The Cadmium Bioavailability Of Tobacco In Major Tobacco-growing Soil And Its Influencing Factors

Cadmium is a highly toxic biological heavy metals，cadmium in the soil was absorpoted throughplant root and transported in vivo，eventually accumulated in the edible parts of plants，finally thecadimum was in the body of people through the food chain，it is harmful to humans. Since2010，excessive heavy metals in cigarettes has been the focus of public attention. This study was based on theinvestigation of94soil samples which in nation’s major tobacco growing area and the correspondingtopsoil cadmium content in tobacco leaves，combined with soil properties，came to the factors thataffected tobacco cadmium bioavailability，on this basis，seven different soil types were selectd to designpot experiment，summarized the accumulation and uptake of cadmium of tobacco laws，and analysedthe differences between the different soil types，studied tobacco cadmium bioavailability under differentsoil types，the main findings are as follows:(1) Through determination of cadmium in the94major tobacco growing area topsoil and thecorresponding tobacco leaves：The nation’s major tobacco growing area average soil cadmium content0.192mg/kg，depending on soil quality standards (GB-15618-1995)，there are12samples exceededthe standard soil Cd whole，accounting for12.4%of the total sample；effective state of soil cadmiumcontent an average of0.101mg/kg，cadmium effective state average proportion of the total amount of53.76%；tobacco cadmium average1.44mg/kg，the highest value of8.14mg/kg.(2)The results of correlation analysis between the nation’s major tobacco soil physical andchemical properties and the cadmium content of cadmium content in tobacco leaves indicted: cadmiumcontent in tobacco leaves and soil pH，organic matter，soil particle volume fraction，and effective stateof soil cadmium levels were significantly associated with resistance，derived by further regressionanalysis：Log (Leaf-Cd)=0.70+0.58Log (Soil-Cd)+0.38Log (OC)-0.12pH (R2=0.48)(P <0.05)，soil cadmium content，organic matter and pH are the main factors.(3) Seven different soil types were selectd to design pot experiment，by measuring the differentperiods of cadmium in tobacco plant parts derived:：each treatment under different levels of cadmium，cadmium accumulation in tobacco volume is highest，followed by stems，roots minimum，and with thebirth period of tobacco plant changes，the cadmium content in tobacco plants and accumulation firstincreases，then decreases; cadmium content in different parts of tobacco，average cadmium distributionrate showed: lower leaves>middle leaves>upper leaves，where tobacco distribution rate of over78percent cadmium or more.In this study，the Cd enrichment factor of tobacco in different types of soil allabove1，indicating that tobacco is a kind of enriched cadmium ability crop.(4) From the analysis of differences in the bioavailability of cadmium in tobacco under sevendifferent soil types in the pot experiment showed： because different soil parent material，physicochemical properties and the use of different methods，cadmium bioavailability performance isnot consistent. Yunnan Red and Yellow，red brick Guizhou，tobacco leaves and cadmium accumulationof Guizhou paddy soil treatment under the cadmium content in different stages and levels of cadmium is higher than other treatments，and Shandong cinnamon，brown leaves at a low level. The same kind ofsoil types in different regions，tobacco cadmium bioavailability showed differences. This were occurredon the purple soil treatment，cinnamon and brown treatment in different areas. Because of differentvalue of the cadmium content in the different soil types，the cadmium bioavailability are not consistentafter exogenous added，in different growth stages，the cadmium accumulation volume in Shandongpoint d brown is more than10times to control，strongly influenced by exogenous cadmium，Yunnanyellow and red treatment showed little difference with the control.