Flugzeuggetragene Messungen von Ameisensäure und Schwefeldioxid in Emissionsfahnen urbaner Ballungsräume in Europa und Asien

Ameisensäure (HCOOH) und Schwefeldioxid (SO2) zählen zu den wichtigsten organischen Säuren beziehungsweise anorganischen Säurevorläufern, die gasförmig in der Atmosphäre vorkommen. Erste detaillierte simultane Messungen von Ameisensäure und Schwefeldioxid in Emissionsfahnen urbaner Ballungsräume in Europa und Ostasien werden in dieser Arbeit vorgestellt. Als Luftschadstoffe wirken sich beide Gase auf die Gesundheit der Bevölkerung aus, zum Beispiel durch Beeinträchtigung der Atemwege und des Herzkreislaufsystems. Zudem beeinflussen sie die Bildung und Eigenschaften von Aerosolen und Wolken und tragen zu saurem Regen bei, wodurch die Flora und Fauna geschädigt werden kann. Zur Reduktion der Luftschadstoffe ist ein genaues Verständnis über ihre Quellen, Senken und Transformationen während des Transports notwendig, wozu flugzeuggetragene In-situ Messungen in Emissionsfahnen urbaner Ballungszentren beitragen können. Im Rahmen des Projekts EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) wurden an Bord des Forschungsflugzeugs HALO während zweier Messkampagnen von Oberpfaffenhofen bei München im Juli 2017 und von Tainan (Taiwan) im März 2018 Messungen durchgeführt. Die Messungen fanden mit einem Chemischen-Ionisations-Ionenfallen-Massenspektrometer (Chemical Ionization Ion Trap Mass Spectrometer (CI-ITMS)) unter Verwendung einer CO3(-) Ionenchemie statt. Kalibrierungen wurden durchgeführt, indem dem Probenfluss isotopisch markiertes SO2 aus einem Gasstandard und HCOOH aus einer Permeationsquelle zugesetzt wurden. Im Zuge der EMeRGe-Kampagnen konnten Schadstofffahnen der Metropolregionen London (UK), Benelux (BE, NL, LU), Ruhrgebiet (DE), Po-Ebene, Rom (IT), Paris, Marseille (FR) und Barcelona (ES) in Europa sowie Taichung, Taipeh (Taiwan), Pearl Flussdelta, Jangtse Flussdelta (China), Manila (Republik der Philippinen), Seoul (Republik Korea), Nagoya, Osaka und Tokio (Japan) in Asien vermessen werden. Die Entfernungen zu den jeweiligen Quellregionen betrugen zwischen 500 m und 2000 km. Eine Zuordnung der vermessenen Emissionsfahnen zu den Quellregionen wurde unter Verwendung von Luftmassentrajektorien- und Emissionsdispersionsberechnungen sowie Perfluorcarbon-Tracer-Experimenten für ausgewählte Fälle hergestellt. Zur Charakterisierung der Schadstofffahnen wurden Emissionsverhältnisse (emission ratios (ER)), Korrelationsanalysen zwischen Spurengasen und zwischen