Concentration, sources and wet deposition of dissolved nitrogen and organic carbon in the Northern Indo-Gangetic Plain during monsoon

Abstract Very limited information on the magnitude and environmental impacts of both inorganic as well as organic forms of Nitrogen (N) wet deposition is available in India. Molar concentrations of inorganic (NH4+ and NO3−) and organic N in rainwater were monitored at three different land-use sites in Indo-Gangetic Plain (IGP) during the monsoon period (June-September) of 2017. It has been observed that dissolved organic N (DON) contributed significantly to the total dissolved N (TDN) ranging from 5–60%. Dissolved inorganic N (DIN = NH4+ + NO3−) concentration was recorded as high as 221.0 µmol L− 1 at urban site to as low as 65.9 µmol L− 1 at the rural site. A similar pattern was also observed for DON. NH4+ contribution to TDN had the order: urban megacity (65%) > urban (70%) > rural (75%). Agriculture and animal husbandry are the primary sources of NH4+ emissions in the rural site. However, NO3− has shown a contrasting trend at these sites (25%, 15% and 8%, respectively). Wet deposition fluxes of atmospheric TDN was observed to be higher at urban sites. This can attributed to a variety of local sources such as vehicular emission, microbial emissions, biomass burning, human excreta due to higher population density, and transportation from surrounding areas, as observed from concentration weighted trajectories (CWT) model and cluster analysis. Upwind region of IGP has experienced major influence of air mass transported from agriculturally rich northwest part of India. However, both the downwind sites have experienced by-and-large the influence of south-westerly air-masses originated over the Arabian Sea. Study has found that the DON contributes significantly to TDN and need to be included for budget assessment in South Asia.

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Variation in carbonaceous and ionic species at a rural receptor location in the eastern Indo-Gangetic Plain

10.5194/egusphere-egu21-7205 ◽

2021 ◽

Author(s):

Bijay Sharma ◽

Anurag J. Polana ◽

Jingying Mao ◽

Shiguo Jia ◽

Sayantan Sarkar

Keyword(s):

Organic Carbon ◽

Forest Fires ◽

Ionic Species ◽

Water Soluble ◽

Photochemical Oxidation ◽

Carbonaceous Aerosol ◽

Charge Ratio ◽

Gangetic Plain ◽

Post Monsoon ◽

Indo Gangetic Plain

The Indo-Gangetic Plain (IGP) is one of the world&#8217;s most populated river basins housing more than 700 million people. Apart from being a major source region of aerosols, the IGP is affected by transported aerosols from the Thar Desert, forest-fires and open burning of crop waste from central India. Studies have been carried out to understand the aerosol chemical composition and optical properties in source regions of IGP but knowledge is severely lacking for receptor locations viz. eastern IGP (eIGP). To address this, the present study reports the seasonal variability of carbonaceous and ionic species in ambient PM2.5 from a rural receptor location (Mohanpur, West Bengal) along with insights on aerosol acidity, its neutralization and potential source regimes. A total of 88 PM2.5 samples collected during the summer, post-monsoon and winter seasons of 2018 were analyzed for SO42-, NO3-, Cl-, Na+, NH4+, K+, Ca2+, Mg2+, F-,PO43-, water-soluble organic carbon (WSOC), organic carbon (OC) and elemental carbon (EC) fractions. Sulfate, nitrate and ammonium (SNA) were the dominating ionic species throughout the seasons (67-86% out of the total ionic species measured). Significant positive Cl- depletion in summer (49&#177;20%) pointed towards influx of marine air while negative depletion in post-monsoon and winter suggested a biomass burning (BB) source, which was further supported by concentration-weighted trajectory analysis. Strong acidity was found to be highest during post-monsoon (141&#177;76 nmol m-3), followed by winter (117&#177;36 nmol m-3) and summer (40&#177;14 nmol m-3) with significant differences between summer and the other seasons. Neutralization factor (Nf) and equivalent charge ratio of cation to anion (RC/A) revealed that summertime aerosols were neutral in nature while those of post-monsoon and winter were comparatively acidic with NH4+ being the major neutralizing agent throughout the seasons. Correlations between WSOC and OC fractions (OC1, OC2, OC3 and OC4) suggested secondary formation of summertime WSOC (WSOC vs OC3: r=0.48, p<0.05) via photochemical oxidation of volatile organic carbons (VOCs) while that of post-monsoon (WSOC vs OC1, OC2, OC3: r=0.45-0.62, p<0.05) and winter (WSOC vs OC1, OC2, OC3: r=0.58-0.68, p<0.05), both primary and secondary pathways seem important. To elucidate the role of BB, we looked into the two components of EC i.e., char-EC (EC1-PC) and soot-EC (EC2+EC3). The percent contribution of char-EC to EC was 65&#177;17%, 90&#177;10% and 98&#177;1% during summer, post-monsoon and winter, respectively. Along with this, char-EC/soot-EC ratios of 2.3&#177;1.8, 17.6&#177;16.4 and 50.3&#177;18.6 during summer, post-monsoon and winter, respectively, and significant correlations of the same with the BB-tracer K+ (post-monsoon: r=0.78, p<0.001; winter: r=0.64, p<0.01) indicated the importance of BB emissions in constraining carbonaceous aerosol profiles during post-monsoon and winter.

