sign in sign up
<<
Home , Gypsum

CCPs in

ENVIRONMENTAL RISK ASSESSMENT FOR GYPSUM TELLS POSITIVE STORY By Karen Bernick

mending with !ue “…the risk assessment has shown that FGD gypsum gas desulfurization (FGD) contains extremely low concentrations of most trace gypsum o"ers a host of promising bene#ts to elements, about the same as found in mined gypsum agriculture, and this bene#cial use and, in most cases, lower than background soils.” providesA an opportunity for power plants to reduce disposal costs. and trouble spots; and other Chaney says the only risk he has iden- But is it safe? contaminant risks in plant uptake and food. tified occurs if livestock producers He is the lead USDA researcher on the FGD allow ruminants to eat large quanti- $e answer appears to be a resounding gypsum risk assessment. ties of stockpiled gypsum. “If livestock “yes” according to early reports from a producers prevent ruminants from eat- comprehensive risk assessment by the $e USDA-EPA assessment exam- ing gypsum by fencing in stockpiles, U.S. Department of Agriculture (USDA) ines what Chaney calls “new” FGD and limit grazing until after a rainfall to and U.S. Environmental Protection gypsum, a high quality form of syn- wash adhering FGD gypsum from for- Agency (EPA). $e assessment, likely thetic gypsum sought by agricultural age leaves, the risk is prevented,” to be concluded in 2013, addresses crop producers for its improvement he says. potential risks that land applications of bene#ts, and supplies, FGD gypsum could pose to human health purity and relative low cost versus mined RISK ASSESSMENT or the environment. gypsum. $e same material is used PROCEDURES for producing wallboard. It is a byprod- $e USDA-EPA risk assessment evaluated “USDA and EPA felt that a risk assess- uct at coal-fueled power plants equipped an exhaustive list of possible pathways for ment would help states in their with state-of-the-art emission scrubbing contaminant exposure from applied FGD bene#cial use designation process,” says systems, and is created a%er !y ash removal. gypsum, including via: Rufus Chaney, a research agronomist Forced oxidization is used to transform cal- at the USDA-Agricultural Research cium sul#te into dihydrate, a t Farm and garden crops Service’s Environmental Management highly pure and consistent form of synthetic t Soil ingestion by children, livestock and Byproduct Utilization Laboratory, in gypsum. and wildlife Beltsville, Maryland. t Livestock, wildlife and soil Chaney says “old” FGD gypsum was pro- organism exposure to crops grown Bene#cial use of non-hazardous mate- duced during !y ash removal and o%en had on amended soils rials, such as gypsum used for soil excessive residues of , arsenic and t Leaching and runo" from amended amendment, is regulated at the state level, . “$ese were a source of concern, #elds explains Chaney, who is an expert in the depending on the coal source,” he says. study of trace elements, plant uptake, bio- Data were collected from a number of availability, soil chemistry and toxicity. For But contaminants in the new material are USDA-EPA collaborative FGD-gypsum the past 35 years he has performed intricate at levels so low that Chaney and his team #eld studies recently completed or cur- risk assessments for the use of biosolids in have found no evidence of any toxicity rently underway in Alabama, Georgia and soils; remediation of toxic sites; cadmium, risks. “FGD gypsum is good stu",” he says. Mississippi, along with other data from

