Tetracycline belongs to amphoteric compounds,containing phenolic hydroxyl groups and enol hydroxyl groups with a weak acidity as well as dimethylamino groups with a weak alkalinity.Therefore,the hydrophobicity and hydrophilicity of dissolved organic matter(DOM)may affect its chelating abilities with tetracycline.Two types of solid-phase extraction columns were used to extract and fractionate DOM from domestic waste biochar,resulting in following four fractions:hydrophobic acidic component(HOA),hydrophobic neutral component(HON),hydrophobic alkaline component(HOB),and hydrophilic component(HIS).The UV spectral data showed that HON and HOB were mainly of hydrophobic components,with a higher degree of aromatization,and their values of SUVA254 and SUVA260 are 6.22-9.90 Lmg-1·m-1 and 5.76-9.44 L mg-1·m-1.However,HIS was mainly composed of hydrophilic components,with SUVA254 and SUVA260 both being 0.46 L mg-1m-1.DOM fractionation increased the fluorescence values of HOB and HON while significantly reduced the fluorescence values of HIS,but did not affect the distribution of microbial humus Cl(80.7％-84.6％)and terrestrial humus C2(15.4％-19.3％)in each fraction.The absorption spectra of DOM and three fractions(HON,HOB,and HIS)increased with increasing tetracycline concentrations,and the kq values(0.90 × 1012-3.89 × 1012 L·mol-1·s-1)in the Stern Volmer Equation were much greater than the maximum scattering collision quenching constant(2 x 1010 L·mol-1·s-1);therefore,TC-DOM belonged to static quenching.On the contrary,the absorption spectra of DOM and three fractions(HON,HOB,and HIS)increased with increasing tetracycline concentrations,belonging to static quenching.The absorption peaks near 275 and 356 nm were linked to the characteristic peaks of tetracycline.The complexation reaction of tetracycline with DOM mainly occurred on microbial humus(Cl),while the complexation of terrestrial humus(C2)was not obvious due to its low relative content.In addition,HON-C1 complexation with TC was unstable(lgKb=5.43)due to limited binding sites(n=1.22),while HON-C2 complexation with TC was stable(lgKb=8.47)because of multiple binding sites(n=2.06).The number of binding sites and binding stabilities of DOM-C1,HOB-C1,and HOB-C2 were between HON-C1 and HON-C2.In summary,DOM has significant differences in the binding capacity of hydrophobic and hydrophilic components to tetracycline,which may affect the ecotoxicity,migration and transformation capacity of tetracycline in the environment.
关键词
生活垃圾生物炭/固相萃取与分馏/荧光猝灭/三维荧光光谱/同步光谱/四环素/结合位点方程/疏水性
Key words
domestic waste biochar/solid-phase extraction and fractionation/fluorescence quenching/three-dimensional fluorescence spectra/synchronous spectrum/tetracycline/binding site equation/hydrophobicity
维普
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