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In this study, the quality of groundwater has been evaluated for irrigation in Khana and Gokana areas of Rivers State, Nigeria. Standard sampling and analytical methods were used. Chemical features were investigated via chemometric determinations, including major ions and potentially toxic elements (PTEs) and saturation index (SI) of selected mineral phases calculated using the PHREEQC software. Parameters like sodium adsorption ratio (SAR), sodium percentage (Na%), permeability index (PI), magnesium adsorption ratio (MAR), Kelly's ratio (KR), and Potential salinity (PS) were computed to ascertain its quality for irrigation purpose. Results revealed that the principal hydrochemical facies in the studied water samples is Ca–Mg–Cl. Geochemical model indicates the prevalence of dissolution process, since all carbonate and sulfate mineral phases are undersaturated. The occurrence of PTEs could be explained by the prevailing hydrogeochemical conditions and the dissolution/precipitation reactions of key mineral phases such as oxy-hydroxides. For the Khana and Gokana samples, respectively, SAR concentrations range from 0.19 to 0.71 and 0.22 to 0.80; MAR values range from 47.83 to 62.35% and 47.61 to 68.09%; KR ranges from 0.15 to 0.53 and 0.11 to 0.50; %Na ranges from 1.44 to 5.78 and 9.69 to 29.29; while PS are generally < 5. Most of the groundwaters fall into the C1–S1 and C2–S1 categories on the USSL diagram, with low-to-medium salinity hazard; while a few fall into the C3–S1 category. The deductions from the different indices computed in this study revealed that the groundwater is generally considered safe for irrigation purposes. [ABSTRACT FROM AUTHOR]

The degree of toxic metal and metalloid [metal(loid)] pollution in a tributary creek, which flows along a small-scale gold mining area, was assessed using modeled speciation profile and various environmental pollution indicators. Sediment and water samples were collected from five different locations representing the creek's upstream, midstream, and downstream areas. Concentration of As, Cd, Cu, and Pb in the sediment and aqueous samples were determined. Chemical speciation of the target analytes in the creek system was performed using geochemical software PHREEQC utilizing elemental concentration in sediment and aqueous phase, temperature, pH, dissolved oxygen, and identified minerals as input values. The concentrations of the metal(loids) in the sediments of midstream and downstream were higher compared to the average shale value (ASV) and toxicological reference values (TRV). Similarly, the total concentrations of As and Cu in creek water exceeded the local guidelines for effluent waters. Speciation results identified HAsO42−, Cd2+, CuOH+, and PbOH+ as the major species of the target analytes. Supersaturation of elements in sediment and low solubility in the aqueous matrix point out to resuspension and transport of metals as colloidal suspensions. The enrichment factor (EF) and geoaccumulation index (Igeo) values indicate significant levels of enrichment and pollution in the midstream and downstream areas. The increasing pollution load index (PLI) suggested the progressive deterioration from the upstream (0.8 to 1.7) down toward the midstream (PLI = 2.0 to 18.0) and downstream (PLI = 2.4 to 17.5). Speciation and environmental index results confirmed that anthropogenic sources in the midstream were transported to the downstream catchment. [ABSTRACT FROM AUTHOR]

Based on both chemical leaching and adsorption tests and a simple modelling using PHREEQC, geochemical behaviours of uranium during the ignimbrite-water interaction were evaluated mainly as a function of temperature, pH, and solution chemistry (esp., alkalinity). The main results of this work are: (1) uranium is more easily mobilized by slightly basic solution (pH 7.5) than by acidified water (pH 4.5) when relative concentrations of the main uranyl ion-calcium-carbonate species, CaUO(CO), increase from 0.6 to 90%; (2) the greatest leaching of uranium occurs at 50 °C (not at higher temperature) because the first dissociation constant of HCO is directly correlated with temperature up to about 50 °C, but decreases from 50 to 80 °C. This directly influences the concentration of HCO which is mirrored by dissolved CO variations; (3) the presence of alkalinity, total C-species and calcium controls the saturation index of sorbate solution with respect to calcite, influencing also speciation, solubility, and sorption of dissolved U; and (4) higher adsorption of uranium is obtained in tests with deionized water (90.0 ± 0.7 mg/kg, at equilibrium) compared to those performed with the natural water (26.0 ± 1.5 mg/kg, at equilibrium), strengthening the role of complexes between uranyl, HCO , and Ca ions in solution to explain the corresponding decrease in uranium adsorption. [ABSTRACT FROM AUTHOR]

