Size-Segregated Characteristics of Carbonaceous Aerosols during the Monsoon and Non-Monsoon Seasons in Lhasa in the Tibetan Plateau

In this paper, we intensively collected atmospheric particulate matter (PM) with different diameters (size ranges: <0.49, 0.49–0.95, 0.95–1.5, 1.5–3.0, 3.0–7.2, and >7.2 μm) in Lhasa during the monsoon and non-monsoon seasons. The results clearly showed that the concentrations of PM, organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) during the non-monsoon season were much higher than the concentrations during the monsoon season. During the monsoon season, a bimodal size distribution of the OC and WSOC, which were at <0.49 μm and >7.2 μm, respectively, and a unimodal size distribution at <0.49 μm for the EC were observed. However, during the non-monsoon season, there was a trimodal size distribution of the OC and WSOC (<0.49 μm, 1.5–3.0 μm, and >7.2 μm), and a unimodal size distribution of the EC (<0.49 μm). Possible sources of the carbonaceous components were revealed by combining the particle size distribution and the correlation analysis. OC, EC, and WSOC were likely from the photochemical transformation of biogenic and anthropogenic VOC, and the incomplete combustion of biomass burning and fossil fuels at <0.49 μm, whilst they were also likely to be from various types of dust and biogenic aerosols at >7.2 μm. OC and WSOC at 1.5–3.0 μm were likely to have been from the burning of yak dung and photochemical formation. The above results may draw attention in the public and scientific communities to the issues of air quality in the Tibetan Plateau.

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Carbonaceous aerosols on the south edge of the Tibetan Plateau: concentrations, seasonality and sources

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-25051-2014 ◽

2014 ◽

Vol 14 (18) ◽

pp. 25051-25082 ◽

Cited By ~ 5

Author(s):

Z. Cong ◽

S. Kang ◽

K. Kawamura ◽

B. Liu ◽

X. Wan ◽

...

Keyword(s):

Tibetan Plateau ◽

Organic Carbon ◽

Monsoon Season ◽

Air Pollutant ◽

Water Soluble ◽

Atmospheric Environment ◽

The Tibetan Plateau ◽

Carbonaceous Aerosols ◽

The South ◽

Aerosol Composition

Abstract. To quantitatively evaluate the effect of carbonaceous aerosols on the south edge of the Tibetan Plateau, aerosol samples were collected weekly from August 2009 to July 2010 at Mt. Everest (Qomolangma Station for Atmospheric and Environmental Observation and Research, briefly QOMS, 28.36° N, 86.95° E, 4276 m a.s.l.). The samples were analyzed for organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC) and major ions. The average concentrations of OC, EC and WSOC were 1.43, 0.25 and 0.77 μg m−3, respectively. The concentration levels of OC and EC at QOMS are comparable to those at high elevation sites on the southern slopes of the Himalayas (Langtang and NCO-P), but three to six times lower than those at Manora Peak, India and Godavari, Nepal. Sulfate was the most abundant anion species followed by nitrate, accounting for 25 and 12% of total ionic mass, respectively. Ca2+ was the most abundant cation species (annual average of 0.88 μg m−3). The various aerosol compositions showed distinctive seasonality. The dust loading, represented by Ca2+ concentration, was relatively constant throughout the year. While OC, EC and other ionic species (NH4+, K+, NO3−, and SO42−) exhibited a pronounced peak in the pre-monsoon period and a minimum in the monsoon season. Similar seasonal trends of aerosol composition were also reported previously from the southern slope of the Himalayas, such as Langtang and NCO-P. This phenomenon indicates that both slopes of Himalayas share a common atmospheric environment regime. The strong correlation of OC and EC in QOMS aerosols with K+ and levoglucosan indicates that they were mainly originated from biomass burning. The active fire spots observed by MODIS and their backward trajectories further demonstrate that in pre-monsoon season, agricultural and forest fires in the northern India and Nepal were most likely sources of carbonaceous aerosol at QOMS. In addition to large-scale atmospheric circulation, the unique mountain/valley breeze system in the Himalayas can also have an important effect on air pollutant transport.

