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561.
Emissions of organic compounds and trace metals in fine particulate matter from motor vehicles: a tunnel study in Houston, Texas 总被引:1,自引:0,他引:1
Chellam S Kulkarni P Fraser MP 《Journal of the Air & Waste Management Association (1995)》2005,55(1):60-72
Fine particulate matter (PM) samples collected in a highway tunnel in Houston, TX, were analyzed to quantify the concentrations of 14 n-alkanes, 12 polycyclic aromatic hydrocarbons, and nine petroleum biomarkers, as well as 21 metals, with the ultimate aim of identifying appropriate tracers for diesel engines. First, an exploratory multivariate dimensionality reduction technique called principal component analysis (PCA) was employed to identify all potential candidates for tracers. Next, emission indices were calculated to interpret PCA results physically. Emission indices of n-heneicosane, n-docosane, n-tricosane, n-tetracosane, n-pentacosane, fluoranthene, and pyrene were correlated highly and increased strongly with percentage carbon present in the tunnel emanating from diesel vehicles. This suggests that these organic compounds are useful molecular markers to separate emissions from diesel and gasoline engines. Additionally, the results are the first quantification of the metal composition of PM with aerodynamic diameters smaller than 2.5 microm (PM2.5) emissions from mobile sources in Houston. PCA of trace metal concentrations followed by emission index calculations revealed that barium in fine airborne particles can be linked quantitatively to diesel engine emissions, demonstrating its role as an elemental tracer for heavy-duty trucks. 相似文献
562.
Hui Yin Xinping Wang Zhangjie Qin Matthew Ginder-Vogel Shuang Zhang Shuqi Jiang Fan Liu Shiwei Li Jing Zhang Yan Wang 《环境科学学报(英文版)》2018,(3)
Hexagonal turbostratic birnessite,with the characteristics of high contents of vacancies,varying amounts of structural and adsorbed Mn~(3+),and small particle size,undergoes strong adsorption reactions with trace metal(TM)contaminants.While the interactions of TM,i.e.,Zn~(2+),with birnessite are well understood,the effect of birnessite structural characteristics on the coordination and stability of Zn~(2+)on the mineral surfaces under proton attack is as yet unclear.In the present study,the effects of a series of synthesized hexagonal turbostratic birnessites with different Mn average oxide states(AOSs)on the coordination geometry of adsorbed Zn~(2+)and its stability under acidic conditions were investigated.With decreasing Mn AOS,birnessite exhibits smaller particle sizes and thus larger specific surface area,higher amounts of layer Mn~(3+)and thus longer distances for the first Mn\O and Mn\Mn shells,but a low quantity of available vacancies and thus low adsorption capacity for Zn~(2+).Zn K-edge EXAFS spectroscopy demonstrates that birnessite with low Mn AOS has smaller adsorption capacity but more tetrahedral Zn(~(IV)Zn)complexes on vacancies than octahedral(~(VI)Zn)complexes,and Zn~(2+)is more unstable under acidic conditions than that adsorbed on birnessite with high Mn AOS.High Zn~(2+)loading favors the formation of~(VI)Zn complexes over~(IV)Zn complexes,and the release of Zn~(2+)is faster than at low loading.These results will deepen our understanding of the interaction mechanisms of various TMs with natural birnessites,and the stability and thus the potential toxicity of heavy metal pollutants sequestered by engineered nano-sized metal oxide materials. 相似文献
563.
Malcolm S. Cresser Richard P. Smart Matthew Clark Andrew Crowe Danielle Holden Pippa J. Chapman Anthony C. Edwards 《Water, Air, & Soil Pollution: Focus》2004,4(6):85-95
Spatial and temporal changes in mobility of N species have been studied for three UK upland river networks, the Etherow in the South Pennines, the Nether Beck in the Lake District and the Dee in NE Scotland. The catchments are subject to N deposition at 35.1, 22.0 and 10.8–15.6 kg N ha–1 yr–1, respectively. TheNH
4
+
leaching appears to be predominantly regulated by flowpath in more polluted upland catchments. It is greatest where water draining acidified peaty soils contributes more to total discharge. Soluble organic matter may provide the dominant counter anion. In the Etherowand Dee catchments, which are dominated by acid mineral and organic soils, at high discharge NO
3
–
also appears to be associated with greater input of water from acidified soils. In contrast, for the Nether Beck, higher NO
3
–
concentrations are associated with tributaries draining soils contributingwater with higher alkalinity, suggesting nitrification is important. For the Etherow and Dee, dissolved organic N (DON) appears to originate predominantly from acidified, peaty soils. Spiking experiments with peat soil from the Etherow catchment confirmed the limited capacity of these soils to utilize inorganic N inputs, favouring equilibration with NH
4
+
inputs and leaching losses of inorganic N throughout the year. 相似文献
564.
