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In order to study the characteristics of atmospheric extinction coefficient in Beijing, systematic measurements had been carried out for atmospheric visibility, PM2.5 concentration, scattering coefficient, black carbon, reactive gases, and meteorological parameters from 2013 to 2014. Based on these data, we compared some published fitting schemes of aerosol light scattering enhancement factor [ f(RH)], and discussed the characteristics and the key influence factors for atmospheric extinction coefficient. Then a set of parameterization models of atmospheric extinction coefficient for different seasons and different polluted levels had been established. The results showed that aerosol scattering accounted for more than 94% of total light extinction. In the summer and autumn, the aerosol hygroscopic growth caused by high relative humidity had increased the aerosol scattering coefficient by 70 to 80 percent. The parameterization models could reflect the influencing mechanism of aerosol and relative humidity upon ambient light extinction, and describe the seasonal variations of aerosol light extinction ability.

The impact of transport pathways on aerosol properties at Shangdianzi (SDZ) background station was analyzed using the back trajectory analysis method with the observation of PM2.5 concentration and aerosol scattering coefficients ( σ(sp)) during 2005-2010. The results showed that the pollutant level at SDZ was influenced by both the direction and motion state of air masses. The southerly transport pathways of air masses had higher PM2.5 concentration and σ(sp) than those of northerly pathways. The air masses with lower moving speed and altitude generally corresponded to higher PM2.5 concentration and σ(sp). Air masses originated from the North China Plain in spring, summer and autumn, and air masses from the north of North China region in winter had a significant contribution to PM2.5 concentration and σ (sp) at SDZ. Dust aerosol appeared frequently in spring, and the mean scattering efficiency (α(sp)) was 0.78 m2 x g(-1). The mean α(sp) of anthropogenic aerosol of four seasons was 4.00 m2 x g(-1) with the highest value in winter and the lowest in spring. The west-northwest, southerly pathways, and the northerly pathways with low moving speed in spring, summer and autumn correspond to higher α(sp) ( > 4.0 m2 x g(-1)). This indicated that these pathways were affected by the emissions form human activities. However, the α(sp) in winter kept at a high level among all pathways, which suggested that the emission effect was relatively uniform in surrounding regions in winter. The other northerly pathways in spring, summer and autumn were affected by anthropogenic pollutants mixed with dust.

The significant effect of anthropogenic pollutants transportation on the physical and optical properties of regional background atmospheric aerosol was studied by using ground-based and satellite remote sensing data obtained at the atmospheric background station (Shangdianzi, Beijing) of North China during October 1 to 15 in 2011. The aerosol mass concentration and reactive gases concentration increased obviously during periods of October 4-5, October 7-9, and October 11-12. Comparing with the background period of October 1-3, volume concentration increased by a factor of 3-6 for reactive gases such as NO(x), and CO, and a factor of 10-20 for SO2. Mass concentration of PM2.5 was about 200 microg x m(-3) on October 9. During haze period, the AOD at 500 nm varied between 0.60 to 1.00. The single scattering albedo (SSA) was lower than 0.88. And the black carbon concentration increased 4-8 times, which suggested the aerosol absorption was very strong during this pollution episode. The absorption of aerosol particles could cause 100-400 W x m(-2) increase of atmospheric radiation. The surface radiation decreased by about 100-300 W x m(-2) due to the aerosol scattering and absorption. This could cause higher stability of atmosphere, which will significantly affect the cloud and precipitation, and thus the regional weather and climate.

By means of field sampling and laboratory analysis, the content distribution characteristics of Cd, Cr, Cu, Ni, Pb and Zn in agricultural region soils of Huaihe basin in Anhui province were analyzed. Assessment of heavy metal pollutions was conducted using enrichment factor, geoaccumulation index and potential ecological risk index. The results showed that the average mass fraction of Cd and Cu was 0.113 5 and 22.09 mg x kg(-1) respectively in the study area soil, which were above the background values 0.097 and 20.4 mg x kg(-1) in Anhui Province. The average mass fraction of other four heavy metals did not exceed the average values of Anhui Province. The results of the evaluations from geoaccumulation index and ecological risk assessment discovered that Cd is the strongest pollution metal among six heavy metals in the study area soil. For some samples of the study soil, Cd was slight risk for the ecosystem. The ecosystem risks caused by the other five heavy metals were not obviously for the sampling points. The entire study area soils were mid integrated potential ecological risk.