In this study, column leaching with artificial road runoff experiments was conducted for 30 days under intermittent leaching. The heavy metal content and partitioning in the soil used in columns were characterized before and after the leaching experiments. A leaching model, PHREEQC, was used to simulate the metal speciation changes during leaching. A large portion of Cu and Pb were leached out with ARR at the early leaching stage and a slow decrease then occurred of the metal leaching toward the end of leaching period. The content of Cu and Pb associated with the oxidizable fraction (organic and sulfide bound metals) was decreased, while the content of metals associated with carbonate fraction increased by about twofold for Pb and threefold for Cu. Geochemical modeling demonstrated that Pb speciation may be dominated by carbonate in the leached soil. Geochemical modeling also indicated that the solution was under saturated with respect to the alite, calcite, and huntite mineral phases, while carbonate minerals such as annite and cerussite, and muscovite controlled the leachability of the metals. [ABSTRACT FROM AUTHOR]

Hydrochemical investigations were conducted to identify variations in surface water chemistry in different parts of the Sarcheshmeh copper complex. Twenty-three water samples from mine drainage, stream water, processing water of the concentrator plant and tailings dam water were collected to understand processes that control the elements' mobility. Changes in trace metal concentrations and variation of major ions show two distinct water types: (a) neutral mine drainage (NMD) associated with the Sarcheshmeh mine waters containing lower trace metal, SO concentrations and neutral pH values, and (b) acid mine drainage (AMD) with waters from tailings impoundments and waste rock dumps corresponding to higher trace metals (Fe, Cu, Zn, Mo) and major anions (SO and Cl) than the first type with typically acidic pH contents. As a result of Cu-Mo sulphides flotation process under alkaline conditions, high pH values, high Mo concentration and low contamination loads of Al, Mn, Fe, Cu and Cd were observed in reject waters from the concentrator plant. Sulphide oxidation (especially pyrite), dissolution-precipitation of the secondary minerals and discharge of the reject waters from concentrator plant were some of the most important factors that influence water quality at the tailings impoundments. The results of PHREEQC speciation and solubility modelling indicated supersaturation of the waters in the tailings impoundments with respect to hydronium jarosite, schwertmannite and gypsum. [ABSTRACT FROM AUTHOR]

Groundwater with elevated dissolved-solids concentrations-containing large concentrations of chloride, sodium, sulfate, and calcium-is present in the Mud Lake area of Eastern Idaho. The source of these solutes is unknown; however, an understanding of the geochemical sources and processes controlling their presence in groundwater in the Mud Lake area is needed to better understand the geochemical sources and processes controlling the water quality of groundwater at the Idaho National Laboratory. The geochemical sources and processes controlling the water quality of groundwater in the Mud Lake area were determined by investigating the geology, hydrology, land use, and groundwater geochemistry in the Mud Lake area, proposing sources for solutes, and testing the proposed sources through geochemical modeling with PHREEQC. Modeling indicated that sources of water to the eastern Snake River Plain aquifer were groundwater from the Beaverhead Mountains and the Camas Creek drainage basin; surface water from Medicine Lodge and Camas Creeks, Mud Lake, and irrigation water; and upward flow of geothermal water from beneath the aquifer. Mixing of groundwater with surface water or other groundwater occurred throughout the aquifer. Carbonate reactions, silicate weathering, and dissolution of evaporite minerals and fertilizer explain most of the changes in chemistry in the aquifer. Redox reactions, cation exchange, and evaporation were locally important. The source of large concentrations of chloride, sodium, sulfate, and calcium was evaporite deposits in the unsaturated zone associated with Pleistocene Lake Terreton. Large amounts of chloride, sodium, sulfate, and calcium are added to groundwater from irrigation water infiltrating through lake bed sediments containing evaporite deposits and the resultant dissolution of gypsum, halite, sylvite, and bischofite. [ABSTRACT FROM AUTHOR]

