Atmospheric deposition coupled terrestrial export of organic carbon in Ganga River (India): linking cross-domain carbon transfer to river DOC

The atmosphere–land–water connectivity of dissolved organic carbon (DOC) is not altogether accounted in major rivers of India despite recent researches highlighting its importance. We studied the coupled effect of atmospheric deposition (AD) and local land use on DOC buildup in Ganga River for a period of 6 years. The AD-OC input increased consistently over time and there was over 1.5- to 1.8-fold increase in 2012 relative to 2007. Microbial activity and water soluble organic carbon (WSOC) in sub-catchment and DOC in land surface runoff increased consistently over time along the gradient of AD input. The river DOC showed positive correlation (R2 = 0.24–0.84; p<0.001) with AD-OC and runoff DOC and WSOC showed positive correlation (R2 = 0.96; p<0.001) with soil microbial activity. Principal component analysis segregated study sites into four groups demarcating source relationships. Our study, that forms the first report on atmosphere–land–water transfer of organic carbon in Ganga River, suggests that future climate models should include region-specific time series data on changing state of atmosphere– land–water connectivity and associated shift in carbon balance of major rivers for more accurately predicting the climate change drivers.