Shao Longyi

Trace elements pollution and toxicity of airborne PM10 in a coal industrial city

Trace elements in particulate matter associated with coal industries hold high risk to human health. Understanding the contents and occurrences of modes of these elements as well as their contribution to particulate toxicity is significant both environmentally and pathologically. A total of 24 PM10 samples were collected in Pingdingshan City, a coal industrial city in North China, in both winter and summer of 2008. An inductively coupled plasma mass spectrometry (ICP–MS) was used to determine the concentrations of 12 trace elements associated with coal industries (Cr, Ni, Cu, Zn, As, Mo, Cd, Sn, Sb, Tl, Pb, and Bi) in PM10 samples. The results indicated that the trace element concentrations were higher in winter than in summer; due mainly to more coal combustion during winter and to the different meteorological conditions of these two seasons. The soluble proportions of these trace elements compared with total values of intact whole samples were higher in winter than in summer, and this difference was attributed mainly to more SO2 reacting with pre–existing particles to form soluble particles in winter. Of all the analyzed elements, Ni, Tl, Sb, Mo, and Cd occurred mainly in the soluble state (>50% in the soluble fraction), Cr, Cu, Zn, and As occurred in both the soluble and insoluble state (20% to 50% in the soluble fraction), and Sn, Pb, and Bi occurred mainly in the insoluble state (<20% in the soluble fraction). A plasmid DNA assay indicated that winter samples had higher toxicity than summer samples. The correlation of PM10 toxicity (TD50 value) with the contribution of various trace elements to DNA damage (trace element concentration) was further analyzed, and the results indicated that PM10 toxicity was caused mainly by the soluble fractions of trace elements, including those of Ni, Pb, Cu, Cd, As, Zn, Cr, and Tl, which were the major toxic trace elements in Pingdingshan PM10.

The geochemistry and bioreactivity of fly-ash from coal-burning power stations

Fly-ash is a byproduct of the combustion of coal in power stations for the generation of electricity. The fly-ash forms from the melting of incombustible minerals found naturally in the coal. The very high coal combustion temperatures result in the formation of microscopic glass particles from which minerals such as quartz, haematite and mullite can later recrystallize. In addition to these minerals, the glassy fly-ash contains a number of leachable metals. Mullite is a well-known material in the ceramics industry and a known respiratory hazard. Macroscopically mullite can be found in a large range of morphologies; however microscopic crystals appear to favour a fibrous habit. Fly-ash is a recognized bioreactive material in rat lung, generating hydroxyl radicals, releasing iron, and causing DNA damage. However, the mechanisms of the bioreactivity are still unclear and the relative contributions of the minerals and leachable metals to that toxicity are not well known.

Microscopic Morphology and Size Distribution of Residential Indoor PM10 in Beijing City

To investigate characteristics of airborne PM10 in residences in Beijing City the indoor PM10 concentrations, morphology and size distribution were measured using a scanning electron microscope coupled with an energy dispersive X-ray micro-analyser and image analysis. PM10 samples were collected in four homes and from the nearby outdoor environment during the winter season. The results showed that the mean 12-h indoor PM10 concentration was 109.9 g/m3 and the corresponding outdoor level was 179.8 g/m3. Indoor PM10 single particles were subdivided into 5 microscopic types according to their microscopic characteristics and morphologies and included soot aggregates, coal fly ash, mineral, biological and unresolved particles. Each particle type had a different contribution to the PM10 composition which were dominated by soot aggregates in both indoor and outdoor air. Numbersize distribution of PM10 in the residences displayed a bimodal pattern with peaks in 0.1 0.7 m and 1 2.5 m ranges. Coal fly ash exhibited a unimodal pattern in indoor and outdoor air with a peak in 0.1 0.5 m range. Mineral particles showed a bimodal number-size distribution in homes but in the outdoor air they exhibited a unimodal pattern perhaps because of the air temperature.

The Physicochemistry and Toxicology of CFA Particles

The term “technogenic particles” is used to describe airborne particulate matter (PM) produced during industrial processes. The most common of these is “fly ash” produced during combustion of solid and liquid fossil fuels. Coal fly ash is derived from the mineral and metal contaminants within coal in which particles (1) are distinctly spherical in shape, (2) are composed of 60–90% glass, and (3) often contain a range of contaminant metals. In addition, particles may contain recrystallized minerals, mainly quartz, mullite, and hematite; both quartz and mullite are recognized respiratory hazards. Fly ash particles from both UK and Chinese coal-burning power stations were characterized by field emission-scanning electron microscopy (morphology and size), x-ray diffraction (crystallinity and minerals), and inductively coupled plasma–mass spectroscopy (elemental composition). PM10 samples were separated from bulk fly ash by a dry dust separator system. The plasmid scission assay (PSA) was used to measure damage produced by fly ash to plasmid bacteriophage ΦX174 RF DNA. The supercoiled DNA was either damaged or severely damaged by reactive oxygen species (ROS) generated by the fly ash at different concentrations. Geochemical analyses confirmed that the fly ash particles are predominantly glass, with a minor component of the minerals quartz, hematite, and mullite. Fly ash particles also contained a range of metals contaminants; however, these were mostly bound into the glass with only a small proportion potentially bioaccessible. PSA data showed that fly ash exhibited significant oxidative capacity when compared to negative control (MB H2O), indicating that ROS are likely to be the driving force underlying fly ash bioreactivity.

