This study has been conducted to ascertain the impact of zinc (Zn) on cadmium (Cd) fractions in two types of calcareous soils of the Fars Province in Iran at the waterlogged and field capacity conditions; also we investigated the adsorption of Cd in soils throughout different shaking times. We examined the effect of Zn on Cd fractions due to their similar characteristics. Treatments were three levels of Cd (0, 30 and 60 mg kg⁻¹ of soil as CdSO₄·8H₂O), three levels of Zn (0, 5 and 10 mg kg⁻¹ of soil as ZnSO₄·7 H₂O) three-level incubation times (2, 4 and 8 weeks), two types of soils (clay and sandy clay loam) and two moisture regimes (waterlogged and field capacity). The randomized completed block design (RCBD) was used for this experiment. After 2, 4 and 8 weeks of treatments, the sequential extraction technique was used to determine the Cd concentration in (WsEx), (Fe–MnOx), (Car), (OM) and (Res) fractions. In the waterlogged condition, adding Zn as zinc sulphate reduced the concentration of Cd in Fe–MnOx, Car and OM fractions but had no significant effect on the WsEx and Res fractions. Changes in the chemical fractions of Cd under the influence of zinc sulphate in both soils followed a similar trend. In the field capacity condition, adding Zn as zinc sulphate reduced the concentration of Cd in WsEx, Car and OM fractions and increased the concentration of Cd in the Fe–MnOx and Res fractions in the clay soil. In the sandy clay loam soil, adding Zn decreased the Cd concentration in Car and OM fractions and increased the Fe–MnOx fraction while has no significant effect on WsEx and Res fractions. It can be concluded that the changing in the Cd concentration in its chemical fractions caused by Zn addition might be from the competitive transport and adsorption interactions between these two ions. The presence of Zn reduces the concentration of Cd in those fractions that are easily released into the soil solution from where they can be absorbed by plants. The results showed that the best-fitted model which can describe the Cd adsorption was the power function model. It seems that clay and organic mineral are the dominant parts which control the Cd adsorption in soils. The rate of Cd adsorption in almost all shaking times was high which shows that Cd has more ability to occupy the adsorption sites.

进行这项研究是为了确定在淹水和田间条件下，伊朗法尔斯省的两种钙质土壤中锌（Zn）对镉（Cd）组分的影响。我们还研究了不同振荡时间下土壤中镉的吸附情况。由于它们的相似特性，我们研究了锌对Cd馏分的影响。处理包括三水平的镉（CdSO ₄ ·8H ₂ O为0、30和60 mg kg ^-1土壤），三水平的锌（ZnSO ₄ ·7 H ₂为0、5和10 mg kg ^-1土壤）O）三级孵化时间（2、4和8周），两种土壤（黏土和沙质壤土）和两种水分状况（涝渍和田间持水量）。随机完成的块设计（RCBD）用于该实验。在处理2、4和8周后，采用连续萃取技术确定（WsEx），（Fe-MnOx），（Car），（OM）和（Res）馏分中的Cd浓度。在淹水条件下，添加锌作为硫酸锌可降低Fe–MnOx，Car和OM馏分中Cd的浓度，但对WsEx和Res馏分无明显影响。在两种土壤中，硫酸锌的作用下镉化学成分的变化趋势相似。在田间条件下，添加锌作为硫酸锌可降低WsEx中Cd的浓度，Car和OM分数增加了粘土中Fe–MnOx和Res分数中Cd的浓度。在砂质壤土上，添加Zn会降低Car和OM组分中的Cd浓度，并增加Fe-MnOx组分，而对WsEx和Res组分没有显着影响。可以得出结论，由于添加锌引起的化学成分中Cd浓度的变化可能是由于这两种离子之间的竞争性迁移和吸附相互作用。锌的存在降低了那些容易释放到土壤溶液中的镉的浓度，这些镉可以被植物吸收。结果表明，能描述Cd吸附的最佳拟合模型是幂函数模型。似乎粘土和有机矿物是控制土壤中Cd吸附的主要部分。几乎所有振荡时间内Cd的吸附率都很高，这表明Cd具有更多的吸附位点。