Vertical distribution of particulate matter, black carbon and ultra-fine particles in Stuttgart, Germany

The stability of the atmosphere plays a major role in the dispersion of pollutants. The meteorological conditions favoring a high-pressure situation resulting in the formation of inversion layer inhibits pollutant dispersion. The aim of the study was to obtain vertical profiles of meteorological parameters and air pollutants in order to investigate the impact of inversion on the air quality of this city. Vertical profiles help to understand the behaviour of temperature inversion, pollutants and their relationship to each other. The tethered balloon was equipped with in-situ instruments to measure Particulate Matter (PM), Black Carbon (BC), Ultra Fine Particles (UFP) as well as meteorological parameters such as air temperature, relative humidity, wind speed and wind direction of the lower troposphere. The measurements were carried out in “Schlossgarten”, a park area near the city center of Stuttgart. Vertical profiles were obtained by ascending the balloon from ground up to a height of a maximum of 470 m and then descending it back to the ground. One complete sounding (ascent and descent) took around 30–40 min. The measurement campaign took place on 8th and July 9, 2018. 43 soundings were performed during that period. During the measurement campaign, a distinct inversion was observed at nighttime, which trapped the pollutants, hence increasing the pollutant concentration near the ground within the inversion layer. PM, UFP and BC concentrations showed a decreasing trend with increasing altitude but during noon, when the atmosphere was well mixed, the concentrations were relatively constant along with increasing altitude.