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51.
Joshua Graff Zivin David Zilberman 《Journal of Environmental Economics and Management》2002,43(3):455
In this paper, we develop a model of population level environmental health risk with individuals that are heterogeneous in their susceptibility to environmental toxins. This framework allows us to determine when it is optimal to target vulnerable subgroups of the population with special exposure-reducing treatments. Our analytic results show that the potential economic gains from targeted policies will depend critically on the quality of existing capital, the degree of returns to scale in treatment technologies, and the size and sensitivity of the vulnerable population. An empirical application of the model is extended to the case of cryptosporidium in drinking water supplies. 相似文献
52.
Adaptive introgression as a resource for management and genetic conservation in a changing climate 下载免费PDF全文
Current rates of climate change require organisms to respond through migration, phenotypic plasticity, or genetic changes via adaptation. We focused on questions regarding species’ and populations’ ability to respond to climate change through adaptation. Specifically, the role adaptive introgression, movement of genetic material from the genome of 1 species into the genome of another through repeated interbreeding, may play in increasing species’ ability to respond to a changing climate. Such interspecific gene flow may mediate extinction risk or consequences of limited adaptive potential that result from standing genetic variation and mutation alone, enabling a quicker demographic recovery in response to changing environments. Despite the near dismissal of the potential benefits of hybridization by conservation practitioners, we examined a number of case studies across different taxa that suggest gene flow between sympatric or parapatric sister species or within species that exhibit strong ecotypic differentiation may represent an underutilized management option to conserve evolutionary potential in a changing environment. This will be particularly true where advanced‐generation hybrids exhibit adaptive traits outside the parental phenotypic range, a phenomenon known as transgressive segregation. The ideas presented in this essay are meant to provoke discussion regarding how we maintain evolutionary potential, the conservation value of natural hybrid zones, and consideration of their important role in adaptation to climate. 相似文献
53.
54.
Wang L Hao J He K Wang S Li J Zhang Q Streets DG Fu JS Jang CJ Takekawa H Chatani S 《Journal of the Air & Waste Management Association (1995)》2008,58(8):1057-1069
In the last 10 yr, Beijing has made a great effort to improve its air quality. However, it is still suffering from regional coarse particulate matter (PM10) pollution that could be a challenge to the promise of clean air during the 2008 Olympics. To provide scientific guidance on regional air pollution control, the Mesoscale Modeling System Generation 5 (MM5) and the Models-3/Community Multiscale Air Quality Model (CMAQ) air quality modeling system was used to investigate the contributions of emission sources outside the Beijing area to pollution levels in Beijing. The contributions to the PM10 concentrations in Beijing were assessed for the following sources: power plants, industry, domestic sources, transportation, agriculture, and biomass open burning. In January, it is estimated that on average 22% of the PM10 concentrations can be attributed to outside sources, of which domestic and industrial sources contributed 37 and 31%, respectively. In August, as much as 40% of the PM10 concentrations came from regional sources, of which approximately 41% came from industry and 31% from power plants. However, the synchronous analysis of the hourly concentrations, regional contributions, and wind vectors indicates that in the heaviest pollution periods the local emission sources play a more important role. The implications are that long-term control strategies should be based on regional-scale collaborations, and that emission abatement of local sources may be more effective in lowering the PM10 concentration levels on the heavy pollution days. Better air quality can be attained during the Olympics by placing effective emission controls on the local sources in Beijing and by controlling emissions from industry and power plants in the surrounding regions. 相似文献
55.
基于响应面模型的区域大气污染控制辅助决策工具研发 总被引:4,自引:3,他引:4
基于CMAQ模型结果,利用高维克里金插值算法,建立了排放控制因子与污染物环境浓度的响应面模型(RSM),实现了大气污染可控源排放与复合污染水平的实时函数响应.研究结果显示,RSM对PM2.5的预测结果与CMAQ实际模拟结果的误差在容许范围内(最大误差小于0.20μg.m-3,3.89%).基于所建立的RSM,开发了RSM-VAT区域大气污染控制可视化辅助决策工具.使用RSM-VAT对美国8个典型城市的PM2.5污染状况进行了控制情景分析,通过"可视化展示"和"图表分析"二大模块,输出不同控制情景下的环境污染物浓度的实时响应图、可视化展示和数据分析图表等结果. 相似文献
56.