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Carbonaceous aerosols on the south edge of the Tibetan Plateau: concentrations, seasonality and sources

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-1573-2015 ◽

2015 ◽

Vol 15 (3) ◽

pp. 1573-1584 ◽

Cited By ~ 123

Author(s):

Z. Cong ◽

S. Kang ◽

K. Kawamura ◽

B. Liu ◽

X. Wan ◽

...

Keyword(s):

Tibetan Plateau ◽

Organic Carbon ◽

Monsoon Season ◽

Air Pollutant ◽

Water Soluble ◽

Atmospheric Environment ◽

The Tibetan Plateau ◽

Carbonaceous Aerosols ◽

The South ◽

Aerosol Composition

Abstract. To quantitatively evaluate the effect of carbonaceous aerosols on the south edge of the Tibetan Plateau, aerosol samples were collected weekly from August 2009 to July 2010 at Qomolangma (Mt. Everest) Station for Atmospheric and Environmental Observation and Research (QOMS, 28.36° N, 86.95° E, 4276 m a.s.l.). The average concentrations of organic carbon (OC), elemental carbon (EC) and water-soluble organic carbon were 1.43, 0.25 and 0.77 μg m−3, respectively. The concentration levels of OC and EC at QOMS are comparable to those at high-elevation sites on the southern slopes of the Himalayas (Langtang and Nepal Climate Observatory at Pyramid, or NCO-P), but 3 to 6 times lower than those at Manora Peak, India, and Godavari, Nepal. Sulfate was the most abundant anion species followed by nitrate, accounting for 25 and 12% of total ionic mass, respectively. Ca2+ was the most abundant cation species (annual average of 0.88 μg m−3). The dust loading, represented by Ca2+ concentration, was relatively constant throughout the year. OC, EC and other ionic species (NH4+, K+, NO3− and SO42−) exhibited a pronounced peak in the pre-monsoon period and a minimum in the monsoon season, being similar to the seasonal trends of aerosol composition reported previously from the southern slope of the Himalayas, such as Langtang and NCO-P. The strong correlation of OC and EC in QOMS aerosols with K+ and levoglucosan indicates that they mainly originated from biomass burning. The fire spots observed by MODIS and backward air-mass trajectories further demonstrate that in pre-monsoon season, agricultural and forest fires in northern India and Nepal were most likely sources of carbonaceous aerosol at QOMS. Moreover, the CALIOP observations confirmed that air-pollution plumes crossed the Himalayas during this period. The highly coherent variation of daily aerosol optical depth (500 nm) between QOMS and NCO-P indicates that both slopes of the Himalayas share a common atmospheric environment regime. In addition to large-scale atmospheric circulation, the unique mountain/valley breeze system can also have an important effect on air-pollutant transport.

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Spatio-temporal variability and light absorption property of carbonaceous aerosol in a typical glacierization region of the Tibetan Plateau

10.5194/acp-2017-865 ◽

2017 ◽

Author(s):

Hewen Niu ◽

Shichang Kang ◽

Hailong Wang ◽

Rudong Zhang ◽

Xixi Lu ◽

...

Keyword(s):

