ABSTRACT
Population growth and industrialization of the world has dramatically increased the overall environmental load of heavy metals. The effects of pollution by heavy metals are not only an environmental problem but also a public health matter. In this study, raw water samples were collected from two sites (A and B) along river Kubanni, two sites (C and D) along river Galma and also at Zaria Dam (site E) all in Zaria, Nigeria. Vegetable samples (lettuce and tomato) were also collected from farmlands located along the banks of the rivers at sites where raw water samples were collected. Treated water samples were also collected from the public water supply in Zaria. For this purpose Zaria metropolis was divided into 8 zones (TA-TH). Sampling was done during the dry season (February to April 2006) and rainy season (August to October 2006). All the samples were analysed for lead, manganese and copper using the Atomic Absorption spectrophotometer (AAS). Lead and copper were not detected in any of the raw water samples analysed. However, manganese was detected in all the raw water sample analysed. In the dry season, manganese concentrations ranged from 0.58 � 0.28 mg/l to 2.52 � 1.65 mg/l while in the rainy season, the concentrations ranged from 0.12 � 0.05 mg/l to 5.36 � 0.26 mg/l. Lead and manganese were detected in all the vegetable samples analysed. The mean lead concentrations in the dry season ranged from 0.40 � 0.01 mg/l to 0.80 � 0.003 mg/l while in the rainy season the concentrations ranged from 0.38 � 0.01 mg/l to 22.6 � 0.07 mg/l. The mean manganese concentration in vegetable samples ranged from 0.1 � 0.003 mg/l to 0.3 � 0.006 mg/l in the dry season and 0.13 � 0.007 mg/l to 0.21 � 0.003 mg/l in the rainy season. Copper on the other hand, was only detected in samples contacted from just one site (site D) in the rainy season with concentration ranging from 9.5 � 0.12 mg/l to 9.7 � 1.2 mg/l. For the analysis of treated water samples, lead and copper were not detected. However, manganess was detected in all the samples analysed with the dry season recording concentrations ranging from 0.02 � 0.02 mg/l to 3.53 � 0.85 mg/l while the rainy season recorded 0.00 � 0.00 mg/l to 2.81 � 0.31 mg/l.