Protein amino acids as markers for biological sources in urban aerosols
2016
Abe, Rene Y. | Akutsu, Yoshiaki | Kagemoto, Hiroshi
Biological aerosol particles are recently gaining increased attention, but global estimates of their emissions are unclear. Traditional organic tracers for biological particles have not been able to capture the diversity of biological sources such as residential wood burning. Here, we have analyzed protein content in air particulate matter over a year in a suburban area near Shibuya, in order to identify contributions from biological sources. Aerosols were separated into five size fractions using a high-volume cascade impactor. Amino acid profiles were obtained from acid hydrolysates by high-performance liquid chromatography and were subsequently used in a receptor model for source apportionment. Results show that protein content ranged from 0.5 to 2 % throughout the year in all size fractions. We observed contributions from seasonally variable emission sources such as pollen and fallen leaves in coarse particles, larger than 7 µm, at elevated concentrations during spring and winter. We also found contributions from pollen and fallen leaves in the smallest size fraction, lower than 1.1 µm, after spring. This finding indicates that sources are broken up to smaller particles in the urban environment. Overall, our findings demonstrate that protein content can be used as marker for biological aerosol particles, and that protein amino acid composition can distinguish multiple sources.
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