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1.
The pervious lateral bars (parafluvial zone) and beds (hyporheic zone), where stream water and groundwater exchange, are dynamic sites of hydrological and biological retention. The significance of these biogeochemical ‘hotspots’ to stream and groundwater metabolism is largely controlled by filtration capacity, defined as the extent to which subsurface flowpaths and matrix hydraulic conductivity modify water characteristics. Where hydraulic conductivity is high, gradients in biogeochemistry and microbial activity along subsurface flowpaths were hypothesized to be less marked than where hydraulic conductivity is low. This hypothesis was tested in two riffles and gravel bars in an Australian subtropical stream. At one site, gradients in chemical and microbial variables along flowpaths were associated with reduced hydraulic conductivity, longer water residence time and reduced filtration capacity compared with the second site where filtration capacity was greater and longitudinal biogeochemical trends were dampened. These results imply that factors affecting the sediment matrix in this subtropical stream can alter filtration capacity, interstitial microbial activity and biogeochemical gradients along subsurface flowpaths. This hydroecological approach also indicates potential for a simple field technique to estimate filtration capacity and predict the prevailing hyporheic gradients in microbial activity and biogeochemical processing efficiency, with significant implications for stream ecosystem function. 相似文献
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Simple yet physically based models to evaluate stream–aquifer interactions during a flooding event subject to triangular stream stage variation were developed in this study. The results from the developed models were compared with other analytical and numerical solutions and noted to be very accurate. The study fills an important gap with regard to available analytical and semi-analytical solutions for modeling stream–aquifer interactions, which can be used for evaluating numerical codes. In particular, the developed models are very useful to obtain preliminary insights with regard to bank storage in ungaged watersheds as required for watershed management and planning studies in rapidly urbanizing watersheds. The utility of the model is illustrated by applying it to study the effects of urbanization on stream–aquifer interactions in the Arroyo Colorado River Watershed along the US–Mexico border region. The results indicate that increased urbanization reduces the amount of influx into the banks. The reduction in flood passage time was noted to have a greater impact than the associated rise in stage. The presence of a semi-permeable barrier was seen to mask the effects of urbanization. The model results also implicitly highlight the importance of how water quality variations caused due to urbanization can affect stream–aquifer interactions. 相似文献
4.
应用流量历时曲线分析黄土高原水利水保措施对河川径流的影响 总被引：2，自引：0，他引：2
流量历时曲线（Flow Duration Curve,FDC）是用于分析流域径流特征及其变化的有效方法之一。以长序列日流量为基础,采用FDC方法并结合各流域的径流量时间变化趋势分析方法,研究了黄土高原佳芦河、秃尾河、延河和湫水河等4条流域流量变化的基本特征;通过临界年份前后两个时段序列及不同年代序列的流量历时曲线变化的比较,分析了流域径流过程对大面积水土保持措施的响应。结果表明：随水土保持措施累积面积的不断增大,佳芦河、湫水河、秃尾河的径流量逐年减少,且水土保持措施对高流量部分径流减少的程度较低流量部分大,尤以工程措施为主的湫水河流量减少最明显。在延河流域,与临界年份前的时段相比,后期的高流量部分的径流量减小,而常水和低流量部分的径流量相对增大。尽管流域水土流失综合治理并未使河川径流量增加,但由于高流量部分流量的减少程度较低流量部分径流量减少程度大,从而使流域年内日径流量变化过程趋于均匀化。 相似文献
5.
