MATERIALBALANSER FÖR VÄNERNS FOSFOR- OCH KVÄVETRANSPORTER 1970-1989 / Nitrogen and Phosphorus Mass Balances for Lake Vänern 1970-1989
Phosphorus and nitrogen mass balances for Lake Vänern show that ca 70 % of the total phosphorus input accumulates in the sediments, while 25 to 40 % of the total nitrogen input was lost via sedimentation and denitrification. These results are based on total input calculations for the period 1970 to 1989, and transport via the outlet Göta älv (calculated from monthly measurements, taken from the station Vargön). Nitrogen and phosphorus concentrations were higher in the outlet than in the central parts of the lake. This means that mass balance models constructed to estimate the concentrations in the lake from loading data result in lower export via the outlet and higher retention in the lake compared with the calculations based on data from the outlet. Possible explanations for the observed concentration differences are discussed.