Assessment of the phytoavailability of Cu and Ni using various extraction procedures

Abstract

The phytoavailability of copper (Cu) and nickel (Ni) in soils from
Bangladesh was assessed. The uptake by Ipomoea aquatica and Oryza sativa L. was
measured and a range of extractants tested on soils and plant tissue samples.
Extractants tested were distilled water, 1 M NH4Cl, 0.01 M CaCl2, 0.005 M
diethylenetriamine penta‐acetic acid (DTPA), 0.1 M ethylenediamine tetraacetic
acid (EDTA), 0.1 M HCl and 1 M HCl. The extractability of the metals varied
depending on the metal species, the crop and the extractant used. The best
extractant was 1 M HCl, which extracted the highest amount of the heavy metals
and correlated most strongly with their plant uptake measures. The use of 1 M
HCl is, therefore, recommended for first‐level screening of soils contaminated
with heavy metals if only one extractant is to be used. Sequential extraction
showed that Cu was associated mostly with the 0.005 M DTPA and 0.1 M EDTA
extractable fractions, while Ni was associated with the 0.1 M HCl and 1 M HCl
fractions in most cases. The fractions of metals extracted using the sequential
extraction procedure varied compared to single extractions for all soil types.