A Berger-linear Buildup Approximation for Air.

ABSTRACT: A combination of the Berger and the linear buildup approximations with the assumption of conservation of energy was fitted for air. The values predicted by this Berger-linear buildup approximation were generally more accurate than those predicted by the Berger approximation alone. Although it is not as accurate as the geometric-progression approximation, the Berger-linear approximation is analytically simpler and makes it easier to find analytical solutions for point source kernel shielding calculations.

An Exact Solution for the Ground-level Gamma Dose Rate from a Spherical Gaussian Puff.

Analytical solutions of the absorbed dose rate integral for a spherically symmetric Gaussian puff were developed for both linear and Berger buildup approximations. Mathematically simpler solutions were also developed for the absorbed dose rate at the center of the puff. These solutions are valid for a ground-level receptor and both ground-level and elevated spherical puffs. Graphical solutions allow estimates of the ratio of the absorbed dose rate due to a puff to the absorbed dose rate for an infinite cloud with concentration equal to the maximum concentration at the center of the puff. Calculations also give the ratio of the absorbed dose rate integral due to photons from Compton scattering and secondary photons, assuming Berger buildup, to the absorbed dose rate integral using linear buildup for ranges of the Berger b parameter reported for air.

Optical characteristics of southeast Asia's regional aerosols and their sources.

The dominant optical characteristics of Southeast Asia (SEA)'s regional aerosols were determined from the cluster analysis of the 26 AERONET aerosol inversion products, including aerosol light scattering/absorption indicators and aerosol size/shape parameters retrieved from 2003 to 2007. The data sets were acquired from four stations: Bac Giang in Vietnam and Mukdahan, Pimai, and Silpakorn University in Thailand. The cluster analysis showed agreement among the aerosol optical characteristics, land cover/uses, season as the surrogate of the prevailing winds, and observations from the literature. The results of this study showed that during the northeast prevailing winds from mid-September to December, the high aerosol exposure events were most frequently observed over the upwind station and less often over the downwind stations. This aerosol exhibited a single scattering albedo (SSA) of approximately 0.95 (440 nm), a relatively low refractive index, and a larger fine-mode size, suggesting it had the characteristics of urban/industrial aerosols reported in the literature. These aerosol sources were upwind from Bac Giang, probably in eastern China. From January to April, the aerosol exhibited a lower SSA of approximately 0.90, a higher refractive index, and a smaller fine-mode size, suggesting biomass burning smoke reported in the literature. The SEA urban aerosol exhibited a mean SSA of approximately 0.90 (440 nm) or lower, and the coarse-mode aerosol, possibly road dust or soil dust, played a role from October to January when seasonal winds are strongest. The results from a canonical discriminant function analysis suggest that the dominant SEA aerosol clusters tended to be separated by a canonical function positively correlated with SSA, the fine-mode asymmetry factor, and the overall fine-mode size and negatively correlated with the refractive index.

Stable plume rise in a shear layer.

Solutions are given for plume rise assuming a power-law wind speed profile in a stably stratified layer for point and finite sources with initial vertical momentum and buoyancy. For a constant wind speed, these solutions simplify to the conventional plume rise equations in a stable atmosphere. In a shear layer, the point of maximum rise occurs further downwind and is slightly lower compared with the plume rise with a constant wind speed equal to the wind speed at the top of the stack. If the predictions with shear are compared with predictions for an equivalent average wind speed over the depth of the plume, the plume rise with shear is higher than plume rise with an equivalent average wind speed.

Solutions to the Gaussian cloud approximation for gamma absorbed dose.

Analytical solutions of the dose rate integral for the Gaussian cloud approximation to the Gaussian plume were developed. A solution for the I1 integral for a ground-level source and for the I2 integral for an elevated source were given in terms of special functions. The I2 solution was also extended for the Berger buildup factor. These enable rapid computation of I1 and I2 to estimate the dose rate.

Plume rise in a shear layer with neutral stability.

Several solutions have been published to predict the rise of buoyant plumes in a shear layer with a power-law velocity profile. Each of these solutions is either a special case or is based on oversimplifying assumptions. In this paper, solutions to the plume-rise equations are given for buoyant and nonbuoyant plumes with initial vertical momentum. Solutions are given for both point sources and sources with a finite initial size under neutral stability. For a constant wind speed, these solutions simplify to the conventional plume-rise equations.

Gaseous and particulate emissions from a DC arc melter.

Tests treating soils contaminated with metal compounds and radionuclide surrogates were conducted in a DC arc melter. The soil melted, and glassy or ceramic waste forms with a separate metal phase were produced. Tests were run in the melter plenum with either air or N2 purge gases. In addition to nitrogen, the primary emissions of gases were CO2, CO, oxygen, methane, and oxides of nitrogen (NO(x)). Although the gas flow through the melter was low, the particulate concentrations ranged from 32 to 145 g/m3. Cerium, a nonradioactive surrogate for plutonium and uranium, was not enriched in the particulate matter (PM). The PM was enriched in cesium and highly enriched in lead.

Metal Emissions from Joule-Heated Vitrification Systems.

Vitrification demonstrations were conducted for surrogates of three inorganic wastewater sludges in a high-temperature, refractory-lined, slurry-fed melter. The total par-ticulate concentrations and melter decontamination factors were determined for selected elements. The decontamination factors were less than 10 for cadmium and lead in all three demonstrations. The decontamination factors for chromium were less than 30 in the two demonstrations using refractories containing chromium, and they were greater than 150 for the demonstrations using refractories without chromium. Except for one demonstration on a surrogate waste with a high sulfate content, decontamination factors were above 80 for the other heavy metals in the demonstrations.

Performance of a Suspended-Growth Bioscrubber for the Control of Methanol.

An experimental study is presented on the control of methanol emissions using a single-stage, laboratory-scale, suspended-growth bioscrubber. The inlet concentration was 50 or 100 ppmv. The bioscrubber was operated for over 80 days at a solids residence time of either one or two days. The overall removal efficiency of the scrubber with biomass ranged from 69.0 to 81.0%. The efficiency increased with the liquid flow rate. Model simulations were in good agreement with the data.