Evaluation of molecular- and culture-dependent MST markers to detect fecal contamination and indicate viral presence in good quality groundwater

Microbial contamination of groundwater represents a significant health risk to resource users. Culture-dependent Bacteroides phage and molecular-dependent Bacteroidales 16S rRNA assays are employed in microbial source tracking (MST) studies globally, however little is known regarding how these important groups relate to each other in the environment and which is more suitable to indicate the presence of waterborne fecal pollution and human enteric viruses. This study addresses this knowledge gap by examining 64 groundwater samples from sites with varying hydrogeological properties using a MST toolbox containing two bacteriophage groups (phage infecting GB-124 and ARABA-84), and two Bacteroidales 16S rRNA markers (Hf183 and BacR); those were compared to fecal indicator bacteria, somatic coliphage, Bacteroidales 16S rRNA marker AllBac, four human enteric viruses (norovirus GI and II, enterovirus and group A rotavirus) and supplementary hydrogeological/chemical data. Bacteroidales 16S rRNA indicators offered a more sensitive assessment of both human-specific and general fecal contamination than phage indicators, but may overestimate the risk from enteric viral pathogens. Comparison with hydrogeological and land use site characteristics as well as auxiliary microbiological and chemical data proved the plausibility of the MST findings. Sites representing karst aquifers were of significantly worse microbial quality than those with unconsolidated or fissured aquifers, highlighting the vulnerability of these hydrogeological settings.

The added value of water footprint assessment for national water policy: a case study for Morocco

A Water Footprint Assessment is carried out for Morocco, mapping the water footprint of different activities at river basin and monthly scale, distinguishing between surface- and groundwater. The paper aims to demonstrate the added value of detailed analysis of the human water footprint within a country and thorough assessment of the virtual water flows leaving and entering a country for formulating national water policy. Green, blue and grey water footprint estimates and virtual water flows are mainly derived from a previous grid-based (5×5 arc minute) global study for the period 1996–2005. These estimates are placed in the context of monthly natural runoff and waste assimilation capacity per river basin derived from Moroccan data sources. The study finds that: (i) evaporation from storage reservoirs is the second largest form of blue water consumption in Morocco, after irrigated crop production; (ii) Morocco’s water and land resources are mainly used to produce relatively low-value (in US$/m³ and US$/ha) crops such as cereals, olives and almonds; (iii) most of the virtual water export from Morocco relates to the export of products with a relatively low economic water productivity (in US$/m³); (iv) blue water scarcity on a monthly scale is severe in all river basins and pressure on groundwater resources by abstractions and nitrate pollution is considerable in most basins; (v) the estimated potential water savings by partial relocation of crops to basins where they consume less water and by reducing water footprints of crops down to benchmark levels are significant compared to demand reducing and supply increasing measures considered in Morocco’s national water strategy.

Science-based decision-making on complex issues: Marcellus shale gas hydrofracking and New York City water supply

Complex scientific and non-scientific considerations are central to the pending decisions about "hydrofracking" or high volume hydraulic fracturing (HVHF) to exploit unconventional natural gas resources worldwide. While incipient plans are being made internationally for major shale reservoirs, production and technology are most advanced in the United States, particularly in Texas and Pennsylvania, with a pending decision in New York State whether to proceed. In contrast to the narrow scientific and technical debate to date, focused on either greenhouse gas emissions or water resources, toxicology and land use in the watersheds that supply drinking water to New York City (NYC), I review the scientific and technical aspects in combination with global climate change and other critical issues in energy tradeoffs, economics and political regulation to evaluate the major liabilities and benefits. Although potential benefits of Marcellus natural gas exploitation are large for transition to a clean energy economy, at present the regulatory framework in New York State is inadequate to prevent potentially irreversible threats to the local environment and New York City water supply. Major investments in state and federal regulatory enforcement will be required to avoid these environmental consequences, and a ban on drilling within the NYC water supply watersheds is appropriate, even if more highly regulated Marcellus gas production is eventually permitted elsewhere in New York State.

