Geospatial Mapping, Environmetrics and Indexing Approach for a Tropical River Sediment in Southern Nigeria

Abstract

The objectives of this study are to assess the trace and heavy metals pollution in the sediments of Ossiomo river, using geospatial mapping, environmetrics and ecological risk indices. The results from the descriptive statistics showed that there was significant difference (P<0.05) of the mean values of Fe, Mn, Cu, Cr, Cd, Pb, Ni and V. A posterior analysis using Duncan multiple regression analysis showed that stations 2 and 3 were significantly different from stations 1 and 4. While, there was no significant difference (P>0.05) in the mean values of Zn across the stations. The results of the relationship of the metals revealed a negative correlation between Fe and Mn with the other metals correspondingly. The results of the Kriging interpolation indicated a strong bull eye colour for stations 2 and 3 (6.42), while stations 1 and 4 were minimal (1.4). The results of the geospatial mapping indicated Fe, Zn and Mn to be the most dominant metals across the stations. The results of the PCA (principal component analysis) yielded 16 variables under 9 components with Eigenvalues >1 in components 1- 6 and these variables explained 99.99 % of the total variance in the sediment. The results of the degree of suitability and sphericity of the PCA revealed a high significant difference at P<0.001. The results of the potential ecological risk index values were very high in station 2 (824.30) and 3 (802.11) correspondingly. That of index of geo-accumulation was generally low (< 2). The findings from this study generally revealed the source apportionment of the trace and heavy metals to come from anthropogenic influences such as farming; fertilizers. Sustainable agriculture is highly recommended in order to reduce the impacts of anthropogenic activities, deterioration of the ecosystem and possible death of the life forms in this watercourse.