Level of Heavy Metals and Potential Ecological Risks in Irrigated Horticultural Farms in the Vicinity of Lake Ziway, Central Ethiopian Rift Valley Region

Table 5

Heavy metal concentrations (μg·L⁻¹) in water samples collected from the three sampling sites (n = 15; specific site for minimum and maximum values is indicated in bracket).

Heavy metals	Concentration (μg·L^−1) (mean ± SD)			RML (μg·L^−1)
	All sites (n = 15)	Min. value	Max. value
As	80 ± 10	50 (S3)	110 (S1)	100
Pb	570 ± 30	520 (S3)	610 (S1)	5000
Zn	170 ± 30	130 (S3)	200 (S1)	2000
Cd	6 ± 3	3 (S3)	9 (S2)	10
Hg	90 ± 20	60 (S1)	110 (S2)	—
Cu	140 ± 30	20 (S3)	180 (S1)	200
Ni	170 ± 10	110 (S1)	180 (S2)	200
Co	10 ± 4	8 (S3)	20 (S2)	50
Cr	50 ± 10	40 (S1)	69 (S2)	100

RML = recommended maximum limit for irrigation water of vegetable farms by FAO [50].