The Diversification Of Dissolved Organic Matter During The Freezing And Thawing Processes Of Water

It was studied the partition of dissolved organic matter(DOM) fractions and haloacetic acids(HAAs) precursors in water-ice system during the freezing processes of water by the indoor simulating tests, the realease of DOM fraction in ice system during the thawing processes of water, the effect of freeze/thaw treatment on the structure and properties of DOM. DOM was fractionated using XAD resins into five fractions: hydrophobic acid(HPO-A), hydrophobic neutral(HPO-N), transphilic acid(TPI-A), transphilic neutral(TPI-N) and hydrophilic fraction(HPI). The results showed that the freezing rate of water samples containing acid fractions was higher than that of neutral fractions. DOC concentrations for five DOM fractions in liquid phase increased with the increase of freezing time, presenting the freeze-concentration effect, during the freezing processes of water. HAAs precursors in five DOM fractions were more liable to be concentrated in liquid phase, as compared with the bulk DOM represented by dissolved organic carbon(DOC). HPI, among the five DOM fractions, was the main HAAs precursors. There was correlation between UV-254 and HAAFP for five DOM fractions in unfrozen liquid samples. Moreover, the linear correlation for HPO-A, TPI-A and HPI achieved very significant levels. However, the correlation between UV-254 and HAAFP for all five DOM fractions in melted ice samples was not significant.DOM fractions will be released significantly in the early chapters of melting ice, when freezing temperatures at the higher(-15℃), ice-like behavior will appear more clearly during this thawing process. Two acidic components like HPO-A and TPI-A exhibit a priority release on a greater degree. Moreover, as compared with the bulk DOM represented by dissolved organic carbon(DOC), aromatic substances and the precursors of generating trihalomethanes and haloacetic acids are preferentially released among DOM fractions. A class of aromatic fluorescent protein substance slowest release behavior, and behavioral differences in the release of four fluorescent substance independent of temperature among 4 fluorescent substance. UV-254 is more suitable than the fluorescent material as an alternative parameter of THMFP and HAAFP.The bulk DOM represented by dissolved organic carbon(DOC) increase after freeze/thaw process, but DOM samples generally lower aromatic substances. For DOM water samples with not immediately determined, it is recommended flash frozen under-50 ℃ treatment saved. Repeated freezing and thawing process enables over two hydrophilic substances DOC concentration increased by a big margin. DOM component fluorescent material is mainly based aromatic proteins and fulvic substances. Five kinds of treatment fluorescent DOM component content decreased After freezing and thawing cycles, and the impact on the hydrophilic component and the excessive hydrophilic component is more significant. Among four fluorescent substance, the impact of freez/thaw on the class and the class of aromatic substances soluble fluorescent protein fluorescence substances most significant fluorescent humic substances Secondly, while the impact of fulvic fluorescent substance weakest.