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排序方式: 共有3296条查询结果,搜索用时 15 毫秒
971.
John S. Kinsey Yuanji Dong D. Craig Williams Russell Logan 《Atmospheric environment (Oxford, England : 1994)》2010,44(17):2147-2156
The fine particulate matter (PM) emissions from nine commercial aircraft engine models were determined by plume sampling during the three field campaigns of the Aircraft Particle Emissions Experiment (APEX). Ground-based measurements were made primarily at 30 m behind the engine for PM mass and number concentration, particle size distribution, and total volatile matter using both time-integrated and continuous sampling techniques. The experimental results showed a PM mass emission index (EI) ranging from 10 to 550 mg kg?1 fuel depending on engine type and test parameters as well as a characteristic U-shaped curve of the mass EI with increasing fuel flow for the turbofan engines tested. Also, the Teflon filter sampling indicated that ~40–80% of the total PM mass on a test-average basis was comprised of volatile matter (sulfur and organics) for most engines sampled. The number EIs, on the other hand, varied from ~1015 to 1017 particles kg?1 fuel with the turbofan engines exhibiting a logarithmic decay with increasing fuel flow. Finally, the particle size distributions of the emissions exhibited a single primary mode that were lognormally distributed with a minor accumulation mode also observed at higher powers for all engines tested. The geometric (number) mean particle diameter ranged from 9.4 to 37 nm and the geometric standard deviation ranged from 1.3 to 2.3 depending on engine type, fuel flow, and test conditions. 相似文献
972.
This research investigated the under-explored area of safety in multi-purpose recreation facilities (MPRFs). Facility managers and other managerial staff (key informants) from four MPRFs in Victoria, Australia participated in semi-structured interviews. Safety was considered important from Occupational Health and Safety (OH&S), business viability and legal liability perspectives but not from a health promotion or public health point of view. Most implemented injury prevention measures required gymnasium and pool staff or users to change their behaviours. Awareness of safety standards was higher for some operational areas (e.g. aquatics, child-care) than others (e.g. gymnasium, group fitness activities). Key informants struggled to keep abreast of legislation changes and they relied on commercial, regulatory, and industry information sources rather than evidence of best practice. Reported factors influencing safety in MPRFs were classified into three types: internal (e.g. training, culture); external (e.g. weather, demographic change); and governance (e.g. insurance, industry standards). Comprehensive, relevant and accessible industry safety standards, which focus not only on OH&S but equally on health promotion principles and public health perspectives linked to injury prevention, are required. Training is needed to reflect these broader and equally important perspectives. Health/injury, fitness/recreation and insurance sector links should be improved to ensure a consistent, sustainable approach to safety. 相似文献
973.
Kadhim N. Salman Mary A. Stuart Jack Schmidt T. Borges Craig J. McClain Farrel R. Robinson Miao Li Larry W. Robertson 《Environmental science and pollution research international》2014,21(10):6400-6409
Copper (Cu) metabolism is altered in rats fed diets high in molybdenum (Mo) and low in Cu. This 10-week study was carried out to examine the effects of supplemental Mo (7.5–240 μg/g diet) on male Sprague–Dawley rats fed diets adequate in Cu (5 μg/g diet) and to determine the susceptibility of Mo-treated animals to the environmental pollutant 3,3′,4,4′-tetrabromobiphenyl (TBB). After 7 weeks of dietary treatment, half of the rats in each group received a single IP injection of TBB (150 μM/kg bw), while the other half received the corn oil vehicle. Rats sacrificed at 10 weeks showed no effects of Mo on growth, feed efficiency, or selected organ or tissue weights. Dose-dependent effects on plasma Mo (0–5.1 μg/mL), plasma Cu (0.95–0.20 μg/mL), and bone Cu (3.4–10 μg/g) in control through the high dose were found. Cu sequestration in the bone of Mo-treated rats is a new finding. TBB treatment resulted in dramatic weight loss and loss of absolute organ mass. Relative organ weights were increased, except for the thymus. TBB altered the concentrations of certain amino acids. Compared to control rats, this polybrominated biphenyl congener significantly decreased plasma Cu and ceruloplasmin at higher concentrations of dietary Mo and promoted the process of plasma Cu decrease by Mo, suggesting a combined effect. 相似文献
974.
