URBAN GEOCHEMISTRY AND WATER QUALITY OF ARKANSAS RIVER SURFACE WATER THROUGH THE LITTLE ROCK METROPOLITAN AREA

The Arkansas River flows over 20 miles through the Little Rock Metropolitan area, which utilizes the river for hydroelectricity, irrigation, recreation, transportation,and runoff and effluent discharges. Water samples were taken along the river upstream, downstream, and in Little Rock on four separate occasions over a nine-month period. During sampling water parameters were collected, such as pH, salinity, conductivity, temperature, and dissolved oxygen; and water samples were analyzed for anions, cations, alkalinity, and trace metals. Samples analyzed from September 2014 showed the highest conductivity (over 1000uS) and elevated concentrations of chloride (> 207 ppm), sulfate (>70 ppm), and boron (>70 ppb), which was more than double the other sampling events. Each sampling event also revealed a gradient from higher to lower concentrations in most constituents as it flowed through Little Rock, such as fluoride, chloride, sulfate, manganese, and iron. Concentrations were compared to water levels in the Arkansas River, upstream activity, and with identified effluent discharges to the river from the Little Rock area to understand the chemical changes in the Arkansas River in the Little Rock area.