A Studay Of Complexation Of DOM In Biogas Slurry With Typical Heavy Metals

As a by-product of biogas project,biogas slurry is widely used in crop fertilizer,which has an important impact on soil environment.As the most active substance in biogas slurry,DOM contains a large number of unsaturated functional groups,which can complex with heavy metal ions in soil,thus affecting the migration and transformation of heavy metals and reducing the absorption efficiency of plants on heavy metals.This article took straw biogas slurry DOM(JDOM)and cow dung biogas slurry DOM(NDOM)as the research object.The structure of JDOM and NDOM and the complexation mechanism with Cu(Ⅱ),Cr(Ⅲ),Pb(Ⅱ),Fe(Ⅲ),Zn(Ⅱ)and Cd(Ⅱ)were researched by fluorescence quenching titration combines with three-dimensional fluorescence spectrum,synchronous fluorescence spectrum,parallel factor analysis and two-dimensional correlation analysis.The results of research indicate that:(1)Both JDOM and NDOM contained two protein-like fluorescences and three humiclike fluorescences with relatively large contents in the three-dimensional fluorescence spectra.and there was no fluorescence quenching of Cd(Ⅱ)and Zn(Ⅱ)with JDOM and NDOM.According to the LogK,the complexation ability of JDOM was stronger than that of NDOM,and the complexation ability of protein-like substances was stronger than that of humic-like substances.(2)PARAFAC(Parallel Factor Analysis)divided JDOM into five components,contained protein-like substances and humic-like substances.NDOM has one more component C6 than JDOM,which represents both protein-like substances and protein-like substances.JDOM and NDOM had the best C3 quenching effect among them.According to the LogK,it can be concluded that Cu(Ⅱ),Cr(Ⅲ),Pb(Ⅱ)and Fe(Ⅲ)have different order of complexation ability with JDOM and NDOM.(3)The results of two-dimensional correlation synchronous spectroscopy show that JDOM and NDOM were more sensitive to the heavy metals of Cu(Ⅱ),Cr(Ⅲ),Pb(Ⅱ)and Fe(Ⅲ)in the short-wavelength band than to the long-wavelength band.However,the sensitivity sequence of JDOM and NDOM with Cu(Ⅱ),Cr(Ⅲ),Pb(Ⅱ)and Fe(Ⅲ)was different.Moreover,the sensitivity of Cu(Ⅱ)and JDOM was stronger than that of NDOM while the other three metals were weaker than that of NDOM.According to the LogK,the complexation order of JDOM and NDOM was also different.From the above conclusions,it can be seen that JDOM and NDOM contained a large number of protein-like substances and humic-like substances,and there was no fluorescence quenching of Cd(Ⅱ)and Zn(Ⅱ).The complexation point position,complexation ability and complexation sequence of JDOM and NDOM with Cu(Ⅱ),Cr(Ⅲ),Pb(Ⅱ)and Fe(Ⅲ)were different.The protein-like substances of JDOM and NDOM had stronger complexing ability to Cu(Ⅱ),Fe(Ⅲ),Cr(Ⅲ)and Pb(Ⅱ)than to humic-like substances,and JDOM had stronger complexing ability than NDOM.