Tibetan Plateau ◽

East Asia ◽

Monsoon Season ◽

The Tibetan Plateau ◽

Carbonaceous Aerosols ◽

Carbonaceous Matter ◽

Near Surface ◽

Post Monsoon ◽

Local Sources ◽

Post Monsoon Season

Abstract. The high altitude glacierized regions of the Tibetan Plateau (TP) are influenced by carbonaceous aerosols from local sources and long range transport from the adjoining areas. Deposition and accumulation of light-absorbing carbonaceous matters on glacier surfaces can alter the energy balance of glaciers. In this study, two years (December 2014 to December 2016) of continuous observations of carbonaceous aerosols performed in glacierized region of Mt. Yulong (4510 m a.s.l.) and Ganhaizi (GHZ) basin (3054 m a.s.l.) are analyzed. The mass absorption efficiency (MAE) of black carbon (BC) was determined for the first time in Mt. Yulong using a thermal-optical carbon analyzer. The average BC and organic carbon (OC) concentrations were 1.51 ± 0.93 and 2.57 ± 1.32 μg m−3, respectively. The average SOC (secondary OC) concentration, quantified using BC-tracer method, was 1.67 ± 1.15 μg m−3. Monthly mean BC concentrations from monsoon to post-monsoon season were higher than OC in the high altitudes (approximately 5000 m a.s.l.) of Mt. Yulong. The concentrations of carbonaceous matter have distinct spatial and inter-annual variations in this glacierization area. High carbonaceous matter associated with OC (including both SOC and POC) in GHZ basin was mainly contributed from tour bus emissions. The annual mean OC / BC ratio was 2.45 ± 1.96 in Mt. Yulong. Strong photochemical reactions and local tourism activities in monsoon season were the main factors inducing high OC / BC ratios in the Mt. Yulong region. The mean MAE of BC, measured at 632 nm with a thermal-optical protocol under the filter-based method, was 6.82 ± 0.73 m2 g−1, comparable with the results from other studies. Strong seasonal and spatial variations of BC MAE were largely related to the OC and SOC abundance. Source attribution analysis using a global aerosol-climate model, equipped with a BC source tagging technique, suggests that East Asia emissions, including local sources, have the dominant contribution (over 50 %) to annual mean near-surface BC at the two sites. There is also a strong seasonal variation in the regional source apportionment. South Asia has the largest contribution during the pre-monsoon season, while East Asia dominates the monsoon season and post-monsoon season. Results in this study have great implications for accurately evaluating the influences of carbonaceous matter on glacial melting and water resource supply in glacierization areas.

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Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-15629-2010 ◽

2010 ◽

Vol 10 (6) ◽

pp. 15629-15670

Author(s):

P. Shrestha ◽

A. P. Barros ◽

A. Khlystov

Keyword(s):

Boundary Layer ◽

Chemical Composition ◽

Organic Carbon ◽

Size Distribution ◽

Elemental Carbon ◽

Monsoon Season ◽

Number Concentration ◽

Water Soluble ◽

Aerosol Size Distribution ◽

Aerosol Number Concentration

Abstract. Aerosol particle number size distribution and chemical composition were measured at two low altitude sites, one urban and one relatively pristine valley, in Central Nepal during the 2009 pre-monsoon season (May–June). This is the first time that aerosol size distribution and chemical composition were measured simultaneously at lower elevation in the Middle Himalayan region in Nepal. The aerosol size distribution was measured using a Scanning Mobility Particle Sizer (SMPS, 14~340 nm), and the chemical composition of the filter samples collected during the field campaign was analyzed in the laboratory. Teflon membrane filters were used for ion chromatography (IC) and water-soluble organic carbon and nitrogen analysis. Quartz fiber filters were used for organic carbon and elemental carbon analysis. Multi-lognormal fits to the measured aerosol size distribution indicated a consistent larger mode around 100 nm which is usually the oldest, most processed background aerosol. The smaller mode was located around 20 nm, which is indicative of fresh but not necessarily local aerosol. The diurnal cycle of the aerosol number concentration showed the presence of two peaks (early morning and evening), during the transitional period of boundary layer growth and collapse. The increase in number concentration during the peak period was observed for the entire size distribution. Although the possible contribution of local emissions in size ranges similar to the larger mode cannot be completely ruled out, another plausible explanation is the mixing of aged elevated aerosol in the residual layer during the morning period as suggested by previous studies. Similarly, the evening time concentration peaks when the boundary layer becomes shallow concurrent with increase in local activity. A decrease in aerosol number concentration was observed during the nighttime with the development of cold (downslope) mountain winds that force the low level warmer air in the valley to rise. The mountain valley wind mechanisms induced by the topography along with the valley geometry appear to have a strong control in the diurnal cycle of the aerosol size distribution. During the sampling period, the chemical composition of PM2.5 was dominated by organic matter at both sites. Organic carbon (OC) comprised the major fraction (64~68%) of the aerosol concentration followed by ionic species (24~26% mainly SO42- and NH4+). Elemental Carbon (EC) compromised 7~10% of the total composition. A large fraction of OC was found to be water soluble (nearly 27% at both sites).

