Study On Phytoremediation Of Urban Lead Contaminated Soil In Jilin City

With the acceleration of urbanization and industrialization,people have to face a series of environmental problems while sharing the benefits of the reform and development.Among them,soil heavy metal pollution is the most serious problem,which has posted a threat to human health and survival.All these problems are demanding prompt solutions.Among various urban soil heavy metal measures of remediation,ornamental plants phytoremediation appears preferable due to its low cost,operational convenience,as well as its sustainable characteristics.This study took the urban soil of Jilin City as the research object and evaluated the soil lead pollution in different functional parks in Jilin City through the single-factor pollution index method and the potential ecological risk index method.Through hydroponics and pot experiments(0 mg·kg^-1,100 mg·kg^-1,200 mg·kg^-1,500 mg·kg^-1,and 1000mg·kg^-1),the common ornamental plants varieties with strong lead enrichment ability in Jilin City were screened out,which provided a scientific basis for the phytoremediation of heavy metal lead-contaminated soil,and also to provide a reference for the greening work of the landscaping department of Jilin City.The results are as follows:（1）The average single-factor pollution index（Pi）of soil lead in Jilin City was1.30,and the pollution level was mild.Among them,the Pi value of industrial park green space was 2.35 and has reached the moderate level;the Pi value of road green space and residential green space were 1.52 and 1.10,respectively,which were in the mild level;the Pi value of park green space was 0.84 and was denoted as not polluted.The order of pollution level was:industrial park green space>road green space>residential green space>park green space.The average single potential ecological risk coefficient of soil lead pollution in Jilin City was 6.47,and the order of potential ecological risk coefficients of the four functional parks was:industrial park green space（11.73）>road green space（7.61）>residential green space（5.50）>park green space（4.20）,implying that there existed mild ecological risks.（2）The result of the hydroponic experiment indicated that he lead content in the shoots of all the tested ornamental plants varied from 11.35 mg·kg^-1 to 1274.13 mg·kg^-1,among which Malachite was the highest,reaching 1274.13 mg·kg^-1,followed by the Solanum nigrum that has reached 1158.73 mg·kg^-1,the lead content in the root system varied from 47.13 mg·kg^-1 to 15698.46 mg·kg^-1.Moreover,the tolerance index of the shoots varied from 0.22 to 1.04.Malachite was the highest,followed by Solanum nigrum,which has reached 0.95.The range of tolerance index of the root system was 0.18-0.94.The aboveground enrichment coefficients ranged from 0.67 to5.64,among which Malachite was the highest,and the root enrichment ranged from9.14 to 48.06.In conclusion,the tolerance and enrichment abilities of Malachite and Solanum nigrum are relatively strong.（3）The results of the pot experiment showed that the lead content in the stems of Solanum nigrum and Malachite varied from 2.95 mg·kg^-1 to 66.51 mg·kg^-1;the lead content in the leaves was in the range of 1.95 mg·kg^-1 to 32.25 mg·kg^-1;the lead content in the flowers（fruits）ranged from 0.79mg·kg^-1 to 11.42 mg·kg^-1;the lead content in the root system ranged from 38.16 mg·kg^-1 to 356.52 mg·kg^-1.The order of lead content in the four parts was roots>stems>leaves>fruits（flowers）.The variation of the partial tolerance index of Solanum nigrum and Malachite was 0.52 to1.08,and Malachite was slightly lower than that of Solanum.The range of tolerance index of root system was 0.44-0.94.Malachite was higher than that of Solanum nigrum when the lead concentration was 100mg·kg^-1 and 200mg·kg^-1.The enrichment coefficients of the upper parts of nightshade and peacock grass ranged from 0.07 to 0.15,and the enrichment coefficients of the root parts ranged from 0.32to 0.84.The transfer coefficient varied from 0.08 to 0.22,which did not meet the critical standard for lead hyperaccumulators,but nightshade and malachite grew well at different lead pollution concentrations(except when the lead pollution concentration was 1000 mg·kg^-1),with remediation potential for lead-contaminated soil.In conclusion,the urban soil lead pollution in Jilin Industrial Park has reached moderate pollution,and such issues should be taken seriously and solved in time.Solanum nigrum and Malachite have strong tolerance and enrichment ability in both hydroponic experiments and pot experiments.Therefore,Solanum nigrum and Malachite have broad application prospects in the phytoremediation of urban lead-contaminated soil in Jilin City.