Abundance of organosulfates derived from biogenic volatile organic compounds: Seasonal and spatial contrasts at four sites in China

Atmospheric organosulfates (OSs) derived from biogenic volatile organic compounds (BVOCs) encode chemical interaction strength between anthroposphere and biosphere. We report BVOC-derived OSs in the summer of 2016 and the winter of 2017 at four locations in China (i.e., Hong Kong (HK), Guangzhou (GZ), Shanghai (SH), and Beijing (BJ)). The spatial coverage of three climatic zones from the south to the north in China is accompanied with a wide range of aerosol inorganic sulfate (4.9–13.8 μg/m³). We employed a combined targeted and untargeted approach using high-performance liquid chromatography-Orbitrap mass spectrometry to quantify/semi-quantify ~200 OSs and nitrooxy OSs derived from four types of precursors, namely C₂-C₃ oxygenated VOCs, isoprene, monoterpenes (MT), and sesquiterpenes (ST). The seasonal averages of the total quantified OSs across the four sites are in the range of 201–545 (summer) and 123–234 ng/m³ (winter), with the isoprene-derived OSs accounting for more than 80% (summer) and 57% (winter). The C_2–3 OSs and isoprene-derived OSs share the same seasonality (summer >winter) and the same south-north spatial gradient as those of isoprene emissions. In contrast, the MT- and ST-derived OSs are of either comparable abundance or slightly higher abundance in winter at the four sites. The spatial contrasts for MT- and ST-derived OSs are not clearly discernable among GZ, SH, and BJ. HK is noted to have invariably lower abundances of all groups of OSs, in line with its aerosol inorganic sulfate being the lowest. These results indicate that BVOC emissions are the driving factor regulating the formation of C_2–3 OSs and isoprene-derived OSs. Other factors, such as sulfate abundance, however, play a more important role in the formation of MT- and ST-derived OSs. This in turn suggests that the formation kinetics and/or pathways differ between these two sub-groups of BVOCs-derived OSs.