连续5年施用钝化剂对根际土壤镉活性及在水稻植株体内转运与累积的影响

Effects of Passivator Amendment on Rhizospheric Soil Cd Activity and Cd Bioconcentration and Translocation in Rice Plants for 5 Continuous Years

    摘要
  • 摘要:
    目的 本研究旨在了解连续5年施鸡粪发酵有机肥、生石灰和Si-Ca-Mg土壤调理剂后，对水稻根际土壤镉（Cd）活性、水稻各部位Cd累积量和转运系数产生的累积作用效果。
    方法 选取Cd污染风险管制的酸紫泥田为研究对象，应用大田配对试验，于2015年开始单施三种钝化剂，并于2019年晚稻黄熟期，采集土壤及植株样品，测定根际土壤和水稻各部位Cd含量，研究根际土壤Cd活性和水稻各部位Cd的累积及转运对连续5年钝化剂施用的响应。
    结果 连续施有机肥、石灰和土壤调理剂处理后，分别显著降低水稻糙米、茎叶和根系Cd含量60% ~ 75%、40% ~ 77%和17% ~ 48%（P < 0.05）；其中，连续施石灰、土壤调理剂处理后，糙米Cd平均含量降至国家食品中污染物限量值（0.2 mg kg−1）以下。此外，连续施有机肥、石灰和土壤调理剂后，分别显著降低了Cd由水稻根系向茎叶、茎叶向糙米的转运系数26% ~ 38%、29% ~ 58%和根际土壤DTPA提取态Cd（DTPA-Cd）含量13% ~ 33%，但也提高了根际土壤pH值0.2 ~ 0.9个单位，根际土壤活性有机碳和速效养分含量也呈上升趋势（P < 0.05）。糙米Cd含量主要与水稻植株Cd转运系数、土壤pH、DTPA-Cd、交换态钙和络合态铁含量相关。
    结论 土壤Cd污染风险管制的酸紫泥田，连续5年施生石灰、Si-Ca-Mg土壤调理剂后，可实现稻米达标生产。稻米Cd累积量下降与水稻根际土壤Cd活性降低、植株Cd富集转运能力降低有关。

     

    Abstract:
    Objective This study aimed to explore the cumulative influences of 5-year continuous chicken manure, quicklime, and Si-Ca-Mg mineral amendments on rhizospheric soil Cd mobility, Cd bioconcentration and translocation factor in rice tissues.
    Method The moderately Cd-contaminated acidic purple mud paddy was selected. Three passivators were applied separately and biannually in field-paired trials since 2015. Soil and plant samples were collected at late rice ripening stage in 2019, and the Cd concentration of rhizosphere soil and rice parts was determined. The responses of rhizosphere soil Cd activities and the Cd bioconcentration and translocation in different rice organs were analyzed with the application of passivator for 5 consecutive years.
    Result The Cd concentrations in brown rice (CdR), stem and leaf, and root were significantly reduced by 60%-75%, 40%-77%, and 17%-48%, respectively, after the continuous organic fertilizer, quicklime, and Si-Ca-Mg mineral amendments (P < 0.05). Particularly, the CdR was lowered down to < 0.2 mg kg−1 and met the food safety standard set by China after the continuous quicklime and Si-Ca-Mg mineral amendments. Continuous passivator amendments significantly reduced the translocation factors of Cd from root to stem and leaf as well as from stem and leaf to brown rice by 26%-38% and 29%-58%, respectively. Also, they reduced the concentration of DTPA-extractable Cd in rhizospheric soils by 13%-33%, whereas elevated the pH value in rhizospheric soils by 0.2-0.9 units. The labile organic C and available nutrient contents in rhizospheric soils exhibited an increasing trend (P < 0.05). The CdR was mainly related to the Cd translocation factor in rice tissues, soil pH, DTPA-extractable Cd, exchangeable Ca, and complexed Fe contents.
    Conclusion The CdR could meet the food safety standard after 5 years continuous quicklime and Si-Ca-Mg mineral amendments in moderately Cd-contaminated acidic purple mud paddy. The CdR-reduction was related to the reduction in rhizospheric soil Cd activity and the Cd bioconcentration and translocation capacity in rice tissues.

     

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