Displays

At the industrial revolution (1750-1800), the population of the earth was around 1 Billion and less than 5% of population lived in urban areas. In 1950, when the population reached about 2.9 billion, there were two megacities New York/Newark and Tokyo. In 2020, the earth’s population is around 7.8 Billion, more than 50% live in urban areas and there are now approximately 38 around the world. Since 2007, more than 50% of the population live in urban areas and the earth’s population has now reached 7.8 Billion. Anthropogenic activity to sustain and feed MPC is now one of the most important sources of pollution, modifying atmospheric chemistry, air quality and climate.  To assess the impact of MPC emissions locally and regionally requires knowledge of the transport and transformation of the MPC plumes. The EMeRGe project was proposed to address this need and investigate the transport and transformation of the chemical composition of MPC plumes. Secondary objectives include the improvement of our understanding of the impact of biomass burning, which mixes with the plumes from MPC. EMeRGe selected European and Asian MPC as targets, where the regulations on emissions are significantly different.

EMeRGe assumes that the nature of the local emissions, the meteorology and photochemistry/chemistry determines the transport and transformation of the plumes from MPCs. To test this hypothesis, the following scientific questions are addressed:
a) which transport and dispersion processes dominate the MPC outflows in Europe and Asia during the selected measurement periods;
b) which oxidation or other processes determine the chemical transformation of MPC emissions;
c) what are the regional impacts of the emission by the selected European and Asian MPCs;
d) what is the relevance of emission from European and Asian MPCs for radiative forcing and climate change;
e) do our chemical models adequately simulate of transport and transformation processes of European and Asian MPC outflows.

An integrating focus of EMeRGe were the measurement campaigns exploiting the capabilities of the German HALO research were undertaken during EMeRGe, which investigated the outflow from: i) European MPCs in July 2017; ii) MPCs in East and South East Asia during March and April 2018. In addition to the HALO aircraft measurements, the EMeRGe International scientists contributed studies of the measurement from instrumentation from ground based, airborne and satellite platforms. For example in EMeRGe in Europe the UK NERC FAAM (https://nerc.ukri.org/research/sites/facilities/aircraft/) "ERA - CNR - ISAFOM" (https://www.eufar.net/aircrafts/44) were deployed to make measurements around London and Rome respectively. In EMeRGe in Asia, measurement were made ground based and Lidar measurements were made by EMeRGe partners from Taiwan, Japan, the Philippines, Thailand and China. EMeRGe benefited from the support by iCACGP (international Commission on Atmospheric Chemistry and Global Pollution). This presentation will provide an overview of the objectives, the planning, the measurements and some highlights from the EMeRGe HALO campaigns.

How to cite: Burrows, J. P., Andrés Hernández, M. D., Vrekoussis, M., Chou, C. C.-K., Wang, P. K., Schlager, H., Ziereis, H., Zahn, A., Schneider, J., Pfeilsticker, K., Platt, U., and Kanaya, Y.: EMeRGe - the Effect of Megacities on the transport and transformation of pollutants on the Regional and Global scales , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19474, https://doi.org/10.5194/egusphere-egu2020-19474, 2020.

Taiwan is a subtropical island with an area of only about 36,000 km² and yet packed with high density of mountains. There are 268 peaks that are taller than 3000 m in elevation and, as a result, the mountains are extremely rugged. Such rugged orography will certainly have great influence on the local circulation and consequently impact on the transport of air pollutants. It is thus necessary to understand the impact of the orography on air flow before we can interpret the measured data during the EMeRGe-Asia campaign in March-April 2018 correctly.

For the above purpose, we performed high resolution numerical simulations of the flow around Taiwan region for two cases using the Weather Research and Forecast (WRF) model. The first one is a highly stagnant case where Taiwan was under the influence of a high pressure system occurring on 10 November 2018. Two horizontal resolutions are used: 1 km and 2 km, both show very similar flow and cloud patterns as revealed by satellite images of the day. Detailed analysis of the simulated results including the flow pattern and isentropic analysis will be shown to illustrate that low level pollutants can be transported upward to at least 1 km altitude even under such calm weather.

The second one is the 20 March 2018 case which occurred during the EMeRGe-Asia campaign. Unlike the above stagnant case, this was a more turbulent situation when a typhoon was approaching from the east and a southerly flow carried air pollutants from SE Asia. The 1 km resolution simulation shows good match with satellite observation. The simulation results show a substantial concentration of VOC at ~ 3000 m altitude near Taiwan whereas the VOC was very low near the surface. The model reproduces this feature well and hence it appears that the model’s predictions are credible. More detailed analyses are being performed and comparison of the results with combined ground and aircraft observations to illustrate the impact of the orography on the transport of pollutants.  

How to cite: Wang, P. K. and Lin, C.-Y.: The Impact of Taiwan’s Rugged Orography on Air Pollutant Transport and the Numerical Modeling of 20 March 2018 Case, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19122, https://doi.org/10.5194/egusphere-egu2020-19122, 2020.

EMeRGe (Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales) aims to investigate the impact of MPC emissions on air pollution and chemical processing at local, regional and hemispheric scales by making dedicated airborne measurements using the German research aircraft HALO. Transects and vertical profiling for diverse MPCs (e.g. Rome, London, Taipei, Manila) were performed to determine the composition and transformation of various pollution plumes in Europe and Asia.

To characterize air masses we evaluate different volatile organic compounds (VOCs), measured by a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS), with different or similar sources and different lifetimes. We use the specific tracer acetonitrile to identify air masses influenced by biomass burning (BB), the aromatic compound benzene to tag anthropogenic pollution plumes (e.g. from traffic or industry) and short-lived isoprene as indicator for fresh biogenic influences. Back trajectories based on FLEXTRA (FLEXible TRAjectory model) are used to determine potential source regions of BB affected air and anthropogenic pollution plumes.

Results show that in Europe only minor BB influenced air masses were sampled. However, in Southern France fresh BB close to the source was detected. In contrast to Europe, numerous plumes affected by BB were identified in Asia originating mostly from Southeast Asia.

Air masses with enhanced concentrations in benzene and low concentrations in acetonitrile, indicating anthropogenic pollution, were sampled in Europe over the Po-Valley, Rome, Barcelona and the English Channel. In Asia, plumes were identified along the west coast of Taiwan, the East China Sea and Manila originating from local sources as well as transported from Mainland China.

Significant fresh biogenic influence was found in Europe, as the measurements were performed mostly in summer over land in contrast to Asia were just a minor influence was detected.

How to cite: Förster, E., Bönisch, H., Neumaier, M., Obersteiner, F., Lichtenstern, M., Hilboll, A., Kalisz Hedegaard, A. B., Vrekoussis, M., and Zahn, A.: Air mass characterization based on VOC measurements downstream of European and Asian Major Population Centers (MPC) during the research aircraft campaign EMeRGe (2017/2018), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16820, https://doi.org/10.5194/egusphere-egu2020-16820, 2020.

