Groundwater Contaminant Model Research Articles

Groundwater contamination modelling in Ayad River Basin, Udaipur

Groundwater, a vital freshwater resource catering to agricultural, domestic, and industrial needs, faces a pressing challenge of contamination due to escalating human activities. This study focuses on the Ayad River Basin in the Udaipur district of Rajasthan, employing the FEFLOW simulation code for the first time. A steady-state numerical model and a groundwater contaminant prediction model for total dissolved solids (TDS), nitrate, and fluoride were developed, simulating trends over the next five years with an accuracy exceeding 95%. The results reveal an eastward increase in TDS, nitrate, and fluoride concentrations, attributed to contamination from two waste disposal sites-Titadi and Baleecha. Titadi, operational for four decades until closure in 2010, retains residual waste over 32 thousand m2. The initiation of a new dumping ground at Baleecha by the Udaipur Municipal Corporation post-2010 exacerbates regional contamination. Nitrate contamination is particularly high in agricultural zones with excessive chemical fertilizer usage. Of the 27 scenarios tested, 23 support using the water for irrigation but would require treatment before using it for drinking. Recommendations include deploying a chemical sensor network for real-time data input into the web enabled FEFLOW model, real-time monitoring and alerts, and a mobile application providing personalized guidance on water usage and health risks in case of contamination. This study can be beneficial to decision-makers, who work on the policy and groundwater management strategies.

Cancer risk assessment and modeling of groundwater contamination near industrial estate, Lahore, Pakistan

Abstract More than 60% of the population of Pakistan has no access to safe drinking water. Industrial zones near populated areas make conditions more severe due to continuous contamination. The aim of this study was to use statistical tools for correlation and source identification and health risk assessment of contamination due to Sundar Industrial Estate (SIE), Lahore, Pakistan. Drinking and wastewater samples were collected from SIE and analyzed for physical, chemical, microbial, and heavy metals analysis. Results showed that heavy metals and microbial contamination were beyond the National Drinking Water Quality Standards of Pakistan while high values of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) wastewater were responsible for contamination of drinking water through seepage. There was a medium to strong correlation among parameters of all samples as indicated by Pearson correlation and analysis of variance. Principal component analysis and cluster analysis indicated sources of contamination, i.e., refuse leachate and untreated effluent discharges as main source of pollutants for drinking water. Health risk assessment showed a high intake of heavy metals through drinking water. Hazard quotient and hazard index indicated high probability of non-carcinogenic risk while cancer risk assessment suggested that out of every 100 of the population 93 people may suffer carcinogenic effects.

Mathematical modeling of groundwater contamination with varying velocity field

Abstract In this study, analytical models for predicting groundwater contamination in isotropic and homogeneous porous formations are derived. The impact of dispersion and diffusion coefficients is included in the solution of the advection-dispersion equation (ADE), subjected to transient (time-dependent) boundary conditions at the origin. A retardation factor and zero-order production terms are included in the ADE. Analytical solutions are obtained using the Laplace Integral Transform Technique (LITT) and the concept of linear isotherm. For illustration, analytical solutions for linearly space- and time-dependent hydrodynamic dispersion coefficients along with molecular diffusion coefficients are presented. Analytical solutions are explored for the Peclet number. Numerical solutions are obtained by explicit finite difference methods and are compared with analytical solutions. Numerical results are analysed for different types of geological porous formations i.e., aquifer and aquitard. The accuracy of results is evaluated by the root mean square error (RMSE).

Assessment of Textural Variational Pattern and Electrical Conduction of Economic and Accessible Quaternary Hydrolithofacies via Geoelectric and Laboratory Methods in SE Nigeria: A Case Study of Select Locations in Akwa Ibom State

Abstract: Textural variational pattern of economic and accessible Quaternary aquifer repositories and its conductivity in the south-eastern Nigeria have been assessed through the integration of vertical electrical sounding and laboratory measurements. The results have shown the lithological attributes, pore-water and amount of residual clay minerals in the assumed clean sand; mechanism of charge fixation at the fluid - surface interface; intricate geometry of pores and pore channels; formation’s ability to transmit pore-water and cation exchange capacity.The connections of electrical and hydraulic properties and their distributions have been established. The average interface conductivity contributed by residual clay minerals in assumed clean sands of the aquifer repositories in the study area have been estimated as 30μS/m. Intrinsic average porosity and formation factor have been respectively deduced as 12% and 14.75. Comparing the simulated aquifer formation factor obtained from the observed porosity data with the observed aquifer formation factor, indicates the that study area has 0.5 ≤ a ≤ 0.8 pore geometry factor and 1.5 ≤ m ≤ 2.0 cementation factor as the best fitting values. The interrelations between aquifer parameters have been established through different plots and the aquifer have been empirically proved to be associated with residual clay minerals as the interface conductivity Cq is not equal to zero. The wide ranges of parameters estimated are an indication of variations in grain size. The estimated intrinsic average porosity, formation factor and the average BQv are viable in characterizing the aquifer flow dynamics and contaminant modelling in the associated aquifer sands For low pore geometry factors a (0.2) and low cementation factor m (0.5) the formation factor remains fairly constant. However, marked variability is noticed at higher a (1.0) and m (2.5). Despite the observed variability in formation factors at the indicated porosities, the spatial or geometrical spread of the formation factor remains unchanged in the aquifer units. The Tables for geoelectric and petrophysical parameters and the associated mathematical models generated in this study can be used for groundwater contaminant modelling and simulation of pore space parameters with reasonable accuracy.

