Mercury concentrations and loads in a large river system tributary to San Francisco Bay, California, USA

Abstract

In order to estimate total mercury (HgT) loads entering San Francisco Bay, U.S.A., via the Sacramento-San Joaquin River system, unfiltered water samples were collected between January 2002 and January 2006 during high flow events and analyzed for HgT. Unfiltered HgT concentrations ranged from 3.2 to 75 ng/L and showed a strong correlation (r2 = 0.8, p < 0.001, n=78) to suspended sediment concentrations (SSC). During infrequent large floods, HgT concentrations relative to SSC were approximately twice as high as observed during smaller floods. This difference indicates the transport of more Hg-contaminated particles during high discharge events. Daily HgT loads in the Sacramento-San Joaquin River at Mallard Island ranged from below the limit of detection to 35 kg. Annual HgT loads varied from 61 +/- 22 kg (n=5) in water year (WY) 2002 to 470 +/- 170 kg (n=25) in WY 2006. The data collected will assist in understanding the long-term recovery of San Francisco Bay from Hg contamination and in implementing the Hg total maximum daily load, the long-term cleanup plan for Hg in the Bay.

Concentrations and loads of PCBs, dioxins, PAHs, PBDEs, OC pesticides and pyrethroids during storm and low flow conditions in a small urban semi-arid watershed

“…Continuous, short time interval pollutant concentrations were estimated using these pollutant-specific regressions with turbidity and then combined with the discharge data to derive "instantaneous" loads which were then summed to any longer time interval desired (storm, monthly, or annual). The TSR estimator has been discussed previously and found to work well for computing loads of suspended sediments and mercury for urbanized and mixed land use systems (e.g., Lewis, 1996;Quémerais et al, 1999;Wall et al, 2005;David et al, 2009;Ruzycki et al, 2011;Riscassi and Scanlon, 2013). Expanding upon what has been learned from previous authors, we show here that turbidity can form strong and significant correlations with many trace organic compounds and the TSR method is viable for loads estimation of particle-associated organic pollutants.…”

Mercury offloaded in Northern elephant seal hair affects coastal seawater surrounding rookery

“…On the basis of this estimate, we calculate that ∼0.2 kg organic Hg entered the nearshore environment of Año Nuevo during that molting season. To put that amount in perspective, the San Francisco Bay covers ∼1,100 km 2 , drains 40% of the state of California (26,27), and receives an estimated annual load of 8.0 kg MeHg from external sources such as rivers and point source discharges (25). Conversely, the Año Nuevo State Marine Conservation Area covers only 26.4 km 2 (28), indicating that the magnitude of annual inputs from pinniped colonization constitutes a relevant, previously unaccounted for, source of MeHg to that marine reserve.…”

Reducing methylmercury accumulation in the food webs of San Francisco Bay and its local watersheds

“…Combining this with the improved monitoring data on Hg loads entering the Bay via the Delta (David et al, 2009), which indicate an average annual Hg load of 260 kg, suggests particle concentrations average about 0.23 ppm. Moreover, this sediment load may decrease further due to the cessation of the hydraulic mining sediment pulse, increased sediment trapping in reservoirs, smaller floods, and enhanced bank protection (Schoellhammer, 2011).…”