comparative study of tomatoes and onions form irrigated farmlnads on the bank of river challawa, kano, nigeria

the concentration of cu, mn, ni and zn were determined in tomatoes and onions samples using atomic absorption spectrometry. a total of 32 samples each of tomatoes and onions were collected from the exposed and control sites for analysis. the trace metals (cu, mn, ni and zn) concentration in tomatoes wee found to be 6.2406, 6.5521 , 5.7375 and 8.9297 mg/kg-1, respectively. while those of onions samples (exposed and control) are 8.250 for cu,7.9479 for mn, 10.8583 for ni and 98.7292 for zn; and 5.5698 for cu, 2.5156 for mn, 7.8813 for ni and 6.6573 mg/kg-1 for zn in respect of onions sample (control). the abundance of the trace metals followed the trend of zn > mn > cu > ni for tomatoes samples (exposed), zn > ni > cu > mn for onions samples (exposed) and ni > zn > cu > mn for the onions samples (control). the trace metals levels in the tomatoes and onions were found to be above the fao/who and who/eu allowed limits, which put the consumers of these vegetable crops at risk healthwise. however, the cu and zn values have not reached the maff limit