Evaluation of heavy metals on soil microflora diversity in Robertkiri, Idama and Jokka in Niger Delta Area of Nigeria

Abstract

The increase in the population and industrial growth has led to increased production of industrial and domestic waste, which contains heavy metals in different forms, hence affect the diversity and activities of soil microflora and environmental sustainability. This research was aimed at evaluating the heavy metals on soil microflora diversity in soils of Robertkiri, Idama and Jokka in Akuku-Toru Local Government Area in River State Nigeria. Soil samples were collected randomly from each location at 0-15 and 15-30 cm depth, respectively. The heavy metal contents of soil were determined using standard methods, while the microbial analysis of samples was determined by the enumeration of total heterotrophic bacteria (THB) and fungi and hydrocarbon utilizing bacteria and fungi on plate count Agar at 37°C, and the count recorded after 4 h using standard methods. Results showed that Fe concentration was highest in the contaminated locations at 15-30 cm depth with values 1362.01, 894.01 and 674.11 mg/kg for Robertkiri, Idama and Jokka compared to 0-15 cm depth and the control. Similar trend was observed at 15-30 cm depth for Zn 33.61, 41.20 and 33.98 mg/kg within the study locations. Whereas Cu and Cr had lowest concentration of 0.49 and 0.78 mg/kg in Robertkiri, 0.74 and 1.17 mg/kg in Idama and 0.76 and 1.87 mg/kg in Jokka at 15-30 cm depth. The THB and total heterotrophic fungi (THF) count was relatively low and ranged between 0.59 and 2.85 cfu at 0-15 and 15-30 cm depth in Robertkiri and Idam. While at jokka, THB and THF count ranged between 0.23 and 1.94 cfu at 0-15 and 15-30 cm depth compared to control. Likewise, the hydrocarbon utilizing bacteria (HUB) and hydrocarbon utilizing fungi (HUF) count was found to be low across depth in all the three locations in relative to the control. The study revealed that there is a gradual accumulation of heavy metals and the concentration was high in the contaminated soils than the control. The low count of soil microflora in the study locations may be due to the high levels of heavy metals observed in the contaminated soils from different locations.