VOC (volatile organic compounds) play a critical role in the chemistry of the atmosphere. The formation of many important secondary pollutants in the atmosphere, such as ozone, peroxides, aldehydes, and peroxyacyl nitrates and secondary organic particulate matter depends critically on the availability of VOC as their precursors. Many of them have strong direct adverse effects on our environment. The assessment of the impact of VOC on the atmosphere can be significantly improved by measuring their stable carbon isotope ratios. The isotopic composition of compounds emitted by natural or anthropogenic activities vary for emissions from different sources. In almost all atmospheric processes, e.g. chemical reactions, photolytic processes, transport and dilution, diffusion, and phase transitions, the isotopic ratio in VOC is altered. Studying the isotope ratios of both precursors and products makes it possible to distinguish between freshly emitted VOC and photochemically processed compounds, to increase our knowledge of transport versus chemistry, to study the ultimate fate of oxidation products, and to help assess the impact of emissions, e.g. from large population centres (MPCs), on local, regional and even global pollution.
The automated high volume air sampling system MIRAH has been deployed during several missions with the German High Altitude – Long-range research aircraft (HALO). Here we focus on the campaigns EMeRGe-EU and -ASIA (Effect of Megacities on the transport and transformation of pollutants on the Regional and Global scales). The objectives were to measure the pollution emitted, transported and transformed from the MPCs London, BeNeLux, Rhine-Ruhr and Po Valley for the European Part. The second part of EMeRGe was conducted from Taiwan with the goal to investigate the pollution outflow from Asian MPCs such as Taipei, Hongkong, Shanghai, Beijing, Manila, Seoul and Tokio. In both parts a key experiment was the identification of the source of the air masses by collecting whole air samples on ground prior and during particular flights in specific metropolitan regions. On 7 flights in Europe and 12 flights in Asia, mostly below 6 km altitude, more than 140 air samples were collected on HALO during each campaign, and additional 46 samples at specific ground sides. The whole air samples were analysed for mixing ratios and stable carbon isotope ratios of selected aldehydes, ketones, alcohols, and aromatics. This allowed investigating air masses of different origin, characteristic, and atmospheric processing. In this presentation we will give an overview of the data and show exemplary results.

This work was supported by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG Priority Program SPP 1294) under grant-No. KR3861/1-1.

How to cite: Krebsbach, M. and Koppmann, R.: Stable Carbon Isotope Ratios in Atmospheric VOC during the EMeRGe-EU and ASIA campaigns, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7597, https://doi.org/10.5194/egusphere-egu2020-7597, 2020.

Since peroxy radicals are closely involved in a number of tropospheric chemical processes like O₃ budget, hydrocarbon oxidation and acid formation, the accurate measurement of these radicals can provide essential information to improve our understanding of processing and transformation of polluted outflows from megacities and Major Population Centres (MPCs).

Airborne measurements of the total sum of peroxy radicals, RO₂*  = HO₂ + ∑ RO₂, where R is an organic group, were conducted in Europe in summer 2017 and in East Asia in spring 2018 within the EMeRGe (Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales) project by using the PeRCEAS instrument (Peroxy Radical Chemical Enhancement and Absorption Spectrometer), on board of the HALO research aircraft (www.halo.dlr.de).

Over the course of both measurement campaigns different MPC outflows were investigated including among others, London, Rome, Manila and Taipei. Polluted air masses of different origin and composition were probed. Overall the peroxy radical mixing ratios were of the same order of magnitude in the air masses probed in Europe and in East Asia. The variations in the photochemical activity were studied by taking into account simultaneous observations of radical precursors and photolysis rates, while applying known oxidation mechanisms. Radical precursors, photolysis rates and aerosol load were generally higher in Asia, which might indicate higher radical loss reactions on the aerosol surface than in Europe. Moreover this study shows a clear deviation in the photostationary state for MPC outflows close to the emission sources. Based on this information, this presentation will focus on the actual understanding of the photochemical processing in the probed air masses.

How to cite: George, M., Andrés Hernández, M. D., Liu, Y., Nenakhov, V., Philip Burrows, J., Bohn, B., Förster, E., Zahn, A., Schlager, H., Ziereis, H., Schreiner, B., and Pfeilsticker, K.: Investigation of the photochemical activity in different MPC outflows during EMeRGe, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18635, https://doi.org/10.5194/egusphere-egu2020-18635, 2020.

Middle and long-term  photo-chemical effects of local and regional pollution are not well quantified and are an area of active study. NO_x (here defined as NO, NO₂, and HONO) is a regional pollutant, which influences atmospheric oxidation capacity and ozone formation. Airborne measurements of atmospheric trace gases from the HALO (High Altitude Long Range) aircraft, particularly of NO, NO₂, and HONO were performed as part of the EMeRGe (Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales) campaign over continental Europe and southeast Asia in July 2017 and April 2018, respectively. NO (and NO_Y), O₃, and the photolysis frequencies of NO₂ and HONO were measured in-situ. NO₂ and HONO were inferred from Limb measurements of the mini-DOAS (Differential Optical Absorption Spectroscopy) instrument, using the novel scaling method (Hüneke et al., 2017). These measurements were compared with simulations of the MECO/EMAC models. In relatively polluted air-masses in the boundary layer and free troposphere, HONO measured in excess of model predictions (and previous measurements) suggests an in-situ formation and a significant source of OH as well as a pathway for re-noxification. Aerosol composition simultaneously measured  by the C-Tof-AMS instrument may reveal potential reaction mechanisms to explain the discrepancy. 

How to cite: Schreiner, B., Pfeilsticker, K., Kluge, F., Rotermund, M., Zahn, A., Ziereis, H., Bohn, B., Schneider, J., Kaiser, K., Pozzer, A., and Mertens, M.: Aircraft measurements of nitrous acid in excess of model predictions in the boundary layer and free troposphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13607, https://doi.org/10.5194/egusphere-egu2020-13607, 2020.

Today, the majority of humanity lives in urban areas. Accordingly, major population centers are a significant source of a multitude of atmospheric emissions from human activity such as traffic, heating, industry or power generation. Pollutants directly impact the local inhabitant's health, but are also transported to neighbouring areas, undergo chemical evolution and can have an impact on climate. To understand and assess effective measures for reducing the effects, it is important to determine the source locations and strengths as well as relevant chemical processes.

Aircraft-based measurements can cover the gap between long-term ground-based and globe-covering satellite instruments with its high temporal and spatial coverage during flight time. Remote sensing methods in particular allow a fast and wide-spread probing of atmospheric trace gas distributions. Within this context, the HAIDI (Heidelberg Airborne Imaging DOAS Instrument) instrument was designed to provide data of extremely high temporal and spatial resolution (40m x 40m at 1.5 km flight altitude, 266m x 266m at 10 km flight altitude, at 10 ms temporal resolution) in 2D and 3D during overflight.

During the EMeRGe (Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales) missions HAIDI was part of the comprehensive set of measurement equipment installed on the research airplane HALO (High Altitude and LOng range re-search aircraft) of the DLR (German Aerospace Center). The EMeRGe missions targeted the emission outflows of megacities to investigate their compositions and the atmospheric impact of urban pollution. One mission part was conducted in Europe (July 2017) and aimed at areas around Paris, London, the Po area, Madrid and the Benelux area. For contrast, the second mission part was based in Taiwan (March 2018) and investigated Taiwan cities, Bangkok, Manila, Japanese cities and China outflow.

HAIDI derived a number of trace gases such as NO2, SO2, BrO and HCHO. Due to large concentrations present, for NO2 and SO2 in particular it was possible to obtain high-resolution 2D data of megacity areas and plumes of megacities, powerplants and ships and estimate their emissions. We will present results of the HAIDI measurements during the EMeRGe mission.

How to cite: Bigge, K., Pöhler, D., Frieß, U., and Platt, U.: Aircraft-based 2- and 3D Trace Gas Measurements with HAIDI (Heidelberg Airborne Imaging DOAS Instrument) - Results of the EMeRGe Missions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1093, https://doi.org/10.5194/egusphere-egu2020-1093, 2020.

NO_x (the sum of NO + NO₂) is emitted during most combustion processes. NO₂ is a well-known air pollutant detrimental to human health, critical in the formation of tropospheric ozone and its concentration is regulated in many cities. London is a megacity which often finds itself in breach of these air quality regulations. Emission inventories are used in air quality forecast models to predict current and future air pollution levels and to guide abatement strategy. The National Atmospheric Emissions Inventory (NAEI) has been shown to underestimate NO_x emission in London (Lee et al. 2012, Vaughan et al. 2016). Top down measurements allow assessment of emissions help understand the difference between measurement and model.

During March – June 2017 NO_x emissions were measured using the eddy covariance method sampling from a height of 180 m at the British Telecom (BT) tower in Central London. In July of 2017 measurements of NO_x by the UK’s Facility for Airborne Atmospheric Measurement (FAAM) were made as a part of the Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales (EMeRGe). A mass balance approach (after O’Shea et al. 2014 and Pitt et al. 2019) has been applied to these measurements producing a measurement of bulk emission of NO_x from Greater London and surrounding areas.

