PCBs and OCPs in sediments from Hongfeng Reservoir in Guizhou Province, China     

Zhongqing WEI Congqiang LIU Xiaobing LIANG Fushun WANG Shaofeng WANG 《中国地球化学学报》2006,25(B08):69-70

In this research, chlorinated hydrocarbons （polychlorinated biphenyls and organochlorine pesticides） were measured by GC-ECD in sediments from the Hongfeng Reservoir area. The concentrations of total PCBs range from 3.2 to 31.6 ng/g, among which PCB28, PCB52 are the major congeners with the concentrations from 0.5 to 4.6 ng/g, and from 0.4 to 28.1 ng/g, respectively. The concentrations of these pollutants decrease from surface to bottom, while the concentrations at 1-4 cm are lower than at 5-8 cm, suggesting the decline of PCBs input. TOC concentrations of sediment are found in a significant positive correlation with those of PCBs, suggesting that PCBs are mainly adsorbed on organic matter and particles. HCHs and DDTs are the predominant organochlorine pesticides with the concentrations ranging from 1.6 to 8.9 ng/g （average 3.2 ng/g） and 0.9 to 25.7 ng/g （average 7.8 ng/g）, respectively. β-HCH and γ-HCH （lindane） are the predominant HCH isomers from sediments, and p, p＇-DDE and p, p＇-DDT are the predominant DDT isomers. DDT/DDE＋DDD and α-HCH/γ-HCH ratios range from 0.6 to 0.9 and 0.1 to 3.0, respectively, which indicates more use of lindane than technical mixtures of HCHs before, and also suggests changes in HCHs and DDTs in the environment. The high values of β-HCH and p, p＇-DDE also show that atmospheric input is one of the important sources of the Hongfeng Reservoir, because β-HCH and p, p＇-DDE are stable and have low Sw and Pv so that they can be easily transferred over a long range in atmosphere.  相似文献   

Early diagenesis of nurtrients （C, N, P and Si） stored in sediments of two reservoirs in southwestern China     

Yuchun WANG Jun ZHU Congqiang LIU 《中国地球化学学报》2006,25(B08):161-162

Damming is a common anthropogenic intervention along the course of rivers, which is defined as ＂artificial-lake effect＂, both in China and across the world. Today as many as 48000 dams and/or reservoirs are in operation in the Changjiang River （Yangtze River） drainage area, and more are being constructed. While damming is well known to affect riverbome nutrient loads, and thus the riverine ecosystems owing to removal of carbon fixation, and removal of particles in reservoir sediments, there is limited information on the detailed early diagenesis of sediments in reservoirs including the regeneration processes of nutrients deposited in sediments and exchange flux across the sediment-water interface, which is important for mass balance of riverbome nutrients. In the present study, two large-size reservoirs, Wujiangdu Reservoir （WJDR） and Dongfeng Reservoir （DFR）, located on the main steam of the Wujiang River and with uniformity hydrography and discrepancy biogeochemical activity （e. g. primary production）, were selected for a comparative study on the detailed processes of nutrient regeneration. Water, pore water and sediment were sampled from these two reservoirs and dissolved organic carbon （DOC）, NH4^＋, NO3^-, PO4^3-, dissolved silica （DSi） in the overlying water and pore water, and total organic matter in sediments were determined. The results of correlation analysis suggested that in these two reservoirs, processes of nutrient regeneration near the sediment-water interface were significantly different. As a result of rapid decomposition of algae-derived ＂labile＂ organic matter in upper sediments, nutrient regeneration processes and upward fluxes in WJDR are dramatically stronger than those of DFR. NH4^＋ upward flux from sediment in WJDR was about 17 times higher than that in DFR. PO4^3- flux in WJDR is about 13 times above that in DFR. DOC flux in WJDR is larger that in DFR by 5 times, and DSi by 1 time.  相似文献   

Reservoir description using dynamic parameterisation selection with a combined stochastic and gradient search     

