High rise in carbonaceous aerosols under very low anthropogenic emissions over eastern Himalaya, India: Impact of lockdown for COVID-19 outbreak.
High rise in carbonaceous aerosols under very low anthropogenic emissions over eastern Himalaya, India: Impact of lockdown for COVID-19 outbreak.
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DOI：
10.1016/j.atmosenv.2020.117947
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发表时间：
2021-01-01
期刊：
影响因子：
--
通讯作者：
Roy A
中科院分区：
文献类型：
--
作者：
Chatterjee A;Mukherjee S;Dutta M;Ghosh A;Ghosh SK;Roy A
本研究旨在探讨在有和没有（极低）人为排放的情况下，高海拔喜马拉雅大气中碳质气溶胶（CA）的相对变化。由于全球COVID - 19爆发，在封锁期间（2020年4月）进行了大气有机碳（OC）和元素碳（EC）的测量，并与正常时期（2019年4月）进行了比较。有趣、意外和令人惊讶的观察结果是，封城期间的OC、EC和总CA (TCA) （OC: 12.1±5.5 μ m−3;EC: 2.2±1.1 μ m−3;TCA: 21.5±10 μ m−3）高于正常时期（OC: 7.04±2.2 μ m−3;EC: 1.9±0.7 μ m−3;TCA: 13.2±4.1 μ m−3）。与正常时期（4.2±1.1）相比，封城期间的OC/EC值也较高（5.7±0.9）。在封城期间（由于NO非常低），较高的地表O3可以更好地促进喜马拉雅针叶林覆盖层释放的生物源性挥发性有机物（BVOCs）光化学氧化形成次生OC （SOC）。封锁期间的SOC（7.6±3.5 μ m−3）是正常时期（3.8±1.4 μ m−3）的两倍。有机碳与O3的回归分析表明，在O3增加量相同的情况下，当人为排放极低且生物排放占主导地位时（锁定），有机碳形成的增加幅度大于人为排放较高时（正常）。浓度加权轨迹（CWT）分析表明，尼泊尔上空的人为活动和印度东北部的森林火灾是正常时期大吉岭上空CA的主要远源。另一方面，在封锁期间，大吉岭上空CA的主要来源地区是区域/本地。研究结果表明，喜马拉雅生物圈作为有机碳的主要来源具有巨大的重要性。研究了新冠肺炎封城对碳质气溶胶的影响。在没有人为排放的情况下，有机碳增加了两倍。在封城期间，较高的臭氧产生较高的二次有机气溶胶。生物源性VOC是封城期间二次有机气溶胶的主要前体。
The present study has been conducted to investigate the relative changes of carbonaceous aerosols (CA) over a high altitude Himalayan atmosphere with and without (very low) anthropogenic emissions. Measurements of atmospheric organic (OC) and elemental carbon (EC) were conducted during the lockdown period (April 2020) due to global COVID 19 outbreak and compared with the normal period (April 2019). The interesting, unexpected and surprising observation is that OC, EC and the total CA (TCA) during the lockdown (OC: 12.1 ± 5.5 μg m−3; EC: 2.2 ± 1.1 μg m−3; TCA: 21.5 ± 10 μg m−3) were higher than the normal period (OC: 7.04 ± 2.2 μg m−3; EC: 1.9 ± 0.7 μg m−3; TCA: 13.2 ± 4.1 μg m−3). The higher values for OC/EC ratio too was observed during the lockdown (5.7 ± 0.9) compared to the normal period (4.2 ± 1.1). Much higher surface O3 during the lockdown (due to very low NO) could better promote the formation of secondary OC (SOC) through the photochemical oxidation of biogenic volatile organic compounds (BVOCs) emitted from Himalayan coniferous forest cover. SOC during the lockdown (7.6 ± 3.5 μg m−3) was double of that in normal period (3.8 ± 1.4 μg m−3). Regression analysis between SOC and O3 showed that with the same amount of increase in O3, the SOC formation increased to a larger extent when anthropogenic emissions were very low and biogenic emissions dominate (lockdown) compared to when anthropogenic emissions were high (normal). Concentration weighted trajectory (CWT) analysis showed that the anthropogenic activities over Nepal and forest fire over north-east India were the major long-distant sources of the CA over Darjeeling during the normal period. On the other hand, during lockdown, the major source regions of CA over Darjeeling were regional/local. The findings of the study indicate the immense importance of Himalayan biosphere as a major source of organic carbon. Impact of COVID-19 lockdown on the carbonaceous aerosols were studied. Organic carbon was increased by two times in absence of anthropogenic emissions. Higher ozone produced higher secondary organic aerosols during lockdown. Biogenic VOC was main precursor of secondary organic aerosols during lockdown.
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