Temporal Variability (Diurnal, Seasonal and Decadal Scale) of CO2 Dynamics and Air-Water CO2 Flux in a Tropical Macro-Tidal Estuary, East Coast of India
Abstract
The Hugli Estuary is the first deltaic branch of River Ganges and a coastal plain estuary situated in the eastern coast of India. There are very few works on carbonate dynamics and air-water CO2 flux in this estuary. The fugacity of CO2 [fCO2 (water)] and air-water CO2 flux were estimated along with other biogeochemical parameters in the four stations of Hugli Estuary from the 80 km upstream to the river confluence. The CO2 flux were estimated using `bulk formula' method. All the stations of the Hugli Estuary were highly supersaturated with CO2 [annual mean fCO2 (water) 2200 µatm] with a mean annual salinity of 7.1 and a mean annual pH of 7.86. The semi-diurnal tidal cycle is found to play a crucial role in regulating the diurnal as well as diel variability of fCO2 (water). High fCO2 (water) values were observed during ebb tide and vice versa during flood tide. Even when the low tide conditions coincided with the photosynthetic maxima during the day, the effect of ebb tide overruled the photosynthetic CO2 uptake leading to increases in fCO2 (water) due to freshwater derived organic and inorganic carbon load. The efflux of CO2 showed a maximum during monsoon season (June to September) followed by Pre-monsoon (February to May) and Post-monsoon (October to January) seasons. The decreased efflux during post-monsoon season is assumed to be owing to higher photosynthetic rate and primary productivity. The efflux of CO2 decreased along the directions from the upstream to the river confluence. The estimated annual mean CO2 emission from the Hugli Estuary was 29.3 mol C m-2 yr -1 during the study period. Comparing with a previous study of decades ago, it is concluded that the CO2 efflux in the Hugli Estuary increased more than two fold during the last decade, possibly due to enhanced sewage load, land-use change and climate change.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.B31C0493A
- Keywords:
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- 0478 Pollution: urban;
- regional and global;
- BIOGEOSCIENCESDE: 0481 Restoration;
- BIOGEOSCIENCESDE: 0493 Urban systems;
- BIOGEOSCIENCESDE: 0496 Water quality;
- BIOGEOSCIENCES