT.]

Mardon, S.M., and Hower, J.C., 2004, Impact of coal properties on coal combustion by-product quality—Examples from a Kentucky power plant: International Journal of Coal Geology, v. 59, nos. 3–4, p. 153–169. [Also available at https://doi.org/10.1016/j.coal.2004.01.004.]

Ratafia-Brown, J.A., 1994, Overview of trace element partitioning in flames and furnaces of utility coal-fired boilers: Fuel Processing Technology, v. 39, nos. 1–3, p. 139–157. [Also available at https://doi.org/10.1016/0378-3820(94)90177-5.]

4.2-11 Session 4 Topic 3 BENEFICIAL USES OF COAL ASH

4.3-1 Beneficial Uses of Coal Combustion Products Aprovechamiento de las cenizas de carbones

• A 2014 review by the EPA upheld existing classification of U.S coal ash as nonhazardous waste. • Nonhazardous status allows continued beneficial use of coal ash, but also specifies procedures for proper handling, transfer, and storage. • The rate of re-use of coal combustion products in the U.S. is now 52%, which is an all-time high. • If coal ash is not re-used, it must be stored in landfills or impoundments. Sources: EPA, 2014, https://www.epa.gov/coalash/coal-ash-rule American Coal Ash Association, not dated, https://www.acaa-usa.org/

4.3-2 Use of U.S. Coal Combustion Products (CCPs) Aprovechamiento de cenizas en EE.UU.

2016 52%

Source: American Coal Ash Association, not dated https://www.acaa-usa.org/ 4.3-3 Some Current Uses of Coal Ash and FGD Usos principales de cenizas de carbones

• Raw material in concrete products and grout. • Feedstock in the production of cement. • Fill material for structural applications and embankments. • Ingredient in waste stabilization and (or) solidification. • Ingredient in soil modification and (or) stabilization. • Component in road bases, sub-bases, and pavement. • Produce synthetic gypsum for use in construction and agriculture (FGD).

Source: American Coal Ash Association, not dated https://www.acaa-usa.org/ 4.3-4 Recovery of Rare Earth Elements from Coal Ash? Extracción de tierras raras en las cenizas • Rare earth elements (REE) are increasingly needed in commercial and military applications, including energy applications such as in the magnets of wind turbines. • Global supply of REE is strongly controlled by a single international source—China. • U.S. REE production (one mine with operations currently on hold) is not sufficient to keep up with U.S. demand. • REE from coal are strongly retained in coal ash during coal combustion for power generation. • Alternative REE sources, including coal and coal ash, and new methods of REE extraction from these sources, are currently being investigated in the U.S. and elsewhere. Source: U.S. Department of Energy, 2017a,b 4.3-5 Advantages of Coal Ash as a Source of REE Ventajas de la obtención de tierras raras de cenizas • In 1935, V.M. Goldschmidt proposed recovering rare elements, including REE, from coal ash. • Coal ash (fly ash, bottom ash) is produced in large quantities by utilities during coal combustion for power generation. • REE are strongly enriched in the ash fraction compared to REE contents of feed coals. • Fly ash is produced in a powdered form, eliminating the need for crushing of ores.

Source: Goldschmidt, 1935

4.3-6 Behavior of Elements During Coal Combustion Volatilidad de los elementos en la combustión

Very Volatile

Not Volatile Source: Ratafia-Brown, 1994, Fuel Process. Technol. 4.3-7 REE in Coal Ash vs. Coal and Upper Continental Crust Abundancia de tierras raras

• Plot compares REE for fly ash samples vs. average continental crust and U.S. average coal.

• REE patterns of coal ash and coal are similar, but REE contents are higher in coal ash. REE are also higher in coal ash than in Upper Continental Crust. Sources: Kolker and others, 2017a (Compilation of fly ash sample data) Taylor and McLennan, 1985 (Upper Continental Crust) Bragg and others, 1997; Palmer and others, 2015 (U.S. Average Coal) Korotev, 2009 (Chondrite normalization) 4.3-8 Oddo-Harkins Effect Efecto de Oddo-Harkins

• Elements with an even atomic number are more abundant than those with an odd atomic number. • Effect is apparent in the distribution of the REE. • Normalization to chondritic meteorites (chondrites) eliminates the effect. • Effect occurs because pairing of protons results in greater stability by each one offsetting the spin of the other. Sources: Taylor and McLennan, 1985 (North American Shale Composite (NASC)) Korotev, 2009 (Chondrite normalization) 4.3-9 Possible Modes of Occurrence of REE in Coal Ash Presencia de tierras raras en cenizas de carbones • Retention of trace phases in coal whose melting temperature may exceed boiler temperatures (e.g., monazite, xenotime). But these are much less common in coal ash than in coal. • Retention of trace phases in coal with size reduction by thermal shock. • Breakdown of trace phases with partitioning of REE into the melt. Melt is quenched to form glass phase that may host REE and other constituents. • Occurrence of REE in coal ash as nanoparticles.

4.3-10 REE-Bearing Trace Phases in Coal Fuentes minerales de tierras raras en carbones

Common REE-Bearing Trace Phases in Coal and Rocks Mineral Formula Predominant Melting Temp. REE (°C, 1 atm)

Apatite Ca5(PO4)3(OH,F,Cl) MREE 1,644 (fluorapatite) Zircon ZrSiO4 HREE 1,690 Monazite (Ce,La,Nd,Th)PO4 LREE, MREE 2,000+ Xenotime YPO4 Y, HREE 2,000+ 3+ Allanite (Ce,Ca,Y)2(Al,Fe )3(SiO4)3(OH) LREE, Y No Data

4.3-11 REE-Bearing Trace Phases in Coal Fuentes minerales de tierras raras en carbones

REE Occurrence in Coal Mineral Formula Predominant Reference REE Rhabdophane (Ce,La,Y)PO4.H2O LREE, Y Dai and others, 2014 Florencite CeAl3(PO4)2(OH)6 LREE Dai and others, 2016 Bastnäsite (Ce,Nd,La)CO3F LREE, MREE Zhao and others, 2017; Dai and others, 2016 Organic MREE, HREE Eskanazy, 1987; hosted Eskanazy, 1999

• Rhabdophane, florencite in some Chinese coals; • Bastnäsite in mineralized Chinese coals. • Organic-hosted REE recognized in Bulgarian coals.

