The suggestions so far have been aimed at removing inorganic S from
organic material, primarily sediments.  I'm wondering whether there
might be substantial inorganic S pools within plant and animal tissues that
you would want to preserve, but that would be lost with Cr reduction,
etc.?  I think the earlier comment by K Havenor is pertinent; which pools
represent physiological processing and which are direct products of the
microbial/chemical processes producing inorganic S outside the
organism?
Judith Stribling
Department of Biology
Salisbury State University
1101 Camden Ave.
Salisbury, MD  21801
(410)873-2091