Spatiotemporal variability of lake pCO2 and CO2 fluxes in a hemiboreal catchment

In both methods (manual pCO2aq and sensor pCO2aq), the pCO2aq (μatm) in the chamber after equilibration was proportional to the water concentration according to Henry’s law and was calculated as ¼ ppmpCO P chamber2 total 106 (2) where Ptotal is the air pressure (μatm) and ppmchamber is the mixing ratio of CO2 inside the chamber head- space measured by the sensor or in the manual samples (ppm). [...] The arrows at the top of the panels and the numbers above them show the average wind direction and speed (m s1) during the 24 h deployment period, and the cross arrows denote changing winds. [...] likely due to the position of the lake further downstream in the catchment (Figure 1) and disconnected from the high pCO2aq in the headwaters. [...] Thus, in Följesjön the higher concentration of CO2 in the summer months was likely due to the more efficient warming of the shallow water column and the higher respiration rates supported by the warmer water. [...] In our data, there was a delay in cap- turing the peak pCO2aq because of the chamber design and the dependence on turbulence in the surface water to equilibrate the gas in the chamber (see section 2.2).