Publication Summary

Semipermeable membrane devices were used to monitor chlorinated pesticides, PCBs, and PAHs in the Columbia River below Bonneville Dam during 2003-04. Washington and Oregon currently have 303(d) listings for the Lower Columbia for some of these compounds because of exceedances of human health criteria in fish tissue and/or the water column. The objectives of the study were to measure ambient concentrations, evaluate seasonal differences, and identify and rank sources of contamination to the river.

Semipermeable membrane devices were used to monitor chlorinated pesticides, polychlorinated biphenyls (PCBs), and polynuclear aromatic hydrocarbons (PAHs) in the Lower Columbia River below Bonneville Dam during 2003-2004. Washington and Oregon have placed the river on the federal Clean Water Act Section 303(d) list because fish and/or water samples have exceeded human health criteria for some of these compounds. Five mainstem sites and eight tributaries were monitored between Bonneville Dam and the Columbia River mouth to evaluate seasonal differences in contaminant levels and to identify and rank sources of contamination to the river.

Results showed that human health criteria were commonly exceeded for dieldrin and PCBs, less frequently exceeded for DDT compounds, and not exceeded for PAHs. The highest pesticide and PCB concentrations were generally found in the winter and spring, while PAHs were highest in the fall.

The major sources of DDT compounds and dieldrin were above Bonneville Dam. PCBs exceeded human health criteria at Bonneville Dam due to upstream sources, but there were additional important sources of PCBs below the dam. While PAHs did not exceed criteria, concentrations increased below Bonneville due to local sources. The Willamette River and Multnomah Channel were significant sources for all of these compounds. A screening-level loading assessment suggested there are other important PCB and PAH sources to the lower river that were not monitored in the study. Recommendations are made for follow-up studies and other actions.

Link to EIM data for User Study ID AJOH0041