Spatial Trends and Historical Deposition of Polychlorinated Biphenyls in Canadian Midlatitude and Arctic Lake Sediments

Abstract

A study of PCB concentrations and fluxes in lake sediments was conducted to test the “global fractionation” hypothesis that deposition of semivolatile organics will decline while more volatile congeners will be enriched in polar regions. Sediment cores were collected from 11 remote lakes in Canada ranging from 49° N to 82° N and were dated using excess 210Pb and 137Cs. Sediment extracts were analyzed for up to 90 PCB congeners by capillary GC-ECD with confirmation by GC/high-resolution MS. Total PCB (∑PCB) concentrations in surface slices ranged from 2.4 to 39 ng g-1 (dry wt) and showed no latitudinal trend. Fluxes (ng m-2 yr-1) and inventories of ∑PCB as well as total tetra- to octachlorobiphenyls declined with increasing north latitude while those for di/trichlorobiphenyls showed no latitudinal trend. The proportion of di/trichloro congeners of ∑PCB also increased significantly with latitude, while total octachlorobiphenyls declined. Maximum ∑PCB concentrations were observed in subsurface slices dating to the 1960−1970s in most lakes except those in the high Arctic, where maxima were generally in surface slices. The onset of elevated ∑PCB deposition was delayed in the high Arctic (1950−1960s) relative to the midlatitude and sub-Arctic lakes (1930−1940s). The high proportions of lower chlorinated congeners and the delayed appearance of PCBs are consistent with predictions of the global fractionation model.

Bathymetry and Sediment Geochemistry of Lake Hazen (Quttinirpaaq National Park, Ellesmere Island, Nunavut)

“…The precision of the bathymetric map of Lake Hazen will be increased in the future by adding more spots, particularly along the shoreline and at the far ends of the lake. The volume of the lake based on our bathymetric interpolation is approximately 5.14 × 10 10 m 3 and the mean depth is 95 m; both figures are about 10% larger than previous estimates by Muir et al (1996) based on data in the Deane (1959) report.…”

“…Deane (1959:62), on the basis of 62 echo sounding traverses in 1958, suggested a maximum depth for the lake of 263 m and noted that the "main part of the lake shows a shallow, asymmetrical, U-shaped depression, with the deepest part about half-way between the centre of the lake and the north shore." Muir et al (1996), using the data from Deane's work, reported a maximum depth of 263 m, mean depth of 85 m, and approximate lake volume of 4.55 × 10 10 m 3 . Sediment coring in 1990 at a site northeast of Johns Island in the deep zone identified by Deane (1959) was conducted to a maximum depth of 254 m (G. Brunskill, Australian Institute of Marine Science, Townsville, Queensland, pers.…”

“…Results on sedimentation rate and mercury concentrations and fluxes were subsequently published (Lockhart et al, 1998). Sediment core profiles of polyaromatic hydrocarbons (Lockhart et al, 1992) and PCBs (Muir et al, 1996) have also been reported. Outridge et al (2002) unpubl.…”

Distributions of polychlorinated biphenyls in the Daliao River estuary of Liaodong Bay, Bohai Sea (China)

“…However, site 1 concentrations happen to be largely dominated by 8CBs. Evidence suggests that more highly chlorinated PCB congeners commonly accumulate near the source of PCBs (Ashley and Baker, 1999;de Mora et al, 2005;Hong et al, 2005), whereas less chlorinated PCB congeners may be transported over longer distances (Muir et al, 1996). This may be a possible explanation to the problem.…”

Global Distillation in an Era of Climate Change

“…Polychlorinated biphenyls (PCB) have been amongst the most heavily studied of pollutants in this regard and reports of PCB migration include those in Northern Hemisphere soils (Meijer, et al, 2002), European high mountain lakes (Carera et al, 2002) levels observed in Norwegian mosses (Lead et al, 1996), deposition patterns in Canadian lakes (Muir et al, 1996) and Russian Lakes (McConnell et al, 1996). Studies universally point to enhanced retention of the more chlorinated PCB congeners at lower latitudes, probably reflecting a more facile volatilization of the simpler PCBs and their subsequent migration to the poles.…”