冬小麦吸收重金属特征及与影响因素的定量关系

冬小麦是我国主要粮食作物之一,保障农产品质量安全是农业生产的重要环节.冬小麦吸收重金属受多种因素的影响,为明确田间条件下冬小麦吸收重金属特征及小麦籽粒中重金属含量与土壤理化性质及土壤重金属含量的定量关系,在小麦收获时通过对我国华北小麦主产区50个不同重金属污染程度田块的土壤和小麦进行点对点采样,分析土壤重金属含量、土壤pH、土壤有机质(OM)、土壤阳离子交换量(CEC)、小麦籽粒和秸秆中重金属的含量,研究小麦吸收重金属特征及土壤理化性质对小麦吸收重金属的影响,并通过多元回归分析研究土壤重金属和理化性质与小麦籽粒重金属间的定量关系.结果表明,所采麦田土壤Cd含量范围为0.150～2.66 mg·kg~(-1),其对应的小麦籽粒Cd含量范围为0.033～0.39 mg·kg~(-1);土壤Pb含量范围为4.68～371 mg·kg~(-1),其对应的小麦籽粒Pb含量范围为0.27～2.4 mg·kg~(-1);土壤As含量范围为3.00～21.3 mg·kg~(-1),其对应的小麦籽粒As含量范围为0.044～0.18 mg·kg~(-1);小麦Cd、 Pb和As的超标率分别为55%、 100%和0,与之对应的土壤Cd、 Pb和As的超标率分别为52%、 13%和0.土壤Cd含量与小麦籽粒Cd含量呈极显著正相关(P0.01),相关系数r=0.663(n=50);土壤全Pb含量与小麦Pb含量呈显著正相关(P0.05),相关系数r=0.348(n=50);土壤As含量与小麦As含量相关性不显著;小麦籽粒对土壤Cd、 Pb和As的富集系数均值分别为0.17、 0.027和0.008 9,转移系数均值分别为0.52、 0.27和0.22;小麦对重金属的富集系数和转移系数均表现为CdPbAs.小麦秸秆中重金属含量高于对应籽粒中重金属含量2～5倍.土壤pH、有机质(OM)和阳离子交换量(CEC)也影响小麦籽粒Cd含量.将土壤Cd含量、土壤pH、有机质(OM)和阳离子交换量(CEC)与小麦籽粒Cd含量进行多元回归分析,得到4个小麦籽粒Cd含量预测方程,其相关系数r均达到极显著水平(P0.01),其中包括全部变量在内的预测方程的相关系数最高,r=0.810(n=50),可以较好地预测小麦籽粒Cd含量.

Characteristics of Heavy Metal Absorption by Winter Wheat and Its Quantitative Relationship with Influencing Factors

Winter wheat is one of the main food crops in China, and ensuring the quality and safety of agricultural products is an important component in agricultural production. The absorption of heavy metals by winter wheat is affected by many factors. To clarify the characteristics of heavy metal absorption by winter wheat under field conditions, and the quantitative relationship between the content of heavy metals in wheat grains and the physical and chemical properties of soil and its content of heavy metals, point-to-point sampling was carried out from 50 fields with different levels of heavy metal pollution in the main wheat-producing areas of North China. The pH, organic matter (OM), cation exchange capacity (CEC), and contents of heavy metals in soil, wheat grain, and straw were analyzed. In addition, the characteristics of heavy metals absorbed by wheat and the effects of the physical and chemical properties of soil on the absorption of heavy metals by wheat were studied, and the quantitative relationship between heavy metals and physical and chemical properties of soil and heavy metals in wheat grain was studied by multivariate regression analysis. The results showed that the Cd content in soil in the wheat field ranged from 0.150 to 2.66 mg·kg^-1, and the Cd content of the corresponding wheat grain ranged from 0.033 to 0.39 mg·kg^-1. The range of Pb content in soil was 4.68-371 mg·kg^-1, and the corresponding wheat Pb content range was 0.27-2.4 mg·kg^-1. The soil As content range was 3.00-21.3 mg·kg^-1, and the corresponding wheat grain As content range was 0.044-0.18 mg·kg^-1. The over-standard rates of wheat Cd, Pb, and As were 55%, 100%, and 0, respectively, and those of soil Cd, Pb, and As were 52%, 13%, and 0, respectively. Soil Cd content was positively correlated with wheat grain Cd content (P<0.01), with correlation coefficient r=0.663 (n=50). There was a significant positive correlation between soil Pb content and wheat Pb content (P<0.05), with correlation coefficient r=0.348 (n=50). There was no significant correlation between soil As content and wheat As content. The mean enrichment coefficients of wheat grains on Cd, Pb, and As were 0.17, 0.027, and 0.0089, respectively, and the mean transfer coefficients were 0.52, 0.27, and 0.22, respectively. The enrichment and transfer coefficients of heavy metals in wheat were Cd > Pb > As. The content of heavy metals in wheat straw was 2-5 times higher than that in corresponding grains. Soil pH, OM, and CEC also affect Cd content in wheat grains. Soil Cd content, soil pH, OM, CEC, and wheat grain Cd content were analyzed by multiple regression analysis, and four prediction equations of wheat grain Cd content were obtained. The correlation coefficient r reached a very significant level (P<0.01), and the correlation coefficient of the prediction equation including all variables was highest at r=0.810 (n=50), showing that it could predict the Cd content in wheat grains well.