华南滨海小流域降雨入渗对地下水的补给分析

以华南滨海小流域——中山大学滨海水循环试验基地（试验基地）作为研究区,在对该流域地下水和雨水分别进行采样、实验分析的基础上,利用氯量平衡法（CMB）与地下水动态法计算了该流域的降雨入渗补给系数与给水度。研究发现,试验基地地下水主要受降雨补给,地下水埋深在雨季（4—9月）、旱季（10—3月）的变动范围大致为0～1.5 m与0～0.5 m。根据CMB计算结果,补给区、中间区雨季降雨入渗补给系数分别为旱季的1.3～1.6倍和1.3～2.0倍,且补给区大于中间区（M5井除外）。利用地下水动态法计算次降雨入渗补给系数,所得雨季、旱季的均值（7.6%和4.6%）与CMB计算结果（7.7%和5.3%）较为接近。给水度、雨强与入渗补给系数均存在一定的线性关系。将地下水埋深分别与降雨入渗补给量及潜水蒸发量进行多项式拟合对比,发现降雨入渗对地下水的最大入渗补给埋深约为2.3 m,当埋深为3.1 m时,地下水可获得最大净补给量。     

Preferential leaching of nitrate,chloride and phosphate in an Australian clay soil

This paper investigates leaching of water and nutrients (NO^‐ ₃, Cl^‐, PO^3‐ ₄) from the unsaturated layer in an Australian soil using a multisegment percolation system (MPS). Large undisturbed soil cores were collected from a clay‐based, basaltic plain, agricultural soil at Grassmere, 300 km west of Melbourne, Australia. Significant heterogeneity (or preferential flow) of effluent moisture and solutes was detected (one‐way ANO VA, p < 0.001). Fifty percent of the applied nitrate and chloride leached from the soil core within three days after initial application. Hundred percent of the applied nitrate and chloride leached from the soil core within 8 days after application. These results indicate little incorporation into the soil matrix, and possible denitrification or mineralisation. In contrast, after 18 days, less than 1 % of the total applied phosphates leached from the soil, indicating strong adsorption. Our experiments indicate considerable heterogeneity in water flow patterns and solute leaching on a small spatial scale. Very rapid transport of nitrate and chloride through the soil was evident, in comparison phosphate leaching was negligible. These results have important implications for the management of nutrient schedules in agricultural soils, particularly those located in the Western District of Victoria, Australia.     

Assessing nitrate contamination and its potential health risk to Kinmen residents

Kinmen is located in the southwest of Mainland China. Groundwater supplies 50% of the domestic water use on the island. Residents of Kinmen drink groundwater over the long term because surface water resources are limited. Nitrate–N pollution is found and distributed primarily in the western part of groundwater aquifer whereas saline groundwater is distributed to the northeastern Kinmen. This work applied the DRASTIC model to construct the vulnerability map of Kinmen groundwater. MT3D was then used to evaluate the contamination potential of nitrate–N. The health risk associated with the ingestion of nitrate–N contaminated groundwater is also assessed. The results from DRASTIC model showed that the upland crop and grass land have high contamination potential, whereas the forest, reservoir and housing land have low contamination potential. The calibrated MT3D model inversely determined the high strength sources (0.09–2.74 kg/m²/year) of nitrate contaminant located in the west to the north west area and required 2–5 years travel time to reach the monitoring wells. Simulated results of MT3D also showed that both the continuous and instantaneous contaminant sources of nitrate–N release may cause serious to moderate nitrate contamination in the western Kinmen and jeopardize the domestic use of groundwater. The chronic health hazard quotient (HQ) associated with the potential non-carcinogenic risk of drinking nitrate–N contaminated groundwater showed that the assessed 95th percentile of HQ is 2.74, indicating that exposure to waterborne nitrate poses a potential non-cancer risk to the residents of the island. Corrective measures, including protecting groundwater recharge zones and reducing the number of agricultural and non-agricultural nitrogen sources that enters the aquifer, should be implemented especially in the western part of Kinmen to assure a sustainable use of groundwater resources.     

