Occurrence of acidic groundwater in precambrian crystalline bedrock aquifers,Southwestern Sweden

The pH and alkalinity of groundwater from 7651 wells drilled in the Precambrian crystalline bedrock of southwestern Sweden has been evaluated. The wells are generally less than 100 m deep. Analytical results were collected from different laboratories and authorities in the region. In areas with thin soil cover or coarse-grained deposits overlying the bedrock, alkalinity is normally less than 100 mg HCO₃ L^?1. Below the marine limit, where clayey sediments predominate, alkalinity sometimes even exceeds 200 mg HCO₃ L^?1. When comparing pH and alkalinity of groundwaters from Quaternary deposits with bedrock groundwaters, the latter always have higher pH and alkalinity values. The most acidic bedrock groundwaters are found in small areas close to the city of Göteborg due to additional factors of high acid loadings, high groundwater discharge and thin soil layers. A study of data from 1949 to 1985 in the province of Värmland suggests that no regional acidification of importance is in progress. However, results from public water supplies support the hypothesis that the groundwaters which are most sensitive to acidification are those where discharge from wells in small bedrock aquifers induces rapid groundwater recharge of acidic surficial water.     

Regional groundwater monitoring and examples of acidification trends in the province of Göteborg and Bohus,southwestern Sweden

Acidification is the most serious threat to the groundwater quality in the province, causing both corrosion on water pipe systems and increased leaching of metals from the ground. The regional groundwater monitoring programme focuses on parameters as pH, alkalinity, sulphate and total aluminium. Sampling is done regularly in 1) natural groundwater springs in the countryside, 2) public water supplies, 3) observation wells in the countryside and 4) observation wells in urban areas.For most of the sites, analysing has been carried out during a time period that is shorter than five years. These sites give valuable information about the general relationship between groundwater acidity and the hydrogeological conditions in the recharge area. Results from regular sampling of public water supplies have been used for studies of time series. The trends indicate that the hydrogeological conditions are of great importance for how the groundwater responds to acid input. In general, surficial groundwater in Quaternary deposits is more sensitive to acidification than groundwater in crystalline bedrock.     

标准化地下水指数法分析黑河中游地下水时空演变规律

地下水干旱威胁区域社会经济发展和生态环境健康。基于河西走廊黑河流域中游地区1985—2010年23眼井的月地下水位数据,选择4种不同的分布函数构建标准化地下水指数(standardized groundwater index,SGI),采用K-S检验(kolmogorov-smirnov test)和AIC准则(Akaike information criterion)进行分布函数的优选,对K-S检验未通过的井使用非参数法构建SGI,分析地下水时空演变规律。结果表明:1)不同拟合函数对参数化SGI拟合结果有强烈影响。2)研究区的最佳拟合函数为Beta分布(18眼井),其次为广义极值分布(3眼井),另有2眼井未通过K-S检验,使用非参数法构建SGI。3)张掖区SGI指数变化趋势总体上呈先下降后回升趋势(13眼井),临泽和高台区呈持续下降趋势(10眼井)。地下水指数的构建可为地下水资源的监测、管理及预报提供依据。     

Bacterial pollution of groundwater: A review

Contamination of groundwater resources from bacterial laden wastewater and effluents poses a great threat to the potability and use of these water sources. Future planning, development and management schemes must consider this topic to avoid costly and sometimes untested corrective actions. Major factors affecting the quantity and velocity at which bacteria are able to migrate through soil can be classified as (1) soil factors including particle size distribution, structure, clay content, pore size distribution and moisture regime, and (2) biological factors responsible for bacterial die-off including pH, temperature, moisture content, and nutrient supply. Past bacterial pollution problems have been shown to be localized and restricted to wells utilizing near-surface waters. The following problem areas exist and must be given special consideration in planning and development: (1) use of septic disposal systems in unsuitable soils; (2) drainage waters from wastewater application areas utilizing artificial drainage systems; (3) waste application in areas underlain by fractured crystalline rock or channelized bedrock; and (4) bacterial contamination induced over great distances by groundwater pumping.     

