A Study of the Organic Composition of Haboob Particulate Matter

Jershon Eagar, Denise Napolitano, Aurelie Marcotte and Pierre Herckes Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ

Introduction Results Discussion

Each July marks the beginning of the summer monsoon Haboob events are accompanied by a brief abrupt Haboob events are characterized by short spikes in PM2.5 Organic and Elemental Carbon Concentrations in PM2.5 season in the southwestern United States. Storms Samples, 7/11/13 – 7/18/13 increase in PM2.5 as measured by the US EPA AQS. concentrations (25 - 50μg/m³). The levels were moderate; the US EPA

) 25 originating south of Phoenix create cold fronts that travel ³ During these events, our samples indicate increases in 24-hour PM air standard is 35 μg/m³. Following the event, - 2.5 Phoenix PM2.5 m northwest towards Phoenix. The presence of loose soil along 20 OC and EC concentrations in PM . The OC/EC ratio concentrations go down to typical summer urban levels rather quickly.

gC PM2.5 EC 2.5 μ the storm’s path, as well as its downward trajectory into the ( PM2.5 OC increases slightly during mild haboobs and blowing 15 An increase in PM2.5 measured by the US EPA AQS corresponds with valley, causes a wall of sand and dust to be suspended into dust events but significantly increases during strong 10 measured increases of organic and elemental carbon mass in PM2.5 at the air and commingle with urban particulate matter (PM). haboob events. Organic and Elemental Carbon our sampling site. This type of storm is commonly known as a haboob. 5 1.2

and and Carbon Conc. Concentrations in PM2.5 Samples,

2.5 0 7/1/14 – 8/14/14 During strong haboobs, we observed a significant increase in the ratio 3

The composition of haboob dust is not well known and it PM 25 of organic carbon to elemental carbon. A smaller OC/EC ratio increase is remains unclear whether the composition of haboob dust 2.5 y = 0.1609x observed for mild haboobs, and the OC/EC ratio measured during

20 0.8 significantly impacts background urban PM. R² = 0.4202 blowing dust events is closer to that of background urban PM. This is

OC/EC Ratio g/m³) 2 μ

15 g/m³) Ratio This project aims to characterize the carbonaceous fraction μ indicative of an increase in the influx of biogenic material with EC (

2.5 1.5 EC (

10 of haboob dust so that we may begin to learn how air PM Strong Haboobs increasing haboob strength. A distinction between a haboob and 0.4 Carbon Carbon quality in Phoenix is affected by the occurrence of haboob 2.5 1 Mild Haboobs blowing dust may also be made. 5 PM Dust then Rain events. Heavy Rain 0.5 The CPI of long-chain n-alkanes increases during a haboob, 0 Background 7/11/13 7/13/13 7/15/13 7/17/13 Background Average 0 0 corroborating an influx of biogenic material. Date 0 3 6 0 10 20 30 40 PM2.5 OC (μg/m³) PM2.5 OC (μg/m³) The combined PAHs analyzed reached 4.8ng/m³ during a strong haboob. That level is 105 times lower than OSHA and NIOSH workplace eight-hour limits for total PAHs. Benzo[a]pyrene, which is classified as a Experimental Setup n-alkanes in PM collected July 11-17, 2013 were 35 2.5 probable human carcinogen, reached 1ng/m³. That is 600x lower than quantified. A brief increase in the concentration of 30 the EPA one-year average level for health concern. Sample Collection odd-chain length n-alkanes was observed during the Haboob PM and background urban PM samples were 25 July 12, 2013 haboob event. This increase was more The brief increases in elemental carbon concentrations and PAH 20 collected during the July – September monsoon seasons of n-C29H60 pronounced for long-chain n-alkanes. concentrations during haboobs may suggest a resuspension of 15 n-C31H64 anthropogenic material. 2013 and 2014 at the ASU campus in Tempe, Arizona using The carbon preference index (CPI) for n-alkanes was Alkanes (ng/m³)Alkanes 10 high-volume aerosol samplers. calculated: 5 퐶표푑푑 Instrumental Analysis 0 CPI = 5 퐶푒푣푒푛 The PM2.5 fractions (PM with aerodynamic diameters less than 2.5 micrometers) were analyzed by thermal optical 4 Alkanes(ng/m Conclusions n-C23H48 A CPI close to one is characteristic of a dominance of transmittance to determine atmospheric concentrations of n-C25H52 3 anthropogenic emission sources. A CPI greater than Total PM mass increases significantly during haboob events. Increases organic and elemental carbon in background urban PM and five is indicative of a contribution of biogenic 2.5 2 in OC concentrations in PM2.5 and the CPI of long-chain n-alkanes haboob PM. The samples were then analyzed by GC/MS to 3 ) components to aerosol. An increase in the CPI was suggest an influx of biogenic material during haboob events. identify n‐alkanes, polycyclic aromatic hydrocarbons (PAH), 1 observed during this haboob event. and oxy‐polycyclic aromatic hydrocarbons (oPAH). Resuspension of anthropogenic matter during haboobs is indicated by 0 25 6 increases in EC and PAH concentrations. The elevated levels of PAHs Phoenix PM2.5 Weather Data were lower than long-term standards for health concern. CPI (all) Odd/EvenRatio Mass

20 )

Weather and air quality data were obtained from NOAA and ³ -

m 4

15 400 the US EPA Air Quality System at two locations close to the μg (

2.5

ASU Tempe campus (see map below): 10 ) ³ PM 2 300 benzo[a]anthracene 5 anthracene Further Experimental Work 200 benzo[g,h,i]perylene NOAA archived weather data at 0 0 7/11/13 7/13/13 7/15/13 7/17/13 Additional sample analyses are currently ongoing and chemical Phoenix Sky Harbor International Airport PAH Conc. (pg/m PAH 100 Date composition data will be available for more time periods.

0 The chemical analysis will be extended to other organic molecules that 1200 100 are used as tracers for specific carbonaceous aerosol sources, including ASU Sampling Site benzo[a]pyrene TempePM

Roof of ASU Life Sciences Bldg. The haboob events observed in 2013 and 2014 were biogenic (plant and bacterial materials), anthropogenic (vehicle )

³ 900 pyrene 75 accompanied by an increase in the measured Tempe PM2.5 emissions), and mixed (biomass burning) molecular markers. concentration of PAH characteristic of anthropogenic 600 50 2.5 Additional data analysis will be performed by combining organic and

( emissions. μ g/m³) inorganic/metal aerosol data (see companion poster, A. Marcotte et al.).

PAH Conc. (pg/m PAH 300 25 The charts to the right show the changes of PAHs in a haboob event. The largest increases were pyrene and benzo[a]pyrene which reached 1 ng/m³. Anthracene and 0 0 Maricopa County 6/30/14 7/2/14 7/4/14 7/6/14 7/8/14 7/10/14 Acknowledgments Air Monitoring Site benzo[g,h,i]perylene didn’t increase to as high of levels Date AQS (Air Quality System, US EPA) (0.1 ng/m³) but remained elevated longer.