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排序方式: 共有817条查询结果,搜索用时 468 毫秒
661.
Guangjian Xu Xiaoxiao Zhong Yangfan Wang Alan Warren Henglong Xu 《Environmental science and pollution research international》2014,21(23):13461-13469
The functional parameters, i.e., the estimated equilibrium species number (S eq ), the colonization rate constant, and the time taken to reach 90 % of S eq (T 90 ), of microperiphyton fauna have been widely used to determine the water quality status in aquatic ecosystems. The objective of this investigation was to develop a protocol for determining functional parameters of microperiphyton fauna in colonization surveys for marine bioassessment based on rarefaction and regression analyses. The temporal dynamics in species richness of microperiphyton fauna during the colonization period was analyzed based on a dataset of periphytic ciliates in Chinese coastal waters of the Yellow Sea. The results showed that (1) based on observed species richness and estimated maximum species numbers, a total of 16 glass slides were required in order to achieve coefficients of variation of <5 % in the functional parameters; (2) the rarefied average species richness and functional parameters showed weak sensitivity to sampling effort; (3) the temporal variations in average species richness were well-fitted to the MacArthur-Wilson model; and (4) the sampling effort of ~8 glass slides was sufficient to achieve coefficients of variation of <5 % in equilibrium average species number (AvS eq ), colonization rate (AvG), and the time to reach 90 % of AvS eq (AvT 90 ) based on the average species richness. The findings suggest that the AvS eq , AvG, and AvT 90 values based on rarefied average species richness of microperiphyton might be used as reliable ecological indicators for the bioassessment of marine water quality in coastal habitats. 相似文献
662.
M. Granger Morgan William R. Rish Samuel C. Morris Alan K. Meier 《Journal of the Air & Waste Management Association (1995)》2013,63(10):993-997
The optimum level of sulfur pollution control for a coal fired power plant is the point where the sum of societal costs, due to pollution, and control costs is minimized. This basic microeconomic concept has been of limited practical value due to considerable uncertainty in estimating both costs. A probabilistic approach is used to characterize these uncertainties quantitatively for a hypothetical 1000 Mwe plant located near Pittsburgh, Pennsylvania. Only mortality effects within a distance of 80 km of the plant have been included. The results allow explicit consideration of attitude toward risk and appropriate level of investment to prevent deaths. Limitations of the findings are discussed. Implications are described for policy based on alternative sets of values and assumptions. 相似文献
663.
Alan S. Kao 《Journal of the Air & Waste Management Association (1995)》2013,63(5):683-696
Current regulatory policies for hazardous air pollutants (HAPs) target the sources of direct emissions. In addition to direct emissions, some of the aromatic, nitrogenated, and oxygenated HAPs can be formed in the atmosphere. Formaldehyde and acetaldehyde, in particular, are produced by almost every hydrocarbon photooxidation reaction. Estimates have been made that, in some urban areas, in situ formation contributes as much as 85 percent of the ambient levels of formaldehyde and 95 percent for acetaldehyde. Over 40 percent of the HAPs being regulated under Title III of the 1990 Clean Air Act Amendments have atmospheric lifetimes of less than one day. The transformation products of these HAPs with low atmospheric persistence are important for assessing risks to human health, especially for cases where the transformation products are more toxic than the HAP itself. 相似文献
664.
Alan R. Leston Will M. Ollison 《Journal of the Air & Waste Management Association (1995)》2017,67(11):1240-1248
Long-standing measurement techniques for determining ground-level ozone (O3) and nitrogen dioxide (NO2) are known to be biased by interfering compounds that result in overestimates of high O3 and NO2 ambient concentrations under conducive conditions. An increasing near-ground O3 gradient (NGOG) with increasing height above ground level is also known to exist. Both the interference bias and NGOG were investigated by comparing data from a conventional Federal Equivalent Method (FEM) O3 photometer and an identical monitor upgraded with an “interference-free” nitric oxide O3 scrubber that alternatively sampled at 2 m and 6.2 m inlet heights above ground level (AGL). Intercomparison was also made between a conventional nitrogen oxide (NOx) chemiluminescence Federal Reference Method (FRM) monitor and a new “direct-measure” NO2 NOx 405 nm photometer at a near-road air quality measurement site. Results indicate that the O3 monitor with the upgraded scrubber recorded lower regulatory-oriented concentrations than the deployed conventional metal oxide–scrubbed monitor and that O3 concentrations 6.2 m AGL were higher than concentrations 2.0 m AGL, the nominal nose height of outdoor populations. Also, a new direct-measure NO2 photometer recorded generally lower NO2 regulatory-oriented concentrations than the conventional FRM chemiluminescence monitor, reporting lower daily maximum hourly average concentrations than the conventional monitor about 3 of every 5 days.
