1. Lecture 9 SULFUR GES175, Science of Soils

2. Relevance of Soil Sulfur * Used in amino acids, vitamins * Plant Deficiency   small and spindly plants   yellowish leaves (new tissue) * Environmental Problems:  acidification - acid rain - sulfide oxidation Slide 9.2

3. Sulfur Cycle organic-S S -2 SO 4 -2 (S o ) 1. mineralization 2. Immobilization 3. Oxidation 3 4 4 4. reduction plants & animals Slide 9.3

4. S oxidation and reduction? Slide 9.4

5. Acid Mine Drainage

6. Result of Acid Mine Drainage

7. S oxidation and Reduction * Oxidation S -2  (O 2 )  SO 4 -2 * Autotrophic microorganisms  energy obtained from S oxidation * Acid producing process  S or S -2  H 2 SO 4 Slide 9.7

8. Reduction + e - + e - SO 4 -2  S o  S -2 * Anaerobic process   organisms use S in place of O 2 as a terminal e - acceptor  “sulfate reducing bacteria” (obligate anaerobes) Slide 9.8

9. Reduction (cont’d) * S -2 can be toxic   forms H 2 S gas   reacts with Pb, Cd, Zn  insoluble compounds * mostly, heterotrophic organisms   require OM for energy source Slide 9.9