Change of air quality and its impact on atmospheric visibility in central-western Pearl River Delta

Abstract

Ambient air quality data, including atmospheric visibility, of Foshan city, a highly polluted city in the Pearl River Delta (PRD), and data obtained by the On-line Air Pollutant Exhaust Monitoring Network (OAPEMN), recently established by the National Emission Monitoring and Control Network for major industrial enterprises, were analyzed and are reported here for the first time, revealing the change in air pollution patterns and its impact on visibility degradation in the last decade. Reduced visibility of less than 8 km (after elimination of rainy and foggy periods) was found 22% of the time from 1998 to 2008, accompanied by elevated levels of pollutants, especially SO₂ and PM₁₀, in comparison with that of other developed cities. However, PM₁₀ showed a steady decreasing trend (0.004 mg m⁻³) year⁻¹) during 2001-2008, in contrast to the noticeable increase in ambient NO₂ concentrations from ~0.020 mg m⁻³ before 2005 to above 0.050 mg m⁻³ afterward. Multiple regression analysis revealed that the percentage of reduced visibility strongly correlated with PM₁₀ concentration, suggesting that visibility degradation was directly proportional to the loading of particles. Moreover, the fairly significant correlation between reduced visibility and NO₂ concentration also implied that the impact of primary emissions of NO₂ and enhanced secondary pollutants, formed via photochemical processes in the atmosphere, could not be ignored. The decreased PM₁₀levels were obviously the predominant factor for the improvement in visibility (5.0% per 0.01 mg m⁻³) and were likely due to the implementation of stricter air pollution control measures for industrial exhaust, which also resulted in reduced SO₂ pollution levels in the recent 2 years. In particular, the OAPEMN records showed an overall enhanced SO₂ removal by 64% in major industrial sectors. The continuous increase in road traffic and lack of efficient NO(x) control strategies in the PRD region, however, caused an increase in ambient NO₂ concentrations.

Carbonaceous and Secondary Inorganic Aerosols during Wintertime Fog and Haze over Urban Sites in the Indo-Gangetic Plain

“…The enhanced levels of pollutants lead to poor air-quality and several environmental, health and socio-economical issues in Asia (Hameed et al, 2002;Lee and Sequeira, 2002;Husain et al, 2007;Bari et al, 2010;Wan et al, 2010;Ziao et al, 2010). Among these, fog-haze formation and reduction in visibility is of major concern (Watson, 2002;.…”

Emerging Air Pollution Issues in Changing Pearl River Delta of South China

“…On the contrary, PM 10 concentrations in Foshan displayed a steady decreasing trend with an overall rate of 3.47 μg m -3 per year in 2001-2008, which was believed to be due to continuous implementation of stricter emission control measures on various industrial sources. For instance, many high emitting factories including cement plants and small-scale ceramic plants were forced to close down by the city government in the past decades (Wan et al, 2011). The SO 2 concentrations in Hong Kong showed a growth rate of 0.28 μg m -3 per year in the period of 1984-2008 (Fig.…”

“…Note that the average SO 2 concentration (60 μg m -3 ) reached the National Ambient Air Quality Standard (Level II) (GB3095-1996) (NAAQS II) of 60 μg m -3 (monthly mean). In fact, more than 50% of the days during the period 2001-2007 in Foshan had daily SO 2 concentrations exceeding the NAAQS I of 50 μg m -3 ( (Wan et al, 2011). Moreover, although the number of episode day with daily NO 2 concentration larger than 80 μg m -3 (NAAQS I & II) in Foshan was close to that in Macao (~7.3%), the frequency of daily NO 2 concentration exceeding 120 μg m -3 (NAAQS III) in Foshan was significantly higher than that in Macao (Fig.…”

“…7). However, the continuous growth in coal consumption triggered the substantial increases in 2006 (Wan et al, 2011).…”

High-resolution sampling and analysis of ambient particulate matter in the Pearl River Delta region of Southern China: source apportionment and health risk implications

“…As stated in section 3.2, there are a large number of industrial activities in the north and northwest directions including ceramic industry and coal combustion. Foshan is an industrial city famous in ceramic industry and manufacturing industry (Wan et al, 2011;Tan et al, 2014). The emissions of large quantities of air pollutants from the above-mentioned industries resulted in deteriorating air quality in Foshan, a city which always ranked among cities with the heaviest air 20 pollution in the PRD region.…”