The relationship between emissions and deposition of air pollutants, both spatially and in time forms an important focus for science and for policy makers. In practice, this relationship may become nonlinear if the underlying processes change with time, or in space. Nonlinearities may also appear due to errors in emission or deposition data, and careful scrutiny of both data sources and their relationship provides a means of picking up such deficiencies. Nonlinearities in source receptor relationships for sulfur and nitrogen compounds in Europe have been identified in measurement data for the UK. In the case of sulfur, the dry deposition process has been shown to be strongly influenced by ambient concentrations of NH3, leading to substantial increases in deposition rate as SO2 concentrations decline and the ratio SO2/NH3 decreases. The field evidence extends to measurements over three different surfaces in three countries across Europe. A mechanistic understanding of the cause of this nonlinearity has been provided. Apparent nonlinearities also exist in the sulfur deposition field through the influence of shipping emissions. The effect is clear at west coast locations, where during a period in which land-based sulfur emissions declined by 50%, no significant decline in concentrations of SO(2-) in precipitation were observed. The sites affected are primarily the coastal regions of southwestern UK, where shipping sources contribute a substantial fraction of the deposited sulfur, but the effect is not detectable elsewhere. Full quantification of the spatially disaggregated emission and their changes in time will eliminate this apparent nonlinearity in the source-receptor data. For oxidized nitrogen emission and deposition in the UK, there is strong evidence of nonlinearity in the source-receptor relationship. The concentrations and deposition of NO(3-) in precipitation have declined little following a reduction in emissions of 45% during the period 1987 to 2001. The data imply a significant decrease in the average transport distance for oxidized nitrogen and most probably an increase in the average oxidation rate. However, the net effect of changes in aerosol chemistry due to changes in sulfur emissions and less competition for the main oxidants as a consequence of reductions in sulfur emission have not been separated. A quantitative explanation of the cause of this nonlinearity is lacking and the effects are therefore identified as an important uncertainty for the development of further protocols to control acidification, eutrophication and photochemical oxidants in Europe. 相似文献
Concentrations of air pollutants were monitored during the May November 1999 period on a network of forested sites in Sequoia National Park, California. Measurements were conducted with: (1) active monitors for nitric oxide (NO), nitrogen dioxide (NO2) and ozone (O3); (2) honeycomb denuder/filter pack systems for nitric acid vapor (HNO3), nitrous acid vapor (HNO2), ammonia (NH3), sulfur dioxide (SO2), particulate nitrate (NO3-), ammonium (NH4+), and sulfate (SO4(2-)); and (3) passive samplers for O3, HNO3 and NO2. Elevated concentrations of O3 (seasonal means 41-71 ppb), HNO3 (seasonal means 0.4-2.9 microg/m3), NH3 (seasonal means 1.6-4.5 microg/m3), NO3 (1.1-2.0 microg/m3) and NH4+ (1.0-1.9 microg/m3) were determined. Concentrations of other pollutants were low. With increasing elevation and distance from the pollution source area of O3, NH3 and HNO3 concentrations decreased. Ammonia and NH4+ were dominant N pollutants indicating strong influence of agricultural emissions on forests and other ecosystems of the Sequoia National Park. 相似文献
In spite of increasing efforts to reduce nitrogen inputs into groundwater from intensive agriculture, nitrate (NO3) remains one of the major pollutants of drinking-water resources worldwide. Determining the source(s) of NO3 contamination in groundwater is an important first step for improving groundwater quality by emission control, and it is with this aim that we investigated the viability of an isotopic multi-tracer approach (delta15N, delta11B, 87Sr/86Sr), in addition to conventional hydrogeologic analysis, in two small catchments of the Arguenon watershed (Brittany, France). The main anthropogenic sources (fertilizer, sewage effluent, and hog, cattle and poultry manure) were first characterized by their specific B, N and Sr isotope signatures, and compared to those observed in the ground- and surface waters. Chemical and isotopic evidence shows that both denitrification and mixing within the watershed have the effect of buffering NO3 contamination in the groundwater. Coupled delta11B, delta15N and 87Sr/86Sr results indicate that a large part of the NO3 contamination in the Arguenon watershed originates from the spreading of animal manure, with hog manure being a major contributor. Point sources, such as sewage effluents, contribute to the NO3 budget of the two watersheds. 相似文献
The properties of sludges from a pilot-scale submerged membrane bioreactor (SMBR) and two bench-scale complete-mix, activated sludge (CMAS) reactors treating municipal primary effluent were determined. Compared with the CMAS sludges, the SMBR sludge contained a higher amount of soluble microbial products (SMP) and colloidal material attributed to the use of a membrane for solid-liquid separation; a higher amount nocardioform bacteria, resulting from efficient foam trapping; and a lower amount of extracellular polymeric substances (EPS), possibly because there was no selective pressure for the sludge to settle. High aeration rates in both the CMAS and SMBR reactors produced sludges with higher numbers of smaller particles. Normalized capillary suction time values for the SMBR sludge were lower than for the CMAS sludges, possibly because of its lower EPS content. 相似文献
