Contaminant Mass Balance for Sinclair and Dyes Inlets, Puget Sound, WA

Sinclair Inlet and Dyes Inlets have historically received contaminates from military installations, industrial activities, municipal outfalls, and other nonpoint sources. For the purpose of determining a ?total maximum daily load? (TMDL) of contaminants for the Inlets, a contaminant mass balance for the sediments is being developed. Sediment cores and traps were collected from depositional areas of the Inlets and surface sediment grabs were collected from fluvial deposits associated with major drainage areas into the Inlets. All sediment samples were screened using X-Ray fluorescence (XRF) for metals, UV fluorescence for organics (PAHs), and immunoassay for PCBs. A subset of split-samples was analyzed using ICP/MS for metals and GC/MS for phthalates, PAHs, and PCBs. Sediment cores were age-dated using radionuclides to determine the sedimentation rate and the history of sediment contamination. Streams and storm water outfalls were sampled in both the wet and dry seasons to assess loading from the watershed. Seawater samples collected from the marine waters of the Inlets and boundary passages to central Puget Sound were used to estimate the exchange of contaminates with central Puget Sound. The historical trends from the cores indicate that contamination was at a maximum in the middle of the 1900s and decreased significantlymore » by the late 1900s. The thickness of the contaminated sediment is in the range of 30 to 50 cm.« less