Summary and Conclusions


Toxic contamination is a significant concern in the Columbia River Basin. Many efforts and dollars are focused on restoring critical habitat for endangered salmonids and other wildlife that depend on the ecosystem; however, although physical habitat is a prime consideration in restoration decisions, water-quality concerns, specifically contamination issues, also can influence these decisions. Toxics-reduction efforts are underway to protect the health of people, aquatic life, and the ecosystem. 


To successfully reduce toxics and restore critical habitat, an understanding of the sources of contaminants is necessary. This study was designed to take a first look at two easily defined pathways that deliver contaminants to the Columbia River, wastewater-treatment-plant (WWTP) effluent and stormwater runoff. The resulting data can be used to assess the types, number, and magnitude of compounds present and to lay the foundation for additional studies and potential toxics‑reduction activities. 


Nine cities were selected from throughout the Columbia River Basin to provide diversity in physical setting, climate characteristics, and population density. In downstream order, the cities sampled were Wenatchee, Richland, Umatilla, The Dalles, Hood River, Portland, Vancouver, St. Helens, and Longview throughout Washington and Oregon. These cities also were selected because their WWTP effluent and at least some part of their stormwater (except Umatilla) is delivered directly to the Columbia River. Most samples at the WWTPs were collected in December 2008 for anthropogenic organic compounds (AOCs), pharmaceuticals, estrogenicity, and halogenated compounds. In December 2009, each of these WWTPs was revisited to collect samples for the analysis of currently used pesticides, mercury, and methylmercury. Stormwater samples were collected throughout spring and winter storms of 2009 and 2010 from these cities as well as additional sites along the lower Willamette River near downtown Portland. These samples were analyzed for currently used pesticides, halogenated compounds, mercury, polycyclic aromatic hydrocarbons (PAHs), trace elements, and oil and grease. 


WWTP effluents—Flame retardants (polybrominated diphenyl ethers [PBDEs] and others) and steroids were consistently detected in WWTP-effluent samples, whereas few pesticides or PAHs were detected, except at Longview. Concentrations of PBDEs were detected at all sites, and the highest concentrations detected were for congeners PBDE‑47, PBDE-99, and PBDE-100. No PCBs were detected at most WWTPs, except Wenatchee. Longview also was notable because it had the greatest number of detections and the concentrations were usually among the highest, particularly for the personal-care-product compounds. Fourteen human‑health pharmaceuticals were analyzed for and all but albuterol and warfarin were detected in at least one city. Two pharmaceuticals were detected at all of the W sampled, carbamazepine and diphenhydramine. The yeast estrogen screen, an assay that measures the potential biological effects of the mixture of chemicals present in a sample, was used to screen each sample for total estrogenicity. The estrogenicity levels measured in this study were well above levels that have been shown to cause effects in aquatic biota.


Few currently used pesticides were detected in WWTP‑effluent samples. The primary compounds detected were fipronil and its degradates, which were in samples collected from all WWTPs except Wenatchee. Fipronil is an insecticide used to control common household pests like ants, beetles, cockroaches, and other insects, and can be in topical pet-care products used to control fleas. The highest total mercury concentrations were measured at The Dalles and Vancouver. Both of these concentrations were greater than 12 ng/L, the chronic criterion for freshwater aquatic life.


Stormwater-runoff—Diverse sources of stormwater runoff and the larger amount of suspended sediment present in these samples relative to that in WWTP-effluent samples resulted in very different results for the stormwater-runoff samples. Additionally, localized sources contributed to the detection patterns observed in these samples. Of the 49 halogenated compounds detected in stormwater-runoff samples, 45 were detected in the Willamette2-Dec sample, which is within the Portland Harbor Superfund area. The PBDE concentrations at Willamette2 were roughly double those in the Umatilla sample and the PCB concentrations at Willamette2 were 20–300 times greater than PCB concentrations in any other stormwater-runoff samples. Herbicide and insecticide detections in solids filtered from stormwater runoff also follow a pattern of high contaminant concentrations in samples with high suspended-sediment concentrations—particularly from Umatilla, Vancouver, and Willamette2. Detections for several pesticides and PCBs from the Willamette2 site in December and May exceeded chronic freshwater-quality criteria. Although many of these concentrations are low (less than 1 microgram per liter), mixtures of some of these pesticides have been determined to have synergistic and additive effects on salmon health when they occur together.


