Description: This articles discusses the spatial distribution of solutes in Aquifer outcrop zones along the Brazos River in east-central, Texas. 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 ...

Description: This article discusses a problem of publics and the curious case of Texas.

Description: This article discusses nitrate, arsenic, and selenium concentrations in the Pecos Valley Aquifer in west Texas. Nitrate, arsenic, and selenium concentrations in the Pecos Valley Aquifer of west Texas compiled, mapped, and analyzed in the context of local geology and land use. Alluvial deposits of sand, silt, clay, and gravel compose the unconfined aquifer. Ranching and farming are predominant land uses in the rural study area. Data were tabulated from 79 water wells with a median depth of 75 m and mapped with a geographic information system (GIS). The wells were sampled between the years 2003 and 2008. Total dissolved solids (TDS) concentrations in the aquifer were very high, with a median value of 2,687 mg/L. Approximately 18% of observations exceeded the 44.27 mg/L drinking water standard for nitrate, whereas 6% exceeded the 10 μg/L standard for selenium. There was a statistically significant, direct correlation between arsenic and selenium, as well as between nitrate and selenium concentrations. Moreover, arsenic and selenium concentrations were significantly higher in shallower wells. Probable sources of groundwater contamination in the study area include natural (geological) sources and agricultural activity.

Description: This article discusses excess molar volumes of binary mixtures of cyclohexane and y-butyrolactone with aromatic hydrocarbons. Abstract: Excess molar volumes of cyclohexane + benzene, cyclohexane + toluene, cyclohexane + p-xylene, y-butyrolactone + benzene, y-butyrolactone + toluene, and y-butyrolactone + m-xylene have been measured at 298.15 K. For the first three systems, Vᴱ is positive throughout the entire concentration range. Vᴱ is negative for binary mixtures containing y-butyrolactone, which indicates significant interaction between y-butyrolactone and the aromatic hydrocarbon.

Description: This article addresses, from a historical perspective, Newton's sums of like powers of natural numbers.