Water Resources Research Act Program

Details for Project ID 2009CT202B

Evaluation of Turbidity Acidification During Sampling and Analytical Preparation as the Cause of Observed Manganese Anomalies in Drinking Water Wells

Institute: Connecticut
Year Established: 2009 Start Date: 2009-03-01 End Date: 2011-02-28
Total Federal Funds: $9,478 Total Non-Federal Funds: $19,243

Principal Investigators: Gary A. Robbins

Project Summary: According to the Connecticut Department of Environmental Protection (DEP) files more than 80 locations (involving one or more bedrock wells) have been identified where concentrations of manganese have exceeded the State action level of 0.5 mg/l. Concentrations in domestic wells have been observed ranging up to 100 mg/l. Such levels may pose a neurological hazard. Spatial statistical studies we have conducted indicate the manganese levels are anomalous with respect to background levels in Connecticut and throughout New England, which average about 0.1 mg/l. A number of potential anthropomorphic causes of the anomalous well concentrations have been proposed. By law, if wells are contaminated the DEP is charged with providing an alternative water supply. In cases of rural private wells, the solution applied is an expensive filter system that is usually maintained by the DEP or local health officials, costing thousands of dollars to install and maintain. Recent analyses of the DEP data files suggest that the high manganese concentrations observed are strongly correlated with turbidity. There are two possible explanations for this observation. The high manganese levels may be an artifact of leaching metals from suspended rock flour or fragments of oxidized well casing when the samples are collected and then preserved by acidification, which is a standard approach used by the DEP when they collect the samples. Even if samples are not preserved in the field, standard protocol for metal analysis by inductively coupled plasma (ICP) is pretreatment of samples with acid if they exhibit turbidity greater than 1 NTU. ICP has become the most common method of analysis for metals and is used by the Dept. of Public Health laboratory, which conducts analysis for the DEP, and private sector laboratories in the State. We are proposing to test the acidification hypothesis by conduct systematic laboratory leaching studies and field tests that involve collecting filtered and unfiltered samples.