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1.
Open-marsh water management (OMWM) manipulates selected areas of an estuarine marsh by constructing narrow, deep ditches that harbor resident populations of predators of mosquito larvae. It does not, however, alter the surrounding vegetation by deposition of spoil mounds. We censused the summer (breeding and nonbreeding) bird populations in two adjacent salt marsh sites on Topsail Island, North Carolina, for two summers before OMWM ditching occurred and for four seasons postditching. A total of 53 nonbreeding species and five breeding species of birds were encountered on the study sites. None of the interannual changes in bird populations can be attributed to OMWM.  相似文献   

2.
Sampling theC. septemspinosa population of the Mystic River Estuary simultaneously in deep water and along the shoreline indicated that this population has two major reproductive periods. Berried females move into the estuary in early spring and late autumn to hatch their eggs. Two-and three-year-old females produce the larvae in the spring and 1.0- to 1.5-year-old females give rise to the larvae in winter. All larvae are carried seaward by the tidal currents and eventually settle as juveniles in the deep water near the mouth of the estuary or on the continental shelf. Juveniles from the spring hatch migrate to the shallow shoreline where they grow, rapidly, 0.15 mg/day. Those that hatch during the late autumn do not migrate shoreward. A model of this life cycle and evidence to support two recruitment mechanisms that involve inshore migration of adults and the offshore drift of the larvae are presented.  相似文献   

3.
This study discusses impacts of saline water irrigation and shrimp pond discharges on the surrounding waters in the coastal Cai Nuoc district, Mekong delta of Vietnam where the landscape was re-shaped by shrimp aquaculture since 2000. Sampling took place at the end of the wet season of 2009 in the district (as aquaculture sites) and a nearby freshwater-dominated reference site. The aquaculture sites showed significantly higher salinities and organic loadings (biochemical oxygen demand, chemical oxygen demand) but lower dissolved nutrients (NO3–N, NO2–N, and PO4–P), total iron, and phytoplankton diversity compared to the reference site. Irrigation of saline waters has exacerbated salinization, leading to significant biological changes in the surrounding waters. Impacts of shrimp pond discharges on the surrounding waters were not very dramatic in terms of organic loadings and nutrients. The increase in organic loadings in the surrounding waters was mostly due to contribution from other pollution sources, such as domestic/industrial discharges and runoff. Enhanced salinization and changes in nutrients resulted in a decline in species richness and diversity, and a change in the evenness of the phytoplankton community. Besides, the composition of zooplankton and zoobenthos were also restructured. The mild impacts of shrimp pond discharges on the surrounding waters were primarily due to the limited inputs for shrimp aquaculture in this area.  相似文献   

4.
Analyses by inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and cold vapour atomic absorption (for Hg, CVAA) of a wide range of elements in some 300 surface water samples from the Salar de Uyuni and Salar de Coipasa catchments of the Bolivian Altiplano have been undertaken. Comparison of analyses of acidified aliquots of unfiltered sample water with water filtered at 0.45 μm reveals that the following elements are not affected significantly by filtration in this high-pH environment: B, Ca, Li, Mg, K, Si, Na, Sr, S. The following elements appear to experience significantly elevated concentrations in unfiltered samples, relative to filtered: Al, (As to a minor extent), Ba, Be, Cd, Cr, Co, Cu, Fe, Pb, Mn, Hg, Ni, P, Ag, Tl, Ti, V. The effect appears to be related to the presence, and subsequent dissolution in acid preservative, of Fe-, Al-or Mn-oxyhydroxide flocs (or coatings on silicate particles) in unfiltered samples, and their retention or precipitation on filters.  相似文献   

5.
The relationship between surface water and groundwater not only influences the water quantity, but also affects the water quality. The stable isotopes (δD, δ 18O) and hydrochemical compositions in water samples were analysed in the Second Songhua River basin. The deep groundwater is mainly recharged from shallow groundwater in the middle and upper reaches. The shallow groundwater is discharged to rivers in the downstream. The runoff from upper reaches mainly contributed the river flow in the downstream. The CCME WQI indicated that the quality of surface water and groundwater was ‘Fair’. The mixing process between surface water and groundwater was simulated by the PHREEQC code with the results from the stable isotopes. The interaction between surface water and groundwater influences the composition of ions in the mixing water, and further affects the water quality with other factors.  相似文献   

6.
The effect of wind speed and bed slope on sand transport   总被引:7,自引:0,他引:7  
This paper reports on a wind tunnel study of the effects of bed slope and wind speed on aeolian mass transport. The use of a sloping wind tunnel has enabled estimation of the friction angle α to be about 40° for saltating particles in the range 170–540 μm. A formula relating dimensionless mass transport to friction speed and bed slope is proposed, and mass transport data for five uniform sand samples and one non-uniform sand sample are shown to fit the equation well. In particular, the relationship reveals an overshoot in mass transport slightly above threshold collisions, a feature also evident when previous experimental data is re-examined. As the number of mid-air collisions between the saltating particles increases greatly with wind speed, the overshoot may occur as a result of increasing energy losses resulting from the collisions. Finally, it is demonstrated that data for saltating snow shows a similar overshoot in the dimensionless transport rate.  相似文献   

