Occurrence of C10−C13 Polychlorinated n-Alkanes in Canadian Midlatitude and Arctic Lake Sediments

Sediment cores from six lakes in Canada ranging from 49°N to 81°N were analyzed for C10−C13 polychlorinated n-alkanes (PCAs) with the intent of (i) examining the depositional trends with increasing latitude, (ii) studying the historical profiles and fluxes of PCAs in dated sediment slices, and (iii) investigating possible in situ degradation. Sediment slices were dated using 210Pb and 137Cs, and extracts were analyzed for PCA concentrations by high resolution gas chromatography electron capture negative ion high resolution mass spectrometry (HRGC-ECNI/HRMS) in the selected ion monitoring (SIM) mode. Concentrations of total PCAs in surface sediments declined significantly from 135 ng/g (dry weight (dw)) in sediments from the southern basin of Lake Winnipeg (50°N/96°W, Manitoba) to 4.52 ng/g in Hazen Lake (81°N/71°W, high Arctic); corresponding surficial fluxes were 147 and 0.9 μg/m2 yr, respectively. The high flux of PCAs to the south Lake Winnipeg basin suggests local contamination. This was confirmed by ...