Radon concentrations in the community groundwater system of South Korea

Groundwater samples were collected from 3818 wells used for the community groundwater system (CGS) in the remote rural areas of South Korea and analyzed to determine radon concentrations. Radon concentrations varied with rock type, ranging from 0.1 to 2393.5 Bq/L with an average of 86.6 Bq/L and a median of 46.4 Bq/L. Among 10 geological units, the median CGS radon concentration was highest (59.6-103.0 Bq/L) in granite, and lower in sedimentary rocks (16.9-21.1 Bq/L) and porous volcanic rocks (17.6 Bq/L), respectively. Of the 3818 samples, 26.1% exceeded the World Health Organization (WHO) radon level limit of 100 Bq/L. The application of the natural radon reduction rate (26.5%) recently suggested by Yun et al. Applied Radiation and Isotopes, 126(1), 23-25 (2017) to the CGS water tank appeared to decrease exceedance of the WHO radon level limit to 20.2%. Because of the high radon concentrations in CGS groundwater in South Korea, the establishment of a radon level limit for drinking water is strongly recommended to ensure the health and safety of the people using CGS water.

Characterizing Flaring from Unconventional Oil and Gas Operations in South Texas Using Satellite Observations

Over the past decade, increases in high-volume hydraulic fracturing for oil and gas extraction in the United States have raised concerns with residents living near wells. Flaring, or the combustion of petroleum products into the open atmosphere, is a common practice associated with oil and gas exploration and production, and has been under-examined as a potential source of exposure. We leveraged data from the Visible Infrared Imaging Spectroradiometer (VIIRS) Nightfire satellite product to characterize the extent of flaring in the Eagle Ford Shale region of south Texas, one of the most productive in the nation. Spatiotemporal hierarchical clustering identified flaring sources, and a regression-based approach combining VIIRS information with reported estimates of vented and flared gas from the Railroad Commission of Texas enabled estimation of flared gas volume at each flare. We identified 43887 distinct oil and gas flares in the study region from 2012 to 2016, with a peak in activity in 2014 and an estimated 4.5 billion cubic meters of total gas volume flared over the study period. A comparison with well permit data indicated the majority of flares were associated with oil-producing (82%) and horizontally drilled (92%) wells. Of the 49 counties in the region, 5 accounted for 71% of the total flaring. Our results suggest flaring may be a significant environmental exposure in parts of this region.

Heavy metal contamination and health risk assessment for children near a large Cu-smelter in central China

Nonferrous metallurgy is causing significant concerns due to its emissions of heavy metals into environment, degrading environmental quality, and consequently posing high risks to human health. In this study, the concentration levels of Cadmium (Cd), Copper (Cu), Lead (Pb), and Arsenic (As) were investigated in soil, crop, well water, and fish samples collected around the Daye Copper Smelter in Hubei province, China, and the potential health risks were assessed for local children. The results showed that soils near the smelter were heavily polluted by Cd, Cu, Pb, and As, with the mean concentrations of 4.87, 195.26, 92.65, and 35.84 mg/kg, respectively, which were significantly higher than the values of soil Cd (0.18 mg/kg), Cu (32.84 mg/kg), Pb (28.46 mg/kg), and As (13.65 mg/kg) in the reference area (p < 0.001). The concentrations of Cd and As in vegetable samples collected from smelter-affected area exceeded the maximum permissible level (MPL) for food in China by 82% and 39%, respectively. The concentrations of Cd and Pb in rice grain harvested from smelter-affected area were 9.35 and 1.35 times higher than the corresponding MPL, respectively. The concentrations of Cd, As, and Cu in fish muscle from smelter-affected area exceeded the national MPL by 72%, 41%, and 24% of analyzed samples, respectively. The concentrations of Cd (p < 0.05) and As (p < 0.01) in well water were significantly higher in the smelter-affected area than those in the reference area, respectively. The health risks to local children in the smelter-affected area were 30.25 times higher than the acceptable level of 1, and most of the risks were resulted from Cd (46%), As (27%) and Pb (20%). The intake of crops was a major source (78%) to health risks for local children.

