IS ONCE EVERY 3-5 YEARS ENOUGH?: SEASONALITY IN PRIVATE WELL WATER QUALITY OF NORTHERN MT. DESERT ISLAND, MAINE

Prior studies show that arsenic exposure, even at very low levels, can result in long-term health effects, such as bladder cancer, heart disease, diabetes, and more. The EPA limits arsenic contamination in public drinking water supplies to 10 ppb, but private drinking water supplies are unregulated. The state recommends private well owners test their wells for arsenic every 3-5 years; however, preliminary research suggests that some well water quality may vary seasonally. “All About Arsenic”, a collaborative project spearheaded by MDI Biological Laboratory (MDIBL) and Dartmouth College, empowers secondary school educators in Maine and New Hampshire to engage their students and communities in collecting private well water data while simultaneously promoting data literacy skills through analysis and science communication around locally relevant topics like groundwater contamination. Initially funded through an EPA Environmental Education award, the project is currently supported by an NIGMS/NIH Science Education Partnership Award (SEPA). Researchers from College of the Atlantic (COA) have partnered with MDIBL to ask additional research questions. From 2016-2019, COA researchers sampled over 140 private wells in the northern Mt. Desert Island region to assess spatial variations in groundwater quality. Results of this initial study suggest that groundwater components generally correlate with geologic features, such as bedrock types and fault locations. These data also illuminated a few secondary issues facing private well owners: seasonal variations in water yield and quality and the complexity of water filtration in relation to these variables. Building on this existing dataset, we strategically resampled 25 wells with arsenic values spanning ~1 ppb to >250 ppb. These new data highlight changes in arsenic abundance, more than double in some cases, between dry season (~summer-fall) and wet season (~winter-spring) sampling. Prior studies report average seasonal variations of ~3 ppb; recent research on low dose exposure proposes a 3 ppb variation could be significant in terms of health. A value close to 10 ppb may fall above or below the limit, either motivating the homeowner to remediate or indicating a lower cause for concern.