Persistent organic pollutants and mercury in the Himalaya

Abstract

Persistent organic pollutants and mercury are important contaminants due to their persistence in the environment and potential toxic effects on ecosystems and humans. Concerns related to these contaminants are particularly pertinent in Asia where the use of pesticides and mercury emissions have been increasing dramatically due to changing agricultural practices and rapidly expanding industrialization. Based on studies in European and North American mountain regions, evidence is increasing that alpine regions function as regional convergence zones for selected organic pollutants due to an effect called orographic cold trapping. It is hypothesized that such an effect may be particularly pronounced in the Himalaya because of dramatic elevational temperature and precipitation gradients relative to contaminant source regions in its immediate vicinity, and because of the regional monsoon system that has been shown to deliver particles and inorganic air pollutants to higher altitudes. A review of studies of persistent organic pollutants and mercury in the Himalayan ecosystem reveals that measurements of these contaminants are sparse and rarely adhere to strict quality control procedures, making it difficult to judge whether relatively high concentrations reported for these materials are indeed an indication of efficient transfer of toxic contaminants to Himalayan ecosystems. Knowledge gaps are identified and suggestions are made for research that would allow for the testing of the hypothesis that the Himalaya is an important cold trap for semi-volatile organic contaminants and mercury.