Bioaccumulation of priority trace metals in edible muscles of West African lungfish (Protopterus annectens Owen, 1839) from Nyabarongo River, Rwanda

Figures & data

Figure 1. Map of Rwanda showing the location of Nyabarongo river and the sampled stations. Inset is the location of Rwanda on the African continent. Adapted from.Karamage et al. (2016b)

Table 1. Heavy metal content of water from Nyabarongo river, Rwanda

Heavy metal	Kirinda bridge	Ruliba station	WHO guidelines (WHO, 2017)
Fe (mg/L)	0.63 ± 0.02	1.61 ± 0.03	NC
Mn (mg/L)	0.02 ± 0.002	0.53 ± 0.002	NC
Cu (mg/L)	BDL	0.24 ± 0.02	2.0
Zn (mg/L)	0.09 ± 0.01	BDL	3.0
Cr (mg/L)	0.06 ± 0.002	BDL	0.05
Cd (mg/L)	BDL	0.106 ± 0.002	0.003
Pb (mg/L)	0.75 ± 0.02	0.051 ± 0.01	0.01

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, Rwanda	Kirinda bridge	336.0 ± 0.70	302.6 ± 1.22	6.4 ± 0.26	44.7 ± 0.20	138.2 ± 0.17	BDL	302.4 ± 1.50	2020	This study
	Ruliba station	272.8 ± 0.36	292.2 ± 0.25	8.8 ± 0.36	135.2 ± 0.15	148.0 ± 0.21	BDL	432. 0 ± 0.50
Lower River Benue, Nigeria		0.36 ± 0.02	ND	ND	ND	ND	ND	0.09 ± 0.01	2018	(Ikape et al., 2018)
Oguta Lake, Nigeria		ND	ND	30.10	ND	3.75	0.41	18.10	2016	(Alinnor et al., 2016)
Nkisa river, Nigeria		174.66	11.81	4.92	211.33	1.03	0.79	0.98	2014	(Alinnor, 2014)
Benin city, Nigeria.		ND	ND	ND	ND	ND	0.32 ^F, 0.52^D	ND	2011	(Atuanya et al., 2011)
Anambra river, Nigeria		60.23 ± 0.37 ^a	0.94 ± 0.06	3.01 ± 0.40	10.60 ± 0.08	0.16 ± 0.03	ND	0.01 ± 0.02	2009	(Nwani et al., 2009)
		54.60 ± 0.20 ^b	1.00 ± 0.01	2.86 ± 0.31	11.40 ± 0.30	0.17 ± 0.02	ND	0.01 ± 0.02
FAO/WHO guidelines		NL	1.0	30.0	40.0	10.0	0.5	0.5		(FAO/WHO, 1989)

Notes: a and b-results in these rows were obtained in wet and dry seasons, respectively. BDL-below method detection limit. NL: No established guideline. ND-Not determined, F-Fresh sample, D-Dry sample. Values in bold are higher than their corresponding heavy metal permissible guidelines in fish.

Table 3. Bioconcentration factor of the heavy metals in P. annectens from Nyabarongo river, Rwanda

Location	Bioconcentration factor (L/kg)
	Fe	Mn	Cu	Zn	Cr	Cd	Pb
Ruliba station	169.0	551.3	36.7	NA	NA	NA	8,640
Kirinda bridge	533.3	15,130	NA	496.7	2,303.3	NA	403.2
Recommended limits (Karlsson et al., 2002)	200	500	200	1000	200	200	300

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