Groundwater recharge and agricultural contamination

Agriculture has had direct and indirect effects on the rates and compositions of groundwater recharge and aquifer biogeochemistry. Direct effects include dissolution and transport of excess quantities of fertilizers and associated materials and hydrologic alterations related to irrigation and drainage. Some indirect effects include changes in water–rock reactions in soils and aquifers caused by increased concentrations of dissolved oxidants, protons, and major ions. Agricultural activities have directly or indirectly affected the concentrations of a large number of inorganic chemicals in groundwater, for example NO₃ ^–, N₂, Cl, SO₄ ^2–, H⁺, P, C, K, Mg, Ca, Sr, Ba, Ra, and As, as well as a wide variety of pesticides and other organic compounds. For reactive contaminants like NO₃ ^–, a combination of chemical, isotopic, and environmental-tracer analytical approaches might be required to resolve changing inputs from subsequent alterations as causes of concentration gradients in groundwater. Groundwater records derived from multi-component hydrostratigraphic data can be used to quantify recharge rates and residence times of water and dissolved contaminants, document past variations in recharging contaminant loads, and identify natural contaminant-remediation processes. These data indicate that many of the world's surficial aquifers contain transient records of changing agricultural contamination from the last half of the 20th century. The transient agricultural groundwater signal has important implications for long-term trends and spatial heterogeneity in discharge. Electronic Publication     

陕西省泾惠渠灌区地下水污染与人体健康风险评价

通常井内的地下水流速是由单井示踪试验或Aqua Vision流速流向仪测定得来,用以计算含水层中的地下水流速。由于表皮结构的影响,导致井筒附近的地下水流场发生变化,引起井筒内的流速与含水层中的流速存在偏差。为了探究表皮效应对井筒内地下水流速的影响,利用COMSOL Multiphysics软件,建立考虑表皮效应的地下水流数值模型,系统分析表皮厚度以及渗透系数对井筒中地下水流速的影响机制,根据模拟结果进一步评估利用井筒内地下水流速换算含水层地下水达西流速已有经验公式的可靠性。结果表明：(1)井筒附近表皮区域渗透系数越大,井筒内的地下水流速越大,且利用经验公式计算的地下水达西流速相对误差均小于0.23%,具有较高可靠性;(2)表皮区域渗透系数小于含水层渗透系数时,随着表皮厚度增大,井筒内地下水流速越小,经验公式计算结果的相对误差呈现增大趋势;(3)表皮区域渗透系数大于含水层渗透系数时,随着表皮厚度增大,井筒内地下水流速增大,计算结果相对误差总体上呈现减小的趋势,但其误差波动性较大,表明在该条件下经验公式计算的稳定性较差。结果显示表皮结构对井筒内地下水流速影响较大,在实际应用中要关注表皮结构的影响。

     

地下水污染脆弱性评价方法

地下水污染脆弱性是指污染物自顶部含水层以上某一位置到达地下水系统中某一特定位置的趋势和可能性,进一步分为固有脆弱性和特殊脆弱性.地下水污染脆弱性受地下水流系统和地球化学系统的影响和控制.其主要评价方法有主观分级评价法、统计或基于过程的评价法和综合评价法三大类.中国地下水污染脆弱性评价已有很好的工作基础,评价工作中应以地下水系统为单元,以饮用水井、集中供水水源地、区域含水层系统的补给区为重点保护目标,评价方法应综合区域地下水流系统的过程分析和指数评价方法,并利用已有的区域水质资料进行检验,增强评价结论的科学性和可靠性.     

