Trace Metal Cycling and Fluxes in Sediments

Pb and Cs), commonly used for estimating sedimentation and particle-reworking rates (see chapter 7) in estuaries, with trace metals concentrations (Wen et al., 1999). These radionuclides can help constrain variability in the degree of reprocessing of trace metals across horizontal gradients as well as provide information on the historical accumulation of trace metals in estuaries (Ravichandran et al., 1995b). 

Another oxidant near the sediment-water interface capable of oxidizing Mn(II) is iodate (I03 ), which occurs in the dissolved form as well as adsorbed onto particles (Ullman and Aller, 1985). Iodine is known to be released in porewaters during the remineralization of organic matter (Ullman and Aller, 1983, 1985 Kennedy and Elderfield, 1987). Once produced, iodine is then believed to be oxidized to 103 through microbial processes, where it adsorbs onto metal oxides (Ullman and Aller, 1985). Recent work has shown that an iodide peak can be maintained in sediments through the reduction of 103 by Mn(II), with reoxidation of iodide to IO3 above the iodide peak thus, iodide production is adequate to account for the oxidation of all the upward diffusing Mn(II) via 1 ( 3 (Ansch u tz et al., 2000). 

The majority of trace metals are derived from igneous rocks, simply based on the relative fraction of igneous rocks in comparison to sedimentary and metamorphic rocks in the Earth s crust. 

The major inputs of trace metals to estuaries are derived from riverine, atmospheric, and anthropogenic sources. 

The partitioning of trace metals between the dissolved and particulate fractions in estuaries can be affected by variability in river flow, tidal and wind energy, storms, coagulation, and flocculation in the estuarine turbidity maximum (ETM), resuspension events (of sediments and porewaters), and inputs from wetland and mudflat processes. 

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