OUTFLOW OF TRACE-METALS INTO THE LAPTEV SEA BY THE LENA RIVER

Freshwater concentrations confirm the pristine character of the Lena R iver environment as already pointed-out in a previous study with a lim ited set of data (Martin et al., 1993). Total dissolved concentrations of the freshwater are 13.8 +/- 1.6 nM, Cu, 4.4 +/- 0.1 nM, Ni, 0.054 +/- 0.047 nM, Cd, 642 +/- 208 nM, Fe, 0.2-0.3 nM Pb and 1.2 +/- 1.0 nM , Zn. For Zn and Pb, a simple mixing of the Lena River waters with the Arctic waters is observed. Relationships with salinity suggest that f or Cu, Ni and Cd, there is a mobilization of the dissolved fraction fr om the suspended matter, with an increase of the dissolved concentrati on of 1.5, 3 and 6 times, respectively. For Fe, the total dissolved co ncentrations follow an exponential decrease in the mixing zone and 80% of the total ''dissolved'' Fe is removed from the solution. For Cu, N i, Cd and Fe, the riverine end-members an 20 nM, 12 nM, 0.3 nM and 47 nM, respectively. When considering the input of total dissolved metals to the Arctic Ocean, the fraction attributed to the freshwaters from the Arctic rivers appears to be small (4% of the input of dissolved me tal to the Arctic Ocean for Cd, 27% for Cu, 11% for Ni and 2% for Zn). Metal concentrations in the Laptev Sea and Arctic Ocean are very simi lar, indicating a generally homogeneous distribution in the areas samp led.