The Contribution of Bioaerosols to the Organic Carbon Budget of the Atmosphere

Abstract

Primary Biological Aerosol Particles (PBAPs), commonly known also as bioaerosols, are airborne particles that include mainly bacteria, fungi spores, pollen, viruses, microorganisms or even leaf debris and usually dominate the aerosol mass over remote forested regions. The atmospheric cycle of PBAPs is here parameterized in a state-of-the-art global 3-D chemistry-transport model by taking into account their primary emissions as well as their chemical aging during the long-range transport in the atmosphere. Different ecosystems are used to parameterize the respective flux rates of PBAPs considering bacteria, fungal spores and pollen, and using meteorological parameters in order to account for fluxes seasonal variation. Bioaerosols are assumed to be emitted as 50 % hydrophilic particles but they can be transferred to the soluble mode via atmospheric oxidation, changing thus their physical properties and their atmospheric lifetime. The global annual flux of PBAPs to the atmosphere calculated by the model equals about 123 Tg yr−1 (47.5 Tg-C yr−1) and the atmospheric burden is calculated to equal about 791 Gg. These calculated emissions largely depend on the assumed size distribution and is comparable to the amount of primary particulate organic carbon injected into the atmosphere by anthropogenic emissions.