MacManes MD 《Die Naturwissenschaften》2011,98(11):951-960
Differences in the number of sexual partners (i.e., mating system) have the potential to exert a strong influence on the bacterial
communities present in reproductive structures like the vagina. Because this structure serves as a conduit for gametes, bacteria
present there may have a pronounced, direct effect on host reproductive success. As a first step towards the identification
of the relationship between sexual behavior and potentially pathogenic bacterial communities inhabiting vital reproductive
structures, as well as their potential effects on fitness, I sought to quantify differences in bacterial diversity in a promiscuous
and monogamous mammal species. To accomplish this, I used two sympatric species of Peromyscus rodents—Peromyscus californicus and Peromyscus maniculatus that differ with regard to the number of sexual partners per individual to test the hypothesis that bacterial diversity should
be greater in the promiscuous P. maniculatus relative to the monogamous P. californicus. As predicted, phylogenetically controlled and operational taxonomic unit-based indices of bacterial diversity indicated
that diversity is greater in the promiscuous species. These results provide important new insights into the effects of mating
system on bacterial diversity in free-living vertebrates, and may suggest a potential cost of promiscuity. 相似文献
565.
INTRODUCTION: This exploratory study investigated the relationship between vision obstructions from body pillars and lane-change crashes. METHODS: The vision obstructions were quantified by measuring, from the driver's perspective, the horizontal angular sizes and locations of the driver-side A-, B-, and C-pillars. The sample consisted of 21 vehicle models, including 13 passenger cars, 6 SUVs, 1 minivan, and 1 pickup truck. To control for driver differences, going-straight crashes were used for comparison, with the dependent variable being the ratio of lane-change crashes to going-straight crashes. The analysis used North Carolina crash data. RESULTS: The results of a multiple regression indicate that the relative frequency of lane-change crashes tended to increase with both wider A-pillars and with A-pillars located farther away from straight ahead. IMPACT ON INDUSTRY: The finding supports the hypothesis that visibility obstructions due to A-pillars have safety implications. 相似文献
566.
Claudio Ottoni Hannah E. C. Koon Matthew J. Collins Kirsty E. H. Penkman Olga Rickards Oliver E. Craig 《Die Naturwissenschaften》2009,96(2):267-278
Evolutionary biologists are increasingly relying on ancient DNA from archaeological animal bones to study processes such as
domestication and population dispersals. As many animal bones found on archaeological sites are likely to have been cooked,
the potential for DNA preservation must be carefully considered to maximise the chance of amplification success. Here, we
assess the preservation of mitochondrial DNA in a medieval cattle bone assemblage from Coppergate, York, UK. These bones have
variable degrees of thermal alterations to bone collagen fibrils, indicative of cooking. Our results show that DNA preservation
is not reliant on the presence of intact collagen fibrils. In fact, a greater number of template molecules could be extracted
from bones with damaged collagen. We conclude that moderate heating of bone may enhance the retention of DNA fragments. Our
results also indicate that ancient DNA preservation is highly variable, even within a relatively recent assemblage from contexts
conducive to organic preservation, and that diagenetic parameters based on protein diagenesis are not always useful for predicting
ancient DNA survival. 相似文献
567.
