An 8-yr study was conducted to better understand factors influencing year-to-year variability in field-scale herbicide volatilization and surface runoff losses. The 21-ha research site is located at the USDA-ARS Beltsville Agricultural Research Center in Beltsville, MD. Site location, herbicide formulations, and agricultural management practices remained unchanged throughout the duration of the...

Selenium (Se) can be assimilated and volatilized via the sulfate assimilation pathway. Cystathionine-gamma-synthase (CGS) is thought to catalyze the synthesis of Se-cystathionine from Se-cysteine, the first step in the conversion of Se-cysteine to volatile dimethylselenide. Here the hypothesis was tested that CGS is a rate-limiting enzyme for Se volatilization. Cystathionine-gamma-synthase from...

Compared with dry and wet deposition fluxes, air-water exchange flux cannot be directly measured experimentally. Its model-based calculation contains considerable uncertainty because of the uncertainties in input parameters. To capture the inherent variability of air-water exchange flux of PCBs across the lower Great Lakes and to calculate their annual gross volatilization loss, 57 pairs of air...

Selenium (Se) can be assimilated and volatilized via the sulfate assimilation pathway. Cystathionine-c-synthase (CGS) is thought to catalyze the synthesis of Se-cystathionine from Se-cysteine, the first step in the conversion of Se-cysteine to volatile dimethylselenide. Here the hypothesis was tested that CGS is a rate-limiting enzyme for Se volatilization. Cystathionine-c-synthase from Arabido...

Constructed wetlands have been used effectively to reduce the mass loads of organic and nutrient components from swine anaerobic lagoons. Continuous marsh wetlands with gentle slope and intermittent flows seem to be the best for promoting oxidation and minimizing ammonia volatilization. However, the pond section of the marsh-pond-marsh section could potentially be effectively aerated by mechani...

The output from a pesticiie screening model indicated that chemicals with low Henry’s Law constants (A,,) will tend to accumulate at the soil surface when water is evaporating, resulting in an increased volrtilixation with time. Volatilixation losses and surface distributions of two pesticides with widely differing KH were measured to test the predictions of the screening model, particularly wi...

A numerical model is developed to predict the aqueous concentrations of sparingly soluble compounds resulting from oil, fuel, or chemical spills onto rivers. The model computes the concentration of compounds both in the slick phase and in the aqueous phase by simulating the processes that affect the fate of the spilled compound. Processes simulated by the model include spreading and drifting of...

The volatilization and soft ionization of complex neutral macromolecules at low energies has remained an outstanding challenge for several decades. Most volatilization techniques in mass spectrometry produce ions already in the source and most of them lead to particle velocities in excess of several hundred meters per second. For many macromolecules, post-ionization is inefficient since electro...

Of 100 strains of iron-oxidizing bacteria isolated, Thiobacillus ferrooxidans SUG 2-2 was the most resistant to mercury toxicity and could grow in an Fe(2+) medium (pH 2.5) supplemented with 6 microM Hg(2+). In contrast, T. ferrooxidans AP19-3, a mercury-sensitive T. ferrooxidans strain, could not grow with 0.7 microM Hg(2+). When incubated for 3 h in a salt solution (pH 2.5) with 0.7 microM Hg...

Mangrove killifish, Rivulus marmoratus, are tolerant of prolonged periods of air exposure (>30 days). Air-exposed R. marmoratus eliminate more than 40% of their total ammonia through NH(3) volatilization; however, the sites and mechanisms are unclear. We hypothesized that the cutaneous surface is an important site of NH(3) volatilization in air-exposed R. marmoratus. Ion-selective microelectrod...