Lars Kristian Nielsen  Sam Subbey  Mike Christie  Trond Mannseth 《Computational Geosciences》2006,10(3):321-342

There is a correspondence between flow in a reservoir and large scale permeability trends. This correspondence can be derived by constraining reservoir models using observed production data. One of the challenges in deriving the permeability distribution of a field using production data involves determination of the scale of resolution of the permeability. The Adaptive Multiscale Estimation (AME) seeks to overcome the problems related to choosing the resolution of the permeability field by a dynamic parameterisation selection. The standard AME uses a gradient algorithm in solving several optimisation problems with increasing permeability resolution. This paper presents a hybrid algorithm which combines a gradient search and a stochastic algorithm to improve the robustness of the dynamic parameterisation selection. At low dimension, we use the stochastic algorithm to generate several optimised models. We use information from all these produced models to find new optimal refinements, and start out new optimisations with several unequally suggested parameterisations. At higher dimensions we change to a gradient-type optimiser, where the initial solution is chosen from the ensemble of models suggested by the stochastic algorithm. The selection is based on a predefined criterion. We demonstrate the robustness of the hybrid algorithm on sample synthetic cases, which most of them were considered insolvable using the standard AME algorithm.  相似文献   

Optimization of nonconventional wells under uncertainty using statistical proxies     

Vincent Artus  Louis J. Durlofsky  Jérôme Onwunalu  Khalid Aziz 《Computational Geosciences》2006,10(4):389-404

The determination of the optimal type and placement of a nonconventional well in a heterogeneous reservoir represents a challenging optimization problem. This determination is significantly more complicated if uncertainty in the reservoir geology is included in the optimization. In this study, a genetic algorithm is applied to optimize the deployment of nonconventional wells. Geological uncertainty is accounted for by optimizing over multiple reservoir models (realizations) subject to a prescribed risk attitude. To reduce the excessive computational requirements of the base method, a new statistical proxy (which provides fast estimates of the objective function) based on cluster analysis is introduced into the optimization process. This proxy provides an estimate of the cumulative distribution function (CDF) of the scenario performance, which enables the quantification of proxy uncertainty. Knowledge of the proxy-based performance estimate in conjunction with the proxy CDF enables the systematic selection of the most appropriate scenarios for full simulation. Application of the overall method for the optimization of monobore and dual-lateral well placement demonstrates the performance of the hybrid optimization procedure. Specifically, it is shown that by simulating only 10% or 20% of the scenarios (as determined by application of the proxy), optimization results very close to those achieved by simulating all cases are obtained.  相似文献   

福建省山仔水库浮游植物特征与水体富营养状况分析     

苏玉萍  陈娜蓉  林婉珍  梁晓丹 《福建地理》2006,(4)

采用浮游植物指示法评价了福州省山仔水库2005年不同季节水体的富营养状况,结果表明:冬、春季库区水体处于中—富营养水平,夏季发生水华微囊藻(Microcystis flos-aquae)“水华”,水体处于富营养水平,秋季水体处于中营养水平.由于浮游植物的生长状况受到多因素的影响,有必要进一步结合其他评价方法对整个水体的富营养状态做出综合判断.  相似文献   

湿地生态系统碳循环过程及碳动态模型     

仝川  曾从盛 《福建地理》2006,(3)

从地上、地下有机物质生产对湿地碳输入的贡献,湿地土壤碳库以及土地利用变化对湿地土壤碳库和碳排放的影响,甲烷排放和可溶性有机碳输出以及影响因子,湿地生态系统碳循环动态模型4个方面对湿地生态系统碳循环国内外研究进展和研究成果进行综述、分析,提出了我国亚热带区域天然湿地碳循环研究的主要热点和方向:⑴沿海湿地碳库估算及土地利用转化对土壤碳库和温室气体排放的影响;⑵酸沉降对于我国东南沿海低纬度地区湿地甲烷排放的影响;⑶沿海湿地生态系统碳循环动态模型的应用与开发;⑷湿地系统可溶性有机碳的输出机理探讨.  相似文献   

