Heavy metals risk assessment of water and sediments collected from selected river tributaries of the Mara River in Tanzania

Abstract

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 five 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 coefficient 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 significant correlation with Cd (r = 0.92, p < 0.01) in sediments. The analysis of environmental risks indicated significant 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.

Assessment of toxic metal contamination, distribution and risk in the sediments from lagoons used for fish farming in the central region of Peru

“…The mean concentration of As (Tranca Grande: 4.62 ± 0.24, Tipicocha: 6.95 ± 0.57, Pomacocha: 3.27 ± 0.45 mg kg −1 ) and Cd (Tranca Grande: 0.18 ± 0.01, Tipicocha: 0.18 ± 0.01, Pomacocha: 0.17 ± 0.01 mg kg −1 ) exceeded upper continental crustal reference values (UCC) (As: 1.5 and Cd: 0.098 mg kg −1 ). These results are similar to those obtained by [45] who reported As and Cd concentrations in sediments higher than the interim sediment quality guidelines. The high concentration of As in lake sediments could be attributed to anthropogenic activities such as intensive fish farming and agriculture that misuse arsenic fertilizers and pesticides [7] and Cd could be due to low input from streams to lagoons causing precipitation of Cd in the sediments, increasing its concentration [34] .…”

Source and Distribution of Heavy Metals in Sediment Samples from Select Creeks of the Highly Urbanized Metro Vancouver Watersheds, Canada

“…The concentrations of heavy metals in the sampling area were also compared to background values [19], Table 4. It was observed that apart from Bon Accord Creek (MVC4), all the sampling sites in the study area had at least one heavy metal above the background level (Table 4), suggesting that there were probably some anthropogenic inputs at the sites [34]. According to results in Table 4, Bolivar Creek (MVC25) and Beaver Creek (MVC33) had at least nine heavy metals at each site above the TEL/LEL hence these sites were considered the most polluted.…”

“…Also, the analysis of various pollution indices used in the present study for sediment quality addresses the gaps that exist in the literature in the study area. According to Harikumar et al, [5] as cited by Nkinda et al, [34], pollution indices are powerful tools for evaluating, developing, and conveying raw environmental data into more meaningful information for politicians and decision-makers.…”

Spatial-Temporal Variations for Pollution Assessment of Heavy Metals in Hengshui Lake of China

“…where PRI is the potential ecological risk index of multiple heavy metals; E r i is the risk factor of heavy metal i; T r i is the toxic coefficient of heavy metal i (i.e., Cd = 30, Hg = 40, As = 10, Pb = Cu = 5, Cr = 2, and Zn = 1) [4,15,21,22]; C i is the same as in Equation (1); C i B is the geochemical background value of i, which was used the average value of surface soil in Hebei province [23]. According to the value of E r i and PRI, the degree of potential ecological risk can be divided into different levels (Table S3).…”