WRF/CHEM modeling of impacts of weather conditions modified by urban expansion on secondary organic aerosol formation over Pearl River Delta--颗粒学报PARTICUOLOGY

Wang, X., Wu, Z., & Liang, G. (2009). WRF/CHEM modeling of impacts of weather conditions modified by urban expansion on secondary organic aerosol formation over Pearl River Delta. Particuology, 7(5), 384–391. https://doi.org/10.1016/j.partic.2009.04.007

WRF/CHEM modeling of impacts of weather conditions modified by urban expansion on secondary organic aerosol formation over Pearl River Delta

Xuemei Wang ^a *, Zhiyong Wu ^a, Guixiong Liang ^b

a School of Environmental Science and Engineering, Sun Yat-sen University, 135 Xingang Awest Road, Guangzhou 510275, China
b Guangzhou Environmental Monitor Center, Guangzhou 510010, China

10.1016/j.partic.2009.04.007

Volume 7, Issue 5, October 2009, Pages 384-391

Received 5 January 2009, Revised 19 April 2009, Accepted 21 April 2009, Available online 11 August 2009.

E-mail: eeswxm@mail.sysu.edu.cn

Highlights

Abstract

In this paper, the online Weather Research and Forecasting and Chemistry (WRF/CHEM) model, coupled with urban canopy (UCM) and biogenic-emission models, is used to explore impacts of urban expansion on secondary organic aerosols (SOA) formation. Two scenarios of urban maps are used in WRF/CHEM to represent early 1990s (pre-urbanization) and current urban distribution in the Pearl River Delta (PRD). Month-long simulation results using the above land-use scenarios for March 2001 show: (1) urbanization can increase monthly averaged temperatures by about 0.63 °C, decrease monthly averaged 10-m wind speeds by 38%, increase monthly averaged boundary-layer depths by 80 m, and decrease monthly averaged water mixing ratio by 0.2 g/kg. (2) Changes in meteorological conditions can result in detectable concentration changes of NO_x, VOC, O₃ and NO₃ radicals. Urbanization decreases surface NO_x and VOC concentrations by a maximum of 4 ppbv and 1.5 ppbv, respectively. Surface O₃ and NO₃ radical concentrations over major cities increase by about 2–4 ppbv and 4–12 pptv, respectively; areas with increasing O₃ and NO₃ radical concentrations generally coincide with the areas of temperature increase and wind speed reduction where NO_x and VOC decrease. (3) Urbanization can induce 9% increase of SOA in Foshan, Zhongshan and west Guangzhou and 3% decrease in Shenzhen and Dongguan. Over PRD major cities, SOA from Aitken mode reduces by 30% but with more than 70% SOA from accumulate mode. Urbanization has stronger influence on SOA formation from Aitken mode. (4) Over the PRD, 55–65% SOA comes from aromatics precursors. Urbanization has strongest influence on aromatics precursors to produce SOA (14% increase), while there is less influence on alkane precursors. Alkene precursors have negative contribution to SOA formation under urbanization situation.

Graphical abstract

Keywords

Secondary organic aerosol; Urban expansion; WRF/CHEM model

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