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排序方式: 共有418条查询结果,搜索用时 93 毫秒
1.
Field-grown black cherry (Prunus serotina Ehrh.) seedlings were treated with the antioxidant ethylenediurea (EDU) to evaluate height, diameter, and above-ground dry-weight biomass growth response to ambient ozone over four years. Nine blocks with 44 trees/block were used in a randomized complete block design with three foliar spray treatments: (1) 1000 ppm EDU mixed with a surfactant and water; (2) surfactant mixed with water; and (3) water only. In each growing season treatments were applied seven times at approximately 10-day intervals. Repeated measures analysis of variance indicated significant (P< or =0.05) treatment and year effects for log-transformed height and diameter growth over the four-year period. After four years, EDU-treated trees were approximately 17% taller and stem diameters were 21% greater than non-EDU-treated trees. Total above-ground dry-weight biomass at the end of four years was 47% greater for EDU-treated trees compared to non-EDU-treated trees. 相似文献
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The various analytical protocols that have been developed to aid the measurement of nitrite within environmental samples have been critically appraised and their applicability to field measurement assessed. The present communication presents a perspective on current techniques and technologies encompassing spectroscopic, electrochemical and chromatographic methodologies and highlights those that are liable to emerge in the near future. Commercial devices have been included and where appropriate the advantages and limitations posed by their operation within field contexts have been described. 相似文献
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The purpose of this study was to examine the factor structure of the transformational leadership model in human service teams. As the nature of this work environment mandates certain management‐by‐exception practices, patterns of correlations between perceptions of active and passive management‐by‐exception behaviors and transformational, transactional, and laissez‐faire leadership were of interest. 236 leaders and 620 subordinates from 54 mental health teams completed the Multifactor Leadership Questionnaire, form 8Y. Results suggest that active and passive management‐by‐exception factors are independent constructs. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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Gary M. Bucciarelli Daniel Suh Avery Davis Lamb Dave Roberts Debra Sharpton H. Bradley Shaffer Robert N. Fisher Lee B. Kats 《Conservation biology》2019,33(1):122-131
Introductions of non-native predators often reduce biodiversity and affect natural predator–prey relationships and may increase the abundance of potential disease vectors (e.g., mosquitoes) indirectly through competition or predation cascades. The Santa Monica Mountains (California, U.S.A.), situated in a global biodiversity hotspot, is an area of conservation concern due to climate change, urbanization, and the introduction of non-native species. We examined the effect of non-native crayfish (Procambarus clarkii) on an existing native predator, dragonfly nymphs (Aeshna sp.), and their mosquito larvae (Anopheles sp.) prey. We used laboratory experiments to compare the predation efficiency of both predators, separately and together, and field data on counts of dragonfly nymphs and mosquito larvae sampled from 13 local streams. We predicted a lower predation efficiency of crayfish compared with native dragonfly nymphs and a reduced predation efficiency of dragonfly nymphs in the presence of crayfish. Dragonfly nymphs were an order of magnitude more efficient predators than crayfish, and dragonfly nymph predation efficiency was reduced in the presence of crayfish. Field count data showed that populations of dragonfly nymphs and mosquito larvae were strongly correlated with crayfish presence in streams, such that sites with crayfish tended to have fewer dragonfly nymphs and more mosquito larvae. Under natural conditions, it is likely that crayfish reduce the abundance of dragonfly nymphs and their predation efficiency and thereby, directly and indirectly, lead to higher mosquito populations and a loss of ecosystem services related to disease vector control. 相似文献
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Roger A. Baldwin Niamh Quinn David H. Davis Richard M. Engeman 《Environmental science and pollution research international》2014,21(9):5795-5802
Roof rats (Rattus rattus) and deer mice (Peromyscus maniculatus) are occasional pests of nut and tree fruit orchards throughout California and in many other parts of the USA and beyond. In general, the most practical and cost-effective control method for rodents in many agricultural environments is the use of rodenticides (toxic baits), but little or no information exists on the efficacy of current rodenticides in controlling roof rats and deer mice in orchards. Therefore, our goals were to develop an index of rodent activity to monitor efficacy of rodenticides and to subsequently test the efficacy of three California Department of Food and Agriculture rodenticide baits (0.005 % chlorophacinone treated oats, 0.005 % diphacinone treated oats, and 0.005 % diphacinone wax block) to determine their utility for controlling roof rats and deer mice in agricultural orchards. We determined that a general index using the number of roof rat photos taken at a minimum of a 5-min interval was strongly correlated to the minimum number known estimate of roof rats; this approach was used to monitor roof rat and deer mouse populations pre- and post-treatment. Of the baits tested, the 0.005 % diphacinone treated oats was most effective for both species; 0.005 % chlorophacinone grain was completely ineffective against roof rats. Our use of elevated bait stations proved effective at providing bait to target species and should substantially limit access to rodenticides by many non-target species. 相似文献