The suitability of floodplain sediment as a global sampling medium: evidence from China 总被引：2，自引：0，他引：2
Research undertaken by IGCP 259 (International Geochemical Mapping) indicates that wide-spaced sampling is a fundamental concept of international geochemical mapping as it appears to provide the only practical way to obtain a relative rapid (10–20 years) overview of global geochemistry. The main aim of this study is to test the suitability of floodplain sediment as a global sampling medium.Thirteen floodplain sediment samples and 13 stream sediment samples were taken at the exit of 13 super large drainage basins (SCB). The areal extents of these basins are in the order of 1000–10,000 km2. Within each SCB, 3–11 stream sediment samples each representing a component catchment basin (CCB) of 100–1000 km2 were also taken. Fourty nine elements were analyzed. The results were compared with the average values derived from calculating thousands of stream sediment data available from China's National Geochemical Mapping (RGNG) program. Strong similiarities were demonstrated in distribution and trends among the three levels of data. The set of floodplain sediment data shows great coincidence with RGNR stream sediment data. 相似文献
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D.Conrad Gregoire 《Journal of Geochemical Exploration》1985,23(3):299-313
The extraction of organically bound gold from surficial materials is accomplished by using a solution of 5% sodium hypochlorite. A 10-g sample is digested at least twice with 50 mL of hypochlorite solution. The recovery of gold from the organic phase is nearly quantitative for lake sediments and stream sediments high in organic content. For stream sediments and soils low in organics, the recovery of gold is complicated by the sorption of released gold onto inorganic sample components. For these materials, recoveries as low as 70% of the organically bound gold are possible. For a stream sediment sample containing 53.4 ppb gold, the precision of the method is approximately 6% for a 10-g sample and 14% when a 5-g sample of stream sediment is used. The results obtained for all materials tested indicate that a substantial fraction of the gold found in sediments and soils exists as organically bound gold. 相似文献
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Samples of stream sediments were collected along two streams adjacent to a sanitary landfill. One of the streams drained the landfill directly. In addition, control of background samples were also analyzed from a stream not affected by the landfill. All samples were analyzed for Ag, Zn, Cu, Cd, and Pb content using atomic adsorption techniques. The pH of the three streams were monitored since pH differences in the streams may affect the quantities of metals adsorbed or precipitated on the sediments. The comparison between the content of Ag, Zn, and Cu in the sediments of the two study streams and the same metals in the control sediments indicated the landfill emitted these metals into the two adjacent streams. However, since the Cd and Pb contents in the sediments of both streams were similar to that of the control stream sediments, these metals may not be emitted into the two study streams from the landfill and they represent only background quantities. The comparisons of each metal in the sediments of each stream were made by the use of a metal trend chart, the individual calculated mean metal content values, and by the statistical two sample t-test. No decreasing trends of the quantities of Ag, Zn, or Cu as a function of increasing distance from the landfill was present in the sediments along the stream that drained the landfill directly. These sediments might have been affected by stream action and became mixed with other sediments downstream. 相似文献
8.
Flávia Maia Cláudia Pinto João Carlos Waerenborgh Mário A. Gonçalves Cátia Prazeres Ondina Carreira Susana Sério 《Applied Geochemistry》2012
This work focuses on the geochemical processes taking place in the acid drainage in the Ribeira da Água Forte, located in the Aljustrel mining area in the Iberian Pyrite Belt. The approach involved water and stream sediment geochemical analyses, as well as other techniques such as sequential extraction, Mössbauer spectroscopy, and X-ray diffraction. Ribeira da Água Forte is a stream that drains the area of the old mine dumps of the Aljustrel mine, which have for decades been a source of acid waters. This stream flows to the north for a little over than 10 km, but mixes with a reduced, organic-rich, high pH waste water from the municipal waste water pools of the village. This water input produces two different results in the chemistry of the stream depending upon the season: (i) in the winter season, effective water mixing takes place, and the flux of acid water from the mine dumps is continuous, resulting in the immediate precipitation of the Fe from the acid waters; (ii) during the summer season, acid drainage is interrupted and only the waste water feeds the stream, resulting in the reductive dissolution of Fe hydroxides and hydroxysulfates in the stream sediments, releasing significant quantities of metals into solution. Throughout the year, water pH stays invariably within 4.0–4.5 for several meters downstream of this mixing zone even when the source waters come from the waste water pools, which have a pH around 8.4. The coupled interplay of dissolution and precipitation of the secondary minerals (hydroxides and sulfates), keeps the system pH between 3.9 and 4.5 all along the stream. In particular, evidence suggests that schwertmannite may be precipitating and later decomposing into Fe hydroxides to sustain the stream water pH at those levels. While Fe content decreases by 50% from solution, the most important trace metals are only slightly attenuated before the solution mixes with the Ribeira do Rôxo stream waters. Concentrations of As are the only ones effectively reduced along the flow path. Partitioning of Cu, Zn and Pb in the contaminated sediments also showed different behavior. Specific/non-specific adsorption is relevant for Cu and Zn in the upstream branch of Ribeira da Água Forte with acid drainage conditions, whereas the mixture with the waste water causes that the association of these metals with oxyhydroxide to be more important. Metals bound to oxyhydroxides are on the order of 60–70% for Pb, 50% for Cu and 30–60% for Zn. Organic matter is only marginally important around the waste water input area showing 2–8% Cu bound to this phase. These results also show that, although the mixing process of both acid and organic-rich waters can suppress and briefly mitigate some adverse effects of acid drainage, the continuing discharge of these waste waters into a dry stream promotes the remobilization of metals fixed in the secondary solid phases in the stream bed back into solution, a situation that can hardly be amended back to its original state. 相似文献
