Soluble hydrocarbon and dissolved oxygen (DO) in a shallow aquifer beneath a field site were characterized by sampling ground water at 42 monitoring wells. Results from 10 sampling periods over three years showed a significant reduction in total benzene mass with time in ground water. These reduction and leakage rates from sources were determined from material balance and nonlinear least‐squares analyses. The natural attenuation rate was calculated to be 0.95%/day. Spatial relationships between DO and total benzene, toluene, and xylene (BTX) were shown to be strongly correlated by statistical analyses and solute transport modeling. In addition, laboratory microcosm biodegradation experiments were performed to determine possible threshold limits for aromatic hydrocarbon oxidation under varying levels of dissolved oxygen. The results were remarkably consistent with field data on the presence of high or low levels of BTX and DO in several monitoring well‐water samples.

Abstract-Ecotoxicological assessments of contaminated soil aim to understand the effect of introduced chemicals on the soil flora and fauna. Ecotoxicity test methods were developed and conducted on hydrocarbon-contaminated soils (Ͻ5,000-30,000 mg/kg total petroleum hydrocarbon) and on adjacent uncontaminated control soils from eight field locations. Tests included 7-d, 14-d, and chronic survival tests and reproduction assays for the earthworm (Eisenia fetida) and seed germination, root length, and plant growth assays for corn, lettuce, mustard, and wheat. Species-specific responses were observed with no-observed effect concentrations (NOECs) ranging from Ͻ1 to 100% contaminated soil. The 14-d earthworm survival NOEC was equal to or greater than the reproduction NOEC values for numbers of cocoons and juveniles, which were similar to one another. Cocoon and juvenile production varied among the control soils. Germination and root length NOECs for mustard and lettuce were less than NOECs for corn and wheat. Root length NOECs were similar to or less than seed germination NOECs. Statistically significant correlations (p Ͻ 0.05) for earthworm survival and seed germination as a function of hydrocarbon measurements were found. The 14-d earthworm survival and the seed germination tests are recommended for use in the context of a risk-based framework for the ecological assessment of contaminated sites.

Ecotoxicological assessments of contaminated soil aim to understand the effect of introduced chemicals on the soil flora and fauna. Ecotoxicity test methods were developed and conducted on hydrocarbon‐contaminated soils (<5,000–30,000 mg/kg total petroleum hydrocarbon) and on adjacent uncontaminated control soils from eight field locations. Tests included 7‐d, 14‐d, and chronic survival tests and reproduction assays for the earthworm (Eisenia fetida) and seed germination, root length, and plant growth assays for corn, lettuce, mustard, and wheat. Species‐specific responses were observed with no‐observed effect concentrations (NOECs) ranging from <1 to 100% contaminated soil. The 14‐d earthworm survival NOEC was equal to or greater than the reproduction NOEC values for numbers of cocoons and juveniles, which were similar to one another. Cocoon and juvenile production varied among the control soils. Germination and root length NOECs for mustard and lettuce were less than NOECs for corn and wheat. Root length NOECs were similar to or less than seed germination NOECs. Statistically significant correlations (p < 0.05) for earthworm survival and seed germination as a function of hydrocarbon measurements were found. The 14‐d earthworm survival and the seed germination tests are recommended for use in the context of a risk‐based framework for the ecological assessment of contaminated sites.

Abstract-Aquatic toxicity of nine commercial-grade alcohol ethoxylate surfactants was studied in acute exposures to fathead minnow (Pimephales promelas) and Daphnia magna. All studies were conducted in accordance with USEPA TSCA Good Laboratory Practice Standards. Mean measured surfactant concentrations in the exposure solutions showed good agreement with nominal concentrations for both fathead minnow (R 2 ϭ 0.98, p ϭ 0.05) and daphnid (R 2 ϭ 0.99, p ϭ 0.05) tests. Surfactant recoveries ranged from 59 to 97% and 67 to 106% in the fathead minnow and daphnid solutions, respectively. Response of both species to the surfactants was generally similar. Surfactant toxicity tended to increase with increasing alkyl chain lengths. The effect of low average ethylene oxide (EO) groups on increased surfactant toxicity was more evident in the daphnid exposures. Quantitative structure-activity relationship (QSAR) models were developed from the data, which relate surfactant structure to toxicity. The models predict increasing toxicity with decreasing EO number and increasing alkyl chain length. The models also indicate that average alkyl chain length has a greater effect on toxicity than average EO groups. Further, the models indicate that both species did not differ markedly in their response to alkyl chain length effects, while the number of EO groups had a stronger effect on daphnids than fathead minnow. Model-predicted toxicity agreed well with toxicity estimated from USEPA alkyl ethoxylates SARs and with toxicity values reported in the literature for several surfactants previously studied.

Measurements of the lipogenic rate in adipose tissue samples obtained sequentially by biopsy from the same pig may be useful for many nutritional experiments. The average lipogenic rate over a short period (several days to 2 weeks) appears to be relatively stable if the pigs weigh about 20 kg initially and if approximately 10 animals are allotted to each experimental group. The lipogenic rate is readily influenced by the feeding regimen (amount and timing). It is easily lowered by less than ad libitum dietary intakes and is influenced especially by the intake pattern for several days preceding the rate determination. In two different experiments, the lipogenic rate obtained at either 20 or 50 kg body weight was not effective as a predictor of backfat thickness or loineye area measured 13 or 6 weeks later, respectively.