About 91,300 ha of peatlands has been rewetted in western Europe since the mid-1990s. Still, it is unknown how long-term rewetting alters the dissolved organic matter (DOM) concentration, molecular composition, and functional groups. We examined these DOM characteristics in three peatland types subjected to 47- to 231-yr drainage and 18- to 24-yr rewetting to address this knowledge gap. Cold water-extractable DOM was characterized by pyrolysis field ionization mass spectrometry (Py-FIMS) and X-ray absorption near-edge structure (XANES) spectroscopy. The dissolved organic carbon (DOC) concentration in the rewetted forest peatland was 2.7 times higher than in the drained forest peatland. However, rewetting decreased the DOC concentrations by 1.5 and 4 times in the coastal peatland and percolation mire, respectively, compared with their respective drained peatlands at the topsoil horizons. The Py-FIMS analysis revealed that all nine DOM compound classes' relative abundances differed between the rewetted and drained forest peatland with the lower relative abundances of the labile DOM compound classes in the rewetted forest peatlands. However, most DOM compound classes' relative abundances were similar between the rewetted and drained coastal peatlands and percolation mires. The XANES also revealed nine carbon and seven nitrogen functional groups with no apparent differences between the two contrasting management practices. The influence of drainage and rewetting on DOC concentration and molecular composition depends on peatland type, drainage period, rewetting intensity, and peat degradation status that should be considered in future research for understanding DOM transformation and transportation from degraded and restored peatland ecosystems.

中文翻译：

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泥炭地对比管理实践中的溶解有机质浓度、分子组成和功能组

自 1990 年代中期以来，西欧约有 91,300 公顷的泥炭地被重新润湿。尽管如此，长期再润湿如何改变溶解有机物 (DOM) 浓度、分子组成和官能团尚不清楚。我们在经历 47 至 231 年排水和 18 至 24 年再润湿的三种泥炭地类型中检查了这些 DOM 特征，以解决这一知识差距。冷水可提取 DOM 的特征是热解场电离质谱 (Py-FIMS) 和 X 射线吸收近边结构 (XANES) 光谱。再润湿森林泥炭地的溶解有机碳 (DOC) 浓度是排水森林泥炭地的 2.7 倍。然而，再润湿使沿海泥炭地和渗透泥沼中的 DOC 浓度分别降低了 1.5 倍和 4 倍，与它们各自在表土层的排水泥炭地进行比较。Py-FIMS 分析显示，所有九个 DOM 化合物类别的相对丰度在再润湿和排水森林泥炭地之间存在差异，再润湿森林泥炭地中不稳定 DOM 化合物类别的相对丰度较低。然而，大多数 DOM 化合物类别的相对丰度在重新润湿和排水的沿海泥炭地与渗透泥炭地之间是相似的。XANES 还揭示了 9 个碳和 7 个氮官能团，两种对比管理实践之间没有明显差异。排水和再润湿对 DOC 浓度和分子组成的影响取决于泥炭地类型、排水期、再润湿强度、