[Speciation Characteristics and Bioavailability of Heavy Metals in Oasis Soil Under Pb, Zn Combined Stress]

Pot experiments were conducted on cole (Brassica) grown in oasis soil under combined stress of lead and zinc, to study the effect of heavy metal combined pollution on cole growth as well as the speciation conversion rules and bioavailability. The result showed that the promoting effect on cole growth was shown in the low concentration treatments, especially on stem leaves. With addition of exotic heavy metals, the main speciations of Pb and Zn in the soil transformed from tight-bound to loose-bound forms as compared to the control, and the bioavailability of heavy metals was increased. And, the exchangeable Pb and the carbonate bound form of Zn were the major contributing speciations which were absorbed in different parts of cole. What's more, the capabilities of uptake and translocation of Pb and Zn by cole were stronger at lower stress levels, and the enrichment and migration coefficients decreased with the increasing content of bioavailable fraction of the corresponding element or the coexisting element. In all treatments, the Pb concentration in the stem leaves of cole exceeded the food safety threshold, therefore it is recommended to conduct detection of relevant indicators before planting foliage vegetables in this kind of soil.