The environmental impacts of humans on groundwater in Lebanon

The execution of most large water projects in Lebanon has been continuously postponed, due to political reasons for the period preceding 1975 and to the civil war after that date. The accumulated impacts of mismanagement and shortage in water supplies forced population to drill their private wells and extract groundwater to meet their increasing needs. This uncontrolled action has significantly deteriorated the quality of groundwater, reflected in the increasing salinity of extracted water from coastal aquifers, and in the contamination of many wells and springs by improperly disposed waste water. The overexploitation of the aquifers has led to considerable decline in the discharge of springs and rivers amounting 18.8% between the 1960's and early 80's, irrespective of rainfall fluctuations. This study shows that the water budget in early 1980's has decreased appreciably, relative to 1960's budget. In Mount Lebanon basin the amount of precipitation dropped from 2700 to 2214 m³ yr^?1, the rivers, discharge declined from 1320 to 834 Mm³ yr^?1, and the recharge to groundwater decreased from 733 to 601 Mm³ yr^?1.     

密云水库流域地下水硝态氮的分布及其影响因素

2008年11月至12月,采集了密云水库流域305个井的地下水样品,分析了其硝态氮含量。结果表明,密云水库流域地下水的硝态氮含量的平均值、超标率(10 mg L-1≤NO3--N<20 mg L-1)和严重超标率(NO3--N≥20 mg L-1)分别为6.81 mg L-1、13.77%和2.30%。其中村庄和菜地的地下水硝酸盐污染最为严重,35个村庄井和13个菜地井的地下水硝态氮含量的平均值分别为9.52 mg L-1和9.55 mg L-1,已接近WHO饮用水硝态氮含量10 mg L-1的限定标准,超标率分别为20%和15.38%,严重超标率分别为8.57%和7.69%。219个粮田井水的硝态氮水平位居中间,其硝态氮含量的平均值、超标率和严重超标率分别为6.59mg L-1、14.61%和1.37%。10个林地井的地下水硝态氮含量是最低的,其平均值为2.66 mg L-1,无超标现象。潮河流域农田地下水的硝酸盐污染比白河流域严重。潮河流域农田(124个井)的地下水硝态氮含量的平均值、超标率和严重超标率分别为8.42 mg L-1、21.77%和3.23%,而白河流域(122个井)则分别为5.03mg L-1、6.56%和0,即无严重超标现象。密云水库流域农田地下水的硝态氮含量呈现出上游低而下游高的趋势。玉米田地下水硝态氮含量在接近河道的地方有所降低,与地下水水位呈负相关,与化肥氮的施用量呈正相关,当地下水位小于7m时或当一年的化肥氮的施用量超过200 kg hm-2,存在地下水硝态氮含量超标的潜在危险。     

Longtime effects of deep groundwater extraction management on water table levels in surface aquifers

Purpose

A longtime monitoring (2003–2013) of groundwater levels and soil moisture was done in a plain tract surrounded by deposits from the Saale glacial stage in northern Germany. The purpose was to document the changes in the soil water regime over time in relation to changes in management of groundwater extraction and to evaluate if the hitherto management has been suitable for plant water supply for the local grassland production.

Materials and methods

Groundwater wells in the surface aquifer were monitored at 11 survey sites, and soil matric potentials were measured with tensiometers at five depths per site. Soil analyses also were done. This report contains the results from three of the 11 survey sites, which best represent the variability of the soils in the area.

Results and discussion

The monitoring showed that groundwater extraction from deep aquifers via individual wells altered the groundwater levels in the surface aquifer, even though there was a distance of several meters depth and a geological parting between the two aquifers. The impact of the groundwater extraction was shown by significant correlations between groundwater levels in the surveyed soils and groundwater extraction rates of individual wells. Climatic factors only affected groundwater levels in individual years. The management of the groundwater extraction from 1977 to 2006 severely lowered the groundwater level in the surface aquifer. Due to a limitation of the groundwater extraction rates and a shift in the degree of capacity utilization of the individual wells from 2006 onward, groundwater levels in the area are recovering. Correspondingly, the contribution of capillary rise to plant water supply has increased within the monitoring period.

