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31.
We analyse recent claims of an additional risk of diffusive intrusion by marine organic contamination (OC) into coastal aquifers, and discuss the activity-driven “salt-pump mechanism” which is claimed to accelerate this diffusion. The reported accelerations of transport of OC out of saltwater are far too large to be due to activity effects on simple diffusion. There probably is a small acceleration of diffusion out of saltwater, but there is no direct experimental evidence for this. Possible experimental artefacts are suggested. Larger effects on diffusion in the literature are shown to be not relevant to this problem. Diffusion of suspended OC, present in the experiments, is too slow to be significant; however, this suspended material is shown to have serious implications for the proposed interpretation of the results. Until these results are better understood, no conclusions about any possible environmental implications can be drawn from them.
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D. R. LloydEmail: Phone: +353-1-6081726Fax: +353-1-6712826 |
32.
Karen P.Y. Lai 《Geoforum》2006,37(4):627-642
This paper examines knowledge production networks in the fund management industry. Focusing on Asian emerging markets (EMs), I explore how fund managers, brokers and research analysts utilise a combination of texts, analytical structures, codified procedures, and social networks to generate interpretations and perspectives on Asian EMs. Utilising a process-based approach, I investigate how ‘EMs’ as an investment category is imagined and practiced by those in the fund management industry through knowledge networks and how such networks are produced and maintained. Discussions are drawn from interviews conducted with 22 EMs specialists in Singapore and London. I argue that Asian EMs have distinct characteristics that are acted upon and reproduced by finance workers in particular ways and that the acquisition and transfer of tacit knowledge takes on increased significance when codified knowledge structures are lacking. Actors in Singapore and London are also embedded in different knowledge networks, which offer different strategic advantages but, when taken together, form a complex and multi-layered knowledge production network of ‘imagineering’ Asian EMs from both within and outside of Asia. 相似文献
33.
Characteristics of distribution and transport of petroleum contaminants in fracture-karst water in Zibo Area, Shandong Province, China 总被引:8,自引:0,他引:8
Fracture-karst water is an important water resource for the water supply in North China. Petroleum contamination is one of
the most problematic types of the groundwater pollution. The characteristics of distribution and transport of the petroleum
contaminants in fracture-karst water are different from those in porous water. The flow velocity of fracture-karst water is
much faster than the velocity of porous water on an average. Therefore, contaminant transport in fracture-karst water is an
absolute advection-dominated problem. The plume of the petroleum contamination may extend to several kilometers from pollution
sources. It was not caused by the oil pool floating on the water table but by the oil components dissolved and scattered in
groundwater. The distribution of the petroleum contaminants over space are concentrated in the strong conductive zone on the
plane. On the vertical section the highest concentration of the oil contaminants appeared in the strata where the contamination
sources were located. The concentrations of the oil contaminants in wells changed greatly over time. Therefore, the curves
of concentration versus time fluctuated greatly. The reasons are as follows. (a) Fracture-karst water has a very great velocity.
(b) Local flow fields which were caused by pumping and stoppage in some wells changed frequently. (c) In fracture-karst aquifer
the transport channels are complicated. (d) Residual oil in vadose zone was leached after rainfall. It is of great practical
value for the control and remediation of petroleum contamination in fracture-karst aquifer to understand those characteristics. 相似文献
34.
Chemostatic behaviour of major ions and contaminants in a semiarid spring and stream system near Los Alamos,NM, USA
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Recent studies have focused on the relationship between solute concentrations and discharge in streams, demonstrating that concentrations can vary little relative to changes in discharge (chemostatic behaviour). Chemostatic behaviour is dependent on catchment characteristics (e.g., lithology, geomorphology, and vegetation) and chemical characteristics of the solute (e.g., availability, reactivity, and mobility). An investigation of 3 springs and a stream near Los Alamos, NM, reveals that springs can behave in a chemostatic fashion as stream systems tend to do. Another unique finding of this study is that the anthropogenic contaminants barium and the high explosive RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine) can also behave chemostatically. The chemostatic behaviour of a contaminant has important implications for the residence time of contaminants in a system as well as having a major control on contaminant flux and mass transport. Redox (reduction–oxidation) and biogeochemically sensitive analytes (e.g., Fe, SO4, and NO3) display a combination of chemostatic and chemodynamic behaviour, showing the influence of temporally variable conditions on stream and spring chemistries. 相似文献
35.
