Presentation on theme: "Concentrations and loads of PCBs and OC pesticides in the Guadalupe River watershed Jon Leatherbarrow 1,2, Lester McKee 1, John Oram 1 1 San Francisco."— Presentation transcript:
Concentrations and loads of PCBs and OC pesticides in the Guadalupe River watershed Jon Leatherbarrow 1,2, Lester McKee 1, John Oram 1 1 San Francisco Estuary Institute, Oakland, CA 2 UC Davis, Civil & Environmental Engineering, Davis, CA RMP Sources, Pathways, and Loadings Workgroup December 12, 2007 Agenda Item #4c
Finalized load estimates Addressed comments from May 2007 SPLWG Further analyses on potential source activation and watershed processing Timeline for journal article submission February 2008: draft article completion March 2008: internal review and submission May 2008 SPLWG: update on any response Since last meeting… Agenda Item #4c
Contaminant loading Load in Grams/Yr WY 2003 WY 2004 WY 2005 WY 2006 Avg. Annual Load (g) PCBs PCBs 9807706401,390950 (±330) DDT DDT 8506705801,260840 (±250) Chlor Chlor 690540420920640 (±120) Dieldrin70605011070 (±17) Agenda Item #4c Annual loads on the order of 0.5 to 1.5 kg per year in Guadalupe River for PCBs, DDT, and Chlordanes; Extrapolation to other watersheds (by area) suggests that combined loadings from local tributaries (e.g., >10 kg/yr of PCBs) are sufficient to significantly delay recovery from legacy contamination in the Bay.
Potential sources and distribution (hypotheses) Agenda Item #4c Dispersed non-point sources of legacy contamination by positive relationships between contaminant concentrations and SSC, as opposed to point sources that get diluted by increasing flows and sediment loads; Urban-to-rural gradient of increasing concentrations from lower to upper watershed hypothesized based on higher concentrations on rising stage of storm events compared to falling stage; Unique source activation hypothesized based on occurrence of PCB congener profile similar to Aroclor 1016, which varied from commonly observed patterns of Aroclor 1254 and 1260.
Agenda Item #4c p,p-DDD p,p-DDT Watershed processing Congener profiles of multiple-component contaminants (e.g., PCBs, DDT) help infer how mechanisms of source activation and transport differ between low and high flows. For example, the dominant parent component of technical DDT (p,p-DDT) comprises ~40% of total DDT concentrations in nearly all samples collected during flows above 20 m 3 /s indicating the transport of relatively unweathered sediment during high flows. Discharge (m 3 /s )
Modeling Hydrologic routing: where is the water coming from? Sediment transport: where is the sediment coming from? Contaminant transport: link evolving contaminant profiles to sources of water and sediment. Information gathering on other tributaries Monitoring other selected tributaries Extrapolation/modeling methods Evaluate treatment options Source reconnaissance Structural treatment selection, design, and placement Further study and information needs Agenda Item #4c