Conclusions

The monitoring proves that the present management of groundwater extraction is more suitable for the groundwater situation than past management. However, groundwater levels have not yet obtained a new equilibrium, so continual monitoring is needed.

     

Assessment of Deep Groundwater Quality in Kathmandu Valley Using Multivariate Statistical Techniques

This study was carried out to assess the overall water quality and identify major variables affecting the deep groundwater quality in Kathmandu Valley, Nepal. Forty-two deep wells were sampled during premonsoon and monsoon seasons in 2007 and analyzed for the major physicochemical variables. The water quality variables such as NH ₄ ⁺ -N, Fe, Pb, As, and Cd at most of the sampling locations exceeded the World Health Organization guideline levels for drinking water. Multivariate statistical techniques such as factor analysis and cluster analysis were applied to identify the major factors (variables) corresponding to the different source of variation in deep groundwater quality. Factor analysis indentified six major factors explaining 74.77% of the total variance in water quality; and the major variations are related with the degree of groundwater mineralization, decomposition of organic matter, and reduction of groundwater environment. The water quality of deep groundwater is influenced by the natural hydrogeochemical environment. The wells are broadly divided into two major groups based on the similar groundwater characteristics using cluster analysis. Results show that water quality of deep groundwater does not vary significantly as a function of season.     

复合井修复地下水硝酸盐污染的效果

为探寻更适用于农田周边硝酸盐污染地下水的原位生物修复技术,该研究构建了A、B、C3套试验装置,分别刻画管井（A）、大口井与管井组成的复合井（B、C）。基于3套物理试验模型,定量对比分析了管井与复合井修复地下水硝酸盐污染的效果。结果表明：受水力停留时间的影响,相同流速条件下,A、B、C三套修复系统的硝酸盐负荷分别介于75～100、100～125、125～150 mg/L之间;在允许硝酸盐负荷范围内,去除率均可达到95%以上,且不会出现亚硝酸盐累积及氨氮超标现象,表明了复合井修复系统的可行性,可以实现地下水开采与修复同步进行,提高了地下水水源地供水安全保证率。     

Evaluation of the Influence of Natural and Antrhopogenic Processes on Water Quality in Karstic Region

This paper presents a comprehensive study on the quality of surface and groundwater in an environmentally sensitive karstic watershed strongly pressed by urban growth. The objective of the study was to assess the integrated effects of human activities and natural characteristics of karstic environments on the quality of surface and groundwater using multivariate statistical techniques. Data from 18 physical, chemical, and microbiological water quality variables obtained throughout a hydrological year were analyzed using principal components analysis (PCA) and cluster analysis. The PCA was carried out individually for surface water and groundwater. Our goal was to study the behavior of the water quality variables at each of these systems, as well as to infer the importance of these variables on the dynamics of the water resources in the region. Our results for surface water showed that the 18 original variables could be reduced to five principal components which together accounted for 69% of the total variation in the data, whereas for groundwater, 70% of the total variation in the data was explained by five principal components. In order to evaluate the impacts of anthropic activities on the water quality at the monitoring locations, the cluster analysis was applied to the ten sampling points. The analysis identified five clusters, two of which are formed by points with low contamination levels and three where the anthropic interference is noticeable. The results suggest the existence of specific contamination sources in many points, including in the groundwater, and highlight the natural vulnerability of the karstic environments.     

