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排序方式: 共有251条查询结果,搜索用时 15 毫秒
91.
Concentrations, distribution, and bioaccumulation of synthetic musks in the Haihe River of China 总被引:4,自引:0,他引:4
Seven typical synthetic musks (SMs) in the samples from the surface water, sediment and fish of the Haihe River were measured. The SM concentrations in the sediment and surface water of the Haihe River were significantly lower than those in the Dagu Drainage River and Chentaizi Drainage River (p < 0.05). Along the flow direction, the SM concentrations in surface water and sediment tended to increase from the upstream to the downstream of Dagu Drainage River. The Bioaccumulation factors (BAFs) of galaxolide (HHCB) and tonalide (AHTN) were calculated at high levels in the muscles of crucian carp, common carp, and silver carp. Most of the biota-sediment accumulation factors (BSAFs) for HHCB and AHTN were higher than 1.7, suggesting magnification possibly exist in the musk bioaccumulations of the three fishes in the Haihe River. No significant differences in HHCB/AHTN ratios were observed among the water, fish, and sediment samples (p > 0.05). However, the HHCB/AHTN values in the Haihe River were much lower than those in the Dagu Drainage River and Chentaizi Drainage River (p < 0.05). Compared with several typical persistent organic pollutants (POPs), the musk concentrations were higher or comparable in the Haihe River. 相似文献
92.
Distribution and sources of polycyclic aromatic hydrocarbons in surface sediments of rivers and an estuary in Shanghai, China 总被引:7,自引:0,他引:7
Liu Y Chen L Jianfu Z Qinghui H Zhiliang Z Hongwen G 《Environmental pollution (Barking, Essex : 1987)》2008,154(2):298-305
Concentrations, spatial distribution and sources of 17 polycyclic aromatic hydrocarbons (PAHs) and methylnaphthalene were investigated in surface sediments of rivers and an estuary in Shanghai, China. Total PAH concentrations, excluding perylene, ranged from 107 to 1707 ng/g-dw. Sedimentary PAH concentrations of the Huangpu River were higher than those of the Yangtze Estuary. The concentration of the Suzhou River was close to the average concentration of the Huangpu River. PAHs source analysis suggested that, in the Yangtze Estuary, PAHs at locations far away from cities were mainly from petrogenic sources. At other locations, both petrogenic and pyrogenic inputs were significant. In the Huangpu and Suzhou Rivers, pyrogenic input outweighed other sources. The pyrogenic PAHs in the upper reaches of the Huangpu River were mainly from the incomplete combustion of grass, wood and coal, and those in the middle and lower reaches were from vehicle and vessel exhaust. 相似文献
93.
Guiling?L.?ZhangEmail author Jing?Zhang Jie?Xu Jingling?L.?Ren Sumei?M.?Liu 《Water, Air, & Soil Pollution: Focus》2007,7(6):645-654
CH4 concentrations in both the surface and bottom waters of Jiaozhou Bay were determined during four surveys in 2003, which showed
variability with both seasons and tidal cycles. Atmospheric fluxes of CH4 in Jiaozhou Bay showed obvious seasonal and spatial variations, with the highest values occurring in summer and the lowest
in winter. The annual emission of CH4 from Jiaozhou Bay was estimated to be . CH4 in the water column of Jiaozhou Bay was found to come from several land-sources including riverine water input, sewage water
input and groundwater input. The spatial and temporal variation in distributions and atmospheric fluxes of CH4 in Jiaozhou Bay was influenced mainly by the input of polluted river waters and the sewage effluents along the eastern coast,
which highlights the effects of human impacts on CH4 emission rates. 相似文献
94.
压入式局部通风工作面风流分布数值模拟研究 总被引:7,自引:1,他引:6
笔者应用三维k -ε紊流模型描述压入式局部通风工作面风流的流动过程 ,并采用控制容积法导出了描述流体流动方程的离散化方程式 ;用计算流体力学的方法求得了三维k -ε紊流模型的数值解。采用SIMPLE(压力耦合方程式的半阴解法 )算法解算流场 ;TDMA(三对角线算法 )和Gauss Seidel法结合通过线顺法求解离散方程。利用弱松弛法防止非线性方程组迭代求解过程中的发散现象 ,获得了掘进工作面空间的速度分布 ;并将模拟解算结果与在具有实际尺寸的拱形巷道模型中测得的实验结果进行了对比。数值计算结果与模型实验测定结果非常一致 ,验证了笔者的数学模型和数值模拟方法的正确性。 相似文献
95.