Transparency: aid or obstacle to effective defence of vulnerable environments from reservoir construction? Dam decisions and democracy in North East England     

Christine S McCulloch 《Area》2006,38(1):24-33

Public participation in transparent decisionmaking has been proposed as a panacea for environmental protection. Bargaining theory suggests drawbacks to transparency such as hardening of attitudes and intransigence. Yet achievement of consensus on environmental values for integrated water resource management demands public involvement. Historical study of attempts to prevent reservoir construction in upland valleys designated for protection of nature suggests that 'closed-door' bargaining proved more effective for environmentalists than open, public debate. Records now open for analysis of disputes over Teesdale and Farndale, 1950–1970, allow comparisons to be made between behind-the-scenes deliberations and 'open-door' public discussion. The ambition of progressing from public participation to devolution of environmental decisionmaking and responsibility to the local scale demands more conceptualization of the process of decisionmaking on water resource development.  相似文献   

鄂尔多斯东部下二叠统山西组2段储层评价及勘探前景   总被引：3，自引：6，他引：3  

刘锐娥  李文厚  陈孟晋  张春林  孙粉锦  王雅丽  肖红平  蔺洁 《古地理学报》2006,8(4):531-538

针对鄂尔多斯东部下二叠统山西组2段低渗透油气藏的特点,通过高分辨率层序地层的划分对比,将研究区山2段划分为3个长期旋回。结合425块薄片观察、扫描电镜、阴极发光等储层微观特征分析研究,认为山2段是一套在岸线背景下具有强侵蚀作用的远源砂质辫状河沉积,受物源分异和水动力条件控制,榆林、神木、府谷3条河流的沉积储集特征差异明显,榆林河河道砂体为一套具有石英含量高、杂基和软岩屑含量较低、几乎不含长石的石英砂岩,储层的储集空间主要是以粒间孔为主的复合型孔隙,具有良好的储集性;神木和府谷河河道砂体与之相反,为石英含量低、杂基和软岩屑含量高、普遍含少量长石的岩屑石英砂岩,储层储集性差,仅见少量粒内溶孔。成岩演化分析认为山2段储层进入晚成岩B期,此期压实、压溶作用已非常强烈,榆林地区由于烃类的早期充注才使大量原生孔隙得以保存。通过对山2段储层沉积成岩演化分析,总结了石英砂岩与岩屑石英砂岩沉积储层特征的差异,预测出鄂尔多斯东部下步勘探方向即以榆林气田为代表的榆林河沉积区山2段高渗透石英砂岩发育的河道砂体。  相似文献   

Semi-Analytic Modelling of Subsidence   总被引：2，自引：0，他引：2  

Peter A. Fokker  Bogdan Orlic 《Mathematical Geology》2006,38(5):565-589

This paper presents a forward model for subsidence prediction caused by extraction of hydrocarbons. The model uses combinations of analytic solutions to the visco-elastic equations, which approximate the boundary conditions. There are only a few unknown parameters to be estimated, and, consequently, calculations are very fast. The semi-analytic model is applicable to a uniform and layer-cake stratigraphy, with visco-elastic parameters changing per layer, and an arbitrary depletion pattern. By its capabilities to handle a multi-layered visco-elastic subsurface, the semi-analytic model fills the gap between the analytic single-layered elastic models available to date and the more elaborate numerical, e.g. finite element, models.  相似文献   

基于虚拟SAN的网格GIS数据存储技术研究     

高劲松  张文  关泽群  邓世军 《武汉大学学报(信息科学版)》2005,30(3):214-217

针对空间数据存储的特点，结合网格和虚拟SAN技术的优势，提出了基于虚拟SAN的网格GIS数据存储解决方案．旨在解决网格GIS环境下的数据存储问题。  相似文献