Mass concentration measurements of autumn bioaerosol using low-cost sensors in a mature temperate woodland free-air carbon dioxide enrichment (FACE) experiment: investigating the role of meteorology and carbon dioxide levels

[摘要] Forest environments contain a wide variety of airborne biological particles(bioaerosols), including pollen, fungal spores, bacteria, viruses, plantdetritus, and soil particles. Forest bioaerosol plays a number of importantroles related to plant and livestock health, human disease andallergenicity, and forest and wider ecology and are thought to influencebiosphere–atmosphere interactions via warm and cold cloud formation. Despitethe importance of bioaerosols, there are few measurements of forest aerosol,and there is a lack of understanding of how climate change will affectforest bioaerosol in the future. We installed low-cost optical particle counters (OPCs) to measure particlesin the size range between 1 and 10  µ m (PM 10 –PM 1 ) for aperiod of 2 months in autumn 2018 at the Birmingham Institute of ForestResearch (BIFoR) free-air carbon dioxide enrichment (FACE) facility. In thepaper, we propose that the PM 10 –PM 1 (particulate matter) metric is a good proxy forbioaerosols because of the bioaerosol representative size range, thelocation of the study site (a woodland in a rural location), the fieldmeasurement taking place during the season of peak fungal activity, and thelow hygroscopicity of the particles measured. The BIFoR FACE facilityfumigates three 700 m 2 areas of the forest with an additional 150 ppmCO 2 above ambient levels with minimal impacts on other potential environmentaldrivers such as temperature, humidity, and wind. This experimental set-upenabled us to investigate the effect of environmental variables, includingelevated CO 2 ( e CO 2 ), on bioaerosol proxy concentrations and toevaluate the performance of the low-cost OPCs in a forested environment. Operating the low-cost OPCs during autumn 2018, we aimed to capturepredominantly the fungal bioaerosol season. Across the experimentalduration, the OPCs captured both temporal and spatial variation inbioaerosol concentrations. Aerosol concentrations were affected by changingtemperatures and wind speeds but, contrary to our initial hypothesis, notby relative humidity. We detected no effect of the e CO 2 treatment ontotal bioaerosol concentrations, but a potential suppression of high-concentration bioaerosol events was detected under e CO 2 . In-canopyatmospheric dispersion modelling indicates that the median spore dispersiondistance is sufficiently small that there is little mixing between treatmentand control experiments. Our data demonstrate the suitability of low-costOPCs, interpreted with due caution, for use in forests and so opens thepossibility of forest bioaerosol monitoring in a wider range of habitats toa wider range of researchers at a modest cost.

[学科分类] 大气科学