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۱Spatial Distribution of Solutes in Aquifer Outcrop Zones along the Brazos River, East–Central Texas
اطلاعات انتشار: International Journal Of Environmental Research، پنجم،شماره۳، Summer ۲۰۱۱، سال ۰
تعداد صفحات: ۸
Concentrations of several solutes – nitrate, arsenic, sulfate, boron, chloride, and bromide – along with total dissolved solids (TDS) in ten counties bordering the Brazos River in east–central Texas were compiled, mapped, and analyzed relative to regional land use and geology. Agriculture and oil\gas production are major activities and potential sources of groundwater contamination in the study area. Data were compiled from 104 water wells with a median depth of 446 ft (136 m) in the outcrop zones of six sedimentary aquifers: Carizzo–Wilcox, Queen City, Sparta, Yegua–Jackson, Gulf Coast, and Brazos Alluvium. Only two observations surpassed the 44.3 mg\L drinking water standard for nitrate, and four observations exceeded the 10 ug\L standard for arsenic. The median chloride concentration was 53 mg\L; however, the maximum level was almost three times the secondary drinking water standard of 250 mg\L. Chloride, bromide, sulfate, and boron concentrations resembled TDS patterns, with numerous samples exceeding secondary TDS drinking water standards in the Yegua–Jackson Aquifer. Most chloride\bromide ratios were between 100 and 300. Overall, results of this study suggest that natural processes exert a primary control on solute concentrations in the above aquifers, with a potential for modest anthropogenic impacts from agriculture and oil\gas production.
۲Nitrate and Chloride Concentrations in Groundwater beneath a Portion of the Trinity Group Outcrop Zone, Texas
اطلاعات انتشار: International Journal Of Environmental Research، ششم،شماره۳، Summer ۲۰۱۲، سال ۰
تعداد صفحات: ۶
Using a geographic information system and statistics, we evaluated spatial distributions of nitrate and chloride concentrations in groundwater in an area of north–central Texas with agricultural activity, in addition to oil and natural gas exploration and production. Data were compiled from 40 water wells sampled in 2007. Nitrate concentrations in three wells exceeded the maximum contaminant level (44 mg\L) for drinking water. The highest nitrate concentration was 149 mg\L, and concentrations were generally higher in shallower wells. Chloride concentrations exceeded the 250 mg\L secondary drinking water standard in two wells, with no significant association between chloride concentration and well depth. Results of this study suggest localized human impacts, especially for nitrate, and identify areas warranting future monitoring.
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