14C/12C ratios as tracers of urban pollution

Since fossil carbon is '14C-free', environmental materials influenced by industrial activity have 14C/12C ratios which are measurably depressed below natural values. In this study 14C/12C ratios in samples from an industrial region are compared with those in relatively unpolluted materials. It is shown that artificial sedimentation rates in the coastal sewage dumping area off the West of Scotland are an order of magnitude higher than the natural rate for this region. The 14C/12C ratio in the normal industrial atmosphere shows that up to 20% of the total carbon dioxide content is derived from local combustion of fossil fuels. This may be compared with a circa 6% contribution on a world wide basis. (author)