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Increasing Soil Organic Carbon Through Crop Diversification in Cereal–Cereal Rotations of Indo-Gangetic Plain

Proceedings of the National Academy of Sciences India Section B Biological Sciences ◽

10.1007/s40011-017-0953-x ◽

2017 ◽

Vol 89 (2) ◽

pp. 429-440 ◽

Cited By ~ 5

Author(s):

P. K. Ghosh ◽

K. K. Hazra ◽

M. S. Venkatesh ◽

C. P. Nath ◽

Jagdish Singh ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Crop Diversification ◽

Gangetic Plain ◽

Indo Gangetic Plain

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Optical and chemical properties of wintertime light-absorbing aerosols in the eastern Indo-Gangetic Plain, India

10.5194/egusphere-egu2020-655 ◽

2020 ◽

Author(s):

Supriya Dey ◽

Archita Rana ◽

Prashant Rawat ◽

Sayantan Sarkar

Keyword(s):

Organic Carbon ◽

Light Absorption ◽

Mass Concentration ◽

Chemical Properties ◽

Water Soluble ◽

Chemical Extraction ◽

Aerosol Formation ◽

Gangetic Plain ◽

Indo Gangetic Plain ◽

And Chemical Properties

Light-absorbing carbonaceous aerosols such as black and brown carbon (BC and BrC) and humic-like substances (HULIS) have pronounced effects on the earth&#8217;s radiative balance and tropospheric photochemistry. In India, large heterogeneities exist for BC and organic carbon (OC) emission inventories, which necessitates regionally-representative ground-based measurements. Such measurements are spatially scattered for BC, rare for BrC and non-existent for HULIS. This severely limits a robust understanding of the optical and chemical properties of these aerosols, and consequently, their climate effects. To address this issue, the present study reports optical and chemical properties of wintertime (December 2018-February 2019) BC, BrC and HULIS at a rural receptor site in the highly polluted eastern Indo-Gangetic Plain (IGP), India. A 7 wavelength aethalometer was deployed to measure time-resolved BC mass concentration, and absorption coefficients (babs) and Angstrom exponent (AE) of BrC. Separation of aqueous and organic BrC (BrCaq and BrCorg) and HULIS fractions via a multi-step chemical extraction procedure followed by optical measurements (UV-Vis, fluorescence and FT-IR), and supplementary measurements of OC, water-soluble organic carbon (WSOC) and ionic species led to better insights into the potential chromophore composition and their relative importance in constraining aerosol optical properties.The daily averaged BC mass concentration was 15.4&#177;9.5 &#956;g m-3 during winter, where the biomass burning (BB) contribution was 25&#177;5%. The diurnal profile of BCBB and BrC light absorption coefficient (babs_BrC) showed a prominent morning peak (0700-0800 H) characterized by mixed fossil fuel and biofuel emission and a gradual increase towards night due to enhanced primary BB emission from cooking activities and lowering of the mixing depth. The regionally transported BB plume from northwestern IGP contributed substantial BC and BrC to this receptor location in the eastern end of the corridor, which was supported by concentration-weighted air mass trajectories (CWTs).The BrCorg light absorption at 365 nm (babs_BrC_org) was almost 2 times compared to that of BrCaq (babs_BrC_aq) (36&#177;7.1 vs 18.3&#177;4.3 Mm-1), which suggested a dominance of non-polar polyconjugated BrC chromophores. This was also supported by the increasing trend of water-insoluble BrC from 49&#177;10% at 365 nm to 64&#177;21% at 550 nm, with averaged contributions of 49&#177;8% at 300-400 nm and 67&#177;9% at 400-550 nm, respectively. A strong correlation between WSOC and NO3- (r=0.78, p<0.01) and WSOC and NH4+ (r=0.63, p<0.01) indicated the possibility of nighttime secondary organic aerosol formation. A prominent fluorescence peak at ~409 nm for BrCaq confirmed the presence of HULIS, and babs_BrC_aq was dominated by the low-polarity HULIS-n fraction. AE of individual HULIS fractions increased by 7-36% towards the more polar HULIS-a and highly-polar water-soluble organic matter (HPWSOM) compared to the less polar HULIS-n for the 300-700 nm range. Distinct FTIR peaks at 3400 cm-1, 1710 cm-1 and 1643 cm-1 suggested abundance of C-H, C=O and C=C functional groups, respectively, in the BrC chromophores. Overall, it appeared that the regionally transported BB plume significantly enriches BrC and HULIS in the eastern part of the IGP corridor. &#160;&#160;

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