A Study on Soil Bacterial Population in Steel Company and Some Related Area in Erbil City in Relation to Heavy Metal Pollution

Abstract

Present study was conducted to investigate the impact of heavy metal pollution from Erbil steel company on soil physicochemical properties and bacterial population of surrounding soils. The highest bulk density, pH and total organic carbon were 0.774±0.001, 9.31±0.032, 36.447±0.005 g.Kg -1 respectively were observed inside Erbil steel company. The concentrations of all the metals were higher within the steel company in comparison with the other sites and the maximum values were 292±0.577, 8.4±0.208, 259±0.577 and 7480±0.866 ppm for Pb, Cd, Cu and Zn respectively. The concentrations of Cd, Cu and Zn in Erbil steel company soil are exceeded the permissible limits for soil. The isolated bacterial genera in Erbil steel company soil were Acinetobacter , Bacillus , Micrococcus , Neisseria , Pseudomonas and Staphylococcus . These isolates are considered tolerant to alkaline pH and elevated levels of heavy metals from the steel company. Minimum Arthrobacter spp. (0.32×10 5 ), proteolytic bacteria (0.57×10 5 ) and asymbiotic nitrogen-fixers (0.12×10 5 ) cfu.g -1 dry soil were in the soil of steel company and minimum bacterial population was observed in Nawroz soil (0.05×10 7 ) cfu.g -1 dry soil followed by Erbil steel company soil (0.06×10 7 ) cfu.g -1 dry soil. The relationships between the heavy metals and the microbial populations were negative. The correlations among: pH, total organic C, Cu, Pb and Zn were significantly positive.