组配改良剂联合锌肥对土壤-水稻系统镉迁移转运的影响

Combined Effects of Soil Amendment and Zinc Fertilizer on Accumulation and Transportation of Cadmium in Soil-Rice System

选取湖南省长沙市北山镇某中重度Cd污染稻田进行田间试验,通过连续种植早晚两季水稻,研究了组配改良剂LS(石灰石+海泡石),同时结合土施Zn肥和叶面喷施Zn肥对水稻Cd吸收的影响.结果表明:(1)施用LS(2250 kg·hm^(-2)和4500kg·hm^(-2))的各处理均能使早、晚稻土壤pH值增加0.28~1.26个单位,土壤CEC增加7.7%~33.4%,而土施Zn肥(90kg·hm^(-2))和叶面喷施Zn肥(0.2 g·L^(-1)和0.4 g·L^(-1))对土壤pH值无明显影响.(2)基施LS的各处理能使早、晚稻土壤中TCLP和CaCl_(2)提取态Cd含量分别降低11.5%~38.8%和24.0%~81.0%,土施Zn肥和叶面喷施Zn肥对土壤Cd两种提取态含量无明显影响.(3)单一处理均能显著降低糙米Cd含量,但降低效果均不如联合处理,组配改良剂LS联合Zn肥的处理(L1Z1F1、L1Z1F2、L2Z1F1和L2Z1F2)使早稻和晚稻糙米Cd含量分别降低64.9%~67.5%和56.1%~80.6%,其中L2Z1F1(4500kg·hm^(-2)的LS+90 kg·hm^(-2)的Zn肥+叶面喷施0.2 g·L^(-1)的Zn肥)处理效果最佳.(4)各处理下水稻各部位Cd/Zn比显著降低,糙米中Cd/Zn比值与Cd含量呈极显著正线性相关,说明各部位中Zn含量的增加是稻米Cd含量显著降低的关键原因之一.组配改良剂联合Zn肥修复技术能有效阻隔水稻对Cd的吸收和转运,降低水稻糙米Cd含量,是一种能有效实现中重度Cd污染稻田安全利用的技术模式.

A field experiment was conducted in moderately and severely Cd contaminated paddy fields in Beishan Town,Changsha City,Hunan Province. This study examined the effects of LS amendment( limestone + sepiolite),in combination with soil application and foliar spraying of Zn fertilizer,on Cd uptake in early and late rice plants. The results showed that:(1) the application of LS( 2 250 kg·hm^(-2) and 4 500 kg·hm^(-2)) significantly increased pH and CEC values in paddy soil during the early and late rice seasons,but the addition of Zn fertilizer( 90 kg/hm^(2)) to soil and through foliar spraying( 0. 2 g·L^(-1) and 0. 4 g·L^(-1)) had no significant effects on the pH or CEC of the soil.(2) LS application decreased concentrations of TCLP-Cd and CaCl_(2)-Cd in the soils,by 11. 5%-38. 8% and 24. 0%-81. 0%,respectively,while neither of the treatments involving the addition of Zn fertilizer to soil or through foliar spraying had any significant effects on the concentrations of TCLP-Cd and CaCl_(2)-Cd.(3)Single treatments involving only LS amendment,Zn fertilizer in soil,or foliar spraying of Zn fertilizer also reduced Cd concentrations in brown rice,but to a lesser degree than the combined treatments. The combined treatments( L1Z1F1,L1Z1F2,L2Z1F1,and L2Z1F2) reduced Cd concentrations in brown rice by 64. 9%-67. 5% and 56. 1%-80. 6%,for early and late rice,respectively,while L2Z1F1( 4 500 kg·hm^(-2) LS + 90 kg·hm^(-2) Zn fertilizer +foliar spraying 0. 2 g·L^(-1) Zn fertilizer) resulted in the largest reduction in Cd concentration in brown rice.(4) The Cd/Zn ratio in brown rice was significantly positively correlated with Cd concentrations,indicating that increased Zn concentration in different rice tissues was one of the key reasons for decreased Cd concentration in brown rice. Clearly,as a remediation technology,combining LS amendments with zinc fertilizer is an effective method for achieving the safe utilization of moderately and severely Cd contaminated paddy fields, by effectively inhibiting the uptake, accumulation, and transportation of Cd in rice plants and decreasing Cd concentrations in brown rice.