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Light absorption and fluorescence characteristics of water-soluble organic compounds in carbonaceous particles at a typical remote site in the southeastern Himalayas and Tibetan Plateau

10.5194/egusphere-egu21-3653 ◽

2021 ◽

Author(s):

Chao Zhang ◽

Meilian Chen ◽

Shichang Kang ◽

Fangping Yan ◽

Chaoliu Li

Keyword(s):

Tibetan Plateau ◽

Organic Carbon ◽

South Asia ◽

Light Absorption ◽

Fluorescence Analysis ◽

Water Soluble ◽

The Tibetan Plateau ◽

Remote Site ◽

Carbonaceous Particles ◽

Fluorescence Characteristics

Carbonaceous particles play an important role in climate change, and the increase in their emission and deposition causes glacier melting in the Himalayas and the Tibetan Plateau (HTP). This implies that studying their basic characteristics is crucial for a better understanding of the climate forcing observed in this area. Thus, we investigated characteristics of carbonaceous particles at Yaze village, a typical remote site of southeastern HTP.&#160; The results showed that the organic carbon and elemental carbon concentrations at this study site were 1.86 &#177; 0.84 and 0.18 &#177; 0.09 &#956;g m-3, respectively, which were much lower than those reported for other frequently monitored stations in the same region. Thus, these values reflect the background characteristics of the study site. Additionally, the absorption coefficient per mass (&#945;/&#961;) of water-soluble organic carbon (WSOC) at 365 nm was 0.60 &#177; 0.19 m2 g-1, which was lower than those reported for other remote stations in the HTP. This value could be attributed to a lower and higher contribution of mineral dust and secondary organic carbon, respectively. Multi-dimensional fluorescence analysis showed that the WSOC consisted of approximately 37% and 63% protein and humic-like components, respectively, and the latter was identified as the determining component of light absorption ability of the WSOC. Combined the significant relationships between WSOC and sulfate ion, potassium ion, and nitrate ion with the air masses at the study site originated primarily from South Asia, it is suggested that the levels of carbonaceous particles in Yaze village were predominantly influenced by emissions from South Asia.

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Chemical composition and aerosol size distribution of the middle mountain range in the Nepal Himalayas during the 2009 pre-monsoon season

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-11605-2010 ◽

2010 ◽

Vol 10 (23) ◽

pp. 11605-11621 ◽

Cited By ~ 40

Author(s):

P. Shrestha ◽

A. P. Barros ◽

A. Khlystov

Keyword(s):

