Lake sediments iron sulfide content

Figure 7. Only at the base of sediment cores from 27 lakes is a relationship (r2 = 0.755) observed between the iron content and the fraction of sulfur present as iron sulfides (AVS + CRS). A similar relationship is not observed in surface sediments. As discussed in the text, much of the sulfur at the base of the cores appears to have originated from organic compounds in seston. The relationship may indicate that retention of H2S released during decomposition of seston is determined by the availability of iron. References are...

If iron limits retention of S in sediments (cf. 50, 30) it would be expected that the fraction of S present as iron sulfides would increase with increasing Fe content of sediments. Although this relationship is observed in deep sediments (Figure 7), fractionation of S between organic and inorganic forms is not determined by iron content in surface sediments. Nor is there any relationship between Fe content and total S content in surface sediments for all lakes reported in the literature (Figure lc). In deep sediments where C S ratios indicate that seston was the major source of sedimentary sulfur... 

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