Environmental Effects of Biomass Carbon Modified Bioretention Pond Fill Layer in Sponge City Gardens

With the expansion of urban green areas, the resulting increase in green waste has become the second-largest solid waste in the city. Green waste contains a lot of minerals and the recycling of its resources has become the urgent task of urban green development. Biochar technology is more in line with the concept of green environmental protection in Sponge City. In order to improve the utilization rate of green waste and rainwater resources, the study proposes to apply this technology to the waste disposal of urban gardens. Firstly, the soil quality of the city and the disposal methods of garden waste were investigated and analyzed. Then the waste was pyrolyzed and carbonized as material and the soil improvement indoor test and sponge soil outdoor test were carried out. At the same time, the pollutant interception and water retention function of biochar materials were tested. The results showed that the interception flow rates of the three experimental groups treated with biochar technology were 29.37, 33.14 and 31.98 L, respectively, which were significantly higher than those of the untreated group. The average total nitrogen removal rate of the three treatment groups was above 36% and the removal effect was significantly higher than that of the control group. Sponge soil has good infiltration coefficient and water retention performance and the water retention capacity can be increased by 30%. During rainfall, the water content of soil treated with sponge soil was 8.6~9.9% higher than that without sponge soil treatment. The concentration of suspended particulate matter in soil liquid under the treatment of sponge soil is significantly lower than that in the untreated original soil. This shows that the use of biochar technology can enhance the soil modification capacity in sponge cities and promote the resource recycling of urban waste