Groundwater Contamination Studies Research Articles

Controlling aquifer nitrogen levels when fertilizing crops: A study of groundwater contamination and denitrification

Nitrogen levels in groundwater are a safety concern because many of the aquifers are below intensive agricultural production areas. This paper uses a dynamic model of groundwater flow and denitrification to determine if cropping practices with heavy nitrogen use, such as continuous corn, cause the aquifer nitrogen level to exceed the EPA limit. In many instances, high nitrogen use by farmers does not lead to excessive nitrogen levels in the aquifer. However, in those situations where aquifer levels are too high, a reduction in fertilizer can lower aquifer nitrogen without a similar loss in profitability. A key point for aquifer nitrogen levels is the rate of denitrification. If this rate is too low, then nitrogen will likely be a problem no matter what farmers do. The effects of a nitrogen standard versus a nitrogen tax are also addressed and results show that information about the aquifer is needed for either to be effective. In addition, an input tax would have to be relatively large to be effective.

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.

Experimentally Determined Uranium Isotope Fractionation During Reduction of Hexavalent U by Bacteria and Zero Valent Iron

Variations in stable isotope ratios of redox sensitive elements are often used to understand redox processes occurring near the Earth's surface. Presented here are measurements of mass-dependent U isotope fractionation induced by U(VI) reduction by zerovalent iron (Fe0) and bacteria under controlled pH and HCO3- conditions. In abiotic experiments, Fe0 reduced U(VI), but the reaction failed to induce an analytically significant isotopic fractionation. Bacterial reduction experiments using Geobacter sulfurreducens and Anaeromyxobacter dehalogenans reduced dissolved U(VI) and caused enrichment of 238U relative to 235U in the remaining U(VI). Enrichmentfactors (epsilon) calculated using a Rayleigh distillation model are -0.31% per hundred and -0.34% per hundred for G. sulfurreducens and A. dehalogenans, respectively, under identical experimental conditions. Further studies are required to determine the range of possible values for 238U/235U fractionation factors under a variety of experimental conditions before broad application of these results is possible. However, the measurable variations in delta(5238)U show promise as indicators of reduction for future studies of groundwater contamination, geochronology, U ore deposit formation, and U biogeochemical cycling.

Groundwater Contamination Study of the Islamabad Aquifers and their Graphical Projection using "HC-GRAM" Software

Groundwater Contamination Study of the Islamabad Aquifers and their Graphical Projection using "HC-GRAM" Software

Estimation of Spilled Hydrocarbon Volume – The State-of-The-Art

With the increase in the environmental awareness and reorganization of the need for its protection, the study of soil and groundwater contamination and its remediation have become the focus of numerous researchers. Intentional and unintentional release of hydrocarbon into soil and subsurface pose a great threat to the biosphere environment. The quantification of spilled volume has primary importance for carrying out the remediation work and is considered a first step in the remediation hierarchy. Different investigators approached the problem from many viewpoints, and the resulting achievements are so extensive and scattered that it seems essential to inventory the completed works. This paper presents a systematic study of the available experimental and theoretical works. A complete picture of the present status of the problem is also provided. Issues that remain unresolved and obscure by the current day investigators are pointed out to facilitate future research directions and more comprehensive analyses of the quantification of spilled hydrocarbon volumes.

Application of modelling by the study of ground water contamination with nitrates under grasslands

At permanent grassland in the foothill regions of the Šumava (545 m a.s.l. subassociation Trifolio-Festucetum alopecuretosum Neuhäusl 1972), relations between the use of different doses of N(+PK) and contamination of ground waters with nitrates have been studied with the application of deterministic and probabilistic models with the aim of elaborating a theoretical basis and new methodological approaches for polycriterial optimisation of fertilisation of grass stands. Mutual relations between the use of doses N(+PK), build-up of primary production and perlocations of NO<sub>3</sub><sup>–</sup> into ground waters, expressed by that of unit and marginal values of both these processes showed a mirror-like inversion course with a remarkable co-incidence of reverse local extremes. Within the range of doses from 0 to 100 kg N(+PK)/haP helps, at the ratio of the applied doses P:N 1:1.5–2.5, to a considerable decrease in the concentration of NO<sub>3</sub><sup>–</sup> in ground waters. Specification of suitable doses of N(+PK) to ecologically and phytocenologically similar stands is discussed.

