Abstract
ABSTRACTA one-year campaign was conducted to collected PM2.5 samples in the rural area of Guangzhou, the largest megacity in South China, from March 2012 to February 2013. Mass concentration of PM2.5, carbonaceous fractions (i.e., organic carbon (OC) and elemental carbon (EC)) and 6 water-soluble ions were analyzed. Light extinction coefficient (bext) of fine particulate matter was reconstructed using the revised IMPROVE formula at the site. The reconstructed bext was compared with the measured bext converted from visibility. A good correlation was obtained between the two sets of bext with a coefficient of determination (R2) of 0.61 and a slope of 0.99. The average reconstructed bext in the study was 253.7 ± 162.9 Mm–1. The seasonal reconstructed bext 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). (NH4)2SO4 (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 bext and measured bext was investigated under the influence of seasonality, visibility and PM2.5 concentration. We found that bext could be reconstructed using revised IMPROVE formula in high PM2.5 days (threshold value of ~60 µg m–3). On other hand, the performance of formula was unsatisfactory for bext reconstruction of in low PM2.5 days, when meteorological conditions could have significant impact on visibility.
Highlights
Visibility is an indicator of air quality in urban areas in the absence of special weather conditions (Watson, 2002), and its deterioration has become one of the adverse effects of air pollution (Horvath and Noll, 1969)
We present the results of our measurement of PM2.5 and its chemical composition as well as the application of the revised Interagency Monitoring of Protected Visual Environments (IMPROVE) formula at a regional site in the Pearl River Delta (PRD) region in order to: (1) understand the relationship of public available visibility and chemical composition of PM2.5; (2) evaluate the applicability of the revised IMPROVE formula to light extinction estimation; and (3) assess the contributions of individual components of PM2.5 to the total light extinction
The relationship between visibility and revised IMPROVE formula was used to evaluate the contribution of PM2.5 to reduced visibility at a regional site in the PRD region from March 2012 to February 2013
Summary
Visibility is an indicator of air quality in urban areas in the absence of special weather conditions (e.g., fog and rain) (Watson, 2002), and its deterioration has become one of the adverse effects of air pollution (Horvath and Noll, 1969). Visibility impairment is caused by scattering and absorption of light by aerosol particles and gases in the atmosphere (Ouimette and Flagan, 1982). It is a complex process with many factors involved including concentrations, size distributions, and composition of aerosol particles as well as meteorological conditions (Watson, 2002). When particle size distribution and index of refraction are known, bsp can be quite accurately estimated using Mie theory (Pitchford et al, 2007) This method has been used in many intensive short-term studies (Tao et al, 2014b; Gao et al, 2015). The general expression is as follows: bext MEEi fi RH M i (1)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
