Table 2.
Heavy metal concentrations in P. annectens from Nyabarongo river in comparison with other global studies
| Study area | Mean heavy metal concentration (mg/kg) | Year | Authors | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Fe | Mn | Cu | Zn | Cr | Cd | Pb | |||
| Nyabarongo river, Rwandaa | 272.8 ± 0.36 (336.0 ± 0.70) | 292.2 ± 0.25 (302.6 ± 1.22) | 8.8 ± 0.36 (6.4 ± 0.26) | 135.2 ± 0.15 (44.7 ± 0.20) | 148.0 ± 0.21 (138.2 ± 0.17) | BDL (BDL) | 432. 0 ± 0.50 (302.4 ± 1.50) | 2020 | This study |
| Lower River Benue, Nigeria | 0.36 ± 0.02 | ND | ND | ND | ND | ND | 0.09 ± 0.01 | 2018 | [15] |
| Oguta Lake, Nigeria | ND | ND | 30.10 | ND | 3.75 | 0.41 | 18.10 | 2016 | [16] |
| Nkisa river, Nigeria | 174.66 | 11.81 | 4.92 | 211.33 | 1.03 | 0.79 | 0.98 | 2014 | [17] |
| Benin city, Nigeria. | ND | ND | ND | ND | ND | 0.32F, 0.52D | ND | 2011 | [18] |
| Anambra river, Nigeria | 60.23 ± 0.37b | 0.94 ± 0.06 | 3.01 ± 0.40 | 10.60 ± 0.08 | 0.16 ± 0.03 | ND | 0.01 ± 0.02 | 2009 | [19] |
| 54.60 ± 0.20c | 1.00 ± 0.01 | 2.86 ± 0.31 | 11.40 ± 0.30 | 0.17 ± 0.02 | ND | 0.01 ± 0.02 | |||
| FAO/WHO limit | 30.0 | 1.0 | 30.0 | 40.0 | 10.0 | 0.5 | 0.5 | [20] | |
Detection limits calculated with reagent blanks were 1.50, 0.20, 0.60, 2.50, 0.50, 1.14, 1.20 and 0.37 mg/kg for Fe, Mn, Cu, Zn, Cr, Cd and Pb, respectively. Values in italics are higher than their corresponding heavy metal permissible limits in fish
ND not determined, F fresh sample, D dry sample, BDL below method detection limit
aResults in parentheses are for P. annectens from Kirinda bridge; b, c results in these rows were obtained in wet and dry seasons respectively