scholarly journals Seasonal variation of secondary organic aerosol tracers in Central Tibetan Plateau

2015 ◽  
Vol 15 (15) ◽  
pp. 8781-8793 ◽  
Author(s):  
R.-Q. Shen ◽  
X. Ding ◽  
Q.-F. He ◽  
Z.-Y. Cong ◽  
Q.-Q. Yu ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Tibetan Plateau ◽  
Temperature Effect ◽  
Secondary Organic Aerosol ◽  
Global Climate ◽  
Organic Aerosol ◽  
High Elevation ◽  
Isoprene Emission ◽  
Central Tibetan Plateau ◽  
Dominant Process

Abstract. Secondary organic aerosol (SOA) affects the earth's radiation balance and global climate. High-elevation areas are sensitive to global climate change. However, at present, SOA origins and seasonal variations are understudied in remote high-elevation areas. In this study, particulate samples were collected from July 2012 to July 2013 at the remote Nam Co (NC) site, Central Tibetan Plateau and analyzed for SOA tracers from biogenic (isoprene, monoterpenes and β-caryophyllene) and anthropogenic (aromatics) precursors. Among these compounds, isoprene SOA (SOAI) tracers represented the majority (26.6 ± 44.2 ng m−3), followed by monoterpene SOA (SOAM) tracers (0.97 ± 0.57 ng m−3), aromatic SOA (SOAA) tracer (2,3-dihydroxy-4-oxopentanoic acid, DHOPA, 0.25 ± 0.18 ng m−3) and β-caryophyllene SOA tracer (β-caryophyllenic acid, 0.09 ± 0.10 ng m−3). SOAI tracers exhibited high concentrations in the summer and low levels in the winter. The similar temperature dependence of SOAI tracers and isoprene emission suggested that the seasonal variation of SOAI tracers at the NC site was mainly influenced by the isoprene emission. The ratio of high-NOx to low-NOx products of SOAI (2-methylglyceric acid to 2-methyltetrols) was highest in the winter and lowest in the summer, due to the influence of temperature and relative humidity. The seasonal variation of SOAM tracers was impacted by monoterpenes emission and gas-particle partitioning. During the summer to the fall, temperature effect on partitioning was the dominant process influencing SOAM tracers' variation; while the temperature effect on emission was the dominant process influencing SOAM tracers' variation during the winter to the spring. SOAM tracer levels did not elevate with increased temperature in the summer, probably resulting from the counteraction of temperature effects on emission and partitioning. The concentrations of DHOPA were 1–2 orders of magnitude lower than those reported in the urban regions of the world. Due to the transport of air pollutants from the adjacent Bangladesh and northeastern India, DHOPA presented relatively higher levels in the summer. In the winter when air masses mainly came from northwestern India, mass fractions of DHOPA in total tracers increased, although its concentrations declined. The SOA-tracer method was applied to estimate secondary organic carbon (SOC) from these four precursors. The annual average of SOC was 0.22 ± 0.29 μgC m−3, with the biogenic SOC (sum of isoprene, monoterpenes and β-caryophyllene) accounting for 75 %. In the summer, isoprene was the major precursor with its SOC contributions of 81 %. In the winter when the emission of biogenic precursors largely dropped, the contributions of aromatic SOC increased. Our study implies that anthropogenic pollutants emitted in the Indian subcontinent could be transported to the TP and have an impact on SOC over the remote NC.

scholarly journals Seasonal variation of secondary organic aerosol in Nam Co, Central Tibetan Plateau

2015 ◽  
Vol 15 (5) ◽  
pp. 7141-7169 ◽  
Author(s):  
R.-Q. Shen ◽  
X. Ding ◽  
Q.-F. He ◽  
Z.-Y. Cong ◽  
Q.-Q. Yu ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Tibetan Plateau ◽  
Temperature Dependence ◽  
Global Climate ◽  
Organic Aerosol ◽  
High Elevation ◽  
Nam Co ◽  
Central Tibetan Plateau ◽  
Similar Temperature Dependence ◽  
Similar Temperature