This work investigated the freshening time and hydrochemical evolution of coastal groundwater in two brackish aquifers in Shenzhen, China. One was the brackish aquifer that resulted from heavy pumping, and the other was the aquifer reclaimed from the coastal sea. Freshening time and hydrochemical evolution of brackish aquifers were quantitatively evaluated using PHREEQC 2.0, a one-dimensional reactive-transport model. Freshening time was shown to mainly depend on pore water velocity, while the chemical composition of groundwater was determined by the cation exchange capacity of the aquifer. It was shown that after heavy pumping ceased, the freshening time for the original coastal aquifer ranged from 20 to over 80 years. While for the coastal reclaimed aquifer, the freshening time was from 85 to 140 years, which depended on the hydraulic conductivity of the fill materials in the reclaimed site. During aquifer freshening, groundwater evolved from Na-Cl type to Ca-Mg-HCO or Na-HCO type. A sensitivity analysis showed that the freshening time was most sensitive to the pore water velocity in the aquifer, while the groundwater chemical composition was most sensitive to the values of cation exchange capacity of the aquifer. As for the dispersivity, it had almost no effect on the freshening time and the chemical composition of groundwater. [ABSTRACT FROM AUTHOR]

The Vado Carranza dump, located in the Mexicali Valley, Baja California, northwest Mexico, was operated for more than 15 years receiving about 30 tons/day of solid wastes. The disposed wastes were periodically burned in open air. The presence of a shallow aquifer in the area makes the groundwater vulnerable to contamination processes. The purpose of this study was the evaluation of heavy metals content (Cu, Cd, Ni, Pb and Zn) in soil and groundwater in the vicinity of this dump. The results indicate high content of metals in soil, mainly at a superficial level, with the highest concentrations in the areas where burning of wastes occurred. Elevated concentrations of cadmium and copper were detected in groundwater with the highest concentrations occurring in monitoring wells located in the north side of the dump, downward of groundwater flow. Although the high content of metals in soil can be attributed to the burning of waste, other sources of pollution could be the agricultural irrigation in the vicinity of the dump. The program PHREEQC was used to model the geochemical evolution of groundwater. Results suggest that evaporation of the contaminated waters circulating below the landfill is one of the key processes that explain the increased concentration of contaminants in groundwater and its seasonal variations. As groundwater flows away from the dump, evaporation can concentrate the chemicals making the water more toxic. These results are important because they illustrate processes that are likely to occur in landfills located in other desert areas of the world. [ABSTRACT FROM AUTHOR]

Groundwater, a renewable and finite natural resource, vital for man's life, social and economic development and a valuable component of the ecosystem, is vulnerable to natural and human impacts. The aim of present study is to evaluate hydrogeochemical parameters and heavy metals in groundwater and to study their spatial distribution in the Rupnagar District of Punjab. The spatial distribution of physico-chemical parameters were studied using Arc GIS 9.2. It was observed that the concentration of parameters, such as NO, Cd, Cr, Mn and Pb was above permissible limit (World Health Organization, WHO) in southern part of the study area. The heavy metal pollution index (HPI) was calculated for all sampling locations and it was found much above the critical limit of pollution. Geochemical reaction models of selected water groups were constructed using Phreeqc. Geochemical modeling suggests that sodium has source other than halite-albite and calcium has alternate source other than gypsum-carbonate or silicates. It also suggests that evaporites, ion exchange, dissolution along with anthropogenic activities are controlling the hydro-geochemistry of groundwater in the region. Various indices, such as heavy metal pollution index, permeability index, sodium adsorption ratio, were studied to verify suitability of groundwater for drinking and irrigation. [ABSTRACT FROM AUTHOR]

