水分管理对复合污染稻田Pb、Cd和As迁移特性及稻米质量安全的影响

水稻种植管理过程中水分控制关系着稻米质量安全。本研究通过田间大区试验,研究了种植根部起垄(RR)、干湿交替(IF)、长期淹水(CF)和常规管理(CK)4种水分管理模式对土壤重金属Pb、Cd和As的迁移、转运特性及对水稻质量安全的影响。结果表明:RR模式可以显著降低土壤中Pb、Cd和As含量;CF模式可显著增加土壤中Pb、Cd和As的含量;IF和CK模式下土壤重金属含量变化不显著;水分管理RR、IF和CK模式对土壤As的活度影响不大,仅CF模式可以增强As的活度;重金属Cd较Pb和As易活化,CF和CK可以显著增强其的活性,RR和IF模式对Cd的活化影响较小;重金属Pb有效态活化与水分管理模式无关;RR、IF水分管理模式可显著降低水稻根部重金属Pb、Cd和As的含量;IF模式下根上茎的重金属含量均为最高,RR模式下根上茎As的含量显著低于其他水分管理模式;RR和IF水分管理模式可以显著降低糙米中重金属的含量,低于《食品安全国家标准食品中污染物限量标准》(GB 2762-2017)对Pb、Cd和As的限量值,保障了糙米质量安全。RR模式对土壤中重金属从根系到茎叶的转运能力较强,从根系到糙米的转运能力最弱。CF和CK模式从根系到茎叶、从茎叶到糙米、从根系到糙米的转运系数均较高,转运能力较强,尤其对重金属Cd的转运能力较强。因此,在水分条件可控的种植环境条件下,推荐使用根部起垄和干湿交替措施实现中、轻度重金属风险区稻米的安全种植。

Effects of water management on soil heavy metal transport and rice quality safety

Water management in rice planting controls the rice quality safety.An experiment,including water treatments as roots ridging(RR),intermittent flooding(IF),continuous flooding(CF)and conventional planting(CK),was conducted to study the effects of different water management models on the movement and transport of heavy metals Pb,Cd and As in soil,as well as their effects on rice quality safety.The results showed that RR and CF models significantly decreased the contents of heavy metals in soil;while IF and CK models did not change the contents of heavy metals.RR,IF and CK models had little effect on soil As activity,while CF model enhanced As content significantly.Heavy metal Cd was easier to be activated than Pb and As;CF and CK models significantly enhanced Cd activity,while RR and IF models had little effect on Cd activity.The Pb activity was not related to water management models.The RR and IF water models significantly reduced the contents of Pb,Cd and As in rice roots.The contents of heavy metals in rice roots and stems in IF model were with the highest value,while the content of As in RR model was significantly lower than that in other models.The RR and IF models significantly reduced the heavy metals content in brown rice,which was lower than the National Standard for Food Safety Limits of Contaminants in Food(GB 2762-2017),indicating that the quality of brown rice was safe.The RR model was with the superior ability to transport heavy metals in the soil from roots to stems and leaves,and the inferior ability to transport heavy metals from the roots to brown rice.CF and CK models were with higher transport coefficients from root to stem and leaf as well as from stem and leaf to brown rice,indicating a stronger transport ability from roots to brown rice,especially for Cd.The roots ridging and intermittent flooding are recommended to achieve safe planting of rice in moderate and mild heavy metal risk areas under controllable planting environment.