Potable Groundwaters Research Articles

Potential impact of leaking CO2 gas and CO2-rich fluids on shallow groundwater quality in the Chungcheong region (South Korea): A hydrogeochemical approach

This study evaluates the potential impact of leaking CO2 gas and CO2-rich waters on shallow groundwater quality by focusing on the mobilization of trace elements. For this study, Group I (acidic CO2-rich waters with low TDS), Group II (slightly acidic CO2-rich waters with high TDS), and Group III (CO2-poor waters with low TDS) were sampled in the study area occurring naturally CO2-rich waters. The carbon isotope data (δ13C and 14C) indicate that the dissolved CO2 in CO2-rich water originates from old and deep-seated CO2. Our results show that Group I is formed by the direct input of CO2 gas into recently recharged shallow groundwater, whereas Group II discharging along fractures or wells occurs by long-term CO2-water-rock interactions in the subsurface. Group I shows higher concentrations of trace elements (Al, Ba, Be, Cr, Cs, Fe, Mn, Ni, Rb, and U) than Group III, and its Al and Mn concentrations slightly exceed the US EPA drinking water standard. However, Group II has significantly higher concentrations of trace elements than Group I. In particular, harmful Be exceeds the US EPA drinking water standard by over 6.5-fold. In addition, Fe and Mn exceed the US EPA drinking water standard by 27.7-fold and 16.1-fold, respectively. The higher concentration of bicarbonate by pH buffering in Group II also increases the mobilization of U6+. Our results show that the mobilization of trace elements in the aquifer having little buffering capacity is mainly determined by the degree of CO2-water-rock interactions. This study indicates that upwelling of deep CO2-rich fluids with long-term water-rock interactions can be harmful to shallow potable groundwaters by supplying high levels of trace elements into shallow aquifers.

Measuring Aqueous CH4 Concentration Profiles in Shales and Tills to Define Source, Transport, and Fate of Organic Gases

The rapid development of unconventional shale resource plays has generated public concern with respect to potential contamination of potable groundwaters and surface waters by fugitive natural gases dominated by methane (CH4). Continuous core samples collected at six drill sites to a maximum depth of 240 m below ground were used to define the vertical distribution of dissolved CH4 and conservative Cl− through Cretaceous shales and overlying glacial tills in the Williston Basin, Canada. The interpretation of potentially reactive CH4 depth profiles in conjunction with conservative profiles provide insights into the source, transport, and fate of CH4 in aquitards-aquifer sequences and present baseline gas concentrations for use in fugitive gas migration investigations.

Assessment of Baseline Groundwater Physical and Geochemical Properties for the Quest Carbon Capture and Storage Project, Alberta, Canada

Abstract The Shell Quest Carbon Capture and Storage (CCS) project will capture CO2 from the Scotford Upgrader Facility in Fort Saskatchewan, Alberta, Canada, and inject approximately 1 million tonnes of CO2 per annum over 25 years into the Basal Cambrian Sandstone aquifer. An MMV program has been designed and is being implemented. A key MMV component is the ongoing hydrological and geochemical monitoring of a number of groundwater wells. As part of the MMV process, this project has re-evaluated the shallow geology in the study area where necessary, and based upon this, defined four aquifers including the Surficial, Oldman, Foremost and Basal Belly River Sandstone (BBRS). Historic and ongoing groundwater monitoring data has been used to develop a hydrologic and geochemical baseline for the four target aquifers. Inferred regional groundwater flow directions and velocities have been calculated based upon the available hydraulic head, well pump test data and aquifer properties. Groundwaters from the Surficial, Oldman and Foremost aquifers cannot be separated based upon hydraulic head or upon aqueous chemistry. However, groundwater data from the BBRS aquifer suggests that the BBRS aquifer is hydraulically isolated from the overlying aquifers within the limits of the Quest Project Sequestration Lease Area (SQL). Based on the geochemical baseline, groundwater related solution chemical triggers are being defined which may be used to identity whether or not fluid and/or gas migration is occurring from the storage complex and, if that is the case, what impact those fluids and/or gas may have upon the potable groundwaters above the Base of Groundwater Protection (BGWP) across the SQL.

