利用水平定向钻进改善香港长洲岛水供应

目前,香港长洲岛的自来水主要由位于大屿山岛的银矿湾自来水厂供应。银矿湾自来水厂利用两条长度均为1．4千米左右的海底自来水总管道,穿越北长洲海峡向长洲岛供应自来水。这两条管线分别铺设于1963年和1986年,均采用传统的海底开挖方法。由于管线老化,不断增加的不可靠性以及缺乏满足未来需求的能力,需要对提高长洲岛自来水供应的各种方法实施调查。由于北长洲海峡是香港和澳门之间快速轮渡的主要航线,以及重要的环境问题,人们认识到传统的水下开挖方法将会给新管道的安装带来很多问题,因此,对多个方法进行了调查评估,主要的依据包括资本和运营成本、技术可行性、施工能力、实施规划、操作和维护问题、环境影响、渔业影响、文化遗产影响及海洋交通影响。本文阐述了各种考虑到的非开挖方法,简要介绍了使用水平定向钻进铺设新管线的原因、施工方法及创新性．     

Radiocesium reaction with illite and organic matter in marine sediment

The mineralogical effect on the (137)Cs reaction with marine sediment has not been systematically studied yet, even though illite has been known to adsorb Cs preferentially on its frayed edge sites in a low Cs concentration. Ninety-three marine sediment samples were collected near Yangnam, Korea for quantitative X-ray-diffraction (XRD), gamma-ray, and total organic carbon (TOC) analysis. Illite content was in the range of 0-23 wt.% and those of (137)Cs and TOC were minimum detectable activity (MDA) approximately 7.19 Bq/kg-dry and approximately 3.32%, respectively. The illite content in the marine sediment showed a good relationship with the (137)Cs content (R(2)=0.69), but with an increase in the illite content, the relationship became less linear. This trend can be clearly shown in two groups of samples with different size fractions (< and >5Mdvarphi). For the samples of larger particle sizes (low contents of illite), the relationship is linear, but for the samples of the smaller particle sizes (high illite content) it is less linear with a decreased slope, indicating that increase in illite content does not significantly contribute to the fixation of (137)Cs in marine sediment. Rather, the TOC has a more linear relationship with (137)Cs content with no slope change in all particle size ranges. This may indicate that humic materials in marine sediment block the access of (137)Cs to the frayed edge site and reduces the adsorption of (137)Cs on illite and that the organic materials in marine sediment play more important roles in adsorbing Cs than illite.     

A visual basic spreadsheet macro for recession curve analysis

A Visual Basic program for an Excel spreadsheet was written to construct a master recession curve (MRC), using the adapted matching strip method, for recession analysis of ground water level time series. The program uses five different linear/nonlinear regression models to adjust individual recession segments to their proper positions in the MRC. The program can also be used to analyze the recession segments of other time series, such as daily stream discharge or stage. Some examples of field data from Croatia are used to illustrate the usefulness of its application.     

Reducing long-term remedial costs by transport modeling optimization

The Department of Defense (DoD) Environmental Security Technology Certification Program and the Environmental Protection Agency sponsored a project to evaluate the benefits and utility of contaminant transport simulation-optimization algorithms against traditional (trial and error) modeling approaches. Three pump-and-treat facilities operated by the DoD were selected for inclusion in the project. Three optimization formulations were developed for each facility and solved independently by three modeling teams (two using simulation-optimization algorithms and one applying trial-and-error methods). The results clearly indicate that simulation-optimization methods are able to search a wider range of well locations and flow rates and identify better solutions than current trial-and-error approaches. The solutions found were 5% to 50% better than those obtained using trial-and-error (measured using optimal objective function values), with an average improvement of approximately 20%. This translated into potential savings ranging from 600,000 dollars to 10,000,000 dollars for the three sites. In nearly all cases, the cost savings easily outweighed the costs of the optimization. To reduce computational requirements, in some cases the simulation-optimization groups applied multiple mathematical algorithms, solved a series of modified subproblems, and/or fit "meta-models" such as neural networks or regression models to replace time-consuming simulation models in the optimization algorithm. The optimal solutions did not account for the uncertainties inherent in the modeling process. This project illustrates that transport simulation-optimization techniques are practical for real problems. However, applying the techniques in an efficient manner requires expertise and should involve iterative modification to the formulations based on interim results.     