A polyphasic approach based on cultivation and direct recovery of 16S rRNA gene sequences was utilized for microbial characterization of an aquifer contaminated with chlorinated ethenes. This work was conducted in order to support the evaluation of natural attenuation of chlorinated ethenes in groundwater at Area 6 at Dover Air Force Base (Dover, DE). Results from these studies demonstrated the aquifer contained relatively low biomass (e.g. direct microscopic counts of < 10(7) bacteria/g of sediment) comprised of a physiologically diverse group of microorganisms including iron reducers, acetogens, sulfate reducers, denitrifiers, aerobic and anaerobic heterotrophs. Laboratory microcosms prepared with authentic sediment and groundwater provided direct microbiological evidence that the mineralization of vinyl chloride and cis-dichloroethene as well as each step in the complete reductive dechlorination of tetracloroethene to ethene can occur in the Area 6 aquifer. Enrichment cultures capable of the oxidative degradation of cis-1,2-dichloroethene (cis-DCE) and vinyl chloride (VC) were obtained from groundwater across the aquifer demonstrating the possible importance of direct, non-cometabolic oxidation of cis-DCE and VC in natural attenuation. Culture-independent analyses based upon recovery of 16S rRNA gene sequences revealed the presence of anaerobic organisms distributed primarily between two major bacterial divisions: the delta subdivision of the Proteobacteria and low-G + C gram positive. Recovery of sequences affiliated with phylogenetic groups containing known anaerobic-halorespiring organisms such as Desulfitobacterium, Dehalobacter, and certain groups of iron reducers provided qualitative support for a role of reductive dechlorination processes in the aquifer. This molecular data is suggestive of a functional linkage between the microbiology of the site and the apparent natural attenuation process. The presence and distribution of microorganisms were found to be consistent with a microbially driven attenuation of chlorinated ethenes within the aquifer and in accord with a conceptual model of aquifer geochemistry which suggest that both reductive and oxidative mechanisms are involved in heterogeneous, spatially distributed processes across the aquifer. 相似文献
Oxidation of pyrite at the Nopal I uranium deposit, Peña Blanca district, Chihuahua, Mexico has resulted in the formation of Fe-oxides/hydroxides. Anomalous U concentrations (i.e. several hundred to several thousand ppm) measured in goethite, hematite, and amorphous Fe-oxyhydroxides in a major fracture that crosscuts the deposit and the absence of U minerals in the fracture suggest that U was retained during secondary mineral growth or sorbed on mineral surfaces. Mobilization and transport of U away from the deposit is suggested by decreasing U concentrations in fracture-infilling materials and in goethite and hematite with distance from the deposit. Greater than unity 234U/238U activity ratios measured in fracture-infilling materials indicate relatively recent ( < 1 Ma) U uptake from fluids that carried excess 234U. Systematic decreases in 234U/238U activity ratios of fracture materials with distance from the deposit suggest a multistage mobilization process, such as remobilization of U from 234U-enriched infill minerals or differential or diminished transport of U-bearing solutions containing excess 234U. 相似文献
We evaluated the genotoxicity of dichloromethane (DCM) extracts of PCB-contaminated soil before and after the soil had been treated by a base-catalyzed dechlorination process. The treatment process involves heating a mixture of the soil, polyethylene glycol (or hydrocarbons with boiling points of 310–387°C), and sodium hydroxide to 250–350°C. Dechlorination reduced by >99% the PCB concentration of the soil, which was initially 2,200 ppm. The DCM extracts of both control and treated soils were not mutagenic in strain TA100 of Salmonella, but they were mutagenic in strain TA98. Based on results in strain TA98, the base-catalyzed dechlorination process reduced the mutagenic potency of the soil by approximately one-half. The DCM extracts of the soils before and after treatment were equally genotoxic in a prophage-induction assay in
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, which detects some chlorinated organic carcinogens that are not detected by the Salmonella mutagenicity assay. These results suggest that treatment of PCB-contaminated soil by base-catalyzed dechlorination reduced the mutagenicity of the soil slightly. 相似文献
The recent dispute over the impact of economic growth on the environment relative to the (predicted) physical limits imposed by the ecological system hinges on the role of pollution-preventive technology. This paper attempts a cost-effectiveness evaluation of alternative methods of preventing the largest source of marine oil pollution. The first major result of the analysis is that the technology which minimizes internal costs (and is favored by the oil companies) does not minimize the social costs of pollution prevention. The second is that relative to the price of oil the cost of pollution-prevention processes is very small indeed. 相似文献
Objective: A large portion of child restraint systems (car seats) are installed incorrectly, especially when first-time parents install infant car seats. Expert instruction greatly improves the accuracy of car seat installation but is labor intensive and difficult to obtain for many parents. This study was designed to evaluate the efficacy of 3 ways of communicating instructions for proper car seat installation: phone conversation; HelpLightning, a mobile application (app) that offers virtual interactive presence permitting both verbal and interactive (telestration) visual communication; and the manufacturer's user manual.
Methods: A sample of 39 young adults of child-bearing age who had no previous experience installing car seats were recruited and randomly assigned to install an infant car seat using guidance from one of those 3 communication sources.
Results: Both the phone and interactive app were more effective means to facilitate accurate car seat installation compared to the user manual. There was a trend for the app to offer superior communication compared to the phone, but that difference was not significant in most assessments. The phone and app groups also installed the car seat more efficiently and perceived the communication to be more effective and their installation to be more accurate than those in the user manual group.
Conclusions: Interactive communication may help parents install car seats more accurately than using the manufacturer's manual alone. This was an initial study with a modestly sized sample; if results are replicated in future research, there may be reason to consider centralized “call centers” that provide verbal and/or interactive visual instruction from remote locations to parents installing car seats, paralleling the model of centralized Poison Control centers in the United States. 相似文献