Wetlands are recognized for the importance of their hydrological function and biodiversity, and there is now a consensus to protect and restore them as well as to complete the knowledge on their functioning. Here, we studied the dissolved organic matter (DOM) of a wetland composed of the Auzon cut-off meander, the Allier River, the alluvial fluvial flow, and watershed aquifer. Water was sampled at different locations, in spring, summer, and autumn. For each sample, DOM was characterized for its chemical and optical properties and its photooxidant capacity through its ability to generate DOM triplet excited states (3DOM*) and singlet oxygen upon simulated solar light exposure. UV-visible and fluorescence indices revealed that DOM was mainly microbial-derived whatever the sampling sites with spatial and temporal variations in terms of aromaticity (5.5-22%), specific UV absorbance at 254 nm (0.28-2.82 L m-1mgC-1), ratio of the absorbance at 254 and 365 nm (4.6-10.8), fluorescence index (1.35-166), and biological index (0.812-2.25). All the samples generated 3DOM* and singlet oxygen, rates of formation of which showed parallel variations. Using principal component analysis (PCA), we found positive correlations between the sensitizing properties of DOM samples and parameters associated to the abundance of low molecular weight and low absorbing chromophores. Moreover, the parameter variation across the wetland reinforced the hydrological movements observed in a previous study, suggesting that these parameters could be used as water connection tracers.

译文

湿地因其水文功能和生物多样性的重要性而得到认可,现在已经达成共识,以保护和恢复湿地并完成有关其功能的知识。在这里,我们研究了由Auzon截流曲折,Allier河,冲积河流流和分水岭含水层组成的湿地的溶解有机物 (DOM)。在春季,夏季和秋季的不同位置对水进行了采样。对于每个样品,DOM的化学和光学性质以及通过在模拟太阳光照射下产生DOM三重激发态 (3DOM *) 和单线态氧的能力来表征其光氧化剂容量。紫外可见和荧光指数表明,DOM主要是微生物来源的,无论采样点在芳香性 (5.5-22%),254 nm (0.28-2.82 L m-1mgC-1) 的特定紫外吸收,在254和365 nm处的吸光度比 (4.6-10.8),荧光指数 (1.35-166) 和生物指数 (0.812-2.25)。所有样品均产生3DOM * 和单线态氧,其形成速率显示出平行变化。使用主成分分析 (PCA),我们发现DOM样品的敏化特性与与低分子量和低吸收发色团的丰度相关的参数之间存在正相关。此外,整个湿地的参数变化加强了先前研究中观察到的水文运动,表明这些参数可以用作水连接示踪剂。

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