4.3-12 Investigation of Fly Ash for REE Analisis de cenizas y tierras raras

• USGS obtained a suite of U.S. and International coal ash samples to determine REE mode of occurrence. • Preliminary characterization using microanalysis to determine the distribution of materials in coal ash samples. • Trace element microanalysis using an ion microprobe. • Preliminary results indicate occurrence of REE in fly ash glass phase. • Analytical approach described further in Session 5.

4.3-13 REE in Coal Fly Ash Tierras raras en partículas en suspensión

• Aluminosilicate glass has similar REE distribution as bulk sample. • Glasses containing Ca, Fe trend toward higher REE contents than pure Al-Si glasses. • REE are much less abundant in quartz, which makes up a small portion of the samples. • REE are also present in Fe-oxides. • Results suggest glasses are the primary REE hosts, as suggested by Taggart and others (2016), who found REE correlated with Al in bulk ash and difficulty extracting REE in HNO3. • Fly ash glass is a potential REE source.

Source: Kolker and others, 2017a 4.3-14 Summary – Topic 3: Beneficial Uses of Coal Ash Resumen − Tema 3: Aprovechamiento de cenizas

• Beneficial use of coal combustion products is allowed by its EPA designation as nonhazardous. • Coal combustion products are primarily used in construction materials. • Coal and coal ash are being considered as unconventional sources of needed rare elements, including rare earth elements (REE). • REE are strongly retained in the ash fraction during coal combustion, but REE-bearing trace phases are less common in coal ash than in coal. • Preliminary results suggest that REE enter the melt and might be recoverable from coal ash by fully digesting the glass phase. • Normalization of bulk REE data to chondritric values or to sample composites are useful ways of comparing and interpreting results.

4.3-15 References – Topic 3: Beneficial Uses of Coal Ash Referencias – Tema 3: Aprovechamiento de cenizas

Bragg, L.J., Oman, J.K., Tewalt, S.J., Oman, C.J., Rega, N.H., Washington, P.M., and Finkelman, R.B., 1997, U. S. Geological Survey coal quality (COALQUAL) database; ver. 2.0: U.S. Ge ological Survey Open-File Report 97–134, CD-ROM. [Also avaial ble at https://pubs.er.usgs.gov/publication/ofr97134.]

Dai, S., Luo, Y., Seredin, V.V., Ward, C.R., Hower, J.C., Zhao, L., Liu, S., Zhao, C., Tian, H., and Zou, J., 2014, Revisiting the Late Permian coal from Huayingshan, Sichuan, southwestern China—Enrichment and occurrence modes of minerals and trace elements: International Journal of Coal Geology, v. 122, p. 110–128. [Also available at https://doi.org/10.1016/j.coal.2013.12.016.]

Dai, S., Liu, J., Ward, C.R., Hower, J.C., French, D., Jia, S., Hood, M.M., and Garrison, T.M., 2016, Mineralogical and geochemical compositions of Late Permian coals and host rocks from the Guxu Coalfield, Sichuan Provinece, China, with emphasis on enrichment of rare metals: International Journal of Coal Geology, v. 166, p. 71 –95, accessed October 17, 2016, at https://doi.org/10.1016/j.coal.2015.12.004.

Eskanazy, G.M., 1987, Rare earth elements and yttrium in lithotypes of Bulgarian coals: Organic Geochemistry, v. 11, no. 2, p. 83–89. [Also available at https://doi.org/10.1016/0146-6380(87)90030-1.]

Eskanazy, G.M., 1999, Aspects of the geochemistry of rare earth elements in coal—An experimental approach: International Journal of Coal Geology, v. 38, nos. 3–4, p. 285– 295. [Also available at https://doi.org/10.1016/s0166-5162(98)00027-5.

Goldschmidt, V.M., 1935, Rare elements in coal ashes: Industrial and Engineering Chemistry, v. 27, no. 9, p. 1100–1102. [Also available at https://doi.org/10.1021/ie50309a032.

Korotev, R.L., 2009, “Rare earth plots” and the concentrations of rare earth elements (REE) in chondritic meteorites: Washington University in St. Louisb we page, accessed November 14, 2016, at http://meteorites.wustl.edu/goodstuff/ree-chon.htm.

4.3-16 References – Topic 3: Beneficial Uses of Coal Ash Referencias – Tema 3: Aprovechamiento de cenizas

Palmer, C.A., Oman, C.L., Park, A.J., and Luppens, J.A., 2015, The U.S. Geological Survey coal quality (COALQUAL) database version 3.0: U.S. Geological Survey Data Series 975. [Also available at https://doi.org/10.3133/ds975.]

Taggart, R.K., Hower, J.C., Dwyer, G.S., and Hsu-Kim, H., 2016, Trends in the rare earth element content of U.S.-based coal combustion fly ashes: Environmental Science and Technology, v. 50, no. 11, p. 5919–5926, accessed September 30, 2016, at https://doi.org/10.1021/acs.est.6b00085.

Taylor, S.R., and McLennan, S.M., 1985, The continental crust, its composition and evolution—An examination of the geochemical record preserved in sedimentary rocks: Boston, Blackwell Scientific, 312 p.

U.S. Department of Energy, National Energy Technology Laboratory, 2017a, Rare Earth Elements 2017 Project Portfolio, accessed May 17, 2017, at https://www.netl.doe.gov/File%20Library/Research/Coal/cross-cutting%20research/2017-REE-Portfolio.pdf.

U.S. Department of Energy, National Energy Technology Laboratory, 2017b, Rare earth elements from coal and coal by-products web page: National Energy Technology Laboratory website, accessed May 17, 2017, at https://www.netl.doe.gov/research/coal/rare-earth-elements.

U.S. Environmental Protection Agency [EPA], 2014, Final Rule—Disposal of coal combustion residuals from electric utilities: EPA website, accessed November 17, 2016, at https://www.epa.gov/coalash/coal-ash-rule.

