Case Study: Microbial Ecology and Forensics of Chinese Drywall-Elemental Sulfur Disproportionation as Primary Generator of Hydrogen Sulfide

Abstract

Drywall manufactured in China released foul odors attributed to volatile sulfur compounds. These included hydrogen sulfide, methyl mercaptan, and sulfur dioxide. Given that calcium sulfate is the main component of drywall, one would suspect bacterial reduction of sulfate to sulfide as the primary culprit. However, when the forensics, i.e., the microbial and chemical signatures left in the drywall, are studied, the evidence suggests that, rather than dissimilatory sulfate reduction, disproportionation of elemental sulfur to hydrogen sulfide and sulfate was actually the primary cause of the malodors. Forensic evidence suggests that the transformation of elemental sulfur went through several abiological and microbial stages: (1) partial volatilization of elemental sulfur during the manufacture of plaster of Paris, (2) partial abiotic disproportionation of elemental sulfur to sulfide and thiosulfate during the manufacture of drywall, (3) microbial disproportionation of elemental sulfur to sulfide and sulfate resulting in neutralization of all alkalinity, and acidification below pH 4, (4) acidophilic microbial disproportionation of elemental sulfur to sulfide and sulfuric acid, and (5) hydrogen sulfide volatilization, coating of copper fixtures resulting in corrosion, and oxidation to sulfur dioxide.