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851.
Ralph I. Larsen Thomas R. McCurdy Pamela M. Johnson Walter W. Heck 《Journal of the Air & Waste Management Association (1995)》2013,63(12):1497-1503
Soybean percent crop reduction was estimated as a function of ambient O3 concentrations for each of 80 agricultural sites in the National Aerometric Data Bank (NADB) for each available year of data for years 1981-1985. Fourteen O3 concentration statistics were calculated for each of the resulting 320 site-years of data. The two statistics that correlated best with estimated crop reduction were an effective mean O3 concentration (1 percent of variance unexplained) and an arithmetic mean O3 concentration (4 percent unexplained). The worst correlation of the 14 was for the statistic used in the present O3 National Ambient Air Quality Standard (NAAQS), the second highest daily maximum 1-h O3 concentration (42 percent unexplained). The number of site-years for estimated percent soybean yield reductions was plotted versus increasing O3 concentrations for each of the 14 O3 statistics. A maximum crop reduction line was drawn on each plot. These lines were used to estimate (and list) potential ambient O3 standards for each of the 14 statistics that would limit soybean crop reduction at agricultural. NADB sites to 5, 10, 15, or 20 percent. 相似文献
852.
The diamondback terrapin’s (Malaclemys terrapin) wide geographic distribution, long life span, occurrence in a variety of habitats within the saltmarsh ecosystem, predatory foraging behavior, and high site fidelity make it a useful indicator species for contaminant monitoring in estuarine ecosystems. In this study fat biopsies and plasma samples were collected from males and females from two sites within Barnegat Bay, New Jersey, as well as tissues from a gravid female and blue mussels (Mytilus edulis), which are terrapin prey. Samples were analyzed for persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), chlorinated pesticides, and methyl-triclosan. Terrapins from the northern site, Spizzle Creek, closest to influences from industrial areas, had higher POP concentrations for both tissues than terrapins from the less impacted Forsythe National Wildlife Refuge. Sex differences were observed with males having higher contaminant concentrations in fat and females in plasma. PCB patterns in terrapin fat and plasma were comparable to other wildlife. An atypical PBDE pattern was observed, dominated by PBDEs 153 and 100 instead of PBDEs 47 and 99, which has been documented in only a few other turtle species. The typical PBDE patterns measured in mussels, terrapin prey, suggests that the terrapin may efficiently biotransform or eliminate PBDE 47 and possibly PBDE 99. Plasma contaminant concentrations significantly and positively correlated with those in fat. This study addresses several aspects of using the terrapin as an indicator species for POP monitoring: site and sex differences, tissue sampling choices, maternal transfer, and biomagnification. 相似文献
853.
For decades, toxaphene had been used as a major chloropesticide. Degradation of the multicomponent mixture in the environment was mainly reported to be due to anaerobic dechlorination and hydrodechlorination. Little was known about oxidative transformation processes and the potential hydroxylated metabolites were not available as standard compounds. For this reason we synthesized hydroxylated polychlorobornanes by the UV-induced photochlorination of 2-endo-bornyl acetate with sulfuryl chloride followed by hydrolysis of the acetate moiety. The released polychlorinated 2-endo-hydroxybornanes were slightly higher chlorinated the longer the reaction was maintained. After 8 h, the main products were pentachlorinated hydroxybornanes followed by hexa- and heptachlorinated homologues. Traces of octachlorinated hydroxybornanes were also observed. The GC/ECNI-MS spectra of the products were characterized by the molecular ions and the [M-Cl]− fragment ions. The molecular ions of the polychlorinated hydroxybornanes are isobaric with those of polychlorinated biphenyls. E.g. hexachlorohydroxybornanes (C10H12Cl6O) and hexachlorobiphenyls (C12H4Cl6) show the molecular ion at m/z 358. Based on fractionation experiments on silica with the synthesis products it might be possible that OH-CTTs if present in samples will elute into a more polar fraction usually discarded or not collected. Both problems might explain why these compounds have not been more frequently described in the scientific literature. 相似文献
854.
Vishal K. Mehta M. Todd Walter Erin S. Brooks Tammo S. Steenhuis Michael F. Walter Mark Johnson Jan Boll Dominique Thongs 《Environmental Modeling and Assessment》2004,9(2):77-89
Very few hydrological models commonly used in watershed management are appropriate for simulating the saturation excess runoff. The Soil Moisture Routing model (SMR) was developed specifically to predict saturation excess runoff from variable source areas, especially for areas where shallow interflow controls saturation. A recent version of SMR was applied to two rural catchments in the Catskill Mountains to evaluate its ability to simulate the hydrology of these systems. Only readily available meteorological, topographical, and landuse information from published literature and governmental agencies was used. Measured and predicted streamflows showed relatively good agreement; the average Nash–Sutcliffe efficiency for the two watersheds were R
2=72% and R
2=63%. Distributed soil moisture contents and the locations of hydrologically sensitive areas were also predicted well. 相似文献
855.
856.
857.
