| In recent years,with the rapid development of the economy,heavy metal pollution in the soil has become increasingly serious.Cadmium(Cd)is a non-essential toxic metal.It is ranked at 7th position among 20 highly toxins due to its high solubility and toxic nature.Lead(Pb)is a highly toxic element and widespread environmental pollutant that can cause damage to the human body,especially to children’s growth and development.In this paper,we attempted to study the effects of agronomic regulation and control,intercropping and application of different deactivators on the accumulation and transport of Cd and Pb in wheat,and to reduce the absorption and accumulation of heavy metals in wheat during planting and application of passivating agents.The research results are as follows:In this study,pot experiments were conducted to investigate the effects of ryegrass(Lolium perenne L.),wheat(Triticum aestivum L.)monoculture and their intercropping on Cd、Pb accumulation and transport wheat in heavy metal contaminated soil in situ.The results showed that the Cd concentration in root,stem and leaf of wheat and total Cd amounts in whole wheat were significantly decreased under intercropping mode.The concentration of Cd in shoots decreased by 44%compared with the monoculture at the harvest stage.Compared with the monoculture,the intercropping between ryegrass and wheat reduced the translocation coefficient of wheat from root to all aerial parts during harvesting stage,and this also decreased the Cd concentration of the grain by 13.4%.The intercropping pattern of Pb concentration in wheat roots was significantly lower than that of monoculture,and the total Pb amounts in wheat above the whole growth period was significantly lower than that of monoculture.The Pb transport coefficient of the aboveground organs to grain was significantly lower than that of monoculture,which reduced the Pb concentration of the grain by 76%.On the other hand,the intercropping of wheat and ryegrass increased the absorption of Cd and Pb by ryegrass,and increased the accumulation of Cd and Pb in ryegrass roots and shoots.The above results showed that the agronomic method of ryegrass and wheat intercropping could significantly reduce the accumulation of heavy metals in wheat plants,increase the accumulation efficiency of ryegrass on Cd and Pb,and effectively reduce the concentration of Cd and Pb in wheat grains.In order to study the effects of agronomic control measures on heavy metal accumulation and transport in plants after intercropping with different plants and wheat,outdoor pot experiments of hyperaccumulating plants Solanum nigrum(Solarium nigrum L.),wheat monocropping and Solanum nigrum and wheat intercropping were conducted.The results showed that the intercropping of wheat and Solanum nigrum promoted the accumulation of Cd and Pb in various organs of wheat during the whole growth period,and the total Cd and Pb amounts from wheat shoots also increased significantly.At the same time,the intercropping pattern promoted the increase of Cd and Pb concentration in the shoots of Solanum nigrum,and the total Cd and Pb amounts from the shoots of Solanum nigrum increased significantly.During the whole growth period of wheat,the available concentration of heavy metals in soil gradually increased with the increase of time.The available concentration of Cd in wheat rhizosphere soil was higher in intercropping than in monoculture,while the available concentration of Pb in intercropping was lower than in monoculture.The available concentrations of Cd and Pb in the rhizosphere soil of Solanum nigrum intercropped were significantly higher than that of monoculture.There was no significant effect on the biomass of Solanum nigrum,but the dry weight of wheat intercropped during grain filling and harvest was significantly higher than that of monoculture.The results showed that the intercropping of wheat and Solanum nigrum increased the availability of heavy metals in soil and promoted the accumulation of heavy metals in plants.This indicates that the agronomic measures of wheat and Solanum nigrum intercropping could not reduce the accumulation of heavy metals in wheat.The pot experiment of wheat in greenhouse was carried out by applying passivator to heavy metal contaminated soil.The five treatment groups were set up:(1)Hydroxyapatite was added at the dosage of 20 g kg-1;(2)Lime was added at the dosage of 4 g kg-1;(3)Superphosphate was added at the dosage of 20 g kg-1;(4)Biochar was added at the dosage of 50 g kg-1;(5)the control(no blunt application).The effect of wheat on the accumulation and transport of heavy metals after applying a passivating agent.The results showed that the Cd concentration of wheat in the hydroxyapatite,lime and biochar treatment groups decreased by 76%,60%and 74%compared with the control at 40 days,and the total Cd amounts decreased by 77%.60%,78%;Pb concentration in wheat shoots was also significantly lower than the control group,which decreased by 80%,82%,and 76%,respectively.At 80 days,the Cd concentration and the total Cd amounts of wheat in the hydroxyapatite and biochar treated groups were significantly lower than those in the control group.However,the total Pb amounts from wheat shoots treated with four passivators was significantly lower than that of the control group,with a decrease of 74%,68%,43%and 45%,respectively,and the root to ground transport coefficient was also significantly lower than the control group.This indicated that the amount of accumulation of Cd and Pb in wheat plants could be significantly reduced after the application of the passivating agent. |
