蚕沙与海泡石联合施用对水稻根际土壤Cd生物有效性及籽粒Cd富集的影响

矿区重金属稻田土壤治理对水稻粮食安全意义重大,为探索蚕沙与海泡石联合施用对矿区重金属Cd污染稻田土壤的生态修复效果,明确其对水稻根际土壤Cd生物有效性和植株不同部位Cd富集及稻米安全性的影响,进行稻田原位土壤修复试验,早稻设置蚕沙+海泡石(T1)、蚕沙+腐植酸钠+海泡石(T2)、蚕沙(T3)3种钝化处理及不添加改良剂为对照(CK)处理,晚稻进行老化效果跟踪试验。采用梯度扩散薄膜(DGT)技术研究稻田根际土壤Cd生物有效性,探讨水稻植株不同部位Cd富集、籽粒Cd累积与其相关性。结果表明,蚕沙单独施用及与其他钝化材料联合施用均可降低Cd污染稻田根际土壤Cd生物有效性,与CK相比,早稻T1、T2、T3处理Cd生物有效性显著下降,分别下降88.36%、82.00%、74.18%;晚稻T3处理下降29.71%。蚕沙与海泡石联合施用减少水稻对Cd的吸收。水稻根系、茎秆、叶片、谷壳和籽粒Cd含量下降31.71%～55.54%、17.01%～84.60%、18.21%～57.09%、44.94%～49.69%和47.62%～53.84%。蚕沙与海泡石联合施用改变土壤理化性质,土壤pH提升0.13～0.27,电导率提高16.45%～121.54%,土壤有机质提高15.51%～39.64%。在老化效果跟踪试验中,蚕沙与海泡石施用处理下水稻籽粒的Cd含量达到安全水平,符合《食品安全国家标准食品中污染物限量》(GB 2762—2017)中的相关标准,对稻田Cd污染作用的持续影响效果最久。蚕沙与海泡石联合钝化有效阻控了土壤-水稻Cd之间的传递,可作为一种稻田Cd污染逆境生态调控的应用技术。

Effects of the combined application of silkworm excrement and sepiolite on Cd bioavailability in rhizosphere soil and Cd accumulation in grains of rice

Treatment of heavy metals in paddy field soil in mining areas is of great significance to rice food security. This study aimed to explore the ecological remediation effect of silkworm excrement combined with sepiolite on Cd-contaminated paddy soil in mining areas, and to clarify treatment effects on Cd bioavailability in rice rhizosphere soil, Cd enrichment in different parts of the plants, and rice safety. For in-situ soil remediation tests in the paddy field, early rice was treated with silkworm excrement + sepiolite(T1), silkworm excrement + sodium humate + sepiolite(T2), silkworm excrement(T3), and a control(CK) without any modifier, whereas late rice was subjected to the aging test to assess treatment effects. The gradient diffusion film(DGT) technique was used to study the bioavailability of Cd in rhizosphere soil of the paddy field, and the correlation between Cd accumulation in different parts of the rice plant and in the grains was evaluated. The results showed that the bioavailability of Cd in rhizosphere soil of Cd-polluted paddy fields was reduced by treatment with silkworm excrement and other materials. Compared with CK, the T1, T2, and T3 treatments decreased bioavailability significantly in early rice by 88.36%, 82.00%, and 74.18%, respectively, and by 29.71% in the T3 treatment of late rice. The combined application of silkworm excrement and sepiolite reduced Cd uptake by rice, and the Cd content in the roots, stalks, leaves, chaff, and grains of rice decreased by 31.71%~55.54%, 17.01%~84.60%, 18.21%~57.09%, 44.94%~49.69%, and 47.62%~53.84%, respectively. The combined application of silkworm excrement and sepiolite improved soil physical and chemical quality. Soil pH, electrical conductivity, and soil organic matter increased from 0.13 to 0.27, 16.45% to 121.54%, and 15.51% to 39.64%, respectively. The Cd content of rice grains reached the safety level in the experiment on the aging effect of sepiolite, and met the relevant standards of National Food Safety Standard Limits for Pollutants in Food(GB 2762-2017). The lasting effect on Cd-pollution in paddy field was the longest. The combined passivation of sepiolite and silkworm excrement can effectively prevent and control the transfer of Cd between soil and rice, and can be used as an applied technology for the ecological regulation of Cd pollution in paddy fields.