The effects of landscape fragmentation on nest predation and brood parasitism, the two primary causes of avian reproductive failure, have been difficult to generalize across landscapes, yet few studies have clearly considered the context and spatial scale of fragmentation. Working in two river systems fragmented by agricultural and rural-housing development, we tracked nesting success and brood parasitism in > 2500 bird nests in 38 patches of deciduous riparian woodland. Patches on both river systems were embedded in one of two local contexts (buffered from agriculture by coniferous forest, or adjacent to agriculture), but the abundance of agriculture and human habitation within 1 km of each patch was highly variable. We examined evidence for three models of landscape effects on nest predation based on (1) the relative importance of generalist agricultural nest predators, (2) predators associated with the natural habitats typically removed by agricultural development, or (3) an additive combination of these two predator communities. We found strong support for an additive predation model in which landscape features affect nest predation differently at different spatial scales. Riparian habitat with forest buffers had higher nest predation rates than sites adjacent to agriculture, but nest predation also increased with increasing agriculture in the larger landscape surrounding each site. These results suggest that predators living in remnant woodland buffers, as well as generalist nest predators associated with agriculture, affect nest predation rates, but they appear to respond at different spatial scales. Brood parasitism, in contrast, was unrelated to agricultural abundance on the landscape, but showed a strong nonlinear relationship with farm and house density, indicating a critical point at which increased human habitat causes increased brood parasitism. Accurate predictions regarding landscape effects on nest predation and brood parasitism will require an increased appreciation of the multiple scales at which landscape components influence predator and parasite behavior. 相似文献
57.
Nucleotide variation in cytochrome c oxidase subunit I (COI) was used to examine population structure in three invasive bryozoans: Bugula neritina (Linnaeus, 1758), Watersipora subtorquata (d’Orbigny, 1852), and W. arcuata (Banta, 1969). These species are found on ship hulls and have a short (≤2 days) larval phase. Samples were collected from 1998–2001 at multiple sites in Australia, and in Hong Kong, New Zealand, Hawaii, California, Curaçao, and England. B. neritina is known to include three cryptic species, including species Type S (Davidson and Haygood in Biol Bull 196:273–280, 1999) which occurs on the east and west coasts of the USA. One haplotype recorded previously in the USA, S1, was found to be widespread, occurring throughout Australia and in Hong Kong, Curaçao, Hawaii, and England. W. subtorquata, a Caribbean–Atlantic species which has invaded southern Australia, New Zealand, and California, had low nucleotide diversity in these areas (π=0.0016±0.0014), consisting of three haplotypes connected by one or two nucleotide mutations. W. arcuata, an Eastern-Pacific native, had comparatively high diversity (π=0.0221±0.0115) in introduced populations from Australia and Hawaii. In each species, identical haplotypes were identified on separate coastlines providing evidence of widespread, rather than genetically independent, introductions. The major contrast in nucleotide diversity suggests that different propagule-source models explain introductions. 相似文献
58.
