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991.
A major focus of palynological research has been to assess the various pathways by which pollen is delivered to sedimentary
archives. In open lake systems, the contribution of streamborne pollen to lake sediments is thought to be highly significant.
Despite this, little research has attempted to identify changes in the pollen record that might be attributed to changing
sediment pathways rather than to changes in vegetation. This research aims to partially redress this gap by examining a dated
pollen sequence from Kyre Pool, Worcestershire, England. The results presented in this paper suggest that some changes in
sediment source, as determined by a fingerprinting approach, can influence the pollen record reconstructed from a lake sediment
profile. 相似文献
992.
我国新疆地区经常发生冰川阻塞湖引起的突发性洪水灾害.通过对叶尔羌河、昆马力克河和四棵树河三条典型河流的研究,发现可预报洪水序列与阻塞湖库容量有正相关关系.结合分析阿尔泰山、祁连山和西藏地区的地理环境特点,认为塔里木盆地周边地区是冰湖洪水的突发区. 相似文献
993.
994.
In poorly buffered areas acidification may occur for two reasons: through atmospheric deposition of acidifying substances and – in mining districts – through pyrite weathering. These different sources of acidity lead to distinct clearly geochemistry in lakes and rivers. In general, the geochemistry is the major determinant for the planktonic composition of the acidified water bodies, whereas the nutrient status mainly determines the level of biomass. A number of acidic mining lakes in Eastern Germany have to be neutralized to meet the water quality goals of the European Union Directives and to overcome the ecological degradation. This neutralization process is limnologically a short-term maturation of lakes, which permits biological succession to overcome two different geochemical buffer systems. First, the iron buffer system characterizes an initial state, when colonization starts: there is low organismic diversity and productivity, clear net heterotrophy in most cases. Organic carbon that serves as fuel for the food web derives mainly from allochthonous sources. In the second, less acidic state aluminum is the buffer. This state is found exceptionally among the hard water mining lakes, often as a result of deposition of acidifying substances onto soft water systems. Colonization in aluminum-buffered lakes is more complex and controlled by the sensitivity of the organisms towards both, protons and inorganic reactive aluminum species. In soft-water systems, calcium may act as antidote against acid and aluminum; however, this function is lost in hard water post mining lakes of similar proton concentrations. Nutrient limitations may occur, but these do not usually control qualitative and quantitative plankton composition. In these lakes, total pelagic biomass is controlled by the bioavailability of nutrients, particularly phosphorus. 相似文献
995.
Issac Yomtovian 《Journal of the American Water Resources Association》1978,14(5):1176-1186
ABSTRACT: The frequent high water levels in Chisago Chain of Lakes, located in east-central Minnesota, have caused extensive flood damages. Recent floods raised the concern of the local property owners and they pressured the Chisago County Board of Managers to initiate a study of alternative lake control levels. A study was carried out to identify potential flood control alternatives, screen out the most promising feasible alternatives, and recommend the most cost-effective flood control measure. Several flood control alternatives were considered - eight of them were analyzed and evaluated in detail. A statistical method was used to estimate the expected annual flood damages under existing and future conditions. The effect of all proposed control measures on the annual flood damage reductions (benefits) were determined. Detailed benefit/cost analyses were carried out to evaluate the economic feasibility of alternatives. The effect of potential flood control measures on the environment was also studied. The economic analysis of the most cost-effective alternative did not strongly support artificial lake level control, therefore the decision-making authorities were even more firm in their position to maintain the present condition and chose the Null Alternative as the most suitable alternative. 相似文献
996.
程海湖流域生态环境现状及保护 总被引:1,自引:0,他引:1
由于自然原因和人为影响,程海湖周围生态系统严重退化,湖泊水质污染加重,已进入营养向富营养化趋进的过程。必须从宏观调控、入湖污染物总量控制、水资源管理、水污染控制和陆地生态建设等方面采取相应对策,以控制恶化,改善生态环境。 相似文献
997.
998.
本文依据湖泊、水库的箱式模型理论,建立了简阳三岔湖水库网箱养鱼总磷模型和容解氧模型。并利用这一模型对不同网养面积下三岔湖水库总磷浓度和溶解氧进行了模拟实验。结果指出:按照三岔湖1991年养鱼特征和水文特征,网养面积最好不超过4.4×104m2,绝对不能超过6×104m2。 相似文献
999.
皖北朱仙庄矿塌陷湖水域重金属含量特征及其源解析 总被引:1,自引:0,他引:1
以皖北朱仙庄矿塌陷湖水域为研究对象,通过现场调查取样,室内测试分析等手段,对Pb、V、Cr、Cu、Co、Ni 6种重金属元素的含量特征进行研究,结果表明,塌陷湖6种重金属元素含量均值的高低顺序为VCuNiPbCrCo,变异系数依次为PbCoCrCuNiV,其中Pb、Co变异系数分别为99.7%和93.6%,空间分异大。箱体图显示,6种重金属元素的含量均不同程度高于环境背景值,塌陷湖Ⅱ中6种重金属元素含量较高,受人类活动影响较大,塌陷湖Ⅳ受人类活动影响最小。聚类分析和主成分分析表明,朱仙庄矿塌陷湖水域重金属元素来源存在差异,其中Pb、Cu来源于煤矸石淋溶作用;V、Co来源于燃煤作用;Cr来源于自然界,Ni元素具有来源的复合性。 相似文献
1000.
为实现流域范围内的生态环境管理和生态风险控制,在生态风险评估框架基础上,基于相对风险模型构建了系统水平的湖泊流域生态风险评估模型. 模型分析了社会经济系统与生态系统的耦合方式,将生态系统整体作为风险受体、生态系统服务作为评估终点,通过风险组分及其关系的分析量化实现了区域相对生态风险水平的表征,并以太湖流域上游区域为例进行了试算. 结果表明:研究区内无锡-江阴区域(沿江水系)生态风险最高,溧阳-宜兴、常州-金坛、湖州-德清和长兴-安吉区域风险值分别为无锡-江阴区域的73.2%、78.8%、74.4%和59.9%;长兴-安吉区域(西苕溪水系)生态风险最低. 不同区域风险主要来源不同,湖州-德清区域主要受水利设施影响,长兴-安吉区域各风险源贡献率较为均衡,其他区域主要风险源为工业、种植业和水产养殖业,其风险贡献率分别为13%~18%、12%~19%和8%~15%;研究区域内,水产品、水质净化等生态系统服务的产出受到较大影响. 相似文献