Temporal patterns and drivers of CO₂ emission from dry sediments in a groyne field of a large river

Abstract. River sediments falling dry at low water levels are sources of CO2 to the atmosphere. While general relevance emissions from has been acknowledged and some regulatory mechanisms have identified, knowledge on temporal dynamics is still sparse. Using a combination high-frequency measurements two field campaigns we thus aimed identify processes responsible for assess large German river. were largely driven by microbial respiration in sediment. Observed fluxes could be explained patterns responses sediment rates measured laboratory incubations. We exclude groundwater as significant source because concentration was too explain fluxes. Furthermore, not related radon fluxes, which used trace groundwater-derived degassing CO2. strongly regulated temperature resulting diurnal fluctuations with peaking during day. The temperature–CO2 flux relation exhibited hysteresis highlights effect transport makes it difficult dependence simple linear regressions. response incubations identical. Also deeper layers apparently contributed correlated thickness unsaturated zone, increasing distance local level Rain events lowered river probably blocking Terrestrial vegetation growing exposed greatly increased respiratory emissions. conclude that regulation complex. Diurnal mandatory even uptake dark phototrophic micro-organisms considered when assessing impact rivers.