China Particuology最新文献

Liquid and solid particles in polar stratospheric clouds (PSCs) have been known to play a crucial role in the chemical loss of stratospheric ozone over the Antarctic and Arctic regions in late winter and early spring. The stratospheric aerosol and cloud particles provide the sites where fast heterogeneous chemical reactions convert inactive halogen reservoir species into potential ozone destroying radicals. The sedimentation of nitric acid-containing PSC particles irreversibly removes HNO₃ gas (denitrification) from the lower stratosphere, which slows the return of chlorine to its inactive forms, resulting in more severe stratospheric ozone destruction. Although these clouds have been investigated extensively during the past decade using in situ field observation, laboratory experiment and modeling studies, the detailed microphysics processes under cold stratospheric conditions are still uncertain. This paper reviews the recent advances in our understanding of PSCs.

Traffic-generated fugitive dust is a source of urban atmospheric particulate pollution in Beijing. This paper introduces the resuspension method, recommended by the US EPA in AP-42 documents, for collecting Beijing road-surface dust. Analysis shows a single-peak distribution in the number size distribution and a double-peak mode for mass size distribution of the road surface dust. The median diameter of the mass concentration distribution of the road dust on a high-grade road was higher than that on a low-grade road. The ratio of PM_2.5 to PM₁₀ was consistent with that obtained in a similar study for Hong Kong. For the two selected road samples, the average relative deviation of the size distribution was 10.9% and 11.9%. All results indicate that the method introduced in this paper can effectively determine the size distribution of fugitive dust from traffic.

Aerosol Optical Thickness (AOT), water vapor content and derived Angstrom exponent acquired by a CIMEL sun photometer in Beijing are analyzed. Monthly means computed from quality-assured daily means, seasonal trends and inter-annual variations are presented and discussed. Summer has the highest seasonal average AOT at 440 nm (τ_a440), Angstrom exponent (α_440–870) and water vapor content with the values 0.93, 1.34 and 3.0 cm, respectively. The second highest seasonal average τ_a440 appears in spring with the largest variation of α_440–870 and minimum α_440–870 0.99 due to the impact of coarse particles. The minimum seasonal average τ_a440 (0.44) and water vapor content (0.4 cm) appear in winter. The annual average τ_a440, α_440–870 and water vapor content for about 4-year observation period are 0.70, 1.19 and 1.4 cm, respectively. All monthly average Angstrom exponents are within 0.8-1.4, which indicates aerosol in Beijing is a very complex mixture of both fine- and coarse-mode particles (from anthropogenic influence and natural mineral dust).

The Monsoon Asia Integrated Regional Study (MAIRS) is a new Earth System Science Partnership (ESSP) program aimed at the integrated study of environmental changes over monsoon Asian region. This paper briefly introduces MAIRS, its background and concept, scientific themes and objectives, data requirements and its information system, intensive observation experiment, and its linkage with ongoing international projects.

The objective of this study was to characterize the elemental carbon and organic carbon (EC and OC, respectively) content of aerosol particles (PM_2.5) collected at Tongliao, a site in the Horqin Sandland of northeastern China. During spring 2005, the PM_2.5 mass concentration was 126±71 μg·m⁻³, with higher dust concentrations during five dust storms than on non-dusty days (255±77 vs. 106±44 μg·m⁻³). The average OC and EC concentrations in PM_2.5 determined by a thermal/optical reflectance method were 15.7±7.3 μg·m⁻³ and 3.3±1.7 μg·m⁻³, respectively, and carbonaceous aerosol accounted for 9.9% of the PM_2.5 mass during dust storms compared to 21.7% on normal days. The average ratios of OC to EC during dust storms were similar to those on non-dusty days, and the correlation coefficient between OC and EC was high, 0.86. The high OC/EC ratios, the distributions of eight carbon fractions, and the strong relationship between K with OC and EC indicate that rural biomass burning was the dominant contributor to the regional carbonaceous aerosol.

The present study investigates glass and cement compatibility with a view to use glass as a cement replacement. Amber, flint and green glasses were chosen due to their prevalence in the Greek market as packaging materials. The factors under investigation were the pozzolanicity of the glass cullet, the hydration rate and the mechanical strength development of the cement pastes, as well as the expansion of the specimens due to alkali-silica reaction. Moreover, the potential enhancement of glass pozzolanic activity was examined. The results of the study were encouraging to show the potentiality of utilising glass cullet in cementitious products.

In a novel method for synthesizing ultrafine aluminum hydroxide particles presented in this paper, the morphology and crystal structure of the particles were investigated by TEM, XRD, etc. The process consisted of two steps: chemical precipitation by acid and carbonation. The product has an hourglass or half-hourglass morphology with a narrow size distribution of 150-200 nm. Major endothermal peak of decomposition was found at 270°C by differential thermal analysis. X-ray diffraction identified the product as bayerite. Those properties were compared with those of aluminum hydroxide prepared by carbonization only.

This paper provides a broad review of the existing study on soil aggregate and its responses to land management practices. Soil aggregate is used for structural unit, which is a group of primary soil particles that cohere to each other more strongly than other surrounding particles. The mechanism of soil particle aggregation may be expressed by a hierarchical model, which is based upon the hypothesis that macroaggregates (>250 μm) are collections of smaller microaggregates (<250 μm) held together with organic binding agents. Primary particles form microaggregates and then macroaggregates. Carbon (C)-rich young plant residues form and stabilize macroaggregates, whereas old organic C is occluded in the microaggregates. The interaction of aggregate dynamics with soil organic carbon (SOC) is complex and embraces a range of spatial and temporal processes within macroaggregates and microaggregates. The nature and properties of aggregates are determined by the quantity and quality of coarse residues and humic compounds and by the degree of their interaction with soil particles. The mechanisms resulting in the binding of primary soil particles into stable aggregates vary with soil parent material, climate, vegetation, and land management practices. Land management practices, including tillage methods, residue management, amendments, and soil fertility management, enhance soil aggregation. However, there is still much uncertainty in the dynamics of organic matter in macroaggregation and microaggregation, and research is still needed to understand further the mechanisms of aggregate formation and its responses to human activities.

This work focuses on the production of glass and glass-ceramics by using industrial wastes or by-products, e.g., two fly ashes from the combustion of lignite, a slag from the production of Fe-Ni and a slag from the making of steel. Vitrification took place at 1 350°–1 450°C and crystallization was achieved by heat treatment at 900, 950 and 1 000°C. The capability of the waste to be vitrified and subsequently devitrified was determined by XRD techniques. The crystalline phase depends greatly on the structure of the by-product and the heat treatment. The final products showed low leachability and good hardness.