Characteristics, sources, water quality and health risk assessment of trace elements in river water and well water in the Chinese Loess Plateau

Water resources and water quality are restrictive factors in the Chinese Loess Plateau (CLP), a unique area with most severe soil erosion, fragile ecology and water shortage. River and well water samples were firstly analyzed, and multiple methods and indexes, including principal component analysis (PCA), correlation analysis (CA), sodium adsorption ratio (SAR), water quality index (WQI), hazard quotient (HQ), and hazard index (HI), were used to investigate characteristics, water quality and health risk assessment of trace elements in CLP. The average trace elements concentrations were higher than the world average with a slightly alkaline characteristic. PCA and CA showed that Al, Fe, Li, B, As, and F had natural origins from loess weathering and leaching; Cr, Pb, Cd, Cu, Ag, and Tl were mainly from anthropogenic input; Co, Ni, and Mn were dominated by both anthropogenic and natural sources. The poor river water quality was mainly related with high sodium (alkalinity) and salinity hazard. The poor well water quality samples with high WQI values, especially for As, Cr, and B, were distributed in the northwest and the Fenhe River sub-basin. The pollution level of trace elements in rivers in CLP was in medium level compared with other rivers worldwide. Arsenic pollution was the worst in well water and was the potential pollutant in river water especially for children. Arid climate together with anthropogenic input and special water characteristics (high Na, pH, and low Ca) aggravated As pollution. More work should be done to monitor the secular variation and remove As in the high As areas. The results of this study can provide the basic data for efficient water management and human health protection in CLP.

Prospective Biopsy-Based Study of CKD of Unknown Etiology in Sri Lanka

BACKGROUND AND OBJECTIVES

A kidney disease of unknown cause is common in Sri Lanka's lowland (dry) region. Detailed clinical characterizations of patients with biopsy-proven disease are limited, and there is no current consensus on criteria for a noninvasive diagnosis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We designed a prospective study in a major Sri Lankan hospital servicing endemic areas to ascertain pathologic and clinical characteristics of and assess risk factors for primary tubulointerstitial kidney disease. We used logistic regression to determine whether common clinical characteristics could be used to predict the presence of primary tubulointerstitial kidney disease on kidney biopsy.

RESULTS

From 600 new patients presenting to a tertiary nephrology clinic over the course of 1 year, 87 underwent kidney biopsy, and 43 (49%) had a biopsy diagnosis of primary tubulointerstitial kidney disease. On detailed biopsy review, 13 (30%) had evidence of moderate to severe active kidney disease, and six (15%) had evidence of moderate to severe chronic tubulointerstitial kidney disease. Patients with tubulointerstitial kidney disease were exclusively born in endemic provinces; 91% spent a majority of their lifespan there. They were more likely men and farmers (risk ratio, 2.0; 95% confidence interval, 1.2 to 2.9), and they were more likely to have used tobacco (risk ratio, 1.7; 95% confidence interval, 1.0 to 2.3) and well water (risk ratio, 1.5; 95% confidence interval, 1.1 to 2.0). Three clinical characteristics-age, urine dipstick for protein, and serum albumin-could predict likelihood of tubulointerstitial kidney disease on biopsy (model sensitivity of 79% and specificity of 84%). Patients referred for kidney biopsy despite comorbid diabetes or hypertension did not experience lower odds of tubulointerstitial kidney disease.

CONCLUSIONS

A primary tubulointerstitial kidney disease occurs commonly in specific regions of Sri Lanka with characteristic environmental and lifestyle exposures.

Modeling fate and transport of hydraulic fracturing fluid in the presence of abandoned wells

Hydraulic fracturing in shale/tight gas reservoirs creates fracture network systems that can intersect pre-existing subsurface flow pathways, e.g. fractures, faults or abandoned wells. This way, hydraulic fracturing operations could pose environmental risks to shallow groundwater systems. This paper explores the long-term (> 30 years) flow and transport of fracturing fluids into overburden layers and groundwater aquifers through a leaky abandoned well, using the geological setting of North German Basin as a case study. A three-dimensional model consisting of 15 sedimentary layers with three hydrostratigraphic units representing the hydrocarbon reservoir, overburden, and the aquifer is built. The model considers one perforation location at the first section of the horizontal part of the well, and a discrete hydraulic fracture intersecting an abandoned well. A sensitivity analysis is carried out to quantify and understand the influence of a broad spectrum of field possibilities (reservoir properties, overburden properties, abandoned well properties and its proximity to hydraulic fractures) on the flow of fracturing fluid to shallower permeable strata. The model results suggest the spatial properties of the abandoned well as well as its distance from the hydraulic fracture are the most important factors influencing the vertical flow of fracturing fluid. It is observed that even for various field set-tings, only a limited amount of fracturing fluid can reach the aquifer in a long-term period.

Arsenic exposure and young adult's mortality risk: A 13-year follow-up study in Matlab, Bangladesh

BACKGROUND

Widespread arsenic contamination in underground water is a well-documented public health concern that threatens millions of lives worldwide. We investigated the risk of young-adult mortality due to high chronic exposure to arsenic through years of drinking arsenic contaminated water.