Through comparison of these measurements with the NAEI we present an exploration of NO_x emission from London and assess how this is captured in the emissions inventory.

Lee et al., Environmental Science & Technology, 2015, 49, 1025-1034

Vaughan et al., Faraday Discussions, 2016, 189, 455-472

O’Shea et al., J. Geophys. Res. Atmos., 2014, 119, 4940–4952

Pitt et al., Atmos. Chem. Phys., 2019, 19, 8931-8945

How to cite: Drysdale, W., Vaughan, A., Squires, F., Nelson, B., Pitt, J., Metzger, S., Durden, D., Pingintha-Durden, N., Grimmond, S., Purvis, R., and Lee, J.: Exploring NOx Emission from the Ground and the Air in London, UK, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17372, https://doi.org/10.5194/egusphere-egu2020-17372, 2020.

Megacities worldwide are suffering from elevated air pollution due, e.g., to continuously increasing urbanization, and a sizeable amount of the population in such areas is exposed to particulate matter (PM) concentrations exceeding the WHO limits. Huge efforts are therefore undertaken to characterize the air pollution situation and to reduce or mitigate the impact on the population and the environment. Modern instrumentation allows for a quantitative determination of aerosol concentration and composition with high time resolution (minutes to hours), and subsequent source apportionment.

We collected PM₁₀ and PM_2.5 aerosols alternatingly with an online X-ray fluorescence (XRF) spectrometer in the cities of New Delhi (India) in 2019, Beijing (China) in 2017, and Krakow (Poland) in 2018, with time resolutions from 30 to 120 min, and in London (UK) in 2012 with 3-stage rotating drum impactors and subsequent offline SR-XRF analysis. Campaigns lasted for two to seven weeks in fall and winter. Elements from Al to Bi were analyzed in near-real time, except for London.

Our results show that some of the cities experience episodic extreme events, whereas extremely high elemental concentrations are chronic in others. Toxic metals are shown to be strongly location-dependent, and may occur in extreme plumes. Meteorological conditions also play an important role and will be discussed. The regional influence of fine PM, in comparison to the more local origin of coarse PM will be evaluated. The differences among the four cities, with substantially higher concentrations in the Asian cities than the European ones will be discussed. Highly time-resolved size-segregated sampling allowed for a rough classification of elements into five groups and will be described in detail. We demonstrate that the use of size information on toxic elements, diurnal patterns of targeted emissions, and local vs. regional effects are advantageous for formulating effective environmental policies to protect public health.

How to cite: Furger, M., Rai, P., Slowik, J. G., Tripathi, S. N., Cao, J., Necki, J., Visser, S., Prévôt, A. S. H., and Baltensperger, U.: Hourly elemental concentrations in ambient aerosols in four cities in Asia and Europe – comparison and source apportionment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6595, https://doi.org/10.5194/egusphere-egu2020-6595, 2020.

In wintertime, high background concentrations of atmospheric fine particulate matter (PM_2.5) are commonly observed in the metropolitan area of Santiago, Chile. Although the frequency of alert events has been decreasing in the recent years, two short-lived peak events reaching up to 600µg/m³ for a few hours were observed in the city on June 18^th and June 26^th 2016, triggering emergency measures for the next day.

The observed meteorological conditions at the time of these peaks are not unusual. In addition, a high-resolution meteorology and chemistry-transport simulation with the WRF meteorological model and the CHIMERE chemistry-transport model reproduces fairly well the meteorology and levels of PM for June 2016, except for those two particular events that are not captured by the model. The combination of these elements leads to the conclusion that sporadic strong emissions are at play.

The analysis of recorded concentration ratios of PM_2.5, NOx and CO points to a specific source, departing significantly from the average signal for the season. Based on the literature and HTAP emission ratios, usual sources of PM such as traffic, residential heating and industry can be ruled out. The temporal correlation of the events with soccer games of the Chilean team and the recorded chemical footprint lead to conclude to the dominant contribution of massive barbecue cooking at the peak times.

Following the source identification via surface stations analysis, the next question was to quantify the potential transport and impact of such pollution peaks in the Santiago Metropolitan area. An additional source term was added in the chemistry-transport simulation, and maps of PM changes were analyzed. For both events, the same region in the Southwest of Santiago was impacted by the plume.

A natural continuation of this work is the study through modeling of the dispersion patterns of polluted plumes outside of the Santiago basin on a longer time scale. In particular, significant deposition of light-absorbing particles has been measured on glaciers near the capital city, without a clear identification of their source or the underlying processes of transport.

How to cite: Lapere, R., Menut, L., Mailler, S., and Huneeus, N.: Combining air quality network data and chemistry-transport modeling for the attribution of extreme pollution events: a case study of Santiago, Chile, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3596, https://doi.org/10.5194/egusphere-egu2020-3596, 2020.

In this presentation, we will discuss the top down emission estimates of SO₂ and volatile organic compounds using mass spectrometers integrated on a research aircraft with a fast-meteorological sensor. The study area is four coal power plants, one steel mill, and one petrochemical industrial facility, located in the Tae-ahn Peninsular in South Korea 50 km away from the southern tip of the Seoul Metropolitan Area. We conducted 20 research flights to closely monitor emissions from each facility.  We will present detailed analysis of instantaneous emission rates to verify emission inventories to proceed their impacts to regional air quality, particularly towards the Seoul Metropolitan Area with a population of 25 millions, using a semi-Lagrangian photochemical box model.

How to cite: Kim, S., Mielnik, A., Wong, G., Sarkar, C., and Guenther, A.: The emission and photochemistry of a large industrial facilities near megacities - a case study in South Korea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8430, https://doi.org/10.5194/egusphere-egu2020-8430, 2020.

We carried out 14 days of Car MAX-DOAS experiments on the 6th Ring Rd of Beijing in January, September and October, 2014. The tropospheric vertical column densities (VCD) of NO₂ are retrieved and used to estimate the emissions of NO_x. The offline LAPS-WRF-CMAQ model system is used to simulate wind fields by assimilation of observational data and calculate the NO₂ to NO_x concentration ratios. The NO_X emissions in Beijing for different seasons derived from Car MAX-DOAS measurements are compared with the multi-resolution emission inventory in China for 2012 (MEIC 2012), and impacts of wind field on estimated emissions and its uncertainties are also investigated. Results show that the NO₂ VCD is higher in January than other two months and it is typically larger at the southern parts of the 6th Ring Road than the northern parts of it. Wind field has obvious impacts on the spatial distribution of NO₂ VCD, and the mean NO₂ VCD with south wind at most sampling points along the 6th Ring Rd is higher than north wind. The journey-to-journey variation pattern of estimated NO_X emissions rates (E_NOX) is consistent with that of the NO₂ VCD, and E_NOX is mainly determined by the NO2 VCD. In addition, the journey-to-journey E_NOX in the same month is different and it is affected by wind speed, the ratio of NO₂ and NOx concentration and the decay rate of NO_X from the emission sources to measured positions under different meteorological condition. The E_NOX ranges between 6.46×10²⁵ and 50.05×10²⁵ molec s^-1. The averaged E_NOX during every journey in January, September and October are respectively 35.87×10²⁵, 20.34×10²⁵, 8.96×10²⁵ molec s^-1. The estimated E_NOX after removing the simulated error of wind speed and observed deviation of NO₂ VCD are found to be mostly closer to the MEIC 2012, but sometimes E_NOX is lower or higher and it indicates that the MEIC 2012 might be overestimate or underestimate the true emissions. The estimated E_NOX on January 27 and September 19 are obviously higher than other journeys in the same month because the mean NO₂ VCD and Leighton ratio during these two periods are larger, and corresponding wind speeds are smaller. Additionally, because south wind may affect the spatial distribution of mean NO₂ VCD in Beijing which is downwind of south-central regions of Hebei province with high source emission rates, the uncertainty of the estimated E_NOX with south wind will be increased.

