Remote sensing the surface air quality from space is a new technology following the development of the space-based observations. How to use the column atmospheric aerosol optical depth ([EQUATION]) products to quantitatively estimate surface air quality is a difficult question. The surface extinction coefficients ([EQUATION]) and the dry aerosol extinction coefficients ([EQUATION]) are derived from high spatial resolution aerosol optical depth products with a vertical distribution correction and a moisture effect correction. It is found that the [EQUATION] has a higher correlation with surface PM[EQUATION] mass concentration than the [EQUATION], and the [EQUATION] has the highest correlation among the three variables with PM[EQUATION] measurements. The products of [EQUATION] are used to estimate the air quality change in summer of 2008 in Beijing. Comparing with the seasonal averaged data in 2005[EQUATION]2007, the surface aerosol extinction in summer of 2008 decreased by 17[EQUATION]20%. In the other cities and regions of the North China Plain, there is no significant change on the surface aerosol distributions. It is concluded that the decrease of aerosol loading in Beijing is related to the local emission reduction directly.

With the rapid economic growth of China, environmental pollution has become one of the most widely concerned issues. The air pollution in economy fast developing area has appeared regional and complex behavior by the accumulation and coupling of multi pollutants from various sources. Although many ambient air quality monitoring stations are established in urban area, the ground surface pollutant levels are limited to give the whole picture of the air pollution and reveal its real evolution process, chemical reaction scheme and regional transportation. It brings some confusion to the public by the mismatch of air quality index with the sense of atmospheric visibility. Several advanced optical and spectroscopic techniques and an integrated spatio-temporal air quality monitoring system based on these techniques are introduced, which are applied to monitor the particulate matter regional transport flux, gaseous pollutant emission flux from area sources and distribution of vertical columns of trace gases in a large area. The partly measurement results obtained during the 2008 Beijing Olympic Games are presented. The monitoring method and techniques applied for the regional and complex air pollution study are also discussed.

A world-wide attention has been paid to the air quality during the Beijing Olympic Games, especially the air pollution during the haze days. In order to monitor the air quality during Olympic Games, a project of Knowledge Innovation Program of Chinese Academy of Sciences, named as ‘Union Action Plan for Air Quality Monitoring and Forecasting During Olympic Game in Beijing and its Surround Area’, was carried out in Beijing in 2008. Different techniques have been used, including the ground-based [EQUATION]-[EQUATION] measurements, ground-based remote sensing and satellite measurements. The results demonstrated that the haze distribution on a regional scale can be derived from satellite measurements, and the relative humidity of 68.84% during the haze days in Beijing is only 4.23% larger than that during the non-haze days. Measurements from the Super Station at the Institute of Remote Sensing Applications (IRSA) revealed that the visibilities were about 5 km during the haze days, and the haze aerosol optical depths were mostly more than 1.0 during last August. The ground-based measurements from Beijing and its surrounding stations show that the averaged PM[EQUATION] and PM[EQUATION] mass densities were 68.08 [EQUATION]g/m[EQUATION] and 178.81 [EQUATION]g/m[EQUATION] during the haze days respectively, while the corresponding values are 29.58 [EQUATION]g/m[EQUATION] and 76.05 [EQUATION]g/m[EQUATION] during the non-haze days. The measured total column densities of NO[EQUATION] are far below the national standard, however, the space-borne observation by OMI/Aura showed high values in several areas in North China, including Beijing, Tianjin, Tangshan and some regions located in Shandong, Hebei, Shanxi and Henan provinces. Further analysis to the monitoring data and the backward track trajectory of wind profile indicated that the formation of haze in Beijing is mostly resulted from the wet growth of fine solution particulates under the stable atmospheric conditions with a plenty of water vapor, consequently leading to the rapid decrease of the visibility. As an evidence, a rapid increase of the PM[EQUATION] mass extinction across section was noticed that when the relative humidity is up to 95% from the measurements at the Super Station.