Daniel Dancer Craig Baker-Austin James A. Lowther Rachel E. Hartnell David N. Lees L. O. Roberts 《Environmental Forensics》2014,15(3):256-264
A novel microbial source tracking (MST) method based on the detection of human and non-human markers was developed and applied to track the origin of fecal pollution in water systems. Mitochondrial DNA sequences were used to develop new quantitative real-time polymerase chain reaction (qPCR) assays for dog, poultry, and gull. The targets were included as part of a toolbox including human, cow, pig, and sheep assays. A primer and probe set for the detection of the human-specific nifH gene of Methanobrevibacter smithii was also designed as an indicator of human fecal contamination. The assays were tested for specificity and applied to fecal-spiked surface waters and environmental samples collected from two river catchments impacted by sources of human and non-human fecal contamination. The MST methods described were applicable to both spiked waters and environmental samples, and using the two approaches the origin of fecal pollution could be successfully determined in mixed source fecally polluted waters. 相似文献
975.
976.
Implications of differing input data sources and approaches upon forest carbon stock estimation 总被引:3,自引:0,他引:3
Michael A. Wulder Joanne C. White Graham Stinson Thomas Hilker Werner A. Kurz Nicholas C. Coops Ben?it St-Onge J. A. Trofymow 《Environmental monitoring and assessment》2010,166(1-4):543-561
Site index is an important forest inventory attribute that relates productivity and growth expectation of forests over time. In forest inventory programs, site index is used in conjunction with other forest inventory attributes (i.e., height, age) for the estimation of stand volume. In turn, stand volumes are used to estimate biomass (and biomass components) and enable conversion to carbon. In this research, we explore the implications and consequences of different estimates of site index on carbon stock characterization for a 2,500-ha Douglas-fir-dominated landscape located on Eastern Vancouver Island, British Columbia, Canada. We compared site index estimates from an existing forest inventory to estimates generated from a combination of forest inventory and light detection and ranging (LIDAR)-derived attributes and then examined the resultant differences in biomass estimates generated from a carbon budget model (Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3)). Significant differences were found between the original and LIDAR-derived site indices for all species types and for the resulting 5-m site classes (p?<?0.001). The LIDAR-derived site class was greater than the original site class for 42% of stands; however, 77% of stands were within ±1 site class of the original class. Differences in biomass estimates between the model scenarios were significant for both total stand biomass and biomass per hectare (p?<?0.001); differences for Douglas-fir-dominated stands (representing 85% of all stands) were not significant (p?=?0.288). Overall, the relationship between the two biomass estimates was strong (R 2?=?0.92, p?<?0.001), suggesting that in certain circumstances, LIDAR may have a role to play in site index estimation and biomass mapping. 相似文献
977.
Using the analytical hierarchy process to assess the environmental vulnerabilities of basins in Taiwan 总被引:3,自引:0,他引:3
Every year, Taiwan endures typhoons and earthquakes; these natural hazards often induce landslides and debris flows. Therefore,
watershed management strategies must consider the environmental vulnerabilities of local basins. Because many factors affect
basin ecosystems, this study applied multiple criteria analysis and the analytical hierarchy process (AHP) to evaluate seven
criteria in three phases (geographic phase, hydrologic phase, and societal phase). This study focused on five major basins
in Taiwan: the Tan-Shui River Basin, the Ta-Chia River Basin, the Cho-Shui River Basin, the Tseng-Wen River Basin, and the
Kao-Ping River Basin. The objectives were a comprehensive examination of the environmental characteristics of these basins
and a comprehensive assessment of their environmental vulnerabilities. The results of a survey and AHP analysis showed that
landslide area is the most important factor for basin environmental vulnerability. Of all these basins, the Cho-Shui River
Basin in central Taiwan has the greatest environmental vulnerability. 相似文献
978.
