黑河流域水环境演变及其驱动机制研究进展   总被引：10，自引：0，他引：10  

肖生春  肖洪浪 《地球科学进展》2008,23(7):748-755

基于近几十年来诸多学者对西北干旱区典型内陆河流域——黑河流域水环境演变诸方面研究成果,综述了上游山区成水环境、中游绿洲用水环境和下游荒漠天然绿洲水成环境在不同时间尺度上的演变过程及其驱动机制。通过对各种古环境代用指标的对比研究表明：在大尺度上,流域上下游表现出阶段性的一致性水环境演变趋势;在小尺度上,则表现水环境演变的时空异质性。驱动机制方面,在空间上,流域上、中、下游水环境演变的气候变化和人类活动影响驱动作用各有侧重;在时间上,表现为不同尺度上气候变化与流域人类活动耦合作用的驱动机制。  相似文献   

海底泉对在海底有限延伸的越流含水层系统中地下水潮汐效应的增强作用     

杨颖  李海龙  夏玉强  孙萍萍 《地下水》2008,30(2):9-14

海底泉在滨海地下水排泄过程中起着重要的作用。本文给出了含有一个海底泉的在海底延伸的越流承压含水层系统中地下水水头在海潮作用下波动的近似解析解。该含水层顶底板隔水且向海底延伸有限距离。假设含水层的海底露头被一层隔水层覆盖,海底泉由一个渗透性很好的完全穿透海底含水层硕板的圆柱体渗漏天窗（海底泉孔）来表示。近似解析解中包含了6个参数：承压含水层的海潮传播参数,海底泉孔中心到海岸线的距离,表示泉的圆柱体的等效半径,海底泉孔中心到含水层海底露头处的距离,承压含水层的海潮载荷效率和弱透水层的越流。分析表明,如果海底泉孔中心到海岸线的距离远大于泉孔的等效半径,且海底泉孔中心到含水层海底露头处的距离远大于泉孔的等效半径时,解析解的近似误差可以忽略。然后本文讨论了解析解的两个基本性质,分析了海底泉对海底地下水水头波动的影响。  相似文献   

四川省九龙县娃娃沟泥石流运动特征与堵河成灾机制分析     

施蕾蕾  陈宁生  杨成林 《中国地质灾害与防治学报》2008,19(2):16-22

2006年7月16日娃娃沟流域暴发的大规模泥石流,给下游3个电站造成巨大经济损失,是大渡河流域一次典型的灾害性泥石流。分析得出,娃娃沟泥石流重度高、搬运能力强,泥石流固体物质砂、石混杂,粗大砾石含量高;暴发频率低、规模大,流速及峰值流量分别高达10．78m／s及798．5m^3／s;在汇口处,泥石流堆积物堵塞河道是引起下游电站受灾的重要原因,高重度、粗颗粒、大流量的组合是此次泥石流堵江的重要原因。堵河判别计算结果显示在发生百年一遇泥石流时,该断面均有发生堵河的可能。娃娃沟泥石流表明：①在大渡河支流的泥石流沟周边的中小电站极有可能在泥石流暴发时受到破坏。因此,电站建设过程中应加强对周边泥石流沟的防灾减灾工作;②虽然娃娃沟流域植被良好,但仍然发生了大规模泥石流。表明植被不能完全避免泥石流的发生,对于此类泥石流沟不能疏忽大意。  相似文献   

太湖入湖河道沉积物中生物利用磷和营养水平分析   总被引：7，自引：0，他引：7  

袁旭音  李兵  许薇薇  陈颖 《地学前缘》2008,15(5):212

为了解太湖入湖河道的营养状况,研究了太湖西部河流沉积物生物利用磷的组成与分布。研究结果显示,北部沉积物中营养元素较高,南部较低;沉积物中生物利用磷的含量次序为藻类可利用磷(AAP)>NaHCO3提取磷(OLP)>水溶性磷(WSP)>易解吸磷(RDP),其中AAP是重要的生物利用磷,AAP的比例越高,富营养化程度越高。AAP与营养元素的相关性在不同区域河道有所不同,北部河道与总氮(TN)、总磷(TP)相关性较好,中部和南部河道与沉积物有机质总量(TOM)相关性较好。沉积物的生物利用磷受不同污染源影响较大。对比河道沉积物与湖泊沉积物的特征,发现湖泊沉积物中生物利用磷(BAP)/总磷(TP)、藻类可利用磷(AAP)/总磷(TP)都高于河道沉积物,表明湖泊沉积物中的磷更容易被植物吸收。  相似文献   

