Effect of Kawrgosk Oil Refinery on Some Physicochemical Characteristics, Microbial Population and Biochemical Properties of Surface Soils

Abstract

Effect of Kawrgosk Oil Refinery byproducts on physicochemical, microbiological and certain soil enzymes was studied. Contamination of the Refinery affected physicochemical, biological and enzymatic properties of soil. Soil pH slightly increased to 8.42±0.173, moisture content and organic matter were significantly lower than control 0.84±0.116 % and 15.04±0.301 g.Kg -1 respectively. Refinery contamination caused reduction in bacterial population to 0.04×10 7 cfu.g -1 dry soil and fungal population to 2×10 3 cfu.g -1 dry soil and reduced dehydrogenase activity to 0.020 TPF µg.g -1 when compared to control. Whereas, the Refinery contamination was increased oil residue to 2.6±0.000 µg.kg -1 , Fe to 31.50±0.433 g.kg -1 , Ni to 0.116±0.002 g.kg -1 , As to 0.300±0.003 g.kg -1 and Cd to 0.227±0.002 g.kg -1 in comparing with control. The ranges of soil enzymes were: dehydrogenase 0.020-157.651 TPF µg.g -1 in both Tobzawa and Agholane Gichka soils; urease 162-396.96 µg N-NH4 + .g -1 in both Jideda Zab and Agholane Gawra soils; nitrate reductase 3.126-4.658 µg N-NO2.g -1 in Agholane Gichka and Jideda Zab soils; whereas, catalase 0.5-1 ml KMnO4.g -1 .20 min -1 in both Girdarasha and Tobzawa soils respectively. Significant positive correlation (r= 0.582 at p<0.05) between total bacteria and organic matter was observed. Highly positive correlation (r= 0.863 at p<0.01) between total bacteria and dehydrogenase activity was observed. A negative correlation among: the studied heavy metals with dehydrogenase and nitrate reductase; oil residues, microbial population with dehydrogenase, urease and catalase activities were other findings of the study. Higher dehydrogenase activity was observed in sandy soils than loamy soils in Agholane Gawra, Kawrgosk and Agholane Gichka soils which have higher sand contents 63.77, 69.29 and 68.25% respectively.