Assessment of Spatial Variability of Heavy Metals in Soils under the Influence of Industrial Soap and Detergent Waste Water Discharge

Soil heavy metals have been a very useful indicator of environmental quality worldwide. The present study was conducted to investigate the levels, sources, distribution and spatial variability of heavy metals (Cu, Mn, Cd, Pb, and Zn) in soils in close proximity to an industrial area. Hierarchical Cluster Analysis (HCA) was applied to test the similarities between sampled elements based on nearest neighbour method. Mean concentrations (mg/L) of heavy metals in the sampled soils were as follows: Mn (19.90), Cu (15.23), Zn (9.06), Pb (6.19) and Cd (0.13). ANOVA showed that the concentrations of individual heavy metals in soils were significantly higher (P < 0.05) than the background reference soils indicating that the effluent discharge from the industry has increased the heavy metal concentrations in these soils. A strong positive correlation was found between Cu, Zn, Pb and Cd whereas Mn was positively correlated somewhat less strongly to Zn and Pb. Mn was negatively correlated with Cu and Cd. The results indicate that the concentrations of all metals except Cd exhibited weak spatial autocorrelations (ratios ranging from 0.80 to 11.94) confirming that spatial variability was affected by the industrial effluent discharge. These results suggest the need to develop proper management strategies to contend with heavy metal contamination in industrial areas.