Prospect of China's ambient air quality standards

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 SO2concentrations more stringent such that it meets the values defined in the World Health Organization(WHO)interim target-2 and the WHO air quality guideline(AQG).We further suggested that the SO2standard should be revised promptly.Simultaneously,regions with a relatively high proportion of cities meeting the standard are encouraged to introduce more stringent interim target limits in due course to manage the local ambient air quality.

Chemical composition, mass closure and sources of atmospheric PM_(10) from industrial sites in Shenzhen, China

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 μg/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 SO42-, which accounted for 34.3%-39.7% of the total ions. NO3-/SO42- 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.

Comparison of inorganic chemical compositions of atmospheric TSP,PM10 and PM2.5 in northern and southern Chinese coastal cities

To compare the inorganic chemical compositions of TSP（total suspended paniculate）,PM10（particulate matter with an aerodynamic diameter less than 10 μm） and PM2.5（particulate matter with an aerodynamic diameter less than 2.5 μm） in southern and northern cities in China,atmospheric particles were synchronously collected in Dalian（the northern city）and Xiamen（the southern city） in spring and autumn of 2004.The mass concentrations,twenty-three elements and nine soluble ions were assessed.The results show that in Dalian,the mass concentrations of Mg,Al,Ca,Mn and Fe in spring were 4.0-10.1,2.6-8.0,4.1-12,1.2-3.6 and 2.9-7.9 times higher,respectively,than those in Xiamen.The dust storm influence is more obvious in Dalian in spring.However,in Xiamen,heavy metals accounted for 13.9%-17.9%of TSP,while heavy metals contributed to 5.5%-9.3%of TSP in Dalian.These concentrations suggest that heavy metal pollution in Xiamen was more serious.In addition,the concentrations of Na＋,Cl-,Ca2＋ and Mg2＋ were higher in Dalian due to the influence of marine aerosol,construction activities and soil dust.The NO3-/SO42- ratios in Dalian（0.25-0.49） were lower than those in Xiamen（0.51-0.62）,indicating that the contributions of vehicle emission to particles in Xiamen were higher.Coefficient of divergence values was higher than 0.40,implying that the inorganic chemical composition profiles for the particles of Dalian and Xiamen were quite different from each other.