Assessment of groundwater vulnerability in the Yinchuan Plain,Northwest China using OREADIC 总被引:13,自引:0,他引:13
Groundwater vulnerability assessments provide a measure of the sensitivity of groundwater quality to an imposed contaminant
load and are globally recognized as an essential element of all aquifer management and protection plans. In this paper, the
vulnerability of groundwaters underlying the Yinchuan Plain of Northwest China is determined using OREADIC, a GIS-based assessment
tool that incorporates the key characteristics of the universally popular DRASTIC approach to vulnerability assessment but
has been modified to consider important additional hydrogeological factors that are specific to the region. The results show
that areas of high vulnerability are distributed mainly around Qingtongxia City, Wuzhong City, Lingwu City, and Yongning County
and are associated with high rates of aquifer recharge, shallow depths to the water table, and highly permeable aquifer materials.
The presence of elevated NO3− in the high vulnerability areas endorses the OREADIC approach. The vulnerability maps developed in this study have become
valuable tools for environmental planning in the region and will be used for predictive management of the groundwater resource. 相似文献
979.
Most agronomic situations involve a sequence of herbicide, fungicide, and insecticide application. On the other hand, use
of pesticidal combinations has become a standard practice in the production of many agricultural crops. One of the most important
processes influencing the behavior of a pesticide in the environment is its degradation in soil. It is known that due to several
pesticide applications in one vegetation season, the pesticide may be present in mixtures with other pesticides or xenobiotics
in soil. This study examines the role which a mixture of chemicals plays in pesticide degradation. The influence of other
pesticides on the rate of pendimethalin (PDM) degradation in soil was measured in controlled conditions. Mixtures of PDM with
mancozeb or mancozeb and thiamethoxam significantly influenced the degradation of pendimethalin under controlled conditions.
The second type of mixtures, with metribuzin or thiamethoxam, did not affect the behavior of pendimethalin in soil. Also,
we determined the influence of water content on the rate of pendimethalin degradation alone in two soils and compared it to
the rate in three pesticide mixtures. We compared two equations to evaluate the predictors of the rate of herbicide dissipation
in soil: the first-order kinetic and the non-linear empirical models. We used the non-linear empirical model assuming that
the degradation rate of a herbicide in soil is proportional to the difference of the observed concentration of herbicide in
soil at time and concentration of herbicide in the last day of measurement. 相似文献
980.
Distinguishing and quantifying anthropogenic trace metals and phosphorus accumulated in sediment is important for the protection
of our aquatic ecosystems. Here, anthropogenic proportion and potential sources of trace metals and phosphorus in surface
sediments of Chaohu Lake were evaluated based on the exhaustive geochemical data. The analysis shows that concentrations of
major and trace metals, and phosphorus, displayed significant spatial diversity and almost all elements were over the pre-industrial
background value, which should be related to the variations of sediment composition partially. Therefore, conservative element
normalization was introduced and calculated enrichment factors (EFs) of the elements were referenced highlighting the human
contamination. EFs of the major and trace metals, except Zn, Pb, and Cu, were all nearly 1.0, indicating the detrital origin.
The EFs of Zn, Pb, Cu and phosphorus were 1.0–10.4, 1.0–3.8, 1.0–4.9, and 1.0–7.6, respectively, showing moderate to significant
contamination. Higher EFs of Zn, Pb and Cu occurred in the mouth areas of Nanfei River and Zhegao River, and they decreased
to the lake center in the northwest and northeast lake areas, respectively. We deduced that anthropogenic Zn, Pb, and Cu were
mainly from urban and industrial point sources and the non-point sources of atmospheric deposition contributed little to their
contamination. The EFs of phosphorus showed similar spatial degradation with that of Zn, Pb, and Cu. Moreover, higher EFs
(>1) of phosphorus also occurred in other areas adjacent to the river mouths besides Nanfei River and Zhegao River. This indicated
that the non-point agricultural source may also be responsible for the contamination of phosphorus in Chaohu Lake in addition
to the urban sewage sources. Anthropogenic phosphorus was mainly concentrated in the speciation of NaOH-P, which had higher
potential biological effects than the detrital proportion. Concentrations of Zn, Pb and Cu surpassed the threshold effect
concentrations (TEC) of consensus-based sediment quality guidelines of freshwater ecosystems, especially in the contaminated
northwest area of Chaohu Lake. This highlighted the contributions of anthropogenic contamination to the elevated potential
biological effects of trace metals. Though there had been no obvious human contamination of Cr and Ni in Chaohu Lake, concentrations
were all over the TECs, which may be due to higher background levels in the parent materials of soils and bedrocks in Chaohu
Lake catchment. 相似文献