Zhao, L., Dai, S., Graham, I.T., Li, X., Liu, H., Song, X., Hower, J.C., and Zhou, Y., 2017, Cryptic sediment-hosted critical element mineralization from eastern Yunnan Province, southwestern China—Mineralogy, geochemistry, relationship to Emeishan alkaline magmatism and possible origin: Ore Geology Reviews, v. 80, p. 116–140, accessed November 1, 2016, at https://doi.org/10.1016/j.oregeorev.2016.06.014.

4.3-16 Session 4 Topic 4 COAL ASH ENVIRONMENTAL ISSUES

4.4-1 Mobility of Constituents from Coal Ash? Lixiviación de los componentes de las cenizas

• Beneficial use of coal ash Generalized Coal Ash Impoundment Showing is permitted in the U.S. Possible Pathways of Migration of Leachates because coal ash has been designated as a nonhazardous waste by the U.S. EPA. • If not used, U.S. coal ash is stored in landfills or impoundments often along rivers and streams. • Standardized leaching tests, such as the EPA Toxicity Characteristic Leaching Procedure (TCLP), are used to test for element mobility from coal ash. Diagram not drawn to scale Sources: EPA, 1992 (TCLP) Deonarine and others, 2015 (diagram) 4.4-2 Mobility of Constituents From Coal Ash? Lixiviación de los componentes de las cenizas

• Recent U.S. coal ash spills from storage facilities, with considerable environmental impact: Kingston, Tennessee, December 2008, 5.4 million cubic yards of coal ash was released into the Emory and Clinch Rivers. After the spill, river sediments contained elevated levels of arsenic and mercury even after river water trace metals returned to normal levels. Eden, North Carolina, February 2014, 39 thousand tons of coal ash was released into the Dan River. • Other ash impoundments have been identified by the EPA as having potential for hazardous impacts in the event of a spill. • Ash utilization in construction materials and other uses can help reduce the need for storage of coal ash. Sources: Ruhl and others, 2010; Deonarine and others, 2015

4.4-3 Mobility of Constituents From Coal Ash? Lixiviación de los componentes de las cenizas

Coal ash spill site, Kingston, TN, December 2009 Sources: U.S. EPA, 2014; Immediate Area Impacted by Ash Spill Deonarine and others, 2015, 2016 Source: Ruhl and others, 2010, Envi. Sci Tech.

4.4-4 Potential for Mobility of Trace Elements Lixiviación de los componentes de las cenizas • Potential mobility of trace elements from coal ash differs by element. • Availability of oxygen effects degree of element leaching. • Standardized leaching test protocols only consider case where oxygen is available.

Deonarine and others, 2015, USGS Fact Sheet 2015-3037 4.4-5 Leaching Experiments for As and Cr in Fly Ash Lixiviación de As y Cr en cenizas de carbones • Coal ash leaching experiments up to 28 days to test for trace metal mobility with redox conditions controlled. • Arsenic is leachable under all conditions. • Chromium is partly leachable in one sample under oxic conditions and not leachable in other cases.

Source: Deonarine and others, 2015, 2016 4.4-6 Summary – Topic 4: Environmental Issues Resumen − Tema 4: Problemas ambientales • U.S. coal ash is classified as a nonhazardous waste, permitting its beneficial use. • When not used, coal ash is stored in landfills and (or) impoundments. With failure, ash or constituents from ash may be released into the environment. • Standardized leaching protocols, such as TCLP, generally indicate that trace constituents are not readily leachable from coal ash, but the test only applies to surface (oxygenated) conditions. • Availability of oxygen varies with depth in landfills and impoundments, and these differences in redox conditions can influence the mobility of trace constituents.

4.4-7 References – Topic 4: Environmental Issues Referencias – Tema 4: Problemas ambientales

Deonarine, A., Kolker, A., and Doughten, M.W., 2015, Trace elements in coal ash: U.S. Geological Survey Fact Sheet 2015–3037, 6 p. [Also available at https://pubs.usgs.gov/fs/2015/3037/.

Deonarine, A., Kolker, A., Doughten, M., Bailoo, J.D., and Holland, J.T., 2016, Arsenic speciation in bituminous coal fly ash and transformations in response to redox conditions: Environmental Science and Technology, v. 50, no. 11, p. 6099–6106, accessed September 14, 2016, at https://doi.org/10.1021/acs.est.6b00957.

Ruhl, L., Vengosh, A., Dwyer, G.S., Hsu-Kim, H., and Deonarine, A., 2010, Environmental impacts of the coal ash spill in Kingston, Tennessee—An 18-month survey: Environmental Science and Technology, v. 44, no. 24, p. 9272–9278. [Also available at https://doi.org/10.1021/es1026739.

U.S. Environmental Protection Agency [EPA], 1992, SW-846 Test Method 1311—Toxicity characteristic leaching Procedure: EPA website, 32 p., accessed November 17, 2016, at https://www.epa.gov/hw-sw846/sw-846-test-method-1311-toxicity-characteristic-leaching-procedure.

4.4-8 Laboratory Methods Laboratory Quality Assurance Introduction to Compositional Data Analysis SESSION 5 Session 5 Topic 1 LABORATORY METHODS

5.1-1 How to Study Trace Elements in Coal Métodos de estudio de elementos traza en carbones

Bulk Methods Microanalysis Whole Sample Specific Minerals

• X-Ray Diffraction- Minerals in • Scanning Electron Microscope bulk coal after low-temperature (SEM)- Texture and distribution of combustion of organics. minerals in coal individually. • Chemical Analysis- Element • Electron microprobe- Most distribution, e.g., by ICP-MS. abundant elements in individual • Selective leaching- Element minerals. forms (species) inferred from leaching behavior. • Laser Ablation ICP-MS and Ion • X-ray absorption fine structure Microprobe- Trace elements in (XAFS)- Element species individual minerals. determined directly by structure • Transmission Electron Microscope of X-ray absorption edge. (TEM)- Minerals in coal individually at very fine scale. 5.1-2 Common Methods for Bulk Trace Element Analysis Métodos de analisis geoquímico de elementos traza Method Advantages Disadvantages

ICP-MS Precision and Detection Limits; Must Get Sample Entirely Into All Elements Determined at Solution; Isobaric Interferences Once; Most Common Method must be Avoided or Corrected. Neutron Activation (INAA) Precision and Detection Limits; Access to a Reactor Facility; All Elements Determined at Handling of Radioactive Samples; Once; Digestion not Required Not as Widely Used as ICP-MS X-Ray Fluorescence Common Before Introduction of Detection Limits for Most ICP-MS. Many Elements Elements not as Good as ICP-MS. Determined Simultaneously. Irregular Surface Characteristics Determination on Pressed Pellets of Pressed Pellet can Effect of Powdered Solid Sample. Results. Isotope Dilution Very High Precision (1-2%) Requires Column Chemistry for Separation of Elements or Groups of Elements. Used in Specialized Applications where High Precision is Needed.