河流活性物质入海通量:概念与方法   总被引：1，自引：0，他引：1  

周国华  孙彬彬  刘占元  魏华玲  曾道明 《地质通报》2008,27(2):182-187

河流水体中呈溶解态和悬浮物结合态的元素活动性强,具有生态环境意义,查明其入海通量是当前生态地球化学评价的重要任务。通过总结前人的相关研究成果,确定了影响河流水体悬浮物的浓度及其矿物、化学组成的主要因素。从沿海经济带区域生态地球化学评价的实际需要出发,拟定了开展中国主要入海河流水溶态和悬浮物结合态元素入海通量调查的基本框架。  相似文献   

近50 a渭河流域洪水成因分析及防治对策   总被引：6，自引：1，他引：6  

张琼华  赵景波 《中国沙漠》2006,26(1):117-121

 通过对近50 a渭河流域洪水的年际变化、月际变化和潼关高程变化的综合分析得出，造成该流域洪水灾害的原因有降水量年内分配不均和年际变化大，滩面淤积加重，支流河口淤塞以及河势、流态的恶化等。针对这些原因，根据渭河流域洪水灾害的特点，提出了相应的防治措施，即降低下游高程，减少河道的淤积，增大河道泄洪能力；利用水库进行调水调沙，引进客水冲刷渭河下游；防洪工程要除险加固，提高防洪标准与抗洪能力；恢复林草植被，遏止水土流失，从源头上控制泥沙入河等。  相似文献   

三工河流域新老绿洲发育度的比较   总被引：1，自引：0，他引：1  

何新梅  李小玉  肖笃宁  李彦 《干旱区地理》2006,29(3):342-347

绿洲是干旱区最重要的景观单元之一。人工绿洲是在干旱条件下经长期人类活动改造而形成的特殊景观。随着人类对绿洲水土资源开发利用程度的不断加强,绿洲呈现出不同的发展阶段。从天然绿洲到人工绿洲,是人类适应和改造干旱区自然环境的历程。在这一人地相互作用的过程中,绿洲显示出明显的发育演化特征。从多学科综合的角度,提出绿洲发育度的概念,并从灌溉体系的建设状况、水资源的利用水平、植被与生态建设、农业发展程度、社会经济水平和绿洲景观结构等7个方面提出了绿洲发育度的评价指标体系,以天山北坡2个人工绿洲为例,从空间上定量比较2个绿洲的发育程度,其中阜康市绿洲发育度高于222团绿洲(阜北农场)。  相似文献   

The ＂CO2-rich gas vents＂ of Mt. Amiata volcano （Tuscany, Central Italy）： Geochemistry,genetic mechanism and hazard evaluation     

Franco Tassi Orlando Vaselli Elena Lognoli Fabrizio Cuccoli Barbara Nisi Elena Ramaldi Sandro Moretti Luca Lombardi Bruno Capaccioni 《中国地球化学学报》2006,25(B08):70-71

Mt. Amiata （Southern Tuscany, Central Italy） is an extinct Quaternary volcano located in an area still marked by high heat-flow that is caused by deep seated （6-10 km） hot masses related to Pliocene magmatic activity. The anomalous geothermal gradient gives rise, within the Mesozoic limestone formation （Tuscan series）, to geothermal systems that fed the Ca-SO4 thermal springs characterizing this area. Besides of thermal fluids, several cold, dry CO2-rich gas emissions seep out on the NE flank of the volcano. These gas vents mostly consist of large sub-circular craters at variable depth and diameter （5-15 m and 10-50 m, respectively）, and represent a serious hazard for the local population, as testified by the several asphyxia casualties that have been repeatedly occurred within these morphological depressions. In this work, the chemical and isotopic compositions of the Mt. Amiata ＂CO2-rich gas vents＂ and the estimation of both the CO2 flux from the soil and the CO2 distribution in air of their surroundings, has been carried out in order to： （1） assess the origin of gases, （2） recognize the mechanism of formation for these gas emissions and their relationship with local tectonics, and （3） to evaluate the CO2 hazard in the high flux emanations. The chemical composition of the gases is largely dominated by CO2 （up to 98 % by vol） and shows relatively high concentrations of N2, CH4 and H2S （up to 1.1%, 0.9% and 3.9 % by vol, respectively）. These features, coupled with the carbon and nitrogen isotopic signatures, suggest that the origin of the main gas compounds may be related to the contribution of deep （i.e., thermometamorphic processes on carbonate formations for CO2） and shallow （i.e. thermal decomposition of organic material for CH4, N2 and H2S） sources.  相似文献   

