Fecal sterol and bile acid biomarkers: Runoff concentrations in animal waste-amended pastures

Nonpoint source pollution is the leading remaining cause of water quality problems. The extent of NPS pollution is often more difficult or expensive to monitor at the point(s) of origin, as compared to monitoring of point sources. This study evaluated the hypothesis that animal manure (chicken, cow, horse, and pig) applied to pasture contribute fecal sterols and bile acids to runoff. The study also assessed the potential benefit of fecal sterols and bile acids as biomarkers in distinguishing fecal pollution and its sources. Fecal sterol and bile acid concentrations were determined in flow-weighted composite runoff samples collected from 2.4∈×∈6.1 m plots (n∈=∈3) amended with manure. Runoff was generated from simulated rainfall (152 mm.h ^-1). Runoff samples from manure-amended plots showed high concentrations of fecal sterol (ranged from 13∈±∈1 to 1,287∈±∈183) and bile acid (ranged from 24∈±∈1 to 2,251∈±∈248) biomarkers. The profiles of fecal sterols and bile acids in runoff samples were similar to those of fresh manure for all selected animals. For runoff and fresh manure, chenodeoxycholic acid, deoxycholic acid, epicoprostanol, and hyodeoxycholic acid were consistent biomarkers for chicken, cow, horse, and pig, respectively, suggesting that sterols and bile acids can be used to identify sources and occurrence of fecal matter in water and sediments.