Evaluation of soil temperature effect on herbicide leaching potential into groundwater in the Brazilian Cerrado

The effect of annual variations in the daily average soil temperatures, at different depths, on the calculation of pesticide leaching potential indices is presented. This index can be applied to assess the risk of groundwater contamination by a pesticide. It considers the effects of water table depth, daily recharge net rate, pesticide sorption coefficient, and degradation rate of the pesticide in the soil. The leaching potential index is frequently used as a screening indicator in pesticide groundwater contamination studies, and the temperature effect involved in its calculation is usually not considered. It is well known that soil temperature affects pesticide degradation rates, air–water partition coefficient, and water–soil partition coefficient. These three parameters are components of the attenuation and retardation factors, as well as the leaching potential index, and contribute to determine pesticide behavior in the environment. The Arrhenius, van’t Hoff, and Clausius–Clapeyron equations were used in this work to estimate the soil temperature effect on pesticide degradation rate, air–water partition coefficient, and water–soil partition coefficient, respectively. The relationship between leaching potential index and soil temperature at different depths is presented and aids in the understanding of how potential pesticide groundwater contamination varies on different climatic conditions. Numerical results will be presented for 31 herbicides known to be used in corn and soybean crops grown on the municipality of São Gabriel do Oeste, Mato Grosso do Sul State, Brazil.

Prevention versus Treatment under Precautionary Regulation: A Case Study of Groundwater Contamination under Uncertainty

AbstractPolicy discussions on agricultural pollution problems characterize prevention as more cost effective and precautionary than ex post treatment. We derive conditions under which treatment alone is more cost effective in situations involving multiple sources of emissions, multiple sites affected, and a commonly used precautionary approach to uncertainty. We also show that a greater degree of precaution can result in less reliance on prevention. An empirical case study indicates that treatment alone is the most cost‐effective means of dealing with nitrate in most Maryland community water system wells. The use of leaching prevention measures is restricted to the most intensive poultry producing areas. The incremental cost of precaution is substantial.

Study of groundwater contamination by radioactive brine: the Lake Karachai case

Major hydrodynamic and hydrogeochemical mechanisms governing subsurface transport of radioactive brine released from a waste-disposal site known as Lake Karachai are investigated on the basis of field and laboratory data analysis and numerical modeling. In this work, some results regarding density-induced transport and some implications regarding the experimental study of geochemical interactions are presented. A set of alternative models incorporating different ideas on conceptualization of flow and mass-transport processes has been applied. Both sharp interface (Densflow) and fully miscible (Tough2 and Codesa-3D) models were used for simulation of the plume spreading. The major factors controlling preferential flow paths of the brine movement were investigated. The calibration of flow/transport models was based on hydrodynamic and geochemical data on regime of groundwater within the contaminated site. Preliminary long-term predictions were performed. Data from laboratory experiments on the study of radio-strontium adsorption and diffusion into porous matrix were used for modeling of the reactive component transport. In particular, a relationship between the adsorption distribution constant and NaNO3 content established under laboratory conditions has been incorporated into the transport code.

Use of the geophysical method EM 34-3 in the study of groundwater contamination by coal waste and ashes

The main objective of this paper is to evaluate the efficiency of the geophysical technique EM – 34 – 3 in the study of the groundwater contamination by residues from coal processing. It was applied, in the coal waste and ashes disposal site – CH 20, located in the municipal district of Charqueadas, the electromagnetic geophysical method EM – 34 – 3, which measures the electric conductivity of the medium in subsurface. It was noticed that the highest anomalous electrical conductivity values and ions content were placed inside the disposal site with the most significant contamination situated in the phreatic aquifer. Besides, it was verified an incipient pollution plume in the direction of groundwater flow (to SW). The methodology presented good results in the delimitation of the polluted area, supplying a guiding character for posterior sampling campaigns of contamination groundwater degree and indicating the concentrations of the pollutant elements in subsurface.

