Mercury distribution, speciation and bioavailability in sediments from the Pearl River Estuary, Southern China

► Total Hg in the Pearl River Estuary surface sediments displayed large spatial variations. ► There was accelerating input of Hg into the Pearl River Estuary in the past decades. ► The organo-chelated and strong-complexed Hg were the dominant Hg species. ► The low extraction of Hg from sediments indicated the low bioavailability of Hg. ► Organic matter strongly influenced the concentration, distribution, and extractability of Hg.