Models-3/CMAQ and Brute Force method were applied to simulate the ozone pollution and to analyze how meteorological condition influenced the pollution characteristic and the source apportionment of ozone during July 2014 in Baoding. The distribution of ozone concentration in Baoding gradually increased from west to east. In July, the high ozone episode mainly occurred when southern air mass, southeastern air mass and eastern air mass arrived, and the percentages of polluted days were about 28%, 39% and 17%, respectively. During the maximum eight hours of ozone, background and cross regional transmission contributed about half of concentration of surface ozone. As for the regional contribution, Hebei contributed about 2/5 of the surface ozone. Henan contributed about 1/10 as well as Shandong and Jiangsu. The rapid increasing contribution from central Hebei and influences of vertical transportation from Henan and Shandong province leaded to rapid increasing of surface ozone concentration during the daytime in Baoding; most regional contribution changed gently except for central Hebei area, which resulted in high ozone concentration and long duration in the afternoon as well as the single peak diurnal variation.

The authors conducted on-line measurements of water soluble inorganic ions and their gas phase precursors for more than 30 days at Wangdu, Baoding City in summer in 2014 with a Gas and Aerosol Collector (GAC). It was found that, the observation site was always subjected with an ammonia rich conditions; the averaged PM_2.5 concentration was 68.2 μg/m3, of which the detected SO₄^2-, NO₃^-, Cl^-, NH₄⁺ and K⁺ by GAC was 12.6, 8.5, 1.4, 11.7 and 0.7 μg/m³, respectively, consisted 51% of the total mass of PM_2.5. All these observed pollutants showed distinct diurnal variations: SO₂, SO₄^2-, NO₃^-, NH₄⁺ and Cl^- showed a morning maximum, HCl and HNO₃ presented an afternoon peak, and NH₃ possessed a day-night variations. As depicted by the analysis of Sulfur and Nitrogen Oxidation Rates (SOR, NOR), fast transformations of trace gases into secondary inorganic aerosols were indicated. The averaged value of SOR and NOR are 0.43 and 0.22, respectively. The variation of SOR and NOR inferred that both gas phase and aqueous oxidations contributed to the fast transformation that formed water soluble inorganic salts.

The Comprehensive Air Quality Model with extensions (CAMx), a 3-D regional chemical transport model, was used to simulate ozone concentrations in the Pearl River Delta (PRD) in November, 2009. Ozone Source Apportionment Technology (OSAT) was applied to investigate sources of two typical ozone episodes and a clean day as comparison. The results showed that emissions from urban Guangzhou and Dongguan mainly contributed to local areas and the southwestern part of PRD (15–30 μL/m3), while emissions from Shenzhen Baoan district (15–25 μL/m3) mainly affected the Pearl River Estuary. Mobile sources and solvent usage sources were two major contributors to ozone formation and had an influence in most areas of the central and western PRD. Mobile sources could contribute as much as 50 μL/m3 hourly ozone concentration to the boarding area of Foshan and Guangzhou. Trans-boundary import of ozone made episodes more likely to occur in PRD under unfavorable weather conditions, however, the ozone precursors emitted within the PRD region were the main cause of high ozone concentrations during ozone episodes. As a result, the strategies on controlling emissions within the PRD region are the key to the reduction of ozone pollutions in PRD.

For the first time, PM2.5 source apportionment methods and techniques previously and currently applied in China are summarized, including sampling preparation, sampler selection, chemical speciation analysis, and source apportionment tools. The research direction for PM2.5 source apportionment work in China is also suggested. This review is expected to provide a fundamental understanding of PM2.5 source apportionment methods and to serve as an important reference for future source apportionment studies to be widely conducted in China and regulations or law for PM2.5 abatement in China.

