Check out our New Publishers' Select for Free Articles

Atmospheric Environment (v.42, #26)

Editorial board (pp. i).

Measurement of non-enteric emission fluxes of volatile fatty acids from a California dairy by solid phase micro-extraction with gas chromatography/mass spectrometry by Phillip Alanis; Mark Sorenson; Matt Beene; Charles Krauter; Brian Shamp; Alam S. Hasson (pp. 6417-6424).

Dairies are a major source of volatile organic compounds (VOCs) in California's San Joaquin Valley; a region that experiences high ozone levels during summer. Short-chain carboxylic acids, or volatile fatty acids (VFAs), are believed to make up a large fraction of VOC emissions from these facilities, although there are few studies to substantiate this. In this work, a method using a flux chamber coupled to solid phase micro-extraction (SPME) fibers followed by analysis using gas chromatography/mass spectrