Biosphere-atmosphere exchange of NOx at the Sundarban mangrove forest along the northeast coast of the Bay of Bengal, India, showed uptake rates of -0.84 to -1.63 ng N m-2 s-1 during the day and both uptake and emission rates of -0.36 to 5.19 ng N m-2 s -1 during the night from September to February. However, during the period from March to August, NOx emission ranged between 0.34 and 2.13 ng N m-2 s-1 and 0.88 and 3.26 ng N m-2 s-1 in daytime and nighttime, respectively. During the postmonsoon period, NOx uptake could be attributed to mangrove stomatal activity during the day. Mangroves absorbed nitrogen from both the soil and the atmosphere. Seasonal and diurnal variability of NOx and O3 is partly due to plant growth in the postmonsoon period. In addition to the NOx-O3 photochemical cycle, stomatal uptake of NO x could also be an important process for keeping a low-ozone state at the land-ocean boundary of the northeast coast of the Bay of Bengal. Copyright 2009 by the American Geophysical Union.

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University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Biosphere-atmosphere exchange of NOx in the tropical mangrove forest

Journal of Geophysical Research: Biogeosciences

The present study focused on understanding differences in the post-monsoon carbon (C) biogeochemistry of two adjacent estuaries undergoing different levels of anthropogenic stresses by investigating anthropogenically influenced Hooghly estuary and mangrove-dominated estuaries of the Sundarbans in the north-eastern India. The salinity of well-oxygenated estuaries of the Sundarbans (DO: 91 %- 104 %) varied over a narrow range (12.74-16.69) relative to the Hooghly estuary (0.04-10.37). A mixing model suggested a combination of processes including freshwater intrusion, carbonate precipitation and carbonate dissolution to be a major factor controlling dissolved inorganic C (DIC) dynamics in the freshwater regime of the Hooghly, whereas phytoplankton productivity and CO 2 outgassing dominated in the mixing regime. In the Sundarbans, the removal of DIC (via CO 2 outgassing, phytoplankton uptake and export to the adjoining continental shelf region) dominated its addition through mineralization of mangrove-derived organic C. The concentration of dissolved organic C (DOC) in the Hooghly was ~ 40% higher than in the Sundarbans, which was largely due to the cumulative effect of anthropogenic inputs, DOC-POC interconversion and groundwater contribution rather than freshwater-mediated input. The measured δ 13 CPOC in the Hooghly suggested particulate organic matter contributions from different sources (freshwater runoff, terrestrial C 3 plants and anthropogenic discharge), whereas the contribution from C 3 plants was dominant at the Sundarbans. The significant departure of δ 13 CPOC from typical mangrove δ 13 C in the mangrove-dominated Sundarbans suggested significant particulate organic C (POC) modification due to degradation by respiration. The average pCO 2 in the Hooghly was higher by ~ 1291 μatm compared to the Sundarbans with surface runoff and organic matter degradation by respiration as dominant factors controlling pCO 2 in the Hooghly and Sundarbans, respectively. The entire Hooghly- Sundarbans system acted as a source of CO 2 to the regional atmosphere with ~ 17 times higher emission from the Hooghly compared to the Sundarbans. Taken together, the cycling of C in estuaries with different levels of anthropogenic influences is evidently different, with significantly higher CO 2 emission from the anthropogenically influenced estuary than the mangrove-dominated ones. © Author(s) 2019.

Biogeosciences

The post-monsoon carbon biogeochemistry of the Hooghly-Sundarbans estuarine system under different levels of anthropogenic impacts

