Activities associated with agricultural, residential, commercial, and industrial land uses have affected water quality in 4 stratified-drift aquifers in Connecticut. Water-quality data from 116 shallow wells were segregated by land use. Nonparametric statistical analysis indicate that 27 water-quality variables differ at the 0.05 significance level for samples from at least one land-use area. Most constituent concentrations or detection frequencies are lowest in samples from undeveloped areas. Groundwater quality is more adversely affected in tilled than untilled agricultural areas. Twenty percent of wells in tilled areas yielded water with nitrogen concentrations > 10 mg/L. Atrazine was detected in one-third of the wells in tilled areas. Median concentrations of most inorganic constituents are higher in sewered than in unsewered residential areas. One or more of 17 volatile organic compounds were detected in 62 percent of wells in unsewered areas. Chloroform was detected in sewered areas significantly more often than in undeveloped, tilled agricultural, and unsewered residential areas. Water beneath commercial areas is most adversely affected. Median sodium, chloride, and dissolved solids concentrations are highest in samples from commercial areas. Tetrachloroethylene was detected in 50 percent of wells in commercial areas at concentrations up to 1,300 microg/L. Trichloroethylene and 1,2-transdichloroethylene were found in more than 40 percent of wells in commercial areas. In industrial areas, 91% of the wells sampled contained 1 or more of 12 volatile organic compounds. Chloroform was the most commonly detected compound followed by tetrachloroethylene and 1,1,1-trichloroethane. (USGS)
