Modelling sulphate-enhanced cadmium uptake by Zea mays from nutrientsolution under conditions of constant free Cd2+ ion activity
Ulrico J. L′opez-Chuken , Scott D. Young
DOI:
Received April 06, 2009,Revised July 07, 2009, Accepted , Available online
Volume 22,2010,Pages 1080-1085
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A controlled hydroponic experiment was undertaken to investigate Cd uptake in relation to the activity of Cd species in solution
other than the free ion (Cd2+) by maintaining a constant Cd2+ activity under variable SO4
2?? and Cl?? concentrations exposed to maize
(Zea mays var. Cameron) plants. The objectives of these experiments were: (1) to distinguish and quantify the di erent uptake rates
of free and inorganic-complexed Cd from nutrient solution, and (2) to model the uptake of Cd by maize with a Biotic Ligand Model
(BLM) in a system which facilitates the close examination of root characteristics. Results of the current experiments suggest that, in
addition to the free ion, CdSO4
0 complexes are important factors in determining Cd uptake in nutrient solution by maize plants. Higher
nominal SO4
2?? concentrations in solution generally resulted in a greater Cd accumulation by maize plants than predicted by the Cd2+
activity. A better integration of the complete dataset for the 3 harvest times (6, 9 and 11 days after treatment) was achieved by including
consideration of both the duration of Cd exposure and especially the root surface area to express Cd uptake. Similarly, the fit of the
BLM was also improved when taking into account exposure time and expressing uptake in terms of root morphological parameters.
