Litter decomposition enhances volatile organic compound emission from a freshwater wetland: insights from year-round in situ field experiments

Fang, Hua; Wu, Ting; Ma, Shutan; Jia, Qina; Zan, Fengyu; Zhao, Juan; Zhang, Jintao; Yang, Zhi; Xu, Hongling; Huang, Yuzhe; Wang, Xinming

Plant litter could be a potential source of atmospheric volatile organic compounds (VOCs). Previous studies are mostly restricted to forest litter, but VOC budget of wetlands, especially freshwater wetlands, resulting from litter decomposition remains largely unexplored. Here we performed in-situ VOC flux measurements in a freshwater wetland and three treatments including A (no litter addition), B (1.4 kg litter) and C (2.8 kg litter) were designed to investigate impacts of litter decomposition on wetland-atmosphere exchange of VOCs. During year-round litter decomposition, average fluxes of net VOCs for B and C were 5.93±3.13 μg m -2 h -1 and 8.30±4.00 μg m -2 h -1, respectively, significantly higher than that of A (2.90±2.74 μg m -2 h -1). These results suggested that freshwater wetland was a potential source of atmospheric VOCs and litter decomposition enhanced VOC release. Net VOC flux showed clear seasonal patterns and was highly correlated with ambient temperature ( p<0.05). In general, higher positive VOC fluxes were observed in hot summer, while lower positive VOC fluxes or negative VOC fluxes were observed in cold winter. Moreover, the release (positive flux) or uptake (negative flux) of VOCs varied to chemical groups. Specifically, non-methane hydrocarbons (NMHCs) including alkanes, alkenes and aromatics showed positive net fluxes, and increased with added litter. Halocarbons showed a negative net flux in A, but positive net fluxes in B and C. While oxygenated volatile organic compounds (OVOCs) showed negative net fluxes in both A and B, and switched to a positive flux in C. Positive net fluxes of volatile organic sulfide compounds (VOSCs) were observed in three treatments. According to flux variations of specific VOC group, it has been suggested that temperature-driven biotic and abiotic processes co-modulated VOC release or uptake occurring in the freshwater wetland.

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Fang, Hua / Wu, Ting / Ma, Shutan / et al: Litter decomposition enhances volatile organic compound emission from a freshwater wetland: insights from year-round in situ field experiments. 2024. Copernicus Publications.

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