RESUMO
In the US, private well users are responsible for their own water quality testing, but local health officials are often uncertain what tests to recommend, particularly for regulated organic chemical contaminants. This study evaluated the utility of suspect and non-target screening (NTS) high resolution mass spectrometry (HRMS) as a tool to identify a wide range of organic chemicals of emerging concern in private well water and to inform well water management decisions. Qualitative NTS, which detects chemicals without providing concentrations, was used to analyze 25 private well water samples from Wake County, North Carolina. Using the NIST 20 mass spectral database (M1), NTS tentatively identified 106 unique organic chemicals across the 25 samples and an average of 11 organic chemicals per sample. At least one USEPA ToxCast chemical was identified in each private well water sample. Private well water users were interviewed prior to and after their sample's NTS results were reported back; four county groundwater managers were interviewed after aggregated results for all 25 water samples were reported back. All but one well user participant chose to participate in the reporting-back post-interview. The 24 private well users found NTS results useful and valued the contextualization of their results using NTS results for other well users and a local municipal water sample. Most private well users (67%) were surprised by their well water results, especially regarding the number of tentatively identified organic chemicals detected. All the groundwater managers believed the NTS results were useful and could help improve their testing recommendations to private well users. Even with qualitative limitations, NTS results can be an effective and valuable tool to inform the public and governance stakeholders in decisions around groundwater quality management.
RESUMO
Groundwater is a primary potable water supply for coastal North Carolina (NC), but the increased intensity of extreme rainfall events and floods may exacerbate surface and subsurface processes that contribute anthropogenic chemicals to wells in the major confined aquifers of this region. We evaluated groundwater for organic chemicals of emerging concern (CEC) and the presence of tritium using flooded and not-flooded wells in the NC Department of Environmental Quality well monitoring network across the NC Coastal Plain. Flooded wells experienced standing water around the well casing at least once during the study period. Tritium concentrations, which indicate modern water presence (water recharged after 1953), were significantly greater in groundwater from flooded wells than not-flooded wells. In confined aquifers, modern water was detected at greater depths in flooded wells (206 m) than not-flooded wells (100 m). Suspect-screening high resolution mass spectrometry (HRMS) analysis of 150 groundwater samples yielded a total of 382 unique organic chemicals. Each groundwater sample contained, on average, 19 tentatively identified chemicals from the NIST 20 mass spectral database (M1) and 9 USEPA ToxCast chemicals. The number of tentatively-identified chemicals per sample was not significantly different among aquifers demonstrating the pervasive presence of the detected CECs in unconfined and confined aquifers. The presence of modern water in groundwater from flooded wells coincided with higher detection frequencies of certain organic contaminant classes, particularly pharmaceuticals, food additives, and regulated aromatic hydrocarbons. These results indicate that wells in both unconfined and confined aquifers are susceptible to modern water contamination during flood events; this finding has critical public health implications for coastal communities.