NONPOINT SOURCES OF PERCHLORATE IN GROUNDWATER OF URBAN SOURCES

Perchlorate is a concern due to the threat of a mandated national drinking water standard and the likelihood that perchlorate disrupts normal thyroid functions. The Environmental Protection Agency has set a reference dose of 0.0007 mg/kg/day of perchlorate which has prompted many state action levels for drinking water. Nonpoint sources contribute to the perchlorate concentration of groundwater, however since they are widespread they are difficult to discern and remediate. We measured perchlorate concentrations of nonpoint sources in Suffolk County, NY and identified these as rain water, soil water, lawn fertilizers, wastewater, road salt and road runoff. Concentrations were measured using an ion chromatograph coupled with a duel mass spectrometer at Texas Tech University. Due to the high infiltration rates and large rain events in our study area, perchlorate from rain water and fertilizer is not concentrated in the soil profile, therefore soil water concentrations won't be higher than that of the sources. The known sources to soil water under fertilized turfgrass are an organic fertilizer, with 9 ppb ClO₄, and rain water, measuring less than 0.2 ppb ClO₄. The soil water samples in our study area ranged between 3 to 250 ppb ClO₄, indicating an unknown source of perchlorate or an unknown mechanics to form and/or concentration perchlorate in the soil profile. Road runoff samples measured as high as 18 ppb ClO₄. Proposed sources to road runoff include rain water, road flares, air bags, road salt and possible nearby use of Chilean Saltpeter as a fertilizer. Mass balance calculations conclude that these sources alone can not account for the concentrations we have measured in our study area. Wastewater from twenty four cesspool/septic tanks had an average value of 3 ± 4 ppb ClO₄, which can be attributed to bleach used in household cleaning and laundry products.