The terrestrial end-Permian mass extinction in the paleotropics postdates the marine extinction.

The end-Permian mass extinction was the most severe ecological event during the Phanerozoic and has long been presumed contemporaneous across terrestrial and marine realms with global environmental deterioration triggered by the Siberian Traps Large Igneous Province. We present high-precision zircon U-Pb geochronology by the chemical abrasion-isotope dilution-thermal ionization mass spectrometry technique on tuffs from terrestrial to transitional coastal settings in Southwest China, which reveals a protracted collapse of the Cathaysian rainforest beginning after the onset of the end-Permian marine extinction. Integrated with high-resolution geochronology from coeval successions, our results suggest that the terrestrial extinction occurred diachronously with latitude, beginning at high latitudes during the late Changhsingian and progressing to the tropics by the early Induan, spanning a duration of nearly 1 million years. This latitudinal age gradient may have been related to variations in surface warming with more degraded environmental conditions at higher latitudes contributing to higher extinction rates.

[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.

[Sulfuration character of individual particulates of PM10].

SEM/EDX was used to analyze the component and sulfuration characteristics of individual mineral particulates of PM10, which were collected at different times in summer of Harbin. The results indicate that, the 29 species of mineral were identified in summer of Harbin, in which the proportion of clay minerals is over 40%; There are almost no changes in sulfuration in the noon-time period samples, however, the samples collected in the morning and evening show universal sulfuration. In all samples, clay minerals have the highest sulfuration incidence, the average ratio of S/Ca value is 1.0, which is 73 times of noon-sample S/Ca value. The sulfuration degree of samples at different times and meteorological condition show different mechanism of sulfuration. According to different content of mineral elements, mineral grains could be divided into five types: "Si-rich", "Ca-rich", "S-rich", "Fe-rich", "Mg-rich", respectively, showing that the mineral particles mainly come from the crust source; The mineral particles at different times have homology, which indicates that the atmospheric secondary chemical reaction could be the only reason leading to the S rich in morning or evening periods samples, and rule gypsum particles was formed mainly by sulfuration of calcium carbonate mineral salt such as calcite minerals, etc.

[Investigations of microscopic morphology of individual inhalable particulates in Macao in summer].

By means of high resolution field emission scanning electron microcopy (FESEM) and image analysis (IA), microscopic morphologies and the number-size and volume-size distributions of different types of individual inhalable particles collected in Macao in summer of 2007 were investigated. The results showed that the soot aggregates and mineral particles were ubiquitous in the PM10 of Macao in July, 2007. The mineral particles mostly showed an irregular morphology and the soot aggregates displayed chain-like and fluffy morphology. The soot aggregates accounted for approximately 30%-40% in average by number, and the mineral particles accounted for approximately 20%. The relatively higher percentages of more soot aggregates implied that emission from motor vehicle exhausts was serious in Macao during summer. The number-size distributions revealed that the majority of the particles in PM10 of Macao were fine particles, with the equivalent diameter being concentrated in a range from 0.2-0.4 microm. A distinct spatial difference existed in the types of particles collected at different sampling sites. Soot particles dominated the busy transportation sites and the tunnel site, while the mineral particles had a higher proportion at the dock site.

[Individual particle morphology and bioreactivity of PM10 in Beijing during the 2008 Olympic Games].

Inhalable particulates, including PM10 and PM2.5, were collected on the campus of China University of Mining and Technology during the Summer Olympic Games of Beijing in 2008. The mass concentrations of PM10 and PM2.5 were monitored. The morphology and size distribution of individual particles in PM10 and PM2.5 were investigated by a high-resolution Field Emission Scanning Electron Microscopy (FESEM) and image analysis (IA). The toxicity reflected by bioreactivity of PM10 during the Olympic Games was also studied by Plasmid DNA assay. The results showed that the mass levels of PM10 and PM2.5 were well below 81.6 microg x m(-3) and 54.6 microg x m(-3), meeting the second ambient air quality standard of China. The ratio of PM2.5 and PM10 was averaged 0.63, indicating that the PM10 is dominated by fine particles. In terms of microscopic morphology, four types of particles were identified, including spherical particles, soot aggregates, minerals and unresolved fine particles, with the spherical particles and unresolved particles being the predominant components. Most PM10 and PM2.5 particles were in the size range of 0.1-0.4 microm, displaying a unimodal pattern. Volume-size distribution of PM10 exhibited a bimodal pattern with the peaks in 0.4-0.5 pm and 1-2.5 microm, and PM2.5 particles were mainly concentrated in the range of 1-2.5 microm. The results from plasmid assay showed that the bioreactivity of PM10 during the Olympic games was obviously lower than those of past summers, with the TD20 (toxic dosage of PM10 causing 20% plasmid DNA damage) being higher than those of the past summers.

