Heavy metal concentration and identification of microorganisms in soil under roadside trees of Daejeon city, Korea

Due to the rapid urbanization and scarcity of land, most of metropolitan city of Korea are subjected to many potential pollution sources, including vehicle exhaust and industrial emissions. Soil samples were collected under roadside trees, Platanus occidentalis. and Ginko biloba, to study the current conditions of heavy metal contamination and microorganism in Daejeon city, one of the metropolitan city in Korea. The total concentrations of heavy metals in the samples were determined. The results indicate that soils of roadside trees in Daejeon city have elevated concentrations of Cd, Cu, Zn, and Pb. Especially, high metal concentrations in soil were found in old urban commercial district and heavy traffic areas, indicating that the major contamination sources in these soils are traffic emissions. Rhizosphere bacteria in soil of roadside trees in Daejeon area were characterized in that strain richness was lower than other soil samples. Bacterial community members were characterized by DNA sequence analysis of 16S rDNA gene fragments following colony's DNA isolation emerged from nutrient agar medium using dilution plate method after soil sampling, polymerase chain reaction amplification and sequencing. Phylogenic analyses revealed that 16S rDNA sequences were classified β-Proteobacteria, Actinobacteria, Gram-positive bacteria group. Among three study sites, Daejeon station, Daedeok science town, and Daehwa industrial complex, Daehwa industrial complex's soil microbe's richness was lowest. The 16S rDNA sequence and fragment database constitutes a reference to which DNA profiles of roadside tree soil's bacterial communities can be compared.