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

Abstract

Dust invasion is an important type of particle pollution in China. During 1 to 6 May in 2011, a dust event was observed in the Yangtze River Delta region (YRD). The highest PM10 (particles up to 10 μ in diameter) concentration reached over 1000 μg m−3 and the visibility was below 3 km. In this study, the Community Multi-scale Air Quality modeling system (CMAQ5.0) coupled with an in-line windblown dust model was used to simulate the formation, spatial and temporal characteristics of this dust event, and analyze its impacts. The threshold friction velocity for loose, fine-grained soil with low surface roughness in the dust model was revised based on Chinese data to improve the model performance. This dust storm broke out in Xinjiang and Mongolia during 28 to 30 April and arrived in the YRD region on 1 May. The transported dust particles contributed to the mean surface layer concentrations of PM10 in the YRD region 78.9% during 1 to 6 May with their impact weakening from north to south due to the removal of dust particles along the path. The dry deposition, wet deposition and total deposition of PM10 in the YRD reached 184.7 kt, 172.6 kt and 357.32 kt, respectively. The dust particles also had significant impacts on optical/radiative characteristics by absorption and scattering. In Shanghai, the largest perturbations of aerosol optical depth (AOD) and irradiance were about 0.8 DU and −130 W m−2, which could obviously influence the radiation balance in this region. The decrease of actinic fluxes impacts future photochemistry. In Shanghai, the negative effects on the NO2 and O3 photolysis could be −35% when dust particles arrived. The concentrations of O3 and OH were reduced by 1.5% and 3.1% 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 the future formation of secondary aerosols in the atmosphere by directly determining the oxidation rate of their precursors. The work of this manuscript is meaningful for understanding the dust emissions in China as well as for the application of CMAQ in Asia. It is also helpful for understanding the formation mechanism and impacts of dust pollution in the YRD.