| Cadmium transfer factor in soil-plant system represents the comprehensive index of cadmium bioavailability and accumulation ability of plants. Transfer factor (TF) stands for the ability of plants transfer heavy metal, which is the ratio of heavy metal concentrations in plants to that in soil. It directly relates to bioavailability of heavy metals, affecting by physical, chemical and biological factors. This study aims to find the effect of physicochemical properties of soil no cadmium transfer factor, then develop a model, that is helpful for rish assessment and remediation of cadmium contaminated soils:This study involves two parts:One is about the effect of soil properties on cadmium bioavailability in soil-plant system. The plants used were spinach and tomatoes. Uncontaminated soils (15soiis) were collected with various properties over our country. Three concentration gradients (0、1、2mg/kg) of cadmium added to soils. After analyzing the contents of Cd in plants and soils, it was shown that main control factors on TF are pH, citrate/dithionate extractable A1(CD-A1); citrate/dithionate extractable Fe (CD-Fe), they can partly control the coefficients of variation in soil-plant system with44.6%-61.8%,42.2%-89.8% and42.2%-90.7%, respectively, while OMC, CEC and clay content(<2μm, Clay) are secondary factors.The optimal prediction equation of soil-spinach system cadmium transfor factor is:Control the optimal prediction equation of the soil-spinach system cadmium transfer factor is:TF1=2.679-0.248pH-0.020CEC+0.0629CD-Al (R2=0.811,P<0.001);Added exogenous cadmium contaminated soil-spinach system Cd transfer factor of the optimal prediction equation as follows:TF1=4.888-0.404pH-0.328OMC+0.0762CD-A1(R2=0.710,p<0.001);Added exogenous cadmium contaminated soil-spinach system added exogenous cadmium transfer factor of the optimal prediction equation as follows:TF2=5.433-0.446pH-0.376OMC+0.0517CD-Al(R2=0.701,p<0.001); The optimal prediction equation of soil-tomato system cadmium transfor factor is:Control the optimal prediction equation of the soil-tomato system cadmium transfer factor is:TF,=5.101-0.596pH-0.064CEC+4.341CD-Mn (R2=0.895,p<0.001)Added exogenous cadmium contaminated soil-tomato system Cd transfer factor of the optimal prediction equation as follows:TF1=0.183+0.532CD-Al-0.821OX-A1+3.700CD-Mn(R2=0.951,p<0.001;Added exogenous cadmium contaminated soil-tomato system added exogenous cadmium transfer factor of the optimal prediction equation as follows:TF2=2.459-0.301pH+12.097CD-Mn-10.613OX-Mn (R2=0.950,p<0.001)In the above content pH is represents the value of soil pH; CEC is represents cation exchange capacity; OMC is represents soil organic matter; CD-A1is represents citrate/dithionate extractable A1; CD-Mn is represents citrate/dithionate extractable Mn; OX-Mn is represents oxalate extractable Mn.The other is about how to reduce Cd phytoavailability in calcareous soils, the effects of soil amendments of red mud, rape straw, corn straw and red mud plus rape straw in combination with zinc fertilization on Cd extractability and phytoavailability to cowpea were investigated in a calcareous soil with added Cd at1.5mg/kg. The results showed that water soluble and exchangeable Cd in soils was significantly decreased by the amendments, which resulted in significant decrease by about27%(corn straw)-83%(red mud plus rape straw) in Cd concentration in cowpea. Combined with amendments, Zn fertilization further decreased the Cd concentration in cowpea. Compared with amendments only, the concentrations of Cd in the edible parts of cowpea treated with the Zn fertilization plus amendments decreased by27%on average. Also cruciferous rape straw was more effective than gramineous corn straw. In all treatments, rape straw plus red mud combined with Zn fertilization was most effective in decreasing Cd phytoavailability to cowpea in soils, and it is potential to be an efficient, cost-effective and environmentally friendly measure to ensure food safety for crop production in mildly Cd-contaminated and calcareous soils. |
PDF Full Text Request