Feature of Dust Particles in the Spring Free Troposphere over Dunhuang in Northwestern China: Electron Microscopic Experiments on Individual Particles Collected with a Balloon-borne Impactor

Free tropospheric aerosol particles were collected using a balloon-borne particle impactor in August of 2002 and March of 2003 at Dunhuang in northwestern China (40°00′N, 94°30′E), and the morphology and elemental composition of the aerosol particles were analyzed in order to understand the mixing state of coarse dust particles (diameter >1 μm) over the desert areas in the Asian continent in spring. Electron microscopic experiments on the particles revealed that dust particles were major constituents of coarse mode particles in the free troposphere over the Taklamakan Desert in spring and summer. Si-rich or Ca-rich particles are major components of dust particles collected in the free troposphere over dunhuang and the values of [number of Ca-rich particles]/[number of Si-rich particles] differs markedly between spring and summer, being about 0.3 in the spring of 2003 and about 1.0 in the summer of 2002 at heights 3–5 km above sea level. It is likely that the condition of the ground surface and the strength of vertical mixing in source areas of Asian dust are potential factors causing the difference in the chemical types of dust particles. Comparison of the elemental compositions of these particles with those of particles collected over Japan strongly suggests that these particles were chemically modified during their long-range transport in the free troposphere. Analysis of wind systems shows that both the predominating westerly wind in the free troposphere and the surface wind strongly controlled by the geographical structure of the Tarim Basin are important in the long-range transport of KOSA particles originating in the Taklamakan Desert.     

Anthropogenic Calcium Particles Observed in Beijing and Qingdao, China

Analysis of individual particles collected at Beijing in northern China revealed that particles abundant in calcium (Ca) always constituted a large fraction of mineral particles in the urban atmosphere. The particles were characterized by cubic morphologies. The major mineral element in the particles was Ca and few or no other mineral elements were detected. A large number of the particles were in the range of diameter <1 μm, where common natural mineral particles were rarely detected. The contribution of the Ca particles to the volume of total mineral particles greatly exceeded that of other mineral particles during non-dust-storm periods and was comparable to that during dust-storm periods. Reagent film tests showed that particulate sulfate and nitrate formation on the Ca particles was similar to that on common mineral particles. These results indicate that a large portion of Ca in the atmospheric particulate matter in Beijing was from anthropogenic sources rather than from natural sources, and the anthropogenic Ca particles acted as a significant medium for the formation of sulfate and nitrate. Similar particles were also detected at Qingdao, a coastal city in northern China. Data of a dust storm event showed that Ca-abundant particles from East China arrived there and moved out of the continent, similarly to Asian dust storm particles, suggesting possible contributions of anthropogenic Ca even in Asian dust storm samples in the downstream areas. Therefore, Ca may not be a good indicator of Asian dust from natural sources. However, the Ca particles, due to their unique shapes and elemental compositions, may provide an indicator for the atmospheric dispersion of anthropogenic particulate matters in East Asia.     

Establishment of Proper Land-use Assessment and Management Strategy for Deji Reservoir Catchment, Taiwan

Deji Reservoir is situated in the middle of Taiwan on the upstream catchment of the Dajia stream with an area of over 60,160 ha. The embankment stands 180 m high and is the tallest concrete arch dam in Taiwan. This dam stores 1.7 billion cubic meters of valid volume water. It provides over 370 million kilowatt-hours of electricity annually. It is also an important facility for operating flood control, hydroelectricity, irrigation, public water supply, etc. Seventy-two percent of the terrain is at 2,000- to 3,000-m altitude, and 5.2% is above 3,200-m altitude. More than 59% of the area is covered with steep topography of 55% slope. Only 7.9% of the area is shown with gentle slopes of less than 30% slope, which are located among the two banks of main streams with the altitudes ranging from 1,500 to 2,500 m. Most of the gentle slopes are used for temperate zone fruit, vegetable, and tea plantations. This land-use immediately adjoins a reservoir catchment region, resulting in an enormous impact on the mountainous environment. This study reviewed human-developed land-use area to properly address and evaluate norms for mitigating the impacts on the reservoir. The initial investigation brought up the parameters of gradient, slope movement types and processes, distance to the reservoir, location of developed area and distance with the farm road, etc. Local investigation and global information system technology were conducted in this research. We focused on segregating the terrain types of indisposed land-use. A different land-use management strategy is also analyzed.     

