Special Issue

Trends and countermeasures of the environmental problems concerning suspended particulate matter (SPM)

Review

Environmental Problems due to Suspended Particulate Matter and Future Research and Development

Abstract

Despite much efforts for mitigation of SPM emission, atmospheric environmental pollution due to SPM is still at high level, and it is required to elucidate the causes and to apply further countermeasures.　Here, 1) present state of SPM pollution, 2) amounts of SPM emitted from anthropogenic sources, 3) amounts of precursor compounds (SOx, NOx, hydrocarbons and others) which are transformed to SPM, emitted from anthropogenic sources, 4) mechanisms of secondary SPM formation, and 5) contribution of each emission source to atmospheric SPM concentration, are reviewed here.　Targets of research and development responding to the SPM environmental issues are summarized as well.

Key words: Suspended Paticulate Matter(SPM), State of Pollution, Emission Sources, Secondary Particles, Contribution Ratio

(Language:Japanese)

Review

Environmental Assessment with respect to Suspended Particulate Matter

Abstract

Air pollution due to suspended particulate mattear (SPM) has long been an outstanding problem in major urban areas. Technical difficulties in environmental assessment of SPM is one reason for the standstill. Here, assessment means estimating the change in ambient concentration resulting from changes in pollution sources, and judging the allowability with reference to the regulated standard values. Actually SPM includes various chemical components, which originate not only from anthropogenic sources but also from natural processes, so that exact estimation of their inventories is quite difficult. It is also difficult to explain the behaviors of secondary particles, which are composed of gaseous pollutants in ambient air. Since the 1980s, however, these complex behaviors of SPM have been analyzed, and modeling has advanced to give practically available assessment techniques.

Whereas long-term average concentrations are estimated in the assessment system for SO₂ and NOx, a short-term time-dependent model is effective to simulate the behavior of photochemical oxidants (Ox) as it causes acute damage to human health. In case of SPM, adaptation of the long-term assessment system has been one approach. From another point of view, however, episodes of severe SPM pollution tend to occur in such specific seasons as early winter and the rainy season in early summer. This occurrence pattern is similar to that of Ox, and therefore modeling of detailed behaviors of SPM components has been advanced with a view to a short-term assessment system.

Key words: suspended particulate matter, long-term simulation, time-dependent simulation,gas-particle conversion

(Language: Japanese)

Review

Monitoring of suspended particulate matter in the atmosphere : A review

Abstract

The environmental standard criteria of suspended particulate matter (SPM) was promulgated by the Environment Agency of Japan in January 1972. Since then, the average mass concentration has decreased about 60 percent compared with the value of 1972, but it is found that the tendency of the improvement is not changed in recent years. In addition to such domestic circumstances, the new environmental regulation of PM2.5 was added to PM10 in the United States in 1997. Considering those circumstances concerning environmental SPM in Japan, it is necessary to reexamine domestic standard measurement methods. In this paper, the domestic situation for the measurement techniques of the SPM and the background of the PM2.5 regulation in United States are explained, and the future problems are described.

Key words: Fine particles, Measurement techniques, Environmental quality standard, PM2.5

(Language:Japanese)

Technical Report

Properties on Condensed Particulate Matter from Stationary Sources

Abstract

Properties of condensed particulate matter in heavy oil combustion flue gas were investigated using a test duct which could control temperature of flue gas optionally.

The main results obtained through the examination were as follows.

1. The dust color which was sampled with parts of high temperature was black, but the condensed particulate matter which was sampled with a part of low temperature is light brown, and the smell was stimulating.
2. The concentration of the condensed particulate matter at a part of low temperature was large, 2~4 times compared with dusts at high temperature.
3. The sharp of the condensed particulate matters were filmy and droplets extended to 10 several µm.
4. In the component ratio of organic carbon and elemental carbon, there was no difference in the condensed particulate matter and the dust. On the other hand, in solution component of SO₄^2-, the condensed particulate matter was large with 90 % for 50~70 % dust. Also, by the component concentration, a large quantity of absorption or adsorption of SO₂ produced approximately 8 times of the amount of dust in the condensed particulate matter.

Key words: Dust, Condensed Particulate Matter, Particle Measurement, SO₄^2-, SO₂

(Language:Japanese)

Review

A way to suppress suspended particulate matter

Abstract

Suspended Particulate Matter (SPM) is receiving great attention because of its potential hazards to health. We can contribute to solve this problem by applying electrical discharge to suppress dust and condensible gases, which may lead to the production of SPM, in atmosphere. The electrical discharge will produce radicals, excited molecules, ions, etc. which will effectively lead to new chemical reactions. Recent technological progresses to precipitate fine particles and to detoxicate (decompose) condensible gases from factories, automobiles, etc. are introduced in this article.

