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Nitrogen accumulation and attenuation in the Ganges-Brahmaputra-Meghna river system: An evaluation with multiple
Shan Jiang1, Md Jaker Hossain1, Sheikh Aftab Uddin2
1State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China.
Abstract:
We examined dissolved inorganic nitrogen (DIN) accumulation and attenuation in the lower stream and estuary of the Ganges-Brahmaputra-Meghna River system. In the lower stream of Ganges, Meghna and Brahmaputra rivers, nitrate (NO3-) was the dominant component in the DIN pool apart from the site near an industrial center. Concentrations of NO3- displayed minor differences between surface and bottom water, accounting for >90 % of the riverine DIN pool. Sources of NO3- were likely to be municipal wastewater and fertilizer based on signals of 15N-NO3- and 18O-NO3-. In the Meghna River, ammonium concentration in river water increased due to sewage discharge from local industrial centers. In the estuary, likely due to the high-abundance nitrifiers, nitrification rates overwhelmed removal rates and led to NO3- accumulation. Towards coastal ocean, DIN concentrations decreased due to seawater dilution and biological assimilation, indicating a tight linkage between the riverine input and ecological stability in the receiving water.
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