Abstract. Secondary organic aerosol (SOA) affects the earth's radiation balance and global climate. High-elevation areas are sensitive to global climate change. However, at present, SOA origins and seasonal variations are understudied in remote high-elevation areas. In this study, particulate samples were collected from July 2012 to July 2013 at the remote Nam Co (NC) site, Central Tibetan Plateau and analyzed for SOA tracers from biogenic (isoprene, monoterpenes and β-caryophyllene) and anthropogenic (aromatics) precursors. Among these compounds, isoprene SOA (SOAI) tracers represented the majority (26.6 ± 44.2 ng m−3), followed by monoterpene SOA (SOAM) tracers (0.97 ± 0.57 ng m−3), aromatic SOA (SOAA) tracer (2,3-dihydroxy-4-oxopentanoic acid, DHOPA, 0.25 ± 0.18 ng m−3) and β-caryophyllene SOA tracer (β-caryophyllenic acid, 0.09 ± 0.10 ng m−3). SOAI tracers exhibited high concentrations in the summer and low levels in the winter. The similar temperature dependence of SOAI tracers and isoprene emission suggested that the seasonal variation of SOAI at the NC site was mainly influenced by isoprene emission. The ratio of high-NOx to low-NOx products of isoprene (2-methylglyceric acid to 2-methyltetrols) was the highest in the winter and the lowest in the summer, due to the influence of temperature and relative humidity. The seasonal variation of SOAM tracers was impacted by monoterpenes emission and tracers partitioning. The similar temperature dependence of SOAM tracers and monoterpenes emission was only observed during winter to spring. SOAM tracer levels did not elevate with increased temperature in the summer, probably resulting from the counteraction of temperature effects on gas/particle partitioning and monoterpenes emission. The concentrations of DHOPA were 1–2 orders of magnitude lower than those reported in the urban regions of the world. Due to the transport of air pollutants from the adjacent Bangladesh and the eastern India, DHOPA presented relatively higher levels in the summer. In the winter when air masses mainly came from the northwestern India, mass fractions of DHOPA in total tracers increased, although its concentrations declined. The SOA-tracer method was applied to estimated secondary organic carbon (SOC) from these four precursors. The annual average of SOC was 0.22 ± 0.29 μg C m−3, with the biogenic SOC (sum of isoprene, monoterpenes and β-caryophyllene) accounting for 75%. In the summer, isoprene was the major precursor with its SOC contributions of 81%. In the winter when the emission of biogenic precursors largely dropped, the contributions of aromatic SOC increased. Our study implies that anthropogenic pollutants emitted in the Indian subcontinent could transport to the TP and have impact on SOC over the remote NC.

scholarly journals A biogenic secondary organic aerosol source of cirrus ice nucleating particles

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Martin J. Wolf ◽  
Yue Zhang ◽  
Maria A. Zawadowicz ◽  
Megan Goodell ◽  
Karl Froyd ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Secondary Organic Aerosol ◽  
Global Climate ◽  
Compositional Analysis ◽  
Field Measurements ◽  
Organic Aerosol ◽  
Cloud Formation ◽  
Ambient Atmosphere ◽  
Atmospheric Conditions ◽  
Mass Fractions

Abstract Atmospheric ice nucleating particles (INPs) influence global climate by altering cloud formation, lifetime, and precipitation efficiency. The role of secondary organic aerosol (SOA) material as a source of INPs in the ambient atmosphere has not been well defined. Here, we demonstrate the potential for biogenic SOA to activate as depositional INPs in the upper troposphere by combining field measurements with laboratory experiments. Ambient INPs were measured in a remote mountaintop location at –46 °C and an ice supersaturation of 30% with concentrations ranging from 0.1 to 70 L–1. Concentrations of depositional INPs were positively correlated with the mass fractions and loadings of isoprene-derived secondary organic aerosols. Compositional analysis of ice residuals showed that ambient particles with isoprene-derived SOA material can act as depositional ice nuclei. Laboratory experiments further demonstrated the ability of isoprene-derived SOA to nucleate ice under a range of atmospheric conditions. We further show that ambient concentrations of isoprene-derived SOA can be competitive with other INP sources. This demonstrates that isoprene and potentially other biogenically-derived SOA materials could influence cirrus formation and properties.

