Distribution of Organochlorine Pesticide and Polychlorinated Biphenyl Residues in Lake Sediment Cores from the Plitvice Lakes National Park (Croatia).

The occurrence and distribution of 11 organochlorine pesticides (OCPs) and their degradation products as well as of 17 polychlorinated biphenyl congeners (PCBs) were investigated for the first time in sediments of three (Lake Prošće, Lake Kozjak, Lake Kaluđerovac) out of 16 cascading karst lakes within the protected area of the Plitvice Lakes National Park in central Croatia. The 15-cm-long sediment cores were divided for analysis into three 5-cm-long segments. The abundance and levels of sediment-associated OCPs and PCBs were evaluated with respect to sampling location and sediment depth, presumed age of deposition, and organic carbon content. The burden of sediments with OCPs and PCBs decreased downstream with the highest mass fractions measured in the uppermost Lake Prošće (total OCPs 2.72-5.86 μg kg d.m., total PCBs 0.37-1.78 µg kg d.m.) and the lowest in Lake Kaluđerovac (total OCPs 0.30-0.58 μg kg d.m., total PCBs 0.07-0.12 µg kg d.m.). The predominant organochlorine pollutants were DDT-type compounds (total DDX, w = 0.30-5.72 µg kg d.m.) with p,p'-DDE and p,p'-DDD accounting for up to 100% and 50%, respectively, of the total DDX. The findings indicated an old input of p,p'-DDT that largely converted to its degradation products. The OCP and PCB mass fractions in the Plitvice lake sediments were at trace levels characteristic for preserved pristine natural environments with no or limited anthropogenic impact wherein long-range atmospheric transport is considered as their main source.