1. GES175, Science of Soils
Lecture 9
SULFUR

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

3. Sulfur Cycle Slide 9.3 plants & animals SO4-2 2. Immobilization 4
organic-S 3
4. reduction
(So)
S-2
1. mineralization
3. Oxidation

4. S oxidation and reduction?
Slide 9.4
S oxidation and reduction?

5. Acid Mine Drainage

6. Result of Acid Mine Drainage

7. S oxidation and Reduction
Slide 9.7
S oxidation and Reduction
* Oxidation
S-2 ¾(O2)® SO4-2
* Autotrophic microorganisms
u energy obtained from S oxidation
* Acid producing process
u S or S-2 ¾® H2SO4

8. Reduction SO4-2 ¾¾® So ¾¾® S-2 * Anaerobic process
Slide 9.8
Reduction
+ e e-
SO4-2 ¾¾® So ¾¾® S-2
* Anaerobic process
u organisms use S in place of O2
as a terminal e- acceptor
u “sulfate reducing bacteria”
(obligate anaerobes)

9. * mostly, heterotrophic organisms
Slide 9.9
Reduction (cont’d)
* S-2 can be toxic
u forms H2S gas
u reacts with Pb, Cd, Zn Þ
insoluble compounds
* mostly, heterotrophic organisms
u require OM for energy source