Ground-water quality and potential contamination of the Mississippi River alluvial aquifer in northeastern Arkansas.

摘要

This study of ground water from 38 wells drilled in the Mississippi River Valley alluvial aquifer in Mississippi County and the eastern parts of Craighead and Poinsett Counties, Arkansas indicates that the water is generally hard, calcium bicarbonate type, often with iron concentrations greater than one milligram per liter. The pesticide fluometuron was detected in one sample at a concentration of 0.5 mug/L. Bentazon was detected in three samples at concentrations of 2.5, 0.3, and 0.3 mug/L. The occurrences of the pesticides represent isolated incidents rather than a widespread aquifer contamination. All detections were below health and safety standards. Nitrate is present in several wells at concentrations above 0.15mg/L, one of which exceeded the EPA established maximum contaminant level for drinking water of 10 milligrams per liter as nitrogen. Except for two wells nitrate and iron are not present together at concentrations above 0.15mg/L. This is probably due to microbially mediated reactions. Nitrate concentrations above 0.15 mg/L is only present in wells that are less than 60 feet deep and near permeable soils. Iron is present in wells that are not near permeable soils or wells that are greater than 40 feet deep. Calcium, bicarbonate and total dissolved solids concentrations increase with well depth.