Research On The Remediation Effect Of Organic Materials On Hexavalent Chromium In Soil And The Feasibility Of Soil Landscape Application After Remediation

Chromium（Cr）is a ubiquitous heavy metal element in soil.It is widely used in electroplating,textile,printing,leather tanning,wood preservation,paint pigment and metal processing and other industrial fields.Due to improper leakage,storage and disposal,chromium-containing waste will release a large amount of chromium into the environment under the action of long-term leaching and wind erosion,causing potential adverse effects on local ecological environment safety and human health.In soil,chromium mainly exists in trivalent and hexavalent forms.Cr（III）generally exists in soil in the form of oxides and hydroxides,with low bioavailability and toxicity.Cr（Ⅵ）exists in ionic state.It has strong mobility,toxicity and carcinogenicity.Solidification/stabilization and chemical reduction methods are commonly used methods for remediation of Cr（Ⅵ）-contaminated soils.Among them,organic remediation agents have received extensive attention due to their environmental friendliness.However,the access to such repair agents is usually limited,and the acquisition cost is high.Therefore,the efficient organic remediation agents which have low price and easy access to getting a lot is one of the problems to be solved in the remediation of Cr（Ⅵ）soil at this stage.Cr（Ⅵ）-contaminated soils are mostly landfilled after remediation,resulting in a waste of soil resources.Scientifically and safely restoring the function of soil growing plants,i.e.landscape application,may be one of the effective ways to solve the remediation and reuse of Cr（Ⅵ）contaminated soil.This paper studied the remediation effect of Ginkgo biloba and tangerine peel on Cr（Ⅵ）-contaminated soil and evaluated the feasibility of using Cr（Ⅵ）-contaminated soil after remediation of Ginkgo biloba leaves for Poa pratensis planting soil.The main conclusions are as follows:1)Ginkgo biloba leaves converts Cr（Ⅵ）into Cr（III）mainly through the reduction of its own decomposition product quercetin.At the same time,it can be used as a carbon source to drive the enrichment of Cr（Ⅵ）reducing bacteria in soil and further promote the reduction of Cr（Ⅵ）in soil.2)Tangerine peel mainly converts Cr（Ⅵ）to Cr（III）through the reduction of the hydrolysate of its macromolecular substances.At the same time,it can be used as a carbon source to drive the enrichment of Cr（Ⅵ）reducing bacteria in soil,but its reduction contribution is low.3)Compared with the uncontaminated soil,the stem and root growth of Poa pratensis in the Cr（Ⅵ）-contaminated soil after Ginkgo biloba leaves remediation was inhibited to a certain extent,but Poa pratensis could still grow well.There was a close relationship between the root exudates of Poa pratensis and the bacterial community structure in the medium chromium concentration soil(about 300-600 mg·kg^-1).The chromium stress in soil can be alleviated through amino acid co-metabolism.