Abstract

 
 
 Intensified urbanization and industrialization are rapidly triggering the release of pollutants to the environment. This study determined the extent of soil contamination with Nickel (Ni) in oil mining areas and its effect on the levels of Ni tolerance by fungi and bacteria. The total CFUs/g of soil were enumerated after a culture period of 7 days at 28°C and LC50 was determined using probit and regression analysis. The mean values of Ni were 1.38±0.23 in industrial area, 1.41±0.36 ppm in agricultural area and 1.02±0.64 in urban area. The mean values of Total Petroleum Hydrocarbon (TPH) were 4,405.46 ppm in industrial area, 55.65 ppm in agricultural area and 1,304.53 ppm in urban area. Nickel’s peak concentration indicating growth of both fungi and bacteria at 150 ppm. There was significant difference (p ≤ 0.000) in the mean levels of LC50 for fungi among the study sites. There was no significant correlation between the concentration of TPH in soil and LC50 of fungi (r = -0.169) and bacteria (r = 0.042). In conclusion, TPH influenced the levels of fungi and bacteria tolerance to Ni in soils. Moreover, it was observed that LC50 can be a reliable method for monitoring chemically resistant microorganisms directly in the environment to improve the use of microorganisms for the bioremediation of oil contaminated soils and in monitoring of antibiotic resistant microorganisms in natural ecosystems.
 
 
Highlights
Identified as Ni transporters in microbial cells for example in Yersinia pseudotuberculosis and Brucella suis (Jubier-Maurin et al, 2001; Sebbane et al, 2002; Eitinger et al, 2005)
Microbial count for the soil and levels of Lethal Concentration 50 (LC50) Table 2 shows the observations of mean fungal colony forming units per gram (CFUs/g) of soil in the study sites
There was no significant correlation between the concentration of Total Petroleum Hydrocarbon (TPH) in soil and LC50 for fungi (r = -0.169) and bacteria (r = 0.042) (Table 4)
Summary
Identified as Ni transporters in microbial cells for example in Yersinia pseudotuberculosis and Brucella suis (Jubier-Maurin et al, 2001; Sebbane et al, 2002; Eitinger et al, 2005). Microorganisms are non-vertebrates and provide an alternative approach to use of animals in environmental monitoring. This approach is gaining popularity because they are relatively quick, replicable, cheap and do not attract ethical issues (Rotini et al, 2017; Mortensen et al, 2018). There are other factors that contribute on availability and resilience of microorganisms in soil. The toxic range of a substance may be tested to determine its toxicity range. This study adopted the Finney, 1952 method where percentage deaths of CFUs/g of soil were determined and linear regression analysis was used to determine LC50 (Manguilimotan & Bitacura, 2018). The objective of this study is to determine the impact of oil spills to Ni levels on the Greater Port Harcourt Area soils
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