Bioreduction of nitrate in groundwater using a pilot-scale hydrogen-based membrane biofilm reactor

A long-term pilot-scale H₂-based membrane biofilm reactor (MBfR) was tested for removal of nitrate from actual groundwater. A key feature of this second-generation pilot MBfR is that it employed lower cost polyester hollow fibers and still achieved high loading rate. The steady-state maximum nitrate surface loading at which the effluent nitrate and nitrite concentrations were below the Maximum Contaminant Level (MCL) was at least 5.9 g·N·(m²·d)^?1, which corresponds to a maximum volumetric loading of at least 7.7 kg·N·(m³·d) ^?1. The steady-state maximum nitrate surface area loading was higher than the highest nitrate surface loading reported in the first-generation MBfRs using composite fibers (2.6 g·N·(m²·d)^?1). This work also evaluated the H₂-utilization efficiency in MBfR. The measured H₂ supply rate was only slightly higher than the stoichiometric H₂-utilization rate. Thus, H₂ utilization was controlled by diffusion and was close to 100% efficiency, as long as biofilm accumulated on the polyester-fiber surface and the fibers had no leaks.     

Increased macrophyte nitrate reductase activity as a consequence of groundwater input of nitrate through sandy beaches

While most marine macrophytes preferentially assimilate ammonium to meet growth demand for nitrogen, some also utilize nitrate and exhibit high nitrate reductase activity (NRA). Although nitrate concentrations are often low in coastal waters during the summer and sandy beaches are generally considered to be low nutrient-input habitats, we have observed elevated NRA in leaves of some eelgrass (Zostera marina L.) plants growing immediately adjacent to the shoreline. We postulated that nitrate may become available to eelgrass and macroalgae via groundwater inputs that enter the nearshore water column. To address this possibility, we investigated the availability of groundwater nitrate for the induction of NRA in the leaves of eelgrass and in the macroalgaeSargassum filipendula C. Agardh (Phaeophyceae) andEnteromorpha intestinalis L. Link (Chlorophyceae) collected adjacent to two sandy beaches in the vicinity of Woods Hole, Massachusetts, USA. Induction of NRA was determined in the laboratory for eelgrass collected from one of the beach sites and from an offshore site, Lackey's Bay, which is isolated from groundwater input. At the two beach locations, pore water nitrate concentrations were 100 to 400µM within a few meters inland from the waterline. Nitrate efflux into the nearshore water column was quite high and variable (2160±660µmol m^–2 h^–1) when associated with rapid percolation (37±11 1 m^–2 h^–1) of nitrate-enriched pore water. Turbulent wave mixing rapidly diluted the nitrate. Macroalgae and eelgrass growing adjacent to a beach with high nitrate efflux had NR activities three- to sevenfold higher than those of algae and eelgrass growing along a beach section with low nitrate efflux. NRA of eelgrass plants from Lackey's Bay and Great Harbor increased in response to low daily nitrate additions (10 to 25µM) in the laboratory, with higher nitrate additions (50 to 200µM) yielding less dramatic responses. The increase in NRA was roughly three times higher for Great Harbor than for Lackey's Bay eelgrass. It appears that groundwater input of nitrate is sufficient to induce NRA in marine macrophytes growing near some beaches, including those with turbulent wave mixing.     