The significance of dilution in evaluating possible impacts of wastewater discharges from large cruise ships

In response to public concerns about discharges from large cruise ships, Alaska's Department of Environmental Conservation (ADEC) sampled numerous effluents in the summer of 2000. The data showed that basic marine sanitation device (MSD) technology for black water (sewage) was not performing as expected. Untreated gray water had high levels of conventional pollutants and surprisingly high levels of bacteria. Both black water and gray water discharges sometimes exceeded state water quality standards for toxicants. The state convened a Science Advisory Panel (the Panel) to evaluate impacts associated with cruise ship wastewater discharges. The effluent data received wide media coverage and increased public concerns. Consequently, legislative decisions were made at the State and Federal level, and regulations were imposed before the Panel completed its evaluation. The Panel demonstrated that following the rapid dilution from moving cruise ships, the effluent data from the Summer of 2000 would not have exceeded water quality standards, and environmental effects were not expected.     

Physical and biological development of a newly breached managed realignment site, Humber estuary, UK

As part of the Humber flood defence upgrade works (Urgent works) undertaken by the Environment Agency, the Paull Holme Strays site was identified as one of twelve potential managed realignment sites within the Humber catchment. The site was breached in September 2003, creating 80 hectares of new intertidal habitat. Initial accretion monitoring commenced in December 2003 with annual surveys of invertebrate colonisation commencing in October 2004. The present study gives details of the physical development of the newly created mudflat within the site, together with invertebrate colonisation and benthic community change over time. Comparisons between the newly created habitat and the existing mudflat outside the old sea wall are made. The macrofaunal communities found within the area as a whole are considered to be characteristic of the area with low species diversity, high abundance and small body size. The community within the managed realignment site is still in an early successional stage with low abundance and diversity in comparison with other sites within this part of the Humber. However the community biomass increased considerably between 2004 and 2005. Colonisation within the managed realignment site is still primarily concentrated in the areas around the two breach sites and is thought to be restricted in other areas due to infrequent tidal inundation.     

The accumulation of radiocesium in coarse marine sediment: effects of mineralogy and organic matter

The controlling factors affecting the accumulation of (137)Cs in marine sediment have not been investigated in detail, especially in coarse grained sediment. Eighty eight coarse marine sediment samples near Wuljin, Korea, were characterized by quantitative X-ray-diffraction (XRD), gamma-ray, and total organic carbon (TOC) analysis. Those factors were then compared. The grain size was in the range of -0.48 to 3.6Mdphi corresponding to sand grains. TOC content was in the range of 0.06-1.75%, and the concentration of (137)Cs was 相似文献   

Survival of Vibrio alginolyticus in seawater and retention of virulence of its starved cells

The aim of this study was to evaluate the survival responses of four strains of Vibrio alginolyticus in seawater under starvation conditions. We used microcosms containing sterilised seawater and incubated at ambient temperature (22-25 degrees C). V. alginolyticus maintained its culturability for at least nine months. Long-term-starved cells showed an absence or a decrease in their enzymatic activities. Resuscitation assays of viable but non-culturable (VBNC) cells were conducted and the recovery of these cells was achieved after the addition of nutrients. Amplified 16S ribosomal DNA (rDNA) restriction analysis (ARDRA) was used to confirm that the same strain of V. alginolyticus persisted in all microcosms during a long period of time. Starved cells maintained their infectivity for gilt head sea bream (Sparus aurata) and sea bass (Dicentrachus labrax) as determined by intraperitoneal challenges.     

Why did the copepod Calanus sinicus increase during the 1990s in the Yellow Sea?

Recent field and retrospective data were combined to investigate variations from 1984 to 1998 in the spring abundance of dominant copepods in the Yellow Sea. A calanoid copepod, Calanus sinicus, was chosen to assess the long-term changes in abundance associated with temperature, salinity, chlorophyll-a and predator abundance. Average anomalies of sea surface temperature (SST), salinity, and the abundance of C. sinicus were positive in the 1990s and negative in the 1980s. The average abundances of C. sinicus in the study area in the 1990s were also significantly higher than those in the 1980s (p<0.01). Catches of the anchovy Engraulis japonicus, a predator of C. sinicus, showed a decreasing trend during the study period. The higher abundances of C. sinicus in the 1990s may have been affected by an increase in water temperature and a decrease in predators, without distinctive changes in chlorophyll-a concentrations during the study period.