Contributors (in alphabetical order)
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DioxinsTotal dioxins were detected in two of the four samples analyzed, with their concentration ranging from 0.69 to 1.00 ppt (parts per trillion) at an analytical detection limit of 0.4 ppt. The two samples having detectable concentrations of total dioxins were collected from sampling stations LGR 8-3 (0.69 ppt) and LGR 13-7 (1.00 ppt), which are located in the upper portion of Lower Granite Lake. These concentrations are within the lower range of concentrations identified in studies of the Lower Columbia River and the lower Willamette River (Bi-State Study and 1990 Portland Army Corps of Engineers Survey) (Corps 1998c). In Lower Granite Lake the total dioxin concentrations decrease from upstream to downstream, with no detectable concentrations of total dioxins identified in the samples collected from stations LGR 5-8 and LGR 6-4. The trend of decreasing total dioxins concentrations with increasing distance downstream would suggest that the source(s) for these organic compounds is located upstream of the study area. GlyphosateGlyphosate (N-(phosphonomethyl)glycine) is a postemergence herbicide that has found widespread agricultural and domestic use. It is sold as a terrestrial and aquatic herbicide. A major metabolite of Glyphosate is aminomethylphosphonic acid (AMPA). All top layer sediment samples (94 total samples) were tested for glyphosate and AMPA. Glyphosate was detected in 36% of the samples and AMPA was detected in 16% of the samples tested. The concentration of glyphosate ranged from non-detected to a maximum of 68.9 ppb (parts per billion) with an arithmetic mean of 12.52 ppb. The concentration of AMPA ranged from non-detected to a maximum of 29.3 ppb with and arithmetic mean of 7.48 ppb (Normandeau 1999b). No screening criteria have been established for either glyphosate or AMPA in sediments within the Columbia River Basin. Glyphosate and AMPA were detected in sediment samples collected from each of the impoundments. The highest individual concentrations of glyphosate and AMPA were detected in samples collected from Lake Bryan (upstream of the Little Goose Dam) (Normandeau 1999b). The highest average reach concentration of glyphosate was found in the samples collected from Lake Sacajawea (Table 17). Table 17. Summary of average glyphosate and AMPA concentrations (μg/L, Elutriate, and ppb, Sediment) For sediment samples collected during 1997 in the Lower Snake River (Corps 1999).
The highest average reach concentration of AMPA was found in the samples collected from Lake West (upstream of Lower Monumental Dam). The suspected source of glyphosate and AMPA in the Lower Snake River sediments is runoff from surrounding uplands and through transport via stream flow. Sources for these organic compounds may include agricultural, industrial, municipal or domestic uses within the watershed. Organochlorine PesticidesSeveral organochlorine pesticides were detected in the sediment samples collected from the Lower Snake River. The organochlorine pesticide compounds detected (and their frequency of detection) included, 4,4-DDD (11), 4,4-DDE (43), 4,4-DDT (5), aldrin (3), dieldrin (4), endrin (1), heptachlor (1) and lindane (3) (Normandeau 1999b, Table 18). The three principal organochlorine pesticide compounds detected in the sediments are related, with DDT being the parent compound and DDD-DDE being daughter products generated by the transformation of DDT in the environment (Callahan et al. 1979). The predominant organochlorine compound detected was DDE, which ranged in average concentration from 2.68 in Ice Harbor to 6.48 in Lower Granite Reach, with an arithmetic mean concentration of 4.89 ppb. DDD was detected in 11 sediment samples with an average maximum concentration of 6.48 ppb in Lower Granite Reach and an arithmetic mean of 2.07 ppb. DDT was detected in only five samples with a mean arithmetic concentration of 1.62 ppb. Table 18. Summary of Average Concentrations (ppb) of Organochlorine Pesticides and TPH in Sediments Collected during 1997 in the Lower Snake River (Corps 1999).
Total DDT (DDD, DDE and DDT) concentrations ranged from non-detect to 32.8 ppb with an average concentration of 8.23 ppb (Normandeau 1999b). The highest mean reach concentration for total DDT was 11.3 ppb for Lower Granite Lake. The average reach concentration of total DDT decreases steadily from Lower Granite Lake down to 5.7 ppb as recorded in Lake Sacajawea. The maximum and average total DDT concentrations in the Lower Snake River sediments exceed the guidance levels set forth in "Puget Sound Dredged Disposal Analysis Guidance Manual: Data Quality Evaluation for Proposed Dredged Material Disposal Projects" (PTI 1989a) or recommended screening concentration (6.9 ppb), but are lower than the bioaccumulation trigger concentration of 50 ppb as established in the Dredged Material Evaluation Framework (DMEF) (Corps 1998c). Concentration levels above the screening level prompt biological testing to ascertain health risks to aquatic organisms using the DMEF (Corps 1998c). The pesticides aldrin, dieldrin, endrin, heptachlor and lindane were all detected in five or less of the 94 sediment samples. The concentration of aldrin ranged from non-detect to 3.5 ppb, dieldrin from non-detect to 8.0 ppb, endrin from non-detect to 9.4 ppb, heptachlor from non-detect to 4.9 ppb and lindane from non-detect to 5.5 ppb (Normandeau 1999b). The maximum concentrations of aldrin, dieldrin, heptachlor, and lindane in the Snake River sediment are lower than their screening level concentration of 10 ppb. No screening level has been established for endrin in the DMEF (Corps 1998c). A recent report by the USGS (Clark and Maret 1998) documents the results of the collection and analysis of bed sediments from the Snake River upstream of the study area. The only organochlorine compound detected in all of the bed sediment samples analyzed by the USGS was DDE at concentrations ranging from 1 to 11 ppb. These concentrations are similar to those reported for the sediment samples analyzed for this investigation. Reports of previous investigations performed on the lower Columbia River (Bi-State Study and Portland Corps 1997 Survey) also document that pesticides are typically only detected at low concentrations (Corps 1998c). A modified version of EPA Method 418.1 was used for the analysis of the sediments to determine the concentration of petroleum products. Use of this analytical method only provides an indication of the amount of petroleum material in the sediments but does not quantitatively identify the specific type of petroleum material present. The concentration of TPH ranged from non-detect to 256 ppm (LM 1-2) with an arithmetic mean of 55.41 ppm (Normandeau 1999b). Along the Lower Snake River, the average concentration of TPH generally increases in the downstream direction with the highest average reach concentration (62.13 ppm) found in Lake Sacajawea. No screening level has been established for TPH under the DMEF (Corps 1998c). | ||||||||||||||||||||||||||||||||||||||||||||||||||||||