Thermodynamic and experimental studies on condensation behavior of low-boiling-point elements volatilized in the melting process

To study the volatilization and condensation behaviors of low-boiling-point elements in the waste melting process, experiments were conducted to collect the dust from a coke-type incineration residue melting furnace. Then, a comparison was made between the experimental results and the calculated values obtained from a thermodynamic equilibrium model in terms of the chemical composition of the dust. The composition of the dust collected from a cylindrical filter in the exhaust gas duct was determined by chemical methods, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and X-ray analysis. As a result, the sampled dust was classified into two different types: fine particles mainly containing Na, K, Pb, and Zn collected from the side face of the cylindrical filter, and large particles containing Ca, Si, and Al collected from the bottom face of the cylindrical filter. From X-ray analysis of the sampled dust, NaCl, KCl, PbS, and ZnS were identified in the fine-particle dust, while CaO, SiO₂, Al₂O₃ were detected in the large-particle dust. From the results of the thermodynamic equilibrium calculation in the gas cooling process from 2000 to 600 K, it was found that Na, K, Pb, and Zn volatilized as metals in the melting furnace were condensed as alkali chlorides such as NaCl and KCl and heavy metal sulfides such as PbS and ZnS. These computational results were in good agreement with the X-ray diffraction results of the sampled dust at a gas temperature of 823 K for the formation of NaCl, KCl, PbS, and ZnS.     

Heterogeneous Sulfate Formation on Dust Surface and Its Dependence on Mineralogy: Balloon-Borne Observations from Balloon-Borne Measurements in The Surface Atmosphere of Beijing, China

This study focuses on providing a direct insight into the process by which sulfate is formed on mineral dust surface in the actual atmosphere. Six sets of aerosol measurements were conducted in the outskirts of Beijing, China, in 2002–2003 using a tethered balloon. The mineralogy of individual dust particles, as well as its influence on the S (sulfur) loadings was investigated by SEM-EDX analysis of the directly collected particles. The mixed layer in the urban atmosphere was found to be quite low (500–600m), often appearing as a particle dense stagnant layer above the surface. It is suggested that mineral dust is a common and important fraction of the coarse particles in Beijing (35–68%), and that it is relatively enriched with Calcite (>28%). An exceptional amount of S was detected in the mineral particles, which can be explained neither by their original composition, nor by coagulation processes between the submicron sulfates and the dust. Heterogeneous uptake of gaseous SO₂, and its subsequent oxidation on dust was suggested as the main pathway that has actually taken place in the ambient environment. The mineral class found with the largest number of particles containing S was Calcite, followed by Dolomite, Clay, Amphibole etc., Feldspar, and Quartz. Among them, Calcite and Dolomite showed distinctly higher efficiency in collecting sulfate than the other types. A positive correlation was found with the number of S containing particles and the relative humidity. Calcite in particular, since almost all of its particles was found to contain S above 60% r.h. On the other hand, the active uptake of SO₂ by the carbonates was not suggested in the free troposphere downwind, and all the mineral classes exhibited similar S content. Relative humidity in the free troposphere was suggested as the key factor controlling the SO₂ uptake among the mineral types. In terms of sulfate loadings, the relationship was not linear, but rather increased exponentially as a function of relative humidity. The humidity-dependent uptake capacity of mineral types altogether showed an intermediate value of 0.07 gSO₄ ²⁻ g⁻¹ mineral at 30% r.h. and 0.40 gSO₄ ²⁻ g⁻¹ mineral at 80%, which is fairly consistent with laboratory experiments.     

