Combined analysis of bile acids and sterols/stanols from riverine particulates to assess sewage discharges and other fecal sources

This investigation aimed to demonstrate the combined use of bile acids, sta nols, and sterols to assess fecal matter inputs into aquatic environments. Bile acids, stanols, and sterols were determined in suspended particulates in water samples collected from sites in the vicinity of discharges from se wage treatment works along the course of the Avon River, Bristol, U.K. The concentrations of the major fecal bile acids [lithocholic (LCA) and deoxych olic (DOCA)] were determined using GC and GC/MS and found to increase along the course of the river. These results agreed with those obtained for copr ostanol, the traditional indicator of fecal pollution and other related ste rols and stanols. In contrast, sterols and stanols not originating from fec es, i.e., 24-ethylcholesterol and 24-ethylcholestanol, tended to decrease i n concentration as compared to coprostanol and other fecal markers in the l ower reaches of the river. The increasing concentration of bile acids downs tream of sewage discharges correlates with the coprostanol/(coprostanol + 5 alpha-cholestanol) ratio of >0.7, thus supporting the use of bile acids as sewage pollution markers. Overall, it is demonstrated that a combined mult imolecular approach involving bile acids, stanols, and sterols provides an enhanced means of assessing fecal matter inputs into aquatic environments.