THE DISTRIBUTION OF ARSENIC IN GROUND AND SURFACE WATERS OF THE WOODBURY HILLS NEAR MONMOUTH, MAINE

Although the Woodbury Hills of Monmouth, Maine is only a three square mile study area, it contains four distinct metamorphic geologic formations. Groundwater flow is complex, but is assumed to be controlled by the highly faulted and folded terrain. This study aims to link arsenic occurrence in ground and surface waters with complex hydrogeology and potentially identify a source lithology for the reported arsenic occurrences.

Twenty-six water samples were collected from domestic wells, springs and surface waters within the study area. Preliminary ICP-MS results show arsenic concentrations range from <0.001 to 0.147 mg/L, up to fifteen times that of the USEPA limit of 0.010 mg/L for arsenic in drinking water.

Water from domestic wells within the study area is usually not treated before human consumption. Continued ingestion of elevated arsenic through drinking water could cause skin and/or circulatory problems and possibly lead to an increased risk in cancer.

Arsenic concentrations in waters from Woodbury Hills are not uniform and may be due to several anthropogenic point sources. One such source of arsenic is the presence of multiple pre- 1900's cemeteries, potentially harboring arsenic compounds used during the embalming process. Another potential point source could be the possible use of arsenic containing pesticides in former apple orchards. These hypotheses are considered unlikely as the dominant arsenic source in the groundwater, because most of the wells are drilled to depths of more than 300 feet and no distinct arsenic plumes have been identified from either source. Surface water analyses will help verify or refute this hypothesis.

The absence of an anthropogenic point source leaves the geology as a more likely arsenic source. A biotite granofels formation is the dominant lithology. This formation contains a rusty sillimanite schist suspected to contain pyrite. Wells containing elevated arsenic concentrations may be drilled into the rusty sillimanite schist. The interaction between bedrock and ground water may be difficult to determine due to the complexity of this metamorphic formation.