Webb RM Wieczorek ME Nolan BT Hancock TC Sandstrom MW Barbash JE Bayless ER Healy RW Linard J 《Journal of environmental quality》2008,37(3):1145-1157
Pesticide leaching through variably thick soils beneath agricultural fields in Morgan Creek, Maryland was simulated for water years 1995 to 2004 using LEACHM (Leaching Estimation and Chemistry Model). Fifteen individual models were constructed to simulate five depths and three crop rotations with associated pesticide applications. Unsaturated zone thickness averaged 4.7 m but reached a maximum of 18.7 m. Average annual recharge to ground water decreased from 15.9 to 11.1 cm as the unsaturated zone increased in thickness from 1 to 10 m. These point estimates of recharge are at the lower end of previously published values, which used methods that integrate over larger areas capturing focused recharge in the numerous detention ponds in the watershed. The total amount of applied and leached masses for five parent pesticide compounds and seven metabolites were estimated for the 32-km2 Morgan Creek watershed by associating each hectare to the closest one-dimensional model analog of model depth and crop rotation scenario as determined from land-use surveys. LEACHM parameters were set such that branched, serial, first-order decay of pesticides and metabolites was realistically simulated. Leaching is predicted to be greatest for shallow soils and for persistent compounds with low sorptivity. Based on simulation results, percent parent compounds leached within the watershed can be described by a regression model of the form e(-depth) (a ln t1/2-b ln K OC) where t1/2 is the degradation half-life in aerobic soils, K OC is the organic carbon normalized sorption coefficient, and a and b are fitted coefficients (R2 = 0.86, p value = 7 x 10(-9)). 相似文献
59.
Poultry litter treatment with alum (Al(2)(SO(4))(3) . 18H(2)O) lowers litter phosphorus (P) solubility and therefore can lower litter P release to runoff after land application. Lower P solubility in litter is generally attributed to aluminum-phosphate complex formation. However, recent studies suggest that alum additions to poultry litter may influence organic P mineralization. Therefore, alum-treated and untreated litters were incubated for 93 d to assess organic P transformations during simulated storage. A 62-d soil incubation was also conducted to determine the fate of incorporated litter organic P, which included alum-treated litter, untreated litter, KH(2)PO(4) applied at 60 mg P kg(-1) of soil, and an unamended control. Liquid-state (31)P nuclear magnetic resonance indicated that phytic acid was the only organic P compound present, accounting for 50 and 45% of the total P in untreated and alum-treated litters, respectively, before incubation and declined to 9 and 37% after 93 d of storage-simulating incubation. Sequential fractionation of litters showed that alum addition to litter transformed 30% of the organic P from the 1.0 mol L(-1) HCl to the 0.1 mol L(-1) NaOH extractable fraction and that both organic P fractions were more persistent in alum-treated litter compared with untreated litter. The soil incubation revealed that 0.1 mol L(-1) NaOH-extractable organic P was more recalcitrant after mixing than was the 1.0 mol L(-1) HCl-extractable organic P. Thus, adding alum to litter inhibits organic P mineralization during storage and promotes the formation of alkaline extractable organic P that sustains lower P solubility in the soil environment. 相似文献
60.
Joshua C. Galster Frank J. Pazzaglia Dru Germanoski 《Journal of the American Water Resources Association》2008,44(4):948-960
Abstract: Land use in a watershed is commonly held to exert a strong influence on trunk channel form and process. Land use changes act over human time‐scales, which are short enough to measure effects on channels directly using historic aerial photographs. We show that high‐resolution topographic surveys for the channels of paired watersheds in the Lehigh Valley, Pennsylvania, are comparable, but have channel widths that have changed dramatically in the past five decades. The two watersheds, Little Lehigh Creek and Sacony Creek, are similar in most aspects except in their respective amount of urban land use. Aerial photographs of the urbanized Little Lehigh Creek show that a majority of the measured widths (67 of 85) were statistically wider in 1999 than in 1947. In contrast, the measured widths from the agricultural Sacony Creek are more evenly distributed among those that widened (18), narrowed (28), and those that were statistically unchanged (6) from 1946 to 1999. From 1946 to 1999 the only section of Sacony Creek that widened was that reach downstream of the only sizable urban area in the watershed. The current land use in Sacony Creek watershed resembles that of 1946, while the Little Lehigh Creek watershed has more than tripled its urban area. These data, in concert with other recent hydrologic data from the watersheds suggest that the increase in urban area‐generated peak discharges is the mechanism behind the widening that occurred in the Little Lehigh Creek. These wider channels can affect water quality, aquatic habitat, suspended sediment loads, and river esthetics. 相似文献