Secondary organic aerosol contributions to PM2.5 in Monterrey, Mexico: Temporal and seasonal variation

2015 ◽  
Vol 153 ◽  
pp. 348-359 ◽  
Author(s):  
Yasmany Mancilla ◽  
Pierre Herckes ◽  
Matthew P. Fraser ◽  
Alberto Mendoza
Keyword(s):  
Seasonal Variation ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol

scholarly journals Future changes in isoprene-epoxydiol-derived secondary organic aerosol (IEPOX-SOA) under the shared socioeconomic pathways: the importance of explicit chemistry

2020 ◽  
Author(s):  
Duseong S. Jo ◽  
Alma Hodzic ◽  
Louisa K. Emmons ◽  
Simone Tilmes ◽  
Rebecca H. Schwantes ◽  
...  
Keyword(s):  
Secondary Organic Aerosol ◽  
Fine Particulate Matter ◽  
Formation Rate ◽  
Critical Role ◽  
Organic Aerosol ◽  
Climatic Conditions ◽  
Basis Set ◽  
Chemical Mechanism ◽  
Isoprene Emission ◽  
Chemistry Modeling

Abstract. Secondary organic aerosol (SOA) is a dominant contributor of fine particulate matter in the atmosphere, but the complexity of SOA formation chemistry hinders the accurate representation of SOA in models. Volatility-based SOA parameterizations have been adopted in many recent chemistry modeling studies and have shown a reasonable performance compared to observations. However, assumptions made in these empirical parameterizations can lead to substantial errors when applied to future climatic conditions as they do not include the mechanistic understanding of processes but are rather fitted to laboratory studies of SOA formation. This is particularly the case for SOA derived from isoprene epoxydiols (IEPOX-SOA), for which we have a higher level of understanding of the fundamental processes than is currently parameterized in most models. We predict future SOA concentrations using an explicit mechanism, and compare the predictions with the empirical parameterization based on the volatility basis set (VBS) approach. We then use the Community Earth System Model 2 (CESM2.1.0) with detailed isoprene chemistry and reactive uptake processes for the middle and end of the 21st century under four Shared Socioeconomic Pathways (SSPs): SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5. With the explicit chemical mechanism, we find that IEPOX-SOA is predicted to increase on average under all future SSP scenarios, however with some variability in the results depending on regions and the scenario chosen. Isoprene emission is the main driver of IEPOX-SOA changes in the future climate, but IEPOX-SOA yield from isoprene emission also changes by up to 50 % depending on the SSP scenario, in particular due to different sulfur emissions. We conduct sensitivity simulations with and without CO2 inhibition of isoprene emissions that is highly uncertain, which results in a factor of two differences in the predicted IEPOX-SOA global burden, especially for the high-CO2 scenarios (SSP3-7.0 and SSP5-8.5). Aerosol pH also plays a critical role in the IEPOX-SOA formation rate, requiring accurate calculation of aerosol pH in chemistry models. On the other hand, isoprene SOA calculated with the VBS scheme predicts nearly constant SOA yield from isoprene emission across all SSP scenarios, as a result, it mostly follows isoprene emissions regardless of region and scenario. This is because the VBS scheme does not consider heterogeneous chemistry, in other words, there is no dependency on aerosol properties. The discrepancy between the explicit mechanism and VBS parameterization in this study is likely to occur for other SOA components as well, which may also have dependencies that cannot be captured by VBS parameterizations. This study highlights the need for more explicit chemistry, or for parameterizations that capture the dependence on key physico-chemical drivers when predicting SOA concentrations for climate studies.

