Atmospheric Composition

Abstract/Description

Bioaerosols are an integral and ubiquitous component of the atmospheric aerosol. Despite this, they have received little attention in the atmospheric sciences for many years. Recently, however, interest in bioaerosols has been stimulated by growing evidence that bioaerosols are not only a health concern, but may also play an important role in cloud formation. At the same time, automated and on-line instrumentation for bioaerosol research has emerged, promising new insights into the abundance and distribution patterns of bioaerosols by providing higher time resolution and less labor-intensive measurements. In particular, measurements at a mountain station in atmospheric regions where clouds form are rare.

At the Sonnblick Observatory we have installed a SwisensPoleno Jupiter next to a traditional Hirst-type pollen trap since April 2023. The SwisensPoleno Jupiter is an online aerosol monitor that obtains scattered light, two holographic images and fluorescence signals of individual aerosol particles. Using the Hirst pollen trap, particles are collected on a sticky tape and later manually examined under a microscope to visually identify pollen and fungal spores. This data is used to validate the automatic measurements.

In this presentation we will focus our discussion on selected time periods where FLEXPART simulations indicate long-range transport of air masses, e.g. from the Saharan region. For these periods, we have taken a closer look at the fluorescence properties of the particles together with the holographic images. In a previous laboratory study, we obtained representative fluorescence signals for three classes of bioaerosol particles: pollen, fungal spores and plant debris. We use these data in combination with pollen and spore counts from the Hirst trap to characterize the selected events and to contrast and compare them with periods of stagnant conditions and stronger local influence.

Abstract/Description

Innsbruck, an urban area nestled in a mountainous region, presents unique challenges for atmospheric research due to its complex orography. This inherent complexity complicates the accurate quantification of emission sources, particularly greenhouse gases such as methane. Recognizing the importance of methane in climate change and its associated uncertainties in alpine environments, the Innsbruck Atmospheric Observatory (IAO) at the University of Innsbruck has implemented a long-term monitoring strategy employing the eddy covariance measurement technique. As a Top-Down approach, these measurements provide direct emission estimates that complement and validate conventional Bottom-Up emission inventories, which often rely on assumptions about activity data and emission factors.
Our multi-year dataset, combining continuous observations of methane, carbon dioxide, and nitrogen oxides with campaign-based non-methane volatile organic compound (NMVOC) flux measurements, enables a detailed characterization of urban methane emissions. We identify pre-flush operations and inefficient gas furnaces as the dominant methane sources, with fluxes showing a strong correlation with ethane and a negative temperature dependence. The observed ethane-to-methane ratio (~5%) aligns with the composition of the regional gas supply.
The estimated 20-year global warming potential (GWP) of methane emissions from the residential, commercial, and public sectors could be as high as 20–30% relative to CO₂ emissions, underlining the significance of unburned methane as a climate-relevant pollutant. Our findings highlight the potential for immediate emission reductions through the transition from gas furnaces to heat pumps, offering a clear path for mitigating methane emissions in urban areas. In this regard, the study emphasizes the value of long-term flux measurements in alpine urban environments for improving regional climate models and guiding effective mitigation strategies.