[Morphology and bioreactivity of PM10 in air of Zhengzhou].

PM10 was collected at the urban and suburban sites of Zhengzhou city during autumn. High solution field emission scanning electron microscopy (FESEM) and image analysis (IA) were used to analyse the morphology and size distribution of individual particles in PM10. Plasmid DNA assay was employed to investigate the bioreactivity of PM10. The results showed that the coal fly ash particles were dominated in the PM10 at the urban site while mineral particles were dominated at the suburban site. The number-size distribution showed that the PM10 at the urban site was mainly concentrated in the range of 0.1 microm to 0.4 microm, but the PM10 at the suburban site was scattered in a relatively wider size range. The volume-size distribution demonstrated that the PM10 from both urban and suburban sites occurred mainly in the size range > 1 microm. These facts showed that by number the fine particles were prevailing in the PM10, while by volume (mass) the coarse particles had a major contribution to the total PM10. The results from plasmid assay showed that the bioreactivity of the urban PM10 was obviously higher than that of the suburban PM10.

[Physical and chemical characteristics of individual mineral particles in an urban fog episode].

Field emission scanning electron microscopy (FESEM) and scanning electron microscopy with energy dispersive X-ray detector (SEM-EDX) were used to study the four aerosol samples collected in Beijing air during the fog and non-fog episodes in winter. Size-distribution of mineral particles in fog sample displayed two major peaks at the size range of 0.1-0.3 microm and 1-2.5 microm. EDX analyses indicated that the major chemical compositions varied greatly in the individual mineral particles of the fog and non-fog episodes, especially the sulfur. A total of 9 different mineral categories were classified, namely, "Si-rich", "Ca-rich", "S-rich", "Fe-rich", "Mg-rich", "Al-rich", "Ti-rich", "K-rich" and "Cl-rich". About 55% of the "Ca-rich" in the fog samples comprised of Ca (50% +/- 1.2%)and S (37% +/- 1.6%) and about 72% of the "S-rich" comprised of S (44% +/- 1.5%) and Ca (33% +/- 2%), illustrating that particles with abundant sulfur were also enriched with abundant calcium. It is suggested that the "Ca-rich" alkali minerals could alleviate acidity of the fog water in Beijing air. The S/Ca mean ratio of mineral particles in the fog sample was 6.11, being 8 times higher than the S/Ca mean ratio of the non-fog samples (0.73). This result showed that sulfuration on the surfaces of aerosol particles was extremely severe, and that the conversion efficiency from SO2 to sulfates was relatively high.

Mineralogical characterization of airborne individual particulates in Beijing PM10.

This work mainly focuses on the mineralogical study of particulate matter (PM10) in Beijing. Samples were collected on polycarbonate filter from April, 2002 to March, 2003 in Beijing urban area. Scanning electronic microscopy coupled with energy dispersive X-ray (SEM/EDX) was used to investigate individual mineral particles in Beijing PM10. 1454 individual mineral particulates from 48 samples were analysed by SEM/EDX. The results revealed that mineral particulates were complex and heterogeneous. 38 kinds of minerals in PM10 were identified. The clay minerals, of annual average percentage of 30.1%, were the main composition among the identified minerals, and illite/smectite was the main composition in clay minerals, reaching up to 35%. Annual average percentage of quartz, calcite, compound particulates, carbonates were 13.5%, 10.9%, 11.95%, 10.31%, respectively. Annual average percentage less than 10% were gypsum, feldspar, dolomite, and so on. Fluorite, apatite, halite, barite and chloridize zinc (ZnCl2) were firstly identified in Beijing PM10. Sulfurization was found on surface of mineral particles, suggested extensive atmospheric reaction in air during summer.