A total of 68 gram-negative freshwater bacterial isolates were screened for their ability to receive and express plasmids from Pseudomonas aeruginosa donors. The plate mating technique identified 26 of the isolates as recipient active for the self-transmissible wide-host-range plasmid R68; 10 were recipient active by R68 mobilization for the wide-host-range plasmid cloning vector R1162. Frequencies of transfer were compared by using three conjugal transfer procedures: broth, plate, and filter mating. For every recipient tested, a solid environment was superior to a liquid environment for transfer. The broth mating technique failed to demonstrate R68 transfer in 63% of the recipient-active isolates. Filter mating, in general, yielded the highest transfer frequencies. The more-rapid plate mating procedure, however, was just as sensitive for testing the capacity of natural isolates to participate in conjugal plasmid transfer.

First-order biotic and abiotic degradation rate constants of 14 pesticides were determined in estuarine water and sediment/water slurry systems. Test systems used environmentally realistic concentrations of pesticides in sterile and nonsterile samples of water and sediment taken directly from the field. Thiobencarb, sulprofos, chlorothalonil, diclofop-methyl, fenthion, oxyfluorfen, methoxychlor, phorate, and trifluralin all showed significantly (p <= 0.01) more degradation in the presence of nonsterile sediment than in the presence of sterile sediment. Most of these nine pesticides biodegraded significantly faster in flasks containing sediment than in those with water alone. Endosulfan and PCNB, however, biodegraded faster in the absence of sediment. EPN and chlorpyrifos were degraded primarily by abiotic processes. Methomyl did not significantly degrade under any test conditions. Oxyfluorfen and chlorpyrifos were also slow to degrade, with half-lives of generally over two weeks in nonsterile sediment. Diclofop-methyl and phorate were the least persistent, with half-lives of a few days or less.

Our results have demonstrated that TCE may be biodegraded to nontoxic products under certain conditions. Trichloroethylene is apparently degraded by strain G4 to CO2, cellular carbon, and inorganic chloride. This activity requires aerobic conditions and exposure of the organism to certain aromatic compounds. This exposure is required to induce the bio-synthesis of one or more enzymes that fortuitously degrade TCE. The normal function of the enzyme(s) is the metabolism of the aromatic compounds. Evidence from the work with environmental samples indicates that the natural microflora in a variety of areas is capable of TCE degradation if stimulated by the appropriate aromatic compounds. These results are presently being applied to the development of bench-scale continuous treatment systems for further assessment of biodegradation as a means for detoxification of TCE-contaminated sites.

Tests were conducted to compare the environmental fate of shale oil-derived jet fuel with that of petroleum-derived jet fuel. These tests included chemical characterization of the fuels, and the water-soluble fraction of each fuel, also measurement of volatilization and biodegradation rates in laboratory systems designed to simulate three disparate aquatic environments. No major differences in the volatilization and biodegradation rates of the two fuels were found. Differences in composition were generally small and should not cause the behavior of the fuels in aquatic environments to differ.

Disadvantages of current biodegradation tests are examined: the need for high substrate concentrations, lack of parent compound concentration measurements, no estimation of sediment effects, failure to indicate compounds to which microbial populations must adapt to degrade, and lack of site specificity in innocula selection. A modified river die-away test is proposed for determining biodegradability of organic compounds and testing for toxic degradation products. The present test uses shake flasks containing sterile (2% formalin) and nonsterile site water: both with, and without, site sediment (500 mg/liter). Concurrent toxicity testing with mysids or daphnids provides a sensitive assay for the detection of toxic metabolites. Examples of three test compounds are given: methyl parathion, which undergoes rapid, sediment-mediated biodegradation; dibutylphthalate, to which some microbial communities exhibit an adaptation phenomenon; and methoxychlor, which has a relatively low water solubility and high sediment partition coefficient. The relative merits of this test procedure are discussed.

Statistical analysis of degradation rates of methyl parathion samples from two Gulf Coast estuaries over a three-year period indicated that biodegradation occurred in the presence of sediment but was insignificant in water. Sediment rates always showed the same relative five-fold difference at a primary site within each estuarine area. Samples from 11 ancillary sites indicated biodegradation rates in sediments can be subdivided into two groupings which were independent of seasonal differences (excluding temperature). Spatial variations in rates, therefore, may be of minor environmental significance for this chemical in estuarine areas.

Abstract The influence of lugworms (Arenicola cristata Stimpson) and seagrass (Thalassia testudinum Koenig) on Kepone® (chlordecone) distribution in sediment/water systems was examined. Radiolabeled Kepone was introduced into continuous-flow sediment/water systems, and the dissolved and sorbed concentrations of Kepone were quantified. Lugworm activity decreased the Kepone concentration in the water and increased its concentration in the sediment. The presence of seagrasses did not appreciably affect the concentration of Kepone in the water. Bioturbation appeared to be the prime factor in the transport of Kepone from water to sediment.

Biotic and abiotic degradation of di-n-butylphthalate (DBP) in water and sediment/water systems from six different sites was investigated under laboratory conditions. DBP disappearance was rapid in all microbially active systems and substantially reduced under sterile conditions. Adaptation of microbial populations to degrade DBP was indicated in six of nine evaluations conducted. The presence of sediment significantly increased biodegradation rates in five of the six sites.