USDA studies have provided new information about how the pesticide endosulfan moves through the atmosphere and how its molecular structure can change after it’s applied to crops.
Agricultural Research Service chemist Cathleen Hapeman and her colleagues led a five-year study that looked at the pesticide's journey out of Florida's Homestead agricultural region. The team established air sampling sites in Homestead, Everglades National Park and Biscayne National Park in Florida. The Everglades sampling site was six miles away from the Homestead sampling site, and the Biscayne sampling site was 12.5 miles away from the Homestead site.
The researchers found that samples from all three sites were dominated by gaseous concentrations of alpha-endosulfan, the pesticide's more volatile form. Average atmospheric concentrations of alpha-endosulfan in the Homestead samples were 10 times greater than levels in the Everglades samples, and 100 times greater than levels in the Biscayne samples.
Results from other modeling and real-time observations indicate that with the right meteorological conditions, atmospheric levels of endosulfans can increase by drift as well as by volatilization. This information can be used to help determine the fate of the pesticide in the environment.
The scientists also made new findings about alpha-endosulfan and about beta-endosulfan, a less volatile form of endosulfan. Both forms are applied to crop fields at a ratio of seven parts alpha-endosulfan to three parts beta-endosulfan. Results from previous studies had suggested that beta-endosulfan degraded fairly easily because it was usually found at low levels in the environment.
However, Hapeman's group found that beta-endosulfan could easily change into alpha-endosulfan in a process called isomerization, a chemical reaction where one molecule is changed into another molecule, which explains why beta-endosulfan was detected much less frequently during atmospheric sampling.
Hapeman works at the ARS Environmental Management and Byproduct Utilization Laboratory in Beltsville, Md. The scientists published their findings in a 2013 issue of Atmospheric Environment.