Chemical characterization of long-range transport biomass burning emissions to the Himalayas: insights from high-resolution aerosol mass spectrometry

Abstract

Abstract. An intensive field measurement was conducted at a remote, background, high-altitude site (Qomolangma Station, QOMS, 4276 m a.s.l.) in the northern Himalayas, using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) along with other collocated instruments. The field measurement was performed from 12 April to 12 May 2016 to chemically characterize the high time-resolved submicron particulate matter (PM 1 ) and obtain the dynamic processes (emissions, transport, and chemical evolution) of biomass burning (BB), frequently transported from South Asia to the Himalayas during pre-monsoon season. Overall, the average (±1σ ) PM 1 mass concentration was 4.44 (±4.54) µg m −3 for the entire study, which is comparable with those observed at other remote sites worldwide. Organic aerosol (OA) was the dominant PM 1 species (accounting for 54.3 % of total PM 1 on average) followed by black carbon (BC) (25.0 %), sulfate (9.3 %), ammonium (5.8 %), nitrate (5.1 %), and chloride (0.4 %). The average size distributions of PM 1 species all peaked at an overlapping accumulation mode (∼ 500 nm), suggesting that aerosol particles were internally well-mixed and aged during long-range transport. Positive matrix factorization (PMF) analysis on the high-resolution organic mass spectra identified three distinct OA factors, including a BB-related OA (BBOA, 43.7 %), a nitrogen-containing OA (NOA, 13.9 %) and a more-oxidized oxygenated OA (MO-OOA, 42.4 %). Two polluted episodes with enhanced PM 1 mass loadings and elevated BBOA contributions from the west and southwest of QOMS during the study were observed. A typical BB plume was investigated in detail to illustrate the chemical evolution of aerosol characteristics under distinct air mass origins, meteorological conditions, and atmospheric oxidation processes.

Regional Differences of Chemical Composition and Optical Properties of Aerosols in the Tibetan Plateau

“…Aerosol sources for these two sites Each arrow corresponds to the addition of a particular functional group to an aliphatic carbon and the percentage number indicate the data points in each region to the total data points. Based on satellite monitoring and in situ observations (Kumar et al, 2011;Zhang et al, 2018), biomass burning has been identified as the major source of OA in the southern TP, while anthropogenic emissions (coal combustion and fossil fuel usage) are the major source of OA in the northern TP (Figure 12). The plot of DBE vs. n C .…”

“…could be generally determined by air mass trajectory analysis which show that the air mass to WLG were all from the inland of northwest of China with about 50% from the source at short distance (100-200 km), while they were dominantly from northwest of India with long distance (up to 1,000 km) ( Figure S5). Based on satellite monitoring and in situ observations (Kumar et al, 2011;Zhang et al, 2018), biomass burning has been identified as the major source of OA in the southern TP, while anthropogenic emissions (coal combustion and fossil fuel usage) are the major source of OA in the northern TP (Figure 12). This is determined by the energy structure and distribution of natural resources in the countries adjacent to the northern and southern part of the TP region.…”

“…Water-soluble inorganic ions were analyzed as components of aerosol chemical composition, attributing them to common anthropogenic activities . Aerosol mass spectrometry (AMS) has been applied in field studies of the aerosol chemistry which reported description of main organic aerosol (OA) classes, their temporal variations, variability in chemical composition, sources, and oxidation states Zhang et al, 2018). Measurements of the organic to elemental carbon ratio (OC/EC) show elevated organic content in the southern TP attributed to the aged biomass burning emissions (Ming et al, 2010).…”

“…Measurements of the organic to elemental carbon ratio (OC/EC) show elevated organic content in the southern TP attributed to the aged biomass burning emissions (Ming et al, 2010). Aerosol mass spectrometry (AMS) has been applied in field studies of the aerosol chemistry which reported description of main organic aerosol (OA) classes, their temporal variations, variability in chemical composition, sources, and oxidation states Zhang et al, 2018). Molecular characterization of volatile OA fractions has been reported based on the gas-phase MS measurements and provided further insights on OA sources and chemistry (Hegde & Kawamura, 2012).…”

Molecular characterization of organic aerosol in Himalayas: insight from ultra-high resolution mass spectrometry

“…Qomolangma from Apr. 12 to May 12, 2016 using a suit of 83 instruments (Zhang et al, 2018b), and the instruments used in this study includes a HR-ToF-84 AMS (Aerodyne Research Inc., Billerica, MA, USA) for 5-min size-resolved chemical 85 compositions (organics, sulfate, nitrate, ammonium, and chloride) of non-refractory submicron 86 particulate matter (NR-PM 1 ) and a photoacoustic extinctionmeter (PAX, DMT Inc., Boulder, 87 CO, USA) for BC mass concentration. The QOMS observatory locates at a remote site with 88 sparse local residents and anthropogenic activities around it, except for a high way for the 89 tourism to the west about 500 m. The tourists are normally increased from June each year due to 90 the warmer weather during summer.…”