L.R. Krumholz | Geology Reports

USGS1997

Anaerobic aquifer transformations of 2,4-Dinitrophenol under different terminal electron accepting conditions

We evaluated the susceptibility of 2,4-dinitrophenol (2,4-DNP) and 2,4-diaminophenol to anaerobic biodegradation in aquifer slurries. Aquifer microorganisms depleted 2,4-DNP at rates of 25, 9 and 0.4 μM/day under methanogenic, sulfate-reducing and nitrate-reducing conditions, respectively. Rates of abiotic, 2,4-DNP loss in autoclaved control incubations were 7.2, 6.2 and 0.95 μM/day respectively. Abiotic, 2,4-DNP reduction was especially important as the first step in its transformation. 2-Amino-4-nitrophenol was produced by this process, but this compound was further metabolized in methanogenic and sulfate-reducing aquifer slurries. This partially reduced compound persisted in autoclaved controls and in the nitrate-reducing aquifer slurries. Aquifer slurries incubated with either 2,4-DNP or 2,4-diaminophenol produced methane when incubated with no other electron acceptor suggesting that mineralization had occurred under these conditions. In parallel experiments, aquifer slurries amended with 2,6-dinitrophenol or picric acid did not produce methane at levels above the substrate unamended controls.

Anaerobe↗

USGS1997

Transformations of TNT and related aminotoluenes in groundwater aquifer slurries under different electron-accepting conditions

The transport and fate of pollutants is often governed by both their tendency to sorb as well as their susceptibility to biodegradation. We have evaluated these parameters for 2,4,6-trinitrotoluene (TNT) and several biodegradation products. Slurries of aquifer sediment and groundwater depleted TNT at rates of 27, 7.7 and 5.9 μM day −1 under methanogenic, sulfate-reducing and nitrate-reducing conditions, respectively. Abiotic losses of TNT were determined in autoclaved controls. Abiotic TNT loss and subsequent transformation of the products was also observed. These transformations were especially important during the first step in the reduction of TNT. Subsequent abiotic reactions could account for all of the transformations observed in bottles which were initially nitrate-reducing. Other controls removed TNT reduction products at much slower rates than slurries containing live organisms. 2-Amino-4,6-dinitrotoluene was produced in all slurries but disappeared in methanogenic and in sulfate-reducing slurries within several weeks. This compound was converted to 2,4-diamino-6-nitrotoluene in all slurries with subsequent removal of the latter from methanogenic and sulfate-reducing slurries, while it persisted in autoclaved controls and in the nitrate-reducing slurries. Aquifer slurries incubated with either 2,4- or 2,6-diaminotoluene showed losses of these compounds relative to autoclaved controls under nitrate-reducing conditions but not under sulfate-reducing or methanogenic conditions. These latter compounds are important as reduced intermediates in the biodegradation of dinitrotoluenes and as industrial chemicals. In experiments to examine sorption, exposure to landfill sediment resulted in losses of approximately 15% of diaminotoluene isomers and 25% of aminodinitrotoluene isomers from initial solution concentrations within 24 h. Isotherms confirmed that the diaminotoluenes were least strongly sorbed and the amino-dinitrotoluenes most strongly sorbed to this sediment, while TNT sorption capacity was intermediate. In our studies, 2,4,6-triaminotoluene sorption capacity was indeterminate due to its chemical instability. Coupled with biodegradation information, isotherms help describe the likelihood of contaminant removal, persistence, and movement at impacted sites.

Journal of Industrial Microbiology and Biotechnolo↗

USGS1997

A rapid and simple method for estimating sulfate reduction activity and quantifying inorganic sulfides

A simplified passive extraction procedure for quantifying reduced inorganic sulfur compounds from sediments and water is presented. This method may also be used for the estimation of sulfate reduction rates. Efficient extraction of FeS, FeS 2 , and S 2- was obtained with this procedure; however, the efficiency for S 0 depended on the form that was tested. Passive extraction can be used with samples containing up to 20 mg of reduced sulfur. We demonstrated the utility of this technique in a determination of both sulfate reduction rates and reduced inorganic sulfur pools in marine and freshwater sediments. A side-by-side comparison of the passive extraction method with the established single-step distillation technique yielded comparable results with a fraction of the effort.

Applied and Environmental Microbiology↗