J. E. Leatherbarrow

Removal Efficiencies of a Bioretention System for Trace Metals, PCBs, PAHs, and Dioxins in a Semiarid Environment

AbstractThe negative effects of urbanization on water quantity and quality and the performance of bioretention for treating runoff and reducing concentrations and loads of sediment, nutrients, pathogens, and selected trace metals have been well documented. This study evaluated the efficiency of a bioretention system installed in semiarid Daly City, California, for a large suite of pollutants, including some that have been rarely evaluated in such systems. Stormwater flow and pollutant concentrations were measured before and after the construction of a bioretention system consisting of rain gardens and a bioswale. After installation, concentrations of most pollutants were reduced and met water quality guidelines. Water quality improvements (concentration or load reductions) were demonstrated for total Hg, polychlorinated biphenols (PCBs) and dioxins ranging between 18 and 100%, and a suite of more conventional pollutants [SSC, Cd, Cu, Ni, Pb, Zn, and polycyclic aromatic hydrocarbons (PAHs)] ranging between...

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

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.