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The use of nitrate in the bioremediation of fuel-contaminated groundwater was shown to offer only moderate improvement in contaminant reduction. Core material removed from the nitrate treated and control areas showed varying degrees of alkylbenzene removal governed by the denitrifying and iron-reducing characteristics of the soil column above the aquifer. The reductions in the aquifer's contaminants were shown to be a function of anaerobic bioremediation rather than a direct effect of nitrification.

The re-deposition of colloids mobilized in the aquifer and gas binding due to hydrogen peroxide decomposition, rather than to iron precipitation, likely caused the reduced permeability of the aquifer near delivery systems. This was found following an investigation of the effects of iron oxidation state and concentration, the presence of colloidal materials and the impact of nutrient solutions and hydrogen peroxide in the feedwater on the permeability of the aquifer material in the bioremediation experience at Eglin Air Force Base in Florida. Bioremediation at the site was stopped because of the failure of delivery systems owing to iron precipitation.

Although Concentrated Animal Feeding Operations (CAFOs) have been identified as potentially important sources for the release of estrogens into the environment, information is lacking on the concentrations of estrogens in whole lagoon effluents (including suspended solids) which are used for land application. Lagoons associated with swine, poultry, and cattle operations were sampled at three locations each for direct analysis for estrogens by GC/ MS/MS and estrogen conjugates by LC/MS/MS. Estrogen conjugates were also analyzed indirectly by first subjecting the same samples to enzyme hydrolysis. Solids from centrifuged samples were extracted for free estrogens to estimate total estrogen load. Total free estrogen levels (estrone, 17α-estradiol, 17β-estradiol, estriol) were generally higher in swine primary (1000ߝ21000 ng/L), followed by poultry primary (1800ߝ4000 ng/L), dairy secondary (370–550 ng/L), and beef secondary (22–24 ng/L) whole lagoon samples. Swine and poultry lagoons contained levels of 17α- estradiol comparable to those of 17β-estradiol. Confirmed estrogen conjugates included estrone-3-sulfate (2–91 ng/L), 17β-estradiol-3-sulfate (8–44 ng/L), 17α-estradiol-3-sulfate (141ߝ182 ng/L), and 17β-estradiol-17-sulfate (72– 84 ng/L) in some lagoons. Enxzymatic hydrolysis indicated the presence of additional unidentified estrogen conjugates not detected by the LC/MS/MS method. In most cases estrogen conjugates accounted for at least a third of the total estrogen equivalents. Collectively, these methods can be used to better determine estrogen loads from CAFO operations, and this research shows that estrogen conjugates contribute significantly to the overall estrogen load, even in different types of CAFO lagoons. [ABSTRACT FROM AUTHOR]