Publication Summary

The Washington State Department of Ecology monitored contaminants in Lake Roosevelt during 1992 as part of a two-year study to document the impact of pollution controls being implemented upstream in Canada. Contaminants monitored were 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; commonly referred to as dioxin), 2,3,7,8-tetrachlorodibenzofuran (TCDF), and metals (zinc, lead, copper, arsenic, cadmium, and mercury).

The Washington State Department of Ecology monitored contaminants in Lake Roosevelt during 1992 as part of a two-year study to document the impact of pollution controls being implemented upstream in Canada. Contaminants monitored were 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; commonly referred to as dioxin), 2,3,7,8-tetrachlorodibenzofuran (TCDF), and metals (zinc, lead, copper, arsenic, cadmium, and mercury).

The major source of TCDD/TCDF is the Celgar pulp mill in Castlegar, B.C. The Cominco lead-zinc smelter in Trail, B.C., is the major source of metals contamination. Columbia River suspended particulate matter (particulates) was collected near the international border over a three-day period and analyzed for TCDD, TCDF, and metals. Lake whitefish (Coregonus clupeaformis) were collected from Lake Roosevelt near Kettle Falls and analyzed for TCDD/TCDF in muscle tissue and eggs. Liver tissues from largescale suckers (Catostomus macrocheilus) collected near the border were analyzed for metals. Activities of delta-aminolevulinic acid dehydratase (ALAD), a blood enzyme inhibited by lead exposure, were measured in largescale sucker blood to determine if this species exhibited a physiological response to ambient lead concentrations. TCDD and TCDF data were compared to results from similar surveys of Lake Roosevelt conducted by Ecology during 1990. The metals data will be used as a baseline for future trend monitoring efforts. Columbia River particulates showed a substantial decrease in TCDF from 1990 (6.2 vs. 99 pg/g or parts per trillion). TCDD was not detected in particulates during either year.

Estimated loads of TCDF entering Lake Roosevelt dropped from 30 mg/day in 1990 to 2.1 mg/day in 1992. The reduction in TCDF loads appear to be consistent with recent mill modifications at Celgar designed to reduce dioxin and furan discharge to the Columbia River. TCDD and TCDF residues in lake whitefish muscle were significantly lower in 1992 compared to 1990. Mean TCDD and TCDF concentrations in 1992 were 0.8 and 62 pg/g, respectively, down from 1.9 and 126 pg/g in 1990. Concentrations of TCDD and TCDF residues in whitefish eggs decreased by an order of magnitude from 1990 to 1992. Metals in particulates were comparable to bottom sediments from depositional areas in Lake Roosevelt, suggesting that discharges from Cominco continue to represent a metals problem to the lake.

Loading estimates for particulate-bound metals to Lake Roosevelt were generally within ranges discharged through Cominco's sewers. Concentrations of cadmium, lead, and zinc in sucker livers were significantly higher in the Columbia River at Northport compared to fish from Lake Wenatchee, an uncontaminated reference lake. Mean zinc and copper concentrations from the same two groups were similar. ALA-D activity was significantly higher in Lake Wenatchee suckers compared to Northport suckers. Inhibition of ALA-D, however, did not result in depressed hemoglobin levels.

Recommendations were to continue monitoring TCDD and TCDF in a manner similar to the one described here. Metals monitoring should also continue, but with modifications to the fish tissue component.

Link to EIM data for User Study ID DSER0012