Ammonia (NH3) is an atmospheric pollutant mainly emitted from the agricultural sector (animal housing buildings, manure storage and management, and manure and fertilizer applications) with an uncertain part from traffic in urban areas. Ammonia emissions are projected to increase in the future due to population growth, rise in food demand, and climate change. Excess atmospheric ammonia/nitrogen deposition is likely to damage ecosystems, causing eutrophication and acidification. NH3 is also a precursor of secondary inorganic aerosols in the sub-micron size fraction, which are very harmful to public health. Monitoring atmospheric NH3 concentrations is essential for improving air quality models in terms of spatial and temporal (diurnal, seasonal) variabilities and gas/particle inter-conversion, in order to better quantify NH3 emissions and pollution events. Despite its environmental impacts, measurements of atmospheric ammonia concentrations are not yet subject to regulation. Ammonia observations are very challenging from a metrological point of view (ammonia is a polar, sticky, reactive and highly water-soluble molecule, resulting in strong interactions with sampling systems). In France, an IPSL-lead consortium, called AMICA (Analysis of Multi-Instrumental Concentrations of Ammonia) formed in 2021, conducted an intensive measurement campaign over the Paris megacity in autumn 2024 called AMICA 2024. Ammonia measurements continued throughout the winter, spring, and summer in 2025 at the three IPSL sites: QUALAIR, LISA, and SIRTA.

This project aims to better monitor atmospheric ammonia concentrations and derive city emissions of NH3 preferentially from the autumn period. It is of high scientific relevance since the new European directive on ambient air quality now include measurements of atmospheric ammonia concentrations for regulation.

In this internship, the candidate will analyze and interpret the dataset collected over several years (including the AMICA 2024 campaign), which consists of many innovative measurement techniques (chemical samplers, open-path, sensors, and emerging technology-based). First, the candidate will study the comparisons of NH3 concentrations measured at the different locations between urban and semi-urban sites in order to quantify NH3 sources in the Greater Paris urban area, diurnal variability, and particle conversion for atmospheric model evaluation. Second, the candidate will analyse NH3 observations derived from IASI satellites, and OASIS ground-based remote sensing observatory in order to explore the added-value between NH3 integrated columns and surface concentrations of atmospheric ammonia in the Paris region at different time scales.

The candidate will take advantages of this multi-actors (13 research laboratories and institutions) campaigns to enlarge his interests in many aspects (metrology, data analysis, satellite observations, …) of atmospheric researches.