Yanfen Lin

Mixing of Asian dust with pollution aerosol and the transformation of aerosol components during the dust storm over China in spring 2007

NO3 and NH4 decreased owing to the dilution of the local pollution by the invaded dust. The western dust contained relatively low anthropogenic aerosols, and it mainly derived from the Taklimakan Desert, a paleomarine source. The northwestern dust had a considerable chemical reactivity and mixing with sulfur precursors emitted from the coal mines on the pathway of the long‐range transport of dust. The northeastern dust reached Shanghai with high acidity, and it became the mixed aerosol with the interaction among dust, local pollutants, and sea salts. Comparison of the speciation of the water‐soluble ions on both nondust and dust days at all sites illustrated the evolution of major ion species from different dust sources during the long‐range transport of dust. The mixing mechanisms of the dust with the pollution aerosol on the local, medium‐range, and long‐range scale revealed from this study would improve the understanding of the impacts of Asian dust on the regional/global climate change.

Mixing of dust with pollution on the transport path of Asian dust — Revealed from the aerosol over Yulin, the north edge of Loess Plateau

Both PM(2.5) and TSP were monitored in the spring from 2006 to 2008 in an intensive ground monitoring network of five sites (Tazhong, Yulin, Duolun, Beijing, and Shanghai) along the pathway of Asian dust storm across China to investigate the mixing of dust with pollution on the pathway of the long-range transport of Asian dust. Mineral was found to be the most loading component of aerosols both in dust event days and non-dust days. The concentrations of those pollution elements, As, Cd, Pb, Zn, and S in aerosol were much higher than their mean abundances in the crust even in dust event days. The high concentration of SO(4)(2-) could be from both sources: one from the transformation of the local emitted SO(2) and the other from the sulfate that existed in primary dust, which was transported to Yulin. Na(+), Ca(2+), and Mg(2+) were mainly from the crustal source, while NO(3)(-) and NH(4)(+) were from the local pollution sources. The mixing of dust with pollution aerosol over Yulin in dust event day was found to be ubiquitous, and the mixing extent could be expressed by the ratio of NO(3)(-)/Al in dust aerosol. The ratio of Ca/Al was used as a tracer to study the dust source. The comparison of the ratios of Ca/Al together with back trajectory analysis indicated that the sources of the dust aerosol that invaded Yulin could be from the northwestern desert in China and Mongolia Gobi.

Impact of mixed anthropogenic and natural emissions on air quality and eco-environment—the major water-soluble components in aerosols from northwest to offshore isle

Based on more than 300 atmospheric TSP and PM2.5 samples collected at five sites over China in 2007 and 2008, characteristics, sources, and interactions of the major water-soluble species were investigated for a better understanding of their role in urban air quality and offshore eco-environment. From the dust source regions in Northwestern China to an offshore isle over the East China Sea, concentration levels and fine/coarse particle distributions of five representative water-soluble components were well elucidated, reflecting the distinct differences of geo-history, location, and present economic situation among the target areas. NO3−/SO42− mass ratios reflected significant divergence of motorization among the studied regions. Specifically, a case study during the World Car-Free Day proved that traffic restriction measures could indeed help mitigate the aerosol species formed from vehicle emissions. Investigation on the molar concentration stoichiometry and mass percentage variations of particulate NO3−, SO42−, and NH4+ revealed that NH3 was a driving factor in the formation of major secondary water-soluble ions in atmospheric fine particles over urban areas. Based on the prevailing wind analysis, observation over an offshore isle clearly indicated the influence of the relative strength of anthropogenic sources and ocean-related natural sources on the formation and size distribution of MSA (methanesulfonic acid), a major water-soluble organic component in aerosol. Annual dry deposition flux of particulate NO3− and NH4+ over the East China Sea was estimated based on the strength of an improved calculation formula. Reductive nitrogen was found to be the major form of the deposited atmospheric inorganic nitrogen, accounting for ~ 69% of the total nitrogen depositions.