Contamination of Lake Baikal with Organic Priority Pollutants

Abstract

Lake Baikal is the largest reservoir of natural fresh water in the world. Nevertheless industrial enterprises on its banks as well as river effluents and transboundary transfer contaminate this unique basin. However an overall estimation of the presence of all classes of organic pollutants has never been done. The present work was launched to identify organic toxicants, especially the priority pollutants of lake Baikal and to find out their routes of appearance. We have studied the presence of organic priority pollutants (US EPA list) in samples including water, soil, snow and biota like molluscs, fish, birds and seals in order to clarify also the accumulation of the pollutants in trophic chains. The chemical studies were accompanied by biotesting. The results obtained in 1996-1997 throw light upon the presence of organic toxicants (PAHs, phenols, organochlorines, phthalates) in birds and seals, i.e. the representatives of the highest trophic levels. The results demonstrate high level of contamination of the studied animals. The food of the most polluted species consists mainly of molluscs (not fish); thus we propose that the major role of transfer of toxicants into the higher trophic levels is via water and aquatic invertebrates. The identification of more than 70 organic compounds in the samples was the first step for the creation of the priority pollutants list for the lake. Besides that the data array obtained allows differentiation between contaminants really characteristic for Baikal and those which are accumulated by birds during their winter stay in China.