Volatilization of Mercury by a Chlorella sp.: Influence of Light and Mercury (II) Speciation

Abstract

The adsorption and reduction characteristics of Hg²⁺ by a green alga, Chlorella sp. were investigated in the presence of Cl^- Volatilization of mercury was greatly affected by the concentration of Cl^- and rapid volatilization was observed at Cl^- concentration at which [HgCl₂] ⁰ complex was dominant. Toxicity of Hg²⁺ to Chlorella cells was also enhanced under the same conditions. Although the amount of Hg²⁺ adsorbed on the surface of the cells decreased with increasing Cl^- concentration, the amount of Hg²⁺ taken up into the cells increased with increasing distribution ratio of [HgCl₂] ⁰ complex in the system. These results indicate that the formation of [HgCl₂] ⁰ complex facilitated the uptake of Hg²⁺ into Chlorella cells, and hence, the rate of Hg²⁺ reduction under light irradiated conditions and the toxicity of Hg²⁺ to the cells were greatly enhanced.