METHODS

A prospective cohort study of 58,406 individuals was enrolled who were 4-18 years at baseline. Since Matlab HDSS (Health and Demographic Surveillance System) has an active surveillance system, all individuals were included in the follow up. Each individual's arsenic exposure was calculated at (1) baseline As level as current exposure (2) time-weighted lifetime (average or lifetime average) and (3) cumulative arsenic exposure. Age, sex, educational attainment and SES were adjusted during the analysis. In this 13 years closed-cohort study (2003-2015), all young-adult deaths were captured through verbal autopsy (VA) using International Classification of Diseases (ICD-10) to define the causes.

RESULTS

Although, girls had higher values of cumulative arsenic exposure via tube well water than boys (median: 1858.5 μg/year/L vs. 1798.8 μg/year/L) but higher mortality due to cancers and due to cerebro-vascular disease, cardio-vascular disease, and respiratory disease (7.0 vs. 5.7 per 100,000 person-years and 6.4 vs. 4.2 per 100,000 person-years respectively). Higher risk of deaths among young adults (Adjusted HR: 2.7, 1.3-5.8) due to all cancers among those who were exposed to As > 138.7 compared to As ≤ 1.1 μg/L. For cerebro-vascular disease, cardio-vascular disease, and respiratory disease deaths, average arsenic in well water (>223.1 μg/L vs. ≤90.9 μg/L) and cumulative arsenic in well water (>2711.0 μg/year/L vs. ≤1013.3 μg/year/L) had 4.8 (1.8-12.8) and 5.1 (1.7-15.1) times higher risks of mortality than to those lowest exposed.

CONCLUSION

Higher concentration of, and chronic exposure to arsenic in drinking water, increases the mortality risk among the young adults, regardless of gender.

The role of gut microbiome and its interaction with arsenic exposure in carotid intima-media thickness in a Bangladesh population

BACKGROUND

Emerging data suggest that inorganic arsenic exposure and gut microbiome are associated with the risk of cardiovascular disease. The gut microbiome may modify disease risk associated with arsenic exposure. Our aim was to examine the inter-relationships between arsenic exposure, the gut microbiome, and carotid intima-media thickness (IMT)-a surrogate marker for atherosclerosis.

METHODS

We recruited 250 participants from the Health Effects of Arsenic Longitudinal Study in Bangladesh, measured IMT and collected fecal samples in year 2015-2016. 16S rRNA gene sequencing was conducted on microbial DNA extracted from the fecal samples. Arsenic exposure was measured using data on arsenic concentration in drinking water wells over time to derive a time-weighted water arsenic index. Multivariable linear regression models were used to test the inter-relationships between arsenic exposure, relative abundance of selected bacterial taxa from phylum to genus levels, and IMT.

RESULTS

We identified nominally significant associations between arsenic exposure, measured using either time-weighted water arsenic or urinary arsenic, and the relative abundances of several bacterial taxa from the phylum Tenericutes, Proteobacteria, and Firmicutes. However, none of the associations retained significance after correction for multiple testing. The relative abundances of the family Aeromonadaceae and genus Citrobacter were significantly associated with IMT after correction for multiple testing (P-value = 0.02 and 0.03, respectively). Every 1% increase in the relative abundance of Aeromonadaceae and Citrobacter was related to an 18.2-μm (95% CI: 7.8, 28.5) and 97.3-μm (95% CI: 42.3, 152.3) difference in IMT, respectively. These two taxa were also the only selected family and genus using the LASSO variable selection method. There was a significant interaction between Citrobacter and time-weighted water arsenic in IMT (P for interaction = 0.04).

CONCLUSIONS

Our findings suggest a role of Citrobacter in the development of atherosclerosis, especially among individuals with higher levels of arsenic exposure.

Maternal swimming pool exposure during pregnancy in relation to birth outcomes and cord blood DNA methylation among private well users

Swimming in pools during pregnancy may expose the fetus to water disinfection by-products (DBP). As yet, our understanding of the impacts on DBPs on the fetus is uncertain. Individuals with public water systems are typically exposed to DBPs through drinking, showering and bathing, whereas among those on private water systems, swimming in pools may be the primary exposure source. We analyzed the effects of maternal swimming on birth outcomes and cord blood epigenetic changes in the New Hampshire Birth Cohort Study, a cohort of pregnant women with households on private water systems. Information about swimming in pools during pregnancy was obtained from 1033 women via questionnaires. Swimming pool use and duration were modeled using linear regression with newborn weight, length, and head circumference (z-scores) and genome wide cord blood DNA methylation as the outcomes and with adjustment for potential confounders. Overall 19.7% of women reported swimming in a pool during pregnancy. Among swimmers, duration of swimming was inversely related to head circumference (-0.02 z-score per 10% increase in duration, P = 0.004). No associations were observed with birth weight, length or DNA methylation modifications. Our findings suggest swimming pool exposure may impact the developing fetus although longer-term studies are needed.