Groundwater contamination: risk management and assessment for landfills in Mar del Plata, Argentina

 This study presents a program for risk management in the contamination of groundwater resulting from leachate in landfills at Mar del Plata (Argentina). The program includes prediction, prevention, monitory observation and mitigation as actions that must be taken prior to, during, and after contamination occurs. This routine aids in the identification of weak points and failures of the program for those who are in charge of making decisions, and will allow better use of limited financial and technical resources based on planning, thus minimizing disconnected determinations. Results of the prediction stage were confirmed through monitoring. The presence of a plume of contamination more than 100 m from the landfill was shown, thus proving that implementation of a monitoring plan to follow the development of the contaminated plume must be implemented, particularly in populated areas which depend on residential wells for their water supply. Received: 8 May 2000 · Accepted: 14 August 2000     

地下水污染脆弱性评价方法

地下水污染脆弱性是指污染物自顶部含水层以上某一位置到达地下水系统中某一特定位置的趋势和可能性,进一步分为固有脆弱性和特殊脆弱性。地下水污染脆弱性受地下水流系统和地球化学系统的影响和控制。其主要评价方法有主观分级评价法、统计或基于过程的评价法和综合评价法三大类。中国地下水污染脆弱性评价已有很好的工作基础,评价工作中应以地下水系统为单元,以饮用水井、集中供水水源地、区域含水层系统的补给区为重点保护目标,评价方法应综合区域地下水流系统的过程分析和指数评价方法,并利用已有的区域水质资料进行检验,增强评价结论的科学性和可靠性。     

Groundwater resources assessment for irrigable agricultural lands in the Wadi Araba area, southern Jordan

The main target of this research paper was to the hydrogeological assessment of the groundwater resources to irrigate 600 ha of irrigable agricultural lands, distributed along the Dead Sea–Aqaba Highway in Umm, Methla, Wadi Musa, Qa’ Saideen and Rahma, southern Jordan. Therefore, a comprehensive groundwater study was commenced by drilling eight new wells which can be used to supply irrigable areas with the existing groundwater that would be enriched by the yield of three proposed recharge dams on Wadi Musa, Wadi Abu-Burqa, and Wadi Rahma. The evaluation of the pumping test data of the drilled was carried out using the standard methods of pumping test interpretation. This was based on the available water table measurements at well locations and knowledge of water flow in the general. The sustainable yield of each well was calculated based on the pumping test parameters. The obtained results indicate that pumping out of Beer Mathkor wells should not exceed 1,100 m³/day in the case of continuous pumping and 8,700 m³/day in the case of intermittent pumping. Since the water table did not significantly change with small changes in pumping (it took eightfolds of magnitude increase in pumping from approximately 1,100 to 8,700 m³/day to show a significant drop in the water table equivalent to about 5.5 MCM per year from the aquifer.     

Geoelectric resistivity sounding of riverside alluvial aquifer in an agricultural area at Buyeo,Geum River watershed,Korea: an application to groundwater contamination study

Twenty profiles of vertical electric soundings (VES) were obtained in a riverside alluvium at the Buyeo area, South Korea, to examine the variations of subsurface geology and associated groundwater chemistry. The combination of the VES data with the borehole data provided useful information on subsurface hydrogeologic conditions. The vestige of an ancient river channel (e.g. oxbow lake) was identified on the resistivity profiles by the lateral continuation of a near-surface perched aquifer parallel to the river. Such a perched aquifer is typically developed in the area with a clay-rich silty surface alluvium which prohibits the infiltration of oxygen. Therefore, groundwater below the oxbow lake shows a very low nitrate concentration and Eh values under the strong anoxic condition. The distribution of water resistivity is correlated with that of measured total dissolved solids concentration in groundwater, while the earth resistivity of the aquifer shows a significant spatial variation. It is interpreted that the earth resistivity of the aquifer is mainly controlled by the soil type rather than by the water chemistry in the study area.     

