Concentrations and loads of PCBs and OC pesticides in

the Guadalupe River watershed

Jon LeatherbarrowJon Leatherbarrow1,21,2, Lester McKee, Lester McKee11, John , John OramOram11

11San Francisco Estuary Institute, Oakland, San Francisco Estuary Institute, Oakland, CACA

22UC Davis, Civil & Environmental UC Davis, Civil & Environmental Engineering, Davis, CAEngineering, Davis, CA

RMP Sources, Pathways, and Loadings WorkgroupDecember 12, 2007

Agenda Item #4c

LocationLocationAgenda 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…Since last meeting…

Agenda Item #4c

Contaminant loadingContaminant loading

Load in Load in Grams/YrGrams/Yr

WY2003

WY2004

WY2005

WY2006

Avg. Annual Load (g)

PCBsPCBs 980 770 640 1,390 950 (±330)

DDTDDT 850 670 580 1,260 840 (±250)

ChlorChlor 690 540 420 920 640 (±120)

DieldrinDieldrin 70 60 50 110 70 (±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 Potential sources and distribution (hypotheses)(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

Q (cubic meters)

0 50 100 150 200

Con

trib

utio

n to

TD

DT

(%

)

0

20

40

60

80 p,p’-DDD ▼ p,p’-DDT ○

Watershed processingWatershed 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 m3/s indicating the transport of relatively unweathered sediment during high flows.

Discharge (m3/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 needsFurther study and information needs

Agenda Item #4c