Gestão das águas minerais no Brasil: panorama legal atual e perspectivas futuras

As águas minerais no Brasil são tratadas juridicamente como recursos minerais, possuem legislação própria (Código de Águas Minerais de 1945) e seguem os fundamentos e instrumentos de outorga de direitos da legislação que regulamenta a atividade de mineração no país. Estes princípios conflitam com a própria Constituição Federal de 1988, que delegou o domínio das águas subterrâneas aos Estados. Além disso, a legislação ambiental e de recursos hídricos, promulgadas a partir da década de 1980, introduziram uma dimensão ambiental às águas como um todo, incluindo os recursos hídricos subterrâneos, definindo-as como bens de domínio público e de uso comum do povo, de caráter não dominial e inalienável. As águas minerais foram legalmente definidas na década de 1940 como águas subterrâneas naturalmente potáveis, protegidas da contaminação superficial, de composição química regularmente definida e presumível ação medicamentosa. Alguns conceitos originais da legislação de águas minerais foram profundamente modificados com o tempo, principalmente no que se refere ao estudo da ação terapêutica destas águas e seu uso em balneários e estâncias hidrotermais. Atualmente o aproveitamento econômico das águas minerais é primordialmente voltado à produção de bebidas engarrafadas e as características químicas e físico-químicas da maior parte de suas fontes revelam que hoje as águas minerais pouco se diferenciam das águas subterrâneas de composição ordinária. No momento político atual, em que se discute a mudança do marco legal da mineração no país, é desejável retomar a discussão, em nível governamental, para atualizar a lei das águas minerais, levando em consideração os conhecimentos modernos de hidrogeologia, química e medicina, assim como os fundamentos de proteção do meio ambiente e de desenvolvimento sustentável introduzidos pela Constituição. Defende-se aqui um debate franco, aberto e democrático, que conte com a participação dos diversos setores da sociedade com interesses conflitantes no uso de recursos hídricos subterrâneos.

Identification of thermodynamic controls defining the concentrations of hazardous elements in potable ground waters and the potential impact of increasing carbon dioxide partial pressure

Abstract Concern has been expressed that carbon dioxide leaking from deep storage reservoirs could adversely impact water quality in overlying potable aquifers by mobilizing hazardous elements present in the aquifer rocks to the extent that their concentrations might exceed Maximum Contaminant Levels (MCLs). To evaluate this issue, 38,000 ground water quality analyses from aquifers throughout the United States, each containing one or more analyses for As, Ba, Cd, Hg, Pb, Sb, Se, U or Zn, were retrieved from the Unites States National Water Information System (NWIS). The analyses were used to calculate the saturation indices (SIs) of all identified and thermodynamically characterized minerals containing the listed elements as essential components. These minerals were initially selected through literature surveys to establish whether field evidence supported their postulated presence in potable water aquifers. SI frequency histograms were plotted to evaluate whether these minerals are at saturation in NWIS ground waters (i.e., they show modes at SI 0). Mineral assemblages meeting the criterion of thermodynamic saturation were assumed to control the aqueous concentrations of the hazardous elements at initial system state as well as at elevated CO 2 partial pressure caused by the ingress of leaking CO 2 . The impact on the identified mineral solubilities of increasing CO 2 partial pressures was then predicted over the range from −4 to +1 (i.e., 10 −4 ≤P(CO 2 ) in bar ≤10). Under reducing conditions (characteristic of most ground waters), the most serious problem resulting from intrusion of CO 2 into shallow groundwater may arise through enhanced dissolution of pyrite and solubilization of arsenic. At the highest P(CO 2 ) assumed in our study, Ba, Pb and Zn may also approach or exceed regulatory concentration limits. Of the remaining elements, the MCLs of Cd, and Sb are unlikely to be exceeded, and Hg, Se and U concentrations are unaffected by CO 2 intrusion.

