1. METHYL MERCURY IN THE SAN JOAQUIN RIVER BASIN Chris Foe Central Valley Regional Water Quality Control Board 916-464-4713 cfoe@waterboards.ca.gov

2. OUTLINE MERCURY CONTROL PROGRAMS. --Schedule --Toxicity METHYL MERCURY IN SAN JOAQUIN RIVER. --Sources --Transport CONCLUSIONS http://www.waterboards.ca.gov/centralhttp://www.waterboards.ca.gov/centralvalley/programs/tmdl/deltahg

3. MAP OF SAMPLING LOCATIONS IN SAN JOAQUIN RIVER WATERSHED

4. Table 1. Methyl mercury concentrations (ng/l) in the San Joaquin River Basin.

5. Figure 3. Water balance for the San Joaquin River at Vernalis during the non-irrigation season (Sept-Mar)

6. Figure 6. Methyl mercury mass balance for the San Joaquin River at Vernalis during the non-irrigation season (Sept-Mar)

8. Figure 7. Methyl mercury load at Vernalis as a function of the load at Crows Landing.

9. CONCLUSIONS CENTRAL VALLEY MERCURY TMDLS ARE BASED ON METHYL MERCURY BECAUSE STATISTICALLY SIGNIFICANT POSITIVE CORRELATIONS EXIST BETWEEN AQUEOUS AND BIOTIC METHYL MERCURY CONCENTRATIONS. MUD SLOUGH IN THE SAN JOAQUIN BASIN PROVIDES 9% OF THE WATER AND 49% OF THE METHYL MERCURY LOAD AT VERNALIS DURING THE NON IRRIGATION SEASON. STATISTICALLY SIGNIFICANT POSITIVE CORRELATIONS EXIST BETWEEN METHYL MERCURY LOADS AT CROWS LANDING AND 50 MILES DOWNSTREAM AT VERNALIS SUGGESTING THAT MOST OF THE METHYL MERCURY IS BEING PRODUCED IN THE TOP OF THE BASIN AND IS BEING TRANSPORTED IN A CONSERVATIVE FASHION DOWN RIVER. ALSO BROUGHT POSTERS ON METHYL MERCURY CONCENTRATIONS AND LOADS IN THE SACRAMENTO BASIN AND YOLO BYPASS.