5.1-3 About Moisture Humedad de carbones • Generally, heating value increases and moisture decreases with increasing rank. Need to know moisture content to accurately express elemental concentrations in coal. • Moisture contents range from about 2% in bituminous coals to as much as 30% in low rank coals. Perfect analyses determined on a dry basis can be off by as much as 30% if moisture is not taken into account. • Moisture content can change if samples are not analyzed promptly after collection.

5.1-4 Whole Coal vs. Ash Basis Componentes en el total de la muestra o en sus cenizas • For inorganic analysis, coal samples are “ashed” in a laboratory furnace. • Ashing concentrates inorganic matter in coal for sample digestion and analysis. • Trace element results obtained are on an ash basis, but concentrations in the ash are a function of 1) whole coal element concentration; 2) proportion of ash present in coal; and 3) proportion of moisture present in coal. • To eliminate variability in 2) and 3), results need to be converted to a common basis—moisture-free whole coal.

5.1-5 Standards for Coal and Coal Ash Analysis Normas sobre análisis de carbones y sus cenizas • U.S. National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) https://www.nist.gov/srm. • SRM 1632d Trace Elements in Bituminous Coal Elements Certified: H, Na, S, Cl, K, Ti, V, Fe, Co, Cu, Rb, Sr, Sb, Ba, Hg, Pb, U. • SRM 1633c Trace Elements in Coal Fly Ash Elements Certified: Na, Mg, Al, K, Ca, Ti, Mn, Fe, Ni, Co, As, Rb, Sr, Cd, Sb, Ba, Hg, Pb • Values given with three levels of certainty: 1) Certified; 2) Reference; 3) Informational • Produced in batches having an expiration date.

5.1-6 Common Methods for Mercury Analysis Métodos de analisis geoquímico de mercurio Method Advantages Disadvantages

Thermal decomposition, Good Precision and Detection Somewhat Prone to Carry-over amalgamation, and atomic Limits. Analysis Done on Solid Effects After Runs of High-Hg absorption spectrophotometry, Powdered Sample. Inexpensive Samples if Not Careful. also called Direct Mercury Off the Shelf Analyzers Widely Analysis (DMA), EPA, 2007 Available. Cold Vapor Atomic Precision and Detection Limits Requires getting sample into Absorption (CVAA) Comparable to DMA. solution

Cold Vapor Atomic Better Detection Limits than Not as Widely Available as DMA, Fluorescence (CVAFS) DMA and CVAA. CVAA. Low levels of detection generally not needed for coal studies. Portable atomic absorption Real-time measurement of Generally not intended for bulk spectrometer with Zeeman mercury in the vapor phase. solid samples. Can be used for Background Correction Portable—excellent for field use. solids if other approaches are Amalgamation not required. unavailable.

5.1-7 Microanalysis Methods Microanálisis Method Advantages Disadvantages

SEM/EDX Excellent spatial resolution and Results for trace elements are imaging capability. Newer qualitative to semiquantitative models can operate at low with EDX. Need concentrations vacuum conditions for in the 10th’s of weight percent to environmental samples. determine trace elements.

Electron Microprobe Good spatial resolution. Sensitivity for trace elements Combines quantitative analysis limited to ~100-200 ppm; can be and wavelength-dispersive improved by long count times. elemental mapping capabilities.

TEM/EDX & HR TEM Spatial resolution in the Not widely equipped with EDX nanometers range. Elemental analyzers. If EDX equipped, data available if equipped with results for trace elements are EDX. Excellent for imaging semiquantitative, similar to SEM. particle surfaces.

5.1-8 Scanning Electron Microscope SEM/EDX Microscopio electrónico de barrido

EDX- Energy Dispersive Analyzer Used to identify major elemental constituents present and for qualitative analysis.

SEM Image of Fly Ash Particle

Scanning Electron Microscope (SEM) Also has backscattered electron (BSE) mode. SEM is good for particle morphology. BSE is good for particle composition.

5.1-9 Electron Microprobe Microsonda electrónica

Has wavelength dispersive spectrometers for quantitative analysis and element mapping in addition to SEM, BSE, and EDX

USGS Reston Labs

5.1-10 Electron-beam Instruments Instrumentos de rayos catódicos

• Instruments include SEM and electron microprobe. • Modes include: 1) Secondary electrons for imaging. 2) Backscattered electrons for imaging and composition. 3) Characteristic X-rays for elemental composition.

5.1-11 Microanalysis Microanálisis

BSE Fe Ca

Al Si

50 µm Backscattered electron imaging (BSE, above) and wavelength dispersive elemental mapping (right) shows composition. Images from USGS electron microprobe in Reston.

5.1-12 Transmission Electron Microscopy (TEM) Microscopio electrónico de transmisión surface coating

1 µm glassy ______spheres

High-resolution TEM shows nanometer-scale coating of carbonaceous material on fly ash particle surfaces. Source: Deonarine and others, 2015 USGS Fact Sheet 2015-3037 5.1-13 Trace Element Microanalysis Methods Microanálisis de elementos traza Method Advantages Disadvantages

Laser Ablation ICP-MS Good spatial resolution (10-25 No mapping capability. µm). Large range of elements Subject to isobaric interferences determined with good detection as in bulk ICP-MS. Destructive. limits. Measurement of isotopic Drills through sample grains in a ratios possible. few seconds.

Ion Microprobe Good spatial resolution (10-25 Not widely available due to high µm). Large range of elements if cost and complexity. No they form secondary ions. mapping capability. Ionization Excellent precision for isotopic potential varies by element. ratios. Used for radiometric Need standards that are a good dating of single zircons. matrix match to unknowns.

