| Coal gangue is a main solid waste produced in the process of coal production.Because of its low utilization and large accumulation,it causes serious pollution to the environment.It is meaningful for realizing the resource utilization of coal gangue to develop the matrix configuration of coal gangue as the main material.In this study,coal gangue was mixed with three levels of soil,polyacrylamide,fly ash and com straw to form the experimental substrate.The L9(34)orthogonal tab was used to arrange the test,Trifolium repens L.and Festuca arundinacea were planted for greenhouse cultivation.Chemical properties and heavy metal content of mixed substrate,growth status and accumulation of heavy metals in plants were measured to study the effect of different improvement treatment on plant growth and heavy metals enrichment and migration.The following main conclusions were obtained:(1)Coal gangue could significantly increase the contents of total nitrogen,total phosphorus,available nitrogen,available phosphorus,available potassium and organic matter in the substrate.Polyacrylamide increased the content of available nitrogen in the substrate and reduced the occurrence and leaching of Cr.Com straw increased the contents of organic matter,total nitrogen,available phosphorus,and significantly improved the alkalinity of substrate and reduced the content of As in substrate and leaching solution.Appropriate amount of fly ash could increase the content of available nutrients and reduce the occurrence and leaching of As and Cd.Effect from large to small is the ratio of coal gangue and soil,fly ash,com straw,polyacrylamide.According to the results of improving the substrate fertility and removing heavy metals,the optimum matrix determined by comprehensive equilibrium evaluation was:weight ratio of soil/gangue 1000g:0g,adding PAM 120mg,fly ash 75g,corn straw 50g.(2)Soil could increase the emergence rate,plant height,fresh weight and dry weight of Trifolium repens L.and inhibit the accumulation and transfer of Cd and As.Polyacrylamide increased the plant height and fresh weight of Trifolium repens L.and significantly reduced the enrichment of Cd and Cr.Fly ash signifieantly affected the growth index of Triolium repens L.and inhibited the enrichment of Cd,Cr and As.Com straw promoted the growth of Trifolium repens L.but did not significantly affect the accumulation and migration of heavy metals.Effect from large to small is the ratio of coal gangue and soil,fly ash,polyacrylamide,com straw.The optimum substrate which could promote the growth of Trifolium repens L.and inhibit the accumulation of heavy metals is A3B3C2D3:weight ratio of soil/gangue 500g:500g,adding PAM 120mg,fly ash 75g,corn straw 50g.(3)With the addition of soil,the growth indexes of Festuca arundinacea increased first and then decreased,and the enrichment and transfer of As were obviously inhibited.Polyacrylamide increased plant height,fresh weight and dry weight of Festuca arundinacea,and reduced enrichment ability of Cd.Fly ash significantly increased plant height,fresh weight and dry weight,and inhibited Cd enrichment on ground and root.Com straw could promote the growth of Festuca arundinacea,and inhibit the accumulation and migration of Cd and As.Effect from large to small is fly ash,the ratio of coal gangue and soil,eom straw,polyacrylamide.The optimunm substrate which could promote the growth of Festuca arundinacea and inhibit the accumulation of heavy metals is A2B3C3D3:.weight ratio of soil/gangue 750g:250g,adding PAM 120mg,fly ash 150g,com straw 50g.(4)The heavy metal accumulation and migration ability of Cr,As and Cd in Trifolium repens L·and Festuca arundinacea were compared.The results showed that the enrichment ability of Trifolium repens L.to Cr was higher than that of Festuca arundinacea.The enrichment and transfer ability of As and Cd in Festuca arundinacea is stronger than that in Trifolium repens L.It provided some theoretical references for the study of phytoremediation of heavy metals. |
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