Sterols as bio-markers for waste impact and source characterization in stream sediment

Sterols are involved in life processes in organisms and are therefore potential biomarkers for assessment of environmental ecosystems. Current data indicate that sterols are persistent in stream sediments, since sterols are not sufficiently soluble in water to be readily detected in water samples. Stream sediment therefore can act as an integrating exposure index of pollution for animal or human waste in streams. The study reported here was conducted in two phases. Phase 1 involved development and validation of a simplified method for the determination of sterols, and Phase 2 involved application of that method to evaluate actual environmental samples. Stream sediment samples from agricultural settings, wastewater-treatment-facility outfalls, and recreational state parks in Iowa and Pennsylvania were analyzed for sterol compounds. Sterol profiles differ considerably among animals, and the study distinguished sterol profiles within stream sediments. Feces from different animal species were also analyzed to provide reference sterol profiles. Individual-sterol and total-sterol concentrations were determined. Sterols were observed in 73.4 percent of environmental sediment samples tested (n = 124) and at 100 percent of the sites (n = 18). Coprostanol, a key indicator of fecal pollution, was observed in 38.7 percent of the environmental sediment samples tested and at 72.2 percent of the sites. Samples were collected from multiple points at selected sites, and duplicate samples were analyzed at a frequency of 16.1 percent. One to five months later, additional samples were collected from the duplicate locations and were analyzed. Data generated by the study provide a basis for stream sediment monitoring that enables the chronological recording of waste impact; this method may be coupled with other measurements to determine the extent and possible source of stream contaminants.