Atmospheric transport of environmental pollutants to Lake Mjøsa.

Abstract

This report describes the results of a study to reveal the sources that control levels of selected contaminants in Lake Mjøsa. The project focused on sources to air, airborne transport and deposition of PCBs, PBDEs, HBCDDs, and Hg. The following activities have been conducted from summer 2006 to summer 2009: Active air measurements of selected POPs at Kise, passive air measurements of selected POPs, and Hg-measurements and field campaigns. Based on these and earlier measurements air transport modeling and mass balance calculations were performed. The atmospheric PCB levels for the Mjøs region, measured at Kise, reflects typical Norwegian background levels and no time trend could be identified. Two passive sampling sites close to Gjøvik show elevated PCB concentrations. River water inflow is dominating inflow of PCB7 to the lake (53%), followed by atmospheric deposition (32%) and STPs (15%). PBDE measured at Kise reflects background level and no time trend could be identified. The passive air samples showa significant local source of PBDEs located in Lillehammer. Elemental mercury in air at Kise was comparable to the northern hemispheric background mean. Episodes with high concentrations of atmospheric mercury were observed year round, mainly associated with transport of polluted air from Europe. The main contributor of Hg to the water seems to be the inflow from rivers and the sediment-water exchange.