Variation of airborne DNA mass ratio and fungal diversity in fine particles with day-night difference during an entire winter haze evolution process of Central China.

Airborne fungi are a primary component of bioaerosols and proved to impact human health and climatic change. Deoxyribonucleic acid (DNA) is the essential component of most living organisms with relatively stable physicochemical properties. Little is known about day-night and pollution-episode differences of DNA mass ratio and fungal community in fine particles (PM _2.5 ) during serious winter haze events in China. Here we collected twenty-nine PM _2.5 samples every day and night during an entire winter haze evolution process in a megacity of Central China, Wuhan. DNA extraction and high-throughput sequencing methods were adopted to analyze fungal community. Results showed that mass ratio of DNA in PM _2.5 (R _D/P %) changed with pollution process and showed significant negative correlations with PM _2.5 concentration (r = -0.72, P < 0.05) and temperature (r = -0.74, P < 0.05). R _D/P became lower (4.40 × 10 ^-4 %) after haze episodes than before (7.16 × 10 ^-4 %). R _D/P of night-samples (1.98 × 10 ^-4 -4.97 × 10 ^-4 %) were all lower than those for day-samples (3.05 × 10 ^-4 -9.99 × 10 ^-4 %) for the same period. The fungal species richness became much lower (76 operational taxonomic units (OTUs)) after haze episodes than before (198 OTUs). The species richness of night-samples (119-537 OTUs) were all higher than those of day-samples (71-198 OTUs) for the same period. The OTUs specially owned by night-samples were also more than those by day-samples. Fungal community diversity showed random variations. The fungal community composition of each sample was classified from phylum to genus level. Pathogenic fungi accounted for 8.60% of the entire fungal community. The significantly enriched fungal taxa in the night-sample group (29 taxa) were also much more than that in the day-sample group (9 taxa), which could explain the higher species richness of airborne fungi community in the night during the haze evolution episodes. These findings may serve as an important reference or inspiration to other aerosol studies focusing on human health and behavior of aerosols in the atmosphere.
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