Donald W. Schults

Sediment toxicity to a marine infaunal amphipod: Cadmium and its interaction with sewage sludge

Abstract The acute toxicity of cadmium to the marine infaunal amphipod, Rhepoxynius abronius , was determined separately in sediment and seawater. Most cadmium added to test sediment was bound to particles and less than 5% was dissolved in interstitial water. The LC 50 based on cadmium concentration in interstitial water was similar to the LC 50 based on cadmium concentration in seawater without sediment. Cadmium in interstitial water, rather than that bound to particles, therefore appears responsible for acute sediment toxicity to this species. The addition of small quantities of sewage sludge or an increase in the proportion of the fine fraction of sediment particles significantly reduced the toxicity of cadmium in sediment. Binding of cadmium by sediment particles may explain the presence of phoxocephalid amphipods at sites where sewage and metal pollution occur together. The cadmium sensitivity of R. abronius is similar to that of several marine invertebrates commonly used in seawater bioassays. This amphipod is a useful test species for sediment bioassays used in research, monitoring and regulatory programs.

Temporal changes in the benthos along a pollution gradient: Discriminating the effect of natural phenomena from sewage-industrial wastewater effects

Abstract As pollution from the Los Angeles County Sanitation Districts (LACSD) outfalls decreased between 1980 and 1983, the macrobenthic community partially recovered and surficial (0–2 cm deep) sediment contamination and toxicity decreased at 60 m water depth along a pollution gradient from the outfalls. Pollution from the LACSD outfalls continued to decrease but macrobenthic conditions and surficial sediment quality deteriorated 1 km, was unchanged 3 km, and improved 5–15 km from the LACSD outfalls between 1983 and 1986. The net effect of natural phenomena is indicated when ecosystem changes occur in the opposite direction from that expected under prevailing pollution conditions. Our data suggest that the net effect of natural phenomena (e.g. winter storms, El Nino) on the benthos was greater than LACSD wastewater effects 1 km, about equal to LACSD wastewater effects 3 km, and less than the LACSD wastewater effects 5–15 km from the outfalls at the LACSD 1983–1986 mass emission rate. Surficial sediment samples collected beyond the 1 km station from the LACSD outfalls probably represented ⪢ 3 years of natural + effluent particulates accumulation, and they were, therefore, better suited for detecting long-term trends than for testing short-term temporal variability in surficial sediment contamination and toxicity. Nevertheless, some contaminants in the surficial sediments significantly increased between 1983 and 1986, probably primarily reflecting renewed wastewater effects near the outfalls and the effects of natural phenomena (e.g. storm-induced sediment transport or erosion) further from the outfalls. Since natural phenomena may have an effect on the benthos ≥ 3 years of LACSD wastewater effects, short-term benthic changes must be interpreted cautiously at the study site.

A comparison of methods for collecting interstitial water for trace organic compounds and metals analyses

Abstract Several common materials and methods used to collect interstitial water (IW) were evaluated to determine their effect on the accuracy and precision of measured concentrations of selected organic compounds and metals. We compared the concentration of pollutants in dosed seawater before and after exposure to stainless steel and Teflon centrifuge tubes, glass fiber and Nuclepore filters, cellulose dialysis membranes and fritted glass tubes. Exposure to most hardware materials did not significantly affect the concentration of four metals (Cd, Cr, Cu, Pb) but there was significant loss (up to 79%) of two organic compounds (fluoranthene, p,p′-DDE) to almost all the hardware materials tested. Of five commonly used IW collection methods (centrifuging, centrifugal drainage or basal cup, squeezing, vacuum filtration and dialysis) investigated, the centrifuge method was judged the most accurate and precise for polycyclic aromatic hydrocarbons and PCBs. All IW collection methods tested showed high variability for the metals. As a result, with one exception (Cu), there was no significant difference detected in the accuracy of the methods for metals.

Toxicity of sewage sludge toRhepoxynius abronius, a marine benthic amphipod

Relative toxicity of sewage sludges from six treatment plants was determined by the LC50 of sludge-sediment mixtures to the infaunal marine amphipod,Rhepoxynius abronius. LC50s were measured as the increase in the percent total volatile solids (TVS) of the mixture due to the addition of sludge required to kill 50% of the amphipods during a 10-day exposure. LC50s ranged from 2.83% TVS addition for sludge from the small, domestic community of Waldport, Oregon to <0.1% TVS addition for metropolitan, more industrialized sources in Los Angeles, California. The toxicity of the sludge-sediment mixtures is attributed primarily to chemical contamination rather than organic enrichment. Rank correlations between toxicity and specific chemicals were usually not statistically significant, indicating that different combinations of stresses involving multiple or unmeasured factors were probably responsible for observed effects. Integrative measures of contamination (oil/grease concentration; consensus ranking of contamination based on 15 parameters) were significantly correlated withR. abronius survival indicating that the more toxic sludges had a higher overall level of contamination.

Selected chemical contaminants in surface sediments of Commencement Bay and the tacoma Waterways, Washington, USA

Abstract Eight metals, 21 organic priority pollutants, and 11 other contaminants and contaminant-related sediment characteristics were measured in surface sediments (upper 2 cm) at 21 locations in Commencement Bay and the Tacoma Waterways, Washington. Summary statistics were calculated and statistical approaches (analysis of variance, multiple comparisons tests, cluster analysis and principal component analysis) were applied to subsets of the data to classify sediment contamination. Overall sediment contamination was highest in the Sitcum, City and Hylebos Waterways, intermediate in Commencement Bay, at the entrances to the Tacoma Waterways and in the outer reaches of the Blair and Hylebos Waterways, and lowest at the Blair Waterway turning basin, the mouth of the Puyallup River and at a reference site near Browns Point. High concentrations of some contaminants appeared to be related to proximity to sources of contaminants. Depositional vectors, and chemical adsorption processes may also influence the spatial distribution of sediment contamination in the study area. Results of simple and partial correlation analyses indicate that arsenic, iron and manganese may be more closely associated with the clay fraction, while cadmium, copper and polynuclear aromatic hydrocarbons may be more closely associated with the total organic carbon content of sediments. We were unable to discriminate statistically between the affinity of chromium, lead, zinc and phthalates with the % clay or the total organic carbon content of sediments.

A comparison of interstitial water isolation methods demonstrates centrifugation with aspiration yields reduced losses of organic constituents

Spiked sediment and seawater were used to evaluate the recoveries of neutral organic compounds in interstitial water (IW) separated by centrifugation and sampled using a unique aspiration system. An average recovery of 94%±0.8% (SE, n=116) of ten polynuclear aromatic hydrocarbons and four chlorinated hydrocarbons was obtained from spiked estuarine IW using the aspiration system. Centrifugation of spiked sediment using the aspiration system recovered significantly higher IW concentrations of acenaphthene, phenanthrene, fluoranthene and DOC than did IW filtration, or in situ IW collection by fritted glass, or membrane covered, vessels.