The Hg policy restricting Hg usage in Ghana since 1989 has contributed to the recent marginal decline of Hg in the sediment.
The study took a retrospective look at these contaminations by conducting sediment core analysis of heavy metals in sediments collected from Lake Amponsah in the Bibiani district. Results The Lake was found to be undergoing sedimentation at an average rate of 1.76 cm/y.
There was marginal decline in Hg concentrations over the past two decades (from the 1990s to 2010s), while the other metals showed relatively increasing trends.
Cs can be used to date the most recent past, under ideal circumstances as far back as 120–150 years.
However, some obvious (and some less obvious) requirements need to be fulfilled for the dating-methods to be applicable and estuaries are often challenging environments in this respect.
The discussion is illustrated with examples from tidal flat, salt marsh and fjord sediments from temperate settings but the problems are universal and should be equally relevant for estuarine settings in other climatic zones.