Summer is another peak season for haze besides winter in Beijing area, which is different from that in South China. The data of microwave radiometer, profiler, sounding, AWS, NCEP (NCAR) and air pollution monitors were used in the analysis of two haze cases which occurred in winter and summer, respectively. Both cases lasted for 6 days. This research focused on the difference in the mechanism of the formation and persistence of haze cases in various seasons. In winter, north-westerly flow dominated Beijing at upper-levels and a few of shallow troughs passed by during persistent haze development. The main meteorological reasons for lower visibility in 6 days were: there was an inversion in the boundary layer all the time; wind was weak at surface and moisture went up gradually. The change of inversion height and humidity day and night led to the diurnal variation of PM2.5 concentration and visibility. The surface wind speed kept lower because the weak cold air could not often hit the surface during the haze case. In addition, three factors played key roles in the inversion formation in boundary layer. One was that the rapid decrease in the surface temperature after sunset due to the radiation. At the same time, there was some warm advection at upper boundary layer. The third one attributed to the temperature increase after the air flowing over the mountains and down. However, in summer, regional transportation of aerosol, sustained convective stability and high air saturation were very important factors for the haze formation. Under the sub-tropic high control, the wind direction at lower troposphere was south. The PM2.5 concentration went up when the speed of south wind increased. The south flow caused by both synoptic scale systems and mountain-valley breeze near Beijing transported the aerosol northward from higher polluted area. There was no inversion in the summer haze case. But, the convective inhibition was kept over 200 J x kG(-1). As the result, it was not favorable for the pollutant diffusion upward. Furthermore, the level of free convection also changed during the day and at the night, which had similar effect on the PM2.5 concentration and visibility as the daily variation of inversion. In conclusion, these cases in winter and summer were categorized into two different kinds of persistent haze. The main reason leading to the difference was the synoptic pattern.

Five secondary aluminum metallurgy enterprises in the southwest area of China were measured for emissions of PCDD/Fs. The results indicated that the emission levels of PCDD/Fs (as TEQ) were 0.015-0.16 ng x m(-3), and the average was 0.093 ng x m(-3) from secondary aluminum metallurgy enterprises. Emission factors of PCDD/Fs (as TEQ) from the five secondary aluminum metallurgy enterprises varied between 0.041 and 4.68 microg x t(-1) aluminum, and the average was 2.01 microg x t(-1) aluminum; among them, PCDD/Fs emission factors from the crucible smelting furnace was the highest. Congener distribution of PCDD/F in stack gas from the five secondary aluminum metallurgies was very different from each other. Moreover, the R(PCDF/PCDD) was the lowest in the enterprise which was installed only with bag filters; the R(PCDF/PCDD) were 3.8-12.6 (the average, 7.7) in the others which were installed with water scrubbers. The results above indicated that the mechanism of PCDD/Fs formation was related to the types of exhaust gas treatment device. The results of this study can provide technical support for the formulation of PCDD/Fs emission standards and the best available techniques in the secondary aluminum metallurgy industry.

Six cement kilns were measured for emissions of PCDD/Fs in the Southwest Area, China. The results indicated that the emission levels of PCDD/Fs were 0.0029-0.0062 ng-m(-3) (Average, 0.0043 ng X m(-3)) from cement kilns which did not burn solid waste, and 0.028 ng X m(-3) from co-processing sewage sludge in cement kiln. The levels of PCDD/Fs emissions from cement manufacturing in the Southwest Area were significantly below the national emissions standard (0.1 ng x m(-3)). Emission factors of PCDD/Fs from the six cement kilns varied between 0.0089 and 0.084 microg x t(-1) cement, which were near or below the lowest emission factor reported by UNEP in 2005. Moreover, the emission factor of PCDD/Fs from co-processing sewage sludge in cement kiln was 7.6 times of the average factors from the other five cement kilns. Moreover,congener distribution of PCDD/F in stack gas from the two types of cement kilns was very different. The results showed that modern dry process cement kilns with preheating have lower emissions of PCDD/Fs. This suggested that the product of co-processing solid waste in cement kilns should be largely enhanced in China in future.