Potential water quality impacts originating from land burial of cattle carcasses

Among the conventional disposal methods for livestock mortalities, on-farm burial is a preferred method, but the potential water quality impacts of animal carcass burial are not well understood. Typically, on-farm burial pits are constructed without liners and any leachate produced may infiltrate into soil and groundwater. To date, no information is available on temporal trends for contaminants in leachate produced from livestock mortality pits. In our study, we examined the concentrations of conventional contaminants including electrical conductivity, COD, TOC, TKN, TP, and solids, as well as veterinary antimicrobials and steroid hormones in leachate over a period of 20 months. Most of the contaminants were detected in leachate after 50 days of decomposition, reaching a peak concentration at approximately 200 days and declined to baseline levels by 400 days. The estrogen 17β-estradiol and a veterinary antimicrobial, monensin, were observed at maximum concentrations of 20,069 ng/L and 11,980 ng/L, respectively. Estimated mass loading of total steroid hormone and veterinary pharmaceuticals were determined to be 1.84 and 1.01 μg/kg of buried cattle carcass materials, respectively. These data indicate that leachate from carcass burial sites represents a potential source of nutrients, organics, and residues of biologically active micro-contaminants to soil and groundwater.

Preliminary risk assessment of radon in groundwater: a case study from Eskisehir, Turkey

The aim of this study was to determine the radon concentrations in the water supplies of a residential area of central west Anatolia, Turkey. This research provides a preliminary risk assessment for inhabitants in the study area which can be applied for other regions. In 14 out of the 19 water supplies analysed, radon concentrations exceeded the maximum contaminant level (11.1 Bq l(-1)). The total annual effective doses of 10 for the wet season and 14 for the dry season out of the 19 water supplies are greater than the values recommended by EPA [Cancer Risk Coefficients for Environmental Exposure to Radionuclides, Federal Guidance Report No. 13 (US Environmental Protection Agency, Washington, DC, 1999) < http://www.epa.gov/rpdweb00/docs/federal/402-r-99-001.pdf >] (0.1 mSv a(-1)). The elevated radon concentrations in water resources are most probably linked with geological origin which contains significant amounts of radioactive minerals.

Pit latrines and their impacts on groundwater quality: a systematic review

BACKGROUND

Pit latrines are one of the most common human excreta disposal systems in low-income countries, and their use is on the rise as countries aim to meet the sanitation-related target of the Millennium Development Goals. There is concern, however, that discharges of chemical and microbial contaminants from pit latrines to groundwater may negatively affect human health.

OBJECTIVES

Our goals were to a) calculate global pit latrine coverage, b) systematically review empirical studies of the impacts of pit latrines on groundwater quality, c) evaluate latrine siting standards, and d) identify knowledge gaps regarding the potential for and consequences of groundwater contamination by latrines.

METHODS

We used existing survey and population data to calculate global pit latrine coverage. We reviewed the scientific literature on the occurrence of contaminants originating from pit latrines and considered the factors affecting transport of these contaminants. Data were extracted from peer-reviewed articles, books, and reports identified using Web of ScienceSM, PubMed, Google, and document reference lists.

DISCUSSION

We estimated that approximately 1.77 billion people use pit latrines as their primary means of sanitation. Studies of pit latrines and groundwater are limited and have generally focused on only a few indicator contaminants. Although groundwater contamination is frequently observed downstream of latrines, contaminant transport distances, recommendations based on empirical studies, and siting guidelines are variable and not well aligned with one another.

CONCLUSIONS

In order to improve environmental and human health, future research should examine a larger set of contextual variables, improve measurement approaches, and develop better criteria for siting pit latrines.

[Monitoring of quality of drinking groundwaters on the territory of the Republic of Mari El]

In the paper the hygienic characteristics of groundwaters used for drinking water supply of the population of the Republic of Mari El is presented The features of the quality of groundwaters in different areas of the country have been detected, the causes of the deterioration of drinking water, which can act as a risk to public health have been shown.

Removal of 1,1,1-trichloroethane from aqueous solution by a sono-activated persulfate process