Contrasting occurrence of Chromobacterium violaceum in tropical drinking water springs of Uganda

Occurrence of Chromobacterium violaceum in six protected drinking water springs in Uganda was investigated. C. violaceum showed a contrasting occurrence, which was independent of human impact as assessed by faecal pollution indicators. It was isolated from two springs (S1 and S2) that were located close to each other (3 km) but not in the rest. In S1 C. violaceum was continuously detected, in concentrations ranging from 6 to 270 cfu 100 ml(-1), while in S2 it was detected on only one sampling occasion. C. violaceum was never detected in the investigated upper soil layers (down to 15 cm) in the immediate surroundings (50 m radius) of the springs, despite continued isolation of faecal indicators. The results of the study indicate that C. violaceum may not be ubiquitous in spring water, but could occur in significant numbers in particular potable groundwaters as an autochthonous member.

Baseline models of trace elements in major aquifers of the United States

Trace-element concentrations in baseline samples from a survey of aquifers used as potable-water supplies in the United States are summarized using methods appropriate for data with multiple detection limits. The resulting statistical distribution models are used to develop summary statistics and estimate probabilities of exceeding water-quality standards. The models are based on data from the major aquifer studies of the USGS National Water Quality Assessment (NAWQA) Program. These data were produced with a nationally-consistent sampling and analytical framework specifically designed to determine the quality of the most important potable groundwater resources during the years 1991–2001. The analytical data for all elements surveyed contain values that were below several detection limits. Such datasets are referred to as multiply-censored data. To address this issue, a robust semi-parametric statistical method called regression on order statistics (ROS) is employed. Utilizing the 90th–95th percentile as an arbitrary range for the upper limits of expected baseline concentrations, the models show that baseline concentrations of dissolved Ba and Zn are below 500 μg/L. For the same percentile range, dissolved As, Cu and Mo concentrations are below 10 μg/L, and dissolved Ag, Be, Cd, Co, Cr, Ni, Pb, Sb and Se are below 1–5 μg/L. These models are also used to determine the probabilities that potable ground waters exceed drinking water standards. For dissolved Ba, Cr, Cu, Pb, Ni, Mo and Se, the likelihood of exceeding the US Environmental Protection Agency standards at the well-head is less than 1–1.5%. A notable exception is As, which has approximately a 7% chance of exceeding the maximum contaminant level (10 μg/L) at the well head.

Naturally occurring Cr 6+ in shallow groundwaters of the Yilgarn Craton, Western Australia

Hydrogeochemical investigations of the Yilgarn Craton and its margins have been dominantly in areas of deep (20–100 m) regolith, within unconfined aquifers where water tables are commonly 10–60 m below surface. These groundwaters contacting weathered Archaean rocks have a surprising (on the basis of its normal aqueous chemistry) lack of correlation between Cr content and acidity. Trivalent Cr has a soluble chemistry similar to that of Al, being extremely insoluble under neutral conditions, with appreciable solubilities only below pH 4. In contrast, dissolved Cr concentrations in the studied Yilgarn groundwaters can be very high, with no pH relationship, and are strongly correlated with the presence of ultramafic rocks. Groundwaters in contact with fresh and weathered ultramafic rocks contain consistently high (0.01–0.43 mg l −1 ) dissolved Cr concentrations, whereas waters in contact with other lithologies have Cr concentrations below detection (< 0.005 mg l −1 ). This effect is highly robust at the Yilgarn sites tested and offers a potential method for recognizing the presence of ultramafic rocks, even where they are intensely weathered. If the dissolved Cr were present as Cr 3+ , those groundwaters with Cr concentration greater than 1 μg l −1 and pH above 6 would be strongly over-saturated with respect to secondary Cr oxides. Comparison of ICP-AES and spectrophotometric analyses indicate that Cr in these groundwaters is present as Cr 6+ (i.e. CrO 4 2− ), which has a much higher solubility than Cr 3+ . A high oxidation state of dissolved Cr is also suggested by its highly anti-pathetic relationship with dissolved Fe, possibly due to the capacity of dissolved Fe 2+ to reduce CrO 4 2− to the less soluble Cr 3+ ion. A similar anti-pathetic relationship is observed between dissolved Cr and Mn. In non-reducing (i.e. Fe– and Mn–poor) groundwaters, CrO 4 2− will be relatively stable and potentially mobile. However, the mechanism by which CrO 4 2− is released into groundwater is not known. These naturally occurring concentrations of dissolved Cr 6+ are, in many cases, well above the WHO maximum concentration allowed in drinking water (0.05 mg l −1 ). In at least one area (Lawlers mining district, Western Australia), otherwise potable groundwaters cannot be used for human consumption due to concentrations of Cr 6+ up to six times greater than that allowable.

