Development and Evaluation of a Method to Determine Indicator Microorganisms in Air Emissions and Residue from Medical Waste Incinerators

To allow testing of microbial destruction in medical waste incinerators, methods were developed to determine indicator microorganisms (Bacillus Stearothermophilus spores) in incinerator air emissions and residue. The emission trapping train consisted of a water cooled glass probe and impingers containing a neutral phosphate buffer. In field tests, spores were injected directly into the probe, and results showed that approximately 60 percent of the spores were recovered. Spores were analyzed with adequate precision using a microbial membrane filter unit. Lab experiments indicated that spores were stable in neutral pH phosphate buffer for up to 20 days, and heat shocking samples (heating to 80°C for 20 minutes) reduced spore numbers in acidic or basic buffer. Laboratory tests also showed that 60 to 70 percent of spores initially added to ash were recovered up to 22 days after addition of the spores. In addition, lab tests showed that spores can be effectively recovered from residue test pipes spiked with indicator spores.     

Kinetics and Mechanism of the Reaction of Azide with Ozone in Aqueous Solution

ABSTRACT

The stoichiometry of the reaction of aqueous ozone with sodium azide was studied at pH 12 (mainly) where a yellow metastable intermediate is observed. We propose that this is hypoazidite (N₃O^- ), analogous to hypobromite, and that it plays a central role in the azide catalyzed decompostion of ozone. The yellow intermediate is unstable in acid, in which it rapidly decomposes, generating N₂ and NO₂ ^-.

The rate of reaction was studied at pH 2.0–3.5, with the ionic strength at 0.6 M and temperature at 3–15 ° C. The intrinsic second-order rate constants were found to be k _HN3 ≤ ≈ 400 M^-1sec^-1 and k _N3- = (8.7 ± 0.5) × 10⁵ M^-1sec^-1 (3 °C, 0.6 M), both in agreement with the only other previous study. The rate constant at 25 °C was estimated using the following experimentally determined parameters: ln k_N3- (M^-1sec^-1) = (5.73 ± 0.36) × 10³/T (K) + (28.34 ± 1.27). The value of k_N3- estimated in this way is (2.5 ± 0.1) × 10⁶ M^-1sec^-1 at 25 °C and 0.6 M. The enthalpy of reaction (A H) is -48 ± 3 kJ mol^-1.     

The Effect of Reformulated Gasoline on Ambient Carbon Monoxide Concentrations in Southeastern Wisconsin

Abstract

Reformulated gasoline (RFG) contains oxygen additives such as methyl tertiary butyl ether or ethanol. The additives enable vehicles to burn fuel with a higher air/fuel ratio, thereby lowering the emission of carbon monoxide (CO) and volatile organic compounds (VOCs). Because VOCs react with sunlight to form ozone (O₃), the Clean Air Act requires severe O₃ nonattainment areas such as southeastern Wisconsin to use RFG. On July 17, 2001, the U.S. Environmental Protection Agency (EPA) granted Milwaukee, WI, and Chicago, IL, a waiver from the VOC reduction requirement of Phase II RFG. The VOC reduction requirement was lowered from 27.4% of the 1990 baseline fuel to 25.4%. The assumption was that ethanol-blended RFG would lower summertime CO concentrations sufficiently to offset the increased VOC emissions. The waiver is estimated to increase VOC emissions by ～0.8%, or 0.4 t of VOC on a hot summer weekday. This study evaluates whether RFG has been effective in lowering southeastern Wisconsin ambient CO concentrations. Three years of ambient CO data before RFG was introduced were compared with the first three years of ambient CO data after RFG was introduced. This paper also evaluates how the meteorology, vehicle inspection/maintenance program, vehicle miles traveled, and stationary source emissions influence CO concentrations. The winter decrease in ambient CO concentrations was found to be statistically significant, while the summer data showed no statistically significant change, indicating that RFG is most effective lowering ambient CO concentrations in cold weather.     

MTBE in California Drinking Water: An Analysis of Patterns and Trends

Over the past decade, there has been much publicity surrounding the impact of Methyl tert -butyl ether (MTBE) on drinking water supplies in the United States. In California, the presence of MTBE in groundwater and drinking water has led to a ban on the future use of MTBE in gasoline. Other states, such as those in the northeast, are also seeking ways to reduce or eliminate the use of MTBE due to perceived threats to the environment and public health. Despite claims about the incidence of MTBE in drinking water, no comprehensive characterization has been conducted on the available drinking water monitoring data. This paper provides a detailed analysis of the MTBE drinking water data compiled by the California Department of Health Services (CDHS) from 1995 to 2000. We find that MTBE was detected in about 1.3% of all drinking water samples, 2.5% of drinking water sources, and 3.7% of drinking water systems in California over this 6-year period. Our analysis reveals that many drinking water sources are not sampled routinely for MTBE, and in those sources that appear to be affected by MTBE, the compound is not consistently detected. The majority of MTBE detections are also concentrated in several geographic areas, which contain about 9-21% of the total California population. Average detected MTBE concentrations have decreased significantly since 1995 and 1996, ranging from 5 to 15 ppb over the last 3 years depending on the outcome of interest. Of the samples in which MTBE was present above the analytical detection limit, the concentrations in approximately 73% of drinking water samples and 86% of drinking water sources and systems were below the State's primary health-based standard of 13 ppb. Our findings suggest that, although some drinking water supplies in California have been affected by MTBE, the majority of drinking water sources and systems either have not been affected at all or contain MTBE at concentrations below levels that are likely to be of health concern.     

