C. Alewell et M. Novak, Spotting zones of dissimilatory sulfate reduction in a forested catchment:the S-34-S-35 approach, ENVIR POLLU, 112(3), 2001, pp. 369-377
The localization of sulfate reducing sites in forested catchments is of maj
or importance, because dissimilatory sulfate reduction can be a considerabl
e sink for deposited sulfate. To localize dissimilatory sulfate reduction s
ites in a forested catchment (northeastern Bavaria, Germany), three sites w
ithin the catchment (upland site, intermittent seep, fen) were investigated
for delta S-34 depth profiles of soil sulfur and potential sulfate reducti
on rates were measured with S-35 radiolabeling. Stable sulfur isotopes indi
cate that aerobic metabolism is the dominant process on the upland site and
the intermittent seep (delta S-34 Of soil sulfur between + 1.6 and + 9.0 p
arts per thousand) and dissimilatory reduction is not a significant sink fo
r sulfate. However, results of the S-35 radiolabeling indicated for the upl
and site that the soil has potentially high sulfate reduction rates under l
aboratory conditions. Soil sulfur of the fen was markedly depleted in S-34
(delta S-34 between -6 and +2.6 parts per thousand). Both, S-34 and S-35 da
ta indicated that dissimilatory sulfate reduction is an ongoing process on
this site. The S-34 and S-35 approaches are complementary. While measuremen
ts using S-35 can show momentary potential for dissimilatory bacterial sulf
ate reduction, delta S-34 data reflect long-term predominance of either ass
imilatory or dissimilatory S metabolism at a particular site. (C) 2001 Else
vier Science Ltd. All rights reserved.