Boundary Layer ◽

Chemical Composition ◽

Organic Carbon ◽

Size Distribution ◽

Elemental Carbon ◽

Monsoon Season ◽

Number Concentration ◽

Water Soluble ◽

Aerosol Size Distribution ◽

Aerosol Number Concentration

Abstract. Aerosol particle number size distribution and chemical composition were measured at two low altitude sites, one urban and one relatively pristine valley, in Central Nepal during the 2009 pre-monsoon season (May–June). This is the first time that aerosol size distribution and chemical composition were measured simultaneously at lower elevations in the middle Himalayan region in Nepal. The aerosol size distribution was measured using a Scanning Mobility Particle Sizer (SMPS, 14–340 nm), and the chemical composition of the filter samples collected during the field campaign was analyzed in the laboratory. Teflon membrane filters were used for ion chromatography (IC) and water-soluble organic carbon and nitrogen analysis. Quartz fiber filters were used for organic carbon and elemental carbon analysis. Multi-lognormal fits to the measured aerosol size distribution indicated a consistent larger mode around 100 nm which is usually the oldest, most processed background aerosol. The smaller mode was located around 20 nm, which is indicative of fresh but not necessarily local aerosol. The diurnal cycle of the aerosol number concentration showed the presence of two peaks (early morning and evening), during the transitional periods of boundary layer growth and collapse. The increase in number concentration during the peak periods was observed for the entire size distribution. Although the possible contribution of local emissions in size ranges similar to the larger mode cannot be completely ruled out, another plausible explanation is the mixing of aged elevated aerosol in the residual layer during the morning period as suggested by previous studies. Similarly, the evening time concentration peaks when the boundary layer becomes shallow concurrent with increase in local activity. A decrease in aerosol number concentration was observed during the nighttime with the development of cold (downslope) mountain winds that force the low level warmer air in the valley to rise. The mountain valley wind mechanisms induced by the topography along with the valley geometry appear to have a strong control in the diurnal cycle of the aerosol size distribution. During the sampling period, the chemical composition of PM2.5 was dominated by organic matter at both sites. Organic carbon (OC) comprised the major fraction (64–68%) of the aerosol concentration followed by ionic species (24–26%, mainly SO42− and NH4+). Elemental Carbon (EC) compromised 7–10% of the total composition and 27% of OC was found to be water soluble at both sites. The day-to-day variability observed in the time series of aerosol composition could be explained by the synoptic scale haze that extended to the sampling region from the Indian Gangetic Plain (IGP), and rainfall occurrence. In the presence of regional scale haze during dry periods, the mean volume aerosol concentration was found to increase and so did the aerosol mass concentrations.

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Size distribution of PM20 observed to the north of the Tibetan Plateau

Journal of Mountain Science ◽

10.1007/s11629-020-6086-3 ◽

2021 ◽

Vol 18 (2) ◽

pp. 367-376

Author(s):

Cheng-long Zhou ◽

Fan Yang ◽

Wen Huo ◽

Ali Mamtimin ◽

Xing-hua Yang

Keyword(s):

Tibetan Plateau ◽

Size Distribution ◽

The Tibetan Plateau ◽

The North

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Size-Segregated Atmospheric Humic-Like Substances (HULIS) in Shanghai: Abundance, Seasonal Variation, and Source Identification

Atmosphere ◽

10.3390/atmos12050526 ◽

2021 ◽

Vol 12 (5) ◽

pp. 526

Author(s):

Tianming Sun ◽

Rui Li ◽

Ya Meng ◽

Yu Han ◽

Hanyun Cheng ◽

...

Keyword(s):