Geochemical occurrences of arsenic and fluoride in bedrock groundwater: a case study in Geumsan County,Korea

Bedrock groundwaters in Geumsan County, Korea, were surveyed to investigate the distribution and geochemical behaviors of arsenic and fluoride, mobilized through geogenic processes. The concentrations were enriched up to 113 μg/L for arsenic and 7.54 mg/L for fluoride, and 16% of 150 samples exceeded World Health Organization drinking water guidelines for each element. Simple Ca-HCO₃ groundwater types and positive correlations with pH, Ca, SO₄, and HCO₃ were characteristics of high (>10 μg/L) As groundwaters. The oxidation reaction of sulfide minerals in metasedimentary rocks and locally mineralized zones seems to be ultimately responsible for the existence of arsenic in groundwater. Desorption process under high pH conditions may also control the arsenic mobility in the study area. High (>1.5 mg/L) F groundwaters were found in the Na-HCO₃ type and with greater depth. Fluoride seemed to be enriched by deep groundwater interaction with granitic rocks, and continuous supply to shallow Ca-HCO₃-type groundwater kept the concentration high. In the study area, drinking water management should include periodic As and F monitoring in groundwater.

     

济南市地下水硝酸盐污染研究

调查了济南市东郊工业区浅层地下水、南部山区补给区地下水及市区饮用水中硝酸盐现状及发展趋势。结果表明，工业区浅层地下水硝酸盐含量超出国家饮用水卫生标准；补给区地下水及市区饮用水硝酸盐也受到人类活动的影响，污染呈逐年上升趋势。分析了造成地下水硝酸盐污染的原因，提出了相应的防治措施与对策。     

Ecological modelling of nitrate pollution in small river basins by spreadsheets and GIS

With the increasing importance and awareness of water quality in the small basins, the modelling system is developed for monitoring and predictions of surface water pollution. The compartment model deals with basin characteristics extended by land cover attributes. The parameters of the model are estimated by experimental data of water quality together with land cover types that serve as nutrient detention media or transformers. The study examines methodology to determine the potential areas of nitrate pollution from point and non-point sources by remote sensing techniques. Classification of water, agricultural, forest and urban areas is processed with satellite images (LANDSAT 7). Whereas the agricultural and urban areas act as sources of pollution, forest zones operate as sinks. The nitrate levels are decreased downstream, if the proportion of the forest inside contribution zones increases. The modelling system is used to simulate amounts of nitrates in each compartment of the stream during the monitored period of one year. The number of compartments and their lengths are estimated on the basis of morphology of the basin. Simulation of the dynamic model is carried out with the TabSim. Geographic information system (GIS) and remote sensing tools are used to manage and estimate nitrate inflows from point and non-point sources of pollution. The article presents the spatial and time variation of the nitrate (NO₃⁻) within the basin of the stream Rakovnický (the west part of Bohemia, the whole area of 368 km²). It is shown that the model approach extended by the GIS and remote sensing can support decision-making process for better management practices in the basins.     

Organic compounds in water extracts of coal: links to Balkan endemic nephropathy

The Pliocene lignite hypothesis is an environmental hypothesis that has been proposed to explain the etiology of Balkan endemic nephropathy (BEN). Aqueous leaching experiments were conducted on a variety of coal samples in order to simulate groundwater leaching of organic compounds, and to further test the role of the Pliocene lignite hypothesis in the etiology of BEN. Experiments were performed on lignite coal samples from endemic BEN areas in Romania and Serbia, and lignite and bituminous coals from nonendemic regions in Romania and the USA. Room temperature, hot water bath, and Soxhlet aqueous extraction experiments were conducted between 25 and 80 °C, and from 5 to 128 days in duration. A greater number of organic compounds and in higher concentrations were present in all three types of leaching experiments involving endemic area Pliocene lignite samples compared to all other coals examined. A BEN causing molecule or molecules may be among phenols, PAHs, benzenes, and/or lignin degradation compounds. The proposed transport pathway of the Pliocene lignite hypothesis for organic compound exposure from endemic area Pliocene lignite coals to well and spring drinking water, is likely. Aromatic compounds leached by groundwater from Pliocene lignite deposits in the vicinity of endemic BEN areas may play a role in the etiology of the disease. A better understanding of organic compounds leached by groundwater from Pliocene lignite deposits may potentially lead to the identification and implementation of effective strategies for the prevention of exposure to the causative agent(s) for BEN, and in turn, prevention of the disease.     