Characteristics and Dolomitization of Upper Cambrian to Lower Ordovician Dolomite from Outcrop in Keping Uplift, Western Tarim Basin, Northwest China

: Late Cambrian to Early Ordovician sedimentary rocks in the western Tarim Basin, Northwest China, are composed of shallow-marine platform carbonates. The Keping Uplift is located in the northwest region of this basin. On the basis of petrographic and geochemical features, four matrix replacement dolomites and one type of cement dolomite are identified. Matrix replacement dolomites include (1) micritic dolomites (MD1); (2) fine–coarse euhedral floating dolomites (MD2); (3) fine–coarse euhedral dolomites (MD3); and (4) medium–very coarse anhedral mosaic dolomites (MD4). Dolomite cement occurs in minor amounts as coarse saddle dolomite cement (CD1) that mostly fills vugs and fractures in the matrix dolomites. These matrix dolomites have δ18O values of −9.7‰ to −3.0‰ VPDB (Vienna Pee Dee Belemnite); δ13C values of −0.8‰ to 3.5‰ VPDB; 87Sr/86Sr ratios of 0.708516 to 0.709643; Sr concentrations of 50 to 257 ppm; Fe contents of 425 to 16878 ppm; and Mn contents of 28 to 144 ppm. Petrographic and geochemical data suggest that the matrix replacement dolomites were likely formed by normal and evaporative seawater in early stages prior to chemical compaction at shallow burial depths. Compared with matrix dolomites, dolomite cement yields lower δ18O values (−12.9‰ to −9.1‰ VPDB); slightly lower δ13C values (−1.6‰–0.6‰ VPDB); higher 87Sr/86Sr ratios (0.709165–0.709764); and high homogenization temperature (Th) values (98°C–225°C) and salinities (6 wt%−24 wt% NaCl equivalent). Limited data from dolomite cement shows a low Sr concentration (58.6 ppm) and high Fe and Mn contents (1233 and 1250 ppm, respectively). These data imply that the dolomite cement precipitated from higher temperature hydrothermal salinity fluids. These fluids could be related to widespread igneous activities in the Tarim Basin occurring during Permian time when the host dolostones were deeply buried. Faults likely acted as important conduits that channeled dolomitizing fluids from the underlying strata into the basal carbonates, leading to intense dolomitization. Therefore, dolomitization, in the Keping Uplift area is likely related to evaporated seawater via seepage reflux in addition to burial processes and hydrothermal fluids.

Oxidative damages to DNA by indoor PM10s: Their relationships with trace element compositions

Plasmid DNA assay and ICP-MS analysis were conducted in order to investigate the bioreactivity of inhalable particles (PM10) and the relationship between bioreactivity and trace element compositions of PM10 in Beijing air. A total of four PM10 samples were carefully selected to represent the indoor and corresponding outdoor environments: one from urban smokers home, two from nonsmokers homes, and the other from the outdoor. In general, the oxidative damage by indoor PMlo was slightly higher than that of outdoor. Among the four sets of samples, the PM10 from the smokers home had a lowest TD50 (toxic dose of PM10 causing 50% DNA to be damaged), being 100 µg·mL−1, suggesting the highest bioreactivity. The heavy metals are believed to be the main reason for oxidative damage to plasmid DNA. The ICP-MS analysis combined with the DNA assay showed that the water-soluble zinc levels had better rela- tionship with TD50 values than other elements, implying that water-soluble zinc might play an important role in the damage of DNA. It is concluded that the PM10 in smokers home had the highest level of water-soluble zinc as well as the lowest TD50 (highest bioreactivity). Iron is considered to be one of the most bioreactive elements, but it will cause little damage to plasmid DNA, probably because iron is mainly in water-insoluble state in Beijing PM10.

Preparation of cordierite from high-alumina fly ash

Fly ash is a potential resource. Utilization of the fly ash with high value-added products is a hot issue in the present. In this paper, using the high-alumina fly ash collected from the Jungar power plant mixed with a small amount of talc powder, sintering of cordierite was conducted by solid-phase reaction. The physical properties of the sintered cordierite samples were determined by water displacement method. The phase composition and the microstructure of the cordierite samples were analyzed with XRD and SEM. The results show that based on the proportion of the fly ash and talc powder designated as 1.6288 : 1, the cordierite samples could be manufactured at the 1350°C and 1370°C for 2 h or/and 3 h, and its physical properties could meet the quality requirements of commercial cordierite. The major phases of the cordierite samples are α-cordierite (indialite); meanwhile, the minor phases are a lesser amount of anorthite and spinel with almost no glass matter.