Environmental Contamination of Heavy Metals and Effects of Sediment Bacteria on Cadmium Speciation in the Vicinity of the Hwacheon Mine
In order to investigate the extent and degree of heavy metal contamination in soils and sediments influenced by past mining activities, and to estimate the effects of indigenous bacteria on Cd speciation and bioremoval efficiency in sediments according to the various environmental conditions, tailings, soils, waters and sediments were collected from the Hwacheon Au-Ag-Pb-Zn mine in Korea. Elevated levels of metals, i.e., 29 As mg/kg, 30 Cd mg/kg, 261 Cu mg/kg, 601 Pb mg/kg and 3128 Zn mg/kg were found in sediments. High concentrations of As and other heavy metals in soils, waters and sediments were found near the tailings piles. From the results of sequential extraction analyses with tailings and soils, a high proportion of Cd is present as non-residual fractions. This indicates that Cd is more mobile and bioavailable than Cu, Pb and Zn. For seasonal variation, the concentrations of As and other heavy metals were much more elevated in soils collected before rainy season than after rainy season. To estimate the bioremoval efficiency for Cd, bacteria which can adsorb Cd were isolated from sediments in this area. Microorganisms in sediments can alter the mobility of heavy metals and bacteria can leach heavy metals from sediments, adsorb them on their cell wall and accumulate them within an intracellular matrix. From the metal sorption tests with indigenous bacteria, the bioremoval efficiency of Cd in Cd single solution (10 ppm) was more than 90%. As well, the isolated bacterial strains exhibited a preferential metal sorption , i.e., Cd > Pb > Zn for single metal solutions and Pb > Cd > Zn for the mixed metal solutions. Therefore, the use of some microorganisms to remove heavy metals from contaminated sediments may represent an innovative purification process.
Kwang Hwa Chung, Yong Hyeon Shin, Sue-Nie Park, Hyun Sook Cho, Soon-Ae Yoo, Byung Joo Min, Hyo-Suk Lim and Kyung Hwa Yoo
S. E. Lee et al., "Environmental Contamination of Heavy Metals and Effects of Sediment Bacteria on Cadmium Speciation in the Vicinity of the Hwacheon Mine", Key Engineering Materials, Vols. 277-279, pp. 438-444, 2005