Is shrimp farming a successful adaptation to salinity intrusion? A geospatial associative analysis of poverty in the populous Ganges–Brahmaputra–Meghna Delta of Bangladesh

The Ganges–Brahmaputra–Meghna delta of Bangladesh is one of the most populous deltas in the world, supporting as many as 140 million people. The delta is threatened by diverse environmental stressors including salinity intrusion, with adverse consequences for livelihood and health. Shrimp farming is recognised as one of the few economic adaptations to the impacts of the rapidly salinizing delta. Although salinity intrusion and shrimp farming are geographically co-located in the delta, there has been no systematic study to examine their geospatial associations with poverty. In this study, we use multiple data sources including Census, Landsat Satellite Imagery and soil salinity survey data to examine the extent of geospatial clustering of poverty within the delta and their associative relationships with salinity intensity and shrimp farming. The analysis was conducted at the union level, which is the lowest local government administrative unit in Bangladesh. The findings show a strong clustering of poverty in the delta, and whilst different intensities of salinization are significantly associated with increasing poverty, neither saline nor freshwater shrimp farming has a significant association with poverty. These findings suggest that whilst shrimp farming may produce economic growth, in its present form it has not been an effective adaptation for the poor and marginalised areas of the delta. The study demonstrates that there are a series of drivers of poverty in the delta, including salinization, water logging, wetland/mudflats, employment, education and access to roads, amongst others that are discernible spatially, indicating that poverty alleviation programmes in the delta require strengthening with area-specific targeted interventions.     

Mobilization of arsenic in aquifers from the Datong Basin,China: Evidence from geochemical and iron isotopic data

Iron isotope compositions of various Fe pools in aquifer sediments were measured at a known As-contaminated site in the Datong Basin, China. The δ⁵⁶Fe values of HCl-extracted poor-crystalline Fe(III) range widely from ?0.41‰ to 0.36‰. We interpret the low Fe(II)/Fe_Extractable ratios (<50%) and the negative correlation between Fe(II)/Fe_Extractable and δ⁵⁶Fe values in HCl-extracted poor-crystalline Fe to be best explained by redox cycling of Fe induced by microbial Fe(III) reduction. However, the high Fe(II)/Fe_Extractable ratios (?70%) and positive correlation between Fe(II)/Fe_Extractable and δ⁵⁶Fe values for HCl-extracted poor-crystalline Fe indicates production of sulfides (FeSs). The δ⁵⁶Fe values of crystalline Fe(III) extracted by reductant appears to be comparatively small varying from ?0.01‰ to 0.24‰, which is consistent with the δ⁵⁶Fe values for ferric oxides/hydroxides having undergone microbial Fe(III) reduction. The Fe isotope composition of various Fe pools shows the transformation between crystalline Fe(III) and poor-crystalline crystalline Fe(III) and the secondary Fe(II) phases has already occurred or is occurring in aquifer sediments. More importantly, there is a significant difference in the As concentrations in crystalline Fe(III) oxides/hydroxides and HCl-extracted Fe phases. The concentrations of As range from 1.6 to 29.9 mg kg^?1 and from 0.6 to 3.0 mg kg^?1, for crystalline Fe(III) and HCl-extracted Fe phases respectively. Accordingly, the transformation of Fe minerals induced by microbial Fe(III) reduction can contribute to the mobilization of As. This study is the first to examine the Fe isotope compositions in high As aquifer sediments; the results show that the Fe isotope would be an important tool in demonstrating the enrichment of As in groundwater.     

Rapid and Sensitive LC/MS/MS Direct Injection Method for the Determination of Trace Level Corexit EC9500A Oil Dispersant in Seawater

A rapid and sensitive liquid chromatography tandem mass spectrometry (LC/MS/MS) method for the determination of trace dioctyl sulfosuccinate (DOSS) concentrations in seawater samples has been established. The method is well suited to aquatic environment impact monitoring following application of the dispersant Corexit EC9500A. Linearity of the method was demonstrated down to 0.05 ng/mL^?1 (0.05 µgL^?1) DOSS in seawater, with a 2.4% relative standard deviation precision for preparation replicates. A US EPA method limit of detection of <0.02 ng/mL^?1 (<0.02 µgL^?1) was calculated and specificity was confirmed by monitoring of two qualifier ions at 291.1 m/z and 227.1 m/z. These transitions were confirmed by QToF analysis to be associated with the DOSS precursor ion at 421.2 m/z. For application to seawater samples and samples containing oil particulates, a practical and repeatable calibration range of 0.5 ng/mL^?1 (0.5 µgL^?1) to 25.0 ng/mL^?1 (25.0 µgL^?1) DOSS is reported. The method was shown to have excellent precision and accuracy, with a consistent ≤1.6% relative standard deviation for system suitability standards at 0.5 ng/mL^?1 (0.5 µgL^?1) and linear weighted (1/x) regression coefficients of determination ≥0.995. The surfactant nature of the analyte is discussed in relation to detection limit and loss of analyte. Speculation of a relationship between DOSS in association or aggregation with divalent cations, such as Ca²⁺ present in salt water and hard water, is suggested. The consequent effects on cell ionic balance and membrane function are discussed.