EVALUATING SOURCES OF ARSENIC IN GROUNDWATER RESOURCES OF LEBANON, CONNECTICUT

Arsenic is a tasteless and odorless metalloid that may be geologically sourced or anthropogenic. Under appropriate environmental conditions, arsenic has been known to leach from these sources contaminating groundwater. The susceptibility of residents within Connecticut to be exposed to this cancer-causing agent is unknown; however, the number of individuals that rely on private well water that could potentially be contaminated with arsenic has become a recent health concern. In October of 2013 traces of arsenic were reported in the well water at Lebanon Elementary School. Unfortunately, the source remains unknown. In cooperation with the Department of Energy and Environmental Protection and the Connecticut Geological Survey, one hundred randomly selected well water samples were collected and analyzed for Lebanon to evaluate and examine the distribution of arsenic with respect to rock type, groundwater flow, and potential anthropogenic sources. Results indicate that samples intersecting the Brimfield Schist, the Hebron Gneiss, and the Scotland Schist at the surface exhibit statistically significant higher arsenic concentrations than the remaining rock types. This suggests that a correlation exists between rock type and arsenic concentrations given that the Brimfield Schist has been known to contain arsenic bearing minerals and wells are likely to intersect this rock type at depth. Although arsenic concentrations were greater and occurred more often in bedrock wells than dug wells, results indicate that arsenic concentrations may be both geologically sourced and anthropogenic. Groundwater flow and groundwater quality conditions indicate that the former landfill is not a source for arsenic contamination. Furthermore, relatively high pH, low concentrations of iron, and low concentrations of manganese in areas with high arsenic suggest that arsenic complexation may be occurring, groundwater is aged, and/or wells are intersecting calc-silicate rock of the Tatnic Hill Formation. Continuation of this study by additional groundwater analyses will contribute to the development of policies and regulations regarding arsenic in private drinking water wells for towns similar to Lebanon, Connecticut by local and State health officials.