Groundwater nitrate pollution in an alluvium aquifer, Eskişehir urban area and its vicinity, Turkey

 A large amount of the water requirement (municipal, industrial, etc.) of Eskişehir city, Turkey, is supplied from groundwater via wells in the urban area. The groundwater in the Eskişehir Plain alluvium has been polluted by municipal and industrial wastewater, and agricultural activities. The nitrate concentrations at nine sampling points on Porsuk River, the main water course in the plain, ranged from 1.5 to 63.3 mg/l during the period from July 1986 to August 1988. In the same period, the nitrate concentrations measured in water from 51 wells ranged between 2.2–257.0 mg/l. The nitrate content of the groundwater samples was 34.2% above 45 mg/l, the upper limit for nitrate in drinking water standards. High nitrate levels were observed in water from wells in the central and eastern parts of the urban area. The nitrate content of the well water is subject to seasonal fluctuation. In general, low nitrate concentrations were observed in wet seasons, and high ones in dry seasons. Received: 16 April 1996 · Accepted: 2 October 1996     

Distribution of nitrate in groundwater affected by the presence of an aquitard at an agricultural area in Chiba, Japan

Geological and geographical parameters including land use, stratigraphic structure, groundwater quality, and N- and O-isotopic compositions of nitrate in groundwater were investigated to elucidate the mechanism of groundwater pollution by NO₃ ^? in the agricultural area of Katori, Chiba, Japan. An aquitard distributed in the western part of the study area has produced two unconfined aquifers. The average concentrations of NO₃ ^? and dissolved oxygen (DO) were high in the aquifer above the aquitard (7.5 and 7.6 mg/L, respectively) and in the aquifer of the eastern part of the study area that was not influenced by the aquitard (11.9 and 7.8 mg/L, respectively); however, the levels in the aquifer under the aquitard were relatively low (2.2 and 3.7 mg/L, respectively). The δ¹⁵N and δ¹⁸O values of NO₃ ^? generally increased exponentially in the groundwater that flowed into the aquifer under the aquitard as the concentration of NO₃ ^? decreased, although this decrease in NO₃ ^? also occasionally occurred without isotopic changes. These results indicated that the aquitard prevented the penetration of NO₃ ^?, DO, and gaseous O₂. Under the aquitard, denitrification and dilution with unpolluted water that entered from natural forested areas reduced the NO₃ ^? concentrations in the groundwater. The major sources of NO₃ ^? in groundwater in the study area were estimated to be NH₄-chemical fertilizer, livestock waste, and manure.     

Groundwater vulnerability and contamination risk assessment of the Weining Plain,using a modified DRASTIC model and quantized pollution loading method

Groundwater resources have become more vulnerable to contamination due to rapid population growth and economic development. This study aimed to assess the groundwater contamination risk in the Weining Plain, China. Based on the specific conditions of the Weining Plain, a new model DRTSWI with a weighting scheme determined by analytic hierarchy process was developed to evaluate the intrinsic groundwater vulnerability for the study area. An integrated approach, combining the toxicity, the release possibility, and the potential release quantity of the pollutants, was used to estimate the pollution loading. The groundwater contamination risk results were obtained by overlaying the intrinsic vulnerability and pollution loading maps. These indicated that two industrial parks pose the main threat to groundwater quality, due to their unfavorable hydrogeological setting and potential pollution sources on the surface. Some areas in and around the industrial parks exhibit groundwater pollution, which was identified on the contamination risk map using buffer analysis. High risk areas are industries with high or medium vulnerability. The vulnerability and contamination risk maps developed for this study are valuable tools for environmental planning and can be used for predictive management of groundwater resources.     

Evaluation of an intrinsic and a specific vulnerability assessment method in comparison with groundwater salinisation and nitrate contamination levels in two agricultural regions in the south of Portugal

The applicability of two vulnerability assessment methods in evaluating the impact of agricultural activities on groundwater quality, is tested in two areas in the south of Portugal with modest results. Intensive citri- and horticulture require large amounts of fertiliser and water supplied by irrigation, which induces groundwater salinisation and contamination by nitrates. The degree of contamination varies highly within and between the study areas and is related to hydrogeological factors as well as intensity of agricultural practices. Vulnerability mapping is performed with the intrinsic DRASTIC method and the specific Susceptibility Index (SI), which is an adaptation of DRASTIC. These methods can constitute useful groundwater management tools, for instance when designating new Nitrate Vulnerable Zones as defined in the European Directive 91/676/EEC. However, in the case of DRASTIC, little correspondence exists between the most vulnerable and the most contaminated areas. This is mainly a result of underestimating the dilution capacity and overemphasising the attenuating potential of the unsaturated zone and aquifer, as both chloride and nitrate prove to be very stable contaminants. By including a parameter for land use, SI manages to produce more reliable results, although in many areas the vulnerability is overestimated.

