Characterization of Black Carbon Aerosols over Darjeeling - A High Altitude Himalayan Station in Eastern India

Abstract

A continuous monitoring of black carbon (BC) aerosols was carried over a high altitude station Darjeeling (27°01′N, 88°15′E; 2200 m a.s.l.) at eastern part of Himalaya in India during January 2010-December 2011. In this article, we have presented the results of our analysis of the data collected during this interval. This study is focused on the investigation of the temporal variations, potential sources, long-range transport of BC aerosols along with the meteorological impact on these aerosols. BC is found to exhibit strong seasonal variation with the maximum concentration during premonsoon (5.0 ± 1.1 µg/m 3 ) followed by winter (3.9 ± 2.2 µg/m 3 ), postmonsoon (2.9 ± 1.0 µg/m 3 ) and minimum during monsoon (1.7 ± 0.7 µg/m 3 ). BC concentration varied between 0.2-12.8 µg/m 3 with an average of 3.4 ± 1.9 µg/m 3 over the entire period of study. The diurnal variation of BC aerosol shows sharp morning and evening peaks associated to the local anthropogenic activities as well as the impact of up-slope mountain wind. Amongst the long distant sources, BC concentration associated with the transport from Middle East countries and passing over South West countries like Pakistan, Afghanistan and IndoGangetic Plain is found to be comparatively higher. It is observed that the contributions of local emissions, long-range transport and mountain wind transport are approximately 56%, 27% and 17%, respectively, towards the total BC loading over Darjeeling during premonsoon. Fossil fuel emissions during premonsoon and biomass burning during winter are the major sources of BC with the overall dominance of fossil fuel burning throughout the entire study period. The BC concentration over Darjeeling is found to be much higher than any other high altitude stations in India and Nepal and even higher and comparable with some of the metro-cities in India.

How the Atmosphere over Eastern Himalaya, India is Polluted with Carbonyl Compounds? Temporal Variability and Identification of Sources

“…The ambient level of acetaldehyde over Darjeeling was found to be higher than most of the cities in India and abroad. Earlier, we observed higher concentrations of carbonaceous aerosols and VOCs (BTEX: Benzene, Toluene, Ethylbenzene, Xylene) over Darjeeling from various anthropogenic activities and their concentrations were comparable and higher than some of the metro-cities in India (Sarkar et al, , 2015. The sources of carbonaceous aerosols and BTEX are similar to that of acetaldehyde over Darjeeling.…”

“…As far as Himalaya is concerned, a case study was performed on atmospheric CCs in Bhutan (Wangchuk et al, 2015). Earlier we have reported high ambient level of black carbon aerosols (Sarkar et al, 2015), volatile organic compounds , submicron aerosols (Adak et al, 2014), anthropogenic aerosols (Chatterjee et al, 2010(Chatterjee et al, , 2012Roy et al, 2016) over Darjeeling at eastern Himalaya. This prompted us to make a year-long study on other major part of carbonaceous pollutants like carbonyl compounds over this part of Himalaya where the loading of atmospheric pollutants are of major concern due to increased anthropogenic activities related to tourists and rapid pace of urbanization and socio-economic development.…”

Spring-Time Enhancement in Aerosol Burden over a High-Altitude Location in Western Trans-Himalaya:Results from Long-Term Observations

“…This is due to the proximity of NCO-P to Kathmandu valley (~200 km away) and transport of pollutants to the station from Khumbu valley (which represents a natural chimney through which pollutants can be vented to NCO-P and the higher Himalaya) through thermal winds (mountain-valley breeze circulation) 34 . Notwithstanding the large differences in magnitude, the seasonal trends in the observed M BC at Hanle are quite similar to that in NCO-P. Table 1 provides a detailed comparison of M BC at Hanle with other highaltitude Himalayan locations [33][34][35][36][37][38][39][40][41] . Other stations are at a much lower elevation and less pristine compared to Hanle in view of the observed higher BC mass loading over these locations.…”

“…Also, the nature of upwind regions which contribute to aerosol transport is another determining factor. Recently, Sarkar et al 38 examined M BC over Darjeeling station, located in the eastern Himalaya in India, and pointed out the distinctiveness of the impact of aerosol transport over different parts of the Himalaya. Although aerosol transport through west/northwest airmasses is more frequent in dry periods over the Himalaya, its impact is much higher over the eastern Himalaya compared to the western and the central Himalayan stations.…”

Dependence of Daily Aerosol Wet Deposition on Precipitation at Appalachian Mountains Site in the United States

“…Observations in mountain areas can provide insight into: a) long-range transport of air pollutants; b) impact of acid rain on alpine forests and their response to pollution; c) fog scavenging and aerosol removal from direct cloud impact with terrain slopes; d) role of orographic convection and its effects on precipitation; e) heterogeneous ice nucleation of various aerosol types (Wrzesinsky and Klemm, 2000;Avila and Rodà, 2002;Igawa et al, 2002;Thalmann et al, 2002;Baumgardner et al, 2003;Burkard et al, 2003;Bayraktar and Turalioglu, 2005;Kim et al, 2006;Fischer et al, 2007;Budhavant et al, 2009;Calvo et al, 2012;Pawar et al, 2012;Hallar et al, 2013;Li et al, 2014;Conen et al, 2015;Weiss-Penzias et al, 2015;Sarkar et al, 2015).…”