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排序方式: 共有236条查询结果,搜索用时 62 毫秒
231.
Steven H. Cadle Robert A. Gorse Jr. Brent K. Bailey 《Journal of the Air & Waste Management Association (1995)》2013,63(2):278-291
ABSTRACT In April 1999, the Coordinating Research Council sponsored a workshop focusing on our understanding of real-world emissions from motor vehicles. This summary presents the latest information on in-use light- and heavy-duty vehicle tailpipe and evaporative emissions, the effects of fuels on emissions, field programs designed to understand the contribution of mobile sources to emission inventories, efforts to evaluate and improve mobile source emission models, progress of vehicle inspection/ maintenance programs, and topics for future research. While significant progress has been made in understanding in-use vehicle emissions, further improvements are necessary. Moreover, the impact of current and future changes in emission control technologies and control programs will have to be monitored for effectiveness and incorporated into the emission factor models. 相似文献
232.
Stefanie Ebelt Sarnat Brent A. Coull Pablo A. Ruiz Petros Koutrakis Helen H. Suh 《Journal of the Air & Waste Management Association (1995)》2013,63(2):186-196
Abstract Particle infiltration is a key determinant of the indoor concentrations of ambient particles. Few studies have examined the influence of particle composition on infiltration, particularly in areas with high concentrations of volatile particles, such as ammonium nitrate (NH4NO3). A comprehensive indoor monitoring study was conducted in 17 Los Angeles–area homes. As part of this study, indoor/outdoor concentration ratios during overnight (nonindoor source) periods were used to estimate the fraction of ambient particles remaining airborne indoors, or the particle infiltration factor (FINF), for fine particles (PM2.5), its nonvolatile (i.e., black carbon [BC]) and volatile (i.e., nitrate [NO3 ?]) components, and particle sizes ranging between 0.02 and 10 μm. FINF was highest for BC (median = 0.84) and lowest for NO3 ? (median = 0.18). The low FINF for NO3 ? was likely because of volatilization of NO3 ? particles once indoors, in addition to depositional losses upon building entry. The FINF for PM2.5 (median = 0.48) fell between those for BC and NO3 ?, reflecting the contributions of both particle components to PM2.5. FINF varied with particle size, air-exchange rate, and outdoor NO3 ? concentrations. The FINF for particles between 0.7 and 2 μm in size was considerably lower during periods of high as compared with low outdoor NO3 ? concentrations, suggesting that outdoor NO3 ? particles were of this size. This study demonstrates that infiltration of PM2.5 varies by particle component and is lowest for volatile species, such as NH4NO3. Our results suggest that volatile particle components may influence the ability for outdoor PM concentrations to represent indoor and, thus, personal exposures to particles of ambient origin, because volatilization of these particles causes the composition of PM2.5 to differ indoors and outdoors. Consequently, particle composition likely influences observed epidemiologic relationships based on outdoor PM concentrations, especially in areas with high concentrations of NH4NO3 and other volatile particles. 相似文献
233.
Persistent organic pollutants (POPs), xenobiotics that accumulate in fat tissue, may impair bone metabolism. We studied (1) the association of bone mineral density (BMD) with POPs and (2) whether associations of fat mass (FM) or lean mass (LM), two components of body composition, with BMD differed depending on levels of POPs. Participants aged ?20 in the National Health and Nutrition Examination Survey 1999-2004 were included (n = 2769). Eight POPs with detection rate ?80% and three skeletal subregions (left arm, pelvis, and right leg) were selected. All analyses were stratified by gender and age (cutpoint 50 years or more). POPs at background concentrations were mostly unassociated with BMD. However, the associations of FM and LM with BMD depended on POPs concentrations, in particular with BMD of the left arm (usually not weight-bearing) in postmenopausal women. When POPs concentrations were low, FM showed inverse associations with BMD while LM showed positive associations. However, when POPs levels were high, FM showed positive associations with BMD while the positive associations between LM and BMD weakened. POPs may biologically modify the associations of FM and LM with BMD, especially among postmenopausal women, possibly explaining inconsistent associations between FM and BMD in previous epidemiological studies. 相似文献
234.
