Assessing ecological risks and probable sources of Cu, Zn, and Mn in River Tana sediments, Kenya
2022
Githaiga, Kelvin | Njuguna, Samwel | Onyango, Janet | Yan, Xue
Current study aimed at finding the concentrations, ecological risks and probable sources of Cu, Zn, Mn and Fe heavy metals in River Tana surface sediments. Ecological risks were assessed using enrichment factors (EF) and potential ecological risk indices (PERI), while principal component analysis (PCA) was used to deduce the probable sources of the heavy metals. The average concentrations of Fe, Mn, Zn, and Cu (in mg/kg dry weight) were 338, 338, 4.71, and 2.23, respectively, and were below the permissible levels in sediments. The average Mn, Zn, and Cu enrichment was 63.2, 16.7, and 8.7, respectively. Based on the average EF, Mn was found to be extremely enriched while Cu and Zn enrichment was classified as significant. High Mn and Zn enrichment characterized the upper catchment areas compared to downstream. Cu was more enriched in the upper catchment and mid regions where extensive agriculture was practiced. However, the maximum recorded PERI was 4.13, therefore indicating low potential ecological risks. PCA analysis resulted to two principal components (PC). PC1 was loaded with Fe, Mn and Zn that was sourced from natural sources. PC2 contained Cu, which was sourced from anthropogenic activities including urban runoff, vehicular emissions and use of agricultural-based chemicals.
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