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The geochemical dispersion, in an arid environment, of Pb and Zn in stream sediments is examined with respect to size fractions and depth of sampling in a stream draining the Gamsberg Zn orebody.Sampling results indicate that there is a well-developed drainage train for approximately 8 km from the orebody for both Pb and Zn. The length of the drainage train is similar for both the minus 80 and minus 200-mesh size fractions but it is less for the minus 10, plus 40-mesh fraction.Higher metal values were obtained from samples taken from the surface of the stream bed. Metal values are generally lower in samples collected below the surface of the stream bed. The sampling position within the stream channel is not important.Sampling of the magnetite fraction from the stream sediments produced a well-defined Zn train for a distance of 14 km from the orebody. This train is more significant than the train found by normal sediment sampling. 相似文献
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In trial analyses of a series of n-alkanes, precise determinations of 13C contents were based on isotopic standards introduced by five different techniques and results were compared. Specifically, organic-compound standards were coinjected with the analytes and carried through chromatography and combustion with them; or CO2 was supplied from a conventional inlet and mixed with the analyte in the ion source, or CO2 was supplied from an auxiliary mixing volume and transmitted to the source without interruption of the analyte stream. Additionally, two techniques were investigated in which the analyte stream was diverted and CO2 standards were placed on a near-zero background. All methods provided accurate results. Where applicable, methods not involving interruption of the analyte stream provided the highest performance (sigma = 0.00006 at.% 13C or 0.06% for 250 pmol C as CO2 reaching the ion source), but great care was required. Techniques involving diversion of the analyte stream were immune to interference from coeluting sample components and still provided high precision (0.0001 < or = sigma < or = 0.0002 at.% or 0.1 < or = sigma < or = 0.2%). 相似文献
12.
Xu Chengcheng Wu Chu Li Tianchen Lu Chuiyu He Xin Sun Qingyan Qin Tao Yan Lingjia 《Hydrogeology Journal》2022,30(6):1789-1800
The widely used groundwater flow model MODFLOW offers a range of software packages to simulate the interaction between streams and groundwater in aquifer systems. However, these existing packages lack a general method to address the chaotic simulation sequences of stream segments and require these segments to be ordered by modelers as input to the code. Therefore, it is challenging to simulate a stream network divided into a large number of segments such as a canal irrigation system. In this study, the Streamflow Automatic Routing (SAR) package was developed, and an effective method is proposed to automatically determine the segment simulation sequence. The stream segment order in the SAR input file is arbitrary, which allows modifications of the stream network by removing segments directly and adding segments at the end of the segment group. This mainly includes two processes: scanning all the outlet channels of the water system and calling the recursive algorithm for each outlet channel of the water system. The SAR package was tested using a hypothetical stream–aquifer system and applied to a complex flow field in Aiding Lake of Turpan Basin, China. In the results, a close fitting between the simulation and observations shows that the SAR package precisely simulated the exchange flux between the steams and aquifer. The SAR package can significantly improve the efficiency of simulations in a complex stream network, and it can be widely used as a subroutine package of MODFLOW in agricultural irrigation areas where rivers and canals are interlaced.
相似文献13.
Analysis of the relationship between the stream regulations and the geomorphologic effects of floods 总被引：1，自引：0，他引：1
Jakub Langhammer 《Natural Hazards》2010,54(1):121-139
This article presents the results of analysis of relationships between stream regulations and the geomorphic effects of floods
for the case of the Blanice river basin in the Czech Republic, which was at the center of an extreme flooding event that impacted
Central Europe in August 2002. The assessment is based on a geostatistical analysis of data on the distribution of flood effects
and stream modifications acquired by field survey and completed by historical maps and digital cartography. Using the cluster
analysis and regression tree classification, relationships between the occurrence of erosion and deposition forms, and the
parameters of stream modification and general physiography were tested. The results indicate a limited relationship between
stream modifications and the occurrence of geomorphic effects of the flood. The cluster analysis detected different sets of
parameters linked to erosion and accumulation. The accumulation was related to physiographic properties of stream, while erosion
was related to the presence of weirs in the stream segment. The regression tree classification demonstrates the potentially
critical combinations of stream modifications related to the occurrence of flood effects. 相似文献
14.