Implications: Employing bias-prone instruments for measurement of ambient ozone or nitrogen dioxide from inlets at inappropriate heights above ground level may result in collection of positively biased data. This paper discusses tests of new regulatory instruments, recent developments in bias-free ozone and nitrogen dioxide measurement technology, and the presence/extent of a near-ground O3 gradient (NGOG). Collection of unbiased monitor inlet height–appropriate data is crucial for determining accurate design values and meeting National Ambient Air Quality Standards. 相似文献
665.
Sasha D. Hafner Felipe Montes C. Alan Rotz Frank Mitloehner 《Atmospheric environment (Oxford, England : 1994)》2010,44(34):4172-4180
Silage on dairy farms has been identified as a major source of volatile organic compound (VOC) emissions. However, rates of VOC emission from silage are not accurately known. In this work, we measured ethanol (a dominant silage VOC) emission from loose corn silage and exposed corn silage particles using wind tunnel systems. Flux of ethanol was highest immediately after exposing loose silage samples to moving air (as high as 220 g m?2 h?1) and declined by as much as 76-fold over 12 h as ethanol was depleted from samples. Emission rate and cumulative 12 h emission increased with temperature, silage permeability, exposed surface area, and air velocity over silage samples. These responses suggest that VOC emission from silage on farms is sensitive to climate and management practices. Ethanol emission rates from loose silage were generally higher than previous estimates of total VOC emission rates from silage and mixed feed. For 15 cm deep loose samples, mean cumulative emission was as high as 170 g m?2 (80% of initial ethanol mass) after 12 h of exposure to an air velocity of 5 m s?1. Emission rates measured with an emission isolation flux chamber were lower than rates measured in a wind tunnel and in an open setting. Results show that the US EPA emission isolation flux chamber method is not appropriate for estimating VOC emission rates from silage in the field. 相似文献
666.
Enhanced phytoextraction of Pb and other metals from artificially contaminated soils through the combined application of EDTA and EDDS 总被引:6,自引:0,他引:6
Chemically enhanced phytoextraction is achieved by the application of chelates to soils. Using pot experiments, the effect of the combined application of EDTA and EDDS on the uptake of Cu, Pb, Zn and Cd by Zea mays L. was studied. Among the tested application ratios of 1:1, 1:2, and 2:1 (EDTA/EDDS), 2:1 of EDTA:EDDS was the most efficient ratio for increasing the concentrations of Cu, Pb, Zn and Cd in the shoots. The combined application of 3.33 mmol kg(-1) soil of EDTA+1.67 mmol kg(-1) soil of EDDS produced 650 mg kg(-1) of Pb in the shoots, which was 2.4 and 5.9 times the concentration of Pb in the shoots treated with 5 mmol kg(-1) of EDTA and EDDS alone, respectively. The total phytoextraction of Pb reached 1710 microg kg(-1) soil, which was 2.1 and 6.1 times the total Pb from 5 mmol kg(-1) EDTA and EDDS alone, respectively. The combined application of EDTA and EDDS also significantly increased the translocation of Pb from the roots to the shoots. The mechanism of enhancing the phytoextraction of Pb by the combined application of EDTA+EDDS did not involve a change in the pH of the soil. The increase in the phytoextraction of Pb by the shoots of Z. mays L. was more pronounced than the increase of Pb in the soil solution with the combined application of EDTA and EDDS. It was thought that the major role of EDDS might be to increase the uptake and translocation of Pb from the roots to the shoots of plants. 相似文献
667.
