Simulating the formation of carbonaceous aerosol in a European Megacity (Paris) during the MEGAPOLI summer and winter campaigns

We use a three-dimensional regional chemical transport model (PMCAMx) with high grid resolution and high-resolution emissions (4 × 4 km2) over the Paris greater area to simulate the formation of carbonaceous aerosol during a summer (July 2009) and a winter (January/February 2010) period as part of the MEGAPOLI (megacities: emissions, urban, regional, and global atmospheric pollution and climate effects, and Integrated tools for assessment and mitigation) campaigns. Model predictions of carbonaceous aerosol are compared against Aerodyne aerosol mass spectrometer and black carbon (BC) high time resolution measurements from three ground sites. PMCAMx predicts BC concentrations reasonably well reproducing the majority (70 %) of the hourly data within a factor of two during both periods. The agreement for the summertime secondary organic aerosol (OA) concentrations is also encouraging (mean bias = 0.1 µg m−3) during a photochemically intense period. The model tends to underpredict the summertime primary OA concentrations in the Paris greater area (by approximately 0.8 µg m−3) mainly due to missing primary OA emissions from cooking activities. The total cooking emissions are estimated to be approximately 80 mg d−1 per capita and have a distinct diurnal profile in which 50 % of the daily cooking OA is emitted during lunch time (12:00–14:00 LT) and 20 % during dinner time (20:00–22:00 LT). Results also show a large underestimation of secondary OA in the Paris greater area during wintertime (mean bias =  −2.3 µg m−3) pointing towards a secondary OA formation process during low photochemical activity periods that is not simulated in the model

Influence of vessel characteristics and atmospheric processes on the gas and particle phase of ship emission plumes: in situ measurements in the Mediterranean Sea and around the Arabian Peninsula

International audienceA total of 252 emission plumes of ships operating in the Mediterranean Sea and around the Arabian Peninsula were investigated using a comprehensive dataset of gas- and submicron-particle-phase properties measured during the 2-month shipborne AQABA (Air Quality and Climate Change in the Arabian Basin) field campaign in summer 2017. The post-measurement identification of the corresponding ship emission events in the measured data included the determination of the plume sources (up to 38 km away) as well as the plume ages (up to 115 min) and was based on commercially available historical records of the Automatic Identification System. The dispersion lifetime of chemically inert CO2 in the ship emission plumes was determined as 70±15 min, resulting in levels indistinguishable from the marine background after 260±60 min. Emission factors (EFs) as quantities that are independent of plume dilution were calculated and used for the investigation of influences on ship emission plumes caused by ship characteristics and the combustion process as well as by atmospheric processes during the early stage of exhaust release and during plume ageing. Combustion efficiency and therefore emission factors of black carbon and NOx were identified to depend mostly on the vessel speed and gross tonnage. Moreover, larger ships, associated with higher engine power, were found to use fuel with higher sulfur content and have higher gas-phase SO2, particulate sulfate, particulate organics, and particulate matter EFs. Despite the independence of EFs of dilution, a significant influence of the ambient wind speed on the particle number and mass EFs was observed that can be traced back to enhanced particle coagulation in the case of slower dilution and suppressed vapour condensation on particles in the case of faster dilution of the emission plume. Atmospheric reactions and processes in ship emission plumes were investigated that include NOx and O3 chemistry, gas-to-particle conversion of NOx and SO2, and the neutralisation of acids in the particle phase through the uptake of ambient gas-phase ammonia, the latter two of which cause the inorganic particulate content to increase and the organic fraction to decrease with increasing plume age. The results allow for us to describe the influences on (or processes in) ship emission plumes quantitatively by parameterisations, which could be used for further refinement of atmospheric models, and to identify which of these processes are the most important ones

An Overview of the Atlas Field Campaign in Morocco (North-West Africa) in September-October 2019

International audienceThe Atlas Experiment, is a MARSU (Marine Atmospheric Science Unravelled: Analytical and mass spectrometric techniques development and application) project field campaign, which took place on the central region of Morocco (Fes-Meknes Region) from September 15th to October 15th, 2019. The goal of the campaign was to collect detailed atmospheric measurements that can be used to evaluate and characterise, for the first time in that African area, the chemical air composition and evaluate the contribution from the local emissions and from the transported air masses from Sahara, Atlantic and Europe. Measurements were performed in two urban sites within the city of Fes (over 1.25 million inhabitants) and one site in the remote area of Michlifen in the Middle Atlas Mountains (2000 m altitude) about 70 km south of Fes city. The deployment of a large set of instrumentation enabled to characterise the aerosols chemical composition in the three sites as well as trace-gases species. The high concentrations measured for a series of pollutants in both sites at the city of Fes indicated that local emissions have a large contribution to the pollution events observed during the campaign. On the other hand, the measurements at the remote site (Mohammed V observatory, AMV) showed that chemical composition at this high-altitude site is influenced by both regional and trans-regional transport of emissions. MARSU project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 69095

An Overview of the Atlas Field Campaign in Morocco (North-West Africa) in September-October 2019

International audienceThe Atlas Experiment, is a MARSU (Marine Atmospheric Science Unravelled: Analytical and mass spectrometric techniques development and application) project field campaign, which took place on the central region of Morocco (Fes-Meknes Region) from September 15th to October 15th, 2019. The goal of the campaign was to collect detailed atmospheric measurements that can be used to evaluate and characterise, for the first time in that African area, the chemical air composition and evaluate the contribution from the local emissions and from the transported air masses from Sahara, Atlantic and Europe. Measurements were performed in two urban sites within the city of Fes (over 1.25 million inhabitants) and one site in the remote area of Michlifen in the Middle Atlas Mountains (2000 m altitude) about 70 km south of Fes city. The deployment of a large set of instrumentation enabled to characterise the aerosols chemical composition in the three sites as well as trace-gases species. The high concentrations measured for a series of pollutants in both sites at the city of Fes indicated that local emissions have a large contribution to the pollution events observed during the campaign. On the other hand, the measurements at the remote site (Mohammed V observatory, AMV) showed that chemical composition at this high-altitude site is influenced by both regional and trans-regional transport of emissions. MARSU project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 69095