Analysis of Total Non-Volatile Non-Sulfide Reduced Sulfur in Potable and Untreated Surface and Groundwaters

An analytical method was developed to measure the total concentration of non-volatile non-sulfide reduced sulfur in treated and untreated surface and groundwater. The method was based on the alkaline reduction by Raney nickel (prepared in situ from Raney alloy) of organic and inorganic sulfur compounds (in oxidation states below +6) to sulfide. Sulfide was swept out of the reflux apparatus under nitrogen into a trap of zinc acetate and determined colorimetrically as ethylene blue. The recoveries obtained from solutions of elemental sulfur, sulfide, sulfite, thiosulfate, tetrathionate, cysteine, cystine, methionine, glutathione, allylthiourea, sulfanilamide and thiocyanate ranged from 84–102% with typical recoveries of approximately 90%. Sulfate was not detectable by the procedure. Chlorine present in potable water samples interfered in the procedure and was removed with sodium borohydride. The relative standard deviation of the method varied from 0.25 to 5.6% and averaged 3%. The detection limit based on a 500 mL sample was 3 mg m−3.

Bromine geochemistry of british groundwaters

AbstractThe concentrations of Br in potable groundwaters in the United Kingdom range from 60 to 340 µg 1-1. The occurrence of Br is described in terms of the Br/Cl weight ratio which enables small changes in bromide concentrations to be assessed in terms of salinity. Median values of Br/Cl in groundwaters range from 2.60 to 5.15 × 10−3 compared with a sea water ratio of 3.47× 10−3. In recent shallow groundwaters the Br/Cl ratio is rather variable in response to a range of natural and anthropogenic inputs (marine and industrial aerosols, industrial and agricultural chemicals including road salt). Some slight enrichment in Br/Cl also occurs naturally during infiltration as a result of biogeochemical processes.Evolution of Br/Cl along groundwater flow lines reflects the sources of increasing salinity; either the influence of marine sedimentary formations or evaporites. The groundwaters in the Triassic sandstones of the English Midlands show significant Br depletion due to the evaporite source, in contrast to groundwaters in Cumbria. Br/Cl ratios in the Sherwood Sandstone of the East Midlands mainly reflect the natural input sources and can be used to help understand the palaeohydrology.

