Sulphate labile organic

Thus, pore water studies provide evidence that some trace elements (As, Co, Cr) become more soluble on redox dissolution of Mn-Fe oxides in marine and sediments. However, these studies have failed to detect a parallel release of trace elements (other than Co) with Fe and Mn during redox events (Sakata, 1985 Morfett et al., 1988 Achterberg et al., 1997). It appears that in spite of the loss of labile organic matter and oxides of Fe and Mn, the trace elements remain relatively immobile. In oceanic or estuarine sediments it has been proposed that sulphides have a role to play in fixing the trace elements under reducing conditions. This has also been demonstrated in sulphate-rich freshwater systems (Huerta-Diaz et al., 1998). However, Cu and Pb, at least, clearly remain firmly attached to freshwater sediment even in the absence of measurable sulphides, and where Mn and Fe are being actively released via reduction (Sakata, 1985). 

---