长江三角洲典型地区土壤-水稻系统中Cd的分布及其迁移制约因素

摘要

In order to find the Cd pollution and impact factors on the migration in soil-rice system in Yangtze River Delta Region. 66 groups of soil, rice shoot and rice grain from typical area were sampled; contents of heavy metals and major elements, soil pH, soil total organic carbon of those samples were measured; Cd pollution in soil and rice grain were evaluated by the means of relevance analysis, and the distribution of Cd were shown; impacts of soil pH and organic carbon, and other metal elements on Cd accumulation in rice were discussed. The results showed that mass fraction of Cd for the soil samples in typical area of Yangtze River Delta Region were (81. 39-1 441. 00) × 109 with the average of 277. 40× 10 9, and those of the grain samples were (10. 44-692. 40) × 10-9 with the average of55.63×10-9; according to the secondary level of Soil Environmental Quality Standard(GB 15618 - 1995), 9.09% of the soil exceeded the standard level for Cd content, and most of the Cd-polluted samples were from Suzhou, Zhenjiang and Changzhou; according to Maximum Levels of Contaminants in Foods Standard (GB 2762 -2005), 4. 55% of rice grains exceeded the standard level for Cd content, and most of the Cd-polluted samples were from Suzhou and Wuxi; impact factors on Cd accumulation in rice were soil pH and contents of total organic carbon,CaO, MgO and P; contents of S and Se were closely related with that of Cd, and Cd cooperated with Zn in rice, but contents of S, Se, Zn in soil had no significant influence on Cd accumulation in rices increasing soil pH and content of total organic carbon could reduce Cd accumulation in rice, and increasing contents of CaO, MgO and P in soil could decrease Cd absorption in a certain extent.%为了弄清楚长江三角洲土壤-水稻系统中Cd污染和迁移制约因素,采集了典型地区的水稻土壤、秸秆、籽实等样品共66组,测试了这些样品中重金属元素和常量元素的含量、土壤pH值和总有机碳含量等参数指标,并对这些参数进行相关性分析,评估水稻土壤与籽实中的Cd污染,探讨Cd空间分布,讨论土壤中pH值和有机质以及其他金属元素对Cd在水稻中积累的制约作用.结果表明:长江三角洲典型地区水稻土壤和籽实都存在Cd含量超标现象,土壤样品中Cd质量分数为(81.39～1441.00)×10 9,平均值277.40×10-9,而水稻籽实样品中Cd质量分数为(10.44～692.40)×10-9,平均值55.63×10 9；根据土壤环境质量标准(GB 15618-1995)的二级标准,水稻土壤超标率为9.09％,超标样品主要分布在苏州、镇江和常州；根据食品中污染物的限量标准(GB 2762-2005),水稻籽实Cd含量超标率为4.55％,超标样品集中在苏州和无锡；影响水稻积累Cd的因素有土壤中总有机碳、CaO、MgO、P的含量和pH值；水稻中S和Se含量与Cd含量关系密切,Cd与Zn表现为协同作用,土壤中S、Se和Zn的含量对水稻积累Cd无明显影响；提高土壤中pH值以及增加土壤总有机碳含量,能适当降低水稻中Cd的积累,适当增加土壤中Ca、Mg和P的含量能在一定程度上降低水稻对Cd的吸收.