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Ambient air quality standards are the core strategic goal of ambient air quality management. Countries worldwide have given importance to research on the development of ambient air quality standards. To understand the history of the development of China's ambient air quality standards, this study analyzed the background associated with all previous formulations and revisions of the standards, classification of functional areas, standard grading, pollutants, and evolution of the standard limits over the past 40 years. The results show that since the initial release of the "Ambient Air Quality Standard" by China in 1982, it has been supplemented once, revised twice, and modified twice. The first ambient air quality standard specified the standard limits of six pollutants commonly found in ambient air. With the development of ambient air quality management, the number of pollutants has increased to ten. Since the release of the "Ambient Air Quality Standards" in 2012, the ambient air quality in China has significantly improved. However, the proportion of cities meeting these standards is still low. At present, China is suitably positioned to make the standards associated with 24 hr SO

To compare the inorganic chemical compositions of TSP (total suspended particulate), PM

Concentrations of atmospheric PM10 and chemical components (including twenty-one elements, nine ions, organic carbon (OC) and elemental carbon (EC)) were measured at five sites in a heavily industrial region of Shenzhen, China in 2005. Results showed that PM10 concentrations exhibited the highest values at 264 microg/m3 at the site near a harbor with the influence of harbor activities. Sulfur exhibited the highest concentrations (from 2419 to 3995 ng/m3) of all the studied elements, which may be related to the influence of coal used as fuel in this area for industrial plants. This was verified by the high mass percentages of SO4(2-), which accounted for 34.3%-39.7% of the total ions. NO3-/SO4(2-) ratios varied from 0.64-0.71, which implies coal combustion was predominant compared with vehicle emission. The anion/cation ratios range was close to 0.95, indicating anion deficiency in this region. The harbor site showed the highest OC and EC concentrations, with the influence of emission from vessels. Secondary organic carbon accounted for about 22.6%-38.7% of OC, with the highest percentage occurring at the site adjacent to a coal-fired power plant and wood plant. The mass closure model performed well in this heavily industrial region, with significant correlation obtained between chemically determined and gravimetrically measured PM10 mass. The main constituents of PM10 were found to be organic materials (30.9%-69.5%), followed by secondary inorganic aerosol (7.9%-25.0%), crustal materials (6.7%-13.8%), elemental carbon (3.5%-10.8%), sea salt (2.4%-6.2%) and trace elements (2.0%-4.9%) in this heavily industrialized region. Principal component analysis indicated that the main sources for particulate matter in this industrial region were crustal materials and coal/wood combustion, oil combustion, secondary aerosols, industrial processes and vehicle emission.