Laboratory Research On Accumulation And Release Of Typical Pollutants Under Intermittent Aquifer Recharge Using Urban Stormwater

In recent years,with the rapid development of economy and society,problems such as water shortage,water pollution,and deterioration of water ecology have become increasingly prominent.In order to alleviate the pressure of water supply and restore the water ecological environment,research and engineering practice on artificial recharge of groundwater have been widely carried out worldwide.In the context of the general shortage of high-quality freshwater resources on the surface,urban rain and floods have attracted increasing attention as an easily accessible unconventional recharge source.However,compared with conventional rivers and lakes,the formation of rain and flood is controlled by precipitation.The artificial recharge of groundwater using it as a water source is a typical intermittent recharge mode.The accumulation and release of pollutants in infiltration media during rain and flood is inevitable It is different from continuous recharge for a long time.This article retrieves and collects urban rainwater quality data of different countries and regions,and different underlying surfaces,selects typical urban rainwater pollutants(Fe,Zn,Pb)as research objects,and uses sand as an infiltration medium to design indoor groundwater Intermittent artificial recharge experiment,to study the media clogging and water quality change process during the infiltration process,reveal the accumulation and release of typical pollutants in the infiltration medium,and get the following main conclusions:1)During intermittent recharge,sand column blockage accelerates the accumulation of pollutants in the infiltration medium,but the accumulation of different pollutants in different media is different.Fe has accumulation in all layers of fine sand and medium sand medium;Zn has good migration ability only in medium sand medium,and it mainly accumulates in the surface layer in fine sand medium;the migration ability of lead is the weakest.The accumulation ability is the strongest,and it mainly accumulates in the shallow layer of the medium.2)After intermittent recharge,the pollutants accumulated in the medium can be partially released at the initial stage of recharging,which shows that the pollutant concentration at the outlet of sand column at the initial stage of recharging is significantly higher than that before intermittent recharge.With the continuation of recharging time,the concentration of pollutants decreased rapidly.With the increase of intermittent times,the peak release concentration of pollutants in the early stage of recharging decreases.The permeability of the plugging media was restored during the interval of recharging,which was the main reason for the concentrated release of pollutants during recharging3)Under intermittent recharge conditions,the indexes such as water content and redox potential of the sand column changed significantly,but under the experimental conditions(infiltration distance,intermittent time,and specific pollutants,etc.),the environmental indicators within the sand column did not change It has a significant impact on the migration and transformation of pollutants.The water chemistry type of the recharge water source did not change during the intermittent recharge process,and no new minerals were generated during the recharge process.4)Compared with continuous recharge,intermittent recharge generally increases the risk of groundwater pollution under the same conditions.The pollutant concentration control standard of the recharging water source should be determined according to the type of pollution substance,infiltration medium,infiltration distance,recharging time and recharging method.