Concentrations and spatial distribution of chlordanes and some other cyclodiene pesticides in Baltic plankton

Twelve chlordane (CHLs) components and their metabolites (heptachlor, heptachlor epoxide, U82, MC4, trans-chlordane, MC5, cis-chlordane, MC7, oxychlordane, MC6, trans- and cis-nonachlor) and aldrin, dieldrin, endrin, isodrin, endosulfan 1, endosulfan 2, and mirex were quantified in mixed subsurface phyto- and zooplankton collected at four spatially distant sites in the southern part of the Baltic Sea. The CHLs concentrations in plankton were low, i.e. 5.3, 8.7, 9.2 and 8.7 ng/g lipid in Gdańsk Depth, Gotland Basin, Bornholm Basin and Pomeranian Bay, respectively. Chlordane compounds showed similar distributions and patterns in plankton at all four sampling sites. The trans-nonachlor to cis-chlordane ratio (N:C ratio) in plankton was between 0.76 and 1.0 which clearly indicates pollution from distant sources due to long-range aerial transport. The relatively high concentrations of heptachlor epoxide seem to be related to local sources of pollution around of the Baltic Sea. Dieldrin was the major cyclodiene pesticide quantified and its concentration was uniformly distributed in the plankton sampled and ranged from 23 to 42 ng/g lipid, while aldrin, endrin, isodrin, endosulfan 1, endosulfan 2 and mirex were undetected.