Nitrous Oxide Production and its Linkage with the Environmental Parameters in The Indian Sundarbans Estuaries

Nitrous oxide (N₂O) is a climate-relevant trace gas and its emissions from coastal areas are a major contribution to the global atmospheric N₂O budget. However, coastal N₂O emissions are associated with a high degree of uncertainty because of the temporal and spatial variability of N₂O production and consumption pathways. Here we investigated N₂O production in the Saptamukhi, Thakuran, and Matla estuaries of the Indian Sundarbans (northern Bay of Bengal). Our study suggests nitrification may possibly be the major N₂O production pathway in the estuarine waters. Our observations also indicated a pronounced seasonal trend, with peak DIN and N₂O levels occurring during the monsoon season and the lowest concentrations post-monsoon. N₂O production rates similarly increased from the pre-monsoon to monsoon periods, heavily influenced by the environmental factors of the system. The N₂O emissions to the atmosphere were not balanced by sedimentary release and nitrification in the water, but were most probably fed by advection of N₂O-enriched waters of riverine origin. This phenomenon may have contributed to the high N₂O concentrations in three estuaries. Further detailed studies on nitrification in these estuaries may prove useful to develop further research on N₂O sources and emission from the Indian Sundarbans.