Nitika Dewan FRIDay 2015 Oral Presentation Abstract

Tracing dust sources using stable lead and strontium isotopes in Central Asia

Nitika Dewan1, Brian J. Majestic1, Michael E. Ketterer2, Justin P. Miller-Schulze3, Martin M. Shafer4,5, James J. Schauer4,5, Paul A. Solomon6, Maria Artamonova7, Boris B. Chen8, Sanjar A. Imashev8, Greg R. Carmichael9

1Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208, USA

2Department of Chemistry, 1201 5th Street, Metropolitan State University of Denver, Denver, CO 80204, USA

3Department of Chemistry, 6000 J Street, California State University, Sacramento, CA 95819, USA

4Wisconsin State Laboratory of Hygiene, 2601 Agriculture Drive, Madison, WI 53718, USA

5Environmental Chemistry and Technology Program, 660 North Park Street, University of Wisconsin, Madison, WI 53706, USA

6U.S. EPA, Office of Research and Development, Las Vegas, NV 89193, USA

7Institute of Atmospheric Physics, 109017 Moscow, Russia

8 Kyrgyz-Russian Slavic University, 44 Kievskaya Street, Bishkek 720000, Kyrgyzstan

9Department of Chemical and Biochemical Engineering, The University of Iowa, Iowa City, IA 52242, USA

From 1960 to 2014, the Aral Sea’s surface area has receded about 90% in size from 68,000 km2 to 8,444 km2. Consequently, newly exposed sediments are resuspended by the wind and are now a source of atmospheric particulate matter in Central Asia, which may have an impact on human health and climate. In this study, strontium (Sr) and lead (Pb) stable isotopic ratios, along with other elemental compositions, are used to explore the extent to which Aral Sea sediments are an important source of air pollution to Central Asia. PM10 ambient samples were collected at the Bishkek and LIDAR (in Teploklyuchenka) sites from mid-July 2008 to mid-July 2009. These air quality sites are located ~1,200 km and ~1,500 km east-southeast of the Aral Sea. The PM10 samples were collected for detailed chemical analysis every other day and included dust and non-dust events. Soil samples also were collected during the study at the Aral Sea and near the Bishkek and LIDAR sites, resuspended, and collected as PM10 for chemical analysis. The average 87Sr/86Sr ratio for the Aral Sea sediments was 0.70992 (range, 0.70951 – 0.71064). The Sr isotope ratio in the surface soils in Kyrgyzstan averaged 0.71579 (range, 0.71448 – 0.71739), which is significantly different from the Aral Sea sediments (t-test, p < 0.05). In contrast, the airborne PM10 collected in Kyrgyzstan had an average 87Sr/86Sr ratio of 0.71177 (range, 0.70946 – 0.71335), which is between the two ratios, indicating a possible mixture of sources. However, since no differences in Sr ratios were observed between dust and non-dust events, this imply that the impact of Aral Sea sediments on the sampling sites is minimal. The elemental composition and stable Pb isotope ratios are employed to further understand the source of PM10. Both indicate an anthropogenic source of airborne Pb in Kyrgyzstan.

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