Nature of Atmospheric Aerosols over the Desert Areas in the Asian Continent: Chemical State and Number Concentration of Particles Measured at Dunhuang,China

Measurements of aerosol were made in August and October 2001, and January 2002, at Dunhuang, China (40°00N, 94°30E), to understand the nature of atmosphericparticles over the desert areas in the Asian continent. Balloon-borne measurements with an optical particle counter suggested that particle size and concentration had a noticeable peak in size range of super micron in not only the boundary mixing layer but also the free troposphere. Thickness of the boundary mixing layer, from distributions of particle concentration, was about 4 km in summer (17 August 2001), about2.5 km in fall (17 October 2001), and about 3 km in winter (11 January 2002), which suggest active mixing of particles near the boundary in summer. Number-size distribution of particleshowed a noticeable peak in the super micron particles size range inthe mixing boundary layer: 0.4–2 particles cm^-3 at diameter>1.2 m in summer, 0.05–4 particles cm^-3 at diameter >1.2 m in fall, and 0.1–5 particles cm^-3 at diameter>1.2 m in winter. In winter strong inversion of atmospherictemperature was found in the height range from the boundary to about 3 km and vertical distribution of particle concentration well corresponded with the temperature distribution. Chemical elements of individual aerosols, which were collectedin the boundary layer atmosphere at Dunhuang (18 October 2001) were analyzed with an electron microscope equipped with EDX. Thosesingle particle analysis suggested that most of the particles with supermicron size were soil particles, and those particles had littlesulfate on its surface. This is a very important different point,comparing with the chemical state of soil particles, which weretransported from the desert area of China to Japan, and showed frequentlythe existence of sulfate on the particle surface. Therefore, it isstrongly suggested that dust particles can be chemically modifiedduring their long-range transport from desert areas to Japan.     

The use of the removable thin film coating technique as an alternative to traditional decontamination methods to mitigate and abate hazardous particulates

This article summarizes a study that evaluated a new decontamination technique for the mitigation and abatement of hazardous dust and particulates. Traditional decontamination methods are time‐consuming, expensive, can create airborne hazards, and do not always bring the concentration of the contaminant to acceptable levels. The use of the removable thin film coating will increase efficiency, will not generate airborne hazards, will decrease costs, and, with one application, will bring the hazardous dust concentrations to acceptable levels. Qualitative tests demonstrated that the removable thin film coating reduced the amount of visible luminescent dust (a surrogate for hazardous dust) from various surfaces. It also indicated that wherever there were minute scratches, the coating did not remove all of the dust. However, the qualitative tests showed that this decontamination method worked well as a preventative method, protecting clean areas from becoming contaminated when exposed to the luminescent dust. Further investigation was conducted using a scanning electron microscope (SEM) and carbon dust. Overall, the SEM experiment demonstrated that there was a statistically significant (p = 0.00007) removal of carbon dust (less than 10 μm in size) from surfaces with crevasses larger than 3 μm. The SEM also revealed that there were some limitations where there were large clusters of carbon dust; in these instances, the coating would tear and remain on the sample surface. One method to resolve this limitation involved adding Kevlar^TM fibers to the removable thin film coating. It was thought that this would increase the strength of the coating and eliminate the coating from tearing when removing large clusters of a contaminant. Unfortunately, this did not alleviate the issue. The use of an engineered textile, saturated with the coating, appeared to eliminate the problem with the coating not being able to remove the contaminant from the minute surface scratches and improved the removal process of the coating. © 2008 Wiley Periodicals, Inc.     

The Influence of Synoptic-scale Air Flow and Local Circulation on the Dust Layer Height in the North of the Taklimakan Desert

