Separation And Characterization Of Dissolved Organic Matter With Different Components And Its Effect On Iron Reduction Process Of Alienation

DOM containing complex chemical structures and compositions plays a key role inthe global carbon cycle. Separation and research of DOM with different compositionand different molecular weight can help us to have a better understanding of thecomplex chemical structure, composition and source of DOM. Resin absorption andultrafiltration membrane filtration were applied in current experiment to separate andcharacterize different components of the DOM with different molecular weight.Ultraviolet-visible spectrophotometer, TOC analyzer, high performance liquid sizeexclusion chromatography (HPLSEC) and three-dimensional fluorescence spectrumwere applied to study the characteristics of different component of DOM. Furthermore,we also paid much attentions to the influence of different component DOM withdifferent molecular weight influence from different sample sites on iron dissimilatoryreduction of lepidocrocite.The results of the study showed that, middle molecular weight and small molecularweight material were the main part of the DOM from different sample sites. XAD-8andXAD-4components were mainly composed of small molecular weight of the material(<1kDa); Eluted components was mainly composed of middle molecular weightmaterial (1kDa-10kDa); From different sources or different components of the DOMwas content with the least large molecular weight material(>10kDa). The differences ofthe UV spectrum among the DOM from different sources were obvious. The signal ofUV spectrum of WN-N-Eluted was higher than those of other eluted.The signal of UVspectrum UV of the DOM separated XAD-8and XAD-4in different sources weredecreased with the increase of detect wavelength. UVs of the different component from Grand Canal in Yangzhou were the minimum. There were three different fluorescencepeak: fluorescence peak A(Ex455-485nm/Em525-538nm), humic-like substancefluorescence peak B(Ex305-325nm/Em379-446nm) and albuminoid fluorescencepeak C（Ex285-290nm/Em354-372nm）.To the different molecular weight DOM which from the same source was not thelarger the E250/E365, the greater the molecular weight was. SUVA254can reflect aromaticdegree of humus substance to some extent. It also had a certain relationship with thetype of DOM. However, this rule didn’t apply to the same source under differentmolecular weight of DOM. As for the different molecular weights’ DOM of Yangzhousurface, Grand Canal in Yangzhou, Sludge and Tangyu, had the same kind offluorescence peak. That was the humic-like fluorescence peak B. The only differencewas the fluorescence intensity. For the Sludge group (pH unregulated), the maindifference from the former four groups was that there was Protein-like fluorescencepeak C in addition under the eluted composition of WNE-N-0.45, WNE-N-50k andWNE-N-3k. For the Humic acid group, there was an peak A (Ex440-470nm/Em517-534nm) in addition except the humic-like fluorescence peak B in the twogroups of FZ-8and FZ-4. Eluted mainly was Protein-like fluorescence peak C. Thesame components of DOM, the fluorescence intensity decreased with the decrease ofthe molecular weight. The same source of DOM, the fluorescence intensity ofcomponent XAD-8was the strongest, the fluorescence intensity of component XAD-4took second place, the fluorescence intensity of the eluted was the minimum.In biological conditions, samples from the same source, their effect onlepidocrocite’s reduction differ from the molecular weights of the DOM from the sameseparation component. Among them, the most obvious effects on lepidocrocitereduction process was by using YB-8-0.45and WN-8-0.45in hydrophobic materialseparated by XAD-8resin. Among the transitional substances isolated by XAD-4resin,the most obvious effects on lepidocrocite reduction process was by using the DOMwhich molecular weight was under50kDa. The final eluted, DOM with differentmolecular weights in the hydrophilic substances had no effect on lepidocrocitereduction process. As long as the concentration of Fe (II) had reached a steady state, thesystem could be observed in khaki color. And the degree of the color depended on the effects of the lepidocrocite reduction caused by DOM. In the system of DOM which thedegree of reduction was deep could be observed the existence of black matter.Reduction of the effect was poorer system unchanged lepidocrocite in yellow color. Inthe process of microbial reduction of lepidocrocite, system by yellow gradually turn intoblack, because lepidocrocite gradually transformed into magnetite.