| In recent years,the growth of the urban residential population and the improvement of people's living standard have led to the rapid increase of the output of the solid waste such as sewage sludge,and it is urgent to find a reasonable and effective way as an important way to eliminate and reuse the waste.The application of composting products in improvement of woodland soil is an economical and effective new idea of urban waste recycling.Taking the mixed composting products ofmunicipal sludge and garden waste as the research object.Three composting products such as the mixed compost of the common anaerobic digestion sludge and the garden waste(Abbreviated as "PH",the dry weight ratio of the sludge to the garden waste is 5:1),the mixed compost of high-grade anaerobic digestion sludge and the garden waste(Abbreviated as "GH",the dry weight ratio of the sludge to the garden waste is 3:1),and high-grade anaerobic digested pure sludge compost(Abbreviated as "GC")and five fertilizer gradients:0(CK),1.5 kg·m-2(T1),3 kg·m-2(T2),6 kg·m-2(T3),12 kg·m-2(T4)were setted.Through the plantation experiment,the growth of Cosmos bipinnatus and its absorption of heavy metal elements under the above five fertilizer gradients were studied;Through the continuous soil monitoring tests,the effects of three fertilizer products on pH,conductivity,total N,and heavy metal accumulation in soil under CK,T1,T2,T3 treatment with time were studied.In order to provide technical support and theoretical basis for the application of sludge compost products in woodland.The main conclusions are as follows:1.Though the experiment of the effect of fertilization on C.bipinnatus,the results showed that:(1)The plant height,biomass and the number of flower of C.bipinnatus were significantly increased with the application of mixed sludge compost.(2)The order of the contents of the heavy matal elements in the plant was:Cu>Zn>Cd,and the enrichment capacities to the three heavy metals were Cu>Cd>Zn;(3)Fertilization had little effect on the content of organic matter in the plant,but the content of N in the root increased with the increase of fertilizer application.2.Through the monitoring experiment on the effect of fertilization on forest land,the results showed that:(1)The soil pH decreased with the increase of fertilizer application,while the change trend of soil conductivity was opposite to the soil pH value;(2)The fertilization can increase N content in the soil.The content of N in soil was significantly higher in 9-12 months than in 3-6 months;(3)The order of the four heavy mental elements with higher content in soil was Mn>Cu>Zn>Cr,and the four elements did not exceed the environmental quality standard of soil pollution.The four elements increase with the amount of fertilizer applied,but with the change of time,the content of four elements have different trends;(4)The form of elements in soil was less affected by the type and amount of fertilization,and the four elements mainly existed in the form of residue.With the change of time,the elements of Zn and Mn showed the trend of changing from residual state to effective state.Contrary to the elements of Zn and Mn,the elements of Cu were changing towards more stable form.This study showed that the plantation ecosystem in Beijing plain afforestation area can tolerate a certain concentration of sludge and garden waste composting,and utilize the nutrients in it to improve soil fertility and promote plant growth. |
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