Key words: dust, particle, gas, decomposition, discharge

(Language:Japanese)

Review

Diesel Fuel Property and Characteristics of Particulate Matter Emission

Abstract

The relation between diesel fuel property and characteristics of particulate matter (PM) emission was explained based on results acquired in our laboratory.

The effects of cetane number on PM emission were noticed, but a fixed relation between the parameters was not found. Concerning distillation property of fuels, such effects on PM emission were not found for the single-cylinder engine test under a stationary operating condition, but it was found that the increase of heavy fractions in the fuels increased PM emission for a diesel passenger car tested under a transient operating condition such as a 10 mode test procedure.　It was to be noted that this tendency was higher for the car conforming to the latest emission standard.

The aromatic carbon atom content (Ca) in the fuels, comprising aromatic samples separated from fractions distilled in every 40°C range, was correlated with PM emission. By using pure hydrocarbon mixed fuels for investigating a relation between chemical structure of the fuels and PM emission, quaternary atom content (C-aro) in aromatic rings and carbon/hydrogen atomic ratio (C/H)showed the highest correlation with PM emission, but other parameters such as Ca, tertiary carbon atom content in aromatic rings and I.S. index showed also high correlation coefficients.

Concerning the test fuel with all the gas oil fractions, it was confirmed that the fuel's aromatic parameters strongly affect PM emission for both the single-cylinder engine tested under stationary operating and the diesel passenger car tested under transient operating condition. Four parameters such as Ca, C-aro, C/H and I.S. index showed high correlation coefficients with PM emission which was higher than a fuel factor representing aromatic contents as volume percentages which had been extensively used.

Key words: Gas oil, Aromatics, Particulate matter, Emission

(Language:Japanese)

Review

Catalytic techniques to remove diesel exhaust particulates

Abstract

In relation to the diesel particulate filter (DPF), which is a promising technique for substantially reducing the particulate matter (PM), the screening and development of catalysts to improve the oxidation of PM, especially the solid carbon (soot), have been reviewed.

Improvement in the engine combustion technique have been conventionally the main countermeasure for the reduction of PM, but stringent regulations, which should be met in the near future, are demanding developments for practical exhaust treatment technique using the DPF. The use of a catalyst, which substantially lowers the soot ignition temperature, is effective to put the DPF technique in practice. In order to influence the catalytic activity upon solid carbon (soot), two types of catalysts, mobile-molten-salt-type and indirect-oxidation-type using coexisting NO in the exhaust gas, are thought to be promising. Concerning the latter type catalyst, the authors have found that SO₃, made on Pt catalysts from SO₂ also coexisting in the exhaust gas, has a strong catalysis for the promotion of soot oxidation with NO₂.

Key words: diesel, exhaust, particulates, soot, catalyst, filter

(Language:Japanese)

Review

Photochemical Reactions for Polycyclic Aromatic Hydrocarbons in Atmospheric Particulate Matters

Abstract

Atmospheric particulate matters contain polycyclic aromatic hydrocarbons (PAHs), which are suspected of being carcinogenic, mutagenic and estrogen disrupting agents. PAHs are mostly distributed among sub-micron particles, which can be travel far from emission sources, and are subject to transformation by photochemical or dark reactions with various gases (e.g. O₂, O₃, NO, N₂O₅) in the atmosphere. This article summarizes important research results on photochemical behavior of PAHs: the gas-solid(particle) phase distribution, photooxidation and nitration, in atmospheric particulate matters.

Key words: Polycyclic aromatic hydrocarbon, Photooxidation, Nitration,Atmospheric particulate matters

(Language:Japanese)

Review

Separation technology with hydrates

Abstract

Hydrates have peculiar crystal structure such that one guest molecule is surrounded with a cage composed by water molecules. These water molecules are connected to each other by hydrogen bonding, but there is no chemical bonding between the guest molecule and the water molecules.

The necessity of applied research occurred at first in the energy industry to prevent hydrates formation in pipelines. In addition, recently methane hydrates have been highlighted as a future energy resource. The unique structure and characteristics of hydrates seem to be finding many industrial applications.

In this short monograph I present other possibilities of hydrates' application. The cage-like structure of hydrates can be utilized as a gas separation technique since in mixture hydrates the mole fraction of components in a hydrate phase is different from that in a gas phase. The outline and principle of this technique is considered to be similar to the separation technology using phase equilibrium. Thus firstly the separation technology using phase equilibrium is briefly described, then properties of hydrates concerning the separation technology are summarized concisely. After that the separation technology with hydrates is introduced.

Key words: Hydrate, Separation, Environmental pollutant, Phase equilibrium

(Language:Japanese)