Duane C. Gossiaux | Search USGS

USGS2004

Time-dependent lethal body residues for the toxicity of pentachlorobenzene to Hyalella azteca

The study examined the temporal response of Hyalella azteca to pentachlorobenzene (PCBZ) in water-only exposures. Toxicity was evaluated by calculating the body residue of PCBZ associated with survival. The concentration of PCBZ in the tissues of H. azteca associated with 50% mortality decreased from 3 to 0.5 μmol/g over the temporal range of 1 to 28 d, respectively. No significant difference was observed in the body residue calculated for 50% mortality when the value was determined using live or dead organisms. Metabolism of PCBZ was not responsible for the temporal response because no detectable PCBZ biotransformation occurred over an exposure period of 10 d. A damage assessment model was used to evaluate the impact and repair of damage by PCBZ on H. azteca. The toxicokinetics were determined so that the temporal toxicity data could be fit to a damage assessment model. The half-life calculated for the elimination of PCBZ averaged approximately 49 h, while the value determined for the half-life of damage repair from the damage assessment model was 33 h.

Environmental Toxicology and Chemistry↗

USGS1993

Toxicity of contaminated sediments in dilution series with control sediments

T he use of dilutions has been the foundation of our approach for assessing contaminated water, and accordingly, it may be important to establish similar or parallel approaches for sediment dilutions. Test organism responses to dilution gradients can identify the degree of necessary sediment alteration to reduce the toxicity. Using whole sediment dilutions to represent the complex interactions of in situ sediments can identify the toxicity, but the selection of the appropriate diluent for the contaminated sediment may affect the results and conclusions drawn. Contaminated whole sediments were examined to evaluate the toxicity of dilutions of sediments with a diversity of test organisms. Dilutions of the contaminated sediments were prepared with differing diluents that varied in organic carbon content, particle size distribution, and volatile solids. Studies were conducted using four macroinvertebrates and a vascular, rooted plant. Responses by some test organisms followed a sigmoidal dose-response curve, but others followed a U-shaped curve. Initial dilutions reduced toxicity as expected, but further dilution resulted in an increase in toxicity. The type of diluent used was an important factor in assessing the sediment toxicity, because the control soil reduced toxicity more effectively than sand as a diluent of the same sediment. Using sediment chemical and physical characteristics as an indicator of sediment dilution may not be as useful as chemical analysis of contaminants, but warrants further investigation.

Chemosphere↗