Synchrotron-based Good spatial resolution (10-25 Beam time allocated by proposal. Microprobe µm). Can do element Nearest facility, LNLS Brazilian concentration, speciation, and Synchrotron Light Laboratory. mapping on the same areas. For mapping, may be better to use electron microprobe.

5.1-14 Laser Ablation ICP-MS Ablación láser • Trace element microanalysis method uses a focused laser source coupled to an Laser ICP-MS analyzer. • Good method for ICP-MS microanalysis of Hg. Samples • Good for showing variation in sample composition with depth. • Method drills through samples in a few seconds. USGS Denver Labs

5.1-15 Pyrite Analysis by Laser Ablation ICP-MS Espectrometría de piritas

South Africa Highveld #4 Coal

20 microns 15 25 microns 64.5 ppm

10 Hg (ppm) Hg

0 0 20 40 60 80 100 120 140 160

400 20 Microns 25 Microns 691 ppm 983 ppm 300

200 As(ppm)

100 Pyrite 0 Backscattered Electron Image 0 20 40 60 80 100 120 140 160 Analysis Number

Source: Kolker and others, 2017b, Int. Journal 5.1-16 Coal Geol. Ion Microprobe Microsonda iónica

• Stanford/USGS SHRIMP-RG- Sensitive High Resolution Ion Microprobe-Reverse Geometry. - + • Negative or positive primary ion beam (O2 or Cs ). • Nominal spot size 15 microns. • Calibration using NIST standard glasses or other trace element standards. • Like laser ablation ICP-MS, ion microprobe standards must be homogeneous on the scale of analysis.

5.1-17 SHRIMP-RG Ion Microprobe Microsonda iónica SHRIMP-RG

Stanford/USGS SHRIMP-RG Ion Microprobe at Stanford University • A mass spectrometer that uses an ion beam as the ion source. • Can determine isotope ratios in addition to trace element data. - + • Primary beam of O2 or Cs ions, with detection in the ppm range. • 10-15 micron spot size. Sources: Bacon and others, 2012; Stanford University, not dated (photo). 5.1-18 Ion Microprobe Data for the REE Microsonda iónica para tierras raras

• Ion microprobe allows selective trace element and (or) isotopic analysis of individual grains within a sample. • Results show aluminosilicate glass has similar REE distribution as bulk sample. • REE are also present in Fe- oxides. • REE are much less abundant in quartz, which makes up a small portion of most samples. Source: Kolker and others, 2017a 5.1-19 Synchrotron Methods Sincrotrón

• Spectroscopic method for trace element bulk Arsenic Map analysis or microanalysis using high-energy X-rays U.S. Bituminous Coal Fly Ash from a synchrotron source. As XANES • Compositional analysis and element speciation on same samples or sample areas. • Requires beamline set up for XAFS (X-ray absorption fine structure) or XANES (X- ray absorption near- edge structure), a kind of Source: Deonarine and others, 2015, USGS Fact Sheet 2015-3037 XAFS.

5.1-20 Summary – Topic 1: Laboratory Methods Resumen – Tema 1: Métodos de laboratorio

• ICP-MS is the most widely used bulk analysis method. Advantages include excellent detection limits and detection of a wide range of elements all at once. • Trace element microanalysis complements bulk analysis by allowing direct determination of trace element mode of occurrence. • Common approaches to trace element microanalysis include electron-beam, laser, ion beam, and synchrotron X-ray methods. • Synchrotron-based methods can determine element speciation in addition to concentration or abundance.

5.1-21 References – Topic 1: Laboratory Methods Referencias – Tema 1: Metodos de laboratorio

Bacon, C.R., Grove, M., Vazquez, J.A., and Coble, M.A., 2012, The Stanford-U.S. Geological Survey SHRIMP ion microprobe- A tool for micro-scale chemical and isotopic analysis: U.S. Geological Survey Fact Sheet 2012-3067, 4 p., accessed July 9, 2018 at https://pubs.usgs.gov/fs/2012/3067/.

Deonarine, A., Kolker, A., and Doughten, M.W., 2015, Trace elements in coal ash: U.S. Geological Survey Fact Sheet 2015–3037, 6 p. [Also available at https://pubs.usgs.gov/fs/2015/3037/.

National Institute of Standards and Technology [NIST], not dated, SRM 1632d —Trace elements in coal (bituminous) web page: Standards reference materials, National Institute of Standards and Technology website, accessed November 19, 2016, at https://www- s.nist.gov/srmors/view_detail.cfm?srm=1632d.

National Institute of Standards and Technology [NIST], not dated, SRM 1633c —Trace elements in coal fly ash web page: Standards reference materials, National Institute of Standards and Technology website, accessed November 19, 2016, at, https://www-s.nist.gov/srmors/view_detail.cfm?srm=1633c.

Stanford University, not dated, Stanford/USGS SHRIMP-RG lab, Sensitive, high resolution ion microprobe – reverse geometry, accessed July 9, 2018, at https://shrimprg.stanford.edu/.

U.S. Environmental Protection Agency [EPA], 2007, Method 7473—Mercury in solids and solutions by thermal decomposition, amalgamation, and atomic absorption spectrophotometry: EPA web page, 17 p., accessed October 27, 2016, at https://www.epa.gov/wastes/hazard/testmethods/sw846/pdfs/7473.pdf.

5.1-22 Session 5 Topic 2 LABORATORY QUALITY ASSURANCE

5.2-1 Common Problems in ICP-MS Analysis Problemas con el análisis ICP-MS • Incomplete sample digestion, especially refractory trace phases such as zircon and monazite, resulting in incomplete recovery for some elements. • Interferences having the same mass as elements of interest (isobaric interferences). These can be combinations of elements or elements plus argon used as carrier gas. • Calibration, baseline, and carry over problems. Can be addressed by running standards and blanks and doing blank subtraction if necessary.

5.2-2 Sample Digestion for ICP-MS Preparación de muestras para análisis ICP-MS

• Digestion in a heated 3-acid (HNO3, HF, HCl) mixture is standard for metals analysis by ICP-MS.

• Can add perchloric acid (HClO4), only if a perchloric hood is available. • Acid digestion may not fully break down acid-resistant trace phases. • Sinter digestion- sample is mixed with sodium peroxide and sintered in a crucible at high temperature. • Sinter digestion generally used where total digestion is required, such as in REE determination.