Steve Carver Ian Convery Sally Hawkins Rene Beyers Adam Eagle Zoltan Kun Erwin Van Maanen Yue Cao Mark Fisher Stephen R. Edwards Cara Nelson George D. Gann Steve Shurter Karina Aguilar Angela Andrade William J. Ripple John Davis Anthony Sinclair Marc Bekoff Reed Noss Dave Foreman Hanna Pettersson Meredith Root-Bernstein Jens-Christian Svenning Peter Taylor Sophie Wynne-Jones Alan Watson Featherstone Camilla Fløjgaard Mark Stanley-Price Laetitia M. Navarro Toby Aykroyd Alison Parfitt Michael Soulé 《Conservation biology》2021,35(6):1882-1893
There has been much recent interest in the concept of rewilding as a tool for nature conservation, but also confusion over the idea, which has limited its utility. We developed a unifying definition and 10 guiding principles for rewilding through a survey of 59 rewilding experts, a summary of key organizations’ rewilding visions, and workshops involving over 100 participants from around the world. The guiding principles convey that rewilding exits on a continuum of scale, connectivity, and level of human influence and aims to restore ecosystem structure and functions to achieve a self-sustaining autonomous nature. These principles clarify the concept of rewilding and improve its effectiveness as a tool to achieve global conservation targets, including those of the UN Decade on Ecosystem Restoration and post-2020 Global Biodiversity Framework. Finally, we suggest differences in rewilding perspectives lie largely in the extent to which it is seen as achievable and in specific interventions. An understanding of the context of rewilding projects is the key to success, and careful site-specific interpretations will help achieve the aims of rewilding. 相似文献
668.
Species reintroduction efforts can improve the recovery of imperiled species, but successful implementation of this conservation strategy requires a thorough understanding of the abiotic and biotic factors influencing species viability. Species interactions are especially understudied, in particular by omitting the effect of imperfect detection on negative, neutral, or positive associations within a community. Using repeat surveys from 5 southern Ontario, Canada, Great Lakes tributaries, we quantified species co-occurrence patterns with the eastern sand darter (ESD) (Ammocrypta pellucida), listed as federally threatened, and characterized how imperfect detection during sampling can influence inference regarding these relationships. We used a probabilistic framework that included 3 approaches of increasing complexity: probabilistic co-occurrence analysis ignoring imperfect detection; single-species occupancy models with subsequent co-occurrence analysis; and 2-species occupancy models. We then used our occupancy models to predict suitable sites for potential future reintroduction efforts while considering the influence of negative species interactions. Based on the observed data, ESD showed several positive associations with co-occurring species; however, species associations differed when imperfect detection was considered. Specifically, a negative association between ESD and rosyface shiner (Notropis rubellus) was observed only after accounting for imperfect detection in the Grand River. Alternatively, positive associations in the Grand River between ESD and northern hogsucker (Hypentelium nigricans) and silver shiner (Notropis photogenis) were observed regardless of whether imperfect detection was accounted for. Our models predicted several potential reintroduction sites for ESD in formerly occupied watersheds with high levels of certainty. Overall, our results demonstrate the importance of investigating imperfect detection and species co-occurrence when planning reintroduction efforts. 相似文献
669.
Environmental and Ecological Statistics - Joint species distribution modeling is attracting increasing attention these days, acknowledging the fact that individual level modeling fails to take into... 相似文献
670.
Application of a scenario-based modeling system to evaluate the air quality impacts of future growth
Jülide Kahyaoğlu-Koračin Scott D. Bassett David A. Mouat Alan W. Gertler 《Atmospheric environment (Oxford, England : 1994)》2009,43(5):1021-1028
The structure and design of future urban development can have significant adverse effects on air pollutant emissions as well as other environmental factors. When considering the future impact of growth on mobile source emissions, we generally model the increase in vehicle kilometers traveled (VKT) as a function of population growth. However, diverse and poorly planned urban development (i.e., urban sprawl) can force higher rates of motor vehicle use and in return increase levels of pollutant emissions than alternative land-use scenarios. The objective of this study is to develop and implement an air quality assessment tool that takes into account the influence of alternative growth and development scenarios on air quality.The use of scenario-based techniques in land use planning has been around since the late 1940s and been tested in many different applications to aid in decision-making. In this study, we introduce the development of an advanced interactive scenario-based land use and atmospheric chemistry modeling system coupled with a GIS (Geographical Information System) framework. The modeling system is designed to be modular and includes land use/land cover information, transportation, meteorological, emissions, and photochemical modeling components. The methods and modularity of the developed system allow its application to both broad areas and applications.To investigate the impact of possible land use change and urbanization, we evaluated a set of alternative future patterns of land use developed for a study area in Southwest California. Four land use and two population variants (increases of 500k and 1M) were considered. Overall, a Regional Low-Density Future was seen to have the highest pollutant emissions, largest increase in VKT, and the greatest impact on air quality. On the other hand, a Three-Centers Future appeared to be the most beneficial alternative future land-use scenario in terms of air quality. For all cases, the increase in population was the main factor leading to the change on predicted pollutant levels. 相似文献