Terry V.Callaghan Lars Olof Bjrn Yuri Chernov Terry Chapin Torben R.Christensen Brian Huntley Roll A.Ims Margareta Johansson Dyanna Jolly Sven Jonasson Nadya Matveyeva Nicolai Panikov Walter Oechel Gus Shaver Sibyll Schaphoff Stephen Sitch Christoph Zckler 《Ambio-人类环境杂志》2004,33(7):445-449
在评价北极陆地生态系统影响时,人们常常强调物种和生态系统对环境变化响应的地理变化,这种变化往往与气候、生物多样性、植被带、生态系统结构和功能的南-北梯度相关联,可是,环境、生态系统的功能和结构上,以及环境史和当前气候变化的明显东-西变化显然也很重要.尽管一些地方变得温暖,但另一些地方却降温了,海洋、群岛和山脉等地理屏障的东西差异过去也对物种和植被带响应气候变化而改变分布区的能力产生了很大影响,同时,这些地理屏障为种群遗传分化和生物多样性热点区的形成提供了必要的隔离条件,这些屏障在未来气候变暖时,也将影响物种重新分布的能力.为了说明这种东西向的变化,同时也避免过分笼统或过于专业化,基于大尺度的天气和气候形成因素,北极气候影响评价项目确定了4个主要亚区.通过模拟与4个北极气候影响评价亚区有关的主要信息,导致物种分布区发生改变的地理屏障,特别是大陆的分布和海洋产生的隔离,明显会影响植被带的向北移动.对植被区向北移动的地理限制或者促进将影响将来碳的贮存和释放,以及生物圈与大气之间水和能量的交换.此外,气候变化使受威胁物种数量在各个亚区之间差别很大(白令海地区别尤其是热点),各个植被亚区重新分布的能力差异将影响每个区的生物多样性.总而言之,亚区分析表明,在整个北极地区水平上概括生态系统结构和功能的反应、物种的丧失,以及生物圈对气候系统的反馈的趋势是困难的,说明需要对北极陆地生态系统对于气候变化响应的空间变化性有深刻的认识. 相似文献
858.
The 19th century and first half of the 20th century is one of those periods in history of rapid economical, technical and social changes. There is an ongoing mechanization, followed by a movement to rationalize production and to make it cost effective. This has created a heavy burden of occupational deaths amongst workers. In this period occupational safety is developing into a professional field. Engineers are enclosing hazards and fencing heights, shaping up safety technique, and writing very practical publications on occupational safety. These publications, predominantly published in the United States, are leading to quite some safety related metaphors, with the iceberg and the domino’s as the most famous ones. Sociologists, psychologists, and physicians are more concerned with questions related to accident causation, and these specialists are conducting research leading to two different safety theories. Causes of occupational accident are found either in the workers’ capacity to handle hazardous situations, or in external causes, like very long working hours, dangerous machines and the increased pressures of work and speed of production. The Pittsburgh survey, the first extended analysis of occupational accidents in a steel district, strongly advocated the environmental hypothesis, while the so-called ‘individual hypothesis’ is favored by the American Safety First Movement, starting as a private initiative in 1906 by US Steel, and later spreading out over Western European countries. The British Industrial Fatigue Board has given the individual hypothesis its scientific justification. Despite scientific criticism just after World War II on the concept of accident proneness and ‘unsafe acts’, its popularity is not fading. Even nowadays the famous metaphors are still part of the vocational training of safety experts, also in The Netherlands. Apparently professional and scientific developments in occupational safety are belonging to two separate worlds. Before World War II, The Netherlands is not a leading country in occupational safety but a follower, first of France and the German speaking countries. After World War I its focus is directed towards the Anglo-Saxon countries. 相似文献
859.
Walter W. Zwirner 《Environmental monitoring and assessment》1991,17(2-3):247-252
Sampling inference is proposed as an alternate paradigm. This method is discussed with respect to classical, Bayesian and a proposed probabilistic real world system. A probabilistic real world system is suggested as more valid and useful in practical as well as research situations. Sampling inference applied to a probabilistic model allows for valid inferences for volunteer and representative as well as random samples. A concept of time and distance based samples is introduced. 相似文献
860.
Su Sponaugle Kristen D. Walter Kelly L. Denit Joel K. Llopiz Robert K. Cowen 《Marine Biology》2010,157(4):839-849
Atlantic blue marlin (Makaira nigricans) and sailfish (Istiophorus platypterus) larvae were collected from 10 monthly cruises (June–October 2003 and 2004) across the Straits of Florida to test (1) whether
growth differed between the more productive western region near the Florida shelf, and the less productive eastern region
toward the Bahamas, and (2) whether growth was related to prey consumption. Examination of larval sagittal otoliths revealed
that instantaneous growth and daily growth during the first 2–3 weeks of life did not vary significantly between the two regions
for either species. However, recent growth during the last two full days prior to collection was greater in the west for blue
marlin larvae. Recent growth of blue marlin larvae <9 mm SL (primarily zooplanktivorous) was significantly related to prey
composition (faster growth when higher proportions of Farranula copepods were consumed). Western larvae grew faster and had higher proportions of Farranula in their guts. Trends for sailfish larvae were not significant. In both species, comparison of early growth between <9 and ≥9 mm
SL size groups indicated that growth trajectories diverged around 5–8 mm SL, the time when billfish larvae become capable
of piscivory. Significantly faster growth of larger (older) larvae suggests that mortality was selective for fast growers
and that the transition to piscivory may be a critical point in the early life of billfish. 相似文献