Fine particle trace elements at a mountain site in southern China: Source identification, transport, and health risks.

Trace elements in atmospheric particulate matter play a significant role in air quality, human health, and biogeochemical cycles. In this study, the trace elements (Ca, Al, K, Fe, Na, Mg, Zn, Pb, Mn, Ti, Cu, Cr, Sr, Ni) in PM2.5 samples collected at the summit of Mt. Lushan were analyzed to quantify their abundance, source, transport, and health risks. During the whole sampling period, the major trace elements was Ca, Al, and K. While the trace metals with the lowest concentrations were Sr, Ni, Rb, and Cd. The trace elements were influenced by air mass transport routes, exhibiting an increasing trend of crustal elements in the northwesterly airmass and anthropogenic elements (Zn, Mn, Cu, and Ni) in the easterly air masses. Construction dust, coal + biomass burning, vehicle emission, urban nitrate-rich + urban waste incineration emissions, and soil dust + industry emissions were common sources of PM2.5 on Mt. Lushan. Different air mass transport routes had various source contribution patterns. These results indicate that trace elements at Mt. Lushan are influenced by regional anthropogenic emissions and monsoon-dominated trace element transport. The total resulting cancer risk value that these elements posed were below the acceptable risk value of 1 × 10-6, while the non-carcinogenic risk value (1.72) was higher than the safety level, suggesting that non-carcinogenic effects due to these trace elements inhalation were likely to occur. Vehicle emission and coal + biomass burning were the common dominant sources of non-cancer risks posed by trace elements at Mt. Lushan.

Mineralogical similarities and differences of dust storm particles at Beijing from deserts in the north and northwest.

Dust storm particles have been one of the important contributors to global aerosol loading, affecting human health and climate system. Beijing, a megapolitan city, experienced two severe dust storms in spring of 2015, with maximum hourly-mean PM10 mass concentrations exceeding 1000 µg/m3. The first dust storm (Dust 1) was from east area of Gobi Desert about 850 km in the north of Beijing and the second (Dust 2) was from west area of Gobi Desert about 1500 km in the northwest of Beijing. Morphologies and elemental compositions of dust particles were identified using high-resolution electron microscopy. The statistical analysis showed that the number fractions of mineral dust particles during the two dust storm episodes were 85.3% and 95.4%, respectively. Clay minerals were the most abundant among mineral particles, with a number fraction larger than 50%, followed by quartz particles (17.3% and 14.8%) and feldspar. Feldspar and carbonate particles accounted for 14.8% and 3.4% of mineral particles in Dust 1, and 9.9% and 13.6% in Dust 2, with the difference due to the different source areas. When the dust storms directly migrated to Beijing, the occurrence of S-containing mineral particles and the relative weight ratio of S in individual mineral particles were extremely low, indicating limited production of sulfate on the dust-storm particles in the atmosphere, regardless of the differences of source areas, migration paths, and mineralogical components. After the peaks of dust storms passed, the occurrence of S on the mineral particles were much higher, although the relative weight ratios of S in the mineral particles was still very small. This result suggests that most of the mineral particles underwent heterogeneous reactions, but the reaction rates were low.

Distribution of rare earth elements in PM10 emitted from burning coals and soil-mixed coal briquettes.

Emission from burning coals is one of the major sources of the airborne particles in China. We carried out a study on the rare earth elements (REEs) in the inhalable particulate matter (PM10) emitted from burning coals and soil-coal honeycomb briquettes with different volatile contents and ash yields in a combustion-dilution system. Gravimetric analysis indicates that the equivalent mass concentration of the PM10 emitted from burning the coals is higher than that emitted from burning the briquettes. The ICP-MS analysis indicates that the contents of total REEs in the coal-burning PM10 are lower than those in the briquette-burning PM10. In addition, the contents of the light rare earth elements (LREEs) are higher than those of the heavy rare earth elements (HREEs) in the PM10 emitted from burning the coals and briquettes, demonstrating that the REEs in both the coal-burning and briquette-burning PM10 are dominated by LREEs. The higher contents of total REEs and LREEs in the coal-burning PM10 are associated with the higher ash yields and lower volatile contents in the raw coals. A comparative analysis indicates that the La/Sm ratios in the PM10 emitted from burning the coals and briquettes, being lower than 2, are lower than those in the particles from gasoline-powered vehicle emission.

