Carbon dioxide, methane, and dissolved carbon dynamics in an urbanized river system

Estimates of greenhouse gas evasion from rivers have been refined over the past decades to constrain their role in global carbon cycle processes. However, despite 55% human population living urban areas, had limited attention. We monitored dynamics an urbanized river (River Kelvin, 331 km2, UK) explore drivers dissolved lateral and vertical export. Over a 2-year sampling period, riverine methane (CH4) dioxide (CO2) concentrations were consistently oversaturated with respect atmospheric equilibria, leading continual degassing atmosphere. Carbon stable isotopic compositions (?13C) indicated that terrestrially derived comprised most CH4 CO2 (CO2*) load while inorganic (DIC) groundwater was main form DIC. The CH4, CO2*, DIC primarily hydrology-controlled, is, [CH4] [CO2*] both increased elevated discharge, total [DIC] decreased discharge proportion biologically increasing discharge. concentration organic (DOC) showed weak relationship hydrology summer autumn likely influenced by combined sewer overflows. emission atmosphere is estimated be 3.10 ± 0.61 kg C·m?2·yr?1 normalized water surface area, more than 99% emitted as CO2. Annual loss coastal estuary approximately 4.69 0.70 Gg C yr?1, annual export double DOC. Per unit River Kelvin smaller source natural rivers/streams but shows fluxes DOC under comparable conditions. This research illustrates systems may on demonstrates potential tight link between urbanization