Tracing faecal pollution by coprostanol and intestinal bacteria in an ice-covered finnish lake loaded with both industrial and domestic sewage

The relationships existing between coprostanol (5β-cholestan-3β-ol), faecal indicator bacteria and various physico-chemical tracer and bacterial stress factors in an ice-covered Finnish lake were investigated. Field observations show that coprostanol lies below the theoretical mixing line, indicating a net removal, primarily by settling together with suspended sediments. Faecal indicator bacteria, however, are differently transported and are removed by various environmental factors e.g. industrial wastes. Thus, only faecal streptococci show a regional covariance to coprostanol. Principal component analyses reveal a strong correlation between coprostanol and faecal streptococci in water but not with coliforms and sulfite reducing sporing anaerobs. However, in sediments also coliforms are correlated significantly with coprostanol and faecal streptococci. Therefore it might be necessary to estimate the quality of those waters polluted by both industrial and faecal wastes by means of coprostanol, a principal sterol in sewage of man and higher animals, which is thus well suited as a chemical marker of faecal pollution.