Measuring change in sterol input to estuarine sediments

In complex estuarine environments suites of sterols can be used to define a utochtonous and allochtonous sources of organic matter and to identify biol ogical processes occurring in situ. Coprostanol is a major faecal sterol pr esent in human waste (40%-60% of total faecal sterols excreted). As raw sew age is the primary source of this sterol, its determination is an effective measure of the degree of untreated sewage contamination. Mean concentratio ns of sterols in mug.g(-1) dry sediment are reported for the Tay Estuary. R atios of coprostanol/cholesterol, coprostanol/epicoprostanol and the 5 beta /(5 beta + 5 alpha) stanol index were used to assess and cross-validate ste rol sources. These results have a special significance in that the disposal of raw sewage is being phased-out in north-east Scotland. Our study will t herefore act as a record, showing the degree of contamination during discha rge of raw sewage. Adherence to the EC Urban Waste Water Directive 1991 (91 /271/EEC) by the Scottish Environmental Protection Agency and the North of Scotland Water Authority, means that all sewage sludge should receive prima ry treatment. This work establishes a baseline against which reduction in s edimentary sterol concentrations can be measured. (C) 2001 Elsevier Science Ltd. All rights reserved.