Sedimentary records of sewage pollution using faecal markers in contrasting pen-urban shallow lakes

Sewage contamination in shallow lake sediments is of concern because the pathogens, organic matter and nutrients contribute to the deterioration of the water-bodies' health and ecology. Sediment cores from three shallow lakes (Coneries, Church and Clifton Ponds) within Attenborough nature reserve located downstream of sewage treatment works were analysed for TOC, C/N, delta C-13, delta N-15, bacterial coliforms and faecal sterols. Pb-210 and Cs-137 activities were used to date the sediments. Elemental analysis suggests that the source of organic matter was algal and down profile changes in delta C-13 indicate a possible decrease in productivity with time which could be due to improvements in sewage treatment. delta N-15 for Coneries Pond are slightly higher than those observed in Church or Clifton and are consistent with a sewage-derived nitrate source which has been diluted by non-sewage sources of N. The similarity in delta N-15 values (+12 parts per thousand to +10 parts per thousand) indicates that the three ponds were not entirely hydrologically isolated. Analysis by gas chromatography/mass spectrometry (GC/MS) reveals that Coneries Pond had sterol concentrations in the range 20 to 30 mu g/g (dry wt.), whereas, those from Clifton and Church Ponds were lower. The highest concentrations of the human-sourced sewage marker 5 beta-coprostanol were observed in the top 40 cm of Coneries Pond with values up to 2.2 mu g/g. In contrast, Church and Clifton Pond sediments contain only trace amounts throughout. Down-profile comparison of 5 beta-coprostanol/cholesterol, 5 beta-coprostanol/(5 beta-coprostanol + 5 alpha-cholestanol) and 5 beta-epicoprostanol/coprostanol as well as 5 alpha-cholestanol/cholesterol suggests that Coneries Pond has received appreciable amounts of faecal contamination. Examination of 5 beta-stigmastanol (marker for herbivorous/ruminant animals) down core concentrations suggests a recent decrease in manure slurry input to Coneries Pond. The greater concentration of beta-sitosterol in sediments from Church and Clifton Ponds as compared to Coneries is attributed in part to their greater diversity and extent of aquatic plants and avian faeces. (C) 2010 Natural Environment Research Council. Published by Elsevier B.V. All rights reserved.