Assessment of Heavy Metals Contamination on Soil Faunal Diversity in Selected Local Governments Areas of Jigawa State, Nigeria

Abstract

Heavy metal pollution in soils constitutes a highly complex disruption of ecological equilibrium because some are essential trace elements that become toxic when present beyond a certain concentration. The aim of this research is to assess the level of heavy metals contamination on soil faunal diversity in Dutse and Hadejia Jigawa State-Nigeria. The study employed multistage sampling techniques using 20cm² quadrants thrown at random. A modified  Baermann’s funnel method of extraction was used to extract the soil fauna from the soil samples and the specimens were properly examined for  identification under compound microscope. The collected soil samples were digested using concentrated HNO₃ and HCl. The digested samples were  analyzed for heavy metals using Atomic Absorption Spectrophotometer. The result revealed that a total of 275 individuals and 13 species, belonging to 5  classes and 4 phyla were identified from both study areas. Ants, termites, millipedes, earthworms and snails (Cornu aspersum) were found in both Dutse  and Hadejia. However, Beetles, wax worms, roundworms, burrowing nematodes and snails (Achantina fulica) were found only in samples from Hadejia.  There was no significant variation in abundance of most soil fauna (p> 0.05) extracted across the study sites, except for dung beetle, millipedes,  earthworm and roundworm. It also suggested a positive relationship between heavy metals and soil fauna density (r≥0.76), that is, the mean density of  soil fauna increased proportionally with increasing heavy metal concentration. Further study should be conducted to check whether the soil fauna  possibly resisted or adapt to the effect of the heavy metal or the concentration in the soil or inside the organisms is insignificant to have a negative effect  on their diversity.