2010 年 53 巻 3 号 p. 80-95
The phytoavailability of cadmium (Cd), lead (Pb) and Zinc (Zn) in soils from Bangladesh was assessed. The uptake by Ipomea aquatica and Oryza sativa was measured and a range of extractants tested on soils and plant tissue samples. Extractants tested were distilled H_2O, 1M NH_4Cl, 0.01M CaCl_2, 0.005M diethylenetriamine pentaacetic acid (DTPA), 0.1M ethylenediamine tetraacetic acid (EDTA), 0.1M HCl and 1M HCl. The extractability of metals varied depending on the metal species, the crop and the extractant used. The best extractant was 1M HCl, which extracted the highest amount of heavy metals and correlated most strongly with plant uptake measures. The use of 1M HCl is therefore recommended for first-level screening of soil contaminated with heavy metals, followed by 0.1M HCl as the second best choice if only one extractant is to be used. Regardless of the soils and the extractants used, the relative extractability was higher for Pb compared with Cd and Zn. Sequential extraction showed that Cd was associated mostly with the 1M NH_4Cl extractable fraction, while Pb and Zn were associated with the 0.005M DTPA, 0.1M EDTA, 0.1M HCl and 1M HCl fractions in most cases. The fractions of metals extracted varied widely using the sequential extraction procedure compared to single extractions for all soil types.