1,1,1-Trichloroethane (TCA), labeled as a priority pollutant by the Environmental Protection Agency (EPA) of China, can be removed from groundwater by sonochemical oxidation. The sonochemical oxidation of TCA in the presence of persulfate (PS) showed a significant synergistic effect. The operational parameters, ultrasonic frequency, PS/TCA molar ratio, radical scavenger, inorganic anions (Cl(-), CO(3)(2-), HCO(3)(-) and NO(3)(-)) and humic acid (HA), were evaluated during the investigation of the sonochemical reaction. The results showed that the degradation of TCA followed pseudo-first-order kinetics, and the rate constant was found to increase with increasing ultrasonic frequency but to decrease with both an increasing PS/TCA molar ratio and an increasing concentration of inorganic anions. With a concentration of 4.46mg/L of HA in solution, an enhanced effect was observed. Further addition of HA retarded the degradation rate of TCA. TCA could be eliminated almost completely by sono-activated persulfate oxidation, with sulfate and hydroxyl radicals serving as the principal oxidants as confirmed by the addition of radical scavengers. Eleven chlorinated degradation intermediates were detected and quantified by purge and trap gas chromatography coupled with mass spectrometry (P&T-GC-MS) in the absence of pH buffer. Three TCA degradation pathways were therefore proposed. In conclusion, the sono-activated persulfate oxidation process appears to be a highly promising technique for the remediation of TCA-contaminated groundwater.

[Algorithm for complex control and radiation-hygienic evaluation of the quality of underground drinking water in the Moscow region]

On the basis of assessing the quality of underground drinking water in the Moscow region, selected and justified in the process of radiation-ecological monitoring of water quality control criteria of the underground water sources in the region are encouraged to develop an algorithm for complete monitoring and assessing the quality of underground drinking water in the Moscow region on indicators of radiation and chemical safety, presented in a scheme.

[Monitoring the quality of groundwater exploited on the territory of the Republic of Mari El]

Hygienic characteristics of ground water used for drinking water supply of the Republic of Mari El is presented in the article. The features of the quality of ground water in different areas of the country have been revealed, the causes of the deterioration of drinking water which can act as a risk to public health have been shown.

Flux-based risk management strategy of groundwater pollutions: the CMF approach

A site- and receptor-specific risk management strategy for groundwater pollution based on the measurement of contaminant mass flux is proposed. The approach is useful and compatible with the demands formulated in the European Water Framework Directive, its Groundwater Daughter Directive and the regulations applicable in the EU member states. The proposed CMF method focuses on the following: (1) capture zones, (2) the location of control planes, (3) the definition of the maximum allowed contaminant mass discharge and (4) contaminant mass flux measurements. For every control plane, such a maximum allowed contaminant mass discharge is derived and is crucial for the receptor risk management strategy. The method is demonstrated for a large area of groundwater pollution present in the industrial area of Vilvoorde-Machelen located in Flanders, Belgium.

Research considerations for more effective groundwater monitoring

Since numerous pathogens occur in feces, water is monitored for fecal contamination using indicator organisms rather than individual pathogens. Although this approach is supported by health effects data in recreational waters, it is questionable when used for drinking water. Most outbreaks in groundwater occur in systems that have not violated the US EPA's maximum contaminant limit (MCL) for total coliforms within 12 months before the outbreak. Additionally, environmentally stable viruses and parasites are often detected in drinking water samples with no detectable indicators. Recent detections of Escherichia coli O157:H7 and Campylobacter jejuni in groundwaters in the apparent absence of indicators also cast some doubt on the worth of indicators for fecal bacterial pathogens. Individual pathogen monitoring is now technically achievable but currently unreasonable due to the number of possible pathogens and the costs involved. Several alternatives to pathogen monitoring could significantly reduce the frequency at which pathogens occur in waters testing negative for indicators: (i) increasing sample volumes for indicators, (ii) increasing monitoring frequency, (iii) using a suite of indicators, (iv) using a more conservative polymerase chain reaction (PCR) method, (v) sampling when fecal contamination is most likely present or (vi) any combination of these options.

Mechanistic investigations of Se(VI) treatment in anoxic groundwater using granular iron and organic carbon: an EXAFS study

The removal of aqueous Se(VI) from a simulated groundwater by granular iron (GI), organic carbon (OC), and a mixture of these reactive materials (GI-OC) was evaluated in laboratory batch experiments. The experiments were performed under anoxic conditions to simulate subsurface treatment. A total reaction time of 120 h (5 d) was chosen to investigate the rapid changes in speciation occurring over reaction times that are reasonable for permeable reactive barrier (PRB) systems. After 120 h, concentrations of Se decreased by >90% in the GI system, 15% in the OC system and 35% in the GI-OC mixture. Analysis of the materials after contact with Se using synchrotron-radiation based X-ray absorption spectroscopy (XAS) indicated the presence of Se(IV) and Se(0) on the margins of GI grains after 6h with evidence of SeO and SeSe bonding, whereas Se(VI) was not observed. After 72 h, Se(0) was the only form of Se present in the GI experiments. In the OC batches, the XAS analysis indicated binding consistent with sorption of aqueous Se(VI) onto the OC with only minor reduction to Se(IV) and Se(0) after 120 h. Selenium XAS spectra collected for the GI-OC mixture were consistent with spectra for Se(IV) and Se(0) on both the margins of GI grains and OC particles, suggesting that the presence of dissolved Fe may have mediated the reduction of sorbed Se(VI). The results suggest that the application of granular Fe is effective at inducing aqueous Se removal in anoxic conditions through reductive precipitation processes.