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Resumen Se evalúa la aplicabilidad de dos métodos de estimación de vulnerabilidad en evaluar el impacto de actividades agrícolas en la calidad del agua subterránea para dos áreas en el sur de Portugal obteniendo resultados modestos. La horticultura y citricultura intensiva requiere grandes cantidades de fertilizantes y agua abastecida por riego, lo cual induce salinización de agua subterránea y contaminación por nitratos. El grado de contaminación varía fuertemente dentro y entre las áreas de estudio y se relaciona con factores hidrogeológicos así como con la intensidad de las prácticas agrícolas. El mapeo de vulnerabilidad se lleva a cabo con el método intrínsico DRASTIC y el Índice de Susceptibilidad específica (SI), el cual es una adaptación de DRASTIC. Estos métodos pueden constituir herramientas de manejo de aguas subterráneas útiles, por ejemplo al designar nuevas Zonas Vulnerables por Nitratos del modo que se definen en la Directiva Europea 91/676/EEC. Sin embargo, en el caso de DRASTIC, existen poca correspondencia entre las zonas más vulnerables y las áreas más contaminadas. Esto se debe principalmente a la subestimación de la capacidad de dilución y a al sobre énfasis del potencial de atenuación de la zona no saturada y el acuífero, ya que tanto cloruro como nitrato han probado ser contaminantes muy estables. Al incluir un parámetro del uso de la tierra, SI genera resultados más confiables, aunque en muchas áreas se sobrestima la vulnerabilidad.

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Résumé Lapplication de deux méthodes de calcul de la vulnérabilité permettant dévaluer limpact des activités agricoles sur la qualité des eaux souterraines, est testée dans deux zones du Sud du Portugal, avec des résultats modestes. La citriculture et lhorticulture intensives nécessitent de grandes quantités e fertilisants et deau souterraine pour lirrigation, ce qui induit la salinisation et la contamination des eaux souterraines par les nitrates. Le degré de contamination varie grandement à lintérieur et entre les zones détudes, en fonction des facteurs hydrogéologiques et de lintensité des pratiques agricoles. La cartographie de la vulnérabilité est mise en oeuvre via la méthodologie DRASTIC et lIndex de Susceptibilité (SI) spécifique, qui est une adaptation de la méthode DRASTIC. Ces méthodes êuvent constituer des outils de management des eaux souterraines, par exemple lors de la désignation de nouvelles zones de vulnérabilité aux Nitrates selon la n Directive Européenne 91/676/EEC. Par ailleurs dans le cas de DRASTIC, de petites correspondances existent entre les zones les plus vulnérables et les plus contaminées. Ceci est principalement le résultat dune sous-estimation de la capacité de dilution et de la sur-accentuation du potentiel datténuation de la zone non-saturée de laquifère, car et le chlore et les nitrates sont des contaminants très stables. En incluant un paramètre dutilisation des sols, SI produit des résultats plus réalistes, bien que dans de nombreuses zones la vulnérabilité soit surestimée.

     

Groundwater quality,nitrate pollution and irrigation environmental management in the Neogene sediments of an agricultural region in central Thessaly (Greece)

