The impact of salt water inflows on the distribution of polycyclic aromatic hydrocarbons in the deep water of the Baltic Sea

Salt-water inflows into the Baltic Sea are important events for renewing th e deep and bottom waters of the deep basins of the Baltic Sea. These events occur only at irregular intervals. The last strong event was in January 19 93 followed by minor inflows in winter 1993/1994. As a result of these infl ows, the deep water of the central Baltic basins was completely renewed. Based on extensive observations of polycyclic aromatic hydrocarbons (PAHs) in water, fluffy layer material and surface sediments between 1992 and 1998 , the transformation of PAHs and the modification of their distribution in the Baltic deep water is discussed in connection with the spreading of the inflowing highly saline and oxygen-rich water along its pathway from the si lls into the central basins. In the course of the inflows in 1993/1994, the PAH concentration in the deep water of the different basins increased sign ificantly. The concentrations were elevated, at least by a factor of 2 and as much as seven to eight times (for the four-ring PAHs) compared to the pr evious and the following years. Two hypotheses for the causes were discusse d: the inflowing salt water may have entrained more highly polluted surface water in the western Baltic Sea, or it may have entrained contaminated flu ffy layer material or sediment particles along the route of transport. (C) 2001 Elsevier Science B.V. All rights reserved.