Spurengasen und Aerosoleigenschaften sowie Kohlenwasserstoff-Tracer herangezogen, wie Benzol, Acetonitril und Isopren für Emissionen aus anthropogenen und biogenen Quellen sowie Verbrennung von Biomasse. Generell wurde herausgefunden, dass das ER von HCOOH/CO mit dem Alter der Emissionsfahnen zunimmt und in Europa bzw. Asien zwischen 0.05 - 0.57 und 0.03 - 0.08 liegt. Weiter wurde festgestellt, dass die Erhöhungen durch eine sekundäre Bildung von HCOOH in den Emissionsfahnen hauptsächlich durch Oxidation der Isopren-Emissionen verursacht sind. Die ermittelten HCOOH-Bildungsraten betragen 18.5 pmol mol-1 HCOOH / nmol mol-1 CO pro Stunde und 1.25 pmol mol-1 HCOOH / nmol mol-1 CO pro Stunde in Schadstofffahnen in Europa bzw. Asien. Die höheren HCOOH-Produktionsraten in den europäischen Emissionsfahnen sind auf die höheren Isopren-Emissionen in den Quellregionen in Europa im Juli zurückzuführen, verglichen mit den Werten in Asien im März. Die Zunahme von HCOOH mit dem Alter der Emissionsfahne wird auch durch Simulationen mit dem Chemie-Transport-Modell WRF-Chem für den Fall der Manila-Emissionsfahne gezeigt. Die höchste HCOOH-Produktionsrate (33 pmol mol-1 HCOOH / nmol mol-1 CO pro Stunde) wurde in einer Rauchfahne eines großen europäischen Waldbrandes im Jahr 2017 in der Nähe von Marseille, aufgrund des sehr hohen Isopren-Gehalts in der Fahne, beobachtet. Die ermittelten ER von SO2/CO nehmen generell mit dem Alter der Emissionsfahnen ab. Grund dafür ist die Oxidation von SO2 zu H2SO4 (Schwefelsäure), was zu Bildung und Wachstum von Sulfat-Aerosolen in den Schadstofffahnen führt. Eine SO2-Lebensdauer von 10 bis 15 Stunden bzw. 30 bis 43 Stunden konnte für Emissionsfahnen in Europa bzw. Asien abgeleitet werden. Die gemessenen Mischungsverhältnisse von HCOOH und SO2 korrelieren stark mit der Konzentration von organischem Aerosol und Sulfat-Aerosol in den Schadstofffahnen, was auf ihre wichtige Rolle bei der Aerosolbildung und dem Aerosolwachstum hinweist. Die HCOOH- und SO2-Messungen werden auch mit früheren Flugzeugmessungen und mit numerischen Modellsimulationen der Chemie-Klima- und Chemie-Transport-Modelle MECO(n) und WRF-Chem verglichen. Dabei wurde herausgefunden, dass die HCOOH-Mischungsverhältnisse in den Emissionsfahnen in beiden Modellen stark unterschätzt werden. Die vorliegenden Messungen zeigen die zunehmende Bedeutung organischer Emissionen wie HCOOH im Vergleich zu den regulierten klassischen Emissionen SO2 und NOy für die Eigenschaften von Aerosolen, Wolken und Niederschlägen

