Comparison of native ground-water quality with water quality in agricultural and residential areas of Long Island, New York

Estimates of nitrogen loads entering Long Island Sound from ground water and streams on Long Island, New York, 1985-96

“…Studies that address the concentrations of nitrogen in ground water and surface water on Long Island include Perlmutter and Koch (1975), Katz and others (1980), Ragone and others (1981), and Bleifuss and others (1998). Water-quality differences between several areas of differing land use on Long Island are reported by LeaMond and others (1992), Eckhardt and others (1989), Eckhardt and Stackelberg (1995), and Pearsall (1996).…”

“…Under natural (predevelopment) conditions, water that discharges from the deep (Magothy and Lloyd) aquifers to the Sound can be in the ground-water system for more than 400 years (Franke and Cohen, 1972) and probably has not been affected chemically by human activities. Water in the Lloyd aquifer contains less nitrogen than water in the other aquifers; the median nitrate concentration in samples from wells screened in the Lloyd aquifer in Nassau County within 1 mi of the coast was 0.44 mg/L as N. Median nitrate concentrations in samples from the Magothy aquifer in 1989 in undeveloped areas were less than 0.3 mg/L as N (Pearsall, 1996). In some developed areas, however, pumping has drawn contaminated water from the upper part of the aquifer system into the deep aquifers (Eckhardt and Pearsall, 1989), where it affects water quality.…”

Effects and distribution of iron-related well-screen encrustation and aquifer biofouling in Suffolk County, Long Island, New York

“…Native (predevelopment) water quality is difficult to characterize because (1) the effects of human activities are evident in most parts of the upper glacial and Magothy aquifers, and (2) geochemical conditions vary locally, and those in areas of ground-water recharge differ from those in areas of discharge. Native water as described by de Laguna (1964), Eckhardt andothers (1988), andPearsall (1996) is summarized in table 3. De Laguna (1964) summarized native quality of ground water in the upper gla- cial aquifer in central Suffolk County; Eckhardt and others (1988) summarized the effects of land use on water quality at wells screened within 40 ft of the water table in several areas; and Pearsall (1996) compared the amounts of several major ions derived from human activities in ground water from residential areas with those in ground water from agricultural areas.…”

“…Native water as described by de Laguna (1964), Eckhardt andothers (1988), andPearsall (1996) is summarized in table 3. De Laguna (1964) summarized native quality of ground water in the upper gla- cial aquifer in central Suffolk County; Eckhardt and others (1988) summarized the effects of land use on water quality at wells screened within 40 ft of the water table in several areas; and Pearsall (1996) compared the amounts of several major ions derived from human activities in ground water from residential areas with those in ground water from agricultural areas. The data from Pearsall (table 2) are from the lower part of the Magothy aquifer in areas of ground-water recharge in central Suffolk County, and are assumed to be representative of predevelopment conditions.…”

“…Sulfate data collected from the Magothy aquifer throughout Suffolk County as part of an investigation into natural geochemical processes on Long Island indicate that dissolved sulfate concentrations greater than 3.0 mg/L are found primarily along the southern shore (Pearsall, 1996). The oxidation of authigenic pyrite has been used to explain increased sulfate concentrations along flow paths elsewhere in the Magothy aquifer (Knobel and Phillips, 1988).…”