AIR-WATER GAS-EXCHANGE OF ORGANOCHLORINE COMPOUNDS IN LAKE-BAIKAL, RUSSIA

Air and surface water samples were collected at Lake Baikal, Russia, d uring June 1991 to determine concentrations of organochlorine pesticid es and polychlorinated biphenyl (PCB) congeners. These data were combi ned with Henry's law constants to estimate the gas flux rate across th e air-water interface of each compound class. Air samples were collect ed at Lake Baikal and from nearby Irkutsk. Water samples were collecte d from three mid-lake stations and at the mouth of two major tributari es. Average air concentrations of chlorinated bornanes (14 pg m(-3)), chlordanes (4.9 pg m(-3)), and hexachlorobenzene (HCB) (194 pg m(-3)) were similar to global background or Arctic levels. However, air conce ntrations of hexachlorocyclohexanes (HCHs), DDTs, and PCBs were closer to those observed in the Great Lakes region. Significantly higher lev els of these three compound classes in air over Irkutsk suggests that regional atmospheric transport and deposition may be an important sour ce of these persistent compounds to Lake Baikal. Air-water gas exchang e calculations resulted in net depositional flux values for alpha-HCH, gamma-HCH, DDTs, and chlorinated bornanes at 112, 23, 3.6, and 2.4 ng m(-2) d(-1), respectively. The total net flux of 22 PCB congeners, ch lordanes, and HCB was from water to air (volatilization) at 47, 1.8, a nd 32 ng m(-2) d(-1), respectively.