J.M. Suflita J.P. McKinley L.R. Krumholz D. Wong 2004 <p><span>Previous studies have shown that sulfate-reduction activity occurs in a heterogeneous manner throughout the terrestrial subsurface. Low-activity regions are often observed in the presence of clay minerals. Here we report that clays inhibit sulfate reduction activity in sediments and in a pure culture of </span><i class="EmphasisTypeItalic ">Desulfovibrio</i><i class="EmphasisTypeItalic ">vulgaris</i><span>. Clay minerals including bentonite and kaolinite inhibited sulfate reduction by 70–90% in sediments. Intact clays and clay colloids or soluble components, capable of passing through a 0.2-µm filter, were also inhibitory to sulfate-reducing bacteria. Other adsorbent materials, including anion or cation exchangers and a zeolite, did not inhibit sulfate reduction in sediments, suggesting that the effect of clays was not due to their cation-exchange capacity. We observed a strong correlation between the Al</span>₂<span>O</span>₃<span>content of clays and their relative ability to inhibit sulfate reduction in sediments (</span><i class="EmphasisTypeItalic ">r</i>²<span> = 0.82). This suggested that inhibition might be a direct effect of Al</span>³⁺<span> (aq) on the bacteria. We then tested pure aluminum oxide (Al</span>₂<span>O</span>₃<span>) and showed it to act in a similar manner to clay. As dissolved aluminum is known to be toxic to a variety of organisms at low concentrations, our results suggest that the effects of clay on sulfate-reducing bacteria may be directly due to aluminum. Thus, our experiments provide an explanation for the lack of sulfate-reduction activity in clay-rich regions and presents a mechanism for the effect.</span></p> application/pdf 10.1007/s00248-003-1021-z en Springer-Verlag Impact of clay minerals on sulfate-reducing activity in aquifers article