Activators Enhanced Phytoremediation Of Cadmium Contaminated Soil

In recent years,with the expansion of urban integration and development of extensive industry,the problem of heavy metal pollution in soil such as cadmium(Cd)pollution was becoming more crucial.It caused severe damage to all the substituents of the ecosystem,including human beings.Therefore,it has been considered more vital to study the remediation measures of soil with heavy metal Cd,as well as it is also necessary to control the causes of pollution and strengthen the remediation measures of contaminated soil.In this research,the soil contaminated by Cd was the main research subject;the effects of five activators(wood vinegar,saponin,GLDA,HEDP,and citric acid)on the activation of Cd were studied by pot experiment and field experiment Sedum alfredii Hance(rock crop),Brassica napus L(oilseed rape),and Loliumperenne L(ryegrass),which laid the feasibility of joint remediation for contaminated farmland soil by cadmium.The main conclusions can be drawn as follows:As a result of the five different kinds of activators that were used to extract soil heavy metal cadmium,the leaching efficiency of all was increased for removing cadmium i.e.GLDA> CA > HEDP > Saponin > WV.As compared to other activators,the efficiency of GLDA was observed the higher in removing cadmium(69.08% for 50 mmol/L)while WV was the lower one.In the pot experiment,it was found that Saponin could induce heavy metals to encourage soil adsorption,and in this way,it enhanced the bioavailability of heavy metals.Soil for the experiment was chosen from one agricultural field and was having pH of the regional soil of 6.76,the content of organic substance was relatively low or 2.56%,amount of cadmium cons wasted in soil was 9.3mg/kg.So for Cdcontaminated soil except for GLDA,the growth inhibitory activity of Brassica napus L was inhibited among the five activators and the remaining activators increased the biomass.Between them,HEDP increased the dry weight of oilseed rape by 32%,which was the most significant.By testing,WV limits the growth of Sedum alfredii Hance plants,and CA increases its biomass and also it added Sedum alfredii Hance plant growth to 94.7%.The addition of HEDP and CA increased the absorption of cadmium by 2.38% and 5.50% in the subsurface part of oilseed rape.This may be because the two activators entered the soil to form soluble chelates with heavy metal Cd,promoted the desorption of Cd from the soil and enhanced the bioavailability of heavy metals,thus promoting the absorption of Cd by plant roots.Rapeseed plant,the cadmium is transformed into root>stem converting to a sequence.Five types of activators improved the absorption of cadmium to other forms of growth and residue state improved the absorption of plants.The effects of the cultivated species on the cultivation was 50 mmol/L of GLDA > 10 mmol/L WV > 10 mmol/L of HEDP > 50 mmol/L CA > 10 mmol/L Saponin.The extraction efficiency of cadmium by 75.35% of GLDA was higher than that of other activators.The combination of activator and plant mixing varied from soil to plant cadmium absorption.Testing was that the CA with Brassica napus L plant most effective and when HEDP with the rock crop plant are also best combination.Five activators(GLDA,HEDP,CA,Saponin,WV)were chosen to be phytoremediation with Loliumperenne L,Sedum alfredii Hance and Brassica napus L to study the effects of repairing the soil contaminated by Cd through field experiments.Compared with pure phytoremediation,GLDA and HEDP promoted the growth of Loliumperenne L when Cd pollution was higher.For all five activators,the WV inhibited the growth of plants,but the other four kinds of activators increased the biomass of the Sedum alfredii Hance.The five activators reduced the enrichment coefficient and the transport coefficient of Cd,while the influence on the root enrichment of Cd.In the farmland experiment,the local economic crop oilseed rape was chosen to remove the Cd from the soil enhanced by activators,the result showed all the five activators,promoted the rapeseed to uptake the Cd and the effect of five activators on the plant as Saponin(42.4%)> WV(34.5%)> GLDA(26.5%)> CA(18.5%)> HEDP(10.6%).Meantime,the activators also promoted the transfer of Cd from the underground part to the aboveground part,so that the Cd distribution in oilseed rape changed from root> stem> to stem> root.However,citric acid inhibited the biomass growth.As for Brassica napus L,five activators promoted plant biomass.In addition,the five activators selected in this experiment effectively promoted the Loliumperenne L stems and roots to uptake more Cd,but CA and GLDA have a low promotion on the Brassica napus L extraction of heavy metals.Same as Loliumperenne L,the five kinds of activators could promote the Cd extraction of stems and leaves of Brassica napus L under pollution,and HEDP has the most obvious promotion effect among them.