生活垃圾生物炭源溶解性有机质分馏和络合重金属的作用

Fractionation of dissolved organic matter from domestic waste biochar and its complexation with heavy metals

为揭示生活垃圾衍生的溶解性有机质的成分及其与重金属的相互作用机制,利用固相萃取与分馏技术,将生活垃圾衍生的溶解性有机质进行分馏,并采用荧光猝灭滴定与光谱分析探究各馏分与Cu的络合作用.结果表明,分馏共得到4种组分,分别为疏水酸性组分、疏水中性组分、疏水碱性组分和亲水性组分,按C含量分别占5.64%、64.37%和11.66%和18.33%.在这4个组分的三维荧光光谱中观察到5个荧光峰:A(Ex/Em=240/425 nm,类富里酸物质)、C1和C2(Ex/Em=270/425 nm和Ex/Em=315/412 nm,类腐殖酸物质)、T1(Ex/Em=240/354 nm,类色氨酸物质)和T2(Ex/Em=275/358 nm,微生物代谢产物);其中在疏水中性组分中观察到3个荧光峰A、C1和C2.Cu对疏水中性组分的络合顺序为:405—450 nm>383 nm>397 nm>323—340 nm;Ryan-Weber模型拟合表明络合稳定常数(lgK):C2(4.10)>A(3.97)>C1(3.91);这表明与Cu络合时类腐殖酸物质优先于类富里酸物质.总体来说,生活垃圾衍生的溶解性有机质的主要成分为疏水中性组分,与Cu络合可以改变疏水中性组分的分子微环境,从而改变Cu的形态和归趋,影响其生物有效性和生态毒性.

In order to reveal the composition and interaction mechanism with heavy metals,the dissolved organic matter derived from domestic waste biochar was processed by solid-phase extraction and fractionation techniques,and the complexation of each fraction with Cu was explored by fluorescence quenching titration and spectral analyses.The results showed that four components were obtained by fractionation,and they were hydrophobic-acidic component,hydrophobic-neutral component,hydrophobic-base component,and hydrophilic substance,accounting for 5.64%,64.37%,11.66%and 18.33%respectively according to the content of C.Five fluorescence peaks were observed in the three-dimensional fluorescence spectra of these four components:A(Ex/Em=240/425 nm,fulvic acid like substance),C1 and C2(Ex/Em=270/425 nm and Ex/Em=315/412 nm,humic acid like substance),T1(Ex/Em=240/354 nm,tryptophan like substance)and T2(Ex/Em=275/358 nm,microbial metabolite).In addition,three fluorescence peaks(A,C1 and C2)were observed in the hydrophobic-neutral component.The complexation order of Cu with hydrophobicneutral components was 405—450 nm>383 nm>397 nm>323—340 nm,and the Ryan Weber model fitting showed that the complexation stability constant(lgK)was C2(4.10)>A(3.97)>C1(3.91).Furthermore,it shows that humic-acid like substances are superior to fulvic-acid like ones when being complexed with Cu.In general,the main components of dissolved organic matter derived from domestic waste are hydrophobic-neutral components and its complexation with Cu can change the molecular microenvironment of the hydrophobic-neutral component,and mediate the morphology and fate of Cu in term of bioavailability and ecotoxicity.