Enhanced distribution of humic acid-modified nanoscale magnesia for in situ reactive zone removal of Cd from simulated groundwater

Efficient injection and distribution of nanoparticles in porous media are considered a formidable technical hurdle for injection-based in situ remediation. One approach to enhance the mobility of nanoparticles in an aquifer is to use surface modifiers. In this study, nanoscale magnesia (NMgOs), an innovative and effective remedial material for cadmium (Cd) removal from groundwater, was modified with the negatively charged and eco-friendly humic acid to enhance its mobility in aquifers. A two-dimensional reactor (60 × 50 × 10 cm), with 2 injection wells and 30 monitoring wells was designed, constructed, and sand-packed in the laboratory to simulate a saturated aquifer. The simulated aquifer was pre-contaminated with Cd to simulate a plume in groundwater. The distribution of injected unmodified NMgOs and humic acid-modified NMgOs slurry were evaluated in the reactor. The radius of influence (ROI) of humic acid-modified NMgOs was estimated to be approximately 5 cm based on visual observation, while no ROI was apparent for the unmodified NMgOs because of their aggregation at the bottom of the injection wells. The concentrations of Cd and magnesium (Mg) were monitored in all 30 monitoring wells at different time intervals to evaluate the effectiveness of Cd removal. The breakthrough curve analysis revealed that humic acid enhances the transport of NMgOs in the saturated porous media. Furthermore, the results of scanning electron microscopy-energy dispersive x-ray (SEM-EDX) characterization of silica sand before and after injection of NMgOs verified the presence of 5.78% of Mg from humic acid-modified NMgOs and 0.19% from unmodified NMgOs at 35 cm downgradient of the injection wells, which are consistent with the conclusion drawn from the breakthrough curves.

A Case Study of Natural Attenuation of Chlorinated Solvents Under Unstable Groundwater Conditions in Takahata, Japan

The natural attenuation behavior of chlorinated solvents and their risks to human health at a contaminated groundwater site in Takahata, Japan, were investigated. It was found that volatile organic compound (VOC) concentrations gradually decreased via two attenuation mechanisms, namely dilution and biodegradation. It was estimated that the VOC concentrations will be below the Japanese limits within 30 years after stopping the active remediation in 2003, which suggests that there is a high possibility that monitored natural attenuation can be adopted as the clean-up method at this contaminated site. The risk levels of VOCs at the present time are much lower than those at the time when the contamination was discovered. Vinyl chloride still presents a risk in some wells, and there were occasional unexpected increases in the risk levels of tetrachloroethylene, trichloroethylene, and cis-1,2-dichloloethylene, which means that continuous monitoring of the groundwater is necessary for forecasting risk levels.

Complex hydrochemical characteristics of the Middle-Upper Pleistocene aquifer in Soc Trang Province, Southern Vietnam

Environmental isotope techniques were applied to study the hydrochemical characteristics of groundwater in Soc Trang Province, Southern Vietnam, in frame of the project Improvement of Groundwater Protection in Vietnam (IGPVN). Groundwater samples were collected from various monitoring wells (newly drilled by the IGPVN project), national monitoring wells, private tube wells and production wells. Surface water samples were collected from rivers, ponds or canals. The aquifer system is more complex than presumed as the hydrochemical and stable isotope compositions of groundwater samples in the Middle-Upper Pleistocene (qp_2-3) aquifer differ significantly in lateral direction. Furthermore, observed changing redox reactions within the target aquifer from dry to wet season make it probable that some interaction with overlying aquifers exists. The stable isotope signatures of the qp_2-3 groundwater samples can be divided into two distinct groups which, respectively, originated from paleo-meteoric water and either was located in paleo-salinized areas of the qp_2-3 aquifer or resulted from evaporation effect of recharging water prior or during infiltration process. In fact, individual parts of "the same" aquifer seem not to be hydraulically connected to each other. The environmental isotope data provided neither evidences of hydraulic connection between the rivers and the qp_2-3 aquifer nor of recent groundwater recharge in the Province. As a result, saltwater from the sea intruded inland to some extent via the Hau River during the dry season, but it did not affect the target aquifer. Any recharge from surface water to the qp_2-3 aquifer in Soc Trang should occur outside the boundaries of Soc Trang Province. Considering the low groundwater transit velocities roughly estimated in this study (3.6 m/year and 7.8 m/year), it may take several ten thousands to hundred thousands of years for recharging water from beyond the Vietnam's national border to reach the qp_2-3 aquifer in Soc Trang Province. Consequently, natural recharge cannot help to reduce groundwater declining in the short-to-middle term.