The acid neutralizing capacity （ANC） of South Africa＇s freshwater ecosystems     

Stephanie de Villiers 《中国地球化学学报》2006,25(B08):146-146

Acidification is considered the most important one of the primary chemical stress factors that impact on freshwater ecosystems. In unpolluted freshwater systems, the primary controls on the degree of acidification are factors such as the geological substrate of the catchment area, the presence of organic acids secreted by vegetation in the river system, and equilibrium exchange of carbon dioxide with the atmosphere. Anthropogenic factors that can impact on the degree of acidification of freshwater systems include agricultural, mining and industrial activities, either through direct runoff into river systems or through deposition of atmospheric pollutants from these sources. The capacity factors alkalinity and acidity, which represent the acid- and base-neutralizing capacity （ANC and BCN） of an aqueous system, have been used as more reliable measures of the acidic character of freshwater systems than pH. Unlike pH, ANC and BNC are not affected by parameters such as temperature and pressure. Therefore, ANC has been employed as a predictor of biological status in critical load assessments. Freshwater systems with ANC＇s eq/L isμeq/L are considered sensitive to acidification, ANC=0 μbelow 150 commonly used as the predictor for fish species such as trout in lakes, and an eq/L as more realistic for streams. Acid-neutralizing capacity μANC value of 40 （ANC） can be determined by titration with a strong acid to a preselected equivalence point. Alternatively, it can be calculated as the difference between base cations （[BC]） and strong acid anions （[SAA]）： ANC=[BC]- [SAA]=[Ca^2＋]＋[Mg^2＋]＋[Na^＋]＋[K^＋]-[SO4^2-]-[NO3^-]-[Cl^-] To date, there has been no attempt to establish the ANC of South Africa＇s freshwater ecosystems or variability therein, despite the fact that long-term water quality monitoring data exist for all the parameters needed to calculate it according to the above equations. As a result, the relationship between the acid neutralizing capacity of freshwater ecosystems in South Africa and biodiversity factors, such as fish status, is unknown. Results of the first comprehensive （country-wide scale） evaluation of the acid neutralizing capacity of river systems in South Africa will be presented. Long-term monitoring data obtained from the Department of Water Affairs and Forestry （DWAF） from most of South Africa＇s river systems were used to establish geographic and temporal variabilities in ANC. The results show that the Berg and Breede River systems are most susceptible to acidification, and that geological substrate appears to explain most of the geographic variabilities observed.  相似文献   

Peak discharge of a Pleistocene lava-dam outburst flood in Grand Canyon, Arizona, USA   总被引：1，自引：0，他引：1  

Cassandra R. Fenton  Robert H. Webb 《Quaternary Research》2006,65(2):324-335

The failure of a lava dam 165,000 yr ago produced the largest known flood on the Colorado River in Grand Canyon. The Hyaloclastite Dam was up to 366 m high, and geochemical evidence linked this structure to outburst-flood deposits that occurred for 32 km downstream. Using the Hyaloclastite outburst-flood deposits as paleostage indicators, we used dam-failure and unsteady flow modeling to estimate a peak discharge and flow hydrograph. Failure of the Hyaloclastite Dam released a maximum 11 × 10⁹ m³ of water in 31 h. Peak discharges, estimated from uncertainty in channel geometry, dam height, and hydraulic characteristics, ranged from 2.3 to 5.3 × 10⁵ m³ s⁻¹ for the Hyaloclastite outburst flood. This discharge is an order of magnitude greater than the largest known discharge on the Colorado River (1.4 × 10⁴ m³ s⁻¹) and the largest peak discharge resulting from failure of a constructed dam in the USA (6.5 × 10⁴ m³ s⁻¹). Moreover, the Hyaloclastite outburst flood is the oldest documented Quaternary flood and one of the largest to have occurred in the continental USA. The peak discharge for this flood ranks in the top 30 floods (>10⁵ m³ s⁻¹) known worldwide and in the top ten largest floods in North America.  相似文献