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Bolam SG Rees HL Somerfield P Smith R Clarke KR Warwick RM Atkins M Garnacho E 《Marine pollution bulletin》2006,52(4):415-426
This study provides a holistic perspective on the ecological effects of dredged material disposal, both intertidally and subtidally. A number of numerical techniques (univariate, distributional, multivariate and meta-analysis) were used to assess impacts at 18 different disposal sites. The analyses revealed that ecological effects associated with dredged material disposal were dependent on the numerical techniques used, and that impacts were disposal-site specific. Disposal-site communities were generally faunistically impoverished to varying degrees, and impacts following intertidal placement were comparable to those of subtidal placement. We conclude that any assessment of the consequences of dredged material disposal to the coastal environment must take account of site-specific variation in prevailing hydrographic regimes and in ecological status, along with information on the disposal activity itself (mode, timing, quantity, frequency and type of material). As would be expected, variability in the latter presents a significant challenge in attempts to generalise about environmental and ecological impacts. 相似文献
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本文研究了用摄影测量光束平差法处理经纬仪观测值以解决工业应用中控制网精确测量的。为了证明光束法等效于传统的三维网解法，需要将角度观测值转换成虚拟的像片坐标并进行相应的误差传播，文中为此提出了一种投影的数学模型。此外，还研究了在光束平差法中使用未置平经纬仪的观测值。研究中对两个网进行了试验：一个是工业测量中的控制网，另一个是实验室试验控制网。利用第一个网对光束平差法和传统的三维网法进行比较，结果是： 相似文献
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Four samples of two commercially available iron brands used as substrate for iron permeable reactive barriers (PRBs) were tested for suitability for remediation of perchloroethylene (PCE), trichloroethylene (TCE), cis-dichloroethylene (cDCE) and vinyl chloride (VC). Kinetic studies indicate that rates of reaction are enhanced for cDCE and VC on Connelly iron (2.8 x 10(-4) to 6.9 x 10(-4) L/m2/hr and 2.0 x 10(-4) to 9.0 x 10(-4) L/m2/hr, for cDCE and VC, respectively) vs. Peerless iron (3.1 x 10(-5) to 4.6 x 10(-5) L/m2/hr and 2.4 x 10(-5) to 4.1 x 10(-5) L/m2/hr, for cDCE and VC, respectively). Carbon isotopic analyses of the residual chlorinated ethylene (CE) during degradation indicate significant fractionation occurs during reductive dechlorination, with, for example, up to 70% enrichment in carbon isotopic values observed when VC is more than 99% degraded. Comparison of fractionation factors (epsilon) indicates significant differences in carbon isotopic fractionation for different iron types and for different CEs. For the lower CEs (cDCE and VC) in particular, both slower reaction rates and larger fractionation are observed for degradation on Peerless vs. Connelly iron. This is the first study to establish a correlation between the rate of abiotic degradation on Fe(0) and the extent of isotopic fractionation, and the first to confirm consistent differences in these two parameters as a function of iron type. The possibility that these differences in kinetics and carbon isotopic fractionation for cDCE and VC are related to differences in branching ratios between competing hydrogenolysis and beta-elimination reactions during reductive dechlorination on the iron surfaces is discussed. 相似文献
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