Sediment core versus grab samples: evaluation of contamination and toxicity at a DDT-contaminated site.

Four sites from a stream system near Huntsville, Alabama, contaminated with DDT and its metabolites, were sampled using a coring device. Grab samples were also collected at these and five other sites. Analytical and toxicological evaluations were made on both sets of samples. Core samples provided vertical delineation of toxicity and contamination in sediments, and documented periods of sedimentation with clean material, which appears to be isolating the contaminated sediments from benthic communities. Grab samples yielded less information about the sites. Relationships between DDT concentration and sediment toxicity to Chironomus tentans were similar regardless of the sampling method. Substantial increases in toxicity occurred in most samples when concentrations exceeded 3000 micrograms of DDT residue/g organic carbon.

Relationships of quantitative structure-activity to comparative toxicity of selected phenols in the Pimephales promelas and Tetrahymena pyriformis test systems.

The relative toxic response of 27 selected phenols in the 96-hr acute flowthrough Pimephales promelas (fathead minnow) and the 48- to 60-hr chronic static Tetrahymena pyriformis (ciliate protozoan) test systems was evaluated. Log Kow-dependent linear regression analyses revealed that the data from each test system consisted of two linear equations. The less toxic chemicals form a relationship which models polar narcosis; these chemicals are slightly more active than the baseline toxicity of nonionic narcotic chemicals. The more toxic chemicals form a relationship which models uncoupling of oxidative phosphorylation. Regression analysis of fathead minnow toxicity (log LC50 (mol/liter] vs Tetrahymena toxicity (log BR (mmol/liter] showed good correlation between the two systems. An exception appears to be 4-nitrophenol, which is more active in the Tetrahymena system than in the fathead minnow and lies outside the 95% confidence interval. Reanalysis following deletion of 4-nitrophenol results in the equation log LC50 = -0.9192 (log BR) -3.5035; n = 26, r2 = 0.887.

Toxicity of selected priority pollutants to various aquatic organisms.

Toxicity tests were conducted with selected compounds listed by the United States Environmental Protection Agency (EPA) as priority pollutants. Acute toxicity information was determined for acenaphthene, arsenic trioxide, cadmium chloride, mercury(II) chloride, silver nitrate, chlordane, endosulfan, and heptachlor. Acute tests were conducted using one or more of the following species: fathead minnows (Pimephales promelas), channel catfish (Ictalurus punctatus), rainbow trout (Salmo gairdneri), brown trout (Salmo trutta), brook trout (Salvelinus fontinalis), bluegills (Lepomis macrochirus), snails (Aplexa hypnorum), or chironomids (Tanytarsus dissimilis). Acute values from these tests ranged from a silver nitrate 96-hr LC50 of 6.7 micrograms/liter for fathead minnows to an arsenic trioxide 48-hr LC50 of 97,000 micrograms/liter for chironomids. In addition to acute tests, a fathead minnow embryo-larval exposure was conducted with silver nitrate to estimate chronic toxicity. The estimated maximum acceptable toxicant concentration for silver nitrate, based on fathead minnow survival, lies between 0.37 and 0.65 micrograms/liter.

Effects of phenol, 2,4-dimethylphenol, 2,4-dichlorophenol, and pentachlorophenol on embryo, larval, and early-juvenile fathead minnows (Pimephales promelas).

Embryos of fathead minnows were more resistant to phenol, 2,4-dimethylphenol (2,4-DMP), 2,4-dichlorophenol (2,4-DCP), and pentachlorophenol (PCP) than were larval or juvenile life stages. Growth of 28-day-old fish was the most sensitive indicator of stress during exposures to phenol, 2,4-DMP, and PCP, whereas survival was the most sensitive indicator of toxic effects from 2,4-DCP exposure. Based on these effects, the estimated maximum acceptable toxicant concentration for fathead minnows in Lake Superior water lies between 1,830 and 3,570 micrograms/L for phenol; 1,970 and 3,110 micrograms/L for 2,4-DMP; 290 and 460 micrograms/L for 2,4-DCP; and 44.9 and 73.0 micrograms/L for PCP.