Assessment of Isotopically Exchangeable Zinc in Polluted and Nonpolluted Soils

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Abstract
In this study, an isotope exchange kinetics (IEK) approach was used to study soil Zn exchangeability in five polluted and six nonpolluted soils. Results were used in a compartmental analysis to quantify the amount of Zn isotopically exchangeable within 1 min, the amount of Zn exchangeable between 1 min and 15 d, and the amount of Zn that could not be exchanged within 15 d. Results derived from short‐term IEK experiments (100 min) allowed for a precise prediction of the increase of exchangeable Zn throughout 15 d in most of the soils studied. The compartmental analysis conducted on the 11 samples allowed clear separation of the polluted from the nonpolluted soils and showed that most of the soil Zn is either very slowly or not at all exchangeable. The proposed approach yielded simultaneously the intensity factor, the quantity factor, and a parameter related to soil properties governing Zn sorption onto soil [r(1)/R]. The amount of Zn exchangeable within 15 d was found to be very close to Zn extractable by 0.005 M diethylene triamine pentaacetic acid (DTPA) + 0.01 M CaCl2 + 0.1 M triethanolamine (TEA) (ZnDTPA) in all soils, suggesting that both methods were characterizing the same pool of soil Zn.