How to cite: Cheng, X.: Quantification of NOX Emissions Based on Car MAX-DOAS Measurements over Beijing and Impacts of Wind Field, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12459, https://doi.org/10.5194/egusphere-egu2020-12459, 2020.

Delhi is one of the world’s most polluted city and experiences very high levels of particulate matter throughout the year. It significantly affects radiative forcing, increases mortality, and causes other deleterious effects on human health. Generally, there is a lack of consensus on the dominant sources of organic aerosol driving these high aerosol concentrations. In particular, there is a need to elucidate the relative importance of primary vs. secondary sources and formation mechanisms of secondary aerosols. In order to answer questions pertaining to the sources, formation mechanisms, and atmospheric transformations of organic aerosol, we deployed for the first time in Delhi, the recently developed extractive electrospray ionization long-time-of-flight mass spectrometer (EESI-TOF) in Delhi. This was deployed along with a high-resolution long-time-of-flight aerosol mass spectrometer (AMS), and a Chemical Ionisation Mass Spectrometer fitted with a Filter Inlet for Gases and AEROsols (FIGAERO-CIMS). These measurements were further supported by measurements of black carbon and gaseous species such as CO, NO_x etc.

The EESI-TOF provides in real-time information on the chemical composition at the near-molecular level without thermal desorption and fragmentation (Lopez-Hilfiker et al., 2019). It was operated in Delhi from December to February 2019. Measurements by the AMS showed persisting high levels of particulate matter. We attributed the relative contributions of different sources to total non-refractory PM mass by performing source apportionment analysis by means of positive matrix factorization (PMF). A strong day-night variability was clearly seen in all the AMS species. High levels of secondary sources during daytime e.g., low-volatility oxygenated organic aerosol (LVOOA) and an increase of factors associated with primary sources i.e., hydrocarbon-like organic aerosol (HOA) and aerosol from solid fuel combustion (SFC) during morning and evening hours was observed. A similar trend as for the primary aerosol was seen for the semi-volatile oxygenated organic aerosol (SVOOA) mainly due to increased temperature during daytime which may leads to evaporation of semi-volatile species. A unique feature observed was a significant contribution of chloride to the non-refractory (NR) PM_2.5 mass. On average, chloride contributed 18-20% to total NR-mass. Similar trends have also been seen in a recent study (Gani et al., 2018). The effect of these high chlorine concentrations during the night and early morning on atmospheric chemistry as well as on secondary organic aerosol formation will be presented.

How to cite: kumar, V., Bell, D., Haslett, S., Bhattu, D., Tong, Y., Giannoukos, S., Mishra, S., Singh, A., Vats, P., Kumar, R. S., Baltensperger, U., Ganguly, D., Rastogi, N., Mohr, C., Tripathi, S. N., Prevot, A. S. H., and Slowik, J. G.: Characterization and Source Apportionment of Organic Aerosols in Delhi, India, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21005, https://doi.org/10.5194/egusphere-egu2020-21005, 2020.

Black and brown carbon (BC and BrC) are potent climate forcing agents with pronounced effects on global climate and tropospheric chemistry. Given the large heterogeneities in BC emission inventories from India and the paucity of studies on BrC characteristics, field-based measurements of BC and BrC sources and optical properties are essential to understand their impacts on regional climate. To address this issue, we report the first ground-based measurements of BC and BrC from a rural location in the highly polluted eastern Indo-Gangetic Plain (IGP) during May-November 2018 encompassing the photochemistry-dominated summer (May-June) and regional biomass burning (BB)-dominated post-monsoon (October-November) periods. A 7-wavelength Aethalometer was used for time-resolved measurements of BC mass and was supplemented by UV-Vis and fluorescence measurements of time-integrated (24 h) aqueous and organic BrC fractions, and measurements of OC, EC, WSOC, and ionic species.
The daily averaged BC increased 4 times during the BB regime (12.3 ± 3.9 μg m^-3) as compared to summer (4.2 ± 0.8 μg m^-3), while aqueous and organic BrC fractions demonstrated light absorption (babs_365) enhancements of 3-5 times during BB. For aqueous BrC, the averaged AE of 5.9-6.2 and a prominent fluorescence peak at ~420 nm suggested the presence of humic-like substances (HULIS), potentially from secondary photochemical formation during summer and primary emission during BB periods. Fluorescence and UV-Vis spectra also indicated the presence of nitroaromatic compounds, presumably from OH oxidation in summer and nighttime NO3- oxidation in the presence of enhanced NOx and precursor emission during BB. The latter was supported by the strong association between water-soluble organic carbon (WSOC; a proxy for aqueous BrC) and aerosol NO₃^- (r=0.70, p<0.05). During BB, the fraction of water-insoluble (i.e., organic) BrC increased from 41% at 330 nm to 59 % at 550 nm while during the photochemistry-dominated summer period, the water-insoluble BrC fraction decreased from 73% at 400 nm to 41% at 530 nm, possibly due to photobleaching in the presence of OH. The BB-related BrC aerosol was also characterized by higher aromaticity and increased molecular weights of organic components as evidenced by mass absorption efficiency (MAE) ratios (MAE₂₅₀/MAE₃₆₅). Overall, this study established that BrC is a significant component of light-absorbing aerosol in the eastern IGP and that BrC optical properties may vary significantly in this region depending on the relative dominance of aerosol emissions and atmospheric processes.

How to cite: Rana, A., Dey, S., and Sarkar, S.: Optical properties of atmospheric brown carbon (BrC) for photochemical and biomass burning-dominated aerosol regimes in India., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-611, https://doi.org/10.5194/egusphere-egu2020-611, 2020.

In springtime happens to be the biomass burning season in Indochina. Under favor weather conditions, the products of biomass burning pollutants could be transported easily to Taiwan and even East Asia. Actually, the complex interactions of these air pollutants and aerosols features in the boundary layer and aloft have resulted in complex characteristics of air pollutants and aerosols distributions in the lower troposphere. The project “Effect of Megacities on the transport and transformation of pollutants on the Regional and Global scales (EMeRGe)” aims to improve our knowledge and prediction of the transport and transformation patterns of European and Asian megacities pollutant outflows. During the EMeRGe campaign in Asia, the composition of the plumes of pollution entering and leaving Asia measured by the new High Altitude and LOng Range (HALO) aircraft research platform. The HALO aircraft performing optimized transects and vertical profiling in Asia during 12 March and 7 April in 2018. To identify the transportation of biomass burning products, a high resolution (9 km) numerical study by Weather Research Forecast coupled with chemistry model (WRF-Chem) was performed during the campaigns. The long-range transport of biomass burning organic aerosol to Taiwan measured by HALO could be more than 2 ug/m3 at the elevation of 2500 m on 20 March, 2018. Model performances and results will discuss in this meeting. Overall, this series of studies significantly fill the gap of our understanding on air pollutants transformation and transport to Taiwan and East Asia, and show the potential directions of future studies.

How to cite: Lin, C., Chen, W., sheng, Y., Chen, W.-M., and Chien, Y.-Y.: Modeling of Southeast Asia biomass burning pollutants to Taiwan during EMeRGe campaigns in Asia, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9426, https://doi.org/10.5194/egusphere-egu2020-9426, 2020.

        Sentinel-5 Precursor (S5P) is a new generation environmental satellite, and provides trace gases concentrations along with cloud and aerosol information for global coverage. In this study, we focus on a regional scale nitrogen oxide (NO_x) which is not only mainly air pollutant but also the precursors of secondary aerosol and ozone. However, the atmospheric NOx is primary in the form of Nitrogen dioxide (NO₂). To understand the chemical properties and air pollution of NO₂ from S5P in Taiwan, this study accesses the tropospheric NO₂ which is retrieved from the TROPOMI onboard S5P, in conjunction with in-situ surface NO₂ concentration observation from Environmental Protection Administration (EPA) of Taiwan. The temporal period is from June 2018 to May 2019, and surface observation is collocated with daily revisit of S5P spatiotemporally. The data are analyzed in 15 sub-regions of Taiwan for the relationship between tropospheric vertical column and surface concentration of NO₂.

