Arsenic variability and groundwater age in three water supply wells in southeast New Hampshire

Three wells in New Hampshire were sampled bimonthly over three years to evaluate the temporal variability of arsenic concentrations and groundwater age. All samples had measurable concentrations of arsenic throughout the entire sampling period and concentrations in individual wells varied, on average, by more than 7 µg/L. High arsenic concentrations (>10 µg/L) were measured in bedrock wells KFW-87 and SGW-93, consistent with the high pH and low dissolved oxygen typically found in fractured crystalline bedrock aquifers in New Hampshire. Lower arsenic concentrations (<10 µg/L) at well SGW-65 were consistent with lower pH typical of glacial aquifers in New Hampshire.