Sterol biomarkers and chemometric techniques for testing sewage contamination in sediment of Langat River, Malaysia

Sewage contamination that origin from multiple sources such as human, animals and domestic sources has been recognised as one of the major cause of deterioration in water quality especially in Selangor state. For many years, the Langat River has been experiencing anthropogenic inputs that possibly originates from more than three million inhabitants surrounding in the river basin. Sterols, one of the chemical biomarkers has been successfully applied as a sewage biomarker as it remains in the environment longer than microbial indicators and can be used to discriminate different sources of faecal pollution in sediments.In this study, we analysed the distribution of sterols in surface sediments of Langat River and evaluate the level of sewage pollution by using diagnostic ratios (biomarkers) and chemometric techniques. Sediment samples were collected from 22 stations along Langat River then extracted and analysed for sterols by using GC-MS instrument. Six different sterols were identified and quantified with total sterol concentrations ranging between 11.50 to 618.25 ng g-1 dry weight. The highest total sterol concentration was found at Sg. Balak (SL02) at 618.25 ng g-1 dry weight). This is a tributary of Langat River that is densely populated with residential and industrialised areas to identify the sources of sewage. Three types of diagnostic ratios were used; coprostanol/cholesterol, coprostanol/(coprostanol+ cholestanol) and epicoprostanol/coprostanol. From the results of the majority of the diagnostic ratios, it was found that sewage contamination was occurring in some of the sampling sites, the other sampling sites had low to moderate sewage pollution levels. The chemometric techniques led to a better understanding of the data in term of source of pollution. With the use of statistical analysis, the sterols compounds which act as different biomarkers were able to be separated and thus, different sources of sewage origin could be revealed. This is the first report on sewage pollution that is based on the combination of biomarkers and chemometric techniques that can established a new approach for sewage detection using faecal sterol and stanol.

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