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Sá Roberson Davis Rodríguez-Pérez Adriana Patricia Rodrigues-Silva Fernando de Paula Vinicius de Carvalho Soares Prola Liziê Daniela Tentler de Freitas Adriane Martins de Carvalho Karina Querne de Liz Marcus Vinicius 《Environmental science and pollution research international》2021,28(19):24180-24190
Environmental Science and Pollution Research - The photo-Fenton process was performed with four radiation settings to treat clinical analysis laboratory wastewater (CALWW) from a hospital, with the... 相似文献
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Runion GB Davis MA Pritchard SG Prior SA Mitchell RJ Torbert HA Rogers HH Dute RR 《Journal of environmental quality》2006,35(4):1478-1486
Plant species vary in response to atmospheric CO2 concentration due to differences in physiology, morphology, phenology, and symbiotic relationships. These differences make it very difficult to predict how plant communities will respond to elevated CO2. Such information is critical to furthering our understanding of community and ecosystem responses to global climate change. To determine how a simple plant community might respond to elevated CO2, a model regenerating longleaf pine community composed of five species was exposed to two CO2 regimes (ambient, 365 micromol mol(-1) and elevated, 720 micromol mol(-1)) for 3 yr. Total above- and belowground biomass was 70 and 49% greater, respectively, in CO2-enriched plots. Carbon (C) content followed a response pattern similar to biomass, resulting in a significant increase of 13.8 Mg C ha(-1) under elevated CO2. Responses of individual species, however, varied. Longleaf pine (Pinus palustris Mill.) was primarily responsible for the positive response to CO2 enrichment. Wiregrass (Aristida stricta Michx.), rattlebox (Crotalaria rotundifolia Walt. Ex Gmel.), and butterfly weed (Asclepias tuberosa L.) exhibited negative above- and belowground biomass responses to elevated CO2, while sand post oak (Quercus margaretta Ashe) did not differ significantly between CO2 treatments. As with pine, C content followed patterns similar to biomass. Elevated CO2 resulted in alterations in community structure. Longleaf pine comprised 88% of total biomass in CO2-enriched plots, but only 76% in ambient plots. In contrast, wiregrass, rattlebox, and butterfly weed comprised 19% in ambient CO2 plots, but only 8% under high CO2. Therefore, while longleaf pine may perform well in a high CO2 world, other members of this community may not compete as well, which could alter community function. Effects of elevated CO2 on plant communities are complex, dynamic, and difficult to predict, clearly demonstrating the need for more research in this important area of global change science. 相似文献
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Alison G. Stidworthy Kenneth J. Davis Jeff Leavey 《Journal of the Air & Waste Management Association (1995)》2016,66(11):1141-1150
Burning natural gas in power plants may emit radon (222Rn) into the atmosphere. On the University Park campus of The Pennsylvania State University, atmospheric radon enhancements were measured and modeled in the vicinity of their two power plants. The three-part study first involved measuring ambient outdoor radon concentrations from August 2014 through January 2015 at four sites upwind and downwind of the power plants at distances ranging from 80 m to 310 m. For each plant, one site served as a background site, while three other sites measured radon concentration enhancements downwind. Second, the radon content of natural gas flowing into the power plant was measured, and third, a plume dispersion model was used to predict the radon concentrations downwind of the power plants. These predictions are compared to the measured downwind enhancements in radon to determine whether the observed radon concentration enhancements could be attributed to the power plants’ emissions. Atmospheric radon concentrations were consistently low as compared to the EPA action level of 148 Bq m?3, averaging 34.5 ± 2.7 Bq m?3 around the East Campus Steam Plant (ECSP) and 31.6 ± 2.7 Bq m?3 around the West Campus Steam Plant (WCSP). Significant concentrations of radon, ranging from 516 to 1,240 Bq m?3, were detected in the natural gas. The measured enhancements downwind of the ECSP averaged 6.2 Bq m?3 compared to modeled enhancements of 0.08 Bq m?3. Measured enhancements around the WCSP averaged ?0.2 Bq m?3 compared to the modeled enhancements of 0.05 Bq m?3, which were not significant compared to observational error. The comparison of the measured to modeled downwind radon enhancements shows no correlation over time. The measurements of radon levels in the vicinity of the power plants appear to be unaffected by the emissions from the power plants.Implications: Radon measurements at sites surrounding power plants that utilize natural gas did not indicate that the radon concentrations originated from the plants’ emissions. There were elevated radon concentrations in the natural gas supply flowing into the power plants, but combustion dilution puts the concentration below EPA action levels coming out of the stack, so no hazardous levels were expected downwind. Power plant combustion of natural gas is not likely to pose a radiation health hazard unless very different gas radon concentrations or combustion dilution ratios are encountered. 相似文献