A baseline assessment of contamination in the Sacramento deep water ship channel.

The Sacramento Deep Water Ship Channel (SDWSC) in the San Francisco Estuary, which is an active commercial port, is critical habitat for pelagic fish species including delta smelt (Hypomesus transpacificus), longfin smelt (Spirinchus thaleichthys), and Sacramento perch (Archoplites interruptus). Pelagic organism decline has been attributed to covarying factors such as manipulation of habitat, introduction of invasive species, decrease in food production, and contaminant exposure. Quantification of bioavailable toxicant loads in the SDWSC is limited despite previous surveys that have detected elevated contaminant concentrations in the sediments. Therefore, the focus of the present study was to characterize the bioavailability of the contaminants in the SDWSC from six sites along the channel. At each site, organochlorine pesticides (OCPs), pyrethroid insecticides, polyaromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) were quantified in sediment, zooplankton, and suspended solids. In addition, Tenax extraction was used to measure the bioaccessible fraction of sediment-associated contaminants freely dissolved in the water. Bioaccessible contaminants in the sediment provided an uptake route for these stressors into invertebrates and fish with bioaccessible OCPs being found at all sites, particularly 4,4'-dichlorodiphenyldichloroethylene (DDE). Bifenthrin was the only pyrethroid detected in the chosen matrices and it was found at concentrations below levels of concern. Bioaccessible PAHs were found at all sites, with highest detections for phenanthrene and pyrene. No PCBs were detected in sediments, but were detected in both suspended solids and zooplankton. Contaminant concentrations overall were significantly higher in suspended solids, followed by zooplankton and sediments. The highest sediment concentrations of DDE, fluoranthene, pyrene, and dibenzo[a,h]anthracene exceeded sediment quality benchmarks indicating potential risk to sediment-dwelling species. Finally, elevated contaminant levels were found in both suspended solids and zooplankton, suggesting additional risk to pelagic species in the SDWSC.

Assessing the Influence of Organic Carbon, Aging Time and Temperature on Bioaccessibility of Bifenthrin.

Tenax extraction, a measure of chemical desorption rates from sediments, was used to evaluate the bioaccessibility of bifenthrin in two different sediments exposed to three temperatures aged over a 56-d holding period. A 24-h single-point Tenax extraction was used and parent 14C-bifenthrin and polar metabolites were quantified in the sediment and Tenax. Bioaccessibility of bifenthrin was inversely related to the organic carbon (OC) content in the sediment, holding time, and temperature. Sequestration of the bifenthrin into slowly desorbing fractions within the sediment appears to have decreased degradation of the parent compound into metabolites and decreased the amount of parent compound bioaccessible for uptake by the Tenax. These results suggest that the environmental risk of bifenthrin to aquatic species is greatest immediately after the pesticide enters a waterbody after runoff, for low-OC content sediments, and in areas or seasons where water temperatures are colder.

Does Activated Carbon Used for Soil Remediation Impact Eisenia fetida?

Because granular activated carbon can sequester organic pollutants, a potential strategy for reducing the bioavailability of organic contaminants in soil is through its application to the soil's surface. It is well understood that activated carbon is effective in the remediation of air, water, sediment, and soil, but less information is available on the potential toxicity of activated carbon to native wildlife following in situ remedial applications. Several studies have evaluated the effects of activated carbon on aquatic species; however, less is known about its toxicity to terrestrial species. The present study aimed to evaluate the potential lethal and sublethal effects of activated carbon on adult and juvenile Eisenia fetida, which are earthworms in the family Lumbricidae. The percentage of mortality, initial weight, and pre- and postdepuration weights of the worms were observed following exposure to a range of activated carbon concentrations, from 0.5% to 10% based on the soil's wet weight. These concentrations exceeded the 2%-4% activated carbon typically applied in the field. Activated carbon had no statistically significant effects on E. fetida survival; however, significant although inconsistent effects were observed on earthworm biomass. Although some statistical significance in biomass was observed, the biological significance of these effects is unclear. Overall, the concentrations of activated carbon applied in the field for soil remediation are unlikely to impact earthworm survival, although further testing, specifically on potential sublethal toxic effects, is required. Environ Toxicol Chem 2023;42:1420-1430. © 2023 SETAC.