| With the rapid development of China’s industry,the discharge of waste water,waste gas,waste residues,etc.brought about by industrial production,as well as mining,metallurgy and agricultural production activities have caused the soil heavy metal content rise significantly.Heavy metals in the soil will accumulate in the human body through the food chain,causing serious damage to the ecological environment and human health.This paper attempts to study the absorption,accumulation and transfer of cadmium（Cd）and lead（Pb）of crops through the application of different soil amendments and rotation cropping modes,aiming to achieve safe production of crops and at the same time effectively control the farmland polluted by heavy metals in the soil.The results of this study are as follows:1.This article firstly investigated the effects of applying different amendments on the absorption,accumulation,and transport of Cd and Pb in the Cd hyperaccumulation plant Solanum nigrum L.,and the combined effects of the two on the content and distribution of Cd and Pb in soil to explore the feasibility of remediation of heavy metal contaminated soil by applying a passivating agent and planting nightshade when the farmland is idle.After the amendment is applied in the soil,an outdoor pot experiment is conducted.The experiment set up 4 treatments:（1）lime treatment:application amount is 10 g kg-1;（2）hydroxyapatite treatment:application amount is 20 g kg-1;（3）rice husk biochar treatment:application amount 50 g kg-1;（4）Control,no amendment is added.The results of the study showed that the application of rice husk biochar increased the growth of nightshade compared with the control group without the passivation agent.The other two amendments did not significantly promote the growth;these three amendments can reduce the Solanum nigrum L.in varying degrees.Three kinds of amendments can reduce the Cd content of roots and the Pb content of roots and shoots of Solanum nigrum L.in different degrees;lime and hydroxyapatite can reduce the total amount of Cd and Pb in plants.while the total amount of rice husk biochar did not show a significant reduction effect;with the extension of the treatment time,all three amendments reduced the content of DTPA-Cd and DTPA-Pb in the rhizosphere soil to varying degrees,but the effective state content of Cd and Pb treated by these three amendments were not significantly different;these three amendments increased the pH value of rhizosphere soil to varying degrees,and the effect of lime on the pH of rhizosphere soil was the most obvious.2.Through the outdoor pot experiment of heavy metal in situ contaminated soil,the effects of different amendments on the absorption,accumulation and transport of Cd and Pb in Vicia sativa L.The pot experiment also set 4 treatments:（1）lime treatment:application amount is 10 g kg-1;（2）hydroxyapatite treatment:application amount is 20 g kg-1;（3）rice hull biochar treatment:application amount is 50 g kg-1;（4）Control,no passivating agent is added.The test results of the experiment showed that the application of rice husk biochar increased the dry weight of the shoots and roots of Vicia sativa L.compared to the control,and the other two amendments did not promote growth;with the treatment time increased,the three amendments can reduce the Cd and Pb contents in the shoots and roots of Vicia sativa L.in different degrees.Among them,the hydroxyapatite decreased the Cd content the most,and lime decreased the Pb content more obviously.Among the three amendments,the application of ime and hydroxyapatite reduced the total amount of Cd and Pb in Vicia sativa L.,and the rice husk biochar also significantly reduced the total amount of Cd in Vicia sativa L.roots.In the growth of Vicia sativa L.,all three amendments can significantly increase the pH of rhizosphere soil,and the effect of lime on the pH of rhizosphere soil is more obvious than that of hydroxyapatite and rice husk biochar.Similarly,with the extension of the treatment time,all the three amendments reduced the content of DTPA-Cd and DTPA-Pb in the rhizosphere soil of Vicia sativa L.to varying degrees.The effect of lime and rice husk biochar on the effective content of Cd in the rhizosphere soil is better than applying hydroxyapatite;the effect of lime on the effective Pb content of rhizosphere soil is better than that of hydroxyapatite and rice husk biochar.The application of lime and hydroxyapatite also increased the soil nitrogen content.Because the Cd and Pb contents of the Vicia sativa L.shoots treated by the three amendments in various periods meet the national standard（GB13078-2017）,the Cd content is less than 1 mg kg-1 and the Pb content is less than 30 mg kg-1.Therefore,these three amendments are suitable for the safe production of Vicia sativa L.as forage feed.3.Based on the previous research,through field trials,the effects of amendments on the absorption,accumulation and transport of Cd and Pb in winter wheat（Triticum aestivum L.）and Vicia sativa L.rotation were studied.The field test also set up four treatments:（1）lime treatment:application amount is 2.23 t ha-1;（2）hydroxyapatite treatment:application amount is 4.46 t ha-1;（3）rice husk biochar treatment:The application amount is 11.15 t ha-1;（4）Control,no amendment is added.The results show that only rice husk biochar can promote the growth of the first-season crop wheat,and all three amendments have the potential to reduce the Cd and Pb contents in different parts of wheat,but they have not reached a significant level compared with the control.Lime significantly reduced the total Cd and Pb amount in wheat roots and the total Cd amount in grains.The other two amendmentss also showed a reduced effect on the total Cd and Pb amounts in different parts of wheat,but they did not reached a significant level compared with the control.Compared with the control,the application of rice husk biochar increased the growth of roots and aerial parts of the second season crop of Vicia sativa L.,lime and hydroxyapatite did not promote growth.The three amendments all reduced Cd and Pb contents in the shoots and roots of Vicia sativa L.in different degrees,among which hydroxyapatite and rice husk biochar significantly reduced the total amount of Cd in the shoots of Vicia sativa L.;three amendments can also reduce the total amount of Cd and Pb extracted from the ground and root system of Vicia sativa L.in different degrees.The reduction effect of lime and hydroxyapatite is the best.The three amendments not only increased the pH value of the rhizosphere soil of Vicia sativa L.,but also reduced the content of DTPA-Cd and DTPA-Pb in the rhizosphere;the effect of applying lime was the best. |
PDF Full Text Request