| In Soil-Tobacco system, the concentration factor (CF) of Cd is the indicators of the effectiveness ofcadmium in the soil and Cd accumulation capacity of tobacco from soil. The accumulation of tobaccoCd is not only related to the content of soil Cd but also impacted by the soil properties. This study aimsto find out the main factors for tobacco Cd absorption from soil and establish the prediction equationsbetween tobacco Cd and soil properties through the pot experiments. The filed experiment studies onthe effect of different immobilization materials and their combinations for the cutting of soil Cd. Allstudies will provide some reference for risk assessment and prediction of heavy metal pollution ontobacco, and offer some effective solutions for prevention and control of tobacco Cd pollution.The pot experiment indicates that the content and effectiveness of soil Cd is the most direct factors.When the soil pH <5.5, there is a significant linear correlation between tobacco Cd and soil Cd andwhen the soil pH>5.5, there is a significant linear correlation between logarithmic tobacco Cd andlogarithmic soil Cd. Soil pH is one of the most important factors that the Adj.r2of prediction equationraises from0.687to0.903when soil pH is added. Soil organic carbon (OC) is also the impact factor,which has a significantly negative correlation with tobacco Cd. The tobacco Cd can be predictedaccurately by the soil Cd, soil pH and soil OC. The prediction equation is:Log [Tobacco Cd]=3.041+1.212Log [Soil Cd]-0.270pH-0.264Log [OC](Adj.r2=0.911, p <0.001)There are different equations between different sources of soil Cd and tobacco Cd, the predictionequations are as follows:The equation between Soil Cdcontroland tobacco Cd is:Log [Tobacco Cd]=1.69+0.120Log [Soil Cdcontrol]-0.219pH-0.198Log [OC](Adj.r2=0.767. p <0.001)The equation between Soil Cdaddedand tobacco Cd is:Log [Tobacco Cd]=3.49+0.647Log [Soil Cdadded]-0.311pH-0.360Log [OC](Adj.r2=0.864, p <0.001)The equation between Soil Cdtotaland tobacco Cd is:Log [Tobacco Cd]=3.39+0.763Log [Soil Cdtotal]-0.306pH-0.372Log [OC](Adj.r2=0.846, p <0.001)The equation between Soil Cdaddedand tobacco Cd is better than others that indicate the Soil Cdaddedhas a better effectiveness and plant availability.Field study results show that every treatment could significantly reduce the concentration of Cd ineach part of tobacco compared with the control, among them, the treatment using red mud with rapestraw (RM+RS) is significantly better than other treatments. Adding immobilization materials cansignificantly affect the presence form of Cd in the soil compared with the control, with a decrease of theeffective Cd between18.6%and47.4%and an increase of the residual Cd. The contents of Cd in middleleaf and upper leaf correlate with soil available Cd significantly and the Correlation coefficient r2are0.962and0.991. The content of soil available Cd is the direct factor of tobacco Cd. Appling zincfertilizer to each treatment can further reduce the cadmium content of tobacco and each part withdecreasing amplitude between12.8%and30.0%, which indicates an obvious antagonism relationshipbetween cadmium and zinc. Applying the aluminum industry by-product red mud and cruciferous rape straw in company with zinc fertilizer can successfully reduce the effectiveness of soil Cd and theabsorption of tobacco from soil. Joint application of inorganic immobilization agent red mud,cruciferous rape straw zinc fertilizer is an effective and eco-friend method for soil Cd Immobilization. |
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