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

The purpose of this study was to investigate the importance of both natural and anthropogenic sources of organic matter in bottom sediments of the For th Estuary, east Scotland, U.K. Organic matter from the upper, middle and l ower zones of the estuary was characterized using stable isotope (delta C-1 3 and delta N-15) and elemental (C/H and C/N) ratios. The observed narrow r ange of isotopic and elemental ratio data, over the entire length of the es tuary, was consistent with relatively efficient mixing of sediments, althou gh delta C-13 values of -23.6 parts per thousand and C/H ratios of 3.9 +/- 0.3 for lower estuary sediments did suggest a change to a more marine-influ enced system. delta N-15 and C/N ratios could not be used, however, to indi cate either the source or the fate of sediment organic matter. No specific anthropogenic source could be identified on the basis of elemental and/or s table isotopic information. (C) 2001 Academic Press.