AbstractIn this commentary, we highlight some of the strengths of the bibliometric analysis conducted by Qin et al. that examines the relationships between environmental and natural resource sociologies through citation networks, coauthorship, and keyword usage. We also suggest some ways that the analysis could be expanded or built upon, and ideas for further distinct, but related, inquiry. We also reflect on our own identification, training, and mentoring within the two subfields and draw upon responses from a small purposefully selected sample of other early/mid-career environmental and natural resource sociologists to start a conversation about what the relationship between the two fields might look like in the future. 相似文献
36.
Zhiguang Song Keith W. Jones Nebojsa Marinkovic Xian Ming Xiao Huan Feng Elli Tchouparova 《洁净——土壤、空气、水》2011,39(12):1041-1049
Dredging and remediation of contaminated Harbor sediments requires characterization of organic pollutants. In this paper, we apply a combination of Fourier transform IR attenuated total reflectance (FTIR‐ATR) and synchrotron FTIR techniques to the investigation of sediments and related materials from New York/New Jersey Harbor and other locations. The FTIR techniques give information on the functional groups of the compounds found in the sediments and make possible measurements with a spatial resolution of about 0.015 mm. Comparisons of natural organic materials namely, river and groundwater humic substances, recent marine and lacustrine sediments, and ancient sedimentary kerogen show that contaminated NY/NJ Harbor sediments display a strong and distinct absorption in their IR spectra at 2850–2950 cm?1 identified as a C? H stretching band, indicative of the presence of anthropogenic hydrocarbons. We suggest that the presence of this band could be used for rapid screening for the presence of contaminant organic compounds in sediments encountered in dredging operations and/or as an indicator for the efficacy of sediment decontamination technologies used for treatment of dredged material. 相似文献
37.
38.
In this study, a generalized contaminant retardation factor applicable to a multiphase system where various types of colloids exist simultaneously with contaminants is derived and incorporated into an equilibrium model which is successfully applied to experimental data for which phenanthrene was used as hydrophobic organic contaminants and dissolved organic matter (DOM) or bacteria as mobile carriers. Based on the parameter values for the experimental data regarding the association of phenanthrene with solid matrix, DOM and various bacterial isolates, numerical experiments are performed to examine the transport behaviour of hydrophobic organic contaminants in various types of the multiphase system. Numerical experiments demonstrate that the extent of contaminant transport enhancement depends on the adsorption affinity of the colloid, its concentration and its mobility, and that the importance of a third phase to contaminant transport needs to be evaluated carefully with respect to the relevance of experimental conditions applied to realistic environmental conditions. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
39.
Contaminants were assessed in Sydney Harbour during baseline and three years of remediation of a former coking and steel facility. Concentrations of PAHs; PCBs; and lead measured in surface sediments indicate overall spatial distribution patterns of historical contaminants remains unchanged, although at much lower concentrations than previously reported due to natural sediment recovery. Recovery rates were in broad agreement with predicted concentrations; or in some cases lower, despite remediation at the Sydney Tar Ponds (STP) site. Contaminants showed little temporal variability, except for detection of significant increases in PAH concentrations during onset of remediation compared to baseline which represented a short term interruption in the overall long term natural recovery of sediments in Sydney Harbour. Recovery (via “capping”) was enhanced following recent harbour dredging activities where less contaminated outer harbour sediments were discharged into a confined disposal facility (CDF) required for a new container in the inner harbour. 相似文献
40.
渤海滩涂湿地沉积物胶体对石油污染物的吸附特征 总被引:1,自引:0,他引:1
为了研究滩涂湿地沉积物胶体对石油污染物的吸附作用,根据渤海天津段滩涂湿地沉积物的结构和组成,选择代表性沉积物提取胶体,对胶体的粒径、ζ电位、电泳淌度进行了表征,系统测定胶体对可溶性油吸附的动力学曲线和吸附等温线。结果表明,滩涂湿地沉积物胶体平均粒径为345.04nm;ζ电位、淌度中值分别为-0.47mV、-0.03μs-1V-1cm;交换吸附动力学模式适用于滩涂沉积物胶体对可溶性油的吸附作用,其吸附平衡时间约为20~24h,胶体对可溶性油吸附速率常数为9.434L/(g·h);胶体对可溶性油的等温吸附线为直线型,当水相中石油烃浓度低于某一值时,胶体不但不吸附溶液中的石油烃,反而使胶体中的残留石油烃释放出来。 相似文献