Assessment of Impact of Human Activities on Tolerance of Soil Bacteria and Fungi to Cadmium (CD) in Some Parts of Rivers State, Nigeria
Lethal concentration 50 (LC50) of Cadmium (Cd) on bacteria and fungi was used to assess the impact of anthropogenic activity in development and distribution of Cadmium (Cd) tolerance among fungi and bacteria in three study areas; industrial, urbanized and agricultural. Soil samples were collected from the three study areas in replicate and total CFUs/g of soil determined by standard culturing in culture media with different concentrations of 10 ppm, 25 ppm, 50 ppm, 75 ppm, 100 ppm, 150 ppm of Cadmium (Cd) through standard procedures. Percentage of dead fungi and bacteria in each study concentration was determined, which were then converted to probits. Regression analysis was done, where the output of probit and regression analysis was used to calculate LC50. ANOVA of LC50 was done at 95% level of significance to determine the difference among the means of the study areas. The mean values of Total Petroleum Hydrocarbon (TPH) in soil ranged from 5.09±0.33 to 56.70±44.63 ppm. The highest levels of TPH were recorded in Eleme (A2) with a mean value of 56.70±44.63 ppm. The mean values of Cadmium in the soils of the study areas ranged from 0.023±0.015 to 0.057±0.012 ppm. The highest concentration of Cd that recorded growth was 150 ppm which was recorded at Onne (I2), Control (CA), Aluu (A1), Eleme (A2) and Emuoha (A3) which ranged from 1.00×102 to 1.00×102 CFUs/g of soil. There was significant difference in LC50 for fungi among the study sites, p=0.001. Pearson Correlation analysis of metals in the study sites against LC50 of Cd reveal that there was significant relationship between bacteria and Total Petroleum Hydrocarbon [TPH] (r=0.30). There was significant difference in LC50 among the study areas and control areas, [ANOVA, F(5,30) = 3.297 p = 0.017] for fungi and no significance for bacteria [ANOVA, F(5,30) = 0.246 p = 0.939]. The study identifies agricultural areas (CA and A3) among the study areas as vulnerable to pollution with TPH and Cd. The study concludes that fungi in the agricultural areas have developed higher tolerance to Cadmium (Cd) as compared to those in industrial and urban areas
Index Terms - Bacteria, Cadmium, Heavy metals, Fungi, Petroleum, Tolerance, Toxicity, LC50.