BIOMARKERS ASSOCIATED WITH SEWAGE IN THE ARADE ESTUARY, PORTUGAL

A study of the biomarkers associated with human sewage was conducted o n the Arade Estuary and its tributaries, the R. de Boina and Odelouca, Southern Portugal. Surface sediment samples were collected at 20 site s in the system and analysed by gas chromatography - mass spectrometry (CC-MS) for sterols and fatty alcohols. The coprostanol/cholesterol r atio indicated substantial sewage contamination in the Boina and in th e lower reaches of the Arade Estuary. The lack of epi-coprostanol sugg ested that this material was essentially untreated. Other sterols (bet a-sitosterol and brassicasterol) indicate phytoplankton biomass in the middle and upper reaches of the estuary. The fatty alcohols were not correlated with the beta-sitosterol, unlike the brassicasterol, and th erefore suggest an algal origin for this matter. Organic matter derive d from vascular plants (high C22/C16 ratio) was limited to the central portion of the Estuary where a marsh-like community has developed.