Heavy Metal Concentrations in the Groundwater of the Barcellona-Milazzo Plain (Italy): Contributions from Geogenic and Anthropogenic Sources

We collected and analysed 58 samples of groundwater from wells in the Barcellona-Milazzo Plain, one of the most important coastal aquifers of Sicily (Italy), to determine major, minor, and trace element concentrations. In this area, geogenic and anthropogenic sources of heavy metals and other pollutants co-act, making the individuation of the main pollution sources difficult. Our work was aimed at the application of geostatistical criteria for discriminating between these pollution sources. We used probability plots for separating anomalous values from background concentrations, which were plotted on maps and related to possible sources of pollutants. Our results indicate that hydrothermal fluid circulation and the water–rock interaction of country rocks that host mineralized ore deposits generate a significant flux of heavy metals to groundwater, as well as anthropogenic sources like intense agriculture and industrial activities. In particular, NO₃, F, and Ni exceed the Maximum Admitted Concentrations (MACs) established by the WHO and Italian legislation for drinking-water. The spatial distributions of geogenic and anthropogenic sources were so deeply interlocked that their separation was not easy, also employing geostatistical tools. This complex scenario makes the implementation of human health risk mitigation actions difficult, since the flow of pollutants is in many cases controlled by simple water–rock interaction processes.

An assessment of the replicability of a standard and modified sanitary risk protocol for groundwater sources in Greater Accra

Sanitary risk inspection, the systematic observation of contamination hazards, is often used to manage safety of water sources such as wells and boreholes. However, the replicability of sanitary risk inspections undertaken by different observers has not been studied. This study aimed to assess the replicability of sanitary risk inspections by two different observers in urban and peri-urban neighbourhoods of Greater Accra, Ghana. Two observers independently used a standard protocol to record contamination hazards around 62 groundwater sources, additionally recording urban-specific hazards such as damaged sewage pipes via a modified protocol. We calculated risk scores as the proportion of hazards observed at each source, separately for each observer. Linn's concordance correlation coefficient indicated very high agreement between the two observers' risk scores (n = 62; c = 0.949, 95% confidence limits 0.917-0.968). However, risk scores from urban-specific observations were uncorrelated with those from the standard protocol (r = 0.11, p = 0.41 for observer 1; r = 0.16, p = 0.22 for observer 2). Ours is the first study of replicability of sanitary risk observations and suggests high inter-observer agreement. However, urban contamination hazards were not captured using the standard protocol. In the future, assessment of inter-observer agreement and observations of urban-specific hazards could be incorporated into nationwide or regional sanitary risk surveys.

Applying multivariate statistics for identification of groundwater resources and qualities in NW Turkey

This study, performed in Çanakkale-Ezine in NW of Turkey, analyzes the physicochemical properties of 37 groundwater wells. These 37 wells were chosen to represent each geological unit in the study area. The main purpose of the study and its contribution to the literature is to produce information about the resources and availability of groundwater by using multivariate statistical methods and lithology. For determination hydrochemical facies of groundwater, Piper trilinear diagram was used. Gibbs diagram was applied for determining the mechanism of groundwater chemistry and diagram showed that the interaction of rock-water is more dominant in the study area. Multivariate statistics were applied to physicochemical properties for identification origins of waters. According to the Piper diagram, 16 of the wells were identified as Ca-HCO₃ type, 13 of them as Ca-Cl type, 5 of them as mixed Ca-Mg-Cl type, 2 of them as Na-Cl type, and 1 as Ca-Na-HCO₃ type. In the study with the purpose of determining the resources of groundwater, the physicochemical properties of the wells are analyzed with hierarchical cluster (HCA) and non-hierarchical cluster (K-means) methods, and the resources are associated with the lithology based on these methods. A total of 37 wells are divided into five different clusters through the HCA method. Further, for the interpretation of the resources of the groundwater, the facies of the waters on the Piper diagram are evaluated based on the five clusters generated through the HCA method and on the lithology. In the study, the results obtained from the K-means method are not significant and in line with the lithology for the interpretation of the resources of the groundwater. In conclusion, this study with limited dataset reveals that using HCA method is very effective to identify the origins of groundwater and present the association with lithology.

