Observation of organochlorine pesticides in the air of the Mt. Everest region.

High mountains have been suggested to play an important role in the global transport of persistent organic pollutants, yet observation of these pollutants in high mountains is very limited. In the summer of 2002, air samples were collected at Dingri at a height of 4400 m above sea level (m a.s.l.) and at Rongbuk Valley (4976 m a.s.l.) in the Mt. Everest region and analyzed using large volume injection gas chromatography tandem mass spectrometry. The mean concentrations of organochlorine pesticides (OCPs) in the samples were 19.2, 11.2, 7.7, 8.9, 10.4, 27.6, 5.1, 5.1, and 3.7 pg m(-3) for alpha-HCH, beta-HCH, gamma-HCH, HCB, heptachlor, alpha-endosulfan, p,p'-DDE, o,p'-DDT, and p,p'-DDT, respectively. Backward trajectories were used to assess the association between source regions, transport paths, and observed OCP concentrations. During the sampling period, the o,p'-DDT/p,p'-DDT concentration ratios were observed to be between 1.23 and 1.41, much higher than that of technical DDT, indicating the existence of a DDT source other than technical DDTs in the source regions.