The Development Of Prediction Models For Typical Heavy Metals Transfer From Soil To Corn Grain And Cross-species Extrapolation

With the continuous development of industry and agriculture,industrial “three wastes”, irrational urban waste discharge, pesticide,fertilizer and unreasonable irrigation, and extensive use of sewage sludge.Heavy metals showed a sharp increase in the world’s agricultural soils,and the resulting decline in soil productivity, serious problems ofagricultural pollution and ecological destruction, has become one of themain factors hindering agricultural production sustainable and efficientforward. Cadmium (Cd), lead (Pb), chromium (Cr), mercury (Hg) arehighly toxic heavy metals for both plants and animals. The presences ofCd, Pb, Cr, Hg in agricultural soils are of great concern regarding itstransfer in the soil-plant system. This study investigated the transfer of Cd,Pb, Cr, Hg (exogenous salts) from a wide range of Chinese soils to corngrain (Zhengdan958). Through multiple stepwise regressions, predictionmodels were developed combining the Cd, Pb, Cr, Hg bioconcentrationfactor (BCF) of Zhengdan958and soil pH, organic matter (OM) content,and cation exchange capacity (CEC). In addition, select two or moretypical soils, to study the bioconcentration of Cd, Cr, Pb, Hg in grains ofdifferent corn speciesin corresponding soil conditions. Moreover, theseprediction models from Zhengdan958were applied to other non-modelcorn species through cross-species extrapolation approach. The results as follows:(1) The pH of the soil was the most important factor that controlled Cduptake and lower pH was more favorable for Cd bioaccumulation in corngrain. There was no significant difference between three predictionmodels in the different Cd sources. When the prediction models wereapplied to other non-model corn species, the ratio ranges between thepredicted BCF values and the measured BCF values were within aninterval of2folds and close to the solid line of1:1relationship. Moreover,these prediction models also reduce the measured BCF intra-speciesvariability for all non-model corn species.(2) The soil pH and OM were the major factors that controlled Pbtransfer from soil to corn grains. The lower pH and OM could improvethe bioaccumulation of Pb in corn grains. No significant differences werefound between two prediction models derived from the differentexogenous Pb contents. When the prediction models were applied toother non-model corn species, the ratio ranges between the predicted BCFvalues and the measured BCF values were within an interval of2-foldand close to the solid line of1:1relationship. Moreover, the predictionmodel i.e. Log[BCF]=-0.098pH-0.150log[OM]-1.894at the treatmentof high Pb can effectively reduce the measured BCF intra-speciesvariability for all non-model corn species.(3) The pH of the soil was the most important factor that controlled Cr uptake and lower pH was more favorable for Cr bioaccumulation in corngrain. When the prediction model from Zhengdan958Log[BCF]=-0.0623pH-1.948is applied to other non-model corn species,the ratio ranges between the predicted BCF values and the measured BCFvalues were within an interval of2folds and close to the solid line of1:1relationship. Moreover, the prediction model also reduce the measuredBCF intra-species variability for all non-model corn species.(4) The soil pH was the major factor that controlled Hg transfer fromsoil to corn grain. The lower pH could improve the bioaccumulation ofHg in corn grains. No significant differences were found between twoprediction models derived from the different exogenous Hg contents.When the prediction models were applied to other non-model cornspecies, the ratio ranges between the predicted BCF values and themeasured BCF values were within an interval of2-fold and close to thesolid line of1:1relationship. Moreover, the prediction model i.e.Log[BCF]=-0.113pH-0.745at the treatment of high Hg can effectivelyreduce the measured BCF intra-species variability for all non-model cornspecies.(5) With increasing pH, the same corn species corresponding soilheavy metals (Cd, Pb, Cr, Hg) critical concentration increases. Cornspecies is more sensitive to toxic heavy metals in acidic soil greater thanalkaline soil. For Cd, Nongda84is the most sensitive species, Liangyu2 is the most insensitive species; For Pb, Jingketian183is the mostsensitive species, Denghai3is the most insensitive species; For Cr,Zhongdan808is the most sensitive species, Changyu13is the mostinsensitive species; For Hg, Tunyu88for the most sensitive species,Chuandan15is the most insensitive species.These suggested that these prediction models derived from Zhengdan958were adaptable to be applied to other non-model corn species topredict heavy metals (Cd, Pb, Cr, Hg) BCF in corn grains and assess theecological risk of Cd, Pb, Cr, Hg in different agricultural soils.