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 0.008 9, 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. © 2020, Science Press. All right reserved.