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首页> 外文期刊>Atmospheric chemistry and physics >Seasonal and diurnal variations in methane and carbon dioxide in the Kathmandu Valley in the foothills of the central Himalayas
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Seasonal and diurnal variations in methane and carbon dioxide in the Kathmandu Valley in the foothills of the central Himalayas

机译：Himalayas中央山麓的加德满都谷甲烷和二氧化碳的季节性和昼夜变异

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摘要

The SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley-Atmospheric Brown Clouds) international air pollution measurement campaign was carried out from December 2012 to June 2013 in the Kathmandu Valley and surrounding regions in Nepal. The Kathmandu Valley is a bowl-shaped basin with a severe air pollution problem. This paper reports measurements of two major greenhouse gases (GHGs), methane (CH4) and carbon dioxide (CO2), along with the pollutant CO, that began during the campaign and were extended for 1 year at the SusKat-ABC supersite in Bode, a semi-urban location in the Kathmandu Valley. Simultaneous measurements were also made during 2015 in Bode and a nearby rural site (Chanban) similar to 25 km (aerial distance) to the southwest of Bode on the other side of a tall ridge. The ambient mixing ratios of methane (CH4), carbon dioxide (CO2), water vapor, and carbon monoxide (CO) were measured with a cavity ring-down spectrometer (G2401; Picarro, USA) along with meteorological parameters for 1 year (March 2013-March 2014). These measurements are the first of their kind in the central Himalayan foothills. At Bode, the annual average mixing ratios of CO2 and CH4 were 419.3 (+/- 6.0) ppm and 2.192 (+/- 0.066) ppm, respectively. These values are higher than the levels observed at background sites such as Mauna Loa, USA (CO2: 396.8 +/- 2.0 ppm, CH4: 1.831 +/- 0.110 ppm) and Waliguan, China (CO2: 397.7 +/- 3.6 ppm, CH4: 1.879 +/- 0.009 ppm) during the same period and at other urban and semi-urban sites in the region, such as Ahmedabad and Shadnagar (India). They varied slightly across the seasons at Bode, with seasonal average CH4 mixing ratios of 2.157 (+/- 0.230) ppm in the pre-monsoon season, 2.199 (+/- 0.241) ppm in the monsoon, 2.210 (+/- 0.200) ppm in the post-monsoon, and 2.214 (+/- 0.209) ppm in the winter season. The average CO2 mixing ratios were 426.2 (+/- 25.5) ppm in the pre-monsoon, 413.5 (+/- 24.2) ppm in the monsoon, 417.3 (+/- 23.1) ppm in the postmonsoon, and 421.9 (+/- 20.3) ppm in the winter season. The maximum seasonal mean mixing ratio of CH4 in winter was only 0.057 ppm or 2.6% higher than the seasonal minimum during the pre-monsoon period, while CO2 was 12.8 ppm or 3.1% higher during the pre-monsoon period (seasonal maximum) than during the monsoon (seasonal minimum). On the other hand, the CO mixing ratio at Bode was 191% higher during the winter than during the monsoon season. The enhancement in CO2 mixing ratios during the pre-monsoon season is associated with additional CO2 emissions from forest fires and agro-residue burning in northern South Asia in addition to local emissions in the Kathmandu Valley. Published CO = CO2 ratios of different emission sources in Nepal and India were compared with the observed CO = CO2 ratios in this study. This comparison suggested that the major sources in the Kathmandu Valley were residential cooking and vehicle exhaust in all seasons except winter. In winter, brick kiln emissions were a major source. Simultaneous measurements in Bode and Chanban (15 July-3 October 2015) revealed that the mixing ratios of CO2, CH4, and CO were 3.8, 12, and 64% higher in Bode than Chanban.
机译：Suskat-ABC（加德满都山谷大气棕色云的可持续氛围）国际空气污染测量运动是从2012年12月到2013年6月在加德满都谷及尼泊尔周边地区进行的。加德满都山谷是一个具有严重空气污染问题的碗状盆地。本文报告了两种主要温室气体（GHG），甲烷（CH4）和二氧化碳（CO2）以及污染物公司的测量，并在竞选期间开始，并在BODE的SUSKAT-ABC Supersite延长了1年，加德满都山谷的半城市地点。在2015年，2015年的同时测量和附近的农村网站（Chanban）类似于25公里（空中距离）到高大脊的另一边的Bode的西南部。用空腔倒影光谱仪（G2401; PICARRO，USA）一起测量甲烷（CH4），二氧化碳（二氧化碳（CO2），水蒸气和一氧化碳（CO）的环境混合比以及气象参数1年（3月2013- 2014年3月）。这些测量是Himalayan山麓中部的第一个。在BODE，CO 2和CH4的年平均混合比分别为419.3（+/- 6.0）ppm和2.192（+/- 0.066）ppm。这些值高于Mauna Loa，USA（CO2：396.8 +/- 2.0 ppm，CH4：1.831 +/- 0.110 ppm）和中国（二氧化碳：397.7 +/- 3.6 ppm， CH4：1.879 +/- 0.009 ppm）在同一时期和该地区的其他城市和半城市地区，如艾哈迈达巴德和Shadnagar（印度）。它们在BODE的季节略微不同，季节性平均CH4混合比率为2.157（+/- 0.230）PPM，在季风季节，2.199（+/- 0.241）PPM，2.210（+/- 0.200） PPM在季风后季后翁，2.214（+/- 0.209）PPM在冬季。在季风的季隆前413.5（+/- 24.2）ppm，417.3（+/- 23.1）ppm，417.3（+/- 24.2）ppm，417.3（+/- 24.2）ppm，417.3（+/- 24.2）ppm，411.9（+/- 20.3）冬季PPM。在季风期间，冬季CH4的最大季节性平均混合比仅为0.057ppm或比季节性最小值高出0.057ppm或2.6％，而在季风期（季节性最大）期间，二氧化碳为12.8ppm或3.1％。季风（季节性最低）。另一方面，在冬季期间，BODE的CO混合比率比季风季节更高。除了在加德满都山谷的当地排放之外，在季风季节前季季度季季度混合比中的增强与南亚北部的额外二氧化碳排放有关。与本研究中观察到的CO = CO2比进行了比较尼泊尔和印度不同排放源的已发表的CO =二氧化碳比率。这种比较建议加德满都山谷的主要来源是除冬季外的所有季节的住宅烹饪和车辆排气。在冬天，砖窑排放是一个主要来源。 BODE和CHANBAN（2015年7月15日）同时测量显示，二氧化碳，CH4和CO的混合比率比CHANBAN为3.8,12和64％。

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