Hydrogeochemical Evolution of Groundwater In Southeastern New York

A hydrogechemical analysis was conducted utilizing water samples collected from fifteen private groundwater wells from four different counties in eastern New York State. The samples collected from Ulster, Dutchess, Rockland and Orange counties were analyzed for pH, dissolved oxygen, conductivity, alkalinity, nitrate, phosphate, chloride, ammonia, calcium, magnesium, sodium and potassium. The potable groundwater resources of the study area occur mostly in Paleozoic consolidated rocks mostly composed of fractured shale and carbonates. The depth of the wells ranged between 46m – 93m (150ft - 300ft). Typically, water samples from fractured shale aquifers contain high amounts of sodium, and potassium. Higher levels of calcium and magnesium have been observed due to the rock water interaction in carbonate aquifer systems. Results were then compiled and it was found that all wells but one fell within the standard allowable drinking water regulations. One well in Ulster County had high levels of nitrate which are above the USEPA's maximum contamination level (MCL). The occurrences of high levels of chloride, nitrate and bicarbonate in several groundwater samples are caused by recharging water containing fertilizers and the natural dissolution of minerals.