a new yield multiplicative model for simultaneous phytoextraction of ni and cd from contaminated soils

abstract soil contamination by heavy metals is yet one of the most important environmental concerns. among heavy metals, nickel and cadmium have dangerous influences on human, animals and plants. the objective of this study was to derive a new model for simultaneous phytoextraction of ni and cd from contaminated soils. consequently, a macroscopic model was derived by combining yield reduction functions and relative concentrations of ni and cd in plant tissues. to verify the derived model, a clay loam soil was simultaneously contaminated with different concentrations of ni and cd. the ornamental kale seeds were then seeded in these packed contaminated soils in three replicates. plants were harvested after full development. the ni and cd contents of soil samples and plant materials were extracted by 4m hno3 oxidation and wet oxidation methods, respectively. the ni and cd concentrations were measured by atomic absorption spectrometer (shimadzu, aa 670-g) and inductively coupled plasma optical emission spectrometry (varian vista-pro). the results indicated that relative yield of ornamental kale in the contaminated soils with both ni and cd was reduced more than the soil polluted with separate cd or ni. the results also indicated that at any given soil cd concentration, the ni content of ornamental kale increases with increasing soil ni concentration. meanwhile, with increasing soil cd, the ni content in ornamental kale was decreased. further, at any given cd content, the amount of cd in ornamental kale was increased by increasing ni concentration in soil. the results further indicated that the proposed model can well predict ni phytoextraction from soils contaminated with both ni and cd. however, this model could only provide an overall estimate for cd phytoextraction. it was further concluded that ornamental kale due to its high biomass production and high tolerance to ni and cd concentrations can be used to remediate low to moderate combined ni -cd contaminated soils.