Measurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India, and Comilla, Bangladesh

<p>Emissions of greenhouse gases (GHGs) from the Indian subcontinent have increased during the last 20 years along with rapid economic growth; however, there remains a paucity of GHG measurements for policy-relevant research. In northern India and Bangladesh, agricultural activities are consid...

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Autores principales:	S. Nomura, M. Naja, M. K. Ahmed, H. Mukai, Y. Terao, T. Machida, M. Sasakawa, P. K. Patra
Formato:	article
Lenguaje:	EN
Publicado:	Copernicus Publications 2021
Materias:	Physics QC1-999 Chemistry QD1-999
Acceso en línea:	https://doaj.org/article/51d2b2de7c9c419cb7f12e31e97bc8cd
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record_format	dspace
institution	DOAJ
collection	DOAJ
language	EN
topic	Physics QC1-999 Chemistry QD1-999
spellingShingle	Physics QC1-999 Chemistry QD1-999 S. Nomura M. Naja M. K. Ahmed H. Mukai Y. Terao T. Machida M. Sasakawa P. K. Patra Measurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India, and Comilla, Bangladesh
description	<p>Emissions of greenhouse gases (GHGs) from the Indian subcontinent have increased during the last 20 years along with rapid economic growth; however, there remains a paucity of GHG measurements for policy-relevant research. In northern India and Bangladesh, agricultural activities are considered to play an important role in GHG concentrations in the atmosphere. We performed weekly air sampling at Nainital (NTL) in northern India and Comilla (CLA) in Bangladesh from 2006 and 2012, respectively. Air samples were analyzed for dry-air gas mole fractions of <span class="inline-formula">CO<sub>2</sub></span>, <span class="inline-formula">CH<sub>4</sub></span>, <span class="inline-formula">CO</span>, <span class="inline-formula">H<sub>2</sub></span>, N<span class="inline-formula"><sub>2</sub></span>O, and SF<span class="inline-formula"><sub>6</sub></span> and carbon and oxygen isotopic ratios of CO<span class="inline-formula"><sub>2</sub></span> (<span class="inline-formula"><i>δ</i><sup>13</sup></span>C-CO<span class="inline-formula"><sub>2</sub></span> and <span class="inline-formula"><i>δ</i><sup>18</sup></span>O-CO<span class="inline-formula"><sub>2</sub></span>). Regional characteristics of these components over the Indo-Gangetic Plain are discussed compared to data from other Indian sites and Mauna Loa, Hawaii (MLO), which is representative of marine background air.</p> <p>We found that the CO<span class="inline-formula"><sub>2</sub></span> mole fraction at CLA had two seasonal minima in February–March and September, corresponding to crop cultivation activities that depend on regional climatic conditions. Although NTL had only one clear minimum in September, the carbon isotopic signature suggested that photosynthetic CO<span class="inline-formula"><sub>2</sub></span> absorption by crops cultivated in each season contributes differently to lower CO<span class="inline-formula"><sub>2</sub></span> mole fractions at both sites. The CH<span class="inline-formula"><sub>4</sub></span> mole fraction of NTL and CLA in August–October showed high values (i.e., sometimes over 4000 ppb at CLA), mainly due to the influence of CH<span class="inline-formula"><sub>4</sub></span> emissions from the paddy fields. High CH<span class="inline-formula"><sub>4</sub></span> mole fractions sustained over months at CLA were a characteristic feature on the Indo-Gangetic Plain, which were affected by both the local emission and air mass transport. The CO mole fractions at NTL were also high and showed peaks in May and October, while CLA had much higher peaks in October–March due to the influence of human activities such as emissions from biomass burning and brick production. The N<span class="inline-formula"><sub>2</sub></span>O mole fractions at NTL and CLA increased in June–August and November–February, which coincided with the application of nitrogen fertilizer and the burning of biomass such as the harvest residues and dung for domestic cooking. Based on H<span class="inline-formula"><sub>2</sub></span> seasonal variation at both sites, it appeared that the emissions in this region were related to biomass burning in addition to production from the reaction of OH and CH<span class="inline-formula"><sub>4</sub></span>. The SF<span class="inline-formula"><sub>6</sub></span> mole fraction was similar to that at MLO, suggesting that there were few anthropogenic SF<span class="inline-formula"><sub>6</sub></span> emission sources in the district.</p> <p>The variability of the CO<span class="inline-formula"><sub>2</sub></span> growth rate at NTL was different from the variability in the CO<span class="inline-formula"><sub>2</sub></span> growth rate at MLO, which is more closely linked to the El Niño–Southern Oscillation (ENSO). In addition, the growth rates of the CH<span class="inline-formula"><sub>4</sub></span> and SF<span class="inline-formula"><sub>6</sub></span> mole fractions at NTL showed an anticorrelation with those at MLO, indicating that the frequency of southerly air masses strongly influenced these mole fractions. These findings showed that rather large regional<span id="page16428"/> climatic conditions considerably controlled interannual variations in GHGs, <span class="inline-formula"><i>δ</i><sup>13</sup></span>C-CO<span class="inline-formula"><sub>2</sub></span>, and <span class="inline-formula"><i>δ</i><sup>18</sup></span>O-CO<span class="inline-formula"><sub>2</sub></span> through changes in precipitation and air mass.</p>
format	article
author	S. Nomura M. Naja M. K. Ahmed H. Mukai Y. Terao T. Machida M. Sasakawa P. K. Patra
author_facet	S. Nomura M. Naja M. K. Ahmed H. Mukai Y. Terao T. Machida M. Sasakawa P. K. Patra
author_sort	S. Nomura
title	Measurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India, and Comilla, Bangladesh