The present study investigates the influences of synoptic-scale air flows and local wind circulations on the dust layer height (DLH) in the Taklimakan Desert, based on lidar observations performed in the north of the desert in March 2003. The DLH fluctuates approximately every three days between 2500 m (above sea level) and 5000 m, including diurnal variations. Meteorological analyses and numerical simulations show that the three-day fluctuation of DLH corresponds with variations in synoptic-scale air flows over the Taklimakan Desert, and the diurnal variations are linked to downdrafts and updrafts that are formed over the north of the desert as part of local circulations. When strong northerly winds prevail in the upper troposphere and a developed valley wind blows toward the Tienshan Mountains in the lower troposphere, the downdrafts strengthen in the middle troposphere over the north of the desert, lowering the DLH to about 2500 m. In contrast, the DLH rises to about 5000 m when the updrafts develop between strong southerly winds in the upper troposphere and a developed mountain wind blowing from the Tienshan Mountains. Simulations for the local circulation behavior without the presence of the Tienshan Mountains demonstrate that the valley and mountain winds on the southern slope of the Tienshan Mountains control the intensity of the downdrafts and updrafts, thereby influencing the DLH over the north of the Taklimakan Desert.     

Toxicity and source assignment of polycyclic aromatic hydrocarbons in road dust from urban residential and industrial areas in a typical industrial city in Korea

This study analyzed the toxicity and sources of polycyclic aromatic hydrocarbons (PAHs) in road dust from six representative areas (three urban residential areas and three industrial areas) from a typical industrial city in Korea. The concentrations and the toxicity equivalent concentrations (TEQs) in road dust varied by area, depending on the type of traffic and industrial activities and the PAHs identified. High correlations between the total concentration and the TEQ of PAHs in road dust were found in road dust from both the urban and industrial areas. To identify the sources of PAHs, this study utilized a factor loading method in a principal component analysis, the ratio of PAHs from combustion sources to total PAHs (ΣCOMB to ΣPAH), and bivariate plots of phenanthrene/anthracene (PA/Ant) versus fluoranthene/pyrene (FL/Pyr), and ΣCOMB/ΣPAH versus FL/Pyr in road dust. The identified origin of the PAHs was fuel combustion, including gasoline, diesel, oil, and coal, used in urban and industrial areas.     

Features in Number Concentration-Size Distributions of Aerosols in the Free Atmosphere over the Desert Areas in the Asian Continent: Balloon-Borne Measurements at Dunhuang,China

Vertical changes of aerosol concentration and size in the freetroposphere over the Asian desert areas were firstly observed using a balloon-borne optical particle counter at DunHuang, China (40°00N, 94°30E) (17 August and 17 October 2001, and 11 January 2002). In the free troposphere highly concentrated aerosol layers were frequentlyobserved, suggesting the importance of regional scale particletransportation over the Asian continent. Concentration ofparticles with a diameter larger than 0.15 m was about 5–10particles cm^-3 in the free troposphere.Particle number-size distribution in the free troposphereshows important contribution of super micron particles. Regionalscale transportation, in addition to diffusion of soil particlesfrom the lower atmosphere to the free troposphere through localand small scale air motions, is suggested by backward trajectoryanalysis of air masses containing super micron particles. The importance of horizontal transport of coarse size particles in the free troposphere was strongly suggested.Thickness of the boundary mixing layer, from distributions ofparticle concentration, was about 4 km in summer (17 August 2001)and apparently higher than the height of layers in fall (17 October2001) and in winter (11 January 2002), which suggest an active mixingof particles near the boundary in summer. In winter measurement(11 January 2002), strong inversion was found in the vertical profile of temperature, suggesting cold ground surface and vertically stable atmosphere near the ground.     

Aerosol Composition Change due to Dust Storm: Measurements between 1992 and 1999 at Gosan,Korea

Aerosol composition change between dust storm and non duststorm periods is studied using the TSP (Total SuspendedParticulate) data measured at Gosan, Korea between 1992 and1999. The concentrations of elements measured between 1993and 1996 and those of ions between 1992 and 1999 duringdust storms are compared with those during non-dust stormperiods in spring (March, April, and May). Among theanalyzed ions, the concentrations of crustal species(potassium, calcium, magnesium, and chloride) andanthropogenic species (nitrate and non-sea salt (nss)-sulfate) increased when dust storm occurs while those ofammonium and sodium did not increase. Among the analyzedelements, the concentrations of crustal species (Fe, Al,Ca, Ti, and Zn) increased when dust storm occurs whilethose of anthropogenic species (Mn, V, Ni, Cu, Cd, and Cr)did not increase. The only anthropogenic element of whichconcentration increased during dust storm periods was Pb.It was found that the concentrations of nitrate and nss-sulfatewere highest during spring. Also, the ratio of theyearly average concentrations of nitrate to nss-sulfateincreases, probably due to the emission trend change innortheast Asia, especially, in China.     

