MULTI-ELEMENT ANALYSES OF PRIVATE WELLS ON THE ST. REGIS MOHAWK NATION (AKWESASNE)

摘要

One hundred and fifty four well water samples from private wells on the St. Regis Mohawk Nation (Akwesasne) were collected for multi-element analyses to determine the quality of drinking water. An additional thirty-five samples were analyzed for quality control including method blanks, standards, and duplicates, and confirm the high quality of the data collected. In twenty-six instances drinking water standards established by the Environmental Protection Agency (EPA) for various elements were exceeded. Secondary standards for manganese (n = 19) and total dissolved solids (TDS; n = 24) were most often violated. One well exceeded the EPA Maximum Contaminant Level (MCL) for Mercury, one well exceeded the MCL for Arsenic, and one well exceeded the action level for Lead. Several wells had concentrations near the EPA primary MCL for Arsenic. The source(s) of these contaminants is unknown and could be natural. Sodium was found in all wells sampled and had an average concentration of 67 ppm; however, relatively high values of >400 ppm were also measured. A wide variation in water chemistry was noted suggesting potable water is drawn from more than one source. Major chemical trends can be explained by infiltration of water through unconsolidated glacial deposits into a confined rock aquifer (Ogdensburg Dolostone) containing a source of soluble evaporite minerals contributing to enhanced concentrations of elements such as bromine, chlorine, lithium, magnesium, potassium, sodium, and strontium and characterized by a Ca:Mg ratio of ~60:40. There is no evidence for widespread impact to groundwater resources in the wells sampled; however, this statement applies only to inorganic compounds.