The dynamics of methane (CH4) flux in relation to populations of methanogenic and methanotrophic bacteria was studied under the different biophysical conditions of the Indian Sundarban mangrove ecosystem. Soil depth profile analysis (up to 60cm) in the lower littoral zone (LLZ) revealed that a methanogenic population of 6.45 +/- 0.19 x 10(4) cells/g dry weight (dry wt) of soil accounted for a CH4 production rate of 6.23 +/- 3.53 x 10(3) mu molm(-2)day(-1), whereas in the surface soil, a methanogenic population of 3.34 +/- 0.37 x 10(4) cells/g dry wt of soil accounted for a CH4 production rate of 31.6 +/- 0.57 mu molm(-2)day(-1). The CH4 oxidation rate at 60cm depth in the LLZ was 24.42 +/- 1.28 mu molm(-2)day(-1), with an average methanotrophic population of 1.33 +/- 0.43 x 10(4) cells/g dry wt of soil, whereas in the surface soil, the oxidation rate and average population were 3.38 +/- 1.43 x 10(3) mu molm(-2)day(-1) and 12.80 +/- 2.54 x 10(4) cells/g dry wt of soil, respectively. A similar soil profile in terms of CH4 dynamics and the populations of methanogenic and methanotrophic bacteria was found in the mid-littoral and upper littoral zones of the studied area. The results demonstrate that most of the produced CH4 (approximately 60%) was oxidized by methanotrophic bacteria present in the soil, thus revealing their principal role in regulating the CH4 flux from this unique ecosystem.

Marine Ecology

Methane flux dynamics in relation to methanogenic and methanotrophic populations in the soil of Indian Sundarban mangroves

The dynamics of methane (CH4) flux in relation to populations of methanogenic and methanotrophic bacteria was studied under the different biophysical conditions of the Indian Sundarban mangrove ecosystem. Soil depth profile analysis (up to 60 cm) in the lower littoral zone (LLZ) revealed that a methanogenic population of 6.45 ± 0.19 × 104 cells/g dry weight (dry wt) of soil accounted for a CH4 production rate of 6.23 ± 3.53 × 103 µmol m−2 day−1, whereas in the surface soil, a methanogenic population of 3.34 ± 0.37 × 104cells/g dry wt of soil accounted for a CH4production rate of 31.6 ± 0.57 µmol m−2 day−1. The CH4oxidation rate at 60 cm depth in the LLZ was 24.42 ± 1.28 µmol m−2 day−1, with an average methanotrophic population of 1.33 ± 0.43 × 104cells/g dry wt of soil, whereas in the surface soil, the oxidation rate and average population were 3.38 ± 1.43 × 103µmol m−2 day−1and 12.80 ± 2.54 × 104cells/g dry wt of soil, respectively. A similar soil profile in terms of CH4dynamics and the populations of methanogenic and methanotrophic bacteria was found in the mid-littoral and upper littoral zones of the studied area. The results demonstrate that most of the produced CH4(approximately 60%) was oxidized by methanotrophic bacteria present in the soil, thus revealing their principal role in regulating the CH4flux from this unique ecosystem. © 2018 Blackwell Verlag GmbH

Mangroves are known as natural carbon sinks, taking CO2 out of the atmosphere and store it in their biomass for many years. This study aimed to investigate the capacity of world's largest mangrove, the Sundarbans (Indian part) to sequester anthropogenic CO2 emitted from the proximate coal-based thermal power plant in Kolaghat (∼100 km away from mangrove site). Study also includes Kolkata, one of the largest metropolises of India (∼150 km away from mangrove site) for comparing micrometeorological parameters, biosphere-atmosphere CO2 exchange fluxes and atmospheric pollutants between three distinct environments: mangrove-power plant-metropolis. Hourly sampling of atmospheric CO2 in all three sites (late December 2011 and early January 2012) revealed that CO2 concentrations and emission fluxes were maximum around the power plant (360–621 ppmv, 5.6–56.7 mg m−2s−1 respectively) followed by the metropolis (383–459 ppmv, 3.8–20.4 mg m−2s−1 respectively) and mangroves (277–408 ppmv, −8.9–11.4 mg m−2s−1, respectively). Monthly coal consumption rates (41–57, in 104 ton month−1) were converted to CO2 suggesting that 2.83 Tg C was added to the atmosphere in 2011 for the generation of 7469732 MW energy from the power plant. Indian Sundarbans (4264 km2) sequestered total of 2.79 Tg C which was 0.64% of the annual fossil fuel emission from India in the same time period. Based on these data from 2010 to 2011, it is calculated that about 4328 km2 mangrove forest coverage is needed to sequester all CO2 emitted from the Kolaghat power plant. © 2017 Elsevier Ltd

