Removal Of Different Dissolved Organic Matter Chemical Fractions In Road Runoff By The Media Using In Biological Retentions

The dissolved organic matter?DOM?has high activity and can interact with numerous heavy metals and other pollutants by complextion,thereby affecting the migration and transformation of heavy metals and other pollutants.The characteristics of different chemical fractions of DOM and combination with heavy metals in Beijing's road runoff in different periods of rainfall and traffic density were studied.This study examined the effects of different biological retention media on the adsorption and retention of DOM in road runoff,and the changes in the characteristics of DOM chemical fractions in the road runoff after adsorption by different biological retention media.Through the above research,the best medium for removing the DOM of the road runoff is obtained,which provides technical support for the removal of the DOM of the road runoff and chemical fractions.The results are as follows:In order to explore the characteristics of the chemical fraction of dissolved organic matter in the road runoff in Beijing,three-dimensional fluorescence spectroscopy,ultraviolet-visible spectroscopy and FTIR spectroscopy were used to investigate the DOM chemical composition of the road ruuoff under different rainfall and traffic density conditions.The results show that the road runoff DOM in Beijing contains a amount of hydrophobic substances,mainly hydrophobic neutral fractions.The chemical fractions of DOM in the road runoff all contain aromatic protein-like substances,and the hydrophobic fractions also contain a large amount of fulvic acid-like substances.The DOM hydrophobic fraction of road runoff has a higher degree of aromatization and a lower degree of humification,while the hydrophilic fraction is the opposite.The road runoff DOM acidic component contains functional groups such as isomerized carboxyl group and benzene ring,and the basic component and neutral component mostly contain functional groups such as ether bonds,ester groups,phenols and alcohols.Traffic density has no obvious effect on the composition and characteristics of the DOM chemical fractions of road rainwater runoff,but only affects the content of each chemical fractions;the greater the traffic density,the greater the content of each chemical component and the degree of aromatization The higher,the lower the degree of humification..The complexation between the hydrophilic fraction and the heavy metals is greater than the hydrophobic fraction.Cu²⁺and Pb²⁺and the road runoff DOM have a better complexing effect;and Cu²⁺is easier to complex with the HiA fraction,and Pb²⁺is easier to HiB.Based on the pollution characteristics of the DOM in the Beijing road runoff,the adsorption performance of the enhanced biological retention medium on the DOM in the road runoff was investigated.The results showed that the adsorption process of different biological retention media on the DOM of road runoff are controlled by chemisorption and are monolayer adsorption.Under acidic conditions and weakly alkaline conditions,the three media have better adsorption effect on runoff DOM;mainly because of electrostatic adsorption and coordination complexation.The presence of heavy metal ions can inhibit the adsorption of DOM by iron oxide and iron-manganese composite oxide media,and promote the adsorption of DOM by aluminum sludge media.All three bioretention media can adsorb the chemical fractions of DOM.The aluminum sludge medium has the strongest ability to adsorb the DOM chemical fractions of runoff,and the best removal effect is the HoA component.The fulvic acid substances in the chemical components of the flow path DOM are more easily adsorbed and removed by biological retention media,and the adsorption and removal effect of protein substances is poor.The humification degree of each chemical component of the flow DOM increased through the medium adsorption back path,and the degree of aromatization decreased.Compared with iron oxide and iron-manganese composite oxide,the aluminum sludge medium has the best removal effect of the DOM chemical components in the flow path.In order to further investigate the effect of the enhanced biological retention medium on the interception and removal of runoff DOM,a biological retention column was built in the laboratory to explore the effect of the biological retention device on the purification and retention of the DOM chemical fractions in the road runoff.It was found that the biological retention device filled with different media had a certain removal effect on each chemical component of the flow path DOM,but the removal effect of the enhanced media device on each component was significantly higher than that of inert media sand.Among them,the removal effects of the HoN,HoA and HiB components are better in different devices,and the removal effects of HoB,HiA and HiN are less;It has little effect on the types of three-dimensional fluorescence peaks in the chemical components of the road runoff DOM,and has a greater influence on the intensity of the fluorescence peaks.The tryptophan-like peak and the threonine-like peak of each chemical component of the effluent from each device had a small change in peak intensity,and the fulvic acid-like peak had a large change in peak intensity.The aluminum sludge device has a certain removal effect on aromatic substances and macromolecular structure substances in each chemical component of DOM.The iron oxide device mainly adsorbs aromatic substances and macromolecular structure substances in acidic components The iron-manganese composite oxide device mainly adsorbs hydrophilic substances and degraded small molecules in the hydrophobic component.