What Anthropogenic Radionuclides (90Sr and 137Cs in Atmospheric Deposition, Surface Soils and Aeolian Dusts Suggest for Dust Transport over Japan

Currently, atmospheric anthropogenic radionuclides (particulate) are controlled by suspension of the surface dust containing those radionuclides (resuspension). We have found, therefore, that such radionuclides can be used as tracers of the surface dust suspension, transport and its subsequent deposition in distant areas. The ¹³⁷Cs/⁹⁰Sr activity ratios in the atmospheric deposition, without the direct influence of nuclear tests and accidents, at the Meteorological Research Institute (MRI, Tsukuba, Japan) during the 1990s were fairly low (average: 2.1). This value is not in agreement with the ratios in Japanese surface soils (range of averages: 4–7), which had been considered as the primary source of the deposited dust. This suggests that the current atmospheric dust deposition in Japan is a mixture of local and remote components. The remote component could be an aeolian dust that has been transported long distances from arid areas. The major component is most likely to be Asian dust. It was further hypothesized that other remote source may exist beyond the Asian domain, based on accumulated observations and model results. To obtain more information about the dust transport, Sahara dust deposited in Monaco in 2002 and a suspended dust collected in the Taklamakan area in 2001 were analyzed for ⁹⁰Sr and ¹³⁷Cs. The Taklamakan dust exhibited a ¹³⁷Cs/⁹⁰Sr ratio of about 4, which is within the range of atmospheric deposition observed at the MRI, while the Sahara dust exhibited a higher ¹³⁷Cs/⁹⁰Sr ratio (about 13). Although the present Sahara datum was negative for our hypothesis of ‘hyper-range transport’, the seasonal change of the ¹³⁷Cs/⁹⁰Sr ratio in the atmospheric deposition observed at the MRI requires an aeolian dust source having a low ¹³⁷Cs/⁹⁰Sr ratio, other than Asian dust.     

新型旋流除尘器在100万吨/年乙烯装置尾气除尘中的应用

为了去除石化行业乙烯装置裂解炉烧焦尾气中的颗粒污染物,对传统用于气体除尘的旋风分离器进行改进,设计了一种新型旋流除尘器,并将其应用于乙烯装置裂解炉清焦过程中。经新型旋流除尘器处理后,出口气中焦粉颗粒质量浓度基本控制在15 mg/m³以下,符合GB 31570—2016《石油炼制工业污染物排放标准》的排放要求（≤20 mg/m³）,平均分离效率达到92.8%,粒径在10 μm以上的焦粉颗粒得到大幅度去除。     

Climatic and Environmental Changes in the Source Areas of Dust Storms in Xinjiang, China, during the Last 50 Years

The desert environmental changes in the source areas of dust storms occurring in Xinjiang are discussed based on the climate changes and the impacts of human activities in Xinjiang during the past 50 years. The results show that the climate in Xinjiang is changing from a warm-dry type to a warm-wet one. The warm-wet climate has been obvious since the mid-1970's, and especially the sensitivity of the regional climate change in this arid area is obviously revealed by many factors, such as the characteristics of the local climate change in south Xinjiang and north Xinjiang, the difference of climate change in the alpine zones and the basins, and the change of areas of the waters bodies. Furthermore, these factors also reveal the difference in the regional climate change between Xinjiang and central and eastern areas of China. The occurrence and development of dust storms are directly affected by the precipitation, air humidity, status of underlying surface, etc. in the arid areas. The frequency and intensity of dust storms are closely related to the natural conditions, changes of climate and desert environment, as well as the dynamic conditions (i.e., weather systems) in the source areas of dust storms. Therefore, global warming is one of the main causes resulting in the degradation of the ecological environment and the frequent occurrence of natural disasters, especially the disasters of sand drift and dust storms in the arid areas since the late-1980's, which reveals that the inland arid areas are sensitive regions to climate changes.     

