REDUCING THE RISKS OF PESTICIDE EXPOSURE VIA ATMOSPHERIC TRANSPORT

Authors: Hapeman, Cathleen; McConnell, Laura; Rice, Clifford; TORRENTS, ALBA - UNIV OF MD; GOEL, ANUBHA - UNIV OF MD; Prueger, John; HARMAN-FETCHO, JENNIFER - FORMERLY USDA/ARS; SMITH, RAMONA - FORMERLY USDA/ARS; Bialek Kalinski, Krystyna; Drakeford, Leticia

Submitted to: Proceedings of the Workshop on Agricultural Air Quality: State of the Science
Publication Type: Proceedings
Publication Acceptance Date: 7/16/2005
Publication Date: 6/4/2006
Citation: Hapeman, C.J., Mcconnell, L.L., Rice, C., Torrents, A., Goel, A., Prueger, J.H., Harman-Fetcho, J.A., Smith, R.D., Bialek Kalinski, K.M., Drakeford, L. 2006. Reducing the risks of pesticide exposure via atmospheric transport. Proceedings of the Workshop on Agricultural Air Quality: State of the Science. 1:674-676.

Interpretive Summary: The fate and transport of agriculturally-significant organic pollutants in the atmosphere is an important national issue. Volatile components and residues bound to dusts may rise into the atmosphere, travel long distances, and be deposited far from the point of origin through various deposition processes, risking contamination of sensitive ecosystems. Examining the environmental fate of agricultural pesticides is complicated by their sporadic and intense application to soils and crops throughout the growing season. Scientists at USDA-ARS have worked with their partners to conduct fundamental research on the atmospheric transport and deposition of semi-volatile organic pesticides at field, watershed, and regional scales. Results analysis of these will assist in identifying the major volatilization pathways from which more effective management practices to mitigate pesticide volatilization can be developed.

Technical Abstract: Research concerning the environmental fate and transport of semi-volatile organic pollutants has focused largely on urban/industrial chemicals such as polychlorinated biphenyls (PCBs) and polyaromatic hydrocarbons (PAHs). In many cases, these chemicals are present at equilibrium in the atmosphere, and their fate may be predicted using models based on partition coefficients. The study of the environmental fate of agricultural pesticides is complicated by their sporadic and intense application to soils and crops throughout the growing season. They are structurally more complicated and have more reactive sites compared with industrial pollutants; thus, they are frequently more polar and will degrade more readily and at variable rates. Agricultural pesticide residues are rarely present at equilibrium concentrations within the environmental compartments of interest: soil, plants, air and water. Scientists at USDA-Agricultural Research Service, in collaboration with their partners, have conducted fundamental research on the atmospheric transport and deposition of semi-volatile organic pesticides at field, watershed, and regional scales. A critical review and synthesis of these studies has revealed the following. The magnitude and duration of post-application pesticide volatilization is enhanced by high soil moisture and solar radiation (temperature), frequent light precipitation events, and low organic carbon soils. Riparian areas located adjacent to agricultural fields may serve as a trap for pesticide drift. Pesticide residues sorbed by the plant canopy can be readily washed off during a precipitation event and be delivered to nearby surface waters. Studies of regional deposition via precipitation have shown that the Henry’s constant of the pesticide will strongly influence its persistence in the atmosphere. Ecosystems at high altitudes and located downwind from agricultural regions are particularly vulnerable to atmospherically-derived pesticide residues. Colder temperatures will decrease pesticide degradation rates, and sensitive species will be exposed to pesticide residues for longer periods of time. Overall, pesticide residues are present in the atmosphere throughout the year. Deposition occurs continuously via particulate and gas phase deposition. Prevention of volatilization is the most efficient way to reduce atmospheric deposition loads and to lessen the impact of agricultural activities on their surrounding ecosystems.