        The preliminary results reveal high correlation between surface NO₂ and tropospheric NO₂ in North Taiwan (Taipei/New Taipei City/Keelung), Yunlin, Tainan and Kaohsiung. Relative low correlation in Yilan, Hualian because of broad area with less ground-based stations. On the other hand, in order to avoid the impact of short-term factors, monthly mean concentration of NO₂ is applied for further statistics. The results indicate high relationship in most of counties, except Hsinchu and Taitung. This suggests that the tendency of surface NO₂ is similar to the tropospheric NO₂ in most of countries in Taiwan in the monthly scale. Therefore, in order to monitor and analysis of NO₂ concentration, spaceborne TROPOMI on S5P might be an alternative choice for conducting related research in Taiwan.

How to cite: Cai, Y.-J., Liu, C.-Y., and Chou, C.: Spatiotemporal Characteristics of Tropospheric and Surface NO2 from Sentinel-5 Precursor (S5P) and in-situ Observations in Taiwan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2802, https://doi.org/10.5194/egusphere-egu2020-2802, 2020.

This study investigated the influence of upslope fog formation on the chemical composition and single hygroscopicity parameter (κ) of rural aerosols. The compositions were monitored using a mini compact time-of-flight aerosol mass spectrometer (mini-C-ToF-AMS), and a scanning mobility particle sizer (SMPS) from Dec. 1st to Dec. 24th, 2018 at the Xitou forest site (23.40°N, 120.47°E, 1,178 m asl) in Taiwan. Ambient wet aerosol particles were collected by a 13-stage nano-MOUDI II impactor (micro-orifice uniform deposit impactors) and analyzed using a Fourier-transform infrared spectrometer with an attenuated total reflectance accessory (FTIR-ATR). The single hygroscopicity parameter (κ) of aerosols derived from the comparison of AMS pToF size distribution using the κ-Köhler equation and FTIR-ATR measurement. The moderate correlation (r = 0.73) between the oxidized oxygenated organic aerosol (OOA) and CO evidenced the upstream anthropogenic emission transport by sea/land breezes. The decreasing (aerosol mass)/CO ratio with decreasing visibility trends during in-fog periods at two dense foggy events indicated that the fog activation scavenging mechanism dominated the aerosol particle removal. The inconsistency of online real-time AMS and offline FTIR-ATR measurement for submicrometer particles indicated that the evaporation loss of HNO₃ or NH₄NO₃ particles during MOUDI filter sampling could lead to the unavailable κ retrieval for nitrate-containing particles at non-foggy daytime and the discrepancy of aerosol acidity. Similar κ ranges of organic carboxylic acid group particles (0.1 < κ_p-org < 0.3), ammonium-containing, and sulfate-containing particles (0.2 < κ_p-NH4 or κ_p-SO4< 0.5) but ambiguous nitrate-containing particles (0.4 < κ_p-NO3 < 0.6 or 0.6 < κ_p-NO3 < 0.8) were observed at foggy daytime, suggesting that ammonium sulfate and organic carboxylic acid compounds were more likely internal mixture particles with similar hygroscopicity and physicochemical mixing state influenced by upslope fog. However, the distinct κ ranges of sulfate-containing particles (0.5 < κ_p-SO4 < 0.7 or 0.6 < κ_p-SO4 < 0.8) and organic carboxylic acid group particles (0.1 < κ_p-org < 0.2) revealed the different chemical and physical properties of external mixture particles at non-foggy daytime.

How to cite: Chen, C.-L., Chen, T.-Y., Hung, H.-M., Tsai, P.-W., Chen, W.-N., and Chou, C. C.-K.: Influence of Upslope Fog on Hygroscopicity and Chemical Composition of Aerosols at a Forest Site in Taiwan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6387, https://doi.org/10.5194/egusphere-egu2020-6387, 2020.

The performance of air quality modeling (AQM) depends largely on the uncertainty of emission inventory. Since the emission data is an important input for AQM, this study tried to validate the controversial emission inventory. The Taiwan EPA (TEPA) has released the latest TEDS10.0 (Taiwan Emission Database System, version 10.0) based on 2016. This emission has attracted high arguments among governments and academics. This study applied the SMOKE v4.6 (Sparse Matrix Operator Kerner Emissions) to process the TEDS. The study used the CEMS (Continuous Emission Monitoring System) data and replaced temporalized large point source which accounts for 70% of all point source emissions, updated the biogenic emission calculation, improved the temporal profile of NH3, several area sources, and all mobile sources. Then we utilized the CMAQ (Community Modeling and Analysis System) model to simulate a PM2.5 event. However, the performance of the abovementioned improvement for emission processing is still not satisfactory. Therefore, this study tried to adjust the emission inventory according to the comparison of simulations and observations. The performance of air quality modeling has been improved after adjustment.  Meanwhile, this study provided suggestions of several aspects to be improved to the TEPA.

How to cite: Chuang, M.-T., Chou, C. C.-K., and Lin, C.-Y.: Validation and improvement of Taiwan Emission inventory for air quality modeling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7979, https://doi.org/10.5194/egusphere-egu2020-7979, 2020.

In ASEAN (Southeast Asia) countries, anthropogenic emissions have increased significantly over the last two decades from a variety of sources, including power and heating, industries, road-transportation, residential, and agricultural activities. In this study, we analyzed different emission inventories (i.e., MICS-Asia, REAS, EDGAR) to provide the integrated emissions for ASEAN during the period 2000-2010. The study found that anthropogenic emission contribution from ASEAN countries to the total Asian emission was notable during that period. For instance, from the MIX-Asian EI, our analysis shows that the average contribution was the highest from the transportation sector (34%), followed by residential (29%), power (24%), and industrial sector (14%), respectively in 2010. However, similar to the sector-specific emission contribution in 2000 in ASEAN countries, residential sector was the most significant contributor for CO (53%), PM10 (48%), PM2.5 (63%), BC (76%), OC (79%) in 2010, although it is in decreasing trend compared to other sectors. On the contrary, emission contribution of SO2 was the highest from the industrial sector (47%), followed by power (36%), while NOx and NMVOC were contributed mainly by transportation sector (55% and 45%, respectively). Spatially, the emission intensities of SO2, CO, NOx, NMVOC, PM10, PM2.5, BC, OC, and CO2 were high in the major urban cities of Thailand, Vietnam, Malaysia, Philippines, and Indonesia except CH4, N2O, and NH3, which were high in the rural areas of ASEAN countries.

How to cite: Lam, Y. F., Roy, S., and Chui, K. W.: Southeast Asian anthropogenic emission changes: An analysis from regional and global emission inventories, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12495, https://doi.org/10.5194/egusphere-egu2020-12495, 2020.

Air pollution becomes a serious issue due to the population growing up and residential area sprawl in decades. Residential area is not only a major source of air pollutants but also an impact to generate an urban-rural thermal wind and to alter the dispersion of air pollutants. However, the urban-rural breeze caused by a metropolitan is not the only impact on the dispersion of air pollutants. Generally, a synoptic weather condition is the major impact to dominate how the air pollutant exactly diffuses. The most metropolitans are located in the coastal regions. Therefore, a naturally thermal wind, sea-land-breeze, plays also commonly an essential role to transfer the air pollutant. Additionally, topography and natural obstacle are unable to be ignored as an impact to obstruct flow streaming which brings the air pollutant away.

Overall, synoptic weather conditions, local sea-land-breeze patterns, and natural obstacles are three major natural impactors to influence air pollutant dispersion. The urban-rural-breeze pattern and the roughness of the urban area are regarded as the two anthropogenic factors to alter the large breeze system and thereby affecting the spreading pathway of the air pollutant. To analysis the interaction of above mentioned five impactors could be regarded as a comprehensive approach to consider how the air pollutant transfer from a metropolitan to air pollution suffering areas.

