Influence of electrical conductivity on microorganisms and rate of crude oil mineralization in Niger Delta ultisol

Abstract

The effect of salinity on the population density of hydrocarbonoclastic microorganisms and oil degradation in a tropical ultisol was determined. Soils were simulated with 50gkg-1 of Qua Iboe Light (QIL) crude oil. Salt treatments included NaCI amendments to adjust the soil solution electrical conductivities (EC) to 40, 120 and 200 dSm-1. Treated soils were incubated at 28OC. Oil degradation was estimated from the gravimetric determinations of remaining oil. The results showed that amending the ultisol with crude oil stimulated the growth of oil degrading microorganisms, while salt concentration inducing an EC of 200 dSm-1 in oil amended ultisol resulted in a decrease in the amount oil mineralized. A significant positive correlation was found between the number of hydrocarbonoclastic microorganisms and levels of oil mineralization at EC 40 dSm-1 (r = 0.980, P = 0.05) and EC 120 dSm-1 (r = 0.976. P = 0.05) except at EC 200 dSm-1 (r = 0.855, P = 0.05). This is an indication that desalting of soils contaminated with oil and salts is required for a speedy bioremediation of an ultisol.


Key words: Electrical conductivity, crude oil, hydrocarbonoclastic microorganismineralization.


(Global Journal of Pure and Applied Sciences: 2003 9(4): 475-480)