Speciation and concentrations of mercury in certain coastal marine sediments (original) (raw)
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Marine and Freshwater Research, 2009
On reaching the sea, mercury discharged into the environment is deposited on and buried in marine sediments. Diagenetic processes in sediments lead to changes in both mercury concentration and speciation; they may enhance mercury bioavailability and/or lead to mercury remobilisation. Total concentrations and speciation of mercury were measured in dated sediment samples from sites covering a range of different environmental conditions and mercury concentrations. In the course of ~200 year-long diagenetic processes, the dominant changes in mercury speciation have involved diffusion of labile mercury to the overlying water, transformation of organic-bound mercury to HgS under anoxic conditions or to insoluble humin-bound Hg under oxic conditions, and dismutation of HgS into soluble polysulfides under hyperanoxic conditions. Rate constants of labile-to-stable mercury species transformations and the return flux of mercury were calculated on the basis of sediment core geochronology obtain...
Environmental science & technology, 2015
The concentrations and isotopic compositions of mercury (Hg) in surface sediments of the Pearl River Estuary (PRE) and the South China Sea (SCS) were analyzed. The data revealed significant differences between the total Hg (THg) in fine-grained sediments collected from the PRE (8-251 μg kg(-1)) and those collected from the SCS (12-83 μg kg(-1)). Large spatial variations in Hg isotopic compositions were observed in the SCS (δ(202)Hg, from -2.82 to -2.10‰; Δ(199)Hg, from +0.21 to +0.45‰) and PRE (δ(202)Hg, from -2.80 to -0.68‰; Δ(199)Hg, from -0.15 to +0.16‰). The large positive Δ(199)Hg in the SCS indicated that a fraction of Hg has undergone Hg(2+) photoreduction processes prior to incorporation into the sediments. The relatively negative Δ(199)Hg values in the PRE indicated that photoreduction of Hg is not the primary route for the removal of Hg from the water column. The riverine input of fine particles played an important role in transporting Hg to the PRE sediments. In the deep ...