Hypospadias and maternal exposure to atrazine via drinking water in the National Birth Defects Prevention study.

BackgroundHypospadias is a relatively common birth defect affecting the male urinary tract. It has been suggested that exposure to endocrine disrupting chemicals might increase the risk of hypospadias by interrupting normal urethral development.MethodsUsing data from the National Birth Defects Prevention Study, a population-based case-control study, we considered the role of maternal exposure to atrazine, a widely used herbicide and potential endocrine disruptor, via drinking water in the etiology of 2nd and 3rd degree hypospadias. We used data on 343 hypospadias cases and 1,422 male controls in North Carolina, Arkansas, Iowa, and Texas from 1998–2005. Using catchment level stream and groundwater contaminant models from the US Geological Survey, we estimated atrazine concentrations in public water supplies and in private wells. We assigned case and control mothers to public water supplies based on geocoded maternal address during the critical window of exposure for hypospadias (i.e., gestational weeks 6–16). Using maternal questionnaire data about water consumption and drinking water, we estimated a surrogate for total maternal consumption of atrazine via drinking water. We then included additional maternal covariates, including age, race/ethnicity, parity, and plurality, in logistic regression analyses to consider an association between atrazine and hypospadias.ResultsWhen controlling for maternal characteristics, any association between hypospadias and daily maternal atrazine exposure during the critical window of genitourinary development was found to be weak or null (odds ratio for atrazine in drinking water = 1. 00, 95 % CI = 0.97 to 1.03 per 0.04 μg/day increase; odds ratio for maternal consumption = 1.02, 95 % CI = 0.99 to 1.05; per 0.05 μg/day increase).ConclusionsWhile the association that we observed was weak, our results suggest that additional research into a possible association between atrazine and hypospadias occurrence, using a more sensitive exposure metric, would be useful.Electronic supplementary materialThe online version of this article (doi:10.1186/s12940-016-0161-9) contains supplementary material, which is available to authorized users.

Sensitivity analysis of spatial models

Sensitivity analysis is the study of how uncertainty in model predictions is determined by uncertainty in model inputs. A global sensitivity analysis considers the potential effects from the simultaneous variation of model inputs over their finite range of uncertainty. A number of techniques are available to carry out global sensitivity analysis from a set of Monte Carlo simulations; some techniques are more efficient than others, depending on the strategy used to sample the uncertainty of model inputs and on the formulae employed for estimating sensitivity measures. The most common approaches are summarised in this paper by focusing on the limitations of each in the context of a sensitivity analysis of a spatial model. A novel approach for undertaking a spatial sensitivity analysis (based on the method of Sobol' and its related improvements) is proposed and tested. This method makes no assumptions about the model and enables the analysis of spatially distributed, uncertain inputs. The proposed approach is illustrated with a simple test model and a groundwater contaminant model.

Modeling of Groundwater Contamination by Phenol Released from Spilled Bitumen

AbstractLeaching of phenol from spilled bitumen into flowing aquifer poses an environmental threat to groundwater contamination. A two‐dimensional model with de‐coupled transfer was built to model phenol propagation in the flowing stream. The model predicted that the produced phenol concentration monitored at an observation well would rise sharply and then decline gradually as the phenol flux emerging from the bitumen surface was depleted with time. The model is useful in estimating the size of the spill, produced phenol concentration, phenol spatial distribution and the time required for the phenol concentration to decline to an environmentally acceptable level. It is well suited to other water pollution problems with chemical spills.

The impact of a contaminated lignite seam on groundwater quality in the aquifer system of the Bitterfeld region - modeling of groundwater contamination.

Until 1990 the Bitterfeld region (Germany) was heavily polluted by mining, an obsolete chemical industry and the uncontrolled deposition of chemical wastes. The cessation of lignite-mining and open-pit drainage may result in a rise of the groundwater level followed by the mobilization of contaminants, especially halogenated hydrocarbons.At a research area in Bitterfeld, highly mobile chlorinated hydrocarbons were detected in both groundwater and sediments. In particular, the pollutants were found to have penetrated a lignite seam separating the quaternary and the tertiaryaquifers. The consequences of the present situation for the progressive groundwater quality of the quaternary aquifer are assessed by means of hydrodynamic modeling using the groundwater simulation program FEFLOW.Starting from the results of the preliminary investigations and adjusting the relevant hydrogeological parameters for diffusion, dispersion, adsorption and initial pollutant distributions, various scenarios were modeled and discussed. It was shown that the impact of a diffusion-controlledscenario on groundwater quality can be neglected, and that only the reversal of the advective vertical direction of flow from the lower seam border to the surface will result in a significant deterioration of groundwater quality.