Ammonia in Paris derived from ground-based open-path and satellite observations

Ammonia (NH3) is an air pollutant mainly emitted from the agriculture sector with an increasing part from traffic that is highly uncertain in urban areas. NH3 is a highly reactive gas capable of forming fine particulate matter which are harmful for human health. Monitoring NH3 is therefore essential, especially in urban areas such as in Paris, where particulate pollution episodes are observed almost every spring and often associated with emissions from agricultural activities in the surrounding areas.

Recently, Viatte et al. (2023) analyzed 2.5-years of NH3 observations derived from a miniDOAS (Diffential Optical Absorption Spectroscopy) ground-based remote sensing instrument (figure a) and from IASI/Metop observations (figure b). They quantified, for the first time, temporal variabilities (from interannual to diurnal) of NH3 in Paris. NH3 concentrations derived from the miniDOAS instrument located at the QUALAIR super-site (40 meters above ground level, in the Paris city-center, is in relatively good agreement (R>0.70) with the IASI morning NH3 concentrations.

The NH3 weekly cycle observed over 2.5-years of measurements from the ground-based miniDOAS and the IASI satellite observations shows relatively low NH3 concentrations on Saturday and Sunday (figure c), which suggests that ammonia is also controlled by traffic-related emissions.

In Paris, the diurnal cycle of NH3 concentrations is very similar to the one of NO2 (figure d), with morning enhancements coincident with intensified road traffic. NH3 evening enhancements synchronous with rush hours are also monitored in winter and fall. NH3 concentrations measured during the weekends are consistently lower than NH3 concentrations measured during weekdays in summer and fall. This is a further evidence of a significant traffic source of NH3 in Paris.

a) miniDOAS installed at QUALAIR, b) IASI satellite, c) weekly cycles of NH3 concentrations measured in fall by the miniDOAS and IASI instruments in Paris, and d) diurnal variability of NH3 (upper panels) and NO2 (lower panels) concentrations measured by the miniDOAS and Airparif in (μg.m-3) averaged by seasons using 2.5-years of measurements in Paris. The diurnal variability of NH3 and NO2 are shown in blue lines when considering all days, in red lines for weekdays, and in black lines for weekends.   

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