10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Using Single Particle Fluorescence to Characterise Bioaerosols Emissions from Green Waste Composting
ZAHEER AHMAD NASIR, Sean Tyrrel, Cranfield University, MK43 0AL, UK
Abstract Number: 799 Working Group: Bioaerosols
Abstract The potential public health risks from bioaerosols emissions due to increasing waste management facilities, such as open windrow composting, is a growing concern. However, the emissions from such processes are poorly characterised mainly due to the limitations in currently used sampling and analysis methods which offer snapshot data with low temporal resolution. Recent advancement in bioaerosols detection and characterisation technologies, for example, fluorescence spectroscopy offer the capability to monitor bioaerosols in real time and can significantly advance the existing state of knowledge on nature and magnitude of emissions from such facilities. But the broad fluorescence emission detection bands in existing instruments hinder to resolve spectrally integrated signals from the biological fluorophore. The single particle dual excitation multiple fluorescence band systems can offer highly resolved spectral information improving measurement selectivity and classification strategy. This study aims to detect and characterise bioaerosols emissions in real time from green waste composting by using a novel light-induced fluorescence sensor with highly resolved fluorescence intensity measurements (Spectral Intensity Bioaerosol Sensor – SIBS, Droplet Measurement Technologies, USA). The SIBS records a range of data (size, shape, and fluorescence emission across 16 wavelength bands from 288 - 735 nm for two excitation wavelengths (280 nm and 370 nm) on single particles in real time. Four measurements during daytime were carried out between October – December 2016 by using the SIBS downwind of the source at a green waste composting facility. There was considerable temporal variability in the concentration of total and fluorescent particles during different operational activities. Turning of windrows led to higher concentrations of particles in comparison to screening and shredding. There was a shift towards larger size particles during activities. A shift in the MMAD of fluorescent particles was observed during activity and no activity periods. During no activity (no screening and turning) the MMAD for fluorescent particles was 0.66 µm and during activity, the MMAD of fluorescent particles increased to 5.57 µm. In terms of fluorescence spectra, differences were found in the general shapes of the emissions spectra during activity and no activity periods. The SIBS provides additional spectral information in comparison to instruments based on broad emission bands. However, assignment of fluorescence to atmospherically relevant biological fluorophore is challenging and further lab-based studies are needed to interpret the resolved emission spectra recorded by the SIBS. Simultaneously numerical methods and tools are needed to analyse big data to develop discrimination algorithms.