Integrating wetlands and riparian zones in river basin modelling

Wetlands, and in particular riparian wetlands, represent an interface between the catchment area and the aquatic environment. They control the exchange of water and related chemical fluxes from the upper catchment area to surface waters like streams and lakes. Their influence on water and nutrient balances has been investigated mainly at the patch scale. In this study an attempt was made (a) to integrate riparian zones and wetlands into eco-hydrological river basin modelling, and (b) to quantify the impacts of riparian wetland processes on water and nutrient fluxes in a meso-scale catchment located in the northeastern German lowland. The investigation was performed by analysing hydro-chemical field data and applying the eco-hydrological model SWIM (Soil and Water Integrated Model), which was extended to reproduce the relevant water and nutrient flows and retention processes at the catchment scale in general, and in riparian zones and wetlands in particular. The main extensions introduced in the model were: (1) implementation of daily groundwater table dynamics at the hydrotope level, (2) implementation of water and nutrient uptake by plants from groundwater in riparian zones and wetlands, and (3) assessment of nutrient retention in groundwater and interflow. The simulation results indicate that wetlands, though they represent relatively small parts of the total catchment area, may have a significant impact on the overall water and nutrient balances of the catchment. The uncertainty of the simulation results is considerably high, with the main sources of uncertainty being the model parameters representing the geo-hydrology and the input data for land use management.     

Merthyr Mawr: a case study for the assessment of nitrate at humid dunes in England and Wales

Humid dunes in the UK are at risk from nutrient pressures from multiple sources. The Water Framework Directive 2000/60/EC (WFD) requires assessment and identification of these pressures with appropriate measures defined to mitigate against further damage. We discuss the application of nitrate threshold values for the WFD classification, illustrating this with a case study at Merthyr Mawr, South Wales, where ephemeral groundwater discharge from a spring (‘Burrows Well’) sourced within the Carboniferous Limestone, creates a large dune slack. Ecological surveys suggest that the vegetation in this slack was in unfavourable condition, due to high levels of nitrate. Applying the source-pathway-receptor model an investigation was undertaken to improve the conceptual model and assess the significance of damage from groundwater derived nutrients. Results show groundwater nitrate concentrations?~?10 mg/l as NO₃-N feeding the main slack waters. The vegetation survey data shows clear evidence of ecological damage, and the hydrogeological data traces the source of this back to the Carboniferous Limestone aquifer and not the overlying blown sands. Discharging groundwater is the source of the enrichment. Isotopic analysis suggests that the N is derived from inorganic fertilizer and/or atmospheric N. During the first cycle WFD characterisation the unfavourable status of the dunes due to chemical groundwater pressure resulted in a failure of the surrounding groundwater body, which was designated as poor status. The site has been re assessed for the 2nd Cycle WFD characterisation where recently developed nitrate ‘threshold’ values have been applied to assess the significance of damage for groundwater derived nutrients. The surrounding Carboniferous Limestone catchment is complex and could not be sufficiently constrained, thus land management changes could not be targeted. The paucity of historical or repeat vegetation surveys limits our ability to measure change within the dune vegetation and causes difficulties in understanding the impact of multiple pressures.     

Nitrate levels and the age of groundwater from the Upper Devonian sandstone aquifer in Fife,Scotland

The tritium concentrations in 13 groundwater samples from boreholes throughout the Upper Devonian sandstone aquifer of Fife have been measured. Due to atmospheric variations in tritium concentrations over the last century, this radioactive tracer can be used as a groundwater age indicator. In this study, the groundwater tritium concentrations have allowed for the area to be divided into three zones, and the variable chemistry of the groundwater samples, including the problem of recent elevated nitrate levels in the Fife Aquifer, has been interpreted in terms of their relative ages.     