Adverse effect of rapid industrialization on groundwater quality and quantity is widely known problem especially in developing countries. Tirupur, which is situated on the bank of Noyyal River in India, is known for intensive textile processing activities. As groundwater is the main water source for drinking water, there is an urgency to assess the groundwater quality. Twenty groundwater samples were collected for each post and pre-monsoon sampling during August 2009 and March 2010, respectively. Chemical and statistical analysis along with numerical modelling has been performed to assess the current status. The hydro-geochemical study revealed that the dominance of Mg–Cl and Na–HCO 3 groundwater type in the upstream region Tirupur industrial hub of Noyyal River basin. Na–Cl groundwater type was found increasing in industrial hub (Kasipalayam) and downstream of the industrial hub (Anaipalayam) sites. The dominance of Na–Cl type of water is mainly due to the impact of salts like NaCl, Na 2SO 4, etc. used in textile processing, which after discharge, percolate and accumulate in the aquifers. Seasonal groundwater quality of Tirupur region as a whole showed the dominance of Ca–HCO 3−, Na–HCO 3− and Na–Cl water types. PHREEQC model output indicates that nearly all the groundwater samples were oversaturated with respect to calcite and dolomite and undersaturated with respect to gypsum and halite. The results obtained in this study were then compared with groundwater quality of the Noyyal River basin for the year 2008–2009. Among the two sites, Kasipalayam was found to be most contaminated due to incessant industrial discharge. But with the advent of new treatment technologies like CETPs having zero liquid discharge system and MBR, there has been slight decline in the concentration of different physicochemical parameters from 2002–2003 to 2008–2009. This study not only makes situation alarming but also calls for immediate attention for sustainable management of water resources. [ABSTRACT FROM AUTHOR]

Hydrochemical modeling, graphical methods, and different statistical techniques were applied to understand the nature of geological and hydrochemical processes in a shallow groundwater aquifer of the Jena biodiversity experimental field. Factor and cluster analyses were used to identify the governing underlying processes and to detect the spatial similarity between the sampling points. The hydrochemical modeling, using PHREEQC, was used to interpret the reactive minerals. Results of factor analysis indicated that there are five dominant factors which account for about 90 % of the variance of the chemical dataset in the cold season (March, April, November) and warm season (June, August). Factor analysis showed that 43 % of the variation in the cold season and 53 % of the variation in the warm season of the groundwater hydrochemical data are due to major cations and anions which reveals groundwater-geological matrix interaction. Redox and redox-sensitive elements are the next important factors and account for 15 % and 19 % variation in the cold season and warm season, respectively. The hydrochemical modeling using PHREEQC and X-ray diffraction results showed that calcite, dolomite, quartz, and siderite are reactive minerals and are responsible for changes in chemical composition. The hydrochemical data of the two seasons were also compared and the results showed that the groundwater chemistry of the study area varied seasonally in terms of some parameters such as mainly heavy metals (Ba, B, Fe, Mn, U, V, Zn, Sr, Ni), HCO, and DOC. [ABSTRACT FROM AUTHOR]

One of the uncertainties in the field of carbon dioxide capture and storage (CCS) is caused by the parameterization of geochemical models. The application of geochemical models contributes significantly to calculate the fate of the CO after its injection. The choice of the thermodynamic database used, the selection of the secondary mineral assemblage as well as the option to calculate pressure dependent equilibrium constants influence the CO trapping potential and trapping mechanism. Scenario analyses were conducted applying a geochemical batch equilibrium model for a virtual CO injection into a saline Keuper aquifer. The amount of CO which could be trapped in the formation water and in the form of carbonates was calculated using the model code PHREEQC. Thereby, four thermodynamic datasets were used to calculate the thermodynamic equilibria. Furthermore, the equilibrium constants were re-calculated with the code SUPCRT92, which also applied a pressure correction to the equilibrium constants. Varying the thermodynamic database caused a range of 61% in the amount of trapped CO calculated. Simultaneously, the assemblage of secondary minerals was varied, and the potential secondary minerals dawsonite and K-mica were included in several scenarios. The selection of the secondary mineral assemblage caused a range of 74% in the calculated amount of trapped CO. Correcting the equilibrium constants with respect to a pressure of 125 bars had an influence of 11% on the amount of trapped CO. This illustrates the need for incorporating sensitivity analyses into reaction pathway modeling. [ABSTRACT FROM AUTHOR]

