A Primary Study On Modeling Cadmium Accumulation In Rice And Wheat

Human being health is greatly affected by the quality of agricultural productthat is closely associated with heavy metals such as Cd in cropland soils. Thedependence of crop Cd content on soil Cd concentration has been well documented,while relatively few studies focus on the quantitative relationship between Cdcontent in cereal and soil Cd concentration. The objective of this study is to developa statistical model for quantifying the impact of soil available Cd on rice and wheatCd contents and to establish a semi-empirical dynamic model of Cd accumulation inrice plant. Data sets used in this study were extracted from about 50 articles and/ordegree theses.A partial correlation analysis to the data sets indicated that the concentration ofsoil exchangeable Cd is positively related to the soil total Cd concentration (Cd_T)and negatively correlated with soil pH. A further regression analysis suggested thatthe concentration of exchangeable Cd in soil could be quantitatively determined by alinear combination of Cd_T, soil pH and soil organic matter (SOM). Thus, thedependence of Cd content in rice and wheat (Cd_P, mg/kg) on total Cd concentrationin soils (Cd_T, mg/kg), soil pH and soil organic matter content (SOM, g/kg) can bedescribed by a statistical model Cd_P=a×EXP[b×log(Cd_T)+c×pH+d×SOM].Regression and residue analysis showed that this model fit the observed data setswell.Given that the accumulation rate of Cd (dCd/dt)in rice plant depends on thegrowth rate (dW/dt):dCd/dt=α×dW/dt, and the proportion coefficient (a)depends on available Cd in soil, the accumulation rate of Cd in rice plant ispositively related to the growth rate of rice plant and the proportion coefficient (a)can be described by total Cd concentration in soils including soil Cd(Cd_Y) andspiking Cd(Cd_T), and soil pH. Therefore, a dynamic model, of cadmiumaccumulation in rice plant is developed: dCd/dt=[-1.54+(24.82×Cd_Y+2.45×Cd_T)/pH]×dW/dt. Regression analysis and comparison of the observed data sets with calculateddata sets showed that this model fit the observed data sets well, and could be used to,estimate Cd accumulation in rice plant in different growth stages.