Characteristics of Particulate-Phase Polycyclic Aromatic Hydrocarbons (PAHs) in the Atmosphere over the Central Himalayas

Abstract

PAH concentrations were measured in total suspended particle (TSP) samples collected from six sites along two southnorth transects across the central Himalayas from April 2013 to March 2014. The annual average TSP and PAH (especially 5-and 6-ring compounds) concentrations were found to decrease noticeably northwards along both transects. At rural and urban sites, the TSP and PAH concentrations showed clear seasonal variations, with the lower concentrations around the mid-monsoon season and the higher values in the winter season. Meanwhile, at the remote sites (e.g., Nyalam and Zhongba), these pollutants generally remained constant throughout the year but with relatively higher levels during the pre-monsoon season. Both IndP/(IndP + BghiP) and Fla/(Fla + Pyr) ratios suggested that atmospheric PAHs from urban and rural sites were mainly associated with emissions from biomass burning, coal burning and petroleum combustion. However, the contribution of biomass burning increased at remote sites. Similar compositions of PAHs were found at three remote sites located on both sides of the Himalayas (Jomsom, Zhongba, and Nyalam), suggesting that the northern side of the Himalayas may be affected by anthropogenic emissions from the Indo-Gangetic Plain (IGP) via long-range atmospheric transport. This work provides a database of PAHs in central Himalayas for further assessing environmental risk of air pollution in the remote regions.

n‐Alkanes and PAHs in the Southeastern Tibetan Plateau: Characteristics and Correlations With Brown Carbon Light Absorption

“…Journal of Geophysical Research: Atmospheres of the central Himalayas (5.57 ng m −3 ), and the Mount Tai in northern China (1.36 ng m −3 ) (Chen et al, 2017;Liu et al, 2017;Wang et al, 2018;Yang et al, 2017). At the remote Lulang site, the present total-PAHs concentrations were comparable with those from the previous study (2.0 ± 1.2 ng m −3 ) (Wang et al, 2015).…”

“…Higher concentrations of PAHs were reported in the winter-spring season. The major source region of these organic species was the Indo-Gangetic Plain (Chen et al, 2014(Chen et al, , 2017(Chen et al, , 2018Gong et al, 2018;Wang et al, 2015Wang et al, , 2018. southeastern TP) is to the west of the Yarlung Tsangpo Grand Canyo with two typical air circulation patterns, which is conducive to assess the pollutants variations and transport patterns in the area (Wang et al, 2015).…”

Transport of regional pollutants through a remote trans-Himalayan valley in Nepal

“…Numerous studies have investigated the transport of pollutants from the IGP to the Himalayan foothills, the immediate source region for potential transport to the Tibetan Plateau (TP) (Pant et al, 2006;Dumka et al, 2008;Komppula et al, 2009;Hyvärinen et al, 2009;Ram et al, 2010;Brun et al, 2011;Gautam et al, 2011;Srivastava et al, 2012). Further, a suite of studies involving satellite imagery (Ramanathan et al, 2007a;Brun et al, 2011), back trajectories (Lu et al, 2011), model calculations (Kopacz et al, 2011;Zhang et al, 2015), ice core analyses (Lee et al, 2008;Kang et al, 2010), and measurements in the higher Himalaya Chen et al, 2017) strongly suggest that pollutants are efficiently transported from the IGP to the higher Himalaya and onto the Tibetan Plateau, especially during spring prior to the monsoon. This transport north of the Himalayas is potentially concerning as the TP plays a vital role in regulating the regional climate due to its effect on the Asian summer monsoon (ASM) and the hydrologic cycle.…”

Study on Mercury in PM10 at an Urban Site in the Central Indo-Gangetic Plain: Seasonal Variability and Influencing Factors

“…Studies have suggested the high concentrations of PM in this region as the main reason for poor air quality, reduced visibility, and fog and haze formation during wintertime (Ram et al, 2012;Ghosh et al, 2014). Biomass burning significantly affects regional air quality in the IGP, particularly in the winter (Chen et al, 2017). Major sources of biomass-burning emissions are crop harvesting and the common practice of wood burning for domestic use (Bikkina et al, 2017).…”