Source, transport and impacts of a heavy dust event in the Yangtze River Delta, China, in 2011

摘要

Dust invasion is an important type of particle pollution in China. During 1to 6 May in 2011, a dust event was observed in the Yangtze River Deltaregion (YRD). The highest PM₁₀ (particles up to 10 μ in diameter) concentration reached over 1000 μg m?3and the visibility was below 3 km. In this study, the CommunityMulti-scale Air Quality modeling system (CMAQ5.0) coupled with an in-linewindblown dust model was used to simulate the formation, spatial andtemporal characteristics of this dust event, and analyze its impacts. Thethreshold friction velocity for loose, fine-grained soil with low surfaceroughness in the dust model was revised based on Chinese data to improve themodel performance. This dust storm broke out in Xinjiang and Mongolia during28 to 30 April and arrived in the YRD region on 1 May. The transported dustparticles contributed to the mean surface layer concentrations of PM₁₀in the YRD region 78.9% during 1 to 6 May with their impact weakeningfrom north to south due to the removal of dust particles along the path. Thedry deposition, wet deposition and total deposition of PM₁₀ in the YRDreached 184.7 kt, 172.6 kt and 357.32 kt, respectively. The dust particles alsohad significant impacts on optical/radiative characteristics by absorptionand scattering. In Shanghai, the largest perturbations of aerosol optical depth (AOD) and irradiancewere about 0.8 DU and ?130 W m?2, which could obviously influence theradiation balance in this region. The decrease of actinic fluxesimpacts future photochemistry. In Shanghai, the negative effects on theNO₂ and O₃ photolysis could be −35% when dust particlesarrived. The concentrations of O₃ and OH were reduced by 1.5% and3.1% in the whole of China, and by 9.4% and 12.1% in the YRD region,respectively. Such changes in O₃ and OH levels can affect thefuture formation of secondary aerosols in the atmosphere by directly determining theoxidation rate of their precursors. The work of this manuscript ismeaningful for understanding the dust emissions in China as well as for theapplication of CMAQ in Asia. It is also helpful for understanding the formationmechanism and impacts of dust pollution in the YRD.