Thesie (Ph.D.)--Chulalongkorn University, 2009

This research studied the diversity of active soil bacteria in cadmium (Cd) contaminated soil near zinc (Zn) mine at Mae Sot district, Tak province. The soil samples were collected from 4 creeks; Huai Mae Tao, Huai Mae Tao Ngae Sai, Huai Mae Ku and Huai Nong Khiao on May 2008. The total Cd and Zn quantities of the upstream samples of Huai Mae Tao were 8.45 and 193.05 mg/kg soil, respectively. Concentrations were increased to 16.85-22.50 and 954.00-1,998.00 mg/kg soil in the downstream (Ban Mae Tao Mai) samples. The Cd and Zn levels 3.05 and 97.45 mg/kg soil were found in the sample from Huai Mae Tao Ngae Sai, the north-eastern highland of the Zn mine. The metals concentration at Huai Mae Ku, the creek on the other side of the mountain, were 7.55-34.95 and 316.05-789.00 mg/kg soil whereas only 1.10 mg/kg soil of Cd and 27.05 mg/kg soil of Zn were found in a creek in the south-western highland. Cd was found negatively (inversely) correlated to only CEC in all soil (r = -0.749) at the 0.05 confidential level. The maximum Cd amount (34.95 mg/kg soil) was resulted in the highest soil bacterial diversity index (H). From Pearson correlation, the quantity of Cd was positively correlated to the bacterial diversity with correlation coefficient (r) of 0.768. Due to the DNA sequencing results, major group of bacteria was beta-proteobacteria and dominant strain was, Actinobacteria, Rhodococcus yunnanensis. Considering from bacterial community pattern by using DGGE, there were 2 bacterial strains, uncultured Aquicella sp. and Xenophilus sp., which might be used as an alternative detector for Cd in soil.