Issue 1 2012 Ash at Work ‡ 19 gypsum experiments sponsored by the “The USDA-EPA risk Trace Elements in Electric Power Research Institute (EPRI) NEW Gypsum and Soils in Ohio, Indiana, Wisconsin and North assessment evaluated an FDG- 95%ile-US Dakota. Assessments were performed exhaustive list of possible Element G-95%ile Soil to identify and quantify any potential pathways for contaminant As 10.1* 12. contaminants in soil, water, plant and gypsum soil amendments collected in the exposure from applied B 146. . various experiments. FGD gypsum…” Cd 0.29 0.6 TRACE ELEMENTS Co <2.0 17.6 Soil scientists use milligrams (mg) per nutritional quality of forages grown on Cr 8.69 70. kilogram (kg), which is equal to parts per FGDG amended soils, Chaney adds. Cu 2.52 30.1 million, to describe the concentration of Mo 2.48 2.16 trace elements in soil. Elements are usu- ARSENIC Ni 2.39 37.5 ally considered at trace levels if they are Arsenic levels in FGD gypsum are lower found at 100 ppm or less. In the FGD than 95 percent of US background soils Pb 1.0 38.0 gypsum assessment, Chaney looked for (10.1 vs. 12 mg/kg) but Chaney says there Se 27.9 1.0 trace element concentrations higher than is a debate within the EPA about the Zn 15.0 103. corresponding concentrations in “back- appropriate limit for arsenic in soils. *Midwest Soil Improvement ground” or typical uncontaminated U.S. Symposium, August 23, 2011. EPRI agricultural soils as documented by the “Toxicologists at EPA have calculated that data analyzed by Dayton at Ohio State U.S. Geological Survey and USDA. the limit for soil arsenic should be 0.43 University. USGS soil data (right col- mg/kg soil based on cancer risk,” explains umn) published by: Smith, D.B., W.F. If a trace element in FGD gypsum is lower Chaney. Recently they have proposed to Cannon, L.G. Woodru", R.G. Garrett, than the level in background U.S. soils, reduce this 17-fold lower, which would be R. K. Klassen, J.E. Kilburn, J.D. Chaney says contamination problems 0.025 mg As/kg soil, about 1/20th of nor- Horton, H.D. King, M.B. Goldhaber have not been found. “No matter how mal soil arsenic concentration, according and J.M. Morrison. 2005. Major- and hard we try, no matter how many 100 to Chaney. $e proposed increase to the trace-element concentrations in soils years we apply this quality of gypsum, we arsenic cancer slope factor is for one in a from two continental-scale transects of are not going to be able to build up the million chance of lifetime (70 years) risk the and . USGS concentration level with the new FGD for several cancers in humans with high Open-File Report 2005-1253.] gypsum,” Chaney says. arsenic exposures from contaminated drinking water. Figure 1 – Trace Elements in “New” Chaney says the risk assessment has Gypsum and Soils shown that FGD gypsum contains $e present 0.43 limit suggests that nearly extremely low concentrations of most all soils would be deemed toxic, Chaney most of the mercury goes into !y ash and trace elements, about the same as says. “$at number is below the 1st per- not the gypsum. Some FGD gypsum has found in mined gypsum and, in most centile of US natural soil – average US soil slight elevations of mercury above typical cases, lower than background soils. [See arsenic is 5 ppm,” he explains. “We have background soils and mined gypsum, but Figure 1.] found no evidence that this level of natu- Chaney says no risk has been identi#ed. ral soil arsenic actually comprises risk to He explains that soil is a natural “sink” for SELENIUM humans or the environment.” aerosol mercury meaning soils and plants “With the exception of selenium and may emit mercury during the day but boron, trace elements in FGD gypsum are OTHER TRACE ELEMENTS collect mercury at night; emissions vary lower than the 95th percentile of US back- Boron is slightly higher in concentration by season (loss in summer but accumula- ground soils,” Chaney says. for FGD gypsum than background soils tion in winter) so it is di&cult to identify but no cause for alarm, says Chaney. At a risk from the small amount added by Chaney notes that the selenium level in typical application rates, FGD gypsum over long periods of bene#cial FGD gypsum is not able to cause risk gypsum supplies no more boron than a use applications. because of the high levels of calcium sul- farmer would typically add if he or she fate which comprise gypsum. “Selenate were adding it as fertilizer. Further, boron Chaney says the many positive bene#ts of in FGD gypsum is in a matrix of calcium does not accumulate in soils over time, using FGD gypsum on cropland, combined sulfate, and the sulfate inhibits uptake of and boron are periodically with the lack of risks to human health or the selenate by plants,” Chaney says. “$ere is applied for many crops (alfalfa, vegeta- environment, spells a very positive story for no evidence to suggest it would be a toxic bles, etc.). bene#cial reuse in agriculture. O factor to humans, livestock, or wildlife or have any adverse route from plants grow- Mercury is another trace element that ing on amended soils.” $is selenate would is sometimes associated with Coal Karen Bernick is a marketing communica- be a low-grade fertilizer and improve the Combustion Products, but Chaney says tions consultant based in Iowa.

‡$VKDW:RUNIssue 1 2012