Reconstructed Light Extinction Coefficients of Fine Particulate Matter in Rural Guangzhou, Southern China

Abstract

A one-year campaign was conducted to collected PM 2.5 samples in the rural area of Guangzhou, the largest megacity in South China, from March 2012 to February 2013. Mass concentration of PM 2.5 , carbonaceous fractions (i.e., organic carbon (OC) and elemental carbon (EC)) and 6 water-soluble ions were analyzed. Light extinction coefficient (b ext ) of fine particulate matter was reconstructed using the revised IMPROVE formula at the site. (NH 4 ) 2 SO 4 (AS) made a dominant contribution to the light extinction budget, accounting for 61.3% (155.6 ± 108.5 Mm -1 ) annually, with highest in autumn (68.0%) and lowest in winter (55.2%). Organic matter (OM) was the second largest contributor accounting for 20.5% (52.2 ± 42.7 Mm -1 ) with highest in winter (23.4%) and lowest in spring (18.0%). The relationship between reconstructed b ext and measured b ext was investigated under the influence of seasonality, visibility and PM 2.5 concentration. We found that b ext could be reconstructed using revised IMPROVE formula in high PM 2.5 days (threshold value of ~60 µg m -3 ). On other hand, the performance of formula was unsatisfactory for b ext reconstruction of in low PM 2.5 days, when meteorological conditions could have significant impact on visibility.

Chemical Composition of PM2.5 and its Impact on Visibility in Guangzhou, Southern China

“…Given both the total loading values and their large extinction coefficients, the most important species include secondary water-soluble inorganic aerosol (e.g., ammonium sulfate and ammonium nitrate), organic carbon (OC), and elemental carbon (EC) (Cheung et al, 2005;Jung et al, 2009a;Tao et al, 2009). The IMPROVE Algorithms have been proposed to estimate the light extinction coefficient based on aerosol mass and chemical compositions (Sisler and Malm, 2000;Pitchford et al, 2007), and have been widely used to reconstruct light extinction coefficient and study contributions from individual aerosol chemical components (Cheung et al, 2005;Jung et al, 2009a;Tao et al, 2009;Cao et al, 2012;Han et al, 2012;Wang et al, 2015;Chen et al, 2016).…”

Increased Aerosol Extinction Efficiency Hinders Visibility Improvement in Eastern China

“…Furthermore, to quantitatively understand the relative contribution from different chemical components to aerosol extinction at the SORPES station, the Interagency Monitoring of Protected Visual Environment (IMPROVE) algorithm is also employed to calculate particle extinction coefficient (Chen et al, 2016; Pitchford et al, 2007; Tao et al, 2015). Detailed description of IMPROVE formula is given in supporting information, Text S2.…”

Optical Properties of Aerosols and Chemical Composition Apportionment under Different Pollution Levels in Wuhan during January 2018

“…Mineral aerosol contributed 16% to the PM 2.5 aerosol mass, showing that combustion-related particles rather than wind-blown dust dominated the light extinction budget [19]. The seasonally reconstructed b ext was in the order of autumn (319.4 ± 207.2 Mm -1 ) > winter (269.6 ± 175.5 Mm -1 ) > summer (219.0 ± 129.3 Mm -1 ) > spring (193.3 ± 94.9 Mm -1 ) annually in Guangzhou [20]. RH is an important meteorological factor in the atmosphere and has a notable effect on the formation and optical properties of PM 2.5 .…”

“…In recent years, many studies have been performed to investigate aerosol optical properties in many developed cities in China, such as Nanjing [22,27], Beijing [18,28,29], Guangzhou [20,25], and Chengdu [14,30]. In addition, many studies have been done to determine the relationship between aerosol optical properties and pollution level.…”