By Ann Perry,
U.S. Department of Agriculture (USDA) studies have provided new information about how the pesticide endosulfan moves through the atmosphere, and how its molecular structure can change after it is applied to crops.
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 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 such low levels in the environment.
However, Hapeman's group found that beta-endosulfan could easily change into alpha-endosulfan in a process called isomerization, which explains why beta-endosulfan was detected much less frequently during atmospheric sampling.