5.2-3 REE-Bearing Trace Phases in Coal Minerales en carbones con tierras raras

Common REE-Bearing Trace Phases in Coal and Rocks Mineral Formula Predominant Melting Temp. REE (°C, 1 atm)

5.2-4 Fusion digestion vs. 4-acid digestion for REE Preparación de muestras para análisis de tierras raras

USGS GXR-4 Standard Fusion (2012) La Ce Nd Sm Eu Tb Gd Dy Tm Yb Lu GXR-4 measured 65.1 109 42 5.9 na 0.5 na 2.6 0.2 1.5 na GXR-4 certified 64.5 102 45 6.6 1.63 0.36 5.25 2.6 0.21 1.6 0.17 Recovery 1.01 1.07 0.93 0.89 na 1.39 na 1.00 0.95 0.94 na

4-Acid (2015) GXR-4 measured 31.2 67.4 26.3 4.4 1.01 0.4 3.4 2.1 0.1 0.8 0.1 GXR-4 certified 64.5 102 45 6.6 1.63 0.36 5.25 2.6 0.21 1.6 0.17 Recovery 0.48 0.66 0.58 0.67 0.62 1.11 0.65 0.81 0.48 0.50 0.59

Comparison of fusion (sinter) digestion with 4-acid digestion (incl. perchloric) by a commercial lab

5.2-5 Two Sinter Digestions for NIST SRM 1633c Sinterización para NIST SRM 1633c

Which analysis is better?

1633c Sinter Digest

Lab Y La Ce Nd Sm Eu Tb Dy Ho Er Tm Yb Lu 1 106 88.4 203 106 16 3.73 2.68 16.6 3.42 9.44 1.31 8.78 1.27 2 107 77.9 175 89.8 19.5 4.3 2.8 17 3.4 9.9 1.3 6.9 nd Cert. Ref. 87 4.67 3.12 18.7 1.32 Inf. 180 87 7.7 Comparison of sinter digestions in two labs for NIST SRM 1633c fly ash trace elements (in ppm). Cert = Certified Value; Ref. = Reference Value; Inf. = Informational Value. Values in ppm.

5.2-6 Chondrite Normalization Normalización de condritas

• Elements with an even atomic number are more abundant than those with an odd atomic number. • Effect is apparent in the distribution of the rare earths. • Normalization to chondrites or sample composites eliminates the effect. • Effect occurs because pairing of protons results in greater stability by each one offsetting the spin of the other. Sources: Taylor and McLennan, 1985 (North American Shale Composite (NASC)); Korotev, 2009 (Chondrite normalization). 5.2-7 Data Comparison using Chondrite Normalization Normalización de condritas

• Normalization should give a smooth pattern exception for Eu and in rare cases, Ce. • Kinks in normalized pattern suggest analytical problems for Lab 2. Values in ppm

1633c Sinter Digest Lab Y La Ce Nd Sm Eu Tb Dy Ho Er Tm Yb Lu 1 106 88.4 203 106 16 3.73 2.68 16.6 3.42 9.44 1.31 8.78 1.27 2 107 77.9 175 89.8 19.5 4.3 2.8 17 3.4 9.9 1.3 6.9 nd

5.2-8 Chondrite Normalization Normalización de condritas

Comparison of chondrite normalization approaches • No agreement on standard chondrite values to use. • I use approach suggested by Korotev (2009). • This approach uses data of Anders and Grevesse (1989) x 1.36 to give Sm = 0.200 ppm. • Need factors because some chondrites are carbonaceous and some are ordinary.

Normalization values (in ppm): 57 La 58 Ce 59 Pr 60 Nd 62 Sm 63 Eu 64 Gd 65 Tb 66 Dy 67 Ho 68 Er 69 Tm 70 Yb 71 Lu Reference 0.315 0.813 0.597 0.192 0.0722 0.259 0.325 0.213 0.208 0.0323 Masuda and others, 1973/1.2 0.319 0.820 0.121 0.615 0.200 0.0761 0.267 0.0493 0.330 0.0755 0.216 0.0329 0.221 0.033 Anders and Grevesse x 1.36 1.012 1.008 1.030 1.041 1.054 1.031 1.015 1.014 1.063 1.022 Proportion relative to Masuda and others, 1973/1.2 Others 0.31 0.808 0.122 0.6 0.195 0.0735 0.259 0.0474 0.322 0.0718 0.21 0.209 0.0322 UMASS, 2005 0.367 0.957 0.137 0.711 0.231 0.087 0.306 0.058 0.381 0.0851 0.249 0.0356 0.248 0.0381 Taylor and McLennan, 1985 Source: Korotev, 2009, http://meteorites.wustl.edu/goodstuff/ree-chon.htm. 5.2-9 ICP-MS Isobaric Interferences Interferencias isobáricas en ICP-MS

• Interferences can be the result of: 1) Isotopes with overlapping mass ranges (e.g., 204Hg vs. 204Pb); 2) polyatomic species (e.g., 40Ar16O vs 56Fe, 40Ar40Ar vs. 80Se, 35Cl40Ar vs. 75As); and 3) doubly charged species (e.g., 2x 69Ga+ vs. 138Ba2+). • Can get around interferences by: 1) Choosing an isotope without interferences; 2) use of equations to correct for interferences; and 3) use of collision-reaction cell (CRC) technology, where the ion beam passes through a cell that contains an inert or a reactive gas to eliminate interferences (e.g., Li and others, 2014). 5.2-10 IUPAC Periodic Table of the Isotopes Tabla periódica de los isótopos

Source: IUPAC, Chemistry International, 2011

5.2-11 Isotopes of As and Se Isótopos del arsénico y del selenio

Arsenic atomic number 33 75As 100%

Selenium atomic number 34 74Se 0.89% 76Se 9.37% 77Se 7.63% 78Se 23.77% 80Se 49.61% 82Se 8.73%

5.2-12 Example of Interference Correction for 75As Ejemplo de corrección de interferencia para 75As

• 35Cl40Ar interferes with 75As used to measure As. • Polyatomic species (37Cl + 40Ar) at mass 77 is used to give the contribution of (35Cl + 40Ar) at mass 75. • This correction is adjusted for an interference at mass 77 with any selenium present. • The contribution of 77Se is determined by measuring 82Se, which has few interferences, and can be used to obtain the proportion of any isotope of Se present.

