Biogeochemical Controls on PCB Deposition in Hudson Bay (original) (raw)
Related papers
Chemosphere, 1994
Samples of water and suspended particulate matter were collected at two cross-sections of the St. Lawrence River and at the mouth of four of its tributaries regularly between March and November 1991, and analyzed for thirteen PCB congeners. Mean total PCB concentrations were similar in the St. Lawrence River and its tributaries at 1.33 ng/L The highest concentrations were observed in the spring with an important fraction of the contamination in the dissolved phase during the spring snowmelt must likely due to the accumulation of contaminated snow and atmospheric dry deposition during winter. For the rest of the year, the concentrations are lower and the PCBs are essentially transported by the suspended particulate matter. The PCB concentrations measured in the St. Lawrence River system seem to be more a residual signal than due to point sources.
PCBs in Great Lakes sediments, determined by positive matrix factorization
Lancet, 2011
Previously determined PCB concentrations in 10 dated sediment cores from Lakes Michigan, Huron, Erie, and Ontario are analyzed by positive matrix factorization in order to find characteristic congener patterns including signs of anaerobic dechlorination. Three or four factors are sufficient to describe the PCB data for each lake. All four lakes are dominated by Aroclors 1248A, 1248G, 1254A, and 1254G. Aroclor 1260 is only a significant factor in Lake Michigan prior to 1975, reflecting in part a usage patterns of heavy chlorinated Aroclors early and less chlorinated Aroclors in the phase-out years in the 1970s. Dated records of factors or sources indicate clear PCB concentration maxima for Lakes Erie (1981) and Ontario(1968), while redistribution of PCBs in the less contaminated Lakes Michigan and Huron has occurred after 1980. Using a single data matrix for all four lakes provides a common basis and possibility to examine low degrees of dechlorination, while individual data matrices for each lake provide more accurate results and better separation of factors. Lakes Ontario, Michigan, and Huron undergo dechlorination via reactions such as 66(24-34) → 25(24-3) and 18(25-2) → 4(2-2) consistent with reactions H' + M, while Lake Erie appears to be dominated by 18(25-2) → 4(2-2) and 53(25-26) → 19(26-2) that are typical for processes M + Q.
Journal of Great Lakes Research, 1997
PCB concentration and congener composition were examined in sediments and two species of macrophytes in the St. Lawrence River downstream of Cornwall, Ontario. Total PCBs in the macrophytes ranged from 37 to 585 ng/g dry weight, with biota to sediment accumulation factors ranging from 0.3 to 10. The floating-leaved species Nuphar variegatum had generally higher PCB concentrations than the submerged species Myriophyllum spicatum, but the latter had higher biota to sediment accumulation factors. N. variegatum also had a higher lipid content, but lipid levels were not a good predictor of plant PCB concentrations. Congener specific analysis showed congener patterns shifted between plants and sediments; macrophytes tended to have higher levels of tetrachlorobiphenyl congeners. Given that contaminant levels in plants reflect those found in the sediments, the high biomass of macrophytes within the river and particularly in Lake St. Francis represents an important reserve of PCBs which may be transferred to the herbivorous and detrital food webs.
Biogeochemical cycling of PCBs in lakes of variable trophic status: A paired-lake experiment
Limnology and Oceanography, 1999
A paired whole-lake experiment was conducted on two remote, atmospherically driven lakes in the Experimental Lakes Area (ELA) to examine the stresses of trophic condition on air-water exchange and settling fluxes of polychlorinated biphenyls (PCBs). Lake 227 (L227) and Lake 110 (L110) are similar in volume, surface area, and watershed area but differ significantly in trophic status. The two lakes have similar access to atmospheric PCBs but eutrophic L227 may exhibit enhanced air to water exchange due to greater biotic uptake of dissolved PCBs. Settling fluxes of PCB were significantly greater in eutrophic L227 (40 ng m Ϫ2 d Ϫ1 in 1993; 29 ng m Ϫ2 d Ϫ1 in 1994) than in oligotrophic L110 (22 ng m Ϫ2 d Ϫ1 in 1993 and 17 ng m Ϫ2 d Ϫ1 in 1994). Dissolved ⌺PCB concentrations were not significantly different in the two lakes (ϳ0.3 ng liter Ϫ1 ). Greater ⌺PCB settling fluxes in L227 vs. L110 coupled with similar dissolved concentrations after June supports the hypothesis that air-water exchange supports the water column PCB concentrations. Surprisingly, ⌺PCB fugacity gradients in both lakes indicated that net volatilization dominated during the entire ice-free period, requiring another source. A ⌺PCB mass budget in the epilimnion of each lake over the stratified period showed that the major PCB losses were due to settling and volatilization. ⌺PCB settling losses were 2.4 times greater in L227 than in L110 due to higher settling particle fluxes. The mass budgets suggest that the major PCB input to these remote lakes is from the watershed. Our results indicate the intimate environmental linkage between atmospheric, land, and aquatic PCB reservoirs.
