Investigation of effects of cadmium, lead, nickel and vanadium contamination on the uptake and transport processes in cucumber plants by TXRF spectrometry

Uptake and transport processes of some essential nutrient elements (K, Ca, Fe, Mn and Zn) in cucumber plants grown in contamination-free or in contaminated (10(-5) M Cd, Ni, Pb or V) nutrient solutions containing iron in the chemical form of Fe(III)-citrate, Fe(III)-EDTA or Fe-chloride were studied by total reflection X-ray fluorescence spectrometry (TXRF). The root samples were dissolved using a microwave assisted acidic digestion procedure, while the xylem sap samples were directly analysed after addition of internal standard. It was established that the accumulation in the roots and the transport rate of the four heavy metals investigated increase in order of V < Ni << Cd < Pb and V << Pb < Cd < Ni, respectively. Due to the relatively low accumulation and transport of V in the plant it has the smallest influence on the uptake and transport of the essential elements. Cd hampers the water uptake and thereby the amount of all transported essential elements, and in addition results in higher accumulation of Ca, Fe and Zn in the roots. Pb contamination leads to a drastic reduction of Ca accumulated in the roots and mostly a slight increment in the transport of the essential nutrient elements investigated. Ni contamination hinders the transport of K and Zn, and leads to a higher accumulation of Mn in the roots. The chemical form of iron and hereby the presence of complex forming agents play an important role first of all for the uptake and transport processes of Fe and K. (C) 1999 Elsevier Science B.V. All rights reserved.