The polyaniline/vapor grown carbon fiber (PANI/VGCF) was synthesized by in-situ polymerization, and SEM, FTIR, and TGA were used to investigate the microstructure, polymerization mechanism, and thermal stability. SEM images showed that polyaniline/vapor grown carbon fiber was at nano-scale, and the microstructure was similar with purified vapor grown carbon fiber, which indicated that the polymerization of aniline occurred on the surface of the carbon fibers. FTIR spectra gave further explanation of the composite mechanism and there was no new bond generated. The maximum power density of the microbial fuel cell with polyaniline/vapor grown carbon fiber as modification with a specific loading of 5 mg/cm² was 299 mW/m², which was 6.5 times higher than the unmodified microbial fuel cell. The EIS spectra fitted well to the Nyquist model and the equivalent circuit model was given. Polyaniline/vapor grown carbon fiber could be regarded as one economical and potential cathode catalyst for oxygen reduction reaction in microbial fuel cell.

Six representative acid-base components are proposed to quantitatively characterize acid-base properties of particulate matter. Micro-titration and determination of water-soluble ion concentrations are applied to water-soluble particulate matter extract, then the acid-base balance principle and the principle of charge conservation are adopted to calculate the concentrations of representative components. Polynomial regression is conducted to analyze the relationship between the amounts of hydrogen ions neutralized by particulate matter of unit mass and the initial pH values of absorption solutions, and a series of empirical equations are obtained, which are applicable to estimate the change in pH derived by the particles absorbed by the precipitation with lower ion concentrations.

Samples for rain water were collected at four sites including Beijing city and Mazhuang Town in the north of China and Shenzhen city and Mangdang Mountain in the southeast of China. The pH values of precipitation, values of conductivity and concentrations of major water soluble ions were measured. The pH values of rainwater in Beijing City, Mazhuang Town, Shenzhen City and Mangdang Mountain were 6. 02, 5. 97, 4. 72 and 4. 81, respectively. The most abundant ions in the rainwater included SO^2-₄,NH⁺₄, Ca²⁺ and NO^-₃.SO^2-₄ was still the major acid ion in rain and NH⁺₄ was the most important neutralizing ion at these four sites. While the rainwater in the north of China was more severely polluted than that in the south, the acidity of the rain was greater in the south than that in the north. Enrichment factor was used to analyze the contribution from sea-water, soil and other sources to rainwater. Hysplit 4. 7 Model was used to indicate different chemical characters among different backward trajectories. The chemical characters of rainwater in Mazhuang Town were distinctly different among different trajectories and it was not significant among different trajectories in Shenzhen City and Mangdang Mountain.

The authors collected and analyzed three rainwater samples in Shenzhen in April and four rainwater samples in a rural area of Taian in July, 2007. The ion species in PM_2.5 and PM₁₀ concentrations were measured to get the influence of washout process of particles on ion concentrations in rainwater. Compared to that in Taian, the rainwater in Shenzhen showed higher ion concentrations and stronger acidity. The washout process made a more important contribution to ion concentrations in rainwater in Taian than in Shenzhen, because Taian had a more serious air pollution. The washout process of particles was very important. The scavenging ratios of Ca²⁺ and Mg²⁺ in PM²⁺ were high for Ca²⁺, Mg²⁺ mostly existed in coarse particles. NO^-₃, NH⁺₄, Cl^- and K⁺ mainly existed in fine particles and had smaller scavenging ratios. SO₂ and H₂SO₄ contributed a lot to the concentration of SO^2-₄ in rainwater and therefore SO^2-₄ had a high scavenging ratio.

A 3-D Eulerian regional air quality model, CAMx, is used to simulate the temporal variation and spatial distribution of PM10 in Beijing during summertime. The results show the prominent temporal and spatial variation characters of PM10. PM10 diurnal variation shows peaks around midnight and in the morning, an increasing trend around noon in urban areas because of the secondary aerosol production from photochemical reactions, a lowest concentration in early evening. The spatial distribution of PM10 has close relation to the source emission and is affected by the secondary aerosol production from photochemical reactions around noon. The secondary aerosol is an important portion of PM10. The secondary aerosol plays a main role on the concentration variation of sulfate and nitrate, while the concentration level and variation of organic carbon aerosol and PM10 is determined mainly by the primary aerosol.

The Comprehensive Air Quality Model with extensions (CAMx), a 3-D Eulerian regional air quality model, was used to simulate the tropospheric photochemical pollution in Beijing and Tianjin areas. Ozone Source Apportionment Technology (OSAT) was applied to track the contributions of multiple source areas and source categories to ozone formation in Beijing. The results showed that the source emissions in the urban and suburban areas of Beijing contributed much to ozone formation in local and downwind areas; among all the source categories, mobile source contributed most to ozone formation, followed by the pollutants from oil products and organic solvents and those emitted by industrial source, while biogenic source and other anthropogenic area source contributed less in Beijing. The results also showed that the ozone episode in Beijing area was regional in extent, meteorological fields and pollutant emissions were important impact factors to ozone formation and distribution.

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.