The Community Multi-Scale Air Quality (CMAQ) modeling system was applied to simulate the meteorology field, O₃ and PM10 in the Pearl River Delta (PRD) region in the autumn of 2008, in order to elucidate the impact of the typical meteorological conditions on the O₃ and PM10 pollution episodes. It was found that PRD pollution characteristics presents periodic variation affected by cold air processes in the autumn of 2008. In general, good air quality was presented when cold air passing through while serious pollution was took place before and after the cold air invasion. 1) Before the cold air invasion, when the weather system “cold front front part” was presented, the height of the mixing layer was often low due to a presence of temperature inversion. Therefore, the PM10 emitted or formed at night was continuously accumulated in the morning hours causing the air pollution in northern and central PRD; the afterwards transport of the O₃ during daytime and PM10 during nighttime with northern wind would cause the air pollution in southern PRD. 2) Before the cold air invasion, when the weather system “high-pressured base” was presented, an inversion layer was built up to prevent vertical mixing; both O₃ and PM10 was then mainly horizontally transported with northeasterly wind; consequently forming air pollution in southwestern PRD. 3) After the cold air invasion, under the control of a ridge high pressure type of weather condition, temperature inversion was built up near the surface and a stagnant condition was presented; thus, O₃ and PM10 was trapped in the source regions such as western, northwestern and central PRD, resulted in serious local pollutions.

Models-3/CMAQ was applied to simulate the ozone-precursor sensitivity during June, July, and August, 2010 in Beijing. Frequencies of ozone-precursor sensitivity regimes were used to represent the characteristics of the spatial distributions of the regimes. Results showed that ozone formation was VOCs-sensitive in urban Beijing, and turned to be mixed sensitive and NO_x-sensitive in suburban areas and more remote areas of Beijing. In urban Beijing, the number of days that a reduction of anthropogenic VOCs could reduce ozone efficiently accounted for about 50% of the whole summer; while in Changping, Yanqing and Huairou, the number of days that a reduction of anthropogenic NO_x could reduce ozone efficiently accounted for 40%~50%. The situation that ozone gave little response to the reduction of both two precursors occurred in every district/county. The number of days in this situation accounted for more than 70% in eastern and southern districts/counties. The distributions of the sensitivity regimes of maximum 8-hour ozone concentration were similar to that of 1-hour ozone concentration.

The Models-3/CMAQ modeling system was applied to investigate PM₁₀ pollution over the Pearl River Delta (PRD) region during October 2006. Sensitivity analysis was conducted to examine the relationship between the reduction of different source emissions and the consequent change of PM₁₀ concentrations, and to quantify the interaction of air pollution among adjacent cities. The results show that PM₁₀ pollution is a regional-scale issue in PRD. Guangzhou, Foshan, Jiangmen, and Dongguan contribute to the PM₁₀ in PRD remarkably. The relative sensitivity coefficient was proposed to determine the impact of regional pollution sources. The PM₁₀ concentrations in Zhuhai, Jiangmen, Zhongshan, and Foshan cities are significantly influenced by regional source emissions. The intercity transport has been the important factor of PM₁₀ pollution in PRD. To improve the air quality in PRD area, effective control of emission sources should be highly reinforced, together with consentaneous programming, intensive collaboration, joint prevention and control.

A couple of carbonaceous aerosol online monitoring instruments, which are popularly used in the world, were compared by real atmospheric measurement, in order to provide some useful information on their characteristics to scientists in the field. Elemental carbon (EC) and organic matter (OM) in atmospheric fine particles in Shenzhen were monitored simultaneously by 4 different online instruments from October 31 to November 8, 2009, and the comparison among the results indicated that the EC concentrations measured using an aethalometer and an single particle soot photometer (SP2) agreed with each other quite well, with R² = 0. 97 and slope = 1. 00; the EC concentrations measured using an online EC/OC analyzer also correlated well ( R²> 0. 95) with those by the aethalometer and SP2, but presented 30% - 40% lower concentration levels; the organic carbon (OC) concentrations measured using the online EC/ OC analyzer correlated well (R²= 0. 83) with the OM concentrations measured using an Aerosol Mass Spectrometer (AMS), but deviated from the OM time-series trends relatively more when the OM were at high concentration levels. Possible reasons for the differences among the measurement results are discussed.

