Fractionation of Dissolved Organic Matter by Co-Precipitation with Iron: Effects of Composition
Fractionation of Dissolved Organic Matter by Co-Precipitation with Iron: Effects of Composition
复制标题
通过与铁共沉淀分离溶解的有机物：成分的影响
DOI：
10.1007/s40710-017-0281-4
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发表时间：
2018-03-01
影响因子：
4.4
通讯作者：
Jaffe, Rudolf
中科院分区：
文献类型：
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作者：
Du, Yingxun;Ramirez, Cesar E.;Jaffe, Rudolf
溶解有机物(DOM)与不同物理化学形态的铁(Fe)之间的相互作用是有机碳循环中重要的生物地球化学过程。由于气候变化和土地利用变化等人为活动的影响，陆源DOM进入水生系统的负荷量不断增加，从而增加了水生生态系统中有机质的酸度。虽然已经报道了DOM与Fe的络合作用以及DOM在铁氧化物和氢氧化物上的吸附，但关于DOM组成对共沉淀过程的影响还知之甚少。在pH 4.0-8.0范围内，研究了两种DOM标准，即苏万尼河标准腐植酸标准II(SRHA)和北欧水生黄腐酸参考值(NAFA)与铁的共沉淀。用多种分析方法系统地表征了与铁共沉淀后残留的DOM，揭示了DOM的分子分级。降低pH值有利于SRHA或NaFA与Fe的共沉淀，在pH=4.0时，当Fe(III)/C>0.12时，SRHA或NaFA的DOC可被去除约70~80%。在共沉淀过程中，SUVA254和腐殖化指数(Hix)的下降表明，芳香性较高的DOM优先与Fe共沉淀。DOM的相对分子质量影响共沉淀的选择性，高相对分子质量的DOM表现出较强的亲和力。DOM与Fe的共沉淀明显依赖于DOM的组成，表现出陆地上普遍存在的类腐殖质>；微生物类腐殖质组分的亲和力顺序。激发发射基质荧光结合平行因子分析(EEM-PARAFAC)组分的反应性和相对丰度的差异解释了SRHA和NAFA对DOC去除效率的差异。这项研究提供了DOM组成对其分馏的直接影响，特别是通过与Fe的共沉淀，并表明对于富含铁基(氧)氢氧化物的水生体系和环境氧化还原界面，DOM与铁的共沉淀可能会影响水相的光学性质，并代表了陆源有机质的重要汇。
Interactions between dissolved organic matter (DOM) and different physical-chemical forms of iron (Fe) represent important biogeochemical processes in the organic carbon cycle. Due to the effect of climate change and anthropogenic activities such as land-use change, the loading of terrestrial DOM into aquatic systems is increasing, and thus, enhancing the organic matter-based acidity in aquatic ecosystems. While complexation of Fe with DOM and the sorption of DOM on iron oxides and (oxy)hydroxides have been reported, less is known about how co-precipitation processes might affect by DOM composition. Here the co-precipitation of two DOM standards, namely the Suwannee River Standard Humic Acid Standard II (SRHA) and Nordic Aquatic Fulvic Acid Reference (NAFA), with Fe was investigated in a pH range of 4.0–8.0. The DOM remaining after co-precipitating with Fe was systematically characterized by various analytical methods to reveal the molecular fractionation of DOM. The co-precipitation of SRHA or NAFA with Fe was enhanced by decreasing the pH, where at pH 4.0, about 70~80% DOC of SRHA or NAFA was removed at Fe(III)/C ratios higher than 0.12. The decrease in SUVA254and the humification index (HIX) during the co-precipitation process suggests that DOM with high aromatic character was preferentially co-precipitated with Fe. DOM molecular weight influenced the selectivity to co-precipitation, with high molecular weight (HMW) DOM showing a stronger affinity. DOM co-precipitation with Fe was clearly dependent on DOM composition, showing an affinity order of terrestrial humic-like> ubiquitous humic-like> microbial humic-like components. The difference in the reactivity and the relative abundances of excitation emission matrix fluorescence combined with parallel factor analysis (EEM-PARAFAC) components explained the difference in DOC removal efficiency between SRHA and NAFA. This study provides direct insights into the effects of DOM composition on its fractionation specifically through co-precipitation with Fe, and suggests that for aquatic systems rich in iron-based (oxy)hydroxides, and for environmental redox interfaces, co-precipitation of DOM with iron might affect optical properties of the aqueous phase, and represent an important sink for terrestrially-derived organic matter.