[Investigation of Carbonaceous Airborne Particles by Scanning Proton Microprobe].

Carbonaceous particles are an important component of the atmospheric aerosol particles and important for global climate change, air quality and human health. The PM10 single particles from two environmental monitor locations and seven pollution emission sources were analyzed using scanning proton microprobe (SPM) techniques. The concentration of carbon in individual particles was quantitatively determined by proton non-Rutherford elastic backscattering spectrometry (EBS). The results of this investigation showed that carbonaceous particles were dominant in the pollution sources of coal and oil combustions, diesel busexhaust and automobile exhaust, while inorganic particles were dominant in the sources of steel industry, cement dust and soil dust. Carbonaceous matter was enriched in particles from the city center, while mineral matter was the main component of airborne particles in the industrial area. Elemental mapping of single aerosol particles yielded important information on the chemical reactions of aerosol particles. The micro-PIXE (particle induced X-ray emission) maps of S, Ca and Fe of individual carbonaceous particles showed that sulfuration reaction occurred between SO2and mineral particles, which increased the sulfur content of particles.

Evolution Law of Helium Bubbles in Hastelloy N Alloy on Post-Irradiation Annealing Conditions.

This work reports on the evolution law of helium bubbles in Hastelloy N alloy on post-irradiation annealing conditions. After helium ion irradiation at room temperature and subsequent annealing at 600 °C (1 h), the transmission electron microscopy (TEM) micrograph indicates the presence of helium bubbles with size of 2 nm in the depth range of 0-300 nm. As for the sample further annealed at 850 °C (5 h), on one hand, a "Denuded Zone" (0-38 nm) with rare helium bubbles forms due to the decreased helium concentration. On the other hand, the "Ripening Zone" (38-108 nm) and "Coalescence Zone" (108-350 nm) with huge differences in size and separation of helium bubbles, caused by different coarsening rates, are observed. The mechanisms of "Ostwald ripening" and "migration and coalescence", experimentally proved in this work, may explain these observations.

Characterization and Cytotoxicity of PM<0.2, PM0.2-2.5 and PM2.5-10 around MSWI in Shanghai, China.

BACKGROUND: The potential impact of municipal solid waste incineration (MSWI), which is an anthropogenic source of aerosol emissions, is of great public health concern. This study investigated the characterization and cytotoxic effects of ambient ultrafine particles (PM<0.2), fine particles (PM0.2-2.5) and coarse particles (PM2.5-10) collected around a municipal solid waste incineration (MSWI) plant in the Pudong district of Shanghai. METHODS: Mass concentrations of trace elements in particulate matter (PM) samples were determined using ICP-MS (Inductively Coupled Plasma Mass Spectrometry). The cytotoxicity of sampled atmospheric PM was evaluated by cell viability and reactive oxygen species (ROS) levels in A549 cells. RESULT: The mass percentage of PM0.2-2.5 accounted for 72.91% of the total mass of PM. Crustal metals (Mg, Al, and Ti) were abundant in the coarse particles, while the anthropogenic elements (V, Ni, Cu, Zn, Cd, and Pb) were dominant in the fine particles. The enrichment factors of Zn, Cd and Pb in the fine and ultrafine particles were extremely high (>100). The cytotoxicity of the size-resolved particles was in the order of coarse particles < fine particles < ultrafine particles. CONCLUSIONS: Fine particles dominated the MSWI ambient particles. Emissions from the MSWI could bring contamination of anthropogenic elements (Zn, Cd and Pb) into ambient environment. The PM around the MSWI plant displayed an additive toxic effect, and the ultrafine and fine particles possessed higher biological toxicity than the coarse particles.

Characteristics of secondary inorganic aerosol and sulfate species in size-fractionated aerosol particles in Shanghai.