Timothy J. Foxon Matthew Leach David Butler Joanna Dawes David Hutchinson Peter Pearson David Rose 《Local Environment》1999,4(2):137-149
This paper considers methodological questions concerning indicators of sustainability, which have arisen in the course of an EPSRC-supported project investigating a systems approach to assessing the sustainability of cities. The project aimed: (a) to develop a methodology, the Reference Sustainability System (RSS), for representing the energy, resource and material flows, on which the environmental sustainability of cities depends; (b) to show how this methodology could contribute to a more systematic assessment of the potential of technological and resource management strategies to enhance urban sustainability. Systems models of the material or resource flows caused by the household demand for paper, energy, water and bottled water have been constructed. The project has highlighted the complexity of assessing the contributions of specific technologies and strategies to enhanced sustainability. Particular issues raised include the relative merits and problems of using externality valuation methods compared to physical indicators, the difficulties of aggregating environmental impacts, the question of where system boundaries should be drawn in a life cycle analysis, and the need to consider both distant and local impacts which arise from the end-use demands of urban populations. The paper explores these issues, through the use of modelling results from the case studies. Particular emphasis is placed on the communication of research results to policy makers, interested organisations and the public, drawing on recent experience with the dissemination of results from the project's first case study relating to waste-paper management options. 相似文献
568.
Joakim Hjältén Anna Lindau Anders Wennström Patrik Blomberg Johanna Witzell Lars Ericson 《Chemoecology》2008,18(4):227-231
Summary. There is an increased interest for the use of GM trees in forestry and several commercially promising lines are now available.
However, the ecological implications of the use of GM trees, e.g. effects on non-target natural enemies, have rarely been
explored. The aim of this study was to determine if modification of non-defensive traits in GM poplars unintentionally can
influence plant chemistry in a way that has consequences for palatability to voles. In a greenhouse experiment, we used two
lines, SPS33A and SPS26, of GM hybrid poplars (Populus tremula x tremuloides) with 1.5 and 4 times, respectively, over-expression sucrose-phosphate synthase (SPS). This enzyme plays a central role in
sucrose synthesis, affecting cold acclimation, mesophyll sucrose content and biomass production. As a control we used the
isogenic unmodified wild type. Stems of these poplars were presented to bank voles and field voles in cafeteria experiments.
The concentration of condensed tannins was higher in leaves of lines SPS33A and SPS26 than in the isogenic wild-type and the
concentration of nitrogen was higher in line SPS33A than in both the wild-type and line SPS26. Although the bank voles consumed
slightly less bark from SPS33A, there were no significant differences in the preference of bank vole or field vole for the
different poplar lines. This indicates that the changes in plant chemistry were insufficient to produce any strong herbivore
response or that alteration in tannins and nitrogen counteracted each other. Still, changes in the interactions between mammalian
herbivores and GM trees are important to consider in future cost-benefits analyses of GM trees. 相似文献
569.
Urbanization has profound influences on ecological communities, but our understanding of causal mechanisms is limited by a lack of attention to its component stressors. Published research suggests that at landscape scales, habitat loss and fragmentation are the major drivers of community change, whereas at local scales, human activity and vegetation management are the primary stressors. Little research has focused on whether urbanization stressors may supplant natural factors as dominant forces structuring communities. We used model selection to determine the relative importance of urban development, human activity, local and landscape vegetation, topography, and geographical location in explaining land bird species richness, abundance, and dominance. We analyzed the entire community and groups of species based on ecological characteristics, using data collected in remnant forests along a gradient of urban development in the Lake Tahoe basin, California and Nevada, USA. Urbanization stressors were consistently among the principal forces structuring the land bird community. Strikingly, disturbance from human activity was the most important factor for richness in many cases, surpassing even habitat loss from development. Landscape-scale factors were consistently more important than local-scale factors for abundance. In demonstrating considerable changes in land bird community structure, our results suggest that ecosystem function in urban areas may be severely compromised. Such changes compel local- and landscape-scale management, focused research, and long-term monitoring to retain biodiversity in urban areas to the extent possible. 相似文献
570.
W. Bowman Cutter Matthew Neidell 《Journal of Environmental Economics and Management》2009,58(3):253-265
This paper assesses whether individuals change their transportation choices in response to ‘Spare the Air’ (STA) advisories, a public voluntary information program in the San Francisco Bay Area that elicits reductions in ozone-producing activities. Since STAs are issued when ozone levels are predicted to exceed a particular threshold, we use a regression discontinuity design to identify the effect of STAs. We also use traffic conditions in Southern California, an area without STAs, to estimate difference-in-differences models. The results suggest that STAs reduce traffic volume and slightly increase the use of public transit, supporting a potential role for voluntary information programs that directly target individuals as a means for improving local air quality. 相似文献