| Abstract: | Utilization of mercury in gold mining in the tropics has contributed to large inputs of the metal into the aquatic environment. Although in this activity mercury is utilized in its elemental state, which is relatively immobile and inert, transformations to methylmercury occurring in natural systems lead to mercury contamination of aquatic organisms and the food chain. We investigated the effectiveness and mechanisms involved in the solubilization of mercury in the presence of humic acid, which is an important component of dark river waters in the tropics. Results showed that the solubility of elemental mercury was enhanced due to the presence of humic acid through a solubilization–complexation mechanism, which was attributed to the presence of acid sites on the humic acid molecule, mainly the carboxyl group. Calcium ions in solution prevent humic‐acid‐induced elemental mercury solubility. Although it was demonstrated that the mercury complex formed is more mobile in the presence of humic acid, preliminary results indicated that this mercury complex seem absorbed by fish. Copyright © 2000 John Wiley & Sons, Ltd. |