title_short	Measurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India, and Comilla, Bangladesh
title_full	Measurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India, and Comilla, Bangladesh
title_fullStr	Measurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India, and Comilla, Bangladesh
title_full_unstemmed	Measurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India, and Comilla, Bangladesh
title_sort	measurement report: regional characteristics of seasonal and long-term variations in greenhouse gases at nainital, india, and comilla, bangladesh
publisher	Copernicus Publications
publishDate	2021
url	https://doaj.org/article/51d2b2de7c9c419cb7f12e31e97bc8cd
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spelling	oai:doaj.org-article:51d2b2de7c9c419cb7f12e31e97bc8cd2021-11-10T09:27:14ZMeasurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India, and Comilla, Bangladesh10.5194/acp-21-16427-20211680-73161680-7324https://doaj.org/article/51d2b2de7c9c419cb7f12e31e97bc8cd2021-11-01T00:00:00Zhttps://acp.copernicus.org/articles/21/16427/2021/acp-21-16427-2021.pdfhttps://doaj.org/toc/1680-7316https://doaj.org/toc/1680-7324<p>Emissions of greenhouse gases (GHGs) from the Indian subcontinent have increased during the last 20 years along with rapid economic growth; however, there remains a paucity of GHG measurements for policy-relevant research. In northern India and Bangladesh, agricultural activities are considered to play an important role in GHG concentrations in the atmosphere. We performed weekly air sampling at Nainital (NTL) in northern India and Comilla (CLA) in Bangladesh from 2006 and 2012, respectively. Air samples were analyzed for dry-air gas mole fractions of <span class="inline-formula">CO<sub>2</sub></span>, <span class="inline-formula">CH<sub>4</sub></span>, <span class="inline-formula">CO</span>, <span class="inline-formula">H<sub>2</sub></span>, N<span class="inline-formula"><sub>2</sub></span>O, and SF<span class="inline-formula"><sub>6</sub></span> and carbon and oxygen isotopic ratios of CO<span class="inline-formula"><sub>2</sub></span> (<span class="inline-formula"><i>δ</i><sup>13</sup></span>C-CO<span class="inline-formula"><sub>2</sub></span> and <span class="inline-formula"><i>δ</i><sup>18</sup></span>O-CO<span class="inline-formula"><sub>2</sub></span>). Regional characteristics of these components over the Indo-Gangetic Plain are discussed compared to data from other Indian sites and Mauna Loa, Hawaii (MLO), which is representative of marine background air.</p> <p>We found that the CO<span class="inline-formula"><sub>2</sub></span> mole fraction at CLA had two seasonal minima in February–March and September, corresponding to crop cultivation activities that depend on regional climatic conditions. Although NTL had only one clear minimum in September, the carbon isotopic signature suggested that photosynthetic CO<span class="inline-formula"><sub>2</sub></span> absorption by crops cultivated in each season contributes differently to lower CO<span class="inline-formula"><sub>2</sub></span> mole fractions at both sites. The CH<span class="inline-formula"><sub>4</sub></span> mole fraction of NTL and CLA in August–October showed high values (i.e., sometimes over 4000 ppb at CLA), mainly due to the influence of CH<span class="inline-formula"><sub>4</sub></span> emissions from the paddy fields. High CH<span class="inline-formula"><sub>4</sub></span> mole fractions sustained over months at CLA were a characteristic feature on the Indo-Gangetic Plain, which were affected by both the local emission and air mass transport. The CO mole fractions at NTL were also high and showed peaks in May and October, while CLA had much higher peaks in October–March due to the influence of human activities such as emissions from biomass burning and brick production. The N<span class="inline-formula"><sub>2</sub></span>O mole fractions at NTL and CLA increased in June–August and November–February, which coincided with the application of nitrogen fertilizer and the burning of biomass such as the harvest residues and dung for domestic cooking. Based on H<span class="inline-formula"><sub>2</sub></span> seasonal variation at both sites, it appeared that the emissions in this region were related to biomass burning in addition to production from the reaction of OH and CH<span class="inline-formula"><sub>4</sub></span>. The SF<span class="inline-formula"><sub>6</sub></span> mole fraction was similar to that at MLO, suggesting that there were few anthropogenic SF<span class="inline-formula"><sub>6</sub></span> emission sources in the district.</p> <p>The variability of the CO<span class="inline-formula"><sub>2</sub></span> growth rate at NTL was different from the variability in the CO<span class="inline-formula"><sub>2</sub></span> growth rate at MLO, which is more closely linked to the El Niño–Southern Oscillation (ENSO). In addition, the growth rates of the CH<span class="inline-formula"><sub>4</sub></span> and SF<span class="inline-formula"><sub>6</sub></span> mole fractions at NTL showed an anticorrelation with those at MLO, indicating that the frequency of southerly air masses strongly influenced these mole fractions. These findings showed that rather large regional<span id="page16428"/> climatic conditions considerably controlled interannual variations in GHGs, <span class="inline-formula"><i>δ</i><sup>13</sup></span>C-CO<span class="inline-formula"><sub>2</sub></span>, and <span class="inline-formula"><i>δ</i><sup>18</sup></span>O-CO<span class="inline-formula"><sub>2</sub></span> through changes in precipitation and air mass.</p>S. NomuraM. NajaM. K. AhmedH. MukaiY. TeraoT. MachidaM. SasakawaP. K. PatraCopernicus PublicationsarticlePhysicsQC1-999ChemistryQD1-999ENAtmospheric Chemistry and Physics, Vol 21, Pp 16427-16452 (2021)

Measurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India, and Comilla, Bangladesh

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