Effect of Refractory on the Thermal Stability of SF6

The thermal decomposition of SF₆ is known to be oxygen-independent. Nevertheless, because of its high stability, the use of SF6 as a "conservative" surrogate in incinerator performance evaluation has been advocated and researched. This paper shows that refractory decreases markedly the stability of SF₆. The resulting increase in SF₆ decomposition was from 0 percent to 95 percent at 900°C, and the temperatures at which 90-99 percent decomposition occurred were lowered by 300-150°C. Refractory also decreased the stability of CCl₄ and C₂Cl₄, but to a lesser extent. The difference between the decompositions of C₂Cl₄ and SF₆ was reduced from several orders of magnitude to a factor of 2-4. Such a drastic and adverse change in relative stability could render SF₆ unsuitable as a "conservative" surrogate. The requirements for a "conservative" surrogate and the need for caution in its use are discussed, and further research areas are indicated.     

Evaluation of the Use of Solar Irradiation for the Decontamination of Soils Containing Wood Treating Wastes

Laboratory evaluation of the efficacy of soil phase photodegradation of recalcitrant hazardous organic components of wood treating wastes is described. The photodecomposition of anthracene, biphenyl, 9H-carbazole, m-cresol, dibenzofuran, fluorene, pentachlorophenol, phenanthrene, pyrene and quinoline under UV and visible light was monitored over a 50-day reaction period in three test soils. Methylene blue, riboflavin, hydrogen peroxide, peat moss and diethylamine soil amendments were evaluated as to their effect on the enhancement of compound photoreaction rates in the test soil systems. Dark control samples monitored over the entire study period were utilized to quantify non-photo mediated reaction losses. Compounds losses in both the dark control and irradiated samples were found to follow first order kinetics, allowing the calculation of first order photodegradation reaction rate constants for each test soil/compound combination. Degradation due to photochemical activity was observed for all test compounds, with compound photolytic half-lives ranging from 7 to approximately 180 days. None of the soil amendments were found to improve soil phase photodegradation, although photosensitization by anthracene was shown to significantly enhance the rate of photodegradation of the other test compounds. Soil type, and its characteristic of internal reflectance, proved to be the most significant factor affecting compound degradation rates suggesting the necessity for site specific assessments of soil phase photodegradation potential.     

Emission Impacts of Electric Vehicles

Alternative vehicular fuels are proposed as a strategy to reduce urban air pollution. In this paper, we analyze the emission Impacts of electric vehicles In California for two target years, 1995 and 2010. We consider a range of assumptions regarding electricity consumption of electric vehicles, emission control technologies for power plants, and the mix of primary energy sources for electricity generation. We find that, relative to continued use of gasoline-powered vehicles, the use of electric vehicles would dramatically and unequivocally reduce carbon monoxide and hydrocarbons. Under most conditions, nitrogen oxide emissions would decrease moderately. Sulfur oxide and particulate emissions would Increase or slightly decrease. Because other areas of the United States tend to use more coal in electricity generation and have less stringent emission controls on power plants, electric vehicles may have less emission reduction benefits outside California.     

The OTC Challenge: Adding VOC Controls in the Northeast

The 1990 Clean Air Act Amendments create an ozone transport region made up of the northeastern and mid-Atlantic states. These new provisions call for VOC and NOx controls even in clean areas of the region in order to reduce ozone transport to downwind areas. The stationary and mobile source requirements will subject many air pollution sources to controls for the first time.

The provisions also create an Ozone Transport Commission, which can recommend that additional control measures be adopted in all or part of the region. So far, the commission has focused primarily on region-wide mobile source controls, such as California low emission vehicle standards and reformulated gasoline. But lately it has been paying increasing attention to stationary source measures, including NOx controls.     

The Cost Estimation of Thermal and Catalytic Incinerators for the Control of VOCs

In an earlier paper, major commercially available incinerator technologies designed to treat dilute waste gas streams containing volatile organic compounds (VOCs) were described in a qualitative comparison. In addition, a simplified procedure was outlined through which important sizing parameters could be calculated given certain information about the waste gas. This paper describes the use of these parameters in developing a study (±30percent) cost estimate for the total capital investment and the total annual costs incurred in treating a waste stream of volatile organic compounds (VOCs). An illustrative problem used in the former paper is completed here in order to contrast some of the economic differences between thermal and catalytic incinerator systems.     

Methodology for Siting Ambient Air Monitors at the Neighborhood Scale

Abstract

In siting a monitor to measure compliance with U.S. National Ambient Air Quality Standards (NAAQS) for par-ticulate matter (PM), there is a need to characterize variations in PM concentration within a neighborhood-scale region to achieve monitor siting objectives. A simple methodology is provided here for the selection of a neighborhood-scale site for meeting either of the two objectives identified for PM monitoring. This methodology is based on analyzing middle-scale (from 100 to 500 m) data from within the area of interest. The required data can be obtained from widely available dispersion models and emissions databases.

The performance of the siting methodology was evaluated in a neighborhood-scale field study conducted in Hudson County, NJ, to characterize the area’s inhalable particulate (PM₁₀) concentrations. Air monitors were located within a 2- by 2-km area in the vicinity of the Lincoln Tunnel entrance in Hudson County. Results indicate the siting methodology performed well, providing a positive relationship between the predicted concentration rank at each site and the actual rank experienced during the field study. Also discussed are factors that adversely affected the predictive capabilities of the model.     

Application of Forensic Techniques for Age Dating and Source Identification in Environmental Litigation

A multitude of forensic techniques are available for age dating and source identification, including corrosion models for underground storage tanks, the commercial availability of a compound, chemical associations with discrete types of manufacturing processes, chemical profiling, proprietary additives, stable isotope analysis, degradation models, biomarkers and contaminant transport models. The selection and use of these techniques in environmental litigation must be thoroughly understood and applied to be effective as forensic evidence. When introduced as scientific evidence, the governing assumptions and quality of the data are critically evaluated and frequently successfully challenged. The purpose of this paper is to present an overview of commonly used environmental forensic techniques and their possible applications so that a user can decide which technique or combination of methods is most appropriate for their case.     

Estimating the Cumulative Ecological Effect of Local Scale Landscape Changes in South Florida

Ecosystem restoration in south Florida is a state and national priority centered on the Everglades wetlands. However, urban development pressures affect the restoration potential and remaining habitat functions of the natural undeveloped areas. Land use (LU) planning often focuses at the local level, but a better understanding of the cumulative effects of small projects at the landscape level is needed to support ecosystem restoration and preservation. The South Florida Ecosystem Portfolio Model (SFL EPM) is a regional LU planning tool developed to help stakeholders visualize LU scenario evaluation and improve communication about regional effects of LU decisions. One component of the SFL EPM is ecological value (EV), which is evaluated through modeled ecological criteria related to ecosystem services using metrics for (1) biodiversity potential, (2) threatened and endangered species, (3) rare and unique habitats, (4) landscape pattern and fragmentation, (5) water quality buffer potential, and (6) ecological restoration potential. In this article, we demonstrate the calculation of EV using two case studies: (1) assessing altered EV in the Biscayne Gateway area by comparing 2004 LU to potential LU in 2025 and 2050, and (2) the cumulative impact of adding limestone mines south of Miami. Our analyses spatially convey changing regional EV resulting from conversion of local natural and agricultural areas to urban, industrial, or extractive use. Different simulated local LU scenarios may result in different alterations in calculated regional EV. These case studies demonstrate methods that may facilitate evaluation of potential future LU patterns and incorporate EV into decision making.