Estimating bioaugmentation efficacy of TCE dechlorination using long-term field well-to-well tests in a highly recharged and TCE-contaminated aquifer

This study demonstrates a combined field method accurately assessing the extent of trichloroethylene (TCE) reductive dechlorination activity and the mass fraction of its by-products. A combined method of injecting a known concentration of 1,1,2-trichloro-2-fluoroethene (TCFE) as a TCE bio-surrogate and a data processing technique of forced mass balance (FMB), considering the sorption effect on the mass fraction of chloroethene was evaluated by performing soil column and field bioaugmentation tests. In the soil column test, the FMB resulted in the mass fraction of 6% TCE, 48.3% cis-1,2-dichloroethene, 18.5% vinyl chloride and 27.2% ethylene. In the field bioaugmentation test, TCFE showed equivalent dechlorination pathways of TCE. The mass fractions estimated by FMB were very similar to those observed in the soil column bioaugmentation tests: 4.5% TCFE, 57.1% 1,2-dichloro-1-fluoroethene, 12% 1-chloro-1-fluoroethene and 26.4% fluoroethene (FE). The FMB method gave ∼50% higher mass fraction for more chlorinated ethenes (i.e., TCFE) and ∼10% lower mass fraction of less chlorinated ethenes (i.e., FE) than those considering only the aqueous concentrations of chlorofluoroethenes. A combined method of TCFE and FMB that could accurately estimate both the extent of dechlorination activities and mass distribution of TCE reductive dechlorination would be highly useful.

Impact of on-site sanitation systems on groundwater sources in a coastal aquifer in Chennai, India

On-site sanitation is the most preferred mode of sanitation due to expensive off-site sanitation. The increasing population especially in the peri-urban areas has led to increasing use of on-site sanitation systems in India. However, the habitations in the vicinity of these systems do not have centralised water supply and are dependent on groundwater sources. However, there is concern about leaching of faecal coliforms and nitrate from the septic tanks to the underlying aquifer. The present study is attempted at two sites in the coastal city of Chennai where on-site sanitation is prevailing. The sample locations (16 nos.) are selected in such a way that groundwater sources are situated in the vicinity of on-site sanitation systems. The groundwater sources are the bore wells installed by the private agencies. It is observed that parameters considered key parameters to study the impact of the on-site sanitation systems, namely Na2⁺, Cl^-, NO₃^-, faecal coliform and total dissolved solids, exceed the concentration limits recommended by the Bureau of Indian Standards. The piper diagram analysis identifies that the predominant cations and anions are respectively Na⁺, and Cl^-, SO₄^- and HCO₃^-.The Gibbs plot shows ground water quality is dominated by the evaporation process in both the seasons. The Cl/HCO₃ ratio in many samples confirms the seawater intrusion in the study area. Elevated concentrations of faecal coliforms in all the samples (16 nos.) confirm the significant amount of groundwater pollution from the on-site sanitation systems. It is desired that policy planners and implementation agencies should undertake detailed scientific and hydrogeological studies of the region in order to examine the feasibility of implementing on-site sanitation systems.

Arsenic in groundwater in private wells in rural North Dakota and South Dakota: Water quality assessment for an intervention trial

Elevated exposure to arsenic disproportionately affects populations relying on private well water in the United States (US). This includes many American Indian (AI) communities where naturally occurring arsenic is often above 10 µg/L, the current US Environmental Protection Agency safety standard. The Strong Heart Water Study is a randomized controlled trial aiming to reduce arsenic exposure to private well water users in AI communities in North Dakota and South Dakota. In preparation for this intervention, 371 households were included in a community water arsenic testing program to identify households with arsenic ≥10 µg/L by inductively coupled plasma mass spectrometry (ICP-MS). Arsenic ≥10 µg/L was found in 97/371 (26.1%) households; median water arsenic concentration was 6.3 µg/L, ranging from <1-198 µg/L. Silica was identified as a water quality parameter that could impact the efficacy of arsenic removal devices to be installed. A low-range field rapid arsenic testing kit evaluated in a small number of households was found to have low accuracy; therefore, not an option for the screening of affected households in this setting. In a pilot study of the effectiveness of a point-of-use adsorptive media water filtration device for arsenic removal, all devices installed removed arsenic below 1 µg/L at both installation and 9 months post-installation. This study identified a relatively high burden of arsenic in AI study communities as well as an effective water filtration device to reduce arsenic in these communities. The long-term efficacy of a community based arsenic mitigation program in reducing arsenic exposure and preventing arsenic related disease is being tested as part of the Strong Heart Water Study.

