Abstract
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.
Highlights
In the past, wetlands were considered as unhealthy areas and largely drained leading to a loss of about 64 to 71% of natural wetlands since 1900 because of human activities (Davidson 2014)
Dissolved organic matter (DOM) that consists of watersoluble organic chemicals deriving from the decomposition of plants and living organisms is an important constituent of wetlands
The present study was carried out on a wetland including the Auzon cut-off meander, the Allier River and its tributary Vendage, as well as two aquifers, the alluvial fluvial flow and the watershed ones (Fig. 1). This site looked very appropriate to the study because it offers diversity regarding some parameters among those affecting quality and quantity of DOM: hydrologic conditions, vegetation cover, organic matter inputs, and photochemical and biological degradation processes (Sobek et al 2007; Gao et al 2018; McCullough et al 2019; Queimaliños et al 2019)
Summary
Wetlands were considered as unhealthy areas and largely drained leading to a loss of about 64 to 71% of natural wetlands since 1900 because of human activities (Davidson 2014). DOM absorbs solar light and an important and largely documented property of DOM components is their capacity to degrade organic pollutants under solar light exposure (Shang et al 2015) This property is based on their ability to generate reactive species under. The present study was carried out on a wetland including the Auzon cut-off meander, the Allier River and its tributary Vendage, as well as two aquifers, the alluvial fluvial flow and the watershed ones (Fig. 1) This site looked very appropriate to the study because it offers diversity regarding some parameters among those affecting quality and quantity of DOM: hydrologic conditions, vegetation cover, organic matter inputs, and photochemical and biological degradation processes (Sobek et al 2007; Gao et al 2018; McCullough et al 2019; Queimaliños et al 2019). Principal component analysis (PCA) was performed to explore the relationships between all the variables
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