Persistent chemicals in the northern Baltic
The 'Atmospheric exchange of persistent chemicals in Bothnian Bay, northern Baltic Sea' (BAYEX) project investigated organochlorine pesticides (OCPs), current-use pesticides (CUPs), and some naturally occurring organobromine compounds in air and water. Substances such as OCPs, CUPs and organobromine have been shown to undergo long-range transport and deposition in the Arctic. BAYEX consortium members measured loadings to Bothnian Bay, in northern Sweden, which were affected by seasonal changes to concentrations in air, water, temperature, ice cover and primary productivity. The results were used to determine monitoring regimes and process studies, leading to predictions of climate-induced effects on future loadings. Air and surface water samples were analysed for target compounds, of which all were found except for the CUPs trifluralin and chlorothanil — these could not be measured due to chromatographic interferences. Levels found by researchers ranged between those identified in the Arctic Ocean and the North American Great Lakes. Results for air agreed well with measurements taken at the European Monitoring and Evaluation Programme (EMEP) monitoring stations based on the west coast of Sweden and in arctic Finland. Results indicated that bulk deposition (comprising precipitation plus dry particle deposition) to the catchment followed by river runoff could be a significant pathway for toxic chemicals entering Bothnian Bay. A computer simulation was also conducted involving a 2–3 degrees Celsius temperature rise and the resulting loss of ice cover. The simulation predicted a 50–60 % increase in deposition and volatilisation loadings to Bothnian Bay for most compounds, largely due to a longer open-water season. BAYEX provided the first measurements of OCPs and natural organobromine in the air and water of the northern Baltic, and investigated the exchange processes that link them. The information gained through the work of BAYEX will enable EU and Swedish scientists to make atmospheric deposition estimates for these substances and determine how they are affected by changing ice cover and air concentrations.