5.2-13 Other Common Problems with ICP-MS Otros problemas frecuentes con ICP-MS • Calibration- Instrument response for standards defines a calibration curve. If values for unknowns (samples) are too far removed from the calibration, response must be extrapolated, a source of error in the analysis. Fit to calibration curve should have a high correlation. • Carry over- Occurs with insufficient wash-time between samples. If a sample with high concentration is run, some of this may carry over into the next run unless instrument response returns to its baseline.

5.2-14 Internal Checks on Data Quality Revisión de la calidad de los datos • Run standards for calibration and as unknowns. Are standard values reproduced? • Run total analytical blanks. Does instrument response return to baseline or is there carry over? Is there a source of contamination? Especially important for trace elements. • For major elements, do the analyses on an ash basis sum to near 100%? For coal, sulfur is a major element so this needs to be included in the analysis. • For rare earths, do the results form a smooth pattern on a chondrite-normalized plot? • Can you replicate analyses? If not, run it over again!

5.2-15 Run it Over Again Repeticiones

• Replicate Hg analyses for feed coals and density separates were obtained using two different DMA analyzers at USGS labs in Denver and Reston. • Results for 3 of 42 feed coals and 3 of 8 density separates showed poor agreement possibly due to Hg nugget effects. These were re-run (Table). • Values converged after multiple runs. • Averaged values were obtained for all density separates and the 3 feed coals (all values in ppb). Feed Reston Denver Denver Denver Reston Mean (n) Coal Original Original Re-run 1 Re-run 2 Re-run 9B 332 559 480 497 449 463 (5) 12A 211 312 310 271 285 278 (5) 12B 322 226 185 195 239 233 (5) Density Linear regression excludes three samples Separate in each plot. Perfect (1:1) 14A 44.6 76.5 60.6 (2) correspondence also shown for each 14B 49.5 59.8 54.7 (2) group of samples. 14C 78.4 115 96.7 (2) Source: Kolker and others, 2014, 14D 269 201 235 (2) 14E 285 300 304 (5) USGS Open-File 2014-1153 224 392 321 14F 262 647 697 722 631 592 (5) 14G 226 614 544 418 371 435 (5) 5.2-16 14H 421 494 458 (2) Summary – Topic 2: Laboratory Quality Assurance Resumen – Tema 2: Control de calidad de los análisis • Incomplete sample digestion and isobaric interferences are two of the most common problems in ICP-MS analysis. • REE-trace phases such as monazite, xenotime, allanite, and zircon are insoluble in multi-acid digestion used routinely for ICP-MS metals analysis. Sinter digestion is the best method for bulk determination of REE content. • Internal checks on data quality include running internal standards, blanks, and replicates. • For major elements, results should sum near 100% on an ash basis. REE data should give smooth patterns when plotted on a normalized plot. • If results are questionable, run them over again if possible.

5.2-17 References– Topic 2: Lab Quality Assurance Referencias – Tema 2: Control de calidad

Anders, E., and Grevesse, N., 1989, Abundances of the elements—Meteoritic and solar: Geochimica et Cosmochimica Acta, v. 53, no. 1, p. 197–214. [Also available at https://doi.org/10.1016/0016-7037(89)90286-X.]

Korotev, R.L., 2009, “Rare earth plots” and the concentrations of rare earth elements (REE) in chondritic meteorites: Washington University in St. Louis web page, accessed November 14, 2016, at http://meteorites.wustl.edu/goodstuff/ree-chon.htm.

Li, X., Dai, S., Zhang, W., Li, T., Zheng, X., and Chen, W., 2014, Determination of As and Se in coal and coal combustion products using closed vessel microwave digestion and collision/reaction cell technology (CCT) of inductively coupled plasma mass spectrometry (ICP–MS): International Journal of Coal Geology, v. 124, p. 1–4. [Also available at https://doi.org/10.1016/j.coal.2014.01.002.]

Masuda A., Nakamura N., and Tanaka T., 1973, Fine structure of mutually normalized rare-earth patterns of chondrites: Geochimica et Cosmochimica Acta, v. 37, p. 239-248.

University of Massachusetts-Amherst (UMASS), 2005, Lecture notes, Geology 321, petrology, accessed July 9, 2018 at http://www.geo.umass.edu/courses/geo321/Lecture%2016%20REE.pdf.

5.2-18 Session 5 Topic 3 INTRODUCTION TO COMPOSITIONAL DATA ANALYSIS Section Prepared by Ricardo Olea of USGS Eastern Energy Resources Science Center, [email protected].

5.3-1 Compositional data Datos composicionales Compositional data are measurements denoting proportional contributions of parts to a whole. Depending on the units, the sum of all parts may add up to a constant. This is the most common case, happening, for example, when the units are percent, parts per million, or mg/kg. Among the exceptions not adding to a constant, we have the case of concentrations measured in mg/L, µg/m3, or moles.

5.3-2 Closure Clausura

The relative information of compositional data sets them apart from conventional variables using absolute scales, such as speed, mass, and time.

For example, for every part j, when the D parts x j add to a constant κ , one component always can be obtained from the others

x j = κ − (x1 + x2 +K + x j−1 + x j+1 +K + xD ), For example, the constant is 100 when the parts are measured as percentages. Given the physical nature of parts, they cannot have negative values.

5.3-3 Correlations Correlaciones In addition, even for those compositional data that do not add to a constant, the covariances are always related

Var(x j )= cov(x1 ,x j )+ cov(x2 ,x j )+K + cov(x j−1 ,x j )+

cov(x ,x + )+K + cov(x ,x ), where, if N is the samplej j size1 and is thej D mean value of , mj x j 1 N 2 Var(x j )= ∑(xij − mj ) N −1 i=1 1 N cov(x j ,xk )= ∑(xij − mj )⋅(xik − mk ) N −1 i=1 Not surprisingly, blind use of conventional statistics in the analysis of compositional data often leads to misleading or unacceptable results. 5.3-4 Subcompositional incoherence Incoherencia subcomposicional Denotes obtaining contradictory results after elimination of one or more components. A typical example would be: (A) analysis of the some specimens with moisture ( x 4 ) versus (B) after drying them. Case Case (1997) Glahn - Pawlowsky Modified from Aitchison and and Aitchison from Modified

Note that drying resulted in a reversal in the sign of cov ( x 1 , x 2 ) . 5.3-5 Simplex Símplex

A set of values for D non- A set of values for D compositional variables compositional variables lands displays as a cloud in a D- inside a (D−1)-dimensional dimensional Cartesian space. space (simplex). Standard statistical techniques are valid for Euclidean distances in Cartesian coordinate systems, not in simplexes.

