Status of Heavy Metal Contamination in Paddy Soil of Guangxi Province and Effect of Silicon Fertilization on Cd Content in Brown Rice

广西稻田镉污染状况及硅对稻米镉的消减作用（英文）

[Objective] To provide a scientific basis for the management of Cd contamination, the status of Cd contamination in paddy soil of Guangxi Province, as well as the effect of silicon fertilization on Cd content in brown rice, was investigated. [Method] A total of 157 topsoil（0-20 cm） samples were collected from the major rice-growing paddy fields in Guangxi Province. The Cd contents in the topsoil samples were determined. The paddy soil environment quality and potential ecological risk were evaluated by single factor index and potential ecological index methods. In addition, in the Cd-contaminated paddy fields, the effects of different silicon fertilization treatments（no application（CK）, soil application of 750 kg/hm^2 silicon fertilizer（S）, leaf application of 1 500 L/hm^2 0.2% nanometer silicon（L）, soil application of 750 kg/hm^2 silicon fertilizer ＋ leaf application of 1 500 L/hm^2 0.2% nanometer silicon（SL）） on Cd content in brown rice were investigated. [Result] The total Cd contents in the 157 topsoil samples from paddy fields of Guangxi Province ranged from 0.02 to 7.33 mg/kg with an average content of 0.53 mg/kg. The Cd contents in 35.03% of the topsoil samples exceeded the grade II of national soil environment quality standards, and the topsoil samples were dominated by moderate and mild Cd contamination. Different silicon fertilization treatment all significantly reduced the Cd content in brown rice（P〈0.05）. In the treatment III, the Cd content in brown rice was lowest. Compared with that in the CK group, the Cd content in brown rice in the treatment III was reduced by 73.45%, in the treatment II was reduced by 62.07%, and in the treatment I was reduced by 34.48%. [Conclusion] The Cd in paddy fields of Guangxi Province showed a moderate to high ecological risk,and rational application of silicon fertilizer could effectively reduce the Cd content in brown rice.

[目的]调查广西稻田土壤镉污染现状,开展硅对稻米镉的消减作用研究,为治理广西稻田土壤镉污染提供科学依据。[方法]在广西境内,采集水稻主产区的稻田耕层(0~20 cm)土样157个,分析其镉含量,并采用单因子指数法和Hakanson的潜在生态风险指数法对稻田土壤环境质量和潜在生态风险进行评价;另外,在镉超标稻田上进行不同硅肥处理对稻米镉的消减试验,试验设不施硅肥作对照、土壤中施用硅肥750 kg/hm^2、叶面喷施0.2%纳米硅1 500 L/hm^2和土壤中施用硅肥750 kg/hm^2+叶面喷施纳米硅1 500 L/hm^24个处理,测定各处理的稻米中的镉含量。[结果]采样调查结果表明,广西稻田耕层土壤中全量镉含量为0.02~7.33 mg/kg,平均0.53 mg/kg,其中35.03%土壤样品的镉含量超过国家土壤环境质量标准的Ⅱ级标准,以中、轻度污染为主。硅肥试验结果表明,不同硅肥处理均显著降低了稻米中镉的含量(P<0.05),其中土施硅肥750 kg/hm^2+叶面喷施纳米硅1 500 L/hm^2处理效果最好,稻米镉含量比对照处理下降73.45%;喷施纳米硅1 500L/hm^2处理稻米镉含量下降62.07%,土施硅肥750 kg/hm^2处理下降34.48%。[结论]广西稻田土壤中镉的生态风险为中等至高的风险,合理施用硅肥可有效降低稻米镉的含量。