The concentration distribution of CO in Beijing based on MOPITT data and instrumental dataset was analyzed. The results showed that CO column concentration reflected the contamination level of the territorial air pollution, and near-ground CO mass concentration was mainly due to local air pollution emission. As for the continental background CO column concentration of Waliguan was similar to seasonal variations of near-ground mass concentration. CO column concentration reached its peak in spring, but mass concentration near the ground surface was higher during heating period when compared to no-heating period in Beijing. CO column concentration during August of 2000[EQUATION]2007 increased slowly but mass concentration near the ground surface decreased significantly in Beijing. Air cleaning measures taken during 2008 Beijing Olympic Games considerably reduced about 19.3% column concentration and 46.7% mass concentration of CO due to decreased emission of air pollutants from Beijing and its circumjacent regions. It can be concluded that the air cleaning measures greatly improved air quality, but the distribution of air pollution is still kept as it is.

Experiments for estimation of SO emissions from one point-source and one area-source in Shijingshan District, Beijing were introduced, in which a mobile mini-DOAS system was employed to study the environmental prerequisites for its application. A comparison among meteorological conditions for each experiment indicates that, (1) a mid-scale weather system was necessary for measurement so as to avoid local mountain-valley winds; (2) when mixing height and wind velocity were low, more accurate measurements can be obtained and are closer to statistical values from the local authority; (3) using wind direction and velocity at emission height yielded a better estimation of pollutant emission of the point source.

Particulate matter has become the most important pollutant source with the rapid development of industrial economy. The aerosol particle number size distribution may be more important than the mass density in the view of its harm to human health. So the research on the aerosol particle number size distribution appears to be more and more important today. By using the fine particle meter developed by Anhui Institute of Optics and Fine Mechanics, an online, wide-range and quickly measurement of aerosol particle number size distribution in Beijing city during the Olympic Games was performed without making any changes to the samples. The variation trend of daily average and real time of particle matter number concentration, the particle number size distribution during the Olympic Games were analyzed. The results show that the particle number concentration of nucleation mode (5[EQUATION]20 nm) has close relationship with the nucleation process, and the concentration curve is unimodal. Particle number concentration of atiken mode (20[EQUATION]100 nm), with curve of three peak values, is strongly influenced by human activities and growing process of nucleation mode. Accumulation mode, with a tiny trend for its day average particle number concentration, is strongly affected by the weather conditions, especially in strong wind and heavy rain. The concentration of accumulation mode can directly influence the atmospheric visibility.

Black carbon aerosol (BC) has been measured at IRSA site in Beijing during July and August, 2008. By analyzing these real-time BC data, the concentration distributions and the sources of BC are concluded. The average concentrations of BC in July and Beijing Olympic Games are 4.58 [EQUATION]g/m[EQUATION] and 3.07 [EQUATION]g/m[EQUATION] respectively, that the declining ratio is about 33.0%. It shows that a series of regulations successfully decreased the concentration of BC. The correlation coefficient between daily average concentration of BC and inhalable particles(PM[EQUATION]) is 0.86, while the value of BC/PM[EQUATION] is 1.9%. Through comparing with the BC concentration of summer in 2007, the results indicated that the concentration of BC has reduced during Beijing Olympic Games.

In order to study the structural feature of the atmosbhere boundary layer (ABL) over downtown of Beijing and the aerosol extinction characteristics in it during the Beijing Olympic Games, ABL over Beijing was observed with a MPL lidar in August, 2008. The vertical distribution of extinction properties and the height of ABL over the observation site were inverted. The observation data was compared with the results of observations in previous years at downtown of Beijing and Lihua Village in souther suburb of Beijing which was viewed as a standard of clean control site. The data indicate that the diurnal variation of ABL over Beijing during the Olympic Games is obvious, which is low in morning and evening, and high at noon time. The ABL height is relatively stable, it is always less than 2.0 km, its average height is 0.79 km. Compared with the data of previous years, the aerosol particle concentration level at downtown of Beijing during the Olympic Games is descended apparently. The aerosol concentration at observation site changes periodically every day.

The theories of operation of aerodynamic particle sizer spectrometer and tapered element oscillating microbalance are different, and the data types of two measurements are also different. Using the aerodynamic particle sizer spectrometer, the data of particle size distributions were measured in three seasons (winter, spring and summer) in Beijing. Using three instruments of model R&P1400a, the data of PM[EQUATION], PM[EQUATION] and PM[EQUATION] were measured. According to the correlation comparison of the data of two analysis methods, the data correlativity of aerodynamic particle sizer spectrometer and tapered element oscillating microbalance was obtained. The regression equation of two measurements was established.