Sulfate, nitrate and ammonium (SNA) are the dominant species in secondary inorganic aerosol, and are considered an important factor in regional haze formation. Size-fractionated aerosol particles for a whole year were collected to study the size distribution of SNA as well as their chemical species in Shanghai. SNA mainly accumulated in fine particles and the highest average ratio of SNA to particulate matter (PM) was observed to be 47% in the fine size fraction (0.49-0.95 µm). Higher sulfur oxidation ratio and nitrogen oxidation ratio values were observed in PM of fine size less than 0.95 µm. Ion balance calculations indicated that more secondary sulfate and nitrate would be generated in PM of fine size (0.49-0.95 µm). Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra of typical samples were analyzed. Results revealed that sulfur mainly existed as sulfate with a proportion (atomic basis) more than 73% in all size of PM and even higher at 90% in fine particles. Sulfate mainly existed as (NH4)2SO4 and gypsum in PM of Shanghai. Compared to non-haze days, a dramatic increase of (NH4)2SO4 content was found in fine particles on haze days only, which suggested the promoting impact of (NH4)2SO4 on haze formation. According to the result of air mass backward trajectory analysis, more (NH4)2SO4 would be generated during the periods of air mass stagnation. Based on XANES, analysis of sulfate species in size-fractionated aerosol particles can be an effective way to evaluate the impact of sulfate aerosols on regional haze formation.

[Study on transition metals in airborne particulate matter in Shanghai city's subway].

PM10 and PM2.5 aerosol particle samples were collected at a subway station in Shanghai and their morphology, chemical composition and transition metal species were studied. The mass concentrations of PM10 and PM2.5 inside the subway station were significantly higher than those measured in aboveground ambient air. The PM levels inside subway were much higher than the state control limit. The aerosol composition in the metro station was quite different from that of the aboveground urban particles. Concentrations of Fe, Mn and Cr were higher than the averages of aboveground urban air particles by factors of 8, 2, and 2, respectively, showing a substantial enrichment in subway. Scanning electron microscope (SEM) analysis showed that the subway particles had flat surfaces in combination with parallel scratches and sharp edges and looked like metal sheets or flakes. Furthermore, analysis of the atomic composition of typical subway particles by energy dispersive X-Ray (EDX) spectroscopy showed that oxygen and iron dominated the mass of the particles. The X-ray absorption near-edge structure (XANES) spectroscopy results showed that a fraction (> 26%) of the total iron in the PM10 was in the form of pure Fe, while in the street particles Fe(III) was shown to be a significant fraction of the total iron. The work demonstrated that the underground subway stations in Shanghai were an important microenvironment for exposure to transition metal aerosol for the people taking subway train for commuting every day and those who work in the subway stations, and the metal particle exposure for people in the subway station should not be ignored.

Sulfur speciation and bioaccumulation in camphor tree leaves as atmospheric sulfur indicator analyzed by synchrotron radiation XRF and XANES.

Analyzing and understanding the effects of ambient pollution on plants is getting more and more attention as a topic of environmental biology. A method based on synchrotron radiation X-ray fluorescence and X-ray absorption near edge structure spectroscopy was established to analyze the sulfur concentration and speciation in mature camphor tree leaves (CTLs), which were sampled from 5 local fields in Shanghai, China. Annual SO2 concentration, SO4(2-) concentration in atmospheric particulate, SO4(2-) and sulfur concentration in soil were also analyzed to explore the relationship between ambient sulfur sources and the sulfur nutrient cycling in CTLs. Total sulfur concentration in mature camphor tree leaves was 766-1704 mg/kg. The mainly detected sulfur states and their corresponding compounds were +6 (sulfate, include inorganic sulfate and organic sulfate), +5.2 (sulfonate), +2.2 (suloxides), +0.6 (thiols and thiothers), +0.2 (organic sulfides). Total sulfur concentration was strongly correlated with sulfate proportion with a linear correlation coefficient up to 0.977, which suggested that sulfur accumulated in CTLs as sulfate form. Reduced sulfur compounds (organic sulfides, thiols, thioethers, sulfoxide and sulfonate) assimilation was sufficed to meet the nutrient requirement for growth at a balanced level around 526 mg/kg. The sulfate accumulation mainly caused by atmospheric sulfur pollution such as SO2 and airborne sulfate particulate instead of soil contamination. From urban to suburb place, sulfate in mature CTLs decreased as the atmospheric sulfur pollution reduced, but a dramatic increase presented near the seashore, where the marine sulfate emission and maritime activity pollution were significant. The sulfur concentration and speciation in mature CTLs effectively represented the long-term biological accumulation of atmospheric sulfur pollution in local environment.