scholarly journals The effects of morphology, mobility size, and secondary organic aerosol (SOA) material coating on the ice nucleation activity of black carbon in the cirrus regime

2020 ◽  
Vol 20 (22) ◽  
pp. 13957-13984
Author(s):  
Cuiqi Zhang ◽  
Yue Zhang ◽  
Martin J. Wolf ◽  
Leonid Nichman ◽  
Chuanyang Shen ◽  
...  
Keyword(s):  
Black Carbon ◽  
State Transition ◽  
Phase State ◽  
Secondary Organic Aerosol ◽  
Global Climate ◽  
Surface Oxidation ◽  
Organic Aerosol ◽  
Ice Nucleation ◽  
Supersaturation Ratio ◽  
Homogeneous Freezing

Abstract. There is evidence that black carbon (BC) particles may affect cirrus formation and, hence, global climate by acting as potential ice nucleating particles (INPs) in the troposphere. Nevertheless, the ice nucleation (IN) ability of bare BC and BC coated with secondary organic aerosol (SOA) material remains uncertain. We have systematically examined the IN ability of 100–400 nm size-selected BC particles with different morphologies and different SOA coatings representative of anthropogenic (toluene and n-dodecane) and biogenic (β-caryophyllene) sources in the cirrus regime (−46 to −38 ∘C). Several BC proxies were selected to represent different particle morphologies and oxidation levels. Atmospheric aging was further replicated with the exposure of SOA-coated BC to OH. The results demonstrate that the 400 nm hydrophobic BC types nucleate ice only at or near the homogeneous freezing threshold. Ice formation at cirrus temperatures below homogeneous freezing thresholds, as opposed to purely homogeneous freezing, was observed to occur for some BC types between 100 and 200 nm within the investigated temperature range. More fractal BC particles did not consistently act as superior INPs over more spherical ones. SOA coating generated by oxidizing β-caryophyllene with O3 did not seem to affect BC IN ability, probably due to an SOA-phase state transition. However, SOA coatings generated from OH oxidation of various organic species did exhibit higher IN-onset supersaturation ratio with respect to ice (SSi), compared with bare BC particles, with the toluene-SOA coating showing an increase in SSi of 0.1–0.15 while still below the homogeneous freezing threshold. Slightly oxidized toluene SOA coating seemed to have a stronger deactivation effect on BC IN ability than highly oxidized toluene SOA, which might be caused by oligomer formation and the phase state transition of toluene SOA under different oxidation levels. n-dodecane and β-caryophyllene-derived SOA-coated BC only froze in the homogeneous regime. We attribute the inhibition of IN ability to the filling of the pores on the BC surface by the SOA material coating. OH exposure levels of n-dodecane and β-caryophyllene SOA coating experiments, from an equivalent atmospheric exposure time from 10 to 90 d, did not render significant differences in the IN potential. Our study of selected BC types and sizes suggests that increases in diameter, compactness, and/or surface oxidation of BC particles lead to more efficient IN via the pore condensation freezing (PCF) pathway, and that coatings of common SOA materials can inhibit the formation of ice.

scholarly journals Synergistic O3 + OH oxidation pathway to extremely low-volatility dimers revealed in β-pinene secondary organic aerosol

2018 ◽  
Vol 115 (33) ◽  
pp. 8301-8306 ◽  
Author(s):  
Christopher M. Kenseth ◽  
Yuanlong Huang ◽  
Ran Zhao ◽  
Nathan F. Dalleska ◽  
J. Caleb Hethcox ◽  
...  
Keyword(s):  
Climate Models ◽  
Secondary Organic Aerosol ◽  
Global Climate ◽  
Organic Aerosol ◽  
Current Treatment ◽  
Global Climate Models ◽  
Sum Of Products ◽  
Regional Air Quality ◽  
Unidentified Source ◽  
Phase Chemistry