Impact of sanitary landfill on groundwater quality

This paper presents the results of monitoring the shallow groundwater quality around two municipal landfill sites in the Eastern Province of Saudi Arabia. Boreholes were installed at Dhahran and Juaymah sites upstream and downstream of the landfill. Twenty water samples were collected from each borehole and analyzed for various parameters mainly for BOD, COD, TOC, NH₃-N, TKN, sulphate, chloride, hardness and metals. The result of the analysis of water samples from Dhahran boreholes shows an increase in the concentration of pollutants in downstream groundwater over that observed in upstream boreholes. The average concentration of BOD₅, COD and TOC in the samples obtained from the downstream borehole was found to be 6.5, 23.5, and 34.3 mg L^?1, respectively. On the other hand, the mean concentration of the same parameters in upstream monitoring wells was found to be less than 2.4, 11.5, and 10.0 mg L^?1, respectively. The ammonia-N and organic-N in the downstream wells were 0.37 and 0.29 mg L^?1, respectively, whereas, in upstream wells they were 0.11 and 0.15 mg L^?1, respectively. At Juaymah, the average concentration of BOD and TOC in groundwater samples obtained from upstream boreholes were less than 3.0 and 7.2 mg L^?1, respectively, while the concentration of the same parameters in downstream well samples were above 5.0 and 35.0 mg L^?1, respectively. A similar trend of increment of ammonia-N, organic-N, phosphate, sulfate and metals in downstream samples was observed. Since the water from these shallow aquifers at both places is not being used for human consumptions or for any other commercial purpose, therefore, the minor increase in pollutants concentration at downstream level is not of a great concern.     

基于BP神经网络的北京昌平山前平原地下水水质评价

该文采用单因子评价方法对昌平区浅层地下水的超标因子进行筛选,结合水文地球化学理论探讨各因子超标原因,分析浅层地下水水质的空间分布特征,并采用BP神经网络法对水质进行综合评级。从综合评级结果来看,12眼监测井中1眼为Ⅴ类水质,5眼为Ⅳ类水质,6眼为Ⅲ类水质。单因子筛选结果表明,总硬度、总溶解性固体、氮素、氟化物等为该区最主要的超标因子。经分析可知,山前平原地带浅层地下水中氟化物为原生污染,氮素污染物主要来源于地表污染物下渗,总硬度和总溶解性固体的升高主要受地表污染物下渗、氮素的迁移转化等因素的影响。研究可为研究区地下水管理工作提供可靠数据。     

Effects of tree identity dominate over tree diversity on the soil microbial community structure

This study investigated the possible effects of tree species diversity and identity on the soil microbial community in a species-rich temperate broad-leaved forest. For the first time, we separated the effects of tree identity and tree species diversity on the link between above and belowground communities in a near-natural forest. We established 100 tree clusters consisting of each three tree individuals represented by beech (Fagus sylvatica L.), ash (Fraxinus excelsior L.), hornbeam (Carpinus betulus L.), maple (Acer pseudoplatanus L.), or lime (Tilia spec.) at two different sites in the Hainich National Park (Thuringia, Germany). The tree clusters included one, two or three species forming a diversity gradient. We investigated the microbial community structure, using phospholipid fatty acid (PLFA) profiles, in mineral soil samples (0–10 cm) collected in the centre of each cluster.The lowest total PLFA amounts were found in the pure beech clusters (79.0 ± 23.5 nmol g⁻¹ soil dw), the highest PLFA amounts existed in the pure ash clusters (287.3 ± 211.3 nmol g⁻¹ soil dw). Using principle components analyses (PCA) and redundancy analyses (RDA), we found only for the variables ‘relative proportion of beech trees’ and ‘living lime fine root tips associated with ectomycorrhiza’ a significant effect on the PLFA composition. The microbial community structure was mainly determined by abiotic environmental parameters such as soil pH or clay content. The different species richness levels in the clusters did not significantly differ in their total PLFA amounts and their PLFA composition. We observed a tendency that the PLFA profiles of the microbial communities in more tree species-rich clusters were less influenced by individual PLFAs (more homogenous) than those from species-poor clusters.We concluded that tree species identity and site conditions were more important factors determining the soil microbial community structure than tree species diversity per se.     

