A Study of Carbon and Nitrogen Stable Isotope and Elemental Ratios as Potential Indicators of Source and Fate of Organic Matter in Sediments of the Forth Estuary, Scotland

Abstract

The purpose of this study was to investigate the importance of both natural and anthropogenic sources of organic matter in bottom sediments of the Forth Estuary, east Scotland, U.K. Organic matter from the upper, middle and lower zones of the estuary was characterized using stable isotope (δ13C and δ15N) and elemental (C/H and C/N) ratios. The observed narrow range of isotopic and elemental ratio data, over the entire length of the estuary, was consistent with relatively efficient mixing of sediments, although δ13C values of −23·6‰ and C/H ratios of 3·9±0·3 for lower estuary sediments did suggest a change to a more marine-influenced system. δ15N and C/N ratios could not be used, however, to indicate either the source or the fate of sediment organic matter. No specific anthropogenic source could be identified on the basis of elemental and/or stable isotopic information.