Abstract
Abstract. In this paper bioaerosol measurements conducted with the Waveband Integrated Bioaerosol Sensor mark 4 (WIBS-4) are presented. The measurements comprise aerosol chamber characterization experiments and a one-year ambient measurement period at a semi-rural site in South Western Germany. This study aims to investigate the sensitivity of WIBS-4 to biological and non-biological aerosols and detection of biological particles in the ambient aerosol. Several types of biological and non-biological aerosol samples, including fungal spores, bacteria, mineral dust, ammonium sulphate, combustion soot, and fluorescent polystyrene spheres, were analyzed by WIBS-4 in the laboratory. The results confirm the sensitivity of the ultraviolet light-induced fluorescence (UV-LIF) method to biological fluorophores and show the good discrimination capabilities of the two excitation wavelengths/detection wavebands method applied in WIBS-4. However, a weak cross-sensitivity to non-biological fluorescent interferers remains and is discussed in this paper. All the laboratory studies have been undertaken in order to prepare WIBS-4 for ambient aerosol measurements. According to the one-year ambient aerosol study, number concentration of fluorescent biological aerosol particles (FBAP) show strong seasonal and diurnal variability. The highest number concentration of FBAP was measured during the summer term and decreased towards the winter period when colder and drier conditions prevail. Diurnal FBAP concentrations start to increase after sunset and reach maximum values during the late night and early morning hours. On the other hand, the total aerosol number concentration was almost always higher during daytime than during nighttime and a sharp decrease after sunset was observed. There was no correlation observed between the FBAP concentration and the meteorological parameters temperature, precipitation, wind direction and wind speed. However, a clear correlation was identified between the FBAP number concentration and the relative humidity. Humidity-controlled release mechanisms of some fungal spore species are discussed as a possible explanation.
Highlights
Primary biological aerosol particles (PBAP) basically consist of particles that are derived from living organisms, including microorganisms, dispersal units and fragments of all varieties of living things and they can be either dead or alive (Despres et al, 2012)
We present online measurements of ambient fluorescent biological aerosol particles (FBAP) by using the latest version of the WIBS instrument suite (WIBS-4), which is based on the UV light-induced fluorescence (UV-LIF) method
The experiments were conducted at the stainless steel aerosol chamber NAUA at the Institute for Meteorology and Climate Research in Karlsruhe, Germany (IMK-AAF, Karlsruhe Institute of Technology (KIT))
Summary
Primary biological aerosol particles (PBAP) basically consist of particles that are derived from living organisms, including microorganisms, dispersal units and fragments of all varieties of living things and they can be either dead or alive (Despres et al, 2012). PBAP are potentially important for cloud formation processes because they have the potential to act as effective cloud condensation nuclei (CCN) (Petters and Kreidenweis, 2007) and heterogeneous ice nuclei (IN) at temperatures as warm as −2 ◦C (Diehl et al, 2001, 2002). They affect public health and play important roles in further atmospheric processes (Poschl, 2005). There are not enough studies yet about the abundance of PBAP in the atmosphere, their release and dispersal mechanisms, and their role in atmospheric aerosolcloud processes.
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