Estimation of Contaminant Loads from the Sacramento‐San Joaquin River Delta to San Francisco Bay

Abstract

Contaminant concentrations from the Sacramento-San Joaquin River watershed were determined in water samples mainly during flood flows in an ongoing effort to describe contaminant loads entering San Francisco Bay, CA, USA. Calculated PCB and total mercury loads during the 6-year observation period ranged between 3.9 and 19 kg/yr and 61 and 410 kg/yr, respectively. Long-term average PCB loads were estimated at 7.7 kg/yr and total mercury loads were estimated at 200 kg/yr. Also monitored were PAHs, PBDEs (two years of data), and dioxins/furans (one year of data) with average loads of 392, 11, and 0.15/0.014 (OCDD/OCDF) kg/yr, respectively. Organochlorine pesticide loads were estimated at 9.9 kg/yr (DDT), 1.6 kg/yr (chlordane), and 2.2 kg/yr (dieldrin). Selenium loads were estimated at 16 300 kg/yr. With the exception of selenium, all average contaminant loads described in the present study were close to or below regulatory load allocations established for North San Francisco 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

“…This might be because the Houston watersheds have less urban development (14-89%), or because Suarez et al was unable to capture the peak discharge in all but two of 10 samples. In contrast, stormwater concentrations (average 0.022 ng/l) measured in the large and rural-dominated Sacramento River watershed at the head of San Francisco Bay (David et al, 2015) were similar to the low end of concentrations reported for the urban watersheds previously described.…”

“…Although highly urbanized, the Z4LA watershed contains no known PCB source areas; PCB transport in this watershed is likely more generally representative of older mixed urban and industrial land uses. In contrast, watersheds with known specific industrial sources appear to exhibit average concentrations in excess of about 100 ng/l (Hwang and Foster, 2008;Marsalek and Ng, 1989;McKee et al, 2012;Zgheib et al, 2011Zgheib et al, , 2012 and watersheds with little to no urbanization dominated by agriculture and open space exhibit average concentrations b5 ng/l (David et al, 2015;Foster et al, 2000a;Howell et al, 2011;McKee et al, 2012) (see Supplementary Information Figure S3). …”

“…Based on previous studies that have characterized a wide range of pollutant concentrations and loads to the Bay (e.g. Wenning et al, 1999;She et al, 2002;Greenfield and Davis, 2005;Oros et al, 2005;Davis et al, 2007;Oram et al, 2008;Weston et al, 2009;Weston and Lydy, 2010;David et al, 2015), the San Francisco Bay Regional Water Quality Control Board has specified urban stormwater runoff in the total maximum daily loads reports as a large and potentially controllable source of pollutants for enhanced management (e.g. Water Board, 2008).…”

Assessment of the contribution of utility vault water to surface water pollution

“…Similarly, total PCBs in Houston, Texas, ranged from 0.00082 to 0.094 μg/L with a mean of 0.005 μg/L (Howell et al 2011 ). Concentrations of PCBs were particularly low (flow weighted average of 0.000340 μg/L) in the San Francisco Bay Delta, where the two major rivers feed the San Francisco Bay; the rivers drain mostly agricultural land and open space (David et al 2015 ).…”

An integrating geospatial technology with microbiology in isolating and characterizing selenite-reducing bacteria from two mangrove areas along the Red Sea, Egypt

“…Though humans require trace quantities of selenium for cellular functions, elemental selenium and selenite oxyanions are lethal in even small dosages (Fordyce, 2005). Due to the human activities, selenium contamination is considered to be the main environmental pollution found almost everywhere (soil, water) (David et al, 2015) Selenium has widespread uses in industrial and agricultural processes, which are responsible for its high toxic levels in the environment (Pierru et al, 2006). Microorganisms have been shown to play major role in the reduction of different Se oxyanions (Nancharaiah and Lens, 2015).…”