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Water Standard (water + standard)
Selected AbstractsHydrogeochemistry of seepage water collected within the Youngcheon diversion tunnel, Korea: source and evolution of SO4 -rich groundwater in sedimentary terrainHYDROLOGICAL PROCESSES, Issue 9 2001Gi-Tak Chae Abstract In the Youngcheon Diversion Tunnel area, South Korea, 46 samples of tunnel seepage water (TSW) and borehole groundwater were collected from areas with sedimentary rocks (mainly sandstone and shale) and were examined for hydrogeochemical characteristics. The measured SO4 concentrations range widely from 7·7 to 942·0 mg/l, and exceed the Korean Drinking Water Standard (200 mg/l) in about half the samples. The TDS (total dissolved solid) content generally is high (171,1461 mg/l) from more shale-rich formations and also reflects varying degrees of water,rock interaction. The water is classified into three groups: Ca SO4 type (61% of the samples collected), Ca SO4 HCO3 type (15%) and Ca HCO3 type (24%). The Ca HCO3 type water (mean concentrations=369 mg/l Ca, 148 mg/l HCO3 and 23 mg/l SO4) reflected the simple reaction between CO2 -recharged water and calcite, whereas the more SO4 -rich nature of Ca SO4 type water (mean concentrations=153 mg/l Ca, 66 mg/l HCO3 and 416 mg/l SO4) reflected the oxidation of pyrite in sedimentary rocks and fracture zones. Pyrite oxidation resulted in precipitation of amorphous iron hydroxide locally within the tunnel as well as in high concentrations of Ca (mean 153 mg/l) and Na (mean 49 mg/l) for TSW, and is associated with calcite dissolution resulting in pH buffering. The pyrite oxidation required for the formation of Ca SO4 type water was enhanced by the diffusion of oxygenated air through the fractures related to the tunnel's construction. The subsequent outgassing of CO2 into the tunnel resulted in precipitation of iron-bearing carbonate. Copyright © 2001 John Wiley & Sons, Ltd. [source] Glacial Sediment Causing Regional-Scale Elevated Arsenic in Drinking WaterGROUND WATER, Issue 6 2005Melinda L. Erickson In the upper Midwest, USA, elevated arsenic concentrations in public drinking water systems are associated with the lateral extent of northwest provenance late Wisconsin-aged drift. Twelve percent of public water systems located within the footprint of this drift (212 of 1764) exceed 10 ,g/L arsenic, which is the U.S. EPA's drinking water standard. Outside of the footprint, only 2.4% of public water systems (52 of 2182) exceed 10 ,g/L arsenic. Both glacial drift aquifers and shallow bedrock aquifers overlain by northwest provenance late Wisconsin-aged sediment are affected by arsenic contamination. Evidence suggests that the distinct physical characteristics of northwest provenance late Wisconsin-aged drift,its fine-grained matrix and entrained organic carbon that fosters biological activity,cause the geochemical conditions necessary to mobilize arsenic via reductive mechanisms such as reductive desorption and reductive dissolution of metal oxides. This study highlights an important and often unrecognized phenomenon: high-arsenic sediment is not necessary to cause arsenic-impacted ground water,when "impacted" is now defined as >10 ,g/L. This analysis also demonstrates the scientific and economic value of using existing large but imperfect statewide data sets to observe and characterize regional-scale environmental problems. [source] Arsenic in Glacial Drift Aquifers and the Implication for Drinking Water,Lower Illinois River BasinGROUND WATER, Issue 3 2001Kelly L. Warner The lower Illinois River Basin (LIRB) covers 47,000 km2 of central and western Illinois. In the LIRB, 90% of the ground water supplies are from the deep and shallow glacial drift aquifers. The deep glacial drift aquifer (DGDA) is below 152 m altitude, a sand and gravel deposit that fills the Mahomet Buried Bedrock Valley, and overlain by more than 30.5 m of clayey till. The LIRB is part of the USGS National Water Quality Assessment program, which has an objective to describe the status and trends of surface and ground water quality. In the DGDA, 55% of the wells used for public drinking-water supply and 43% of the wells used for domestic drinking water supply have arsenic concentrations above 10 ,g/L (a new U.S. EPA drinking water standard). Arsenic concentrations greater than 25 ,g/L in ground water are mostly in the form of arsenite (AsIII). The proportion of arsenate (AsV) to arsenite does not change along the flowpath of the DGDA. Because of the limited number of arsenic species analyses, no clear relations between species and other trace elements, major ions, or physical parameters could be established. Arsenic and barium concentrations increase from east to west in the DGDA and are positively correlated. Chloride and arsenic are positively correlated and provide evidence that arsenic may be derived locally from underlying bedrock. Solid phase geochemical analysis of the till, sand and gravel, and bedrock show the highest presence of arsenic in the underlying organic-rich carbonate bedrock. The black shale or coal within the organic-rich carbonate bedrock is a potential source of arsenic. Most high arsenic concentrations found in the DGDA are west and downgradient of the bedrock structural features. Geologic structures in the bedrock are potential pathways for recharge to the DGDA from surrounding bedrock. [source] VOLATILE ORGANIC COMPOUNDS IN GROUND WATER FROM RURAL PRIVATE WELLS, 1986 TO 1999,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2004Michael J. Moran ABSTRACT: The U.S. Geological Survey (USGS) collected or compiled data on volatile organic compounds (VOCs) in samples of untreated ground water from 1,926 rural private wells during 1986 to 1999. At least one VOC was detected in 12 percent of samples from rural private wells. Individual VOCs were not commonly detected with the seven most frequently detected compounds found in only 1 to 5 percent of samples at or above a concentration of 0.2 microgram per liter (,g/l). An assessment level of 0.2 ,g/l was selected so that comparisons of detection frequencies between VOCs could be made. The seven most frequently detected VOCs were: trichloromethane, methyl tert -butyl ether, tetrachloroethene, dichlorodifluoromethane, methylbenzene, 1,1,1-trichloroethane, and 1,2-dibromo-3-chloropropane. Solvents and trihalomethanes were the most frequently detected VOC groups in private wells. The distributions of detections of gasoline oxygenates and fumigants seemed to be related to the use patterns of compounds in these groups. Mixtures were a common mode of occurrence of VOCs with one-quarter of all samples with detections including two or more VOCs. The concentrations of most detected VOCs were relatively small and only 1.4 percent of samples had one or more VOC concentrations that exceeded a federally established drinking water standard or health criterion. [source] | ||||||||||