![]() Carbon stable isotopic compositions (δ13C) indicated that terrestrially derived carbon comprised most of the riverine CH4 and dissolved CO2 (CO2*) load while dissolved inorganic carbon (DIC) from groundwater was the main form of riverine DIC. ![]() Over a 2‐year sampling period, riverine methane (CH4) and carbon dioxide (CO2) concentrations were consistently oversaturated with respect to atmospheric equilibria, leading to continual degassing to the atmosphere. #Dieter der film streamcloud driversWe monitored carbon dynamics in an urbanized river (River Kelvin, 331 km2, UK) to explore the drivers of dissolved carbon lateral and vertical export. However, despite 55% of the human population living in urban areas, urban rivers have had limited attention. Based on these findings, we hypothesise that the cyclic periodicity of fluxes of biogenic gases from frequently intermittent streams (wet and dry cycles ranging from days to weeks) and seasonally ephemeral watercourses (dry for months at a time) are likely to differ, and therefore these differences should be considered when integrating transient systems into regional carbon budgets and models of global change.Įstimates of greenhouse gas (GHG) evasion from rivers have been refined over the past decades to constrain their role in global carbon cycle processes. Temporal shifts in water depth and site-specific ephemerality were key drivers of carbon dynamics in the upper Jamison Creek watercourse. CH4–C fluxes increased 19-fold over the duration of the initial, longer wet-cycle from 0.1 to 1.9 mmol m⁻² day⁻¹. Rainfall increased background water–air CO2–C fluxes by up to 780% due to an increase in gas transfer velocity in the otherwise still waters. Soil–air evasion rates were approximately equal to those of water–air evasion. After accounting for temporal changes in the ratio of wet versus dry streambed hydraulic radius, total CO2–C fluxes ranged from 12 to 156 mmol m⁻² day⁻¹, with an integrated daily mean of 61 ± 25 mmol m⁻² day⁻¹. ![]() Water column excess CO2 ranged from −11 to 1600 μM, and excess CH4 from 1 to 15 μM. ![]() In this study we quantify the spatiotemporal variability in CO2 and CH4 concentrations and fluxes of an intermittent first-order stream over three consecutive wet and dry cycles spanning 56 days, to assess how hydrologic phase transitions influence greenhouse gas evasion. Ephemeral streams and wetlands are characterized by complex cycles of submersion and emersion, which influence the greenhouse gas flux rates. ![]()
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