Measurements of coarse mode and primary biological aerosol transmission through a tropical forest canopy using a dual-channel fluorescence aerosol spectrometer

Abstract

Aerosol in the size range 0.8-20 µm was characterized according to optical equivalent diameter, D P , morphology and the presence of biological material, the latter determined by recording fluorescence excited by ultraviolet light pulses at two different wavelengths. Single-particle measurements were performed within and subsequently 5 above a tropical rainforest in Borneo, Malaysia, in June and July 2008. In both locations the aerosol number size distribution exhibited a primary biological aerosol (PBA) mode sized 2 µm <20 µm and much larger in number within the forest than above it, suggesting the PBA originates below the canopy. PBA was observed to dominate the total number at D P >2 µm and possessed a wider morphological range than non-PBA.