5.3-6 Warnings Advertencias

• Fallacy #1. When only a few components are measured, sometimes there is the perception that all problems with compositional data vanish because, in this situation, the parts with measurements are far from adding to a constant. • Fallacy #2. In the analysis of trace elements, typically the value of the concentrations are low. It is wrong to assume that the properties of compositional data disappear when all parts are small. • Fallacy #3. It is false to assume that spurious effects of applying conventional statistics to compositional data are always negligible or predictable. It is like playing Russian roulette. 5.3-7 Solutions Soluciones • Develop a new form of statistics taking into account the properties of compositional data. • Represent compositional data in an unconstrained real space (so it behaves like mass, time, or similar variables). The most successful approach has been the latter. The dominant approach has been to transform the data and analyze the resulting new values. Common aspects are: • Prepare ratios of variables to consider the relative nature of the data, thus emphasizing scale invariance; • Take natural logarithms of the ratios (log ratios) to have absolute scale fluctuation in ( − ∞ , +∞ ) , which sometimes also helps to have more symmetric probability distributions.

5.3-8 Log-ratio transformations using geometric means Transformaciones log ratio usando medias geométricas D The geometric mean, g ( x ) , of D parts is g(x) = x1 ⋅ x2 ⋅K ⋅ xD . For a sample of size N, grouping some or all parts into v and w , g(vij ) zij = c j ⋅ln , i = 1,2,K ,N . g(wij )

When c j, v j and w j are selected in such a way that the z j are Cartesian coordinates, the transformation is called an isometric log-ratio transformation (ilr), with j = 1 , 2 , K , D − 1 . For example, ilri1 = (2⋅3)/(2 + 3) ⋅ln[g(xi2 ⋅ xi3)/g(xi1 ⋅ xi4 ⋅ xi7 )], i = 1,2,K ,N .

If all c j = 1 , v j = x j, and w is the geometric mean of all parts, then the transformation is a centered log-ratio transformation (clr), with j = 1 , 2 , K , D . For example,

clri2 = ln[x2i /g(xi1 ⋅K ⋅ xiD )], i = 1,2,K ,N . 5.3-9 The biplot: A tool for exploring dependencies El biplot: Una herramienta para estudiar dependencias • Length of the red rays is proportional to the standard deviation explained by PC1 and PC2. Here, clr A has the largest variability. • Distance between ray ends away from the origin denotes difference in clrs. Clr M and clr V have quite similar variation. • Because the rays extend in opposite directions, relative increases in ash for different

From Olea and Luppens (2015) Luppens and Olea From samples are compensated with Software: Thió-Henestrosa and Comas, 2016. CoDaPack v2 user’s guide. http://ima.udg.edu/codapack/assets/codapack-manual.pdf relative reductions of the other parts, and the reverse. 5.3-10 Mapping Mapas

• Geostatistical processing of the information in the form of ilr transformations allows adequate mapping of parts. • Area indicated shows a high-ash zone with corresponding reduction in fixed carbon and other parameters.

5.3-11 (2015) Luppens and Olea From Modeling of compositional processes Modelaje de procesos composicionaless

Analogously to several other fields—such as time series analysis— analytical modeling of and others (2015) Glahn compositional data can - be used to test or Pawlowsky

describe the nature of From processes behind the Evolution in time of three parts growing observed value of the at different rates when the parameters λ = λ = λ = parts. are 1 1 ; 2 2 ; 3 3 .

5.3-12 Summary – Topic 3: Compositional Data Analysis Resumen – Tema 3: Análisis de datos composicionales

• When compositional data (parts) add up to a constant, use of conventional statistics in the analysis of these data can lead to misleading or conflicting results. • Parts sometimes do not add to a constant, but still present the same problems. • Compositional data expressed in percent are an obvious example of parts adding to a constant, which also applies to trace elements expressed in ppm. • To represent compositional data in an unconstrained real space, take ratios of variables and natural logarithms of the ratios to create an unconstrained absolute variation in scale. • Examples of log-ratio transformations include ilr (isometric log ratio), and clr (centered log ratio). Ilr gives coordinates in an unconstrained volume space. Clr is defined for each variable by dividing that variable by the geometric mean of all variables. • Interdependencies among log-ratio transformed variables can be explored using bi-plots, 2-d mapping, or time variation. • Use of compositional data analysis may or may not significantly change interpretation of compositional results, but it is more logical to play it safe.

5.3-13 References –Topic 3: Compositional Data Analysis Referencias –Tema 3: Análisis de datos composicionales

Aitchison J., and Pawlowsky-Glahn, V., 1997, The one-hour course in compositional data analysis or compositional data analysis is simple, in Pawlowsky-Glahn,V., ed., Proceedings of IAMG’97: The 3rd annual conference of the International Association for Mathematical Geology, held at the North Campus of the Universitat Politècnica de Catalunya, in Barcelona, September 22–27, 1997, Barcelona, Spain, CIMNE, v. 1, p. 3−35.

Olea, R.A., and Luppens, J.A., 2015, Mapping of coal quality using stochastic simulation and isometric logratio transformation with an application to a Texas lignite: International Journal of Coal Geology, v. 152, pt. B, p. 80−93. [Also available at https://doi.org/10.1016/j.coal.2015.10.003.]

Pawlowsky-Glahn, V., Egozcue, J.J., and Tolosana-Delgado, R., 2015, Modeling and analysis of compositional data: Chichester, United Kingdom, John Wiley & Sons, 247 p.

Thió-Henestrosa, S., and Comas, M., 2016, CoDaPack v2 user’s guide: University of Girona website, accessed August 25, 2016, at http://ima.udg.edu/codapack/assets/codapack-manual.pdf.

5.3-14