Environmental Geosciences, Centre for Microbiology and Environmental Systems Science, University of Vienna, Althanstraße, 1090 Wien, Austria.
Department of Soil and Water Sciences, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 7610001, Israel.
Environ Sci Process Impacts. 2020 Sep 23;22(9):1888-1897. doi: 10.1039/d0em00267d.
Dissolved organic matter (DOM) is ubiquitous in aquatic environments where it interacts with a variety of particles including carbonaceous materials (CMs). The complexity of both DOM and the CMs makes DOM-CM interactions difficult to predict. In this study we have identified the preferential sorption of specific DOM fractions as being dependent on their aromaticity and molecular weight, as well as on the surface properties of the CMs. This was achieved by conducting sorption batch experiments with three types of DOM (humic acid, Suwannee River natural organic matter, and a compost extract) and three types of CMs (graphite, carbon nanotubes, and biochar) with different geometries and surface complexities. The non-adsorbed DOM fraction was analyzed by size exclusion chromatography and preferentially sorbed molecular weight fractions were analyzed by UV/vis and fluorescence spectroscopy. All three sorbent types were found to preferentially sorb aromatic DOM fractions, but DOM fractionation depended on the particular combination of sorbent and sorbate characteristics. Single-walled carbon nanotubes only sorbed the smaller molecular weight fractions (<1 kDa). The sorption of smaller DOM fractions was not accompanied by a preference for less aromatic compounds, contrary to what was suggested in previous studies. While graphite preferentially sorbed the most aromatic DOM fraction (1-3 kDa), the structural heterogeneity of biochar resulted in reduced selectivity, sorbing all DOM > 1 kDa. The results explain the lack of correlation found in previous studies between the amount of aromatic carbon in a bulk DOM and its sorption coefficient. DOM sorption by CMs was generally controlled by DOM aromaticity but complex sorbent surfaces with high porosity, curvatures and functional groups strongly reduced the importance of aromaticity.
溶解有机质（DOM）在水生环境中普遍存在，与包括碳质材料（CMs）在内的各种颗粒相互作用。DOM 和 CMs 的复杂性使得 DOM-CM 相互作用难以预测。在这项研究中，我们已经确定了特定 DOM 分数的优先吸附取决于它们的芳香度和分子量，以及 CMs 的表面性质。这是通过用三种类型的 DOM（腐殖酸、苏万尼河天然有机物和堆肥提取物）和三种类型的 CMs（石墨、碳纳米管和生物炭）进行吸附批量实验来实现的，这些 CMs 具有不同的几何形状和表面复杂度。非吸附的 DOM 部分通过尺寸排阻色谱法进行分析，优先吸附的分子量部分通过 UV/vis 和荧光光谱法进行分析。发现所有三种吸附剂类型都优先吸附芳香族 DOM 分数，但 DOM 分级取决于特定的吸附剂和吸附质特性组合。单壁碳纳米管仅吸附较小分子量的分数（<1 kDa）。与先前的研究结果相反，较小 DOM 分数的吸附并不伴随着对较少芳香化合物的偏好。虽然石墨优先吸附最芳香的 DOM 分数（1-3 kDa），但生物炭的结构异质性导致选择性降低，吸附所有 DOM > 1 kDa。研究结果解释了先前研究中在大量 DOM 中的芳香碳含量与其吸附系数之间缺乏相关性的原因。CM 对 DOM 的吸附通常受 DOM 芳香度控制，但具有高孔隙率、曲率和官能团的复杂吸附剂表面强烈降低了芳香度的重要性。