Using GA-Ridge regression to select hydro-geological parameters influencing groundwater pollution vulnerability

For groundwater conservation and management, it is important to accurately assess groundwater pollution vulnerability. This study proposed an integrated model using ridge regression and a genetic algorithm (GA) to effectively select the major hydro-geological parameters influencing groundwater pollution vulnerability in an aquifer. The GA-Ridge regression method determined that depth to water, net recharge, topography, and the impact of vadose zone media were the hydro-geological parameters that influenced trichloroethene pollution vulnerability in a Korean aquifer. When using these selected hydro-geological parameters, the accuracy was improved for various statistical nonlinear and artificial intelligence (AI) techniques, such as multinomial logistic regression, decision trees, artificial neural networks, and case-based reasoning. These results provide a proof of concept that the GA-Ridge regression is effective at determining influential hydro-geological parameters for the pollution vulnerability of an aquifer, and in turn, improves the AI performance in assessing groundwater pollution vulnerability.

Spring water quality and usability in the Mount Cameroon area revealed by hydrogeochemistry

Groundwater is the only reliable water resource for drinking, domestic, and agricultural purposes for the people living in the Mount Cameroon area. Hydrogeochemical and R-mode factor analysis were used to identify hydrogeochemical processes controlling spring water quality and assess its usability for the above uses. Main water types in the study area are Ca-Mg-HCO(3) and Na-HCO(3). This study reveals that three processes are controlling the spring water quality. CO(2)-driven silicate weathering and reverse cation exchange are the most important processes affecting the hydrochemistry of the spring waters. While tropical oceanic monsoon chloride-rich/sulfate-rich rainwater seems to affect spring water chemistry at low-altitude areas, strong correlations exist between major ions, dissolved silica and the altitude of springs. In general, the spring waters are suitable for drinking and domestic uses. Total hardness (TH) values indicate a general softness of the waters, which is linked to the development of cardiovascular diseases. Based on Na %, residual sodium carbonate, sodium adsorption ratio, and the USSL classification, the spring waters are considered suitable for irrigation. Though there is wide spread use of chemical fertilizers and intense urban settlements at the lower flanks of the volcano, anthropogenic activities for now seem to have little impact on the spring water quality.

A new approach for the assessment of groundwater quality and its suitability for irrigation: a case study of the Korba Coastal Aquifer (Tunisia, Africa)

Groundwater is the main source of water in Mediterranean, water-scarce, semiarid regions of Tunisia, Africa. In this study of the Korba coastal aquifer, 17 water wells were studied to assess their suitability for irrigation and drinking purposes. Assessment parameters include pH, salinity, specific ion toxicity, sodium adsorption ratio, nutrients, trace metals pollutants, and fecal indicators and pathogens. Results indicate that salinity of groundwater varied between 0.36 dS/m and 17.4 dS/m; in addition, its degree of restriction is defined as "none", "slight to moderate", and "severe" for 18, 23, and 59% of the studied wells, respectively. To control salts brought in by irrigation waters, the question arises as to how much water should be used to reach crop and soil requirements. To answer this question, a new approach that calculates the optimum amount of irrigation water considering the electrical conductivity of well water (ECw), field crops, and the semiarid meteorological local conditions for evapotranspiration and rainfall is developed. This is applied to the authors' case study area; barley and lettuce were selected among the commonly grown crops because they are high- and low-salinity tolerant, respectively. Leaching requirements were found to be independent of the crop selected, and depend only on the season, that is, 250 to 260 mm/month in the driest season, with a minimum of 47 mm/month though all seasons. A high bacteriological contamination appears in almost all samples. However, if disinfected and corrected for pH, all the well waters can be used for animal farming (including livestock and poultry), although only 29% could be used for human consumption.