As a comprehensive monitoring survey on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in Chongqing, 20 ambient air samples taken from 5 locations in four seasons were studied. The PCDD/F TEQ concentrations varied from 0.017 pg x m(-3) to 0.21 pg x m(-3). The average value was (0.094 +/- 0.054) pg x m(-3). The PCDD/F concentrations varied by locations and seasons, and the orders were: urban area > suburban area > background area, and Winter > Spring > Autumn > Summer. The concentrations of PCDD/Fs were 2.2-4.6 times higher in the winter than during the summer. The PCA results indicated that PCDD/F homologue pattern varied by seasons. The PCDD/F homologue pattern in particle dominated in winter and spring, and the pattern in gas dominated in summer and autumn. The mass concentration of PCDD/F congener was significantly positively correlated with that of SO2, NO2, PM10 and TSP, and insignificantly negatively correlated with that of O3, respectively. The results showed that spatial distribution and seasonal variation of atmospheric PCDD/Fs in Chongqing was consistent with that of these conventional indicators, and the PCDD/Fs pollution was closely related with the emission sources of SO2, NO2, PM10 and TSP.

A study on the effect of weather condition on the aerosol scattering property has been carried out using one year measurement data sets of aerosol scattering coefficient (ASC) and meteorological parameters at Shangdianzi (SDZ). The results showed that the ASC was highest in haze-fog day with 608.4 Mm(-1) and higher in fog day with 500.6 Mm(-1) and haze day with 423.7 Mm (-1) those were 6.4-9.2 times higher than the ASC in normal day. The ASC was highest in summer in all kinds of weather conditions. The lower ASC in fog day and haze-fog day was observed in autumn and winter, respectively. There was no evident difference of the ASC between other three seasons in haze day and normal day. Pronounced seasonal variation of the mass scattering efficiency (MSE) of PM2.5 was observed in fog day with the highest value in summer. Significant diurnal variations in ASC were observed in haze-fog day and normal day with a unimodal pattern and a bimodal pattern, respectively. The wind was the most important factor for the ASC at SDZ. The transport of aerosol particles by the strong southwest wind should be responsible for the higher level of ASC in SDZ area and regional scale in low visibility weather conditions. The northeast wind was favourable to the reduction of ASC, especially in normal day.

In this study ozone and meteorological factors were measured at an urban station and a downwind rural station around Beijing from June 2005 to September 2006. The ozone at urban station exhibited stronger diurnal and seasonal variations than that at the rural station. The maximum concentrations of ozone were 198.9 x 10(-9) and 151.2 x 10(-9) at Beijing and Xinglong, while there were 171 hours and 255 hours in which ozone exceeded the China's norm, respectively. 90% of the exceeding occurrences happened before 16:00 in Beijing, while more than 82% happened at night in Xinglong. The peak concentration of ozone at Xinglong in the diurnal cycle was 3-4 hours lag of that at Beijing because of the influence of air mass from Beijing. Double ozone peaks phenomena can be found at Xinglong due to the mountain-valley breezes especially in the summertime. Stagnant meteorological conditions and mountain-valley breezes can cause ozone accumulation at downwind areas. The AOT40 values were 23.1 x 10(-6) x h, 26.5 x 10(-6) x h, and 14.1 x 10(-6) x h in spring, summer and autumn respectively at Xinglong, which could cause more than 30% lose in wheat yields.

An in situ GC-ECD monitoring system was established at the Shangdianzi GAW Regional station from April 2007 to March 2008, and the mixing ratio of atmospheric HCFC-22 was (278.1 +/- 113.6) x 10(-12) (mol/mol). A "R" statistical software was applied to the HCFC-22 time series to separate background and pollution data. The background HCFC-22 mixing ratio was (199.5 +/- 5.1) x 10(-12), close to northern hemisphere background level observed at Mace Head and Trinidad Head stations. The pollution HCFC-22 mixing ratio was (312.1 +/- 121.0) x 10(-12) due to anthropogenic emission from various regions and air mass transport. There was no significant seasonal variability of background data. However, pollution data was much higher in summer than that in winter, and elevated up to 100.9 x 10(-12) in July than in January attribute to seasonal emission characteristics. The mean HCFC-22 mixing ratio from southwest wind sector (327.3 x 10(-12)) was much higher than that of northeast sector (236.2 x 10(-12)). The W-WSW-SW wind sector has a positive contribution to the HCFC-22 level, while NNE-N-NE has a large negative contribution.