10 Jun 2022
10 Jun 2022
Status: this preprint is open for discussion.

NH3 spatio-temporal variability over Paris, Mexico and Toronto and its link to PM2.5 during pollution events

Camille Viatte1, Rimal Abeed1, Shoma Yamanouchi2,3, William Porter4, Sarah Safieddine1, Martin Van Damme5,6, Lieven Clarisse4, Beatriz Herrera2,7, Michel Grutter7, Pierre-Francois Coheur4, Kimberly Strong2, and Cathy Clerbaux1,5 Camille Viatte et al.
  • 1LATMOS/IPSL, Sorbonne Université, UVSQ, CNRS, 75252 Paris Cedex 05, France
  • 2Department of Physics, University of Toronto, Toronto, ON M5S 1A7, Canada
  • 3Department of Civil and Mineral Engineering, University of Toronto, Toronto ON M5S 1A4, Canada
  • 4Department of Environmental Sciences, University of California, Riverside, CA 92521, USA
  • 5Université libre de Bruxelles (ULB), Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing (SQUARES), Brussels 1050, Belgium
  • 6BIRA-IASB - Belgian Institute for Space Aeronomy, Brussels 1180, Belgium
  • 7Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México, Mexico City, 04510, Mexico

Abstract. Megacities can experience high levels of fine particulate matter (PM2.5) pollution linked to ammonia (NH3) mainly emitted from agricultural activities. Here, we investigate such pollution in the cities of Paris, Mexico and Toronto, each of which have distinct emission sources, agricultural regulations, and topography. Ten years of measurements from the Infrared Atmospheric Sounding Interferometer (IASI) are used to assess the spatio-temporal NH3 variability over and around the three cities.

In Europe and North America, we determine that temperature is associated with the increase in NH3 atmospheric concentrations with coefficient of determination (r2) of 0.8 over agricultural areas. The variety of the NH3 sources (industry and agricultural) and the weaker temperature seasonal cycle in southern North America induce a lower correlation factor (r2 = 0.5). The three regions are subject to long range transport of NH3, as shown using HYSPLIT cluster back-trajectories. The highest NH3 concentrations measured at the city scales are associated with air masses coming from the surrounding and north-northeast regions of Paris, the south-southwest areas of Toronto, and the southeast/southwest zones of Mexico City.

Using NH3 and PM2.5 measurements derived from IASI and surface observations from 2008 to 2017, annually frequent pollution events are identified in the 3 cities. Wind roses reveal statistical patterns during these pollution events with dominant northeast-southwest directions in Paris and Mexico cities, and the transboundary transport of pollutants from the United-States in Toronto. To check how well chemistry transport models perform during pollution events, we evaluate simulations made using the GEOS-Chem model for March 2011. In these simulations we find that NH3 concentrations are overall underestimated, though day-to-day variability is well represented. PM2.5 is generally underestimated over Paris and Mexico, but overestimated over Toronto.

Camille Viatte et al.

Status: open (until 29 Jul 2022)

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Camille Viatte et al.


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Short summary
Large cities can experience high levels of fine particulate matter (PM2.5) pollution linked to ammonia (NH3) mainly emitted from agricultural activities. Using a combination of PM2.5 and NH3 measurements from in situ instruments, satellite infrared spectrometers, and atmospheric model simulations, we have demonstrated the role of NH3 and meteorological conditions on pollution events occurring over Paris, Toronto, and Mexico cities.