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首页> 美国卫生研究院文献>PLoS Clinical Trials >Use of ESI-FTICR-MS to Characterize Dissolved Organic Matter in Headwater Streams Draining Forest-Dominated and Pasture-Dominated Watersheds
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Use of ESI-FTICR-MS to Characterize Dissolved Organic Matter in Headwater Streams Draining Forest-Dominated and Pasture-Dominated Watersheds

机译：使用ESI-FTICR-MS表征源于森林为主和牧场为主的流域的上游水流中的溶解有机物

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Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) has proven to be a powerful technique revealing complexity and diversity of natural DOM molecules, but its application to DOM analysis in grazing-impacted agricultural systems remains scarce. In the present study, we presented a case study of using ESI-FTICR-MS in analyzing DOM from four headwater streams draining forest- or pasture-dominated watersheds in Virginia, USA. In all samples, most formulas were CHO compounds (71.8–87.9%), with other molecular series (CHOS, CHON, CHONS, and CHOP (N, S)) accounting for only minor fractions. All samples were dominated by molecules falling in the lignin-like region (H/C = 0.7–1.5, O/C = 0.1–0.67), suggesting the predominance of allochthonous, terrestrial plant-derived DOM. Relative to the two pasture streams, DOM formulas in the two forest streams were more similar, based on Jaccard similarity coefficients and nonmetric multidimensional scaling calculated from Bray-Curtis distance. Formulas from the pasture streams were characterized by lower proportions of aromatic formulas and lower unsaturation, suggesting that the allochthonous versus autochthonous contributions of organic matter to streams were modified by pasture land use. The number of condensed aromatic structures (CAS) was higher for the forest streams, which is possibly due to the controlled burning in the forest-dominated watersheds and suggests that black carbon was mobilized from soils to streams. During 15-day biodegradation experiments, DOM from the two pasture streams was altered to a greater extent than DOM from the forest streams, with formulas with H/C and O/C ranges similar to protein (H/C = 1.5–2.2, O/C = 0.3–0.67), lipid (H/C = 1.5–2.0, O/C = 0–0.3), and unsaturated hydrocarbon (H/C = 0.7–1.5, O/C = 0–0.1) being the most bioreactive groups. Aromatic compound formulas including CAS were preferentially removed during combined light+bacterial incubations, supporting the contention that black carbon is labile to light alterations. Collectively, our data demonstrate that headwater DOM composition contains integrative information on watershed sources and processes, and the application of ESI-FTICR-MS technique offers additional insights into compound composition and reactivity unrevealed by fluorescence and stable carbon isotopic measurements.
机译：电喷雾电离傅立叶变换离子回旋共振质谱（ESI-FTICR-MS）已被证明是揭示天然DOM分子的复杂性和多样性的强大技术，但在受牧场影响的农业系统中进行DOM分析的应用仍然很少。在本研究中，我们提供了一个案例研究，即使用ESI-FTICR-MS分析来自美国弗吉尼亚州以森林或牧场为主的集水区的四个水源流的DOM。在所有样品中，大多数分子式为CHO化合物（71.8–87.9％），其他分子系列（CHOS，CHON，CHONS和CHOP（N，S））仅占很小的比例。所有样品都被落在木质素样区域（H / C = 0.7–1.5，O / C = 0.1–0.67）的分子所控制，这表明异源于陆生植物的DOM占主导地位。相对于两个牧场流，两个森林流中的DOM公式更为相似，这是基于Jaccard相似系数和根据Bray-Curtis距离计算出的非度量多维标度得出的。牧草溪流的配方具有较低比例的芳香族配方和较低的不饱和度，这表明牧草土地利用可改变有机质对溪流的贡献。森林溪流中的冷凝芳香结构（CAS）数量更多，这可能是由于在以森林为主的流域中受控燃烧所致，这表明黑碳从土壤转移到溪流中。在15天的生物降解实验中，两种牧草溪流中的DOM的变化程度要比森林溪流中的DOM更大，其H / C和O / C范围的公式类似于蛋白质（H / C = 1.5–2.2，O / C = 0.3-0.67），脂质（H / C = 1.5-2.0，O / C = 0-0.3）和不饱和烃（H / C = 0.7-1.5，O / C = 0-0.1）最多生物反应基团。在结合光和细菌的孵育过程中，优先去除了包括CAS在内的芳族化合物，这支持了黑碳对光变化不稳定的观点。总的来说，我们的数据表明，源头DOM成分包含有关流域来源和过程的综合信息，并且ESI-FTICR-MS技术的应用为荧光和稳定碳同位素测量未揭示的化合物成分和反应性提供了更多见解。

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