Kinetic Study of Biodangerous Methylmercury Degradation under Various Light Conditions

Abstract

Methylmercury (MeHg) has remarkable toxicological effects on humans, plants, and other lives in the environment, which may restrict the comprehensive utilization of biomass source in view of possibly forming biohazardous waste. In this study, a kinetic study of MeHg degradation under UVB, UVA, natural light, and dark was carried out. The result showed that light radiation enhanced MeHg degradation but had no significant influence on the final balance between MeHg and inorganic mercury (Hg2+) in pure water. The balance is of great importance and can be used as a key fundamental to estimate MeHg cycling in other complicated aquatic environments. MeHg degradation was identified to be second-order reaction using the fitting optimization level of the regression equation, and the second-order rate constants were 1.61, 0.82, and 0.91 L·ng−1·d−1, half-lives were calculated to be 0.62, 1.3, and 1.08 d for UVB, UVA, and natural light, respectively. A possible MeHg degradation mechanism was proposed, and it could perfectly explain the results obtained in this paper and some previous studies.