Emerging contaminants and nutrients in a saline aquifer of a complex environment

The quality and availability of water has become a pressing issue worldwide, being particularly important in semi-arid regions, where climate change has aggravated the problem. The use of anthropogenic chemicals, classified as emerging pollutants, adds to the problem representing a treat, since they are not regulated and have a potential impact on human and environmental health. This pressing problem has not been studied widely in complex environments like the one we present here. Distribution and seasonal variability of fecal sterols, alkylphenols, pesticides (emerging pollutants) and nutrients were determined in 35 wells used for agriculture and human consumption in the Valley of Maneadero, located in the semi-arid region of Baja California, Mexico. The presence of the tested pollutants in the saline aquifer was heterogeneous, showing important differences in concentration and distribution. Wells destined for household use showed the highest variability. In these wells, anthropogenic fecal sterols were detected and, alkylphenols, such as octyphenol and nonylphenol had maximum concentrations (2.7 ng/mL). In agriculture and urban wells, we identified DDT and organochlorine pesticides, as well as myclobutanil, which is considered a modern pesticide. Nitrates were identified in concentrations above international standards, mainly during the dry season, in both the agricultural and urban areas. As emerging pollutants represent a negative effect on environmental and human health, this is the first paper showing the importance of measuring this type of pollutant in agricultural/semi-urban areas, especially in aquifers that have been overexploited and communities that have relied on the use of septic tanks for decades.

Evaluation of sources and fate of nitrates in the western Po plain groundwater (Italy) using nitrogen and boron isotopes

Diffuse nitrate pollution in groundwater is currently considered one of the major causes of water quality degradation. Determining the sources of nitrate contamination is an important first step for a better management of water quality. Thus, the isotopic composition of nitrate (δ¹⁵N_NO3 and δ¹⁸O_NO3) and boron (δ¹¹B) were used to evaluate nitrate contamination sources and to identify geochemical processes occurring in the shallow and deep aquifers of the Turin-Cuneo plain (NW Italy). The study area is essentially an agricultural zone, where use of synthetic nitrogenous fertilizers and organic manure is a common practice and the connection to sewer services is locally lacking. Also livestock farming are highly developed. A groundwater sampling campaign was performed on 34 wells in the shallow aquifer and 8 wells in the deep aquifers, to analyze nitrate, chloride, boron, δ¹⁵N_NO3, δ¹⁸O_NO3 and δ¹¹B. Isotope data of nitrate indicate that nitrate contamination in the Turin-Cuneo plain originates from mixtures of synthetic and organic sources, slightly affected by denitrification, and manure or septic tank effluents. Moreover, boron isotopes were used to discriminate further among the main anthropogenic sources of pollution. The analyses results confirm that both animal manure and domestic sewage, especially under the city of Turin, can contribute to the nitrate contamination. The isotope analysis was also used for the evaluation of denitrification and nitrification processes: contrary to expectations, a significant denitrification phenomenon was assessed only in the shallow unconfined aquifer, especially in the Poirino Plateau, the most contaminated sector of the study area.

Evaluating a chemical source-tracing suite for septic system nitrate in household wells

Reducing human and ecological risks of groundwater nitrate contamination requires understanding the source of nitrate. Land use practices, such as agriculture and residential development, can increase groundwater nitrate concentrations. This study evaluated a chemical source-tracing suite that paired analysis of agricultural herbicide metabolites and human wastewater constituents. The source-tracing suite was tested in an area subject to nitrate from both agriculture and on-site waste ("septic") systems. Monitoring wells showed that agricultural contamination was deeper (>5 m) in the aquifer consistent with its origin a greater distance from wells and that on-site waste ("septic system") contamination was shallower in the aquifer (<3 m). Repeated sampling of seventeen household wells showed evidence of both agricultural and on-site waste contamination in wells with higher nitrate concentrations. The artificial sweeteners sucralose and acesulfame and the antibiotic sulfamethoxazole were the only septic system indicators consistently detected. Less persistent compounds, such as caffeine and acetaminophen, were never detected in the household wells indicating they were attenuated over the distance between septic system and well and reducing their utility as a tracer of septic system nitrate. Overall, there was a positive relationship between sucralose, acesulfame and nitrate in wells with low levels of agricultural contamination although the relationship varied between wells.