The impacts of low-cost treatment options upon scale formation potential in remote communities reliant on hard groundwaters. A case study: Northern Territory, Australia

The majority of small, remote communities within the Northern Territory (NT) in Central Australia are reliant on groundwater as their primary supply of domestic, potable water. Saturation indices for a variety of relevant minerals were calculated using available thermodynamic speciation codes on collected groundwater data across the NT. These saturation indices were used to assess the theoretical formation of problematic mineral-scale, which manifests itself by forming stubborn coatings on domestic appliances and fixtures. The results of this research show that 63% of the measured sites within the NT have the potential to form calcium carbonate (CaCO(3)) scale, increasing to 91% in arid, central regions. The data also suggests that all groundwaters are over-saturated with respect to amorphous calcium-bridged ferric-silica polymers, based on the crystalline mineral index (Ca(3)Fe(2)Si(3)O(12)), although the quantitative impact of this scale is limited by low iron concentrations. An assessment of possible low-cost/low-technology management options was made, including; lowering the temperature of hot-water systems, diluting groundwater with rainwater and modifying the pH of the source water. Source water pH modification (generally a reduction to pH 7.0) was shown to clearly alleviate potential carbonate-based scale formation, over and above the other two options, albeit at a greater technical and capital expense. Although low-cost/low-technology treatment options are unlikely to remove severe scale-related issues, their place in small, remote communities with minor scale problems should be investigated further, owing to the social, technical and capital barriers involved with installing advanced treatment plants (e.g. reverse osmosis) in such locations.

Effects of pH and anions on the sorption of selenium ions onto magnetite

This study analyzes the influence of carbonate and silicate, which are generally abundant in granitic groundwater, on the sorption of selenium ions onto magnetite in order to understand the behaviors of selenium in a radioactive waste repository. Selenite was sorbed onto magnetite very well below pH 10, but silicate and carbonate hindered the sorption of selenite onto magnetite. On the other hand, little selenate was sorbed onto magnetite in neutral and weak alkaline solutions of 0.02 M NaNO(3) or NaClO(4), matching the ionic strength in a granitic groundwater, even though silicate or carbonate was not contained in the solutions. The surface complexation constants between selenite and magnetite were obtained by using a geochemical program, FITEQL 4.0, from the experimental data, and the formation of an inner-sphere surface complex such as =FeOSeO(2)(-) was suggested for the sorption of selenite onto magnetite from the diffuse double layer model calculation.

Water quality as an indicator of hydrogeological conditions: a case study of the Belgrade Groundwater Source (Sava/Danube confluence area)

The City of Belgrade receives most of its drinking water supply from the alluvial aquifer of the Sava River. The wells are radial, placed in the lower part of the aquifer, so they partly run below the Sava riverbed. However, the groundwater quality of the wells in one part of the source (near the confluence of the Sava and Danube rivers) is found to differ somewhat from the groundwater quality of the other wells. The finding gave rise to additional investigations. The results revealed the existence of a deeper, limestone aquifer which is isolated from upper alluvial sediments by a thick layer of clay in most of the terrain. The naturally potential hydraulic contact of the two aquifers was additionally maintained by well operation in this part of the source. According to multiple analyses of groundwater flow using a hydrodynamic mathematical model, a hydrogeological and hydraulic system of groundwater flow was defined. Although the wells are situated adjacent to the river, and some well laterals are below the riverbed, most of the groundwater that flows to the wells is partly from the wider zone of the alluvial aquifer, and partly from the deeper aquifer. The initial results of hydrochemical investigations also showed an unexpected, inverse oxic character of the groundwater in these two aquifers.

Microbiological risks of recycling urban stormwater via aquifers

With the release of the Australian Guidelines for Water Recycling: Managed Aquifer Recharge (MAR), aquifers are now being included as a treatment barrier when assessing risk of recycled water systems. A MAR research site recharging urban stormwater in a confined aquifer was used in conjunction with a Quantitative Microbial Risk Assessment to assess the microbial pathogen risk in the recovered water for different end uses. The assessment involved undertaking a detailed assessment of the treatment steps and exposure controls, including the aquifer, to achieve the microbial health-based targets.

