Biodegradability of riverine dissolved organic carbon in a Dry-hot Valley Region: Initial trophic controls and variations in chemical composition

Autor: Maofei Ni, Siyue Li
Rok vydání: 2019
Předmět:
Zdroj: Journal of Hydrology. 574:430-435
ISSN: 0022-1694
DOI: 10.1016/j.jhydrol.2019.04.069
Popis: Aquatic carbon (C) loss is mostly driven by in-situ mineralization of dissolved organic carbon (DOC) and leads to autonomous carbon dioxide (CO2) emissions to the atmosphere. However, limited studies have examined the biodegradability of riverine DOC, especially for the initial trophic controls of DOC biodegradation (%BDOC) and variations in dissolved organic matter (DOM) chemical composition. In this study, we employed a laboratory incubation experiment to determine the riverine %BDOC, temperature sensitivity (Q10 value), nutrients and DOM optical properties in a subtropical river in the Dry-hot Valley Region. We observed the %BDOC at 30 °C (52 ± 19.8%) was significantly higher than that at 20 °C (34 ± 19.9%) with an average Q10 value of 2 ± 1.7. Decreases in a254, a350 values indicated that the aromatic and lignin fractions were decomposed, while increases in E2:E3 and decreases in E4:46 values suggested that large molecular DOMs were incompletely degraded and accumulated after 56-day incubations. The %BDOC was negatively correlated with the DOC:TDP ratio, which suggested that P availability was a dominant control in aquatic microbial respiration. Our results conclude that temperature and trophic status regulate biodegradability of DOC, and also stimulate the incomplete degradation of recalcitrant fraction in DOMs.
Databáze: OpenAIRE
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