Geochemical processes that take place in the aquifer have played a major role in spatial and temporal variations of groundwater quality. This study was carried out with an objective of identifying the hydrogeochemical processes that controls the groundwater quality in a weathered hard rock aquifer in a part of Nalgonda district, Andhra Pradesh, India. Groundwater samples were collected from 45 wells once every 2 months from March 2008 to September 2009. Chemical parameters of groundwater such as groundwater level, EC and pH were measured insitu. The major ion concentrations such as Ca, Mg, Na, K, Cl, and SO were analyzed using ion chromatograph. CO and HCO concentration was determined by acid-base titration. The abundance of major cation concentration in groundwater is as Na > Ca > Mg > K while that of anions is HCO > SO > Cl > CO. Ca-HCO, Na-Cl, Ca-Na-HCO and Ca-Mg-Cl are the dominant groundwater types in this area. Relation between temporal variation in groundwater level and saturation index of minerals reveals the evaporation process. The ion-exchange process controls the concentration of ions such as calcium, magnesium and sodium. The ionic ratio of Ca/Mg explains the contribution of calcite and dolomite to groundwater. In general, the geochemical processes and temporal variation of groundwater in this area are influenced by evaporation processes, ion exchange and dissolution of minerals. [ABSTRACT FROM AUTHOR]

hydrogeochemical study employing graphical, multivariate statistical, and modeling tools was conducted in an area of alluvial deposits in the Mondego river basin, to determine the factors and processes controlling the shallow groundwater chemistry. Groundwater was collected from 29 observation wells in six sampling campaigns, between March 2001 and September 2002. Samples were analyzed for basic physicochemical parameters, major ions and some minor ions. Hierarchical cluster analysis was applied to the data set, including both the spatial and temporal monitoring data and resulted in the definition of eight distinct water types. With the aid of hydrochemical (and physicochemical) scatter plots, it was possible to identify the main processes controlling the groundwater chemistry: (1) evapotranspiration and recharge; (2) calcium and magnesium carbonate and CO dissolution; (3) nitrate leaching from agriculture; (4) oxidation and reduction; and (5) cation exchange. These processes are frequently common to more than one water type but unique in combination and/or extent, in space and/or time. Geochemical modeling of the water types (using PHREEQC) allowed the validation and, to a certain extent, quantification of the processes that affect the shallow groundwater evolution. These tools can provide an essential support for the assessment of groundwater vulnerability to contamination and for the elaboration of groundwater resource management strategies. [ABSTRACT FROM AUTHOR]

In the old mining area of Rodalquilar, mine wastes, soil and sediments were characterized and the results revealed high concentration of Au, Ag, As, Bi, Cu, Fe, Mn, Pb, Se, Sb and Zn in tailings and sediments. The contaminant of greatest environmental concern is As. The mean concentration in the tailings was 679.9, and 345 mg/kg in the sediments of Playazo creek. The groundwater samples from the alluvial aquifer showed high concentration of Al, As, Cd, Fe, Hg, Mn, Ni, Pb, Se, Sb and Zn and very high concentration of chloride and sulfate, which were above the concentration defined in the European standards for drinking water. The presence of As in groundwater may be caused by the oxidation of arsenian pyrite, the possible As desorption from goethite and ferrihydrite and the jarosite dissolution. Groundwater concentrations of Cd, Fe, Mn, and possibly Cu, were associated with low values of Eh, indicating the possible dissolution of oxy-hydroxides of Fe and Mn. The mobility of metals in the column experiments show the release of Al, Fe, Mn, Cr, Cu, Ni, V and Zn in significant concentrations but below the detected values in groundwater. However, As, Cd, Sb, Se Pb and Au, are generally mobilized in concentrations above the detected values in groundwater. The possible mass transfer processes that could explain the presence of the contaminants in the aquifer and the leachates was simulated with the PHREEQC numerical code and revealed the possible dissolution of the following mineral phases: jarosite, natrojarosite, arsenian pyrite, alunite, chlorite, kaolinite and calcite. [ABSTRACT FROM AUTHOR]

CO2 geological storage is a transitional technology for the mitigation of climate change. In the vicinity of potential CO2 reservoirs in Hungary, protected freshwater aquifers used for drinking water supplies exist. Effects of disaster events of CO2 escape and brine displacement to one of these aquifers have been studied by kinetic 1D reactive transport modelling in PHREEQC. Besides verifying that ion concentrations in the freshwater may increase up to drinking water limit values in both scenarios (CO2 or brine leakage), total porosity of the rock is estimated. Pore volume is expected to increase at the entry point of CO2 and to decrease at further distances, whereas it shows minor increase along the flow path for the effect of brine inflow. Additionally, electrical conductivity of water is estimated and suggested to be the best parameter to measure for cost-effective monitoring of both worst-case leakage scenarios. [ABSTRACT FROM AUTHOR]