Differentiation of polychlorinated dibenzo-p-dioxin and dibenzofuran sources in coastal British Columbia, Canada

Multivariate pattern analysis techniques, principal components analysis, and polytopic vector analysis (PVA) were used to apportion sources of dioxins and furans to Howe Sound and the lower Strait of Georgia marine ecosystem, British Columbia, Canada, based on deposition in recent sediments. In sediment cores collected in 1990, differences between congeners in the depth of maximum concentration suggested the influence over time of several different sources. Those with a predominance of hexachlorinated dibenzodioxins and 2,3,7,8-tetrachlorodibenzofuran comprised one of the major contributions to the sediment core samples and surficial samples collected from Howe Sound, consistent with past inputs of pulpmill effluent. For most sediment samples, however, over 50% of the composition was attributable to a separate source with octachlorodibenzo-p-dioxin (OCDD) as the dominant congener, followed by heptachlorodibenzo-p-dioxins with small amounts of heprachlorodibenzofuran and octachlorodibenzofuran (OCDF). This source signature is consistent with the composition of dioxins/furans in formulations of pentachlorophenol-based wood preservatives, which were used extensively in British Columbia, Canada prior to the mid-1980s. This major input signature to the greater Strait of Georgia cannot be unequivocally ascribed to PCP use and disposal, however, since several other dioxin/furan sources also exhibit a highly similar composition, one dominated by OCDD. For example, source signatures similar to PCP formulations include those from diesel emissions, coal combustion, municipal solid waste, or other incineration stack emissions (fly ash, in particular), chimney soot from oil central heating, black-liquor recovery furnace flue gas, and scrap wire and car incineration. Further research is required to discriminate among the OCDD-containing sources and, hence, provide for improved future source management.