PCB Decline in Settling Particles and Benthic Recycling of PCBs and PAHs in Lake Superior
Environmental Science & Technology, 1998
Sediment traps were deployed at fives sites in Lake Superior at multiple depths during lake stratification in 1987 and 1991. Mass, organic carbon, PCB, and PAH fluxes were determined. PCB concentrations on settling solids declined from 1984 to 1991 with a first-order rate constant of 0.26 yrâ»Â¹ similar to reported water column concentration decreases. Total PCB settling fluxes from the
Accumulation and recycling of PCBs and PAHs in artificially eutrophied Lake 227
Canadian Journal of Fisheries and Aquatic Sciences, 1999
The influence of lake trophic status on the cycling and burial of polychlorinated biphenyls (PCB's) and polycyclic aromatic hydrocarbons (PAH's) was examined in Lake 227 (L227), an artificially eutrophied lake in the Experimental Lakes Area, northwestern Ontario, Canada. Sedimentary accumulation of PCB's, PAH's, and organic carbon (OC) was determined pre-and post-eutrophication in L227 and compared with accumulation in other regional lakes. Mass and OC accumulation increased an average of 1.4 and 2.0 times, respectively, since nutrient addition began in June 1969. ΣPCB and ΣPAH sediment accumulation rates and profiles in L227 were similar to those in Lake Superior and other proximate and midlatitude lakes unimpacted by point sources. Eutrophication did not increase contaminant accumulation. In general, individual PAH accumulation rates declined following eutrophication, which coincided with similar signals elsewhere. Perylene declined markedly (4 times) since eutrophication as a result of decreased in situ formation. An increase in OC accumulation did not enhance contaminant accumulation in L227 because phytoplankton community structure shifted to species characterized by lower bioaccumulation factors, and water column recycling rates were high. Accumulation rates of mass, OC, PCB's, and PAH's, when compared with icefree settling fluxes in 1993 and 1994, exhibited similar recycling ratios in eutrophic L227 and oligotrophic L110 due to the efficient preservation of organic matter in sediments.
Historical Deposition of PCBs and Organochlorine Pesticides to Lake Winnipeg (Canada
Journal of Great Lakes Research, 2000
Two dated sediment cores; one taken from the north basin and one from the south basin of Lake Winnipeg (Manitoba, Canada) were analyzed for PCBs and organochlorine insecticides in order to examine the depositional history of these persistent organic pollutants (POPs). No previous work had been conducted on current or historical deposition of POPs in Lake Winnipeg sediments. Analysis by high resolution gas chromatography-electron capture detection showed elevated PCB concentrations in sediments dated to the late 1960s to early 1970s. Recent PCB fluxes were estimated to be 5 to 11 µg/m 2 /y in Lake Winnipeg sediments, with burdens of 388 and 337 µg/m 2 in the north and south basins, respectively. Loadings in the north basin sediment indicated atmospheric sources; south basin sediment reflected inputs from agricultural, industrial, and urban activities. DDT inventories were 37 and 127 µg/m 2 in the north and south basin cores, respectively. DDD contributed the largest amount to DDT in sediments, corresponding to anaerobic degradation of the parent molecule. Maximum hexachlorocyclohexane (HCH) concentrations were observed in recent slices of both sediment cores and fluxes ranged from 177 to 914 ng/m 2 /y. There was evidence for recent increases in lindane deposition. Subsurface maximum concentrations were observed for total chlordane (ΣCHL), pentachloroanisole (PCA), and total chlorobenzenes (ΣCBz) in the south basin. ΣCHL, PCA, and ΣCBz, however, were present at maximum concentrations in the surface slice in sediment from the north basin.
Progress in Oceanography, 2013
The Strait of Georgia is a large, deep, fjord-like estuary on the southern coast of British Columbia which is subject to local and atmospheric inputs of persistent environmental contaminants. We measured 204 polychlorinated biphenyls (PCBs) and 61 polybrominated diphenyl ethers (PBDEs) seasonally in water (two depths; dissolved and particle-bound) and plankton (vertical tow) samples collected at two stations. Principal components analysis clearly distinguished the dissolved and particulate water fractions and plankton samples, with the latter two compartments associated more with heavier congeners. Bioaccumulation factors (log BAFs) for PCBs and PBDEs in plankton were best described by parabolic relationships against octanol-water partitioning coefficients (log K ow ), peaking at a log K ow of 5-7, underscoring the important role of physico-chemical properties in driving the uptake of these persistent contaminants by plankton from water. The estimated total quantity of PCBs (annual average of 0.61 ± SEM 0.12 kg) and PBDEs (annual average of 0.64 ± 0.19 kg) in Strait of Georgia plankton biomass were remarkably similar, highlighting the emergence of currently-used PBDEs as a priority concern. The estimated total of 52.1 ± 8.41 kg of PCBs in water (dissolved + particle-bound) was higher than the estimated 26.8 ± 5.20 kg of PBDEs (dissolved + particle-bound), reflecting the dichotomous use histories for these two contaminant classes. Results provide insight into the biological availability of PCBs and PBDEs to the Strait of Georgia food web, and describe an important initial partitioning process by which the region's endangered killer whales have become highly contaminated.