Systematic Makings of Early Stage Hydrogeologic Conceptual Models

AbstractTechniques to obtain optimal value from existing hydrogeological information are neglected in many ground water contamination studies, resulting in great costs to the public. Data collection and routine interpretations should not be good enough for hydrogeologists, who should be inherently adept at keen early perspectives and applying useful generalizations. Techniques are available to obtain and explain expanded knowledge from piecemeal and imprecise information at the early stages of site studies. Scarcity of precise data should not be a deterrent. This needed mindset should precede the prevailing mindset of initial collection of extensive new data, followed by data interpretation and mathematical modeling. The existing mindset is often guided by rigid regulations.The procedure of interlocking the past with the present to predict the future through the systematic use of generalizations and retrodictive inferences builds a prior conceptual model explanation (PCME). This early PCME is an organized, mental picture or discernment of a hydrogeological setting displaying three‐dimensional hydrogeologic features, the discernment being capable of explaining in narrative form the general fluid mechanics and contaminant behavior within imprecise but reasonable bounds. This characterization is logically followed by possible cause‐and‐effect relations and predictions of extended consequences of natural and human actions. A site PCME has sound support from the cross‐checking of interrelated factors that leads to almost interlocking proofs.

Experimental Study of Groundwater Contamination By Phenol From Water/Heavy Oil Emulsion

Abstract A leaching experiment was conducted at 4 ° C to study the transport of phenol and chloride from a quiescent, viscous Cold Lake W/O emulsion into flowing fresh water. Test results indicated that phenol and chloride were transferred through different mechanisms. The rate-determining step for phenol transport was the slow molecular diffusion of phenol in emulsion. This was successfully modelled by a de-coupled second order diffusion equation from which the diffusion coefficient of phenol in emulsion was determined to be 2.2 x?10−8 cm2/s. Chloride was transported through direct contact of the emulsified water droplets with the leaching water in an 82 µm thick coalescence layer. The transport was essentially complete in less than two days and no further leaching was observed for the rest of the experiment. The bulk emulsified water was stable with no coalescing or segregation with time. The phenol/chloride transport model can be readily scaled to predict the mass transfer of these two chemicals from a contaminated zone into a flowing aquifer as shown in a subsequent paper. No appreciable air oxidation or biological degradation of phenol was detected within the experiment time frame of 61 days. Introduction Similar to coal gasification, the Cold Lake steam stimulation process also generates highly toxic by-products in the formation. These by-products, including various types of phenols, carboxylic acids and other high molecular weight acidic compounds generically classified as humic acids(1), are weak acids. Being soluble both in bitumen and especially in the high pH steam condensate, these compounds are brought to the surface by the produced water and bitumen. Cold Lake bitumen tends to form a stable, highly viscous water in oil emulsion with the produced water under minimal stress. The water content in the emulsion(2) can be as high as 40%. After separation, part of the produced water is softened and re-cycled for steam generation and the excess produced water, together with other harmful waste streams, are injected through a disposal well into an isolated zone to avoid aquifer contamination. In 1988, a leaky seal in the abandoned well C7-13 at Cold Lake caused an accidental spill of bitumen in the form of a water-in-oil emulsion and produced water into a near-surface aquifer zone where the bitumen and the produced water were in a danger of being contacted by the flowing aquifer(3). Although the W/O emulsion was practically immobile at the formation temperature of 4 ° C due to its high viscosity, the toxic phenolic compounds could still be expected to leach slowly into the flowing stream, posing a threat of potential groundwater contamination. To assess the environmental impact of phenol contamination on groundwater, water was produced from a newly drilled well and continuously monitored for chloride and phenol levels. In the meantime, experiments were designed and conducted in the lab to study the rate and mechanism of the release of phenol into fresh water. Experiments were also carried out to quantify the extent of natural degradation of phenol via air oxidation and biological pathways.