7.
8.
地表水入渗对垃圾填埋场水质水量影响的数值模拟分析   总被引:3,自引:0,他引:3  
赵颖  梁冰  薛强  刘磊 《岩土力学》2010,31(7):2295-2302
将填埋垃圾视作一种特殊土体,建立了综合描述垃圾填埋场内渗滤液水分的饱和-非饱和渗流、垃圾土体沉降变形、有机污染物的释放、迁移、转化,以及微生物的生长、衰减等物理化学过程的多场耦合仿真分析模型,将任意的Lagrangian- Eulerian(ALE)方法引入到模型求解中,基于自行开发的仿真分析程序,开展了地表水入渗对垃圾填埋场水质、水量影响的数值仿真分析研究。模拟结果表明:300 d的非饱和水分入渗及内源水产生可使填埋单元内渗滤液饱和液面最高达6 m;地表水入渗对水相可溶性可降解有机物浓度和厌氧微生物浓度具有显著的影响,并间接地影响固相可溶性可降解有机物和微生物的浓度分布。  相似文献   

9.
Groups of embryonic grass shrimp,Palaemonetes pugio, were exposed to 0.1 and 0.3 mg/l cadmium at 30 ppt salinity and 25°C for the last 1, 4 or 8 days prior to hatching. Other groups of embryos were cultured in uncontaminated seawater. Prehatch exposure to cadmium was found to have no additive effect on the sensitivity of the larvae to cadmium exposure and salinity stress for 14 days after hatching. Only one group of larvae, exposed to 0.1 mg/l cadmium for 4 days before hatching, and transferred to 10 ppt salinity water containing 0.1 mg/l cadmium after hatching, showed a significant (X 2, P<0.05) decrease in survival, compared to control survival. No significant decreases in survival were observed for any larvae transferred to 15 and 30 ppt salinity at a pre- and posthatch cadmium concentration of 0.1 mg/l. At a pre- and posthatch cadmium concentration of 0.3 mg/l, significant decreases in survival were observed for all of the larvae transferred to 10 and 15 ppt salinity after hatching. Significant decreases in survival were observed for only 2 of the groups exposed before hatching and transferred to 30 ppt salinity and 0.3 mg/l cadmium after hatching.  相似文献   

10.
河砂既是矿产资源,也是宝贵的环境资源,具有涵养水分、保护环境的作用。河砂资源的过度开采,既引起了河岸坍塌地质灾害,又对沿河水环境特别是地下水环境造成破坏。大汶河河砂开采造成了河岸坍塌、河桥报废。使沿河第四系孔隙水和旧县水源地岩溶地下水水位下降,地下水开采资源减少,水质变差。分析结果表明,大汶河河砂的过度开采,不利于环境保护、不利于长远经济和社会效益,应予取缔或严格限制开采规模。  相似文献   

11.
按照建设部的总体要求,在山东省建设厅、建管局的指导下,青岛市建委从2005年3月份开始,借鉴现代工业管理的成熟理念和经验,以“人本化、秩序化、程序化、数字化”管理为目标,决定利用二年的时间,使全市建筑施工现场安全生产全部实现标准化管理。经过近一年的实践,我市的安全质量标准化工作有了初步成效。  相似文献   

12.
The petrography and powder diffraction analyses were integrated to study the effect of diagenesis on the reservoir quality of the Mamu Sandstone in areas around Enugu, southeastern Nigeria. The sands are moderately to well sorted, very fine to fine grained feldspathic arenite deposited in diverse environments of upper to lower shoreface and sub-environments of delta plain. Pressure solutions, authigenic clays and quartz and feldspar overgrowths are the main diagenetic features of the sandstones in the area. These diagenetic features result in mechanical and chemical compaction, alteration of framework grains and precipitation of dissolved grains. In varying degrees, coating of clasts and filling of pore-spaces by clay and heavy minerals reduced the pore throat diameter, which caused mild reduction of the porosity and permeability of sands. Despite these observed diagenetic effects, the Mamu sands still have the potential to serve as good hydrocarbons reservoir especially for gas.  相似文献   

13.
潍河流域下游地表污水对地下水水质影响的状态分析   总被引:1,自引:0,他引:1  
术洪亮  魏保军 《吉林地质》1999,18(2):37-41,76
为了准确地建立莱洲湾南岸地区虞河段地表水与地下水污染质运移的数学模型,本文对研究区地下水及地表水污染特征及其污染现状进行了调查、分析,为地下水资源的合理利用开发提供了依据。  相似文献   

14.
The disordering kinetics of Al/Si in albite depend on how the samples are dried, and thus on the presence of trace amounts of water. The disordering rate increases with water content and confining pressure. At 10 kb the activation energy is about 67 kcal/mole compared to about 87 kcal/mole for samples disordered in air. Simultaneous plastic deformation increases the disordering rate and the effect is most pronounced below 900° C at 10?6/s. Some albite ordering and microcline disordering experiments show similar kinetic behavior. These results are significant for interpreting the structural state and the high-temperature deformation of feldspars.  相似文献   