The degradation of groundwater quality, which has been noted in the recent years, is closely connected to the intensification of agriculture, the unreasonable use of chemical fertilizers and the excess consumption of large volumes of irrigation water. In the hilly region of central Thessaly in Greece, which suffers the consequences of intense agricultural use, a hydrogeological study is carried out, taking groundwater samples from springs and boreholes in the Neogene aquifers. The aim of this study is the investigation of irrigation management, water quality and suitability for various uses (water supply, irrigation), the degradation degree and the spatial distribution of pollutants using GIS. The following hydrochemical types prevail in the groundwater of the study area: Ca–Mg–HCO₃, Mg–Ca–Na–HCO₃ and Na–HCO₃. In the above shallow aquifers, especially high values of NO₃ ⁻ (31.7–299.0), NH₄ ⁺ (0.12–1.11), NO₂ ⁻ (0.018–0.109), PO₄ ³⁻ (0.07–0.55), SO₄ ²⁻ (47.5–146.5) and Cl⁻ (24.8–146.5) are found, particularly near inhabited areas (values are in mg L⁻¹). The water of shallow aquifers is considered unsuitable for human use due to their high polluting load, while the water of the deeper aquifers is suitable for human consumption. Regarding water suitability for irrigation, the evaluation of SAR (0.153–7.397) and EC (481–1,680 μS cm⁻¹) resulted in classification category ‘C3S1’, indicating high salinity and low sodium water which can be used for irrigation in most soils and crops with little to medium danger of development of exchangeable sodium and salinity. The statistical data analysis, the factor analysis and the GIS application have brought out the vulnerable-problematic zones in chemical compounds of nitrogen and phosphates. The groundwater quality degradation is localized and related exclusively to human activities. Based on 2005 and 2008 estimates, the annual safe yield of the region’s aquifers were nearly 41.95 MCM. However, the existing situation is that 6.37 MCM of water is over extracted from these aquifers.     

Groundwater contamination with arsenic and other trace elements in an area of the pampa,province of Córdoba,Argentina

A geochemical study of groundwater of the pampa in the province of Córdoba, Argentina, was performed; the area covered approximately 10,000 km².Physical-chemical parameters, dissolved solids, and seven trace elements were determined in 60 selected water samples. Systematic and accurate measurements of arsenic, flourine, and vanadium were performed for the first time. Three trace element contaminants not reported earlier were found: an important one, selenium, and two others of less known effects, uranium and molybdenum.Eighty-four percent of the water analyzed showed arsenic contents over 0.05 mg/L, maximum contaminant level established by the U.S. Environmental Protection Agency (1982). The frequency distribution of trace elements was analyzed, and its fit to the lognormal distribution was proved by means of the Pearson and Kolmogorov-Smirnov test; the geographic distribution of the seven trace elements was mapped and its correlation with the anion-cation composition of the water was studied.The maximum arsenic, fluorine, vanadium, and uranium contents were found in the western part of the area under study, in waters containing dominant alkali metals in the cation composition. Maximum selenium and antimony contents were found in the eastern part of the area, while molybdenum distribution does not show any relationship with the other two groups. In addition, the geographic distribution of the trace elements seems to be related to the subsurface structure, which has been inferred using interactive digital analysis of Landsat imagery. The movements of the subsoil have disturbed surface and subsurface drainage influencing the water salinity and trace element contents.In order to investigate the origin of the contamination, 54 loess samples were collected in wells at depths ranging from the surface down to the water table. This loess, which has a high proportion of volcanic components, mainly rhyolitic glass, exhibits a chemical composition corresponding to that of a dacite.The loess and the volcanic glass show anomalous contents of all contaminant trace elements, mainly arsenic and selenium. For this reason loess is considered the most important contamination source in the groundwater under study.     