Atmospheric Environment

Carbon sequestration by mangrove forest: One approach for managing carbon dioxide emission from coal-based power plant

Atmospheric fluxes of CH<inf>4</inf> across different boundaries and its photo-oxidation were measured in the Sundarbans mangrove forest during June 2010-December 2011. The annual mean CH<inf>4</inf> emission rate from intertidal sediment and adjacent estuarine surfaces were 7.06 and 0.14mgm-2d-1, respectively. Together these sources contribute 10.89Gg of CH<inf>4</inf> annually to the atmosphere, of which 99.17% was from sediment. The atmospheric CH<inf>4</inf> mixing ratio varied between 1.693 and 2.251ppmv, having an average of 2.004ppmv. CH<inf>4</inf> exchange flux from this mangrove biosphere to the atmosphere was 0.086mgm-2d-1, contributing 0.30Gg of CH<inf>4</inf> annually. The annual average rate of CH<inf>4</inf> photo-oxidation in the forest atmosphere was 3.25×10-9mgcm-3d-1 with maximum oxidation occurring during the monsoon period and minimum oxidation occurring during the post-monsoon period. Total CH<inf>4</inf> photo-oxidation within the atmospheric boundary layer of the Sundarbans was 9.26Gg annually, which acts as sink for 85.03% of the emitted CH<inf>4</inf>. The HCHO and O<inf>3</inf> mixing ratios in the forest atmosphere ranged between 2.14±0.06-4.08±1.61ppbv and 14.66±1.88-37.90±0.91ppbv, respectively, having maximal pre-monsoon and minimal monsoon periods. The CH<inf>4</inf> photo-oxidation mediated productions of HCHO and O<inf>3</inf> within the atmospheric boundary layer were 17.5 and 139Ggyr-1, respectively. A 'sources and sinks dependent' mathematical model for atmospheric CH<inf>4</inf> proposed in this study can explain the seasonal variability of CH<inf>4</inf> and showed significant correlation with the observed values of this regional atmosphere. © 2015 Elsevier B.V.

Agricultural and Forest Meteorology

Atmospheric fluxes and photo-oxidation of methane in the mangrove environment of the Sundarbans, NE coast of India; A case study from Lothian Island

Mixing ratios of 15 carbonyls and BTEX (benzene, toluene, ethyl benzene, xylenes) were measured for the first time in ambient air of Kolkata, India at three sites from March to June 2006 and their photochemical reactivity was evaluated. Day and nighttime samples were collected on weekly basis. Formaldehyde was the most abundant carbonyl (mean concentration ranging between 14.07 μg m-3 to 26.12 μg m-3 over the three sites) followed by acetaldehyde (7.60-18.67 μg m-3) and acetone (4.43-10.34 μg m-3). Among the high molecular weight aldehydes, nonanal showed the highest concentration. Among the mono-aromatic VOCs, mean concentration of toluene (27.65-103.31 μg m-3) was maximum, closely followed by benzene (24.97-79.18 μg m-3). Mean formaldehyde to acetaldehyde (1.4) and acetaldehyde to propanal ratios (5.0) were typical of urban air. Based on their photochemical reactivity towards OH· radical, the concentrations of the VOCs were scaled to formaldehyde equivalent, which showed that the high molecular weight carbonyls and xylenes contribute significantly to the total OH-reactive mass of the VOCs. Due to the toxic effect of the VOCs studied, an assessment for both cancer risk and non-cancer hazard due to exposure to the population were calculated. Integrated life time cancer risk (ILTCR) due to four carcinogens (benzene, ethyl benzene, formaldehyde and acetaldehyde) and non-cancer hazard index for the VOCs at their prevailing level were estimated to be 1.42E-04 and 5.6 respectively. © Springer Science+Business Media B.V. 2008.