Impact of Road Salt on Drinking Water Quality and Infrastructure Corrosion in Private Wells

Increased road salt use and resulting source water contamination has widespread implications for corrosion of drinking water infrastructure, including chloride acceleration of galvanic corrosion and other premature plumbing failures. In this study, we utilized citizen science sampling, bench-scale corrosion studies, and state-level spatial modeling to examine the potential extent of chloride concentrations in groundwater and the resulting impact on private wells in New York. Across the sampled community, chloride levels varied spatially, with the highest levels in private wells downgradient of a road salt storage facility followed by wells within 30 m of a major roadway. Most well users surveyed (70%) had stopped drinking their well water for aesthetic and safety reasons. In the bench-scale experiment, increasing chloride concentration in water increased galvanic corrosion and dezincification of plumbing materials, resulting in increased metal leaching and pipe wall thinning. Our simple spatial analysis suggests that 2% of private well users in New York could potentially be impacted by road salt storage facilities and 24% could potentially be impacted by road salt application. Our research underscores the need to include the damage to public and privately owned drinking water infrastructure in future discussion of road salt management.

Uranium in groundwater - The importance of hydraulic regime and groundwater flow system's understanding

Uranium and other natural radionuclides are common components in groundwater, but they are not routinely measured. In drinking water their total activity is screened, but in the evaluation of the measured values usually the aquifer material is only considered. However, the occurrence of radionuclides in groundwater is strongly affected by flow systems and their geochemical characteristics. Therefore hydrogeology and flow system's evaluation is crucial to understand natural radioactivity. Areas of different hydraulic regimes - recharge, throughflow and discharge - even within the same aquifer are characterized by different geochemical environment. In the present study pressure-elevation profiles were generated based on existing basic hydraulic data of wells in order to determine the flow regimes and associated vertical groundwater flow directions. 24-753 mBq L^-1 uranium activity concentrations were found in groundwater and surface water showing great areal variability. High uranium values correspond to recharge regimes with downward flow directions. Uranium mobility is enhanced by high bicarbonate content and circumneutral pH. The study emphasize the importance of groundwater flow system's understanding in those areas, where elevated background radioactivity may exist.

Impact of receipt of private well arsenic test results on maternal use of contaminated drinking water in a U.S. population

Exposure to inorganic arsenic in drinking water has known cancer and non-cancer health effects. However, no prior studies have addressed response to well water testing for arsenic during pregnancy, a time of known heightened risk perception. Using a US pregnancy cohort, we assessed the impact of receiving well water arsenic test results on subsequent use of arsenic-contaminated tap water. Study participants were 24-28 weeks' gestation at study entry and reported living in a residence served by a private, unregulated well. Upon enrollment participants provided a tap water sample which was tested for arsenic using ICP-MS. During pregnancy and every four months after, participants were asked their extent of tap water use for drinking, cooking and mixing infant formula. Logistic regression was used to estimate the odds of tap water use at one year post-partum in relation to baseline tap water use and arsenic concentration. Compared to those who used tap water <50% of the time, mothers who reported using tap water for drinking and cooking >50% of time in their prenatal questionnaire had 8.54 times the odds of using their tap water at 1-year postpartum (95% CI: 5.37, 13.60). After adjusting for frequency of prenatal tap water use, mothers were less likely to use tap water for drinking and cooking (OR = 0.34, 95% CI: 0.19, 0.60) and for mixing formula (OR = 0.45, 95% CI: 0.24, 0.86) if the high arsenic concentration (>10 μg/L) was known to them. Our findings suggest that providing well water test results during pregnancy may reduce subsequent maternal use of iAs contaminated tap water for drinking, cooking, and mixing infant formula. Public health implications are discussed.

Groundwater Quality and Hydraulic Fracturing: Current Understanding and Science Needs

Hydraulic fracturing (fracking) is a process used for the stimulation and production of ultra-low permeability shale gas and tight oil resources. Fracking poses two main risks to groundwater quality: (1) stray gas migration and (2) potential contamination from chemical and fluid spills. Risk assessment is complicated by the lack of predrilling baseline measurements, limited access to well sites and industry data, the constant introduction of new chemical additives to frack fluids, and difficulties comparing data sets obtained by different sampling and analytical methods. Specific recommendations to reduce uncertainties and meet science needs for better assessment of groundwater risks include improving data-sharing among researchers, adopting standardized methodologies, collecting predrilling baseline data, installing dedicated monitoring wells, developing shale-specific environmental indicators, and providing greater access to field sites, samples, and industry data to the research community.