Assessment of nitrate contamination risk: The Italian experience

The purpose of this study is to show the results of the Italian research project of national interest (PRIN) launched in 2006 and finished in 2008, concerning the “assessment of groundwater contamination risk by nitrates assessment”. The project verified the IPNOA method for nitrate groundwater contamination risk assessment in four test-sites of Italy. The IPNOA is a parametric index which assesses the potential hazard of nitrate contamination originating from agriculture on a regional scale. The method integrates two categories of parameters: the hazard factors (HF), which represent all farming activities that cause, or might cause, an impact on soil quality in terms of nitrate (use of fertilisers, application of livestock and poultry manure, food industry wastewater and urban sludge), and the control factors (CF) which adapt the hazard factors to the characteristics of the site (geographical location, climatic conditions and agronomic practices). Finally, the Potential Risk Map is obtained by coupling the potential hazard of nitrate pollution (IPNOA) and the aquifer Contamination Vulnerability Map. The project was carried out by five Research Units (RU) from the Politecnico di Torino, Universities of Piacenza, Florence, Naples and Palermo. The geochemistry of groundwaters from the four test-sites was studied to determine the distribution of nitrate, and to evaluate groundwater chemical facies. All the study areas are affected by groundwater nitrate contamination and often by hydrogeochemical peculiarities. In some cases isotopic study, δ¹⁸O–NO₃δ¹⁵N–NO₃, allowed to differentiate nitrates of chemical fertilisers from those of biological origin, as well as denitrification processes.     

Flow and patterns of nitrate pollution in groundwater: a case study of an agricultural area in Tsukuba City, Japan

A numerical simulation was applied to first characterize the groundwater flow and patterns of nitrate pollution of a small-agricultural catchment in Tsukuba City, Japan, for a 10-year period. There was a good performance of the flow simulation. In contrast, although the transport model calculated the evolution of the plume, it only provided estimates of solute concentrations. Groundwater contamination increased exponentially during the first 594 days of the simulation, reaching then a near-equilibrium state. Fertilizer applications are responsible for most of the leaching of NO₃⁻ to groundwater, therefore, shifting of crops and the associated agricultural practices may translate into decreases of contamination levels. A series of hypothetical scenarios demonstrated that replacing grasslands by other crops may reduce the contamination levels up to 12%. As the chosen field is a representative of many other agricultural areas in Japan, the approach and results should also be applicable to similar cases around the country.     

Groundwater and surface water contamination in the area of the Hitura nickel mine, Western Finland

Tailings-derived mine drainage water that is neutral in character, has a high electrical conductivity and contains elevated sulphate, chloride and nickel concentrations, has caused deterioration in groundwater and surface water quality in the mining area of Hitura in Western Finland. This deterioration, and thereby the location of the contaminant plume, was recognized in the water chemistry in the form of a gradual change in ion composition from Ca-HCO₃-type water towards a Mg-SO₄-rich type. It was possible to define the extent of the pollution by using cluster analysis to distinguish between hydrochemically different regimes and performing an electrical sounding survey. The results indicated that contamination is most intense close to the tailings impoundment and is related to an esker complex running across this area. Nevertheless, the water in the eastern and southern parts of the area upgradient of the hydraulic head is uncontaminated and suitable for water supply purposes.     

Spatial assessment of groundwater quality in the Jangseong region,South Korea

A total of 129 groundwater samples were collected in the Jangseong region of South Korea to characterize and evaluate groundwater quality and its suitability for irrigation and domestic uses. Samples were chemically analyzed for major ions, pH, electrical conductivity, and total dissolved solids following standard methods. The AquaChem 2014.2 model linked with PHREEQC was used for the statistical analysis and characterization of the hydrochemistry of the groundwater. The analysis showed that in all samples Ca–HCO₃ was the leading water type and that the abundance of major cations was in the order Ca > Na > Mg > K, and of anions in the order HCO₃ > Cl > SO₄ > F. According to the correlation analysis, Ca showed strong interdependence with HCO₃, suggesting that these parameters may have originated from common sources. Saturation index calculations indicated that all samples were undersaturated with respect to aragonite, calcite, dolomite, fluorite, gypsum, halite, and siderite, and oversaturated with respect to goethite and hematite. The irrigation suitability analysis revealed that groundwater in the Jangseong area can be used for irrigation without any restrictions based on EC, sodium adsorption ratio, percent sodium, residual sodium carbonate, Kelley ratio, permeability index, and the US Salinity Laboratory diagram analysis. The drinking water suitability analysis made for major parameters by comparison with the WHO guidelines indicates that the groundwater in the area is suitable for drinking except in some samples with high nitrate–N concentrations. The elevated nitrate concentrations in the groundwater are likely an indicator of agricultural pollution.