Atacama perchlorate as an agricultural contaminant in groundwater: Isotopic and chronologic evidence from Long Island, New York
Perchlorate (ClO4−) is a common groundwater constituent with both synthetic and natural sources. A potentially important source of ClO4− is past agricultural application of ClO4−-bearing natural NO3− fertilizer imported from the Atacama Desert, Chile, but evidence for this has been largely circumstantial. Here we report ClO4− stable isotope data (δ37Cl, δ18O, and Δ17O), along with other supporting chemical and isotopic environmental tracer data, to document groundwater ClO4− contamination sources and history in parts of Long Island, New York. Sampled groundwaters were oxic and ClO4− apparently was not affected by biodegradation within the aquifers. Synthetic ClO4− was indicated by the isotopic method in groundwater near a fireworks disposal site at a former missile base. Atacama ClO4− was indicated in agricultural and urbanizing areas in groundwaters with apparent ages >20 years. In an agricultural area, ClO4− concentrations and ClO4−/NO3− ratios increased with groundwater age, possibly because of decreasing application rates of Atacama NO3− fertilizers and/or decreasing ClO4− concentrations in Atacama NO3− fertilizers in recent years. Because ClO4−/NO3− ratios of Atacama NO3− fertilizers imported in the past (∼2 × 10−3 mol mol−1) were much higher than the ClO4−/NO3− ratio of recommended drinking-water limits (7 × 10−5 mol mol−1 in New York), ClO4− could exceed drinking-water limits even where NO3− does not, and where Atacama NO3− was only a minor source of N. Groundwater ClO4− with distinctive isotopic composition was a sensitive indicator of past Atacama NO3− fertilizer use on Long Island and may be common in other areas that received NO3− fertilizers from the late 19th century through the 20th century.
|Publication Subtype||Journal Article|
|Title||Atacama perchlorate as an agricultural contaminant in groundwater: Isotopic and chronologic evidence from Long Island, New York|
|Series title||Environmental Science & Technology|
|Contributing office(s)||WMA - Earth System Processes Division|
|Other Geospatial||Long Island|
|Google Analytic Metrics||Metrics page|