A new approach to understanding multiple-source groundwater contamination: Factor analysis and chemical mass balances

Groundwater contamination studies are becoming more important particularly concerning their ability to identify specific sources of the contamination. In most cases, groundwater contamination studies are based upon general physical and/or chemical characterization of subsurface waters and provide information only as to whether a specific sample from a particular aquifer is being contaminated or not. A technique utilizing instrumental neutron activation analysis together with principal componene factor analysis and chemical mass balances has been shown to be a useful tool in helping to differentiate among several possible sources for groundwater contamination. In addition, this technique has been utilized to apportion relative contributions from each source of contamination.

A study of ground water contamination by arsenic in the residential area of behala, calcutta due to industrial pollution

Due to the discharge of industrial effluent after production of the insecticide Paris-Green [Copper acetoarsenite Cu(CH 3COO) 2.3Cu(AsO 2) 2] by a local factory at the P. N. Mitra Lane, Behala, ground water has become contaminated with arsenic. More than seven thousand people were using this arsenic contaminated tube-well water for drinking and house-hold purposes. Many people of the area were hospitalised and symptoms of arsenic toxicity were visible amongst a large number of the population. Analytical study reveals that soil around the area of effluent dumping point, which is at the middle of the locality, contains a very high concentration of arsenic and copper. For the last 20 years this factory had been producing 20 tons of Paris-Green per year and had been dumping its effluent in that area. It seems, the effluent treatment for arsenic removal was not adequate and finally arsenic percolated to the underground aquifers. Consequently, arsenic concentration in the ground water is very high. Both arsenite and arsenate are present in ground water. An alternate source of water other than the ground water is immediately necessary for the people of P. N. Mitra Lane.

A review of the attenuation of trichloroethylene in soils and aquifers

Abstract The transport, transformation, sorption and volatilization of trichloroethylene (TCE) as a non-aqueous phase liquid (NAPL) and as a dissolved aqueous constituent, under both laboratory and field conditions, are reviewed. NAPL-TCE is expected to migrate quite rapidly in soils and other water-unsaturated conditions, leaving droplets of organic liquid in the pore spaces. At the water table level, TCE may stop its downward movement and diffuse laterally, together with a slow migration downwards. From there on NAPL-TCE will slowly dissolve in groundwater. However, some specific hydraulic characteristics may induce rapid transport downwards away from the water table. TCE may appear in soils and aquifers as a result of its wide industrial use and also, possibly, as a degradation by-product of other chlorinated hydrocarbon solvents. TCE can undergo abiotic and (mostly) biotic, aerobic and (mostly) anaerobic transformations leading to less chlorinated ethenes. A half-life of 300 days was observed under field conditions. Batch and column experiments show that TCE is weakly sorbed on soil and aquifer solids with linear partition coefficients. Retardation factors in the range of l to 9 are reported from laboratory and field investigations. The adsorption is almost fully reversible. Gaseous TCE is more adsorbed than aqueous TCE, the extent of uptake being greatly influenced by the moisture content of the solid. Soil gas surveys appear as a promising technique for the study of soil and groundwater contamination by TCE. NAPL-TCE contamination should be quite effectively removed by steam injection. Because of its low adsorption and weak degradation under aerobic conditions, the diffuse contamination of aquifers by dissolved TCE can be extensive. In the case of localized and more severe pollution, approaches for the restoration of aquifers based on pumping followed by treatment at the surface may be effective but they usually are not economical. In situ treatment by stimulating the biotrans-formation is considered as a favourable alternative.

Use of soil vapor surveys in ground water contamination studies: a technique to help minimize monitoring well installation costs : Proc 1990 Annual Symposium on Geology and Geotechnical Engineering, Instrumentation and Computer Applications, Pocatello, 4–6 April 1990 P18.1–18.15. Publ Pocatello: Idaho State University, 1990

Use of soil vapor surveys in ground water contamination studies: a technique to help minimize monitoring well installation costs : Proc 1990 Annual Symposium on Geology and Geotechnical Engineering, Instrumentation and Computer Applications, Pocatello, 4–6 April 1990 P18.1–18.15. Publ Pocatello: Idaho State University, 1990

