Abstract
Abstract. The detection of primary biological material in submicron aerosol by means of thermal desorption/electron impact ionization aerosol mass spectrometry was investigated. Mass spectra of amino acids, carbohydrates, small peptides, and proteins, all of which are key building blocks of biological particles, were recorded in laboratory experiments. Several characteristic marker fragments were identified. The intensity of the marker signals relative to the total organic mass spectrum allows for an estimation of the content of primary biological material in ambient organic aerosol. The developed method was applied to mass spectra recorded during AMAZE-08, a field campaign conducted in the pristine rainforest of the central Amazon Basin, Brazil, during the wet season of February and March 2008. The low abundance of identified marker fragments places upper limits of 7.5% for amino acids and 5.6% for carbohydrates on the contribution of primary biological aerosol particles (PBAP) to the submicron organic aerosol mass concentration during this time period. Upper limits for the absolute submicron concentrations for both compound classes range from 0.01 to 0.1 μg m−3. Carbohydrates and proteins (composed of amino acids) make up for about two thirds of the dry mass of a biological cell. Thus, our findings suggest an upper limit for the PBAP mass fraction of about 20% to the submicron organic aerosol measured in Amazonia during AMAZE-08.
Highlights
Primary biological aerosol particles (PBAP) are suggested to play an important role in atmospheric aerosol processes and cloud formation (Jaenicke, 2005; Jaenicke et al, 2007; Mohler et al, 2007; Deguillaume et al, 2008; Spracklen et al, 2010)
Their re3s1ults show that local production of biogenic secondary organic aerosol dominated the submicron organic mass concentration during times with low sulfate to organic ratios
We presented a method to estimate the mass fraction of primary biological aerosol particles in ambient organic aerosol from aerosol mass spectrometer data
Summary
Primary biological aerosol particles (PBAP) are suggested to play an important role in atmospheric aerosol processes and cloud formation (Jaenicke, 2005; Jaenicke et al, 2007; Mohler et al, 2007; Deguillaume et al, 2008; Spracklen et al, 2010). Since proteins are composed of large chains of amino acids, on average amino acids and carbohydrates contribute about 60 to 80 % to the dry mass of a biological cell It has been demonstrated in laboratory experiments (Diehl et al, 2001, 2002; von Blohn et al, 2005; Iannone et al, 2011) and field studies (Pratt et al, 2009) that PBAP can act as efficient ice nuclei (IN), model studies indicate that on a global scale PBAP account for less than one percent of the global IN fraction, while dust (>80 %) and soot dominate the IN (Hoose et al, 2010).
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