Key Laboratory of the Three Gorges Reservoir Region's Eco-environment, Ministry of Education, College of Environment and Ecology, Chongqing University, No.174 Shazhengjie, Shapingba, Chongqing 400044, China.
Environ Sci Technol. 2022 Sep 20;56(18):13439-13448. doi: 10.1021/acs.est.2c03524. Epub 2022 Sep 7.
The rapid proliferation of planktonic algae induced by eutrophication and climate warming make algae dissolved organic matter (AOM) an important source of dissolved organic matter (DOM) in surface waters, but the understanding of the link between AOM composition and photo-reactivity/photo-transformation of DOM in aquatic systems is limited. Here, intracellular organic matter (IOM) from was extracted and subjected to molecular weight (MW) fractionation. Results indicated that IOM had lower aromaticity and higher photosensitive activity compared to Suwannee River fulvic acid (SRFA). The photosensitive activity of IOM relied on both its molecular weight distribution and fluorescence components. The IOM fraction with the highest MW proteins had the lowest quantum yields of reactive intermediates (Φ), which increased with the decrease of MW, while the fractions with more low-excitation tyrosine-like components had relatively higher Φ. Parallel factor analysis and high-resolution mass spectrometry revealed that light radiation of IOM resulted in the composition transformation from tryptophan-like and tyrosine-like components to humic-like components, forming less aromatic and more saturated recalcitrant dissolved organic carbon. Our findings provide new insights into the photo-reactivity and photo-transformation of algae-derived organic matters and help to predict DOM formation involved in carbon cycling in water environment.
富营养化和气候变暖导致浮游藻类的快速增殖，使藻类溶解有机物（AOM）成为地表水溶解有机物（DOM）的重要来源，但对水生系统中 AOM 组成与 DOM 光反应/光转化之间联系的理解有限。本研究中，从 中提取了细胞内有机物（IOM）并进行了分子量（MW）分级。结果表明，与苏万尼河富里酸（SRFA）相比，IOM 的芳香度较低，光敏活性较高。IOM 的光敏活性依赖于其分子量分布和荧光成分。MW 最高的蛋白质 IOM 分数具有最低的反应性中间体量子产率（Φ），随着 MW 的降低而增加，而具有更多低激发色氨酸样成分的分数具有相对较高的 Φ。平行因子分析和高分辨率质谱揭示了 IOM 的光辐射导致从色氨酸样和酪氨酸样成分向腐殖质样成分的组成转化，形成较少芳香性和更饱和的难降解溶解有机碳。我们的研究结果为藻类衍生有机物的光反应和光转化提供了新的见解，并有助于预测水环境中碳循环中涉及的 DOM 形成。