Seasonal Variation ◽

Size Distribution ◽

Principal Component ◽

Water Soluble ◽

Atmospheric Particulate Matter ◽

Biomass Combustion ◽

Vehicle Exhaust ◽

Total Suspended Particulates ◽

Condensation Mode ◽

Water Soluble Organic Carbon

Humic-like substances (HULIS) are of great interest due to their optical and chemical characteristics. In this study, a total of 180 samples of atmospheric particulate matter (PM) of different sizes were collected from summer 2018 to spring 2019, in order to analyze the size distribution, to investigate the seasonal variation and then to identify the key sources of HULIS. The annual mean concentration of HULIS in the total suspended particulates reached 5.12 ± 1.42 μg/m3. The HULIS concentration was extremely higher in winter (8.35 ± 2.06 μg/m3) than in autumn (4.88 ± 0.95 μg/m3), in summer (3.62 ± 1.68 μg/m3) and in spring (3.36 ± 0.99 μg/m3). The average annual ratio of water-soluble organic carbon (WSOC) to OC and the ratio of HULIS to WSOC reached 0.546 ± 0.092 and 0.56 ± 0.06, respectively. Throughout the whole year, the size distributions of WSOC and HULIS-C were relatively smooth. The peaks of WSOC appeared at 1.8~3.2 μm and 0.56~1.0 μm, while the peaks of HULIS-C were located at 3.2~5.6 μm, 1.0~1.8 μm and 0.18~0.32 μm. The distribution of the HULIS particle mode was similar in spring, summer and autumn, while there was a lower proportion of the coarse mode and a higher proportion of the condensation mode in winter. By using the comprehensive analysis of principal component analysis (PCA), air mass backward trajectories (AMBTs) and fire point maps, key sources of WSOC and HULIS in Shanghai were identified as biomass combustion (48.42%), coal combustion (17.49%), secondary formation (16.07%) and vehicle exhaust (5.37%). The remaining part might be contributed by crustal dust sources, marine sources and/or other possible sources. This study provides new insight into the characteristics and size distribution of HULIS in Shanghai, thereby providing a practical base for further modeling.

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Correction: Aged dissolved organic carbon exported from rivers of the Tibetan Plateau

PLoS ONE ◽

10.1371/journal.pone.0181295 ◽

2017 ◽

Vol 12 (7) ◽

pp. e0181295 ◽

Cited By ~ 1

Author(s):

Bin Qu ◽

Mika Sillanpää ◽

Chaoliu Li ◽

Shichang Kang ◽

Aron Stubbins ◽

...

Keyword(s):

Tibetan Plateau ◽

Organic Carbon ◽

Dissolved Organic Carbon ◽

The Tibetan Plateau

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Potential Production of Carbon Gases and Their Responses to Paleoclimate Conditions: An Example From Xiaolongtan Basin, Southeast Tibetan Plateau

Frontiers in Earth Science ◽

10.3389/feart.2021.582062 ◽

2021 ◽

Vol 9 ◽

Author(s):

Gen Wang ◽

Yongli Wang ◽

Zhifu Wei ◽

Zepeng Sun ◽

Wei He ◽

...

Keyword(s):

Organic Matter ◽

Tibetan Plateau ◽

Low Temperature ◽

Organic Carbon ◽

Carbon Cycle ◽

Higher Plants ◽

The Tibetan Plateau ◽

Climate Conditions ◽

Burial Flux ◽

Carbon Gases

Uplift of the Tibetan Plateau plays a significant and lasting role in the variations of climate conditions and global carbon cycle. However, our knowledge is limited due to the lack of long-sequence records revealing rates of CO2 and CH4 production, hampering our understanding of the relationship between paleoclimatic conditions, carbon cycling and greenhouse gas flux. Here, we present a combination of paleoclimate records and low-temperature thermal simulation results from sediments of the Xiaolongtan Basin at the southeastern margin of the Qinghai-Tibetan Plateau, spanning the late Miocene (14.1 ∼ 11.6 Ma). The n-alkane-derived proxies suggested that the sources of organic matter were obviously different: a mixed source including lower organisms and terrestrial higher plants for the Dongshengqiao Formation from 14.1 to 12.6 Ma, and a predominant contribution from terrestrial higher plants for Xiaolongtan Formation between 12.6 and 11.6 Ma. The paleoclimate was generally warm and humid as reflected by the lipid biomarkers, consistent with previous studies. In addition, the carbon gases (including CO2 and hydrocarbon gases) generated by the low-temperature thermal simulation experiments indicated a production rate of CO2 and CH4 were as high as 88,000 ml/kg rock and 4,000 ml/kg rock, respectively, implying there were certain amounts of carbon gases generated and released into the atmosphere during their shallow burial stage. Besides, the calculated production rate of carbon gases and the estimated burial flux of organic carbon varied in response to the variations of paleoclimate conditions. Based on these observations, we propose that the climate conditions predominantly controlled the formation and accumulation of organic matter, which consequently affected the production of carbon gases and burial flux of organic carbon. The results presented here may provide a significant insight into the carbon cycle in the southeast of the Tibetan Plateau.

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