Among the guiding questions of the Northern River Basins Study, questions 4 and 11 ask about the nature and contents of the contaminants entering the system and about their effects on riparian wildlife, respectively. This report examines these questions by focusing on contaminants in one riparian species, the Common Merganser.
In early August, 1992, pre-fledged Common Mergansers were collected upstream and downstream from the Weyerhaeuser Canada pulp mill (formerly Proctor and Gamble) on the Wapiti River, near Grande Prairie, Alberta. Four birds were collected upstream from the mill and six were collected downstream from the mill. Analyses of dioxins and furans and chlorinated phenolics were made on pooled liver homogenates (n=l for both the upstream and downstream sites). Organochlorine insecticides, PCBs and metals were analyzed in liver or kidney tissue on an individual basis.
In general, few contaminants were detected. Those that were, were found at very low concentrations. Some chlorinated phenolics were detected in the downstream pool but not in the upstream pool while 2378-tetrachlorodibenzofuran (TCDF) occurred at higher levels in the downstream pool than in the upstream pool, suggesting a pulp mill effect. However, the concentration of 2378-TCDF in the downstream pool was less than 10% of that in Common Mergansers downstream from a pulp mill on the St. Maurice River in Quebec. PCBs, organochlorine insecticides and metals did not differ between sites. Vitamin A as retinol and retinyl palmitate were lower in livers of downstream mergansers than in those of upstream ones. One explanation for this is the greater exposure of the downstream mergansers to contaminants such as 2378-TCDF, a member of a class of contaminants known to be associated with reduced stores of vitamin A.