Project description: Analysing trace gases in an inner-Alpine region

Even if they only occur in very small quantities, volatile organic compounds (VOCs) determine the air quality of our atmosphere. Ground-level ozone, which affects our health in high concentrations, is formed from VOCs and nitrogen oxides (_NOx) under the influence of sunlight. In addition, VOCs also influence our climate by having a decisive influence on the formation of the greenhouse gas ozone (_O3) and the formation of the organic proportion of particles in the air (aerosols). Current laboratory experiments show how new particles are formed from individual "gaseous" VOCs through chemical conversion. In our atmosphere, water vapour condenses exclusively on special aerosol particles, so-called cloud condensation nuclei, and this is the only way a cloud drop can form. VOCs therefore influence cloud cover and have an impact on our climate. Although the chemical and physical mechanisms of these processes are investigated in laboratory experiments, measurements in the real atmosphere cannot be replaced.

The aim of this project is to create a unique data set of the composition and source strength of VOCs in a rural, inner-Alpine area in collaboration with scientists from several research institutions in Tyrol and Salzburg and the pupils and teachers of the BORG Mittersill and the BG/BRG Zell am See.

For this purpose, the schools will become modern air quality measuring stations equipped with a proton exchange reaction time-of-flight mass spectrometer (PTR-ToF-MS) for highly time-resolved measurements of VOCs, a weather station including an ultrasonic anemometer and standard measuring devices for _O3, _NOx and CO. The high time resolution of the PTR-ToF-MS and the ultrasonic anemometer enables the use of the eddy-covariance method to determine the flux of VOCs. This makes it possible to determine the emission strength of these compounds in the immediate vicinity of the measuring station. This measurement method has been used in recent years, especially in various ecosystems (coniferous forest, deciduous forest, meadows, etc.), to provide experimental data that allow the global emission levels of biogenic VOCs to be estimated. Globally, the contributions of biogenic VOC sources are much larger than those of anthropogenic sources. There are hardly any measurements for areas with significant anthropogenic influences in the mountains.

The results of the eddy covariance measurement are compared with similar measurements at the Institute of Atmospheric and Cryospheric Sciences at UNI Innsbruck. This allows the differences in concentration, composition and source strength of trace gases between an urban, inner-Alpine area (Innsbruck: 120,000 inhabitants) along a main traffic route and a rural, inner-Alpine area (Mittersill: 5,000 inhabitants; Zell am See 10,000 inhabitants) along a secondary traffic route to be worked out.

In a second approach, "VOC fingerprints" are determined from known pollutant sources (motor vehicle traffic, biomass combustion, domestic fires, etc.) by taking air samples directly at these sources and analysing them with the PTR-ToF-MS. The outdoor air measurements are then analysed with regard to these fingerprints. This allows the proportion of individual sources in the total pollutant load to be determined.

At the two locations Mittersill and Zell am See, one measurement campaign takes place in summer and one in winter in order to record the seasonal differences. The pupils will become scientific assistants who will monitor the measuring station on a daily basis and assist with the necessary maintenance work.

At least once per measurement period, the spatial representativeness of the point measurement for the entire valley is checked on a "Golden Day" (with suitable meteorological conditions). For this purpose, 2 students will set off on a small research expedition. Each team will fill an evacuated canister with outside air at suitable locations in their home communities. The filling will be carried out by all 20 teams at exactly the same pre-agreed time. This will provide a snapshot of the air composition throughout the valley and evaluate the representativeness of point measurements.

Project description: Analysis of Trace Gases in an inner-Alpine Region

Even though volatile organic compounds (VOCs) occur only in very small quantities in our atmosphere, they determine air quality and air chemistry.

Ground-level ozone, which in high concentrations affects our health, is produced from VOCs and nitrogen oxides (_NOx) whenever exposed to sunlight. In addition, VOCs also affect our climate since ozone (_O3) is a greenhouse gas and also through the formation of the organic fraction of particles in air (aerosols). Recent laboratory experiments show how individual precursor VOC-gases form new particles after being chemically processed in the atmosphere. In our atmosphere, water vapour condenses only on special aerosol particles called cloud condensation nuclei and forms cloud droplets. Therefore, VOCs affect cloud cover and our climate. Although in laboratory experiments, the chemical and physical mechanisms of this process are examined, measurements in the real environment cannot be replaced.

In this project a collaboration of scientists from several research institutions in Tirol and Salzburg and the students and teachers of the BORG Mittersill and the BG / BRG Zell am See, will create a unique data set of the composition and source strength of trace gases in a rural, inner-Alpine region.

The schools will become modern air quality monitoring stations, equipped with a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) for highly time-resolved measurements of VOCs, a weather station, including a sonic anemometer and standard instruments for _O3, _NOx and CO measurements. The high time resolution of the PTR-ToF-MS and the sonic anemometer allows the application of the eddy-covariance method for VOC-flux measurements. Using this method the emission source strength of VOCs in the vicinity of the station can be determined.

In recent years this measuring method has been used, especially on different ecosystem levels (coniferous forest, deciduous forest, meadows, etc.) to provide a unique data for estimating global emissions of biogenic VOCs. Globally, the contributions of biogenic VOC sources are much larger than from anthropogenic sources. Rural areas with significant anthropogenic emissions in the mountains have only rarely been investigated so far.

The results of the eddy-covariance measurements in this rural inner-Alpine region (Mittersill: population of 5.000 ; Zell am See population of 10.000) will be compared with similar measurements at the Institute of Atmospheric and Cryospheric Sciences of the LFU Innsbruck (Innsbruck population of 120.000) along a main traffic route.

In a second approach, "VOC-fingerprints" of known pollution sources (traffic related, biomass burning, domestic heating,...) are determined by taking samples directly at the source location. The outdoor air measurements are then examined for VOC-fingerprints. Thus, the contribution of individual sources to the total pollution load can be estimated. At both measurement sites, Mittersill and Zell am See one measurement campaign will take place in summer and one in winter to capture seasonal changes. The students will become science assistants who supervise the air monitoring station on a daily basis and assist during necessary maintenance.

At least once per measurement period, the spatial representativeness of the point measurements for the whole valley will be examined on a "Golden Day" (with appropriate meteorological conditions). For this purpose, pairs of students will start for a small research expedition. Each team will fill an evacuated canister at appropriate points in their home communities with outside air. Each team will fill its canister at exactly the same time. This will provide a snapshot picture of the trace gas distribution in the entire valley atmosphere and helps to evaluate the geographic coverage of the point like air monitoring station.