Environmental Monitoring and Assessment

Mixing ratios of carbonyls and BTEX in ambient air of Kolkata, India and their associated health risk

Amount of radiant energy (short wave) available to drive biosphere-atmosphere exchange of CO2, H2O, CH4 and for transfer into other energy forms were determined for a tropical mangrove forest at the land ocean boundary of north-east (NE) coast of Bay of Bengal from January to December 2006. The mean annual incoming short wave radiation (435±32.8 W m-2) was partitioned into 29% sensible heat, 35% latent heat, 4% ground heat, 7% physical storage energy and 10% photosynthetic storage energy. The mean budget closing energy flux (68.96±24.6 W m-2) or, budget error was 15.8% of incoming short wave radiation. In Varimax factor analysis, budget closing energy flux showed high loading in association with leaf chlorophyll of different mangrove species, indicating its major role for reflectivity of the surface for short wave. There was significant seasonality in CO2 exchange with net primary productivity of 14.1 μmol m-2 s-1. The mean methane emission was found higher (7.29 μg m-2 s-1) during the daytime than that of night time (1.37 μg m-2 s-1) with maximum methane emission rates of 36.1 and 21.1 μg m-2 s-1 in December and January, respectively. Stepwise multiple regression analysis between storage energy [ΔHs(P)] and fluxes of CO2, CH4, H (sensible heat), HL (latent heat of evaporation), ΔR (budget closer energy) showed that the combined explained variability for CO2 flux, evapotranspiration and budget closer energy (39%) was less than that of CH4 and sensible heat flux (46%). The extent of warming effect by CH4 and sensible heat flux was predominant over the resultant cooling effect due to the processes such as photosynthesis, evapotranspiration and albedo. The mangrove forest with two trademarks of low albedo and high surface roughness was poorly coupled to the environment. © 2008 Elsevier Ltd. All rights reserved.

Energy dynamics and its implication to biosphere-atmosphere exchange of CO2, H2O and CH4 in a tropical mangrove forest canopy

A comprehensive size-segregated characterization of the chemical properties (water-soluble inorganic fraction) of the sea-salt aerosol originated from the surf zone at the land-ocean boundary of Sundarban Mangrove forest, NE coast of Bay of Bengal, and an analysis of the relevant meteorological parameters revealed how the combined effect of anthropogenic gases and aerosol advected to the virgin mangrove forest and micrometeorological conditions could change the marine character of the aerosol before the onset of SW monsoon. The average aerosol mass concentration was 99.94 ± 41.9 μg m-3 with production rate of 0.19 μg m-2 s-1 (durinq January) to 4.29 μg m-2 s-1 (during April) and dry deposition rate of 0.019 μg m-2 s-1 (during January) to 13.21 μg m-2 s-1 (during June). 72.35% of the total aerosol mass was leachable by water, and relatively large concentrations of phosphorus were observed. More chloride depletion from the coarse (2.0 < d<inf>p</inf> < 10 μm) and nucleation (d<inf>p</inf> < 0.4 μm) modes compared to the accumulation mode (0.4 < d<inf>p</inf> < 2.0 μm) was observed in winter (Cl/Na = 0.6023 ± 0.1798), and a reverse trend was observed in summer (Cl/Na = 0.644 ± 0.262). A significant positive correlation was obtained for chloride loss with non-sea-sulphate and nitrate for particles > 2.0 μm. Distributions of Na+, K+, Ca2+, Mg2+, NH<inf>4</inf>+, Cl-, NO<inf>2</inf>-, NO<inf>3</inf>-, SO<inf>4</inf>2-, and PO<inf>4</inf>3- in different size modes were considered to collate their source apportionment. The proximity of Calcutta and Haldia metropolis to the mangrove forest could influence the forest air quality and depositional processes. Copyright 2006 by the American Geophysical Union.

Journal	Journal of Geophysical Research: Biogeosciences
Publisher	Blackwell Publishing Ltd
ISSN	0148-0227
Open Access	No