Seasonal shifts in diel pCO2 variations investigated by high-frequency sensor measurements in the lower Ganges River in 2018-2019

High-frequency sensor measurement was combined with dissolved organic matter (DOM) characterization to investigate diel and seasonal variations in the partial pressure of CO2 (pCO2) in the lower Ganges, near Hardinge Bridge (24°03'57.04 N, 89°01'42.85 E). Continuous measurement of pCO2 was conducted every month for 12–13 hours from May 2018 to April 2019, with an extended deployment of 48 hours continuous monitoring in March 2019. Water samples were also collected monthly to measure biodegradable dissolved organic carbon and optical properties of DOM including three fluorescent DOM components. CO2 flux and apparent oxygen utilization were calculated based on CO2 and dissolved oxygen measurements.