Overview: On the transport and transformation of pollutants in the outflow of major population centres – observational data from the EMeRGe European intensive operational period in summer 2017

Megacities and other major population centres (MPCs) worldwide are major sources of air pollution, both locally as well as downwind. The overall assessment and prediction of the impact of MPC pollution on tropospheric chemistry are challenging. The present work provides an overview of the highlights of a major new contribution to the understanding of this issue based on the data and analysis of the EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) international project. EMeRGe focuses on atmospheric chemistry, dynamics, and transport of local and regional pollution originating in MPCs. Airborne measurements, taking advantage of the long range capabilities of the High Altitude and LOng Range Research Aircraft (HALO, https://www.halo-spp.de, last access: 22 March 2022), are a central part of the project. The synergistic use and consistent interpretation of observational data sets of different spatial and temporal resolution (e.g. from ground-based networks, airborne campaigns, and satellite measurements) supported by modelling within EMeRGe provide unique insight to test the current understanding of MPC pollution outflows. In order to obtain an adequate set of measurements at different spatial scales, two field experiments were positioned in time and space to contrast situations when the photochemical transformation of plumes emerging from MPCs is large. These experiments were conducted in summer 2017 over Europe and in the inter-monsoon period over Asia in spring 2018. The intensive observational periods (IOPs) involved HALO airborne measurements of ozone and its precursors, volatile organic compounds, aerosol particles, and related species as well as coordinated ground-based ancillary observations at different sites. Perfluorocarbon (PFC) tracer releases and model forecasts supported the flight planning, the identification of pollution plumes, and the analysis of chemical transformations during transport. This paper describes the experimental deployment and scientific questions of the IOP in Europe. The MPC targets – London (United Kingdom; UK), the Benelux/Ruhr area (Belgium, the Netherlands, Luxembourg and Germany), Paris (France), Rome and the Po Valley (Italy), and Madrid and Barcelona (Spain) – were investigated during seven HALO research flights with an aircraft base in Germany for a total of 53 flight hours. An in-flight comparison of HALO with the collaborating UK-airborne platform Facility for Airborne Atmospheric Measurements (FAAM) took place to assure accuracy and comparability of the instrumentation on board. Overall, EMeRGe unites measurements of near- and far-field emissions and hence deals with complex air masses of local and distant sources. Regional transport of several European MPC outflows was successfully identified and measured. Chemical processing of the MPC emissions was inferred from airborne observations of primary and secondary pollutants and the ratios between species having different chemical lifetimes. Photochemical processing of aerosol and secondary formation or organic acids was evident during the transport of MPC plumes. Urban plumes mix efficiently with natural sources as mineral dust and with biomass burning emissions from vegetation and forest fires. This confirms the importance of wildland fire emissions in Europe and indicates an important but discontinuous contribution to the European emission budget that might be of relevance in the design of efficient mitigation strategies. The present work provides an overview of the most salient results in the European context, with these being addressed in more detail within additional dedicated EMeRGe studies. The deployment and results obtained in Asia will be the subject of separate publications

CH4 emissions from European major population centers: Results from aircraft-borne CH4 in-situ observations during EMeRGe-Europe 2017

Urban environments represent large and diffuse area sources of CH including emissions from pipeline leaks, industrial/sewage treatment plants, and landfills. However, there is little knowledge about the exact magnitude of these emissions and their contribution to total anthropogenic CH4. Especially in the context of an urbanizing world, a better understanding of the methane footprint of urban areas is crucial, both with respect to mitigation and projection of climate impacts. Aircraft-borne in-situ measurements are particularly useful to both quantify emissions from such area sources, as well as to study their impact on the regional distribution. However, airborne CH observations downstream of European cities are especially sparse

Overview: On the transport and transformation of pollutants in the outflow of major population centres – observational data from the EMeRGe European intensive operational period in summer 2017

Abstract. EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) is an international project focusing on atmospheric chemistry, dynamics and transport of local and regional pollution originating in megacities and other major population centres (MPCs). Airborne measurements, taking advantage of the long range capabilities of the HALO research platform (High Altitude and Long range research aircraft, www.halo-spp.de), are a central part of the research project. In order to provide an adequate set of measurements at different spatial scales, two field experiments were positioned in time and space to contrast situations when the photochemical transformation of plumes emerging from MPCs is large. These experiments were conducted in summer 2017 over Europe and in the inter-monsoon period over Asia in spring 2018. The intensive observational periods (IOP) involved HALO airborne measurements of ozone and its precursors, volatile organic compounds, aerosol particles and related species as well as coordinated ground-based ancillary observations at different sites. Perfluorocarbon (PFC) tracer releases and model forecasts supported the flight planning and the identification of pollution plumes. This paper describes the experimental deployment of the IOP in Europe, which comprised 7 HALO research flights with aircraft base in Oberpfaffenhofen (Germany) for a total of 53 flight hours. The MPC targets London (Great Britain), Benelux/Ruhr area (Belgium, The Netherlands, Luxembourg and Germany), Paris (France), Rome and Po Valley (Italy), Madrid and Barcelona (Spain) were investigated. An in-flight comparison of HALO with the collaborating UK-airborne platform FAAM took place to assure accuracy and comparability of the instrumentation on-board. Generally, significant enhancement of trace gases and aerosol particles are attributed to emissions originating in MPCs at distances of hundreds of kilometres from the sources. The proximity of different MPCs over Europe favours the mixing of plumes of different origin and level of processing and hampers the unambiguous attribution of the MPC sources. Similarly, urban plumes mix efficiently with natural sources as desert dust and with biomass burning emissions from vegetation and forest fires. This confirms the importance of wildland fire emissions in Europe and indicates an important but discontinuous contribution to the European emission budget that might be of relevance in the design of efficient mitigation strategies. The synergistic use and consistent interpretation of observational data sets of different spatial and temporal resolution (e.g. from ground-based networks, airborne campaigns, and satellite measurements) supported by modelling within EMeRGe, provides a unique insight to test the current understanding of MPC pollution outflows. The present work provides an overview of the most salient results and scientific questions in the European context, these being addressed in more detail within additional dedicated EMeRGe studies. The deployment and results obtained in Asia will be the subject of separate publications