PM₁₀ samples were collected from seven sites in Gua ngzhou area and associated chemical species including seventeen elements(Na, Mg,Al, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, As, Se, Cd, Ba, and Pb), five water solub le ions(SO_４^2-, NO_３^-, F^-，Cl^- and NH₄⁺) ,and organic an d elemental carbons were a nalyzed. This paper discusses chemical characters, the changes of PM₁₀ and maincomponents under different meteorological conditions, and also sources identification of PM₁₀ by principal factor analysis. The results indicated that the averagePM₁₀ concentration was 125.8μg/m³ and organic matter, sulfate and crustal dustwere maj or components with proportions of 24%-32% ,17%-21% and 10%-12%, respective ly in the seven sites. Principal factor analysis indicated that soil dust, oil burning, industry source(including metallurgy, chemistry and electric industry), coalburning, secondary source (by photochemical reaction) and biomass burning were t he main sources of PM₁₀, accounting for 20.7%, 17.8%, 16.3%, 14.3%, 10.4%, and 6.3%, respectively of the total variance in the data set.

Current status of nitrogen oxides-related pollution in China was analyzed, including NO_x pollution and the related pollution of ozone, acid rain，particulate matter. Then the NO_x and related air quality standards were reviewed. Finally, strategy for integrated and multi-target control of NO_x pollution were put forward: executing ozone air quality standard, establishing the regional photochemical smog monitoring network; pursuing air quality modeling and control for Beijing, Pearl River Delta etc megacities; strengthening the control of NO_x emission from power station and vehicles and setting NO_x-related scientific research program.

Based on the atmospheric chemistry transport model CAMx, its adjoint model is constructed. The adjoint model code is hand-generated and numerical experiments are designed to test and validate the code. CAMx and its adjoint model are applied for simulation and sensitivity analysis of air pollution in the Pearl River Delta. The sensitivities of high ground level sulfur dioxide and ozone respect to pollutant sources are calculated, and the applicability of linear sensitivity coefficients is discussed through numerical experiments, which provide important information for extensive analysis of pollution mechanisms and control strategies. Using the adjoint model, the sensitivities of an object function respect to thousands of input variables can be calculated efficiently. With the introduction of the adjoint method, the function of CAMx is considerably extended, and provides a powerful tool for inverse problems on emission parameters as well as for management of atmospheric environment.

Based on the method of gold amalgamation and CVAFS, the authors designed an instrument for continuously measuring total gaseous mercury in ambient air. The instrument operates with purified ambient air as carrier gas and does not require Argon or Nitrogen for detection. The sampling is run at about 1L/min, with sampling times of 10 min. Under these conditions, a detection limit of about 0.2ng/m³ is achieved. It has been showed that the relative standard deviations for 0.1 ng mercury vapor samples is less than 1.4%, and the linearity of calibration curve is quite well with the correlation coefficient of 0.9995. The instrument was used to continuously measure total gaseous mercury in the atmosphere at Peking University for about three weeks, observing an average concentration of TGM about 7.8ng/m³.

The concentration of peroxides in atmosphere in Beijing and Guangzhou was measured by using the HPLC post-column derivatization system. The H₂O₂average concentration was 2.33×10^-9, 0.338×10^-9 and 0.148×10^-9(V_H2O2V_air) respectively in May, June and September, 2000 in Beijing. The H₂O₂ average concentration was 0.168×10^-9V_H2O2/V_air) in November, 2000, in Guangzhou. The factors that affected peroxides were discussed. The results showed that peroxide concentration was high in daytime and low at night in both sites. Variation of concentration of organic peroxide is similar to that of hydrogen peroxide. The concentration of peroxides has positive correlation with that of O₃ and HCHO.

Based on the studies on photochemical smog in Xigu and Yanshan petroleum industrial areas, Beijing city and Guangzhou City, the current pollution level of photochemical smog and its characteristics in China are discussed, its formation mechanism is explored, and its changing tendency in near future is predicted. The results show that photochemical smog pollution is serious in above areas and the effective way to control the photochemical smog in China is to decrease NO_x emission. The ozone peak appears not only earlier, but also is higher year by year at Zhongguancun, Beijing, which phenomenon indicates that the atmospheric photochemical activity is enhanced. As the fast increasing of the vehicle population, the air pollution in some big cities is in a transition from coal burning caused problem to automobile exhaust related pollution or the pollution combined them.