96.
Lennart Hansson 《Behavioral ecology and sociobiology》1996,39(5):331-334
North Scandinavian bank voles (Clethrionomys glareolus) differ from south Scandinavian conspecifics both in population dynamics and in activity, social behaviour, density-related
sensitivity in sexual maturation and in reproduction. Some ecologists think that cyclically fluctuating rodents are particularly
aggressive, at least in certain cycle phases. This hypothesis was tested in dyadic encounters between animals from southern
and northern Sweden, respectively. Univariate analyses showed significant differences between regions in four separate behavioural
traits, but not in behaviour related to aggression. Laboratory breeding for several generations did not affect the level of
aggressivity. Multivariate analyses revealed two main components of activity and sociability, both with regional variation.
Activity components (also including “freezing” behaviour) were chiefly related to age while sociability showed mainly regional
variation. Differences observed may be due to the geographic location or earlier cyclicity, as the cyclic pattern was weak
at the time when the test animals were sampled. An adaptation to high-density situations appears likely as the sympatric field
vole (Microtus agrestis) shows similar regional differences although it lives in a different habitat. Cyclic animals appear to disperse at increasing
densities while non-cyclic animals show clumped distributions.
Received: 19 February 1996/Accepted after revision: 17 August 1996 相似文献
97.
采集了商丘市包河6个位点的表层沉积物,用色谱-质谱对正构烷烃进行了分析,利用正构烷烃碳数分布特征和CPI指标等,对该市区的正构烷烃来源进行初步探讨。结果表明,正构烷烃碳数分布范围多数在nC13-nC31之间,分布类型只有一种,即高分子碳范围,碳优势指数为nC29,1相似文献
98.
城市浅水湖泊沉积物磷形态分布及其与间隙水磷的关系 总被引:1,自引:0,他引:1
研究了典型城市浅水湖泊莫愁湖沉积物中磷形态及间隙水中TDP、PO43--P含量的垂向分布情况,沉积物中IP是TP的主要组成部分,与湖泊富营养化密切相关的Fe-P占IP的30%左右,Or-P占TP的30%左右。柱状沉积物中磷形态的垂向分布规律比较复杂,但基本上随深度先增后减的趋势。沉积物中TPI、P、Or-P、Ca-P、Fe-P、DP之间都具有极显著的正相关关系,但与Al-P、Oc-P的相关关系不明显,间隙水中TDP、PO43-P浓度与沉积物中Or-P含量具有显著的正相关关系,但相关程度并不高,与其他形态则没有明显的相关关系。 相似文献
99.
100.
The transportation of natural gas often relies on pipelines which require constant monitoring and regular maintenance to prevent spills or leaks. Pipeline incidents could pose a huge adverse impact on people, the environment, and society. Numerous efforts have been invested to identify contributing factors to pipeline incidents so that countermeasures could be developed to proactively prevent some incidents and reduce incident severities or impacts. However, the countermeasures may need to vary for different incidents due to the potential heterogeneity between incidents, and such heterogeneity is likely related to the geology, weather, and built environment which vary across space and time domain. The objective of this study is to revisit the correlates of pipeline incidents, focusing on the spatial and temporal patterns of the correlations between natural gas pipeline incident severity and contributing factors. This study leveraged an integrated spatio-temporal modeling approach, namely the Geographically and Temporally Weighted Ordered Logistic Regression (GTWOLR) to model the natural gas pipeline incident report data (2010–2019) from the U.S. Pipeline and Hazardous Material Safety Administration. Text mining was performed to extract additional information from the narratives in reports. Results show several factors have significant spatiotemporally varying correlations with the pipeline incident severity, and these factors include excavation damage, gas explosion, iron pipes, longer incident response time, and longer pipe lifetime. Findings from this study are valuable for pipeline operators, end-users, responders to jointly develop localized strategies to maintain the natural gas distribution system. More implications are discussed in the paper. 相似文献