Overview: On the transport and transformation of pollutants in the outflow of major population centres – observational data from the EMeRGe European intensive operational period in summer 2017

Megacities and other major population centres (MPCs) worldwide are major sources of air pollution, both locally as well as downwind. The overall assessment and prediction of the impact of MPC pollution on tropospheric chemistry are challenging. The present work provides an overview of the highlights of a major new contribution to the understanding of this issue based on the data and analysis of the EMeRGe (Effect of Megacities on the transport and transformation of pollutants on the Regional to Global scales) international project. EMeRGe focuses on atmospheric chemistry, dynamics, and transport of local and regional pollution originating in MPCs. Airborne measurements, taking advantage of the long range capabilities of the High Altitude and LOng Range Research Aircraft (HALO, https://www.halo-spp.de, last access: 22 March 2022), are a central part of the project. The synergistic use and consistent interpretation of observational data sets of different spatial and temporal resolution (e.g. from ground-based networks, airborne campaigns, and satellite measurements) supported by modelling within EMeRGe provide unique insight to test the current understanding of MPC pollution outflows.In order to obtain an adequate set of measurements at different spatial scales, two field experiments were positioned in time and space to contrast situations when the photochemical transformation of plumes emerging from MPCs is large. These experiments were conducted in summer 2017 over Europe and in the inter-monsoon period over Asia in spring 2018. The intensive observational periods (IOPs) involved HALO airborne measurements of ozone and its precursors, volatile organic compounds, aerosol particles, and related species as well as coordinated ground-based ancillary observations at different sites. Perfluorocarbon (PFC) tracer releases and model forecasts supported the flight planning, the identification of pollution plumes, and the analysis of chemical transformations during transport.This paper describes the experimental deployment and scientific questions of the IOP in Europe. The MPC targets – London (United Kingdom; UK), the Benelux/Ruhr area (Belgium, the Netherlands, Luxembourg and Germany), Paris (France), Rome and the Po Valley (Italy), and Madrid and Barcelona (Spain) – were investigated during seven HALO research flights with an aircraft base in Germany for a total of 53 flight hours. An in-flight comparison of HALO with the collaborating UK-airborne platform Facility for Airborne Atmospheric Measurements (FAAM) took place to assure accuracy and comparability of the instrumentation on board.Overall, EMeRGe unites measurements of near- and far-field emissions and hence deals with complex air masses of local and distant sources. Regional transport of several European MPC outflows was successfully identified and measured. Chemical processing of the MPC emissions was inferred from airborne observations of primary and secondary pollutants and the ratios between species having different chemical lifetimes. Photochemical processing of aerosol and secondary formation or organic acids was evident during the transport of MPC plumes. Urban plumes mix efficiently with natural sources as mineral dust and with biomass burning emissions from vegetation and forest fires. This confirms the importance of wildland fire emissions in Europe and indicates an important but discontinuous contribution to the European emission budget that might be of relevance in the design of efficient mitigation strategies. The present work provides an overview of the most salient results in the European context, with these being addressed in more detail within additional dedicated EMeRGe studies. The deployment and results obtained in Asia will be the subject of separate publications