Ambient measurement of fluorescent aerosol particles with a WIBS in the Yangtze River Delta of China: potential impacts of combustion-generated aerosol particles

Fluorescence characteristics of aerosol particles in polluted atmosphere were studied using a wideband integrated bioaerosol spectrometer (WIBS-4A) in Nanjing, Yangtze River Delta area of China. We observed strong diurnal and day-to-day variations of fluorescent aerosol particles (FAPs). The ratios of FAPs to total aerosol particles (1–15 μm) increased with increasing particle size and finally reached ~ 100 %. The average number concentrations of FAPs (1–15 μm) detected in the three WIBS measurement channels (FL1: 0.6 cm−3, FL2: 3.4 cm−3, FL3: 2.1 cm−3) were much higher than those observed in forests and rural areas, suggesting that FAPs other than bioaerosols were detected. We found that the number fractions of FAPs were positively correlated with the black carbon mass fraction, especially for the FL1 channel, indicating a large contribution of combustion-generated aerosols. To distinguish bioaerosols from combustion-generated FAPs, we investigated two classification schemes for use with WIBS data. Our analysis suggests a strong size dependence for the fractional contributions of different types of FAPs. In the FL3 channel, combustion-generated particles seem to dominate the 1–2 μm size range while bioaerosols dominate 2–5 μm. The number fractions of combustion-generated particles and non-combustion-generated particles were ~ 11 % and ~ 5 %, respectively