| The area of impermeable pavements and the risk of urban flood increased with the acceleration of urbanization.At the same time,the pollutants(total nitrogen(TN),total phosphorus(TP),chemical oxygen demand(COD)and heavy metals)carried by rainwater will eventually enter into rivers,causing water eutrophication and so on.Fillers are the most important factors to reduce runoff and purify water quality.In this paper,the soil properties of Xixian new area were as the research object,and based on the ratio of soil and sand(volume ratio is 4:4).In order to investigate the effects of permeability,impoundment and purification of the fillers,which seven kinds of materials(eg,biochar,compost,perlite,vermiculite,zeolite,straw,coir)and polyacrylamide(PAM)were combined under different proportions.Then selected the fillers of biochar and compost(the volume ratio is 1:1),biochar and zeolite(the volume ration is 0.5:1.5)to study the dynamic simulation,especially on the adsorption law of pollutants(COD,TN,TP,Cu,Zn,Cd)under different storm intensity(2a,5a)and different soil depth(10,20,30,40 cm).The main results are as follows:(1)Soil basic properties of Xixian new areaThe soil clay content of Xixian new area was high,and the soil bulk density,saturated water content and saturated hydraulic conductivity were 1.47-1.6 g/cm3,24.8%-34%and0.61-2.40 m/d,respectively.The soil total nitrogen,total phosphorus,organic carbon,available p content were 452-971 mg/kg,46-73 mg/kg,5.34-13.3 g/kg,3-37.4 mg/kg,respectively.(2)The fillers of permeability and static adsorption effect under different matrix composition amendmentsWithout PAM amendment,soil,sand and coir(volume ratio of 4:4:2)were the best in bulk density,saturated hydraulic conductivity and physical properties of saturated water content.With the addition of PAM,the bulk density was decreased,the saturated water conductivity and the saturated water content were increased under soil,sand,biochar and vermiculite(volume ratio of 4:4:1:1)and soil,sand,biochar and compost(volume ratio of4:4:1:1 and 4:4:0.5:1.5),respectively.The saturated water conductivity increased significantly with the increase of PAM mass concentration under the soil,sand,biochar and compost(volume ratio of 4:4:1:1)treatment.The bulk density,saturated water conductivity and saturated water content were the best under the soil,sand,biochar and compost(volume ratio of 4:4:1:1)as combined with 1%PAM treatment,which were 1.41 g/cm~3,7.93 m/d and34.57%,respectively.Compared with the control(soil and sand,the volume ratio of 5:5),the addition of different materials significantly improved the adsorption rate of TN.The best adsorption effect on TN was observed under biochar and zeolite(the volume ratio of 0.5:1.5)combined with1%PAM treatment,which was 72.4%.The ratio of biochar and zeolite(the volume ratio of0.5:1.5)had the highest adsorption rate of TP,which was 83.4%.Except for coir(the volume ratio of 2),biochar and zeolite(the volume ratio of 1:1 and 0.5:1.5),biochar and straw(the volume ratio of 1:1 and 0.5:1.5),the addition of other matrix significantly improved the adsorption rate of COD,the best adsorption effect on COD was observed in the biochar:compost(0.5:1.5)treatment,which was 57.6%.Secondly was the biochar and compost(the volume ratio of 1:1)treatment,the adsorption rate of TN and COD was 41.4%and 41.7%,respectively.As compared with the control,the addition of the PAM significantly enhanced the adsorption effect of Cu,the highest adsorption rate of Cu was 100%under the biochar and zeolite(the volume ratio of 0.5:1.5)with 1%PAM treatment.Except for biochar and zeolite(the volume ratio of 1:1 and 0.5:1.5)and biochar and straw(the volume ratio of 1:1,0.5:1.5)treatment,the other matrix composition amendment significantly improved the adsorption of Cd,the highest adsorption rate of Cd was 99.78%under the treatment of biochar and compost(the volume ratio of 1:1),however the highest adsorption rate of Zn was 99.97%under the treatment of biochar and vermiculite(the volume ratio of 1:1).(3)The dynamic adsorption effect of pollutant under different matrix composition amendmentsThe concentration of TN and COD were decreased with the time under the biochar and compost(the volume ratio of 1:1),biochar and zeolite(the volume ratio of 0.5:1.5)treatment under the storm intensity of 2a and 5a.As compared the concentration of TN and COD at the40 cm depth between the treatments,the concentration of TN and COD under biochar and zeolite(the volume ratio of 0.5:1.5)treatment was significantly lower than that of biochar and compost(the volume ratio of 1:1)treatment under storm intensity of 2a.However,the concentration of TN under biochar and zeolite(the volume ratio of 0.5:1.5)treatment was significantly higher than that of biochar and compost(the volume ratio of 1:1)treatment under storm intensity of 5a and there was no significant different in COD concentration between of the treatments.The concentration of TP was gradually increased with the time under biochar and zeolite(the volume ratio of 0.5:1.5)treatment under storm intensity of 2a,which the removal rate of TP was 38.17%～88%.However,the concentration of TP was not variance with the time under storm intensity of 5a,and the removal rate of TP was 29.2%～41.5%.There was a trend of gradual decrease of TP concentration under biochar and compost(the volume ratio of 1:1)treatment under storm intensity of 2a and 5a,respectively.As compared the concentration of TP at the soil depth of 40 cm between the treatments,results showed that the purification effect of TP under biochar and zeolite(the volume ratio of 0.5:1.5)treatment was better than that of biochar and compost(the volume ratio of 1:1)treatment under the storm intensity of 2a.However,there was no significant difference in the removal effect of TP between the treatments under the storm intensity of 5a.The removal rates of cadmium,copper and zinc was 98.78%～100%,98.83%～99.76%,99.96%～99.99%under biochar and compost(the volume ratio of 1:1),respectively.The concentration of Cu,Zn and Cd was zero under biochar and zeolite(the volume ratio of 0.5:1.5)treatment,and the removal rate reach to 100%.Considered the effects of infiltration,impoundment and purification,biochar and compost(the volume ratio of 1:1)combined with1%PAM was recommended the soil replacement media for urban green space in Xixian new area. |
PDF Full Text Request