[Distribution Characteristics and Sources of Metal Elements in Rainwater in Xiamen].

Forty-one metal elements, including rare earth elements and the lead isotope ratio in rain water in Xiamen were measured by inductively coupled plasma mass spectrometry. Sources of metal elements were identified by combined enrichment factor, isotope analysis, and positive matrix factorization analysis. The results showed that the concentration sequence of total metal elements in rainwater in Xiamen was winter-suburban (213.964 µg·L-1) > winter-urban (176.357 µg·L-1) > summer-suburban (75.401 µg·L-1). There were seasonal and regional differences in the content of rare earth elements, and their standardized distribution patterns were inconsistent with each potential source, indicating that their sources were relatively complex. Enrichment factor analysis showed that Ni, Cu, Zn, and Cd were significantly affected by human sources, whereas Be, Ti, V, Mn, Cr, Co, Ga, Rb, Y, Cs, rare earth elements, Th, and U were mainly affected by natural sources. The result of Pb-isotopic-analysis showed that Pb in rainwater was significantly affected by coal sources with a contribution rate of 63.67%, and soil parent material, garbage incineration, motor vehicle exhaust, and cement dust with a contribution rate of 36.33%. The result of positive matrix factorization combined with the enrichment factor and isotope method showed that the metal elements in rainwater were affected by coal burning, natural sources, industry, and traffic.

Nitrogen isotope composition of ammonium in PM2.5 in the Xiamen, China: impact of non-agricultural ammonia.

Since NH3 is a significant precursor to ammonium in PM2.5 and contributes significantly to atmospheric nitrogen deposition but largely remains unregulated in China, the insight into the source of NH3 emissions by the isotopic investigation is important in controlling NH3 emissions. In this study, atmospheric concentrations of NH3 and water-soluble ion composition in PM2.5 as well as nitrogen isotope ratios in NH4+ (δ15N-NH4+) in Xiamen, China, were measured. Results showed that average NH3 concentration for the five sites in Xiamen was 7.9 µg m-3 with distinct higher values in the warm season and lower values in the cold season, and PM2.5 concentration for the two sites (urban and suburban) was 59.2 µg m-3 with lowest values in summer. In the PM2.5, NH4+ concentrations were much lower than NH3 and showed a stronger positive correlation with NO3- than that with SO42- suggesting the formation of NH4NO3 and equilibrium between NH3 and NH4+. Although the concentrations of NH3 at the urban site were significantly higher than those at the suburban site, no significant spatial difference in NH4+ and δ15N-NH4+ was obtained. The distinct heavier δ15N-NH4+ values in summer than in other seasons correlated well with the equilibrium isotopic effects between NH3 and NH4+ which depend on temperature. The initial δ15N-NH3 values were in the range of waste treatment (- 25.42‰) and fossil fuel combustion (- 2.5‰) after accounting for the isotope fractionation. The stable isotope mixing model showed that fossil fuel-related NH3 emissions (fossil fuel combustion and NH3 slip) contributed more than 70% to aerosol NH4+. This finding suggested that the reduction of NH3 emissions from urban transportation and coal combustion should be a priority in the abatement of PM2.5 pollution in Xiamen.

[Marine Aerosol Using On-board Aerosol Mass Spectrometry].

Marine aerosols were measured in real-time by an on-board signal particle aerosol mass spectrometer(SPAMS) over the Southeast China Sea. The chemical compositions and size distribution characteristics of aerosol particles were obtained, and the sources and ion spectra were analyzed. The results showed that particle number concentration decreased with the distance apart from the coastal area. In the coastal area, the aerosol compositions were mainly determined by the emissions of industry, such as vessel, traffic and coal combustion etc. When it was far from the continent, aerosols were mainly affected by the sea sources. Aerosol particles during the observation period disturbed singly with a peak diameter value of 0.5 µm. Most of the particles were in the size range of 0.2 µm to 0.8 µm. High signal intensity of EC with high K+ intensity in the positive spectrum and HSO4- intensity in negative spectrum was present in the marine aerosol over the coastal area. However, the signals of NO3- and NO2- were absent in the negative spectrum. The signal intensity of EC was weak in the marine aerosol over the sea area far from the coastal area. High signal intensity of Na+ and weak Mg+,Ca+ and NaCl+ signals were present in the positive spectrum, while high signal intensity of MSA-,CN-,O- and HSO4- were present in negative spectrum which was considered to be the special ions spectrum of marine biological sources. It indicated that ambient aerosols over the observation area were influenced not only by the anthropogenic emission sources but also affected by the marine aerosol formation.

[Separation of PM2.5 from coal combustion with phase change].

The influence of two methods of gas moisture conditioning on removal efficiency of PM2.5 from coal combustion with addition of atomized droplets and steam was investigated. The particles size distribution and number concentration were measured in real time by electrical low pressure impactor (ELPI). The results show that collection efficiency of PM2.5 from coal combustion can be highly improved with steam condensational enlargement. Particle stage collection efficiency increases with the particles, especially for those smaller than 0.3 microm. The separation efficiency can be improved by 60% with the size of particles increasing from 0.03 microm to 0.3 microm for 0.1 kg/m3 of steam addition. The removal efficiency is independent of the gas temperature at the inlet of conditioning chamber for steam addition. But it increases with the gas temperature obviously for atomized droplets addition, which can be improved by 30% with increasing gas temperature from 136 degrees C to 256 degrees C. High removal efficiency of PM2.5 from coal combustion can be obtained with atomized droplets evaporation in hot flue gas except for steam addition.