Atmospheric lead pollution in fine particulate matter in Shanghai, China.

The Pb-monitoring program was extended for 6 years from 2002 to 2007 at 17 representative urban sites (6 traffic, 5 industrial, and 6 residential sites), and 3 suburban sites to assess the lead pollution in fine particulate matter (PM2.5) after phasing out leaded gasoline in Shanghai. Compared with Pb levels reported in other places, the Pb pollution in Shanghai is still serious after phasing out leaded gasoline, which remains at high concentration range (213-176 ng/m3) in PM2.5 in winter. Significant spatial variation of Pb concentrations and strong seasonal variation of higher Pb concentration in winter than that in summer were detected. The size distribution of Pb in particulate matter has a unimodal mode that peaks at approximately 0.154-1.59 microm particle diameter, indicating that Pb is mainly concentrated in fine fraction. Lead in the fine fraction is enriched by a factor of 10(3)-10(4) relative to Pb abundance in crust. Eight categories of Pb pollution sources were identified in the PM2.5 in the winter of 2007 in Shanghai. The important emission sources among them are vehicle exhaust derived from combustion of unleaded gasoline, metallurgic industry emission, and coal combustion emission.

[Elemental size distribution of airborne fine and ultrafine particulate matters in the suburb of Shanghai, China].

The elemental size distributions of airborne fine/ultrafine particulate matters in the suburb of Shanghai were studied using synchrotron X-ray fluorescence. Median mass aerodynamic diameter (MMAD), elemental correlation coefficient as well as enrichment factor (EF) of each size fraction were calculated to characterize the sources of elements in fine/ultrafine particulate matters. Ca and Ti distributed mainly in coarse particles (> 2 microm) with size independent enrichment factors between 0.1 and 3.2, and the correlation coefficient between Ca and Ti was as high as 0.933, which implied strong contribution from nature sources, such as soil dusts and resuspended dusts. However, V, Cr, Mn, Ni, Zn, Cu, Pb, Cl, S mainly distributed in 0.1-1.0 microm particulate matters with MMAD between 0.56-0.94 microm. The EF of V, Cr, Ni, Cu, Zn, Pb increased with decreasing particle size. The highest EF were found for Pb in ultrafine particulate matters (< 0.1 microm) with EF of 2,023.7-2,244.2. The evidences suggested that these elements were significantly influenced by anthropogenic sources and enriched in fine/ultrafine particles smaller than 1 microm. Fe distributed uniformly in the particles larger than 0.2 microm with MMAD of 1.3 microm. The results indicated non-negligible influences of remote transmission of anthropogenic pollutions.

[Bioindicating function of sulfur in Haplocladium under heavy metals pollution by SRXRF and XANES].

Haplocladium was cultivated in a special prepared nutrient medium containing different concentrations of Pb, Fe and Cr in laboratory. The sulfur content in moss was measured by synchrotron radiation X-ray fluorescence (SRXRF), and the percentage of various oxidation states of sulfur was analyzed by X-ray absorption near-edge structure (XANES) spectrum. The results show that the sulfur absorption increases under exposure to heavy metal ions of Pb and Fe, but it decreases under exposure to 400 mg/L Pb and 200 mg/L Fe. When Haplocladium was cultivated for 15 days, under the stress of 100 mg/L Pb, the relative content of low oxidation states sulfur increases from 17.8% to 23.6% and the sulfate sulfur decreases from 56.3% to 51.2%. Under the stress of 400 mg/L Pb, the relative content of low oxidation state sulfur increases from 17.8% to 24.8%, and the sulfate sulfur decreases from 56.3% to 48.4%. Under heavy metal exposure, the total relative content of low oxidation states sulfur such as cystine, cysteine, methionine and glutathione increases, and the relative content of sulfate sulfur apparently decreases. All these results indicate that the changing characteristics of sulfur content and oxidation states percentage in sulfur assimilation process under heavy metal exposure can be used as a bioindicator of heavy metal pollution.