Environmental science & technology
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Environ. Sci. Technol. · Sep 2005
Effect of water/fuel emulsions and a cerium-based combustion improver additive on HD and LD diesel exhaust emissions.
One of the major technological challenges for the transport sector is to cut emissions of particulate matter (PM) and nitrogen oxides (NOx) simultaneously from diesel vehicles to meet future emission standards and to reduce their contribution to the pollution of ambient air. Installation of particle filters in all existing diesel vehicles (for new vehicles, the feasibility is proven) is an efficient but expensive and complicated solution; thus other short-term alternatives have been proposed. It is well known that water/diesel (W/ D) emulsions with up to 20% water can reduce PM and NOx emissions in heavy-duty (HD) engines. ⋯ In contrast, CO (-32%), TEQ (-14%), and NOx (-6%) were reduced by the emulsion for the HD engine, and only hydrocarbons were slightly increased (+16%). Whereas the Cerium-based additive was inefficient in the HD engine for all emissions except for TEQ (-39%), it markedly reduced all emissions for the LD vehicles (PM -13%, CO -18%, HC -26%, TEQ -25%) except for NOx, which remained unchanged. The presented data indicate a strong potential for reductions in PM emissions from current diesel engines by optimizing the fuel composition.
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Environ. Sci. Technol. · Jun 2005
ReviewLessons from endocrine disruption and their application to other issues concerning trace organics in the aquatic environment.
In the past 10 years, many thousands of research papers covering the many different aspects of endocrine disruption in the environment have been published. What has been learned from all this research? We have tried to reduce this very large volume of research into a relatively small number of "lessons". Hence, this paper is not a typical review, but instead it summarizes our personal opinions on what we consider are the major messages to have come from all this research. ⋯ If so, we encourage them to submit them as responses to our paper. Our own lessons range widely, from the design and interpretation of data from fieldwork studies, through some key messages to come out of the very many laboratory studies that have been conducted, to issues around the sources and fates in the environment of endocrine-disrupting chemicals, and finally to the key role of sewage treatment in controlling the concentrations of these chemicals in the aquatic environment. Having (hopefully) learned our lessons, we have then applied them to the difficult issue of how best to approach future concerns about the potential impacts of other new and emerging contaminants (e.g., pharmaceuticals) on wildlife.
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Environ. Sci. Technol. · Mar 2005
Bioaerosol emission rate and plume characteristics during land application of liquid class B biosolids.
This study investigated bioaerosol emission rates and plume characteristics of bioaerosols generated during land application of liquid Class B biosolids. In addition, it compared the rate of aerosolization of coliphages and total coliform bacteria during land application of liquid Class B biosolids to the rate of aerosolization during land application of groundwater inoculated with similar concentrations of Escherichia coli and coliphage MS2. Air samples were taken immediately downwind of a spray applicator as it applied liquid (approximately 8% solids) biosolids to farmland near Tucson, Arizona. ⋯ Because concentrations of coliphages and coliforms were similar in the liquid biosolids and the seeded water, itwas concluded that some property of biosolids reduces aerosolization of microorganisms relative to groundwater. Additional experiments utilizing a novel air sampling protocol showed that the duration of bioaerosol exposure immediately (2 m) downwind of biosolids spray application is brief and the plume of bioaerosols generated is discrete. Additional air samples showed that aerosolization of coliphages and coliform bacteria after liquid biosolids have been applied to land does not occur at detectable levels.
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Environ. Sci. Technol. · Nov 2004
Particles in filter effluent: the roles of deposition and detachment.
Particles in the effluent of granular media filters can be classified as influent particles that were never removed or as particles that detached after prior deposition. To determine the effects of particle size, filter media depth and filter run duration on the relative fraction of each class, laboratory experiments were performed using suspensions of four sizes of polystyrene particles (0.2, 1.2, 2.5, and 4.0 microm diameters) that were destabilized with 0.04 M calcium chloride and continuously supplied to filters after flocculation. To investigate particle attachment alone, three sizes (1.4, 4.0, and 9 microm) of fluorescent microspheres (FM) were periodically pulse injected immediately ahead of the filter media. ⋯ FM deposition followed theory, while results show that particle detachment was significant from an early phase of filtration (100 minutes). The detached fraction of effluent particles increased with particle size (1 to 12 microm range) and filter depth. These model system results suggest that detachment plays a significant role in the origin of filter effluent particles in full-scale water treatment systems.
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Environ. Sci. Technol. · Mar 2004
Quantifying hazardous species in particulate matter derived from fossil-fuel combustion.
An analysis protocol that combines X-ray absorption near-edge structure spectroscopy with selective leaching has been developed to examine hazardous species in size-segregated particulate matter (PM) samples derived from the combustion of fossil fuels. The protocol has been used to identify and determine quantitatively the amounts of three important toxic species in combustion-derived PM: viz., nickel sulfides in residual oil fly ash (ROFA) PM, and Cr(VI) and As(III) species in coal fly ash PM. ⋯ Detailed information on the presence of these toxic species in PM samples is of significant interest to epidemiological and toxicological studies of the health effects of both source and ambient PM. Additionally, information is obtained on insoluble forms that may be useful for source attribution and on the distribution of phases between size fractions that may be related to formation mechanisms of specific toxic species during combustion.