Simulation of groundwater age evolution during the Wisconsinian glaciation over the Canadian landscape

The simulation of groundwater age (residence time) is used to study the impact of the Wisconsinian glaciation on the Canadian continental groundwater flow system. Key processes related to coupled groundwater flow and glaciation modeling are included in the model such as density-dependent flow, hydromechanical loading, subglacial infiltration, glacial isostasy, and permafrost development. It is found that mean groundwater ages span over a large range in values, between zero and 42 Myr; exceedingly old groundwater is found at large depths where there is little groundwater flow because of low permeabilities and because of the presence of very dense brines. During the glacial cycle, old, deep groundwater below the ice sheet mixes with the young subglacial meltwater that infiltrates into the subsurface; the water displacement due to subglacial recharge reaches depths up to 3 km. The depth of penetration of the meltwater is, however, strongly dependent on the permeability of the subsurface rocks, the presence of dense brines and the presence or absence on deep fractures or conductive faults. At the end of the simulation period, it was found that the mean groundwater age in regions affected by the ice sheet advance and retreat is younger than it was at the last interglacial period. This is also true for frozen groundwater in the permafrost area and suggests that significant parts of this water is of glacial origin. Finally, the simulation of groundwater age offers an alternative and pragmatic framework to understand groundwater flow during the Pleistocene and for paleo-hydrogeological studies because it records the history of the groundwater flow paths.     

Geochemical provenance and spatial distribution of fluoride in groundwater of Mayo Tsanaga River Basin, Far North Region, Cameroon: implications for incidence of fluorosis and optimal consumption dose

The 500,000 inhabitants of Mayo Tsanaga River Basin are vulnerable to a “silent” fluorosis from groundwater consumption. For the first time, the groundwater is investigated for the purpose of identifying the provenance of fluoride and estimating an optimal dose of fluoride in the study area. Based on the fluoride content of groundwater, fluorine and major oxides abundances in rocks from the study area, mean annual atmospheric temperature, and on-site diagnosis of fluorosis in children, the following results and conclusions are obtained: Fluoride concentration in groundwater ranges from 0.19 to 15.2 mg/l. Samples with fluoride content of <1.5 mg/l show Ca–HCO₃ signatures, while those with fluoride >1.5 mg/l show a tendency towards Na-HCO₃ type. Fluor-apatite and micas in the granites were identified as the main provenance of fluoride in the groundwater through water-rock interactions in an alkaline medium. The optimal fluoride dose in drinking water of the study area should be 0.7 mg/l, and could be adjusted downward to a level of 0.6 mg/l due to the high consumption rate of groundwater, especially during drier periods.     

Identification and assessment of water pollution as a consequence of a leachate plume migration from a municipal landfill site (Tucumán,Argentina)

Landfills constitute potential sources of different pollutants that could generate human health and environmental problems. While some landfills currently work under the protection of a bottom liner with leachate collection, it was demonstrated that migration could take place even yet with these cautions. The purpose of this paper is to assess the pollution caused by a leachate plume from a municipal landfill that is affecting both groundwater and surface waters. The research was carried out at Pacará Pintado landfill in northwestern Argentina. Analysis of water samples indicates that leachate is affecting groundwater under the landfill area and an abandoned river channel hydraulically connected. In the center of the landfill area, the plume is anoxic and sulfate, nitrate, iron and manganese reduction zones were identified. Leachate plume presented high concentration of organic matter, Fe, Mn, NH₄ ⁺, Cl^? and Cr reaching an extension of 900 m. The presence of a leachate plume in a landfill site with a single liner system implies that the use of this groundwater pollution control method alone is not enough especially if permeable sediments are present below.     

Faecal and nitrate contamination in the groundwater of Mardan district,Pakistan

Environmental Geochemistry and Health - This study aimed to determine the status of groundwater contamination with faecal coliform and nitrate in the rural areas of Mardan district, Pakistan. Both...     