In this study, we apply either computational or measurement tools to consider the effects of metropolitan, Taichung, which is located in middle Taiwan, in the heat island effect and modification of the roughness to alter the natural breeze and also the dispersion of the air pollutant. Several intensive observation periods of 3-dimensional wind field network in boundary layer have been proposed as the evidences to discuss the impacts of urban sprawl on the breeze circulation in Taichung. Otherwise, a large-eddy-simulation model, Parallel-Large-Eddy-Simulation Model (PALM) is applied in the study initially to realize the influence of synoptic weather conditions and topography on air pollutant dispersion. Thereafter, the impacts of the heat fluxes and the roughness changing due to the urban sprawl are proposed in the study. Overall, the altering of metropolitan on the natural breeze is a slight but significant impact and could change the air pollutant dispersion.

Key Words: Boundary Layer, Wind field, Large-Eddy-Simulation, PALM, Urban Sprawl, Heat Island Effect, Thermal Wind

How to cite: Chen, Y.-C., Hwang, G.-D., Chen, W.-N., and Chou, C.-K. C.: Air pollutant dispersion altered by urban-rural breeze and urban sprawl, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6549, https://doi.org/10.5194/egusphere-egu2020-6549, 2020.

To investigate the interaction between local circulation and aerosol major chemical composition and hygroscopicity, a series of studies in Xitou Experimental Forest of National Taiwan University (23.40°N, 120.47°E, 1,178 m asl) in December 2018 was conducted. The isotopes of δ¹⁵N and δ¹⁸O from the filter samples were applied to identify the possible formation pathways. The single hygroscopicity parameter, κ, of aerosols between 9-437 nm in diameter was derived from the measurements of a cloud condensation nuclei counter (CCNc), an ultrafine condensation particle counter (UCPC) and a scanning mobility particle sizer (SMPS) using the κ-Köhler equation. Filter samples collected by a multi-orifice uniform deposit impactor (MOUDI) were applied to quantify the major aerosol composition based on the absorbance of selected functional groups (NH₄⁺, SO₄^2-, NO₃^-, elemental carbon) by a Fourier transform infrared spectroscopy with an attenuated total reflection accessory (FT-IR-ATR). The δ¹⁵N of particulate NH₄⁺ (p-NH₄⁺) and particulate NO₂^- or NO₃^- (p-NO_x^-) and the δ¹⁸O of p-NO_x^- were analyzed by an isotopic ratio mass spectroscopy (IR-MS) to infer the source and chemical pathway of aerosols. The mean κ value of aerosol is mostly between 0.07 and 0.22 during the field study period. The aerosol concentration shows a significant correlation with the local circulation, sea-land breeze combined with the mountain-valley circulation, and is significantly higher in the daytime than that in the nighttime. The foggy period has revealed a higher concentration of NH₄⁺, SO₄^2-, NO₃^-, and elemental carbon (or black carbon, BC), which may be caused by the lower boundary layer and weaker upward turbulent mixing during the foggy period. Aerosols containing NH₄⁺, SO₄^2- shifted to the larger size distribution during the foggy period and that is likely due to the hygroscopic growth of aerosols containing these functional groups at higher RH. The observed stable and high NO₃^- concentration of aerosol in the diameter of 0.56-1 µm during foggy periods is likely caused by the partition of HNO₃ in the aqueous phase under a basic condition or further stabilized by the dissolved ammonium to form particulate NO₃^-. The daily mass-weighted δ¹⁵N of p-NH₄⁺ is ranged from +3.7‰ to +16.3‰ and δ¹⁵N of p-NO_x^- from +1.5‰ to +5.2‰, indicating that p-NH₄⁺ and p-NO_x^- are likely contributed from anthropogenic sources such as coal-burning and traffic. The δ¹⁸O of p-NO_x^- is in the range of +70‰ to +80‰, similar to the result of southeast Asia in winter. The observed high δ¹⁸O might be contributed through the pathways of the oxidation of NO with O₃ to form NO₂, which is further oxidized by OH radicals to form HNO₃.

How to cite: Chen, T.-Y., Chen, C.-L., Hung, H.-M., Chen, Y.-C., Ren, H., Chen, W.-N., and Chou, C. C.-K.: Aerosol Composition, Physiochemical Properties, and Source Apportionment at a Forest Site in Taiwan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12255, https://doi.org/10.5194/egusphere-egu2020-12255, 2020.

Observations of tropospheric peroxy radicals are a key point for interpretation of the processing and transformation of polluted outflows from major populated centres (MPCs). A series of European MPCs are investigated by the project EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional and Global scales). With this objective two airborne campaigns using the research platform HALO (High Altitude and LOng range aircraft) were carried out over Europe in summer 2017 and over east Asia in the intermonsoon period in 2018. The Institute of Environmental Physics (IUP) in Bremen (Germany) participated in both EMeRGe campaigns with the airborne measurement of the total sum of peroxy radicals, RO₂^*, by using  the home made PeRCEAS instrument based on the combination of the PERCA (peroxy radical chemical amplification)  and CRDS (cavity ring down spectroscopy) techniques. One of the main purposes of the campaigns was the investigation of the characteristics and chemical transformation of MPC outflows at the local and regional scales.

During the EMeRGe campaign in Europe, air masses of different photochemical activity were measured, where RO₂^* mixing ratios up to 100pptv being observed. In the present study the RO₂^* observations for six measurement flights of EMeRGe in Europe have been compared with RO₂ (here defined as the sum of HO₂ + CH₃O₂ + ISOOH + CH₃CO₃ + CH₃COCH₂O₂) simulated by using the MECO(n) model.

MECO(n) (MESSy-fied ECHAM and COSMO models nested n times), is  a global/regional chemistry-climate model developed by the MESSy consortium, which couples on-line the global chemistry-climate model EMAC with the regional chemistry-climate model COSMO-CLM/MESSy. The same anthropogenic emission inventory (EDGAR 4.3.1) as well as the same solver for chemical kinetics, involving complex tropospheric and stratospheric chemistry, are applied in EMAC and COSMO-CLM/MESSy.

Overall, the agreement between the measurements and model is reasonable for RO₂^* observations below 40 pptv. Events with higher mixing ratios seem not to be well reproduced by the model but underestimated. Further details on the modelling and the result of the comparison will be presented.

How to cite: Liu, Y., Mertens, M., Andrés Hernández, M. D., George, M., Nenakhov, V., Kerkweg, A., Jöckel, P., and Burrows, J. P.: Comparison of Airborne Peroxy Radical Measurements with MECO(n) model simulation during EMeRGe in Europe , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18247, https://doi.org/10.5194/egusphere-egu2020-18247, 2020.

Comprehensive regional chemistry-climate or chemistry transport models are important tools to study the impact of emissions from major population centres (MPC) and/or investigate potential mitigation options for MPC emissions. Before such models can be employed it is important to investigate how well the models represent observed atmospheric conditions. This comparison helps not only in judging the performance of the models, but allows to test our understanding of chemical and physical processes in the atmosphere. A prerequisite for an extensive evaluation of models are the availability of temporally and spatially high resolved observational data. Such a data set was obtained during the EMeRGe-Europe campaign of the HALO research aircraft in July 2017, which targeted the outflow of different MPC in Europe.

We used the data of the EMeRGe-EU campaign together with ground based observations to evaluate the representation of European MPC emissions in the MECO(n) model system. MECO(n) is a global/regional chemistry-climate model which couples the regional chemistry-climate model COSMO-CLM/MESSy on-line (i.e., during runtime) with the global chemistry climate-model EMAC. The dynamics of EMAC is nudged against ERA-Interim reanalysis data. We performed three nesting steps from 300 km on the global scale to 50 km, 12 km and 7 km on the regional scale. In our evaluation we focus on tropospheric ozone (O₃) and related precursors, methane (CH₄) and sulphur dioxide (SO₂). 

Generally, the comparison between the measurements and the model results shows a good representation of European MPC emissions in MECO(n). In detail, however, the measured mixing ratios of carbon monoxide (CO) and reactive nitrogen (NO_y)  are underestimated, while O₃ and SO₂ are overestimated by the model. Potential reasons for these differences are too efficient vertical mixing, and underestimation of MPC emissions. 

