Remediation Of Heavy Metal Pollution In Landfill Soil With Plant And Passivator

In recent years,the problem of soil heavy metal pollution has become increasingly prominent,which not only seriously threatens the safety of ecological environment,but also directly endangers human health.In this study,the purple soil polluted by heavy metals around Yunxi landfill in Yanting County,Sichuan Province was sampled at the top,middle and bottom of the landfill.Solanum nigrum L.and Sedum plumbizincicola were selected as restoration plants for 120 days pot experiment.In the same period,straw biochar and sepiolite were mixed according to the mass ratio of 1:1,2:1 and 1:2.The biochar and compound passivator were added at the amount of 1%and 3%respectively for 45 days and 90 days passivation culture experiment,and the two best passivator combinations were selected.Secondly,the selected passivator was applied to the soil after phytoremediation for 45 days.By analyzing the total amount of heavy metals in soil before and after remediation,the content of DTPA available state,the leaching amount of TCLP toxicity and the proportion of various forms of BCR,the remediation technology of heavy metal pollution in rural landfill sites by passivator combined enrichment plants is explored.The main results are as follows:（1）Biochar and three kinds of compound passivators can reduce the content of available Cd and Zn in soil DTPA.By comparing the fixation rate,two passivator combinations of 3%biochar（3B）and biochar 2:1 sepiolite（3B₂S₁）were optimized.The Cd fixation rates of the two treatments were 21.18%-39.89%and 11.99%-37.27%respectively.For heavy metal Zn,the passivation effect of 1%biochar 1:1 composite sepiolite（1B₁S₁）is the best,and the fixation rate is 13.08%-28.15%.Followed by 3B and3B₂S₁ treatment,the fixation rates were 4.26%-33.81%and 2.48%-30.89%respectively.（2）Both Solanum nigrum L.and Sedum plumbizincicola can enrich soil heavy metals and reduce pollution levels.For heavy metal Cd,Solanum nigrum L.has the best enrichment effect,the enrichment coefficient is up to 0.26,the content of Cd in soil decreases by 0.1517-0.4408 mg/kg,and the residual state increases by 4%-9%.Compared with Solanum nigrum L.,Sedum plumbizincicola has stronger enrichment ability for Zn,and the enrichment coefficient is 4.51,which is 20 times that of Solanum nigrum under the same conditions.under the same conditions.Compared with the original soil,the content of Zn in the soil decreased by 22.87-37.60 mg/kg,the content of weak acid extracted state and oxidizable state of Zn in the soil decreased by 4%-9%and 10%-20%respectively,and the residual state increased by 7%-20%.（3）Adding passivator to the soil repaired by Solanum nigrum L.and Sedum plumbizincicola with mineral can effectively reduce the level of soil heavy metal pollution,have little impact on the soil environment,and the soil p H is basically unchanged.3B combined with Solanum nigrum L.treatment had the best effect on the remediation of Cd pollution.The fixation rate of passivator for residual Cd in soil after plant adsorption was up to 62.68%,which was 3.58%higher than that of 3B₂S₁ combined with Solanum nigrum L.treatment.For heavy metals Zn,3B and 3B₂S₁ combined with Sedum plumbizincicola treatment had better remediation effect,and the highest fixation rates of Zn were 68.00%and 63.48%respectively.（4）Passivator combined with enrichment plants can effectively reduce the risk of soil ecological pollution and improve the stability of soil heavy metals（I_R）.Compared with the original soil,under the treatment of 3B and 3B₂S₁ combined with Solanum nigrum L.,the I_R of Cd increased by 14.33%and 10.39%,which was 6.90%and 4.24%higher than that of passivator alone.Under the combined treatment of Zn,3B and 3B₂S₁with Sedum plumbizincicola,the I_R increased by 26.68%and 19.95%.In conclusion,passivator combined with plants can effectively repair the soil heavy metal pollution of simple landfill sites in southwest villages and towns,reduce the total amount and available content of soil heavy metals,and increase the stability of soil heavy metals..In view of the heavy metal pollution in the soil of simple landfills in southwest villages and towns,it is suggested to apply 3%biochar or biochar 2:1 sepiolite after planting Solanum nigrum L.to repair Cd pollution,and 3%biochar or biochar 2:1sepiolite combined with Sedum plumbizincicola to repair Zn pollution.