15.
The groundwater abstracted at a well field near the Yamuna River in Central Delhi, India, has elevated ammonium (NH4 +) concentrations up to 35 mg/L and arsenic (As) concentrations up to 0.146 mg/L, constituting a problem with the provision of safe drinking and irrigation water. Infiltrating sewage-contaminated river water is the primary source of the NH4 + contamination in the aquifer, leading to reducing conditions which probably trigger the release of geogenic As. These conclusions are based on the evaluation of six 8–27-m deep drillings, and 13 surface-water and 69 groundwater samples collected during seven field campaigns (2012–2013). Results indicate that losing stream conditions prevail and the river water infiltrates into the shallow floodplain aquifer (up to 16 m thickness), which consists of a 1–2-m thick layer of calcareous nodules (locally known as kankar) overlain by medium sand. Because of its higher hydraulic conductivity (3.7 × 10?3 m/s, as opposed to 3.5 × 10?4 m/s in the sand), the kankar layer serves as the main pathway for the infiltrating water. However, the NH4 + plume front advances more rapidly in the sand layer because of its significantly lower cation exchange capacity. Elevated As concentrations were only observed within the NH4 + plume indicating a causal connection with the infiltrating reducing river water.  相似文献   

16.
The paper covers some results of laboratory and nature experiments on studying the effect of oil films on water evaporation rate and oxygen concentration in sea water. It is demonstrated that oil films on the sea surface reduce the rate of water evaporation by 15 to 33% due to diffusion resistance of oil film as well as energy resistance of monolayer of surface active substances at the film-water interface. Large oil spots may cause, in areas oversaturated with oxygen, increase of oxygen concentration in sea water under the oil spot due to decrease of gas exchange rate at the sea-atmosphere interface.  相似文献   

17.
The hydrochemical composition of surface water and groundwater is a key parameter for understanding the evolution of water and its quality.In particular, little is known about the impact of transferred water on surface water and groundwater.In this study, Baiyangdian Lake was selected as a typical area for extensive groundwater exploration and surface water transfer in the North China Plain.Surface water and groundwater samples were sampled in dry/wet seasons and then analyzed before/after the water transfer, respectively.Generally, surface water and groundwater are extensively hydrologically connected based on hydrochemical evidence.It was found that the hydrochemical composition of the shallow groundwater is affected by the surface water and that the water quality of the deep groundwater is stable.However, inter-aquifer recharge processes from the shallow groundwater to the deep groundwater existed in the anthropogenic region impacted with high nitrate-ion concentrations.Also, the hydrochemical composition of the surface water and groundwater was dominated by rock-weathering and evaporation-precipitation processes.Due to the existence of the deep vadose zone in the alluvial fan, Na~+was exchanged into soil matrices during the leakage of the surface water.In addition, the transferred water resulted in surface water with good quality, and it also played as an important recharge source to groundwater.As the most important water resource for irrigation and drinking, deep groundwater should be paid more attention in the alluvial fan with frequent water transfer and extensive groundwater exploration.  相似文献   

18.
19.
Liu  Xin  Li  Sa  Yin  Jiangsong  Li  Tingting 《Acta Geotechnica》2022,17(10):4641-4654
Acta Geotechnica - For islands in marine environments, groundwater levels vary due to the influence of tides. As a result, the external environment of backfilled carbonate sands on islands...  相似文献   

20.
The Great Zab River catchment is a major left-bank tributary of the River Tigris and drains a substantial part of the Kurdistan Region, an autonomous region of Northern Iraq. Within Kurdistan, the water resources of the Great Zab River catchment are under pressure from population increase and are utilized for potable, domestic and agricultural and industrial supply. As with many parts of the world, effective management of water resources within Kurdistan is hindered by a lack of water quality data and established background concentrations. This study therefore represents the first regional survey of river water chemistry for the Great Zab River catchment and presents data on the spatial and temporal trends in concentrations of As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Sr, Zn, NO3?, SO42?, F?, Cl? and PO43?, in addition to pH, electrical conductivity, dissolved oxygen and turbidity. As a tool for underpinning the management and monitoring of water quality, background concentrations were defined for the Great Zab catchment using three methods. The influences of geogenic and anthropogenic controls upon spatial and temporal trends in water chemistry are also evaluated. The influence of geogenic loading from underlying bedrock was identifiable within the observed spatial trends, with the most notable differences found between waters sampled from the relatively more volcanic-rich Zagros zone to the north and those sampled from the lower catchment underlain by younger clay-, sand- and siltstones. The greatest anthropogenic influence, identifiable through elements such as Cl? and NO3?, is present in the more highly populated lower catchment. The background concentrations identified in the Great Zab catchment would be those expected as a result of geogenic loading with some anthropogenic influence and represent a more conservative value when compared to those such as the World Health Organization Maximum Admissible Concentration. However, background concentrations represent a powerful tool for identifying potential anthropogenic impacts on water quality and informing management of such occurrences.  相似文献   

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