Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland.
Department of Civil, Environmental and Architectural Engineering, Environmental Engineering Program, University of Colorado, Boulder, CO 80309, USA.
Water Res. 2018 Nov 1;144:64-75. doi: 10.1016/j.watres.2018.06.059. Epub 2018 Jun 27.
Oxidation processes are impacted by the type, concentration and reactivity of the dissolved organic matter (DOM). In this study, the reactions between various types of DOM (Suwannee River fulvic acid (SRFA), Nordic Reservoir NOM (NNOM) and Pony Lake fulvic acid (PLFA)) and two oxidants (ozone and chlorine) were studied in the pH range 2-9 by using a combination of optical measurements and electron donating capacities. The relationships between residual electron donating capacity (EDC) and residual absorbance showed a strong pH dependence for the ozone-DOM reactions with phenolic functional groups being the main reacting moieties. Relative EDC and absorbance abatements (UV or UV) were similar at pH 2. At pH 7 or 9, the relative abatement of EDC was more pronounced than for absorbance, which could be explained by the formation of UV-absorbing products such as benzoquinone from the transformation of phenolic moieties. An increase in fluorescence abatement with increasing pH was also observed during ozonation. The increase in fluorescence quantum yields could not be attributed to formation of benzoquinone, but related to a faster abatement of phenolic moieties relative to fluorophores with low ozone reactivity. The overall OH yields as a result of DOM-induced ozone consumption increased significantly with increasing pH, which could be related to the higher reactivity of phenolic moieties at higher pH. The OH yields for SRFA and PLFA were proportional to the phenolic contents, whereas for NNOM, the OH yield was about 30% higher. During chlorination of DOM at pH 7 an efficient relative EDC abatement was observed whereas the relative absorbance abatement was much less pronounced. This is due to the formation of chlorophenolic moieties, which exert a significant absorbance, and partly lose their electron donating capacity. Pre-ozonation of SRFA leads to a decrease of chloroform and haloacetic acid formation, however, only after a threshold of > ∼50% abatement of the EDC and under conditions which are not precursor limited. The decrease in chloroform and haloacetic acid formation after the threshold EDC abatement was proportional to the relative residual EDC.
氧化过程受溶解有机物 (DOM) 的类型、浓度和反应性的影响。在这项研究中，通过光学测量和电子供体容量相结合的方法，研究了不同类型的 DOM（苏万尼河腐殖酸 (SRFA)、北欧水库 NOM (NNOM) 和小马湖腐殖酸 (PLFA)) 与两种氧化剂（臭氧和氯）之间的反应，pH 值范围为 2-9。残留电子供体容量 (EDC) 与残留吸光度之间的关系显示出与酚类官能团的臭氧-DOM 反应具有很强的 pH 依赖性，酚类官能团是主要的反应部分。在 pH 2 时，相对 EDC 和吸光度的衰减（UV 或 UV）相似。在 pH 7 或 9 时，EDC 的相对衰减比吸光度更为明显，这可以通过酚类部分转化为对苯醌等 UV 吸收产物来解释。在臭氧氧化过程中，还观察到荧光衰减随 pH 值的增加而增加。荧光量子产率的增加不能归因于对苯醌的形成，而是与相对低臭氧反应性的荧光团相比，酚类部分的更快衰减有关。由于 DOM 诱导的臭氧消耗，OH 总产率随着 pH 值的增加而显著增加，这可能与较高 pH 值下酚类部分的更高反应性有关。SRFA 和 PLFA 的 OH 产率与酚含量成正比，而 NNOM 的 OH 产率约高 30%。在 pH 7 时 DOM 的氯化反应中，观察到有效的相对 EDC 衰减，而相对吸光度衰减则不那么明显。这是由于形成了氯代酚类部分，它们具有显著的吸光度，并且部分丧失了电子供体容量。SRFA 的预臭氧化导致三氯甲烷和卤代乙酸的形成减少，但仅在 EDC 衰减超过阈值（>∼50%）且不受前体限制的条件下。阈值 EDC 衰减后三氯甲烷和卤代乙酸形成的减少与相对残留 EDC 成正比。