电除尘器及其电离荷电机制的研究新进展

详细介绍了电除尘技术研究现状、现存问题及其研究趋势.目前电除尘技术的理论尚不完备,属于经验工程的学科,电除尘器的技术性能优劣取决于设计命中率.为此,论述烟尘荷电凝聚机制并研究电离放电通道中的带电粒子复合问题及其输运特性等,以便解决除尘电场中的电离占空比、输运项甚低等问题;研究了烟尘荷电、凝聚的物理过程,以便进一步提高电除尘器的性能.     

The effect of dust emissions from open storage piles to particle ambient concentration and human exposure

The current study focus on the determination of dust emissions from piles in open storage yards of a municipal solid waste (MSW) composting site and the subsequent atmospheric dust dispersion. The ISC3-ST (Industrial Source Complex Version 3 – Short Term) model was used for the evaluation of the PM₁₀ ambient concentrations associated with the dispersion of MSW compost dust emissions in air. Dust emission rates were calculated using the United States Environmental Protection Agency proposed dust resuspension formulation from open storage piles using local meteorological data. The dispersion modelling results on the spatial distribution of PM₁₀ source depletion showed that the maximum concentrations were observed at a distance 25–75 m downwind of the piles in the prevailing wind direction. Sensitivity calculations were performed also to reveal the effect of the compost pile height, the friction velocity and the receptor height on the ambient PM₁₀ concentration. It was observed that PM₁₀ concentrations (downwind in the prevailing wind direction) increased with increasing the friction velocity, increasing the pile height (for distances greater than 125 m from the source) and decreasing the receptor height (for distances greater than 125 m from the source). Furthermore, the results of ISC3-ST were analysed with the ExDoM (Exposure Dose Model) human exposure model. The ExDoM is a model for calculating the human exposure and the deposition dose, clearance, and finally retention of aerosol particles in the human respiratory tract (RT). PM₁₀ concentration at the composting site was calculated as the sum of the concentration from compost pile dust resuspension and the background concentration. It was found that the exposure to PM₁₀ and deposited lung dose for an adult Caucasian male who is not working at the composting site is less by 20–74% and 29–84%, respectively, compared to those for a worker exposed to PM concentrations at the composting site.     

Atmospheric Loadings,Concentrations and Visibility Associated with Sandstorms: Satellite and Meteorological Analysis

This Korea-China study monitored the phenomena of sandstorms and significant dustfall (SD) from 1997 to 2000. The analysis of our data included ground measurements of dust concentration, visibility, satellite imagery, aircraft and lidar observations. In addition, an estimation of atmospheric loadings and a studyon the relationship between dust concentrations and visibilitywere carried out. The movement and invasion of dust clouds toKorea were clearly identified with meteorological and satellitedata. The increasing concentrations of TSP and PM₁₀ concurredwell with the satellite information. From case studies, weestimated that atmospheric loadings of a dust cloud were over 1million ton and that the deposition over the Korean Peninsulawas in the range from 46 000 to 86 000 tons. For SD withvisibility of 3 km, we predict TSP 659 g m^-3 and PM₁₀ 493 g m^-3. We recommend the issuance of an SD Watch(advisory) and an SD Warning for the general public.     

