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    硅钙镁调理剂对镉铅砷复合污染稻田的钝化作用及培肥效应

    Heavy Metal Stabilization and Fertility Amelioration of Paddy Fields Multi-Contaminated by Cadmium, Lead, and Arsenic Using Silicon-Calcium-Magnesium Amendment

      摘要
    • 摘要:
      目的 砷（As）的形态及生物有效性的响应规律与镉（Cd）、铅（Pb）存在本质差异，因此Cd、Pb和As共存引起的土壤复合污染比单一污染更加难以治理。探讨硅钙镁调理剂（SCM）对南方酸性Cd-Pb-As复合污染稻田的钝化修复效果及提高土壤肥力的作用，为解决复合重金属污染农田可持续安全利用问题提供技术方案与理论依据。
      方法 首先通过小区试验筛选SCM最佳施用量，并基于此在Cd-Pb-As复合污染稻田开展连续两季（早、晚稻）的大田验证试验，监测水稻籽粒重金属（Cd、Pb、As）含量变化，并分析不同时期土壤重金属（Cd、Pb、As）总量与有效态含量、土壤pH、阳离子交换量（CEC）及养分含量的变化情况。
      结果 小区试验条件下，单季施用SCM 2 250 kg/hm2较为合适，该用量下土壤有效态Cd、Pb含量降幅分别达42.4%和15.8%，且对土壤有效态As含量未产生显著不良影响（P＞0.05)，水稻籽粒Cd（0.107 mg/kg）、Pb（0.090 mg/kg）、As（0.289 mg/kg）含量均符合GB 2762—2022标准相关限值要求。大田试验条件下，SCM连续两季均施（累计4 500 kg/hm2）显著提升土壤pH（由4.86提升至7.26），累计增幅达39.3%；土壤有效Cd含量降幅为33.3%~48.3%，有效Pb含量降幅为15.7%~17.6%，有效As含量最大降幅为13.7%；与同期空白对照相比，稻米Cd含量降幅为65.5%~75.2%，Pb含量降幅为58.0%~63.0%，As含量稳定在安全限值内。土壤肥力则呈现不同幅度的升高，有机质含量由25.7 g/kg提升到30.8 g/kg，CEC由8.33 cmol(+)/kg提升至10.9 cmol(+)/kg。
      结论 连续施用两季硅钙镁调理剂（SiO2≥12%；2 250 kg/hm2)，能够显著降低土壤Cd、Pb污染，降低水稻对As的吸收，提升土壤肥力，实现Cd-Pb-As复合污染农田稻米的安全生产和土壤肥力同步提升。

       

      Abstract:
      Objective Arsenic (As) exhibits markedly different behavior in terms of speciation and bioavailability compared to cadmium (Cd) and lead (Pb). Therefore, the remediation of soils co-contaminated with Cd, Pb, and As is of great difficulty and has received relatively little attention, despite its serious environmental risks. This study investigates the immobilization remediation efficiency and soil fertility improvement effects of silicon-calcium-magnesium amendment (SCM) on acidic paddy soil co-contaminated with Cd, Pb, and As in southern China, aiming to provide technical solutions and theoretical basis for sustainable and safe utilization of heavy metal-contaminated farmland.
      Method The optimal SCM application rate was first determined through plot experiments. Subsequently, based on these findings, a two-season consecutive field validation trial (early and late rice) was conducted in paddy fields co-contaminated with Cd, Pb, and As. Heavy metal concentrations (Cd, Pb, As) in rice grains were monitored, while total and bioavailable heavy metal (Cd, Pb, As) contents, soil pH, cation exchange capacity (CEC), and nutrient contents were determined at different growth stages.
      Result Under plot experiment conditions, an application rate of 2 250 kg SCM per hectare per season was identified as optimal. At this rate, the bioavailable Cd and Pb contents in soil were reduced by 42.4% and 15.8%, respectively, with no significant adverse effect on bioavailable As (P > 0.05). The concentrations of Cd (0.107 mg/kg), Pb (0.090 mg/kg), and As (0.289 mg/kg) in rice grains all complied with the relevant limits stipulated in the GB 2762-2022 standard. Under field conditions, the consecutive two-season application of SCM (cumulatively 4 500 kg/hm2) significantly elevated soil pH from 4.86 to 7.26, representing a 39.3% increase. The bioavailable soil Cd content decreased by 33.3% to 48.3%, bioavailable Pb by 15.7% to 17.6%, with a maximum reduction of 13.7% for bioavailable As. Compared to the concurrent blank control, Cd and Pb in rice grains were reduced by 65.5%-75.2% and 58.0%-63.0%, respectively, while As content remained within safe limits. Soil fertility also improved: organic matter content increased from 25.7 g/kg to 30.8 g/kg, and CEC increased from 8.33 cmol(+)/kg to 10.9 cmol(+)/kg.
      Conclusion The consecutive application of the silicon-calcium-magnesium amendment (SiO2 ≥ 12%; 2 250 kg/hm2 per season) over two seasons successfully reduced soil Cd and Pb contamination, decreased rice uptake of As, and enhanced soil fertility, thereby achieving the dual goals of safe rice production and synchronous improvement of soil fertility in Cd-Pb-As co-contaminated paddy fields.

       

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