THE DISTRIBUTION OF DISSOLVED AND PARTICULATE MERCURY IN 3 SIBERIAN ESTUARIES AND ADJACENT ARCTIC COASTAL WATERS

Dissolved and particulate mercury distributions were determined in the three largest Siberian rivers and in adjacent Arctic coastal waters d uring two cruises. Water samples were collected in the Lena River and its mixing zone in the Laptev Sea in September 1991, and in the Ob and Yenisei Rivers and the adjacent Kara Sea in September 1993. Average t otal dissolved Hg concentration was 5.0 pM in the Lena River, 2.8 pM i n the Ob River and 1.5 pM in the Yenisei River, Mercury content of sus pended particulate matter was low, averaging 0.17 mg kg(-1) in the Len a and 0.05 mg kg(-1) in the Ob and Yenisei Rivers. These concentration s are lower than those observed in other world rivers affected by loca l input of man-made origin. In the estuarine mixing zones, higher conc entrations of dissolved and particulate Hg which may originate from th e spring flood were found. The carbon cycle is apparently a driving me chanism for Hg distribution in Arctic coastal waters. Particulate Hg c ontent was positively correlated with the content of organic matter of the particles. In the Kara Sea, uptake by phytoplankton is suspected to be responsible for the increase in particulate Hg levels. Mercury f luxes from the three rivers to the Arctic Shelf are estimated and comp ared to direct atmospheric inputs.