Molecular tracers of soot and sewage contamination in streams supplying New York City drinking water

Abstract

A molecular tracer method was used to assess the extent and sources of pollution to 60 stream sites that were distributed across the watersheds that supply drinking water to the greater New York City area. Samples were collected from each site annually from 2000 to 2002 during summer baseflow conditions. Twelve polycyclic aromatic hydrocarbons (PAH), 2 fragrance materials (FM), caffeine (CAF), and 7 fecal steroids (FS) were measured using a modification of EPA method 8270, which quantified concentrations to laboratory reporting levels ranging from 0.00009 to 0.016 lg/L or 3 to 5 orders of magnitude lower than method detection levels (MDL) given by EPA 8270. In 54 of 180 stream samples, concentrations of � 1 PAHs exceeded suggested, nonregulatory EPA guidance values for water supplies (0.0038 lg/L for the 5 most toxic PAHs), and PAH signatures (ratios) and spatial patterns suggested that soot from local urban/suburban combustion was the primary source. CAF, FM, and FS all showed their highest concentrations at the 3 sites with large, failing sewage treatment plants, but more complex relationships to landscape variables at remaining sites suggested a variety of anthropogenic point and nonpoint sources. Concentrations of all molecular tracers measured were strongly negatively correlated with % forest cover (¼ all forest variables used) in the watershed. Degradation of water quality can occur from a variety of point and nonpoint sources originating from both anthropogenic and natural factors including industrial effluent, sewage from waste water treatment plants (WWTP) or septic leakage, road and agricultur- al runoff, atmospheric deposition, and wildlife. The range of contaminants includes excessive nutrient loading, metals, pesticides, other toxic organic com- pounds, and pathogens. To best maintain the quality of drinking-water resources, targeted efforts to reduce or eliminate primary contamination sources first require accurate identification and quantification of all con- taminant sources that contribute to the degradation of