The 10 trace elements measured in filtered and unfiltered stormwater runoff in this study were detected consistently through all samples. Arsenic, cadmium, copper, nickel, selenium, and zinc tended to transport more readily in the dissolved phase, whereas chromium, lead, mercury, and silver were more often detected in the solid phase. Chronic and sometimes acute freshwater-quality criteria for cadmium, copper, lead, and zinc were all exceeded in several stormwater-runoff samples. These concentrations, particularly for copper, chromium, and zinc, also were potentially high enough to cause health effects in aquatic biota. The Willamette stormwater-runoff sites in the Portland Harbor area, as well as Vancouver2, had concentrations of total mercury greater than or equal to the chronic criterion for freshwater aquatic life (12 ng/L).


Implications for the Columbia River Basin—Instantaneous loadings were calculated for four compounds detected in WWTP-effluent samples—diphenhydramine, trimethoprim, Galaxolide, and nonylphenol compounds—to estimate the potential contribution to the Columbia River from the studied WWTPs. The instantaneous loads for the Portland WWTP were consistently much greater than for any other plant because the effluent discharge from the Portland WWTP is much greater than for any other plant, discharging five times more than the next largest WWTP, in The Dalles. The resulting concentrations in the Columbia River from these contributions were calculated. Most of these concentrations were small and would not be detectable using standard sampling techniques. These calculations illustrate that the Columbia River is able to “absorb” a variety of inputs because of its ability to dilute. Nonetheless, although the calculated concentrations are small in the context of the entire river, the local effect of these continuous inputs in the mixing zone is understudied. The aquatic biota inhabiting these areas may be exposed to higher concentrations than in other areas.


Comparison to Oregon Senate Bill (SB) 737—As part of the SB 737 process to identify persistent pollutants and reduce concentrations entering Oregon’s waterways, the Oregon Department of Environmental Quality (ODEQ) was tasked with developing a list of persistent pollutants that have a documented effect on human health, wildlife, and aquatic life. The 52 largest WWTPs in Oregon sent samples to the ODEQ laboratory to be analyzed for these pollutants, and the results were compared to plan initiation levels (PILs) developed to decide when action is required to reduce the presence of these pollutants in the effluents. Only four compounds analyzed for in this study—fluoranthene, anthracene, cholesterol, and coprostanol—exceeded the corresponding PILs. Many of the AOCs and pharmaceuticals analyzed in WWTP-effluent samples collected during this study were detected; however, these samples contained only 27 of the 42 compounds on the SB 737 persistent pollutants list that were analyzed for in this study. The reason for this dichotomy is that many of the contaminants on the persistent pollutant list are PAHs, metals, and currently used pesticides—all compounds that are likely to be detected in stormwater but not necessarily wastewater.


Future directions—This study was intended to serve as a precursor for future work. The study results show that WWTP effluent contains a wide variety of contaminants from many compound classes. Given the variety of factors influencing the composition of the effluent, it would be difficult to design a study to explain the expected results for WWTP effluent. It is preferable to consider this pathway simply as an integrator of human activity and focus on minimizing the effects it has on the ecosystem. Seasonality was not addressed in this study design. The large number of hydrophobic compounds that were detected in these effluents indicates that the biosolids from these WWTPs may be potentially significant sources of these contaminants to the ecosystem.


Stormwater runoff acts as an integrator of human activities and can be a source of various compounds to aquatic ecosystems. The inputs from stormwater runoff are more sporadic than the continual input of WWTP effluents, but their potentially large contributions during short periods can still have an effect on biota that inhabit mixing zones in the receiving waters. Toxics-reduction efforts will be more effective when contaminant occurrence and distribution data are coupled with land-use information from the stormwater catchments that drain to the Columbia River.


Data from this study and others like it can provide a useful framework for directing future work on identifying and reducing contaminant concentrations in the Columbia River Basin. Wastewater-treatment plant effluent and stormwater runoff are two pathways for contaminants to reach the receiving waters, but there are other understudied pathways. The results from this study provide a starting point for future work to continue understanding the presence of contaminants in the environment, develop research to characterize the effects of these contaminants on aquatic life, and prioritize future toxic-reduction efforts. 


First posted April 25, 2012