农户稀缺感知、超采认知对地下水灌溉用水效率的影响——基于河北地下水超采区457个农户调研数据

华北地区由地下水超采造成的环境问题日益严重,农业作为主要用水部门,亟须提高灌溉用水效率,减少水资源浪费。本文基于2019年对河北地区457户使用地下水进行灌溉的农户调查数据,采用随机前沿模型对灌溉用水效率进行测算,进一步在参照相关研究基础上重新构建农户水资源稀缺性感知和地下水超采认知测度的指标体系,在控制个人和家庭特征、生产特征基础上,实证分析农户稀缺感知和超采认知对灌溉用水效率的影响。研究结果显示:农户平均灌溉用水效率值为0.59,主要分布区间为0.40～0.80,具有较大提升空间;稀缺感知中水量感知、水位感知和稀缺预期对农户用水效率具有显著正向影响,超采认知中地下水超采危害认知和压采环保认知对用水效率提升具有促进作用;务农年限和受教育程度同用水效率正相关,相较于自有土地,流转土地具有更高的用水效率,耕地细碎化和灌溉设施距离过远则显著降低用水效率。因此,大力提升农户相关认知水平、推进土地流转和完善设施建设等措施将有助于提高河北地区灌溉用水效率。     

再生水灌区地下水硝态氮空间变异性及污染成因分析

为了深入了解北京市再生水灌区地下水硝态氮空间分布规律及污染成因,该文基于地统计学理论、结合ArcGIS软件的地统计分析功能,绘制表达了该区域地下水硝态氮随机性和结构性的半变异函数图和空间分布图。结果表明,研究区域地下水硝态氮含量服从对数正态分布,且与1阶高斯克里格模型拟合最好,从获得的参数可知,地下水硝态氮的空间变程为9639.36m,为反应灌区硝态氮的分布特征,2个监测点的距离不应大于变程;其块金效应为0.43,表明地下水中的硝态氮含量的变化是结构性因素与人为因素共同作用的结果,同时还发现土地利用类型、地下水的开采强度与区域地下水是否容易遭受硝态氮的污染有很大的相关性,监测井深度越小、地下水位降幅越大,地下水硝态氮增幅越大,再生水蓄积区(坑塘水面)对应区域产生地下水硝态氮污染的风险较小。研究结果可为再生水的安全利用提供参考。     

The dynamics of N2O near the groundwater table and the transfer of N2O into the unsaturated zone: A case study from a sandy aquifer in Germany

The research area was the Fuhrberger Feld aquifer (FFA) in northern Germany. It is situated about 30km northeast of the city of Hannover and covers about 300km². Six multilevel sampling wells along a representative strip under predominantly arable land along a groundwater flow-line were sampled from the groundwater table down to a depth of 10m below the soil surface. We measured N₂O, CO₂, NO₃⁻, SO₄²⁻, DOC, pH, redox potentials and O₂ concentrations.N₂O accumulated at four out of six wells close to the groundwater table. About 20% of N₂O that occurred between the groundwater table and 7–8m below it resided in the top 0.4m. An exchange zone for N₂O at the interface between the saturated and the unsaturated zone extended 0.55 ± 0.22m below the groundwater table and acted as a source and sink for N₂O. N₂O below the exchange zone cannot be transferred from the groundwater to the atmosphere. The upward fluxes from the exchange zone into the unsaturated zone at the six wells ranged between 0.0009 and 0.3kg N₂O ha^{− 1} year^{− 1}. The yearly downward fluxes into the exchange zones had about the same order of magnitude as the upward fluxes. The upward and downward fluxes of N₂O at the (fluctuating) water table did cancel out each other, but this does not yet imply, that the N₂O fluxes at the soil surface also cancel out each other.N₂O–N:NO₃–N ratios were highly variable ranging from 0.0002 to 0.0417.A multiple regression for the monthly N₂O amounts in the exchange zone could explain 66% of the yearly variation. The significant variables were NO₃⁻, CO₂, pH, and O₂. Therefore, a combination of the land use (NO₃⁻), the geochemical boundary conditions (pH) and the type of denitrification reaction (O₂ and CO₂ indicate the importance of a heterotrophic denitrification process) governed the N₂O dynamics in the surface groundwater of the FFA and its transfer into the unsaturated zone.     