Morphology and composition of particles emitted from a port fuel injection gasoline vehicle under real-world driving test cycles.

Traffic vehicles, many of which are powered by port fuel injection (PFI) engines, are major sources of particulate matter in the urban atmosphere. We studied particles from the emission of a commercial PFI-engine vehicle when it was running under the states of cold start, hot start, hot stabilized running, idle and acceleration, using a transmission electron microscope and an energy-dispersive X-ray detector. Results showed that the particles were mainly composed of organic, soot, and Ca-rich particles, with a small amount of S-rich and metal-containing particles, and displayed a unimodal size distribution with the peak at 600 nm. The emissions were highest under the cold start running state, followed by the hot start, hot stabilized, acceleration, and idle running states. Organic particles under the hot start and hot stabilized running states were higher than those of other running states. Soot particles were highest under the cold start running state. Under the idle running state, the relative number fraction of Ca-rich particles was high although their absolute number was low. These results indicate that PFI-engine vehicles emit substantial primary particles, which favor the formation of secondary aerosols via providing reaction sites and reaction catalysts, as well as supplying soot, organic, mineral and metal particles in the size range of the accumulation mode. In addition, the contents of Ca, P, and Zn in organic particles may serve as fingerprints for source apportionment of particles from PFI-engine vehicles.

Characteristics and aging of traffic-derived particles in a highway tunnel at a coastal city in southern China.

Road traffic is one of the major sources of particulate matters in the atmosphere. Tunnels provide a semi-closed place to measure traffic-derived particles before the particles were photo-chemically modified in the open air. In this study, aerosol particles were collected in a tunnel, and an urban site for comparison at a coastal city in south China. The particles were analyzed by using a transmission electron microscope coupled with an energy-dispersive X-ray spectrometry. There were four groups of particles according to sources: tailpipe-emitted particles, wear debris, road dust, and secondary particles. Tailpipe-emitted particles included soot, organic, and a part of sulfate and metal particles. Wear debris were characterized by their distinct metal components. Road dust was composed of mineral particles and fly ash. Secondary particles were some sulfate particles and mixture particles. Sulfate particles were further divided into two subtypes: with and without organic coating. Sulfate particles with organic coating accounted for 56.2% of total sulfate particles in the tunnel, while the percentage was 36.9% at the urban site, indicating that sulfate particles were more easily coated by organics in the tunnel than the urban site. However, the aging degree of sulfate particles in the tunnel was weaker than that at the urban site, which was attributed to the absence of photochemical reactions in the tunnel environment. Some mixture particles had a core-shell structure (C-S particles). The composition and morphologies of the cores of the C-S particles were similar to those of mineral, metal, and mixture particles. The shells of the C-S particles were mainly composed of organics. The C-S particles were more aged than the sulfate particles with coating in the tunnel environment, suggesting that mineral and metal components could efficiently enhance particle aging in the absence of photochemical reactions.

[Oxidative Capacity of the PM10 and PM2.5 in Beijing During 2014 APEC].

In order to evaluate the effect of the joint air pollution prevention and control program on the toxicity of the airborne particles in Beijing during the APEC conference, we collected the PM10 and PM2.5 (particulate matter with aerodynamic diameters of less than 10 µm and 2.5 µm respectively) from October to December in the urban district of Beijing, and analyzed the oxidative capacity of the particles by plasmid scission assay. The results indicated that the oxidative capacity of PM10 was higher than that of PM2.5 during the APEC conference, and that the damage rate of supercoiled DNA by the samples increased with their experimental dose levels. The TD30 (toxic dose of PM causing 30% of plasmid DNA damage, unit: µg·mL-1) was used to indicate the oxidative capacity and the lower TD30 values indicated higher oxidative capacity. The TD30 values of the PM samples before, during, and after APEC conference displayed a descending order of during APEC (November) >before APEC (October) >after APEC (December), which indicated a decreasing order of the PM oxidative capacity of after APEC (November) >before APEC (October) >during APEC. The TI (toxic index) was further introduced to represent the human exposure risk of particles, which was represented by the product of the mass concentration of PM (µg·m-3) and the DNA damage percentages under the PM dose of 250 µg·mL-1 (%). Compared with the TI values of previous years, the TI value of the 2014 APEC PM was lower than that of 2004, but higher than that of the 2008 Olypic Games, suggesting that the exposure risk of airborne particles decreased obviously with the increase of policy control strength.