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标题：Seasonal and spatial variability of the partial pressure of carbon dioxide in the human-impacted Seine River in France
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作者：Audrey Marescaux ; Vincent Thieu ; Alberto Vieira Borges 等
期刊名称：Scientific Reports
电子版ISSN：2045-2322
出版年度：2018
卷号：8
期号：1
页码：13961
DOI：10.1038/s41598-018-32332-2
语种：English
出版社：Springer Nature
摘要：Carbon evasion from rivers is an important component of the global carbon cycle. The intensification of anthropogenic pressures on hydrosystems requires studies of human-impacted rivers to identify and quantify the main drivers of carbon evasion. In 2016 and 2017, four field campaigns were conducted in the Seine River network characterized by an intensively cropped and highly populated basin. We measured partial pressures of carbon dioxide (pCO₂) in streams or rivers draining land under different uses at different seasons. We also computed pCO₂ from an existing data set (pH, water temperature and total alkalinity) going back until 1970. Here we report factors controlling pCO₂ that operate at different time and space scales. In our study, the Seine River was shown to be supersaturated in CO₂ with respect to the atmospheric equilibrium, as well as a source of CO₂. Our results suggest an increase in pCO₂ from winter to summer in small streams draining forests (from 1670 to 2480 ppm), croplands (from 1010 to 1550 ppm), and at the outlet of the basin (from 2490 to 3630 ppm). The main driver of pCO₂ was shown to be dissolved organic carbon (DOC) concentrations (R² = 0.56, n = 119, p < 0.05) that are modulated by hydro-climatic conditions and groundwater discharges. DOC sources were linked to land use and soil, mainly leaching into small upstream streams, but also to organic pollution, mainly found downstream in larger rivers. Our long-term analysis of the main stream suggests that pCO₂ closely mirrors the pattern of urban water pollution over time. These results suggest that factors controlling pCO₂ operate differently upstream and downstream depending on the physical characteristics of the river basin and on the intensity and location of the main anthropogenic pressures. The influence of these controlling factors may also differ over time, according to the seasons, and mirror long term changes in these anthropogenic pressures.