Dimeric compounds contribute significantly to the formation and growth of atmospheric secondary organic aerosol (SOA) derived from monoterpene oxidation. However, the mechanisms of dimer production, in particular the relevance of gas- vs. particle-phase chemistry, remain unclear. Here, through a combination of mass spectrometric, chromatographic, and synthetic techniques, we identify a suite of dimeric compounds (C15–19H24–32O5–11) formed from concerted O3 and OH oxidation of β-pinene (i.e., accretion of O3- and OH-derived products/intermediates). These dimers account for an appreciable fraction (5.9–25.4%) of the β-pinene SOA mass and are designated as extremely low-volatility organic compounds. Certain dimers, characterized as covalent dimer esters, are conclusively shown to form through heterogeneous chemistry, while evidence of dimer production via gas-phase reactions is also presented. The formation of dimers through synergistic O3 + OH oxidation represents a potentially significant, heretofore-unidentified source of low-volatility monoterpene SOA. This reactivity also suggests that the current treatment of SOA formation as a sum of products originating from the isolated oxidation of individual precursors fails to accurately reflect the complexity of oxidation pathways at play in the real atmosphere. Accounting for the role of synergistic oxidation in ambient SOA formation could help to resolve the discrepancy between the measured atmospheric burden of SOA and that predicted by regional air quality and global climate models.

scholarly journals A long-term (2005–2016) dataset of integrated land–atmosphere interaction observations on the Tibetan Plateau

2020 ◽  
Author(s):  
Yaoming Ma ◽  
Zeyong Hu ◽  
Zhipeng Xie ◽  
Weiqiang Ma ◽  
Binbin Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Tibetan Plateau ◽  
Soil Temperature ◽  
Water Content ◽  
Global Climate ◽  
High Elevation ◽  
Observation System ◽  
The Tibetan Plateau ◽  
Atmosphere Interaction

Abstract. The Tibetan Plateau (TP) plays a critical role in influencing regional and global climate, via both thermal and dynamical mechanisms. Meanwhile, as the largest high-elevation part of the cryosphere outside the polar regions, with vast areas of mountain glaciers, permafrost and seasonally frozen ground, the TP is characterized as an area sensitive to global climate change. However, meteorological stations are sparely and biased distributed over the TP, owing to the harsh environmental conditions, high elevations, complex topography, and heterogeneous surfaces. Moreover, due to the weak representative of the stations, atmospheric conditions and the local land-atmosphere coupled system over the TP as well as its effects on surrounding regions are poorly quantified. This paper presents a long-term (2005–2016) dataset of hourly land-atmosphere interaction observations from an integrated high-elevation, cold region observation network, which is composed of six field observation and research platforms on the TP. In-situ observations, at the hourly resolution, consisting of measurements of micrometeorology, surface radiation, eddy covariance (EC), and soil temperature and soil water content profiles. Meteorological data were monitored by automatic weather station (AWS) or a planetary boundary layer (PBL) observation system composed of multiple meteorological element instruments. Multilayer soil hydrothermal data were recorded to capture vertical variations in soil temperature and water content and to study the freeze-thaw processes. In addition, to capture the high-frequency vertical exchanges of energy, momentum, water vapor and carbon dioxide within the atmospheric boundary layer, an EC system consisting of an ultrasonic anemometer and an infrared gas analyzer was installed at each station. The release of these continuous and long-term datasets with hourly time resolution represents a leap forward in scientific data sharing over the TP, and it has been partially used in the past to assist in understanding key land surface processes. This dataset is described here comprehensively for facilitating a broader multidisciplinary community by enabling the evaluation and development of existing or new remote sensing algorithms as well as geophysical models for climate research and forecasting. The whole datasets are freely available at Science Data Bank (http://www.dx.doi.org/10.11922/sciencedb.00103, Ma et al., 2020) and, additionally at the National Tibetan Plateau Data Center (https://data.tpdc.ac.cn/en/data/b9ab35b2-81fb-4330-925f-4d9860ac47c3/).

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