Phytoremediation Of Pb Contaminated Soil In Community Garden

As a key place for the public to participate in horticultural activities,the quality of soil environment and plant growth have an important impact on the public ecological security.With the rapid development of human economy and society,a large number of heavy metals are produced and discharged into the soil by human activities such as the application of chemical fertilizers and pesticides,household garbage and transportation,causing serious soil pollution,reducing the yield and quality of edible crops in community gardens,and endangering human health through the amplification of the food chain.In this study,the community garden in Lin ’an District of Hangzhou was taken as an example,and the heavy metal components and contents of the community garden were measured by the method of land accumulation index and potential ecological risk index.On this basis,the application status of plant landscape in the site was investigated and analyzed,and edible plants and hyperenriched plants with high application frequency and landscape benefits were selected as the test plants.Pot experiment was carried out to explore the physiological characteristics of plants and the absorption characteristics of heavy metal lead under the two planting modes of single cropping and intercropping,and to summarize the plant configuration mode with the best restoration effect,so as to optimize and improve the plant landscape of community gardens under different green space types,in order to provide reference for the improvement of the overall quality of community gardens and the planning and design practice.The results are as follows:(1)The average values of six heavy metals(Cu,Zn,Pb,Cr,Cd and Ni)in soil of the study area were all lower than the screening values of GB15618-2018.The average content of Pb was relatively high,which was 1.72 times of the soil background value in Zhejiang Province.The average p H value of soil in the study area was 6.37,showing weak acidity.From the perspective of potential ecological risk level,the overall ecological risk is mild.Source analysis showed that the heavy metal pollution in the soil in the study area was mainly from human activities such as transportation,horticulture and residential life.(2)A total of 87 species of plants were recorded in the Pb contaminated sample plots.The applied species of herbaceous plants were relatively rich,and the seidola plants grew well in the survey plots.The edible plants are mostly leafy vegetables,followed by fruits.According to the survey,there are problems such as soil pollution and ecological landscape benefit not maximized in community gardens.Based on the principles of plant ecological restoration and landscape aesthetics,the pot experiment was carried out by selecting Sedum alfredii,Capsicum annuum,Apium graveolens,and Raphanus sativus.(3)Pot experiment with single as the control group,the study found that the intercropping pattern had a significant impact on plant physiological indexes.Under the intercropping system,the biomass of Sedum alfredii,Apium graveolens and Capsicum annuum increased significantly,while that of Brassica chinensis and Raphanus sativus decreased.The chlorophyll content of intercropping Apium graveolens,Capsicum annuum and Raphanus sativus increased significantly,while the chlorophyll b content of Brassica chinensis leaf decreased by 92.78%.The concentration of MDA in the leaves of edible plants showed a consistent pattern,and the concentration of malondialdehyde in intercropping was lower than that in monoculture.Intercropping significantly increased the content of Pro in Sedum alfredii and Capsicum annuum,but significantly decreased the content of Apium graveolens,Capsicum annuum and Raphanus sativus.In the intercropping system,the CAT in leaves of Apium graveolens,Capsicum annuum and Raphanus sativus increased significantly by 33.92%,41.94% and 53.80%,respectively.(4)Compared with monoculture,it was found that intercropping system could change the absorption and accumulation of heavy metals in plants.In intercropping mode,heavy metals increased significantly in the upper part and root of Sedum alfredii.The accumulation of Pb in edible parts of Apium graveolens,Capsicum annuum and Raphanus sativus decreased by 24.37%,162.50% and 39.82%,respectively,and the transfer of Pb in Apium graveolens,Capsicum annuum was inhibited,and the transport coefficients decreased by 33.01% and 38.96%,respectively.In conclusion,the intercropping of sedum sedum can effectively reduce the absorption of Pb to Apium graveolens,Capsicum annuum and Raphanus sativus,and the Pb content in edible parts is lower than the safe range stipulated by GB2762-2022,reaching the safe edible standard,which is an ideal combination mode under the intercropping mode.(5)Based on the above research results,in the intercropping mode,Sedum alfredii,Apium graveolens,Capsicum annuum and Raphanus sativus were given priority to be used in the public participation in horticultural experience activities for plant planting,so as to achieve the purpose of restoration and production.At the same time,in order to promote community gardens to give full play to the maximum biodiversity,supplemented by strengthening the remediation of Pb contaminated soil purposes.Considering the soil environment polluted by Pb,plants were selected to be suitable for local growth,have strong tolerance or resistance to Pb pollutants,and have good landscape effect.According to the basic principles of plant allocation in community gardens under different types of green space,comprehensive consideration of space status,residents’ needs,community governance and other factors,this paper proposes an optimization model of ecological restoration plants in community gardens,so as to improve the quality of soil environment in green space and realize natural,safe and diverse landscape construction.Finally,the purpose of optimizing community garden landscape,improving soil heavy metal pollution and improving the quality of living environment is achieved.