陕西省乾县地下水位动态变化特征分析

依据渭北高塬与关中平原过渡地带的陕西省乾县近16 a地下水位埋深监测资料,结合研究区数字高程模型(DEM)反映的地貌和水系分布状况,选取7口地下水位监测井,对乾县城区、羊毛湾灌区和宝鸡峡灌区地下水位年际和年内动态变化特征进行了分析。结果表明,乾县城区近10 a地下水位以0.31 m/a的速度上升;羊毛湾灌区和宝鸡峡灌区近16 a地下水位均呈下降趋势,并且前者下降幅度大于后者;降水量偏多使得水库水位高于其附近地下水位,距离水库近的地区,地下水位受水库补给和降雨入渗补给双重作用迅速上升;距离水库远的地方,地下水位主要受降雨入渗补给,地下水位上升具有滞后性。灌区地下水位具有在2月和10月左右达到高水位,7月降至低水位的特征。实施节水和井渠结合灌溉是保证乾县地下水资源可持续利用的有效途径。     

Selection of Tolerant Plants and Their Arrangement to Restore a Forest Ecosystem Damaged by Air Pollution

Wastewater and groundwater has been used for irrigation in the Valsequillo District, east central Mexico, for nearly 50 years. The environmental impact of wastewater on groundwater in the unconfined shallow aquifer is evaluated by means of hydrogeological, microbiological, hydrogeochemical and isotopic evidences. The shallow aquifer consists of upper Tertiary volcano-sedimentary rocks with a calcite-rich matrix. Groundwater from wells near the wastewater canal had similar total coliforms concentrations as the wastewater (～100 MPN 100 mL^-1). The hydraulic head in near-canal wells had a recovery of 10 m until 1983, indicating shallow recharge from wastewater. A bicarbonate vs. calcium plot shows a well-defined mixing process between wastewater and unaffected groundwater. Stable isotopic data (δD and δ¹⁸O) show characteristic signatures for wastewater and non-impacted groundwater, and define a mixing line between those end-members and groundwater affected by wastewater infiltration. Tritium data indicate that non-impacted groundwater is ‘pre-atomic hydrogen bomb’ (>50 yr), whereas the wastewater has a ‘younger’ signature. Tritium data from wells inside the district clearly indicate a mixing process between waste and groundwater. These results demonstrate the interaction and hydrochemical processes between wastewater and shallow groundwater at the site.     

基于指示Kriging法的土壤盐渍化与地下水埋深关系研究

在北方干旱、半干旱的地下水浅埋区,土壤盐渍化是土地资源退化的主要原因,防治土壤盐渍化是农业和生态环境可持续发展的重要保障。该文以内蒙古河套灌区解放闸灌域为例,运用指示Kriging法绘制并比较了不同阈值下地下水位埋深和土壤表层含盐量的概率分布图,从概率空间分布的角度分析研究了土壤盐渍化与地下水位埋深之间的关系,从而将这方面的研究从通常的农田尺度扩大到灌域尺度。结果表明:1)土壤盐分和地下水位埋深空间变异强度均为中等,且具有中等的空间自相关性,球状模型拟合变异函数的效果较好;2)在灌域尺度上,解放闸灌域4月底土壤表层发生中度、轻度盐渍化时地下水位临界埋深分别为2.0、2.5m,西南及中东部地下水位埋深小于临界埋深的概率较大,是土壤返盐的高风险区;3)3月底地下水位埋深对土壤返盐的影响比4月底更大一些,这表明地下水位埋深对土壤返盐的影响具有一定滞后效应,只有地下水位埋深小于临界深度的状态维持一段时间,才会造成土壤中度或轻度盐渍化。