Development and use of an electrical resistivity cone for groundwater contamination studies : Campanella, R G; Weemees, I Can Geotech JV27, N5, Oct 1990, P557–567

Development and use of an electrical resistivity cone for groundwater contamination studies : Campanella, R G; Weemees, I Can Geotech JV27, N5, Oct 1990, P557–567

A Method for Assessing Residual NAPL Based on Organic Chemical Concentrations in Soil Samples

AbstractGround water contamination by non‐aqueous phase liquid (NAPL) chemicals is a serious concern at many industrial facilities and waste disposal sites. NAPL in the form of immobile residual contamination, or pools of mobile or potentially mobile NAPL, can represent continuing sources of ground water contamination. In order to develop rational and cost‐effective plans for remediation of soil and ground water contamination at such sites, it is essential to determine if non‐aqueous phase liquid (NAPL) chemicals are present in the subsurface and delineate the zones of NAPL contamination. The presence of NAPL pools may be evident as a floating or sinking phase in monitoring wells. The residual NAPL contamination may be identified in soil samples if residual contents are high and contaminated zones in the soil cores are thick. However, visual identification may not be effective if residual contents are low or if the NAPL residual is distributed heterogeneously in the samples. The chemical analysis of soil samples provides a measure of the total chemical concentration in the soil but cannot determine directly whether NAPL is present in the samples. Qualitatively, soil analyses that exhibit chemical concentrations in the percent range or >10,000 mg/kg would generally be considered to indicate the presence of NAPL. However, the results of soil analyses are seldom used in a quantitative manner to assess the possible presence of residual NAPL contamination when chemical concentrations are lower and the presence of NAPL is not obvious. The assessment of the presence of NAPL in soil samples is possible using the results of chemical and physical analyses of the soil, and the fundamental principles of chemical partitioning in unsaturated or saturated soil. The method requires information on the soil of the type typically considered in ground water contamination studies and provides a simple tool for the investigators of chemical spill and waste disposal sites to assess whether soil chemical analyses indicate the presence of residual NAPL in the subsurface.

Development and use of an electrical resistivity cone for groundwater contamination studies

The evaluation of groundwater quality has become increasingly important as more industrial waste and solid domestic refuse come into contact with groundwater. One method of detecting contaminated groundwater is by noting the electrical resistivity of the contaminated soil. This method has been applied at the University of British Columbia by the development and use of a new resistivity cone. The resistivity cone consists of four circumferential surface electrodes contained in a separate module behind a 15 cm2 piezocone. The cone has a capability of providing a continuous record of resistivity with depth.Initially, a laboratory testing program was carried out using a simplified probe design to ensure the feasibility of the project. On the basis of favourable laboratory results the module was constructed, calibrated in the laboratory, and then field tested. The paper describes the design and operation of the resistivity cone, theory and laboratory calibration, and test results from three sites in the lower mainland of British Columbia. The results of the testing program provided evidence of the reliability of the instrument and illustrated its application in determining changes in groundwater quality. Factors affecting results and applications of the resistivity cone in contaminant site investigations are discussed. Key words: electrical, resistivity, cone, groundwater, contamination, plumes, mapping, in-situ testing, soil.

Groundwater contamination field methods

Half of the drinking water in the United States comes from groundwater; 75% of the nation's cities obtain all or part of their supplies from groundwater; and the rural areas are 95% dependent upon groundwater. Therefore it is imperative that every possible precaution be taken to protect the purity of the groundwater.Because of the increasing interest in prevention of groundwater contamination and the need for nationally recognized methods for investigation of contamination, a symposium entitled “Field Methods for Groundwater Contamination Studies and Their Standardization” was held February 2–7, 1986, in Cocoa Beach, Fla. The symposium was sponsored and organized by the American Society for Testing and Materials (ASTM) Committee D18 on Soil and Rock and Committee D19 on Water. Gene Collins of the National Institute for Petroleum and Energy Research (Bartlesville, Okla.) was symposium chair, and Ivan Johnson (A. Ivan Johnson, Inc., Consulting, Arvada, Colo.) was vice chair.