| The present study focuses on investigating the occurrence,migration,and transport characteristics of typical antibiotics-sulfamethoxazole(SMX)and heavy metals-Cu(II)in urban surface particles as carriers.Specifically,we examined the infiltration behavior of SMX and Cu(II)in typical permeable pavement systems(permeable bricks,permeable concrete,and permeable asphalt)in runoff,and analyzed the main influencing factors and mechanisms involved.The findings of this study provide a theoretical basis and scientific support for source control of composite pollutants in runoff,ensuring the safety of urban water environments,and have significant theoretical and practical implications.The main conclusions are as follows:(1)The present study investigated the adsorption behavior of particulate matter collected from different regions in Beijing towards the typical composite pollutants sulfamethoxazole(SMX)and Cu(II).The results indicated that the surface of particulate matter possessed abundant pore structures and components including quartz,feldspar,and clay minerals,and could generate numerous hydroxyl groups and characteristic functional groups in aqueous environments.The particulate matter exhibited accumulation effects on SMX and Cu(II)composite pollutants and may rapidly combine with them at the initial stage of runoff.The interaction between SMX and Cu(II)could increase the accumulation amount by forming complex compounds,which significantly affected their presence characteristics on the particulate matter surface.The adsorption of composite pollutants by particulate matter was influenced by p H,and the synergistic effects between composite pollutants changed into antagonistic effects with the decrease of p H.When the p H was 4,the accumulation amount of SMX and Cu(II)in the composite system increased by 0.04 mg/kg and 0.33 mg/g,respectively.However,when the p H was 3,the accumulation amount of SMX and Cu(II)decreased by 0.21 mg/kg and 0.36 mg/g,respectively.The mechanism of particulate matter accumulation of composite pollutants may involve EDA interaction,hydrogen bond interaction,Lewis acid-base interaction,and other factors.(2)This study investigated the impact of runoff scouring on point source pollution of SMX on urban impervious surfaces and explored the transport characteristics under different rainfall intensities.The results showed that the peak value of dissolved SMX was reached in the first 5 minutes before scouring,and then showed a fluctuating state.The peak value of particulate SMX was reached at 20 minutes and gradually decreased.The scouring rate of particles increased rapidly in the early stages of rainfall,and within 20 minutes,81% of the total scouring amount of particles was washed away,with smaller particle sizes being more easily washed away.Smaller particles were more likely to combine with SMX to form particulate SMX,so the particulate SMX increased rapidly in the early stages of rainfall.Cu(II)-loaded particles significantly reduced the proportion of dissolved SMX in the effluent.Cu(II)can form a particulate-Cu(II)-SMX ternary complex,promoting more SMX to transform into particulate form.An increase in runoff volume reduces the amount of pollutants carried by unit runoff,and an increase in rainfall intensity weakens the proportion of pollutants carried by the same proportion of runoff.(3)The infiltration characteristics of SMX in three types of permeable pavement surface materials,including permeable bricks,permeable concrete,and permeable asphalt,were studied.The results showed that the variation trends of the three permeable pavement surface materials’ removal efficiency of SMX under different rainfall recurrence intervals were basically the same,with a rapid increase followed by a gradual decrease.The reduction rate of SMX by different permeable pavement systems decreased with increasing rainfall intensity.The concentration of particulate matter had a minor effect on the removal of SMX by permeable pavement surface layers,and all three surface layers maintained a removal rate of over 55% at different concentrations of particulate matter.However,when the concentration of humic acid in the runoff increased,the removal rate of SMX by permeable pavement surface layers would decrease.X-ray fluorescence measurements found that the main chemical components of the three permeable pavement surface materials were Ca O,Si O2,and Mg O.The ionizable hydroxyl groups on the surface of these materials could exchange ions with SMX to achieve adsorption and retention,while the polarity between the surface layer material and SMX could enhance the van der Waals force between molecules and increase the adsorption of SMX by the permeable surface layer. |
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