Glaciers Are A Source Of Residual DDT

Glacier meltwater is a probable source of the banned pesticide DDT in Antarctic marine ecosystems, according to a new study (Environ. Sci. Technol., DOI: 10.1021/es702919n). Heidi N. Geisz and Rebecca M. Dickhut of the College of William & Mary's Virginia Institute of Marine Science and colleagues made the observation while examining the environmental cycles of persistent chemicals that have been transported to Antarctica via the atmosphere. They used gas chromatography/mass spectrometry to analyze fat from postmortem Adélie penguins, which live only in Antarctica, for DDT and its derivative DDE. Ratios of the compounds indicate that the observed levels of DDT come from old sources rather than new ones. Geisz says they expected to see decreasing levels of DDT, as they do in Arctic birds. "We were surprised to see no decline in total DDT in these penguins since the 1970s," she says. Other researchers previously did not find DDT in air, snow, recently formed ice, or ocean water in the Antarctic, but they did find the pesticide in water from thawing glaciers. Geisz and coworkers estimate that 1–4 kg of DDT is released annually from the continent's glaciers.