Occupational hygiene in a Finnish drum composting plant

Bioaerosols (microbes, dust and endotoxins) and volatile organic compounds (VOCs) were determined in the working air of a drum composting plant treating source-separated catering waste. Different composting activities at the Oulu drum composting plant take place in their own units separated by modular design and constructions. Important implication of this is that the control room is a relatively clean working environment and the risk of exposure to harmful factors is low. However, the number of viable airborne microbes was high both in the biowaste receiving hall and in the drum composting hall. The concentration (geometric average) of total microbes was 21.8 million pcs/m3 in the biowaste receiving hall, 13.9 million pcs/m3 in the drum composting hall, and just 1.4 million pcs/m3 in the control room. Endotoxin concentrations were high in the biowaste receiving hall and in the drum composting hall. The average (arithmetic) endotoxin concentration was over the threshold value of 200 EU/m3 in both measurement locations. In all working areas, the average (arithmetic) dust concentrations were in a low range of 0.6-0.7 mg/m3, being below the Finnish threshold value of 5 mg/m3. In the receiving hall and drum composting hall, the concentrations of airborne microbes and endotoxins may rise to levels hazardous to health during prolonged exposure. It is advisable to use a respirator mask (class P3) in these areas. Detected volatile organic compounds were typical compounds of composting plants: carboxylic acids and their esters, alcohols, ketones, aldehydes, and terpenes. Concentrations of VOCs were much lower than the Finnish threshold limit values (Finnish TLVs), many of the quantified compounds exceeded their threshold odour concentrations (TOCs). Primary health effects due VOCs were not presumable at these concentrations but unpleasant odours may cause secondary symptoms such as nausea and hypersensitivity reactions. This situation is typical of composting plants where the workers are exposed to dozens of VOCs simultaneously. The odour units (OU/m3) were measured using olfactometer. The numbers were 23,000 OU/m3 at the output end of the composting drum and 6300 OU/m3 in the exhaust pipe. Inside the composting hall, the number of odour units was 500 and 560 OU/m3.     

Combining stakeholder analysis and spatial multicriteria evaluation to select and rank inert landfill sites

This paper presents a method based on the combination of stakeholder analysis and spatial multicriteria evaluation (SMCE) to first design possible sites for an inert landfill, and then rank them according to their suitability. The method was tested for the siting of an inert landfill in the Sarca’s Plain, located in south-western Trentino, an alpine region in northern Italy. Firstly, stakeholder analysis was conducted to identify a set of criteria to be satisfied by new inert landfill sites. SMCE techniques were then applied to combine the criteria, and obtain a suitability map of the study region. Subsequently, the most suitable sites were extracted by taking into account also thresholds based on size and shape. These sites were then compared and ranked according to their visibility, accessibility and dust pollution. All these criteria were assessed through GIS modelling. Sensitivity analyses were performed on the results to assess the stability of the ranking with respect to variations in the input (criterion scores and weights). The study concluded that the three top-ranking sites are located close to each other, in the northernmost sector of the study area. A more general finding was that the use of different criteria in the different stages of the analysis allowed to better differentiate the suitability of the potential landfill sites.     

Characterization of Dust Storms to Hong Kong in April 1998

In April 1998, two intense dust storms were generated in CentralAsia and transported eastward across East Asia (15 and 19 April). This article presents the chemical characterization ofHong Kong (HK) aerosols during the dust storms. During the 15 Aprildust storm, hourly respiratory suspended particles (RSP)(particle diameter smaller than 10 m) concentrationsmonitored at 7 sites in Hong Kong reached the peak valuessynchronously between 9 and 11 a.m. on 17 April, in which thehighest concentration was 267 g m^-3. Analysis ofthe RSP samples showed that concentrations of crustalelements (Ba, Ca, Cd, Cr, Fe, Mg, K⁺) and anthropogenicspecies (As, Ni, Pb, Zn, NH₄ ⁺, NO₃ ^-,SO₄ ^2- and total carbon) were substantiallyenhanced. Enhancement of these species was more than afactor of 2 to 14 relative to the non dust period. The totalcarbon content was high, at 59 g m^-3 (notincluding carbonate), and the enrichment factors of Asand Pb on 17 April were 122 and 117, respectively. Thisimplied that anthropogenic materials together with mineraldust were transported to HK from Mainland China. Based onmaterial balance calculations, mineral dust contributed41% to the observed RSP mass on 17 April, which was 2 times thatof the nondust sample (22%). From the 5-day backwardtrajectory analysis, this storm was transported directlyfrom Northwest China to HK. However, there was nocorresponding observation for the 19 April dust stormaerosol. Consequently, 15 April storm had stronger impact onHK's atmosphere than 19 April storm. Compared to the HK AirQuality Objective, 15 April dust storm did not cause seriousair pollution in HK.