Evaluation of groundwater suitability for domestic, irrigational, and industrial purposes: a case study from Thirumanimuttar river basin, Tamilnadu, India

The Thirumanimuttar sub-basin forms an important groundwater province in south India, facing serious deficiency in both quality and quantity of groundwater due to increased demand associated with rapid population explosion, agricultural growth and industrial activities. A total of 194 groundwater samples were collected and 15 water quality parameters were analyzed using standard procedures. Na( + ), Cl( - ), Ca(2 + ), HCO(-)(3), Mg(2 + ) and SO(2-)(4) concentration ions are more dominant in both seasons. The total dissolved solids and electrical conductivity was observed good correlation with Na( + ), Cl( - ), HCO(-)(3), Ca(2 + ), Mg(2 + ), Cl( - ), PO(3-)(4) and NO(-)(3) ions indicating dominance of plagioclase feldspar weathering, anthropogenic input and over drafting of groundwater irrespective of seasons. The Hill-Piper diagram indicates alkaline earths exceed the alkalis, an increase of weak acids was noted during both the seasons. For assessing the groundwater for irrigation suitability parameters like total hardness, sodium adsorption ratio, residual sodium carbonate (RSC), permeability index, and sodium percentage are also calculated. Permanent hardness was noted in higher during both the seasons due to discharge of untreated effluents and ion exchange process. The RSC indicates 56% of the samples are not suitable for irrigation purposes in both seasons, if continuously used will affect the crop yield. From the results, nearly 72% of the samples are not suitable for irrigation.

Evaluation of groundwater quality and its suitability for drinking, domestic, and agricultural uses in the Banana Plain (Mbanga, Njombe, Penja) of the Cameroon Volcanic Line

Groundwater quality of the Banana Plain (Mbanga, Njombe, Penja-Cameroon) was assessed for its suitability for drinking, domestic, and agricultural uses. A total of 67 groundwater samples were collected from open wells, springs, and boreholes. Samples were analyzed for physicochemical properties, major ions, and dissolved silica. In 95% of groundwater samples, calcium is the dominant cation, while sodium dominates in 5% of the samples. Eighty percent of the samples have HCO(3) as major anion, and in 20%, NO(3) is the major anion. Main water types in the study area are CaHCO(3), CaMgHCO(3), CaNaHCO(3), and CaNaNO(3)ClHCO(3). CO(2)-driven weathering of silicate minerals followed by cation exchange seemingly controls largely the concentrations of major ions in the groundwaters of this area. Nitrate, sulfate, and chloride concentrations strongly express the impact of anthropogenic activities (agriculture and domestic activities) on groundwater quality. Sixty-four percent of the waters have nitrate concentrations higher than the drinking water limit. Also limiting groundwater use for potable and domestic purposes are contents of Ca(2+), Mg(2+) and HCO(3) (-) and total hardness (TH) that exceed World Health Organization (WHO) standards. Irrigational suitability of groundwaters in the study area was also evaluated, and results show that all the samples are fit for irrigation. Groundwater quality in the Banana Plain is impeded by natural geology and anthropogenic activities, and proper groundwater management strategies are necessary to protect sustainably this valuable resource.

A potential approach for monitoring drinking water quality from groundwater systems using organic matter fluorescence as an early warning for contamination events

The fluorescence characteristics of natural organic matter in a groundwater based drinking water supply plant were studied with the aim of applying it as a technique to identify contamination of the water supply. Excitation-emission matrices were measured and modeled using parallel factor analysis (PARAFAC) and used to identify which wavelengths provide the optimal signal for monitoring contamination events. The fluorescence was characterized by four components: three humic-like and one amino acid-like. The results revealed that the relative amounts of two of the humic-like components were very stable within the supply plant and distribution net and changed in a predictable fashion depending on which wells were supplying the water. A third humic-like component and an amino acid-like component did not differ between wells. Laboratory contamination experiments with wastewater revealed that combined they could be used as an indicator of microbial contamination. Their fluorescence spectra did not overlap with the other components and therefore the raw broadband fluorescence at the wavelengths specific to their fluorescence could be used to detect contamination. Contamination could be detected at levels equivalent to the addition of 60 μg C/L in drinking water with a TOC concentration of 3.3 mg C/L. The results of this study suggest that these types of drinking water systems, which are vulnerable to microbial contamination due to the lack of disinfectant treatment, can be easily monitored using online organic matter fluorescence as an early warning system to prompt further intensive sampling and appropriate corrective measures.