A regional geochemical survey using soils, stream sediment and stream water sampling revealed multi-element geochemical anomalies, though of low environmental mobility, associated with Mesozoic sedimentary ironstones in Lincolnshire, UK. The most prominent of these anomalies were of As and V in soils and sediments, but elevated levels of elements such as Cr, La, Ce and Th were also observed. These were initially thought to be part of a residual resistate element or heavy-mineral suite, but careful examination suggests that these too may be primarily associated with the process of Fe oxide precipitation during the initial formation of the ironstones. 相似文献
15.
This study is aimed at determining the level of environmental degradation as well as the concentration of trace elements in soil and stream sediments in order to evaluate the environmental impact of the mining operation. Twenty-five (25) soils and ten (10) stream sediment samples were collected from the study area. The physicochemical parameters were determined using appropriate instrumentation with the aid of a digital pH meter (Milwaukee meter) to measure the pH and electrical conductivity, total dissolved solids, moisture content and loss on ignition of the soil and stream sediment samples. The pH of the soil sample ranged from (6.10 to 7.19); Electrical conductivity ranged from (21.3 to 279.4 µS/cm), moisture content varied from (0.60% to 7.20%), and the LOI ranged from (2.03% to 18.62%). The results of the analysis showed that the concentrations of the trace elements in the soils and stream sediment samples were slightly higher than the background values. Plots of the trace elements in stream sediment samples show moderate, consistent decrease downstream except at points where there was mine water discharge into the main river. The pollution levels of heavy metals were examined in stream sediment and soil samples using different assessable indices, such as the enrichment factor, which showed significant-moderate enrichment for Cr, Th, Nb, Zn, Pb, Y and Zr and the geo-accumulation index, which showed practically moderate contamination with Cr, Ni and Sr based on regional background reference values. Geo-accumulation index and contamination index for soils and stream sediment revealed uncontaminated to moderate contamination. Likewise, elements with moderate contamination were Cr, Ni and Sr. The Pearson correlation showed that there were significant positive associations among selected metals in soil and stream sediment samples. 相似文献
16.
Patrick Walsh 《Hydrogeology Journal》2008,16(8):1459-1467
A novel method for analyzing the effects that stratigraphic layers and joints have on spring locations is presented, with specific relevance for the southern Sacramento Mountains, south central New Mexico, USA. Bedrock in this heavily vegetated mountain block is mostly covered by alluvium and soil, making direct field observations difficult, and necessitating alternative methods. Elevations of a mapped geologic contact are used to produce a three-dimensional stratigraphic surface. A histogram of spring stratigraphic positions, calculated from this surface, indicates zones of preferential groundwater flow. Field measurements are combined with GIS analyses to quantify joint control on spring locations within stream valleys, and these results are compared to traditional lineament analysis. Stream valleys are parallel to joints observed in the field, and joint-parallel segments selected from digital elevation model (DEM)-mapped streams are up to 900 m in length. The abundance of springs throughout the study area decreases logarithmically with distance from these joint-parallel stream segments. Springs are more than twice as abundant within 25 m of joint-parallel stream segments compared with manually mapped lineaments from air-photos. Higher correlation with spring locations and significant time reduction by using GIS to select joint-parallel streams for lineament interpretation indicate that the method provides a good alternative to manual lineament analysis. 相似文献
17.
Hydrological systems have been seriously affected by changes of glaciations and snow covers in Mount Gongga, Sichuan, China, but the relevance of ice-snow melt for alpine river basin hydrology is so far not well known. To better understand hydrological features of the Hailuogou River, changes of δ18O and δ2H were investigated by analyzing 117 water samples collected from May 2008 to November 2009. Our results show that the stream water contains a relatively intermediate magnitude of isotopic variations, with δ18O ranging from ?18.09 to ?13.08 ‰ and δ2H from ?126.5 to ?88.8 ‰. The average values are both higher than those of ice-snow meltwater, but lower than those of meteoric water. These data also show a gradually increasing trend from upstream to downstream, and these changes might document the fingerprint of ice-snow melt in the headwater region and indicate the increasing recharge of heavy isotope-enriched waters with flow distance. The similarity in slopes of δ2H and δ18O relationship for meteoric waters and stream waters suggests that the isotopic signature of precipitation is well preserved in stream flow, and during the rainfall and stream flow the evaporation is only minor. Based on δ18O model, the results suggested that the fraction of ice-snow meltwater input over the total stream flow ranged from 84.50 to 86.52 % in the headwater region, but the fraction of ice-snow meltwater input from upper basin downward was significantly decreased. The study demonstrates that ice-snow meltwater is a substantially important water source in alpine regions on the edge of Tibetan Plateau. 相似文献
18.
