Bacterial community structure and response to nitrogen amendments in Lake Shenandoah (VA, USA).

Microbial processes are critical to the function of freshwater ecosystems, yet we still do not fully understand the factors that shape freshwater microbial communities. Furthermore, freshwater ecosystems are particularly susceptible to effects of environmental change, including influx of exogenous nutrients such as nitrogen and phosphorus. To evaluate the impact of nitrogen loading on the microbial community structure of shallow freshwater lakes, water samples collected from Lake Shenandoah (Virginia, USA) were incubated with two concentrations of either ammonium, nitrate, or urea as a nitrogen source. The potential impact of these nitrogen compounds on the bacterial community structure was assessed via 16S rRNA amplicon sequencing. At the phylum level, the dominant taxa in Lake Shenandoah were comprised of Actinobacteria and Proteobacteria, which were not affected by exposure to the various nitrogen treatments. Overall, there was not a significant shift in the diversity of the bacterial community of Lake Shenandoah with the addition of nitrogen sources, indicating this shallow system may be constrained by other environmental factors.

Influence of automatic dishwashings and scrubbings on release of lead from glazed ceramicware.

Use of lead glazes on ceramicware and the release of lead from finished glazes are reviewed. Single units of ceramicware with initial lead leach levels from less than 0.1 to 470 micrograms/mL were subjected to multiple automatic dishwashings with intermediate scrubbing of the ware by plastic fiber pads. Ware was periodically leached with 4% acetic acid solution at room temperature for 24 h, and the solutions were analyzed for lead. Release of lead under these conditions is discussed. Results indicated that neither passive leachings nor multiple dishwashings and scrubbings can predict future lead-release characteristics of glazes and decorations.

Evaluation of electron capture gas chromatographic method for determination of methyl mercury in freezer-case seafoods.

A method was recently adopted by AOAC for determination of methyl-bound mercury in canned and fresh-frozen seafood by electron capture gas chromatography. That method was applied to the analysis of commercially prepared freezer-case seafoods. None of the commercially added ingredients produced electron capture responses that interfered in the analysis for methyl mercury. Recoveries of 95.7-114% were obtained in fortification studies of methyl mercury at 0.2 and 1.0 ppm levels. The applicability of aqueous methyl mercuric chloride solution for fortification studies was demonstrated.

Biodegradation of [C]Tri-p-Cresyl Phosphate in a Laboratory Activated-Sludge System.

Biodegradation of [C]tri-p-cresyl phosphate was studied in a laboratory model sewage treatment system to develop information on the nature of its transformation products. In 24-h experiments, 70 to 80% of tri-p-cresyl phosphate added at the 1-mug/ml level was degraded. The remaining parent compound was associated with the sludge solids. The major metabolite extracted with ethyl ether from the aqueous phase was identified as p-hydroxybenzoic acid by gas chromatography-mass spectrometry. Two unstable ether-extractable metabolites were not identified. The half-life of [C]tri-p-cresyl phosphate was estimated to be 7.5 h.

Comparative effects of feeding lead acetate and phospholipid-bound lead on blood and tissue lead concentrations in young and adult rats.

Two different forms of lead, lead acetate and phospholipid-bound lead, were fed to young and adult male rats for 10 weeks at the 300 ppm dietary level. Based on the lead concentrations found in selected tissues, our results indicate that the bioavailability of phospholipid-bound lead is similar to that of lead acetate at the 300 ppm level. Young rats had higher concentrations of lead in tissues than did adult rats.