Natural contamination with arsenic and other trace elements in groundwater of the Central-West region of Chaco, Argentina

This study covered the central agricultural region of the Chaco province, which lacks a permanent river networks. However, during the rainy period there is localized groundwater recharge. About 84 groundwater samples were taken during the period April-December 2007. These groundwater samples were collected from two different depths: 62 samples from shallow wells (4 to 20 m) and 24 samples from deep wells (20 to 100 m). Chemical variables were determined: pH, specific conductance, total dissolved solid, hardness, alkalinity, HCO(3)-, CO(3)(2-), SO(4)(2-), Cl-, NO(3)-, NO(2) -, NH(4)+, F-, As((tot)), Na+, K+, Ca2+, Mg2+, Fe, Cu, Ni, Pb and Zn. The chemical composition of groundwater in the study area is dominantly sodium bicarbonate and sodium chloride bicarbonate, comprising more than 60% (52/86) of shallow and deep groundwater samples. Of the 86 analyzed groundwater samples, 88% exceeded the WHO (World Health Organization) and CAA (Código Alimentario Argentino) standards (10 μg/L) for As (arsenic) and 9% exceeded the WHO standard (1.5 mg/L) for F(-).Groundwater highly contaminated with As (max. 1,073 μg/L) and F- (max. 4.2 mg/L) was found in shallow aquifer. The contaminated groundwater is characterized by high pH (max. 8.9), alkalinity (max. HCO(3)- 1,932 mg/L), SO(4)(2-) (max. 11,862 mg/L), Na(+) (max. 3,158 mg/L), Cl(-) (max. 10,493 mg/L) and electric conductivity greater than 33.3 μS/cm. Other associated elements (Ni, Pb, Cu and Zn) are present in low concentrations, except for Fe that in 32% of samples exceeded the guideline value of 0.3 mg/L suggested by the CAA.

Determination of processes affecting groundwater quality in the coastal aquifer beneath Puri city, India: a multivariate statistical approach

Variability of groundwater quality parameters is linked to various processes such as weathering, organic matter degradation, aerobic respiration, iron reduction, mineral dissolution and precipitation, cation exchange and mixing of salt water with fresh water. Multivariate statistical analyses such as principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied to the standardized data set of eleven groundwater quality parameters (i.e. pH, Ca2+, Mg2+, Na+, K+, Fe3+, alkalinity, NO3-, Cl-, SO4(2-), TDS) collected during the post-monsoon and the summer seasons in order to elicit hydrologic and biogeochemical processes affecting water quality in the unconfined aquifer beneath Puri city in eastern India. The application of PCA resulted in four factors explaining 73% variance in post-monsoon and 81% variance in summer. The HCA using Ward's method and squared Euclidean distance measure classified the parameters into four clusters based on their similarities. PCA and HCA allowed interpretation of processes. During both post-monsoon and summer seasons, anthropogenic pollution and organic matter degradation/Fe(III) reduction were found dominant due to contribution from on-site sanitation in septic tanks and soak pits in the city. Cation exchange and mineral precipitation were possible causes for increase in Na+ and decrease in Ca2+ concentration in summer. Fresh water recharge during monsoon and Sea water intrusion in summer are attributed as significant hydrologic processes to variations of the groundwater quality at the study site.

Appraisal of salinity and fluoride in a semi-arid region of India using statistical and multivariate techniques

Various physico-chemical parameters, including fluoride (F(-)), were analyzed to understand the hydro-geochemistry of an aquifer in a semi-arid region of India. Furthermore, the quality of the shallow and deep aquifer (using tube well and hand pumps) was also investigated for their best ecological use including drinking, domestic, agricultural and other activities. Different multivariate techniques were applied to understand the groundwater chemistry of the aquifer. Findings of the correlation matrix were strengthened by the factor analysis, and this shows that salinity is mainly caused by magnesium salts as compared to calcium salts in the aquifer. The problem of salinization seems mainly compounded by the contamination of the shallow aquifers by the recharging water. High factor loading of total alkalinity and bicarbonates indicates that total alkalinity was mainly due to carbonates and bicarbonates of sodium. The concentration of F(-) was found more in the deep aquifer than the shallow aquifer. Further, only a few groundwater samples lie below the permissible limit of F(-), and this indicates a risk of dental caries in the populace of the study area. The present study indicates that regular monitoring of groundwater is an important step to avoid human health risks and to assess its quality for various ecological purposes.