Kyaw Zay Ya Tsubasa Otake Aoi Koide Kenzo Sanematsu Tsutomu Sato 《Resource Geology》2020,70(3):296-308
Mining operations in the Pinpet Fe deposit, which is the second‐largest Fe deposit in Myanmar, are currently suspended, in part because of possible contamination of heavy metals and hazardous elements (e.g., Fe, As, Cu, Zn, and U) into the surrounding aquatic environment and associated public concern. However, a scientific investigation of the source and degree of contamination in streams near the deposit has not yet been conducted. Therefore, we quantified heavy‐metal and hazardous‐element concentrations of stream waters and sediments in stream beds, and measured the speciation and concentration of these metals in deposit Fe ores using the sequential extraction method, to better understand the influence of mining activities on the surrounding environment. Geochemical results for Nan‐tank‐pauk stream and its tributaries indicate that the chemical compositions of their waters are controlled by carbonate bedrock and that no detectable contamination has occurred as a result of mining activity or hematite and limonite ore beneficiation processes in either the wet or dry seasons. All measured heavy‐metal and hazardous‐element concentrations were below the World Health Organization standards for drinking water and the proposed national drinking water quality standards in Myanmar. Bulk chemical compositions of stream‐bed and tailings dam sediments show that As, Zn, and Cu concentrations are similar to those in uncontaminated sediments. Results of bulk mineralogical and chemical analyses of ore samples reveal that some limonite ore samples contain substantial amounts of As (up to 2 wt%). However, sequential extraction results indicate that most (>90%) of the As in these As‐rich ores is hosted in insoluble fractions (e.g., crystalline Fe hydroxides and clays). Therefore, arsenic is unlikely to be released into the aquatic environment by interacting with water during ore beneficiation processes should the mine resume operations. 相似文献
19.
A method to estimate stream conveyance losses, including stream bank seepage and evapotranspiration from riparian areas, was developed for the Truckee River in California and Nevada (USA). Aquifer diffusivity is the primary variable required to compute aquifer head and seepage. Head and seepage conceptual models developed in previous studies were calibrated using stream stage and aquifer head at five sites along the Truckee River. The equations for head require numerical convolution to solve. It was found that head is insensitive to diffusivity and a single value for diffusivity provides good results at all study sites. Also, because releases from storage are usually prescribed as a step increase in flow for a given period of time followed by a step decrease in flow, an analytic solution for volume of seepage can be used in place of numerical convolution. Under typical operating conditions, seepage volume represents a small fraction of the total reservoir releases. Uncertainty in seepage estimates can be reduced with increased accuracy in hydraulic conductivity. This work demonstrates a valuable technique to estimate conveyance losses under natural and managed stream flow. 相似文献
20.
The role of megatides and relative sea level in controlling the deglaciation of the British–Irish and Fennoscandian ice sheets 
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下载免费PDF全文 Key external forcing factors have been proposed to explain the collapse of ice sheets, including atmospheric and ocean temperatures, subglacial topography, relative sea level and tidal amplitudes. For past ice sheets it has not hitherto been possible to separate relative sea level and tidal amplitudes from the other controls to analyse their influence on deglaciation style and rate. Here we isolate the relative sea level and tidal amplitude controls on key ice stream sectors of the last British–Irish and Fennoscandian ice sheets using published glacial isostatic adjustment models, combined with a new and previously published palaeotidal models for the NE Atlantic since the Last Glacial Maximum (22 ka BP). Relative sea level and tidal amplitude data are combined into a sea surface elevation index for each ice stream sector demonstrating that these controls were potentially important drivers of deglaciation in the western British Irish Ice Sheet ice stream sectors. In contrast, the Norwegian Channel Ice Stream was characterized by falling relative sea level and small tidal amplitudes during most of the deglaciation. As these simulations provide a basis for observational field testing we propose a means of identifying the significance of sea level and tidal amplitudes in ice sheet collapse. 相似文献