Levels of PCDD, PCDF and PCB in dated lake sediments in Subarctic Finland

Dated sediment cores from three small subarctic headwater lakes from Lapland, the Northern part of Finland, were analyzed for PCDD/F and PCB. The sedimentation rates in the lakes were slow, at the top layers 0.5–1.5 mm year−1. The levels of the sum of PCB at the top layers were 2.95, 5.6, and 3.6 ng/g d.w. and decreased below the detection limits (<0.01 ng PCB congener/g d.w.) in 1940ʹs or 1920ʹs. PCDD/F profiles were highly similar to the profiles of PCB. Also, the concentrations of PCDD/F were low; at the top layers the sums of PCDD/F were 275, 98, and 233 pg/g d.w. corresponding to the toxic equivalents of 4.22, 1.43, and 4.07 pg I-TEQ/g d.w. and decreased below 20 pg/g with increasing depth, corresponding to about 0.90 pg I-TEQ/g d.w. Estimates for present fluxes for the sum of PCB vary between 50 and 200 ng m−2 year−1 and for PCDD/F between 4 and 25 ng m−2 year−1. The numbers are low, but the pattern of the accumulation history shows that the increase of the non-natural organic contaminants in remote areas is clearly detectable and, at least, partly quantifiable. The study belongs to the Arctic Monitoring and Assessment Program (AMAP), which is one part of the Arctic Environmental Protection Strategy, signed by all eight Arctic countries.