To test hypotheses for potential model improvements we performed additional sensitivity studies with different nudging data for EMAC and an alternative anthropogenic emission inventory. The differences of the model results to the observations, however, are only slightly influenced by these changes. Accordingly, further hypotheses for potential model improvements needs to be investigated.  While the simulated mixing ratios differ only slightly between the sensitivity studies, the ozone source apportionment results (using a tagging approach) show much larger differences. This indicates the large uncertainty of  source apportionment analyses caused by uncertainties of emission inventories and model dynamics and requires further analysis in the future. 

How to cite: Mertens, M., Kerkweg, A., Jöckel, P., Kilian, M., Eirenschmalz, L., Grewe, V., Klausner, T., Schlager, H., Ziereis, H., Andrés Hernández, M. D., and Burrows, J. P.: Representation of emissions from European major population centeres in MECO(n) - Lessons learned from EMeRGe-EU, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16941, https://doi.org/10.5194/egusphere-egu2020-16941, 2020.

Aerosols can have a great impact on air quality and human health. In addition they can affect air transport by causing damage in aircraft engines.

To study the transport and transformation of anthropogenic pollutants from major population centers, two airborne measurement campaigns were conducted in the framework of the EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) Project using the German High Altitude-Long-Range (HALO) research aircraft. The aircraft was equipped with a wide range of instrumentation to measure atmospheric constituents. Here we report on results from the measurements characterizing aerosol microphysical properties. Measurements included particle number concentration and size distributions in a size range between 10 nm and ~3 µm as well as absorption properties. Aerosols were measured in the outflow of major population centers in Europe in summer 2017 (EMeRGe-EU) and along the Asian Pacific coast in spring 2018 (EMeRGe-Asia). In selected case studies we investigated detected aerosol layers, their likely source regions and transport paths. Case studies include the pollution along the west coast of Taiwan as well as the outflows of Manila (Philippines) and London (United Kingdom). Differences and similarities between Europe and Asia and the correlations with trace gases such as SO₂, CO₂ and CH₄ are discussed.

How to cite: Wolf, J., Sauer, D., Eirenschmalz, L., Klausner, T., and Schlager, H.: Aerosol microphysical properties for selected case studies during the EMeRGe-EU and EMeRGe-Asia campaigns, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18315, https://doi.org/10.5194/egusphere-egu2020-18315, 2020.

During the EMeRGe campaign we employed a cloud condensation nuclei counter (CCNC) on board the research aircraft HALO. The instrument was located in the CCN-Rack probing together with a single particle soot photometer (SP2) and a multi-impactor for sampling different air masses on silica nitrate substrates. The aerosol particles were sampled through the HALO Aerosol Submicrometer Inlet (HASI). The measurements have been performed with a two column continuous-flow longitudinal thermal-gradient instrument (CCN-200) manufactured by DMT. The CCN-200 measures the CCN number concentration as a function of water vapor supersaturation (S). These measurements are performed by changing S within one column from 0.10 % up to 1.00 % using 12 different supersaturations and keeping S constant within the second column (S = 0.38 %) to ensure baseline data with 1 Hz time resolution. The different supersaturations are created by changing the flow while setting a fixed temperature difference.

Purpose of EMeRGe is to quantify and qualify outflows of megacities, as well as their transport and transformation in the atmosphere. Therefore, measurement flights were performed in the European airspace in 2017, probing aerosol properties over cities like London, Barcelona and Rome. In March 2018, the same set of instruments was probing the outflows of Asian megacities like Taipei, Manila and aged pollution from China Mainland. Furthermore, Japanese and South Korean outflows could be probed. The measurements took place in altitudes between 0.3 km and 13 km ASL. The scientific objective is to investigate the effect of different pollution states on aerosol and CCN properties.

How to cite: Pöhlker, M. L., Krüger, O. O., Holanda, B. A., Pöhlker, C., Klimach, T., Su, H., Cheng, Y., Nenakhov, V., Andrés Hermándes, M. D., Burrows, J. P., and Pöschl, U.: Cloud condensation nuclei (CCN) measurements with the HALO aircraft during EMeRGe in European and Asian airspace, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20218, https://doi.org/10.5194/egusphere-egu2020-20218, 2020.

The Indo Gangetic Plain (IGP), home to more than 400 million people, encompasses most of northern and eastern India, the most populated parts of Pakistan, and Bangladesh. Cities in the IGP are among the most polluted in the world, with levels of particulate matter with diametres smaller than 2.5 microns (PM_2.5), often far exceeding human health recommendations. Seasonal changes in the physical and chemical environment over the IGP are dominated by the large-scale South Asian monsoon system, but also by seasonal sources such as lifting of dust from the Thar desert and agricultural stubble burning at the end of the growing seasons. Organic aerosol (OA) represents a major contribution to PM_2.5. They exist in a complex mixture, comprising of thousands of individual organic compounds. OA is made up of primary OA (POA), emitted directly to the atmosphere, and by secondary OA (SOA) formed by the gas-phase oxidation of volatile organic compounds. We use the WRF-Chem regional atmospheric chemistry model to study seasonal changes in the chemical properties of fine particulate matter over the IGP. In particular, we use the Volatility Basis Set (VBS) model in WRF-Chem to study both POA and SOA seasonal variations, and to quantify the importance of seasonal sources of OA to PM_2.5 over the IGP. We evaluate the model using satellite observations of aerosol optical properties.

How to cite: Mogno, C., Palmer, P., and Knote, C.: What drives seasonal variations of organic aerosol over the Indo Gangetic Plain?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4932, https://doi.org/10.5194/egusphere-egu2020-4932, 2020.

The Middle East is notorious for high air pollution that affects both air-quality and regional climate. The Middle East generates about 30% of world dust annually and emits about 10% of anthropogenic SO₂. In this study we use Modern-Era Retrospective analysis for Research and Applications v.2 (MERRA-2), Copernicus Atmosphere Monitoring Service Operational Analysis (CAMS-OA) data assimilation products, and a regional Weather Research and Forecasting model (10 km resolution) coupled with Chemistry (WRF-Chem) to evaluate natural and anthropogenic air pollution in the ME. The SO₂ anthropogenic emissions used in WRF-Chem are updated using the independent satellite SO₂ emission dataset obtained from the Ozone Monitoring Instrument (OMI) observations onboard NASA EOS Aura satellite. Satellite and ground-based aerosol optical depth (AOD) observations, as well as Particulate Matter (PM) and SO₂ in situ measurements for 2015-2016, were used for validation and model evaluation. 

Although aerosol fields in regional WRF-Chem and global assimilation products are quite consistent, WRF-Chem, due to its higher spatial resolution and novel OMI SO₂ emissions, is preferable for analysis of regional air-quality over the ME. We found that conventional emission inventories (EDGAR-4.2, MACCity, and HTAP-2.2) have uncertainties in the location and magnitude of SO₂ sources in the ME and significantly underestimate SO₂ emissions in the Arabian Gulf. CAMS reanalysis tends to overestimate PM_2.5 and underestimate PM₁₀ concentrations. In the coastal areas, MERRA2 underestimates sulfate and tends to overestimate sea salt concentrations. The WRF-Chem’s PM background concentrations exceed the World Health Organization (WHO) guidelines over the entire ME. The major contributor to PM (~75–95%) is mineral dust. In the ME urban centers and near oil recovery fields, non-dust aerosols (primarily sulfate) contribute up to 26% into PM_2.5. The contribution of sea salt into PM can rich up to 5%. The contribution of organic matter into PM prevails over black carbon. SO₂ surface concentrations in major ME cities frequently exceed European air-quality limits.

How to cite: Ukhov, A., Mostamandi, S., Flemming, J., DaSilva, A., Krotkov, N., Li, C., Alshehri, Y., Anisimov, A., Fioletov, V., McLinden, C., Shevchenko, I., and Stenchikov, G.: Assessment of Air Pollution in the Middle East Using Reanalyses Products and High-resolution WRF-Chem Simulations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3472, https://doi.org/10.5194/egusphere-egu2020-3472, 2020.

