Significant Seasonal Change in Optical Properties by atmospheric humic-like substances (HULIS) in Water-Soluble Organic Carbon Aerosols

Formation of substances with humic-like fluorescence properties, upon photoinduced oligomerization of typical phenolic compounds emitted by biomass burning

“…After 24-h irradiation time AcS and VN no longer occurred in solution (Figure 1), but in both irradiated systems two new fluorescence peaks could be noticed at excitation(Ex)/emission(Em) wavelengths, Ex/Em = 200/400 nm and 300/400 nm (Figure 2). These signals correspond to the spectral regions of peak A and peak C of humic substances (Coble, 1996), and the relevant EEM spectra agree well with the fluorescence properties of HULIS (Fan et al, 2016;Han and Kim, 2017). AcS and VN underwent rather fast phototransformation (Figure 1).…”

Comments

“…5. The photochemical degradation experiment can only demonstrate that HULIS could be photoxidized by UV lights, which has already been reported in previous work (Kieber et al, 2007;Zhang et al, 2013). While the oxidation of HULIS in the ambient samples could hardly be reflected.…”

Follow up

“…In Cheng et al (2013), the higher concentrations of WSOC in winter is mainly due to the stronger emissions from household combustion of coal and open burning of waste material. Huang et al (2012) investigated the spatial and seasonal changes of WSOC and other PM2.5 components in Pearl Delta River in China, a similar sampling site as the current work. They inferred that the lower WSOC level in summer is explained by clean marine air masses from the south China sea and the washing effect of frequent rainfall.…”