Analyses of intermediate products during degradation of pyrene in soil by hemoglobin-catalyzed reaction

Abstract

Hemoglobin (Hb) is a member of heme-protein that can perform catalytic non-specific chain reaction in the presence of hydrogen peroxide (H2O2). Catalytic ability of Hb to degrade pyrene was demonstrated using soil contaminated with 14C pyrene and 10 mg pyrene /kg soil. The composition of soil was similar to previously used soil except that it had lower organic carbon content. Bench scale laboratory tests were conducted in the presence of buffer only, H2O2 only, or Hb with H2O2 for 24 h. After 24 h reaction, 0.1 and 1.3% of 14C pyrene in contaminated soil were mineralized with H2O2 only or Hb plus H2O2. No mineralization to 14CO2 was detected with buffer only. Approximately 12.2% of pyrene was degraded in the presence of H2O2 only while 44.0% of pyrene was degraded in the presence of Hb plus H2O2 during 24 h of catalytic reaction. When degradation intermediate products were examined, two chemicals were observed in the presence of H2O2 only while 25 chemicals were found in the presence of Hb plus H2O2. While most degradation products were simple hydrocarbons, four of the 27 chemicals had aromatic rings. However, none of these four chemicals was structurally related to pyrene. These results suggest that Hb catalytic system could be used to treat pyrene-contaminated soil as an efficient and speedy remediation technology. In addition, intermediate products generated by this system are not greatly affected by composition change in soil organic matter content.