Measurement of reactive trace gases
Instrumentation
We use and develop modern analytical methods for product identification and quantification at mixing ratios found under remote conditions in the lower troposphere. The analytical equipment comprises online methods such as Real-Time Chemical Ionization Mass Spectrometry (CIMS), GC-MS/FID, the direct laser absorption spectroscopy using the MIRO, as well as methods dedicated to single compounds such as formaldehyde, based on Hantzsch derivatization.
Real-Time Chemical Ionization Mass Spectrometers
Our group has long standing expertise in chemical ionization mass spectrometry using different reagent ions to detect compounds from highly volatile (H3O+ as reagent ion, PTRMS down to intermediate and lower volatility (NH4+ , Br-, I- as reagent ions). Using CIMS techniques we can detect complex mixtures in real-time, without chromatography, thus providing fast time response at sub-ppt limits of detection for a diverse range of compound classes. The rugged and compact design of CIMS makes it an ideal, versatile instrument for sampling air at targeted locations using various airborne and mobile platforms. Recent purchases include the VOCUS coupled to a volatility inlet for aerosol called VIA to measure simultaneously gas- and particle-phase compounds and investigate their partitioning in ambient mixtures.
Low-cost sensors
Our goal is to optimize the performance of low cost sensors and deploy them on mobile and airborne platforms in order to improve both the spatial, horizontal, and vertical coverage of pollutant concentrations in the atmosphere.
Our low-cost sensors include electrochemical sensors that can detect pollutants in the gas-phase including NO, NO2, CO, and OX (O3+NO2) but also optical particle counters that provide the size distribution of aerosol particles. We continuously deploy these sensors onboard unmanned aerial vehicles as well as a Zeppelin NT (Tillmann et al., 2022; Schuldt et al., 2022) to identify the strength of various pollution sources including industries, highways, and city centers around Germany.
Recent work includes our participation in the MesSBAR project where 25 kg of instrumentation are deployed on quadcopters in order to investigate the changing vertical distribution of traffic emissions and compare to atmospheric models.
Finally, we extend the characterization and data quality assurance of these sensors in the lab using a newly developed system called Climatized Atmospheric Calibration flow TUbe System (CACTUS) where we control and modify within seconds the temperature, humidity, and pressure in a SilcoNert coated stainless steel tube to identify and correct for possible sensor interferences.