Conservation of Mammals in Eastern North American Wildlife Reserves: How Small Is Too Small? 总被引:6,自引:0,他引:6
Abstract: A common objective of methods of systematic reserve selection has been to maximize conservation benefits—frequently current species richness—while reducing the costs of acquiring and maintaining reserves. But the probability that a reserve will lose species in the future is frequently not known because the minimum area requirements for most species have not been estimated empirically. For reserves within the Alleghenian-Illinoian mammal province of eastern North America, we empirically estimated the minimum area requirement of terrestrial mammals such that reserves should not lose species because of insularization. We compared this estimate to the actual size of 2355 reserves and reserve assemblages within the mammal province. The estimated minimum area requirement was 5037 km2 (95% CI: 2700–13,296 km2 ). Fourteen reserves and reserve assemblages were> 2700 km2 , 9 were> 5037 km2 , and 3 were> 13,296 km2 . These 14 reserves accounted for 73% of the total area of reserves and 10% of the total area of the mammal province. Few reserves appear large enough to avoid loss of some mammal species without the additional cost of active management of habitat or populations. Immigration corridors and buffer zones that combine small reserves into assemblages totaling at least 2700 km2 may be the most efficient means of conserving mammals in these reserves. 相似文献
235.
With increasing environmental issues and depleting resources, the effective application of green government procurement (GGP) is urgently needed and potentially can have greater impacts in the developing world rather than in the developed world. Such an approach can help promote the general goal of sustainable development and address environmental issues through purchasing and facilitating the use of environmentally friendly services and products. This paper addresses this issue by employing a case study on China. We first trace the development of the GGP concept, its spread to Asian countries, and a number of approaches used to expand GGP adoption. We then review current practices in China on GGP, and analyze and identify some of the current barriers and problems in promoting green procurement in the Chinese governmental sector. We finally seek to identify possible appropriate capacity-building solutions, in order to facilitate the application of GGP in China. 相似文献
236.
Gregory G. Turner Brent J. Sewall Michael R. Scafini Thomas M. Lilley Daniel Bitz Joseph S. Johnson 《Conservation biology》2022,36(2):e13803
White-nose syndrome (WNS) is a fungal disease that has caused precipitous declines in several North American bat species, creating an urgent need for conservation. We examined how microclimates and other characteristics of hibernacula have affected bat populations following WNS-associated declines and evaluated whether cooling of warm, little-used hibernacula could benefit bats. During the period following mass mortality (2013–2020), we conducted 191 winter surveys of 25 unmanipulated hibernacula and 6 manipulated hibernacula across Pennsylvania (USA). We joined these data with additional datasets on historical (pre-WNS) bat counts and on the spatial distribution of underground sites. We used generalized linear mixed models and model selection to identify factors affecting bat populations. Winter counts of Myotis lucifugus were higher and increased over time in colder hibernacula (those with midwinter temperatures of 3–6 °C) compared with warmer (7–11 °C) hibernacula. Counts of Eptesicus fuscus, Myotis leibii, and Myotis septentrionalis were likewise higher in colder hibernacula (temperature effects = –0.73 [SE 0.15], –0.51 [0.18], and –0.97 [0.28], respectively). Populations of M. lucifugus and M. septentrionalis increased most over time in hibernacula surrounded by more nearby sites, whereas Eptesicus fuscus counts remained high where they had been high before WNS onset (pre-WNS high count effect = 0.59 [0.22]). Winter counts of M. leibii were higher in hibernacula with high vapor pressure deficits (VPDs) (particularly over 0.1 kPa) compared with sites with lower VPDs (VPD effect = 15.3 [4.6]). Counts of M. lucifugus and E. fuscus also appeared higher where VPD was higher. In contrast, Perimyotis subflavus counts increased over time in relatively warm hibernacula and were unaffected by VPD. Where we manipulated hibernacula, we achieved cooling of on average 2.1 °C. At manipulated hibernacula, counts of M. lucifugus and P. subflavus increased over time (years since manipulation effect = 0.70 [0.28] and 0.51 [0.15], respectively). Further, there were more E. fuscus where cooling was greatest (temperature difference effect = –0.46 [SE 0.11]), and there was some evidence there were more P. subflavus in hibernacula sections that remained warm after manipulation. These data show bats are responding effectively to WNS through habitat selection. In M. lucifugus, M. septentrionalis, and possibly P. subflavus, this response is ongoing, with bats increasingly aggregating at suitable hibernacula, whereas E. fuscus remain in previously favored sites. Our results suggest that cooling warm sites receiving little use by bats is a viable strategy for combating WNS. 相似文献