Seasonal profile of nitrate and nitrite in potable water sources in Onitsha, Nigeria

A general steadiness in the seasonal changes of nitrate and nitrite concentrations in potable surface and ground waters in the Onitsha metropolis was observed. Spectrophotometric analysis revealed that nitrate concentration values for the months of May 1990, August 1990, November 1990 and February 1991 showed a consistent decrease of the magnitude 26.50 ± 0.71, 14.20 ± 1.33, 3.80 ± 0.40, and 3.40 ± 0.7 ppm correspondingly for well water; 7.02 ± 1.2, 2.17 ± 0.61, 1.29 ± 0.50, and 1.56 ± 0.91 ppm for borehole water; and 2.28 ± 0.60, 1.22 ± 1.30, 0.62 ± 0.20, and 0 ppm for surface streams. The nitrate concentration in all cases attained a slight equilibrium between November and February, the peak periods of the dry season. Nitrite concentrations of these water samples showed an inverse relationship to nitrate concentrations. Nitrite concentration values of 5.40 ± 0.70, 5.03 ± 0.90, 7.50 ± 0.30, and 10.60 ± 0.80 ppm were observed in the well water; and 0.76 ± 0.70, 1.20 ± 0.90, 2.00 ± 0.33, and 3.50 ± 1.00 ppm for borehole water for the corresponding months. Nitrite was at no time detected in the surface streams. © 1996 by John Wiley & Sons, Inc.

A Survey of Charge‐Balance Errors on Published Analyses of Potable Ground and Surface Waters

AbstractAlthough the charge balance for a single chemical analysis of a water's electrolytes is not a reliable gauge for the accuracy of that analysis, the percent charge‐balance error (%CBE) becomes more credible as a means for evaluating analytical technique when applied to groups of analyses.Just how good are charge balances for chemical analyses of potable ground and stream waters in mainline geological journals? Starting with each journal's first volume, a search found 68 articles in six journals (Appl. Geochem., Chem. Geol, Geochim. Cos. Acta., Ground Water, J. Hydrol, and Water Resources Res.) that had what was deemed to be “complete” analyses of individual samples' major ions. Analyses of brines and hydrothermal solutions were excluded as were “composite” averages. A total of 1,062 %CBEs were computed and tabulated, and the average was 3.99%$ 6.56 (1σ).The average %CBE (by journals) ranges from 1.55% to 9.34%. Quality of %CBE is slightly better for articles published after 1970. Not surprisingly, low ionic strength samples are prone to charge‐balance errors > 10%. Of the 1,062 charge balances calculated, 612 were positive and 450 were negative. Eight of the 68 articles had analyses that were evenly balanced between positive and negative CB errors. There are 21 articles in which the majority of analyses had negative charge‐balance errors. Thus a clear majority (39) of articles had analyses in which there were more positive than negative charge‐balance errors.Systematic error is likely for situations where the analyses in an article are predominantly positive or predominantly negative. The likely reason for the former occurrence is lab determination of alkalinity from the nonacidified field aliquot. Failure to filter samples may cause the latter situation—especially in carbonate terranes. Systematic laboratory errors involving salt standards and dilutions can also yield charge‐balance errors for a suite of analyses that are skewed to either positive or negative errors. The care with which the analyst did his/her job may also impact charge‐balance errors.

Radium isotopes and 222Rn in shallow brines, Kharaghoda (India)

The concentrations of Ra isotopes ( 224Ra, 223Ra, 228Ra and 226Ra) and 222Rn have been determined in brines from Kharaghoda, western India. The Ra isotopes concentrations in these samples are orders of magnitude higher than that reported in potable groundwaters. The 224Ra activities lie between 28 to 277 dpm per kg; about 4% to 96% of that expected from its production, calculated using 222Rn as a recoil flux monitor. The low [ 224Ra/ 222Rn] activity ratios are typical of less saline brines. Retardation factors for Ra in these brines, derived from the 222Rn- 224Ra- 228Ra system and based on a reversible exchange model, are in the range of about 0.3–114. These values are 3–4 orders of magnitude lower than that in potable groundwaters. The residence time of Ra in Kharaghoda brines is approximately one day. Our data suggest that in briny aquifers Ra is considerably less ‘particle-reactive’ than in potable groundwaters. The retardation factor for Ra shows a strong negative correlation with salinity. This anticorrelation suggests that salinity would play a crucial role in determining the mobility of Ra and its geochemical homologues through groundwater systems.