This study aims to assess the effect of green waste compost (GWC), biochar (BC) and humic acid (HA) amendments of an alkaline heavy metal-contaminated soil. In this study, amendments with GWC, GWC + BC and GWC + HA were applied to the heavy metal-contaminated soil in four application rates (0, 1, 2 and 5%), and was aimed at substantially mitigating the bioavailability of heavy metals for pakchoi cabbage from the sewage irrigation soils. The addition of different ratios of amendments can increase the pH of the soil by 0.11–0.30 units and also increase the organic matter content by 3.1–35.1%. The concentration of available arsenic (As), cadmium (Cd), zinc (Zn) and copper (Cu) in the CaCl₂ extract was decreased effectively by all the amendments, except for the increase in the available concentration of As by compost–humic acid (T8) in the soil. Compared with the control, the CaCl₂ extractable Cd was decreased by 33–48% after the addition of different ratios of amendments in the soil. Moreover, by increasing the content of compost and compost–biochar in combinations, easily exchangeable fractions of As, Cd, Zn and Cu were decreased, while the oxidation fraction and residual fractions were increased. When the soil amendments were applied, fresh weight of the root and shoot increased by 29–63% and 39–85%, respectively. Cd concentration in the roots and shoots of the pakchoi cabbage decreased by 21–44% and 26–53%, respectively, after adding different ratios of amendments. All the amendments were effective in reducing the Cd, Zn and Cu uptake by the roots and shoots of the pakchoi cabbage, and simultaneously reduce the absorption of As in the roots of pakchoi cabbage. As soil amendments, GWC alone or GWC + BC/GWC + HA application can significantly reduce the heavy metal levels in pakchoi cabbage while increasing the biomass production and higher application rate is more effective than the lower application rate.

中文翻译：

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多元素污染土壤中改良剂对小白菜重金属生物有效性、转化和积累的影响

本研究旨在评估绿色废物堆肥（GWC）、生物炭（BC）和腐殖酸（HA）改良剂对碱性重金属污染土壤的效果。本研究将 GWC、GWC + BC 和 GWC + HA 四种施用量（0、1、2 和 5%）施用于重金属污染土壤，旨在大幅降低重金属的生物有效性。用于从污水灌溉土壤中提取的小白菜。添加不同比例的改良剂可使土壤pH值提高0.11-0.30个单位，有机质含量提高3.1-35.1%。_{CaCl 2}提取物中有效砷 (As)、镉 (Cd)、锌 (Zn) 和铜 (Cu) 的浓度均被所有改良剂有效降低，除了堆肥-腐殖酸增加了有效砷浓度之外。土壤中的酸（T8）。与对照相比，土壤中添加不同比例的改良剂后， CaCl _{2可提取的Cd降低了33%~48%。}此外，通过增加堆肥和堆肥-生物炭组合的含量，As、Cd、Zn和Cu的易交换部分减少，而氧化部分和残留部分增加。当施用土壤改良剂时，根和地上部的鲜重分别增加了 29-63% 和 39-85%。添加不同比例的改良剂后，小白菜根部和地上部的镉浓度分别降低了21%~44%和26%~53%。所有改良剂均能有效降低小白菜根部和地上部对Cd、Zn、Cu的吸收，同时降低小白菜根部对As的吸收。作为土壤改良剂，单独施用GWC或施用GWC+BC/GWC+HA可显着降低小白菜的重金属含量，同时提高生物量产量，且较高的施用量比较低的施用量更有效。