In recent years, reactive nitrogen concentration and potentiality has been of environmental concern. India being the second largest populated country in world, huge amount of NH3+ emissions are expected from various activities of humans, agriculture and individual sources. This work has been carried out to calculate wet deposition fluxes of Nr species in rain water and to understand their scavenging behaviour at a typical residential site under semiarid tropical region. For this purpose, sequential sampling of rain events has been performed for determining Nr levels during monsoon 2015 and 2016. Samples were analysed for reactive nitrogen species. The wet deposition flux was observed to be 2.13 kg ha-1year-1 for NH4+-N and 3.62 kg ha-1year-1 for NO3- -N in 2015. However, significant increase in NO3--N was observed in 2016 where as there was no remarkable change for NH4+. This clearly indicates towards dynamic behaviour pattern showing sources of reactive nitrogen in air over the region. Scavenging patterns confirmed the presence of NH4NO3 showing co-variations of NH4+ and NO3- along with the rainfall intensity. Thereby, confirming the possible forms in which these Nr species are being deposited over the study area.

How to cite: Chaturvedi, M. and Kulshrestha, U.: Reactive nitrogen fluxes and scavenging patterns through sequential sampling over Mathura, India. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21779, https://doi.org/10.5194/egusphere-egu2020-21779, 2020.

The estimation of emissions inventories of climate forcing species and air pollutants from activities such as the burning of biomass from cooking food in rural environments in Mexico presents some degree of uncertainty due to the lack of locally obtained emission factors; emissions estimates were generally obtained with other types of biomass and cookstoves. The relevance of these pollutants to Mexico is mainly due to their contribution to air pollution, global warming and negative impacts on human health. This study presents an assembly of a series of theoretical-experimental procedures for the estimation of emission factors in improved stoves and other biomass burning processes. The design is based on the use of a controlled dilution system from which samples are obtained for the determination of PM_2.5 and the content of organic carbon and elemental carbon. The flow of diluted samples is conditioned for continuous monitoring of polluting gases (NOx, CO, NHMC, and SO₂), in addition to climate forcing gases such as CO₂ and CH₄ with a mobile laboratory equipped with instrumentation for air quality measurements. The new sampling design allows the determination of gaseous and particle matter emission factors through the application of two procedures: carbon mass balance and concentration ratios with respect to CO₂ and CO. The proposed design was evaluated for three improved cookstoves (Patsari, Onil, Ecoestufa) using a water boiling test protocol and white oak as fuel, the proposed controlled dilution sampling design can be a reliable method for the determination of emission factors from small combustion sources when biomass is used as fuel and also by using the carbon balance to obtain the emission factors, we reduce the inherent uncertainties of the process due to the difficulty associated with the sampling of this type of emissions under isokinetic conditions in low flow exhaust conditions such as those of small emission sources. The final emission factor consists of a weighted range of the factors determined for each species with respect to the amount of oxidized carbon in each of them. The feasibility of the experimental design is demonstrated by an application of using white oak wood as fuel in three improved cookstoves and one three stones. The ranges of emission factors obtained for the three improved cookstoves in g/kg of wood consumed were: CO₂, 1309-1375; CH₄, 3-4; EC, 0.16 – 0.71; OC 1.94-2.89; CO, 63 - 103; y PM_2.5, 3.17 – 4.12, while for the three stones the ranges of emission in g/kg of wood consumed were: CO₂, 1141- 1232; CH₄, 4.15-4.71; EC, 1.06 – 1.78; OC, 4.79-6.03; CO, 124 - 170; y PM_2.5, 7.47 – 10.18 g/kg.

How to cite: Padilla Barrera, Z., Torres Jardón, R., Ruiz, L. G., Castro, T., Peralta, O., Macera, O., and Molina, L.: Coupling of two methods to obtain pollutant emission factors from biomass burning in small combustion sources, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20875, https://doi.org/10.5194/egusphere-egu2020-20875, 2020.

The WRF-Chem model was used to analyze three different 14-day periods during 2016–2017 in Prague, Czech Republic. Specifically a summertime high-level ozone episode, a summertime convective episode and a wintertime episode with high concentrations of aerosol pollutants have been analyzed in great detail. Simulations were run on a 2 km grid domain covering the center of the Czech Republic with the capital Prague, which was nested into a 10 km domain covering Central Europe. For the analysis of the meteorological impact of the reduction of urban induced emissions, two model simulations were performed for each episode; one simulation with full anthropogenic emissions and a second idealized simulation where emissions over the Prague urban area were reduced to the background level. In this presentation we discuss the differences and similarities between these simulations for chemical species (gas and particle pollutants) but also meteorological variables (e.g., downward solar radiation, temperature, boundary layer height).

How to cite: Karlický, J.: Do local urban emissions influence ambient meteorology?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21630, https://doi.org/10.5194/egusphere-egu2020-21630, 2020.

Sources and Sinks of Nitrated Phenols: Application of an Observation-based Model

Yuwen Peng¹, Sihang Wang¹, Caihong Wu¹, Jipeng Qi¹, Chaomin Wang¹,
Wei Song², Xinmin Wang², Bin Yuan^1,*, Min Shao^1,**

¹ Institute for Environmental and Climate Research, Jinan University, 511443 Guangzhou, China

² Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China

^* byuan@jnu.edu.cn

^** mshao@pku.edu.cn

Abstract: Nitrated phenols are one of the intermediate products of aromatics oxidation that has been proved to be phytotoxic, mutagenic and important components of brown carbon and SOA in the atmosphere. Although its sources and sinks have been reported, high-time-resolution measurements of nitrophenols and the evaluation of reported rate constants insufficient. In this paper, we measured the concentration of nitrated phenols at an urban site in Guangzhou, then we use an observation-based model to compare different photolysis frequencies of nitrophenol and analyze its budget. The primary emission of traffic seems to be the dominant factor when considering its diurnal profile. Photolysis has proved to be the dominant sink of nitrophenol in the atmosphere.

How to cite: Peng, Y.: Sources and Sinks of Nitrated Phenols: Application of an Observation-based Model , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12915, https://doi.org/10.5194/egusphere-egu2020-12915, 2020.

  Clustering analysis using air parcel trajectories is actively used to investigate transport patterns of pollutants. To estimate the impact of nuclide dispersion from nuclear accident, comprehensive information based on long-term meteorological data is required to eatablish a complete and efficient public protection plan. Most of nuclear plants in South Korea are located in a complex terrain near coastal area that involves complicated meteorological phenomenon such as sea breezes and mountain-valley breezes. Robust approach based on long-term climatrological data is required to fully resolve the impacts near Korean nuclear power plants.

  In this study, we assessed the impacts of potential nuclear accident in South Korea by clustering dispersion patterns using 10-year meteorological data. Flow patterns are clustered using trajectory cluster analysis, and then combined with dispersion simulations to demonstrate the clustered dispersion patterns by each season and nuclear power plant.

  The long-term meteorological simulations from 2007 to 2016 were used to evaluate the potential impact of nuclear accidents in Korea, and the modeling framework was designed to show the impact map according to the flow patterns near each nuclear power plant. NOAA HYSPLIT modeling additional clustering analysis suggests that two or three cluster patterns for each power plant can be used. A total of 38 flow patterns are classified near the four nuclear plants in the previous season based on a 10-year wind field analysis. Korea has very complex terrain and coastal areas, and more sophisticated modeling efforts are needed to fully understand the more realistic dispersion characteristics of air masses. In terms of space-time resolution, updating land use information for simulation is very important for weather simulation near the surface of Korea.

  The results of this study can be used as a guideline for constructing a modeling framework for nuclide diffusion simulations, but given these complex simulation configurations, the results demonstrated in the current study are should be interpreted with caution.

How to cite: Lee, H., Jin, C., and Kim, C.: Cluster analysis for dispersion patterns near nuclear power plants in South Korea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22223, https://doi.org/10.5194/egusphere-egu2020-22223, 2020.