2.3. Collection of plant samples for heavy metal analysis
Five plants were randomly selected from the middle row (to
avoid border effect) of each sub-plot at maturity to determine
heavy metals accumulation and pathogenic loading in edible parts
of the vegetables. After cleaning, the samples were grinded to fine
powder and dried at 60 C in an oven to a constant weight. Half
gram of each fine powdered samples were digested in a mixture of
4 ml, 25 ml, 2ml and 1ml of concentrated HClO4, HNO3, H2SO4 and
60% H2O2, respectively, at 100 C on a hot plate for 2 h in a fume
cupboard. The resulting solutionwas left over night and made up to
100ml by adding demonized distilledwater and the concentrations
of the elements were determined by atomic absorption spectrometer
(Pye Unicam SP9; Pye Unicam Ltd, Cambridge, UK). The
detection limit for these measurements is 0.02 mg kg1 for these
elements.
2.4. Bio-accumulation factor (BAF)
Bio-accumulation factor (BAF) is defined as the ratio of the
heavy metal concentrations in the plant tissue (root, stem or leaves)
to that in soil and was calculated as follows (Adesodun et al., 2010);