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This study investigated the levels of Pb, Hg, Cr, Cd, and As in water and sediments from the tributaries of the Mara River,
Tanzania. Pollution risk of water and sediments was investigated using seven indices and fve metals. During the dry
period, the highest concentration of Pb, Hg, Cr, Cd, and As in sediments was 17.45 ±1.22, 0.01, 1.56±0.5, 1.3±0.09, and
30.81±0.02 mg/kg, respectively. During the wet period, the highest concentration of Pb, Hg, Cr, Cd, and As in sediments
was 4.37±0.28, 0.012, 2.58±0.57, 2.25±0.35, and 53±0.02 mg/kg, respectively. For surface water, the respective highest concentrations of Pb, Hg, Cr, Cd, and As were 0.76±0.09, 0.04, 0.68±0.09, 0.74±0.1, and 0.47±0.06 mg/L for the
dry period. The wet period max concentrations for Pb, Hg, Cr, Cd, and As in surface water were 0.56, 0.03, 0.55±0.03,
0.48±0.03, and 0.4±0.03 mg/L, respectively. Principal component analysis results indicated dominant loadings for Pb
and As in sediments during the dry period. Comparison of sediment concentrations with sediment quality guidelines
revealed that As and Cd were enriched. Correlation coefcient results indicated that As had a strong negative correlation
with the rest of the elements in sediments during the dry period. In the wet period, As had a signifcant correlation with
Cd (r=0.92, p<0.01) in sediments. The analysis of environmental risks indicated signifcant enrichment of sediments
with As and Cd. It is important to put in place relevant control mechanisms targeting metals in the studied tributaries,
with a focus on As and Cd. |
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