Geochemical occurrences of arsenic and fluoride in bedrock groundwater: a case study in Geumsan County, Korea

Bedrock groundwaters in Geumsan County, Korea, were surveyed to investigate the distribution and geochemical behaviors of arsenic and fluoride, mobilized through geogenic processes. The concentrations were enriched up to 113 μg/L for arsenic and 7.54 mg/L for fluoride, and 16% of 150 samples exceeded World Health Organization drinking water guidelines for each element. Simple Ca-HCO(3) groundwater types and positive correlations with pH, Ca, SO(4), and HCO(3) were characteristics of high (>10 μg/L) As groundwaters. The oxidation reaction of sulfide minerals in metasedimentary rocks and locally mineralized zones seems to be ultimately responsible for the existence of arsenic in groundwater. Desorption process under high pH conditions may also control the arsenic mobility in the study area. High (>1.5 mg/L) F groundwaters were found in the Na-HCO(3) type and with greater depth. Fluoride seemed to be enriched by deep groundwater interaction with granitic rocks, and continuous supply to shallow Ca-HCO(3)-type groundwater kept the concentration high. In the study area, drinking water management should include periodic As and F monitoring in groundwater.     

The effects of groundwater table and flood irrigation strategies on soil water and salt dynamics and reed water use in the Yellow River Delta, China

Vegetation management in shallow groundwater table environments requires an understanding of the interactions between the physical and biological factors that determine root-zone soil salinization and moisture. In this study, the effects of groundwater depth and flood irrigation strategies on water and salt dynamics and reed water use were analyzed in the shallow groundwater region of the Yellow River Delta in China using the HYDRUS-1D model. The results indicated that there is a conflict between water, salt stress, and reed water use with variations in groundwater depth. A water table depth of 3.5 m is the minimum limit to maintain a safe level of soil salinity, but at this depth, the environmental stress on reeds is worsened by the decrease in soil water storage. Maintaining the flood pulses on the wetland, especially during May, may be critical for restoring the reed wetland in the Yellow River Delta.     

再生水回灌地下水环境安全风险评价技术方法研究

再生水回灌是水资源管理的一条有效途径,也是污水再生利用的重要发展方向。然而,当再生水以农灌、土壤含水层处理（SAT）、河湖入渗和井灌等方式进行地下水回灌时,不可避免的会在回补地下水的过程中造成对地下水环境的污染风险。针对不同回灌方式建立适用于我国的再生水回灌地下水环境安全风险评价技术体系至关重要。借鉴国内外地下水污染风险评价方法,综合分析再生水回灌对地下水产生风险的关键环节,采用层析分析法,从回灌水特征污染物特性、回灌区地下水固有脆弱性以及回灌工程布设方式3个方面,针对地表灌溉、河湖入渗和井灌3种回灌方式,建立了包含污染物浓度水平、分配系数、溶解度、半衰期、半致死剂量、地下水埋深、降雨入渗补给量、地形坡度、土壤介质、包气带介质、含水层介质、含水层厚度、回灌强度、回灌周期、回灌水停留时间以及取水点与回灌点水平距离16个指标在内的风险评价指标体系。在此基础上,结合地下水使用功能,以20个典型再生水回灌场地调研结果和160种再生水回灌地下水污染风险因子物化特性为数据基础,对各指标进行了风险水平的划分,基于聚类分析法,采用各指标风险指数相乘的风险表征方法计算总风险指数,构建了再生水回灌地下水环境安全风险评价技术方法。该方法有效的避免了指标权重计算的主观性,并且能够直观的找出导致风险的主要因素。结果表明：利用建立的风险评价技术方法可将我国再生水回灌地下水环境安全风险划分为3级,风险值〈5为一级,风险值在5-15之间为二级,风险值〉15为三级。在某再生水回灌场地的应用表明,该回灌区地下水环境安全风险为二级,同时得出回灌水特征污染物特性指标是造成该回灌区地下水环境风险的主要因素。