Preliminary Study On The Toxicity And Alleviating Methods And Mechanisms Of Aluminum To Sedum Plumbizincicola Grown On Strong Acidic Soil

Soil metal pollution in China has a long history and the overall situation is generally not optimistic,particularly concerning the current Cd pollution issue in acid agricultural soils,which seriously threatens the food safety and human health.Remediation of metal-contaminated soil is urgently required in China.Acid soil in China accounts for about 21%of the total land area,mainly in 14 provinces and most widely distributed in the south of China.Soil acidity is an important limiting factor affecting agricultutal production worldwide and an important subject in the field of agricultural disasters study.Aluminum toxicity caused by soil acidfication has attracted increasing attention.As an environmentally friendly,cost-effective remediation technique,phytoextraction has drawn the interest of both domestic and international researchers.It has become a hotspot in soil remediation research and applications.Sedum plumbizincicola.is a cadmium/zinc hyperaccumulating plant with the advantages such as large biomass,fast growth rate,strong hyperaccumulation ability,and wide adaptability,and has been applied to farmland soils with low and middle Cd and Zn pollution level.However,its practical application in large scale in acid farmland soils is inevitably limited by the factors such as soil acidity and Al toxicity.The negative effects of Al toxicity in acid soils on the growth and metal uptake of S.plumbizincicola has become an urgent problem needed to be solved.In terms of Al toxicity alleviation,pot experiments were carried out using different kinds of amendments and intercropping S.plumbizincicola with Al-tolerant plants.In the experiment of spiking different amendments,three types of materials for acid soil improvement(calcium magnesium phosphate fertilizer(CMP),magnesium carbonate(MgCO3),potassium dihydrogen phosphate(KH2PO4))and different adding rates of CMP were adopted.The results show that different amendments have different effects on soil properties and phytoextraction performance of S.plumbizincicola.The detailed summaries are as follows:(1)Magnesium carbonate can significantly increase soil pH and reduce the concentration of available Cd and Zn and exchangeable Al in soils,and has little effect on soil available P content.Potassium dihydrogen phosphate has almost no effect on soil pH,available Cd and Zn concentration,but significantly reduces the soil exchangeable Al conten and increases the content of available P.Calcium-magnesium-phosphorus fertilizers had no significant effect on soil pH,soil available Cd,Zn concentration,and exchangeable Al content,but with the increase of the amount,the exchangeable Al content in the soil showed a downward trend,and the content of available P in the soil increased significantly.(2)Magnesium carbonate can increase the biomass of S.plumbizincicola to some extent,but the effect is not significant,and improve the metal uptake of S.plumbizincicola as well.On the contrary,potassium dihydrogen phosphate significantly inhibits the growth and metal removals by S.plumbizincicola.This indicates that KH2PO4 is not suitable for the amelioration of Al toxicity to S.plumbizincicola in acid soils.(3)With the increasing adding rates of CMP in soils,the shoot biomass of S.plumbizincicola showed an upward trend.This indicates that CMP fertilizer played a certain role in promoting the growth of S.plumbizincicol.Nevertheless,the high level of(18.78 g/kg)CMP addition significantly inhibited the growth of S.plumbizincicola.Overall,CMP spiking of 9.39 g/kg has the best promotion effect on the growth and metal uptake of S.plumbizincicola.(4)Both intercropping density of buckwheat(Fogopyrum esculentum Moench.cv Jiangxi)and S.plumbizincicola increased soil pH and reduce the concentration of exchangeable Al.The effects of two density intercropping on the uptake of heavy metals in S.plumbizincicola were different,The intercropping density of buckwheat and S.plumbizincicola at 1:2 increased the uptake of Cd and Zn by S.plumbizincicola.Intercropping was not conducive to the growth of companion S.plumbizincicola,but promoted the growth of buckwheat and reduced the uptake of Cd and Zn by buckwheat,indicating that under intercropping conditions,it did not increase the risks of metal contamination in the buckwheat.