| Rainwater gardens and rainwater seepage wells are typical low-impact development measures in the construction of sponge cities.At present,domestic and foreign researches on the two mainly focus on structural design and application effects.However,such facilities are not The impact process and pollution risk of soil and groundwater are not clear,which affects the reasonable application of such facilities.Therefore,in order to rationalize the deployment and scientific promotion of sponge facilities,it is necessary to carry out research on the impact of sponge facility rainwater infiltration on soil and groundwater.In this paper,the two rainwater gardens of Xi'an University of Technology and the seepage wells of Xianyang Vocational and Technical College were taken as the research objects.The rainfall data of the two research areas in 2018?2019 were collected,and the two sponges in 2018?2019 were obtained through on-site experimental monitoring.The inflow and outflow data of the facility,groundwater depth,and groundwater quality data analyze the effects of the two stormwater facilities on the regulation of stormwater runoff,and discuss the impact of the stormwater runoff on groundwater depth and groundwater quality.The main conclusions drawn are as follows:(1)The average removal rate of total phosphorus,total nitrogen,COD,ammonia nitrogen,and nitrate nitrogen in pollutants in rainwater runoff by the rain garden is 53.81%,30.57%,22.10%,78.89%,and-56.40%,respectively.The rainfall of each session has a correlation,in which the removal rate of total nitrogen and total phosphorus is non-linearly correlated with rainfall,and the relationship between the removal rate of COD and rainfall is linearly positively correlated.Compared with 2018,the removal effect of rainwater seepage wells on total nitrogen,COD,and ammonia nitrogen in stormwater runoff tended to be stable,with removal rates of 32.45%,16.09%,and 12.32%,respectively,but the removal of total phosphorus and nitrate nitrogen The rate is still unstable.(2)The inter-annual and intra-annual changes of the groundwater depth of the rainwater garden have a significant correlation with rainfall.Field rainfall is the main factor affecting groundwater depth variation.With the increase of rainfall,the variation of groundwater burial depth showed a trend of increasing first and then decreasing.When the rainfall is 25mm,the underground water depth changes the most.According to MODFLOW numerical simulation prediction,after years of different levels of richness,flatness,and dryness,the groundwater burial depth of rainwater gardens increased by 0.27?0.38m,0.16?0.27m,and-0.33?-0.14m,respectively.Through the analysis of the change trend of groundwater burial depth in the seepage well facilities from 2017 to 2019,it is concluded that the increase of groundwater burial depth before and after the construction of the seepage well is 0.48m;the supply of groundwater by the seepage well is significantly related to rainfall,but there is a Lag around month.(3)The concentrated infiltration of rainwater runoff will have a certain impact on COD,total nitrogen,heavy metal Cu and other indicators in the groundwater of the rainwater garden.The response of COD to rainfall has a one-day lag,and the impact on total nitrogen is greater in the flood season;application The comprehensive groundwater quality scoring method,improved Nemero index method and groundwater environmental capacity index evaluation method for groundwater quality in the rainwater garden area show that the groundwater quality of the rainwater garden in the flood season is more susceptible to the impact of rainfall runoff infiltration,at the inlet The impact is greater than the overflow.The change trend of groundwater quality in the seepage well area and the evaluation results of groundwater quality in 2018?2019 show that the groundwater quality closer to the seepage well is better than that farther away,so it can be considered that the construction of the research area with groundwater depth of 12?15m The seepage well will not negatively affect groundwater. |
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