[Pollution Characteristics and Source Analysis of Carbon and Nitrogen Components in Ambient PM2.5 in Huangshi City].

Based on stable isotope technology and a PMF model, the pollution characteristics and sources of carbon and nitrogen components in ambient PM2.5 in Huangshi City were explored. The results showed that the total carbon concentration[ρ(TC)] and the total carbon isotopic composition (δ13CTC) in ambient PM2.5 in Huangshi City both showed seasonal variation characteristics of being high in winter and low in summer, with values of (4.4±1.2) µg·m-3 and (-26.3±0.5)‰ in summer and (9.9±3.5) µg·m-3 and (-25.5±0.5)‰ in winter, respectively. The total nitrogen concentration[ρ(TN)]was significantly lower in summer[(9.1±9.1) µg·m-3]than that in winter[(62.4±26.4) µg·m-3], whereas the total nitrogen isotopic composition (δ15NTN) was obviously enriched in summer[(12.8±1.9)‰]compared with that in winter[(2.9±4.0)‰]. In addition to the contribution from local sources, the carbon and nitrogen components were mainly affected by the short-range regional emission in northern Hunan and the long-distance transport in the northwest. The MixSIAR model and the PMF model indicated that the vehicle emission source was the main source of carbon components in PM2.5, with contribution rates of 38.9% and 39.3%, respectively. MixSIAR results showed that NOx emission sources had a greater impact on nitrogen components in PM2.5 of different seasons than NH3 emission sources, and their contribution was higher in summer (80%) than that in winter (66.8%), among which the NOx emissions from coal combustion (summer:36.1%; winter:20.2%) had the largest contribution. By contrast, the PMF model indicated that the main source of nitrogen components was vehicle emissions (59.8%). Combining multiple models to overcome the uncertainty and subjectivity of single-model analysis can provide a theoretical basis for actively controlling and reducing fine particulate matter emissions and effectively dealing with urban aerosol pollution.

[Effect of WESP on Emission Characteristics of Condensable Particulate Matter from Ultra-low Emission Coal-fired Power Plants].

In order to study the effect of wet electrostatic precipitators(WESP) on emission characteristics of condensable particulate matter (CPM) from ultra-low emission coal-fired power plants that are under different capacity conditions, a set of CPM sampling devices was built based on US EPA Method 202, and an ultra-low emission coal-fired power plant was detected. This study evaluated the emission level of the CPM from the flue gas of coal-fired power plants, the effects of different unit capacity conditions on the CPM emission concentrations, and the removal efficiency of WESP for different components of the CPM. The results suggested that the emission concentrations of the CPM from ultra-low emission power plants were 27.27 mg·m-3 and 28.71 mg·m-3under the conditions of 75% and 100% capacity, respectively. The removal efficiencies of WESP for the CPM were 35.59% and 27.59%, respectively. SO42- was the main component of water-soluble ions of the CPM. The proportion of SO42- in inorganic components of the CPM reached more than 65% under different capacity conditions. In addition, the removal efficiency of WESP for Cl-, K+, Ca2+, Mg2+, Na+, and other inorganic ions reached 30%-50%, but the mass concentrations of SO42- and NO3- increased.

Seasonal variations and chemical characteristics of PM(2.5) in Wuhan, central China.

PM2.5 samples were collected at an urban site (WD) and a suburban site (TH) in Wuhan from August 2012 to July 2013. The mass concentrations of water-soluble inorganic ions, carbonaceous species and elements of PM2.5 were measured. The annual mean concentrations of PM2.5 were 106.5 µg/m(3) and 114.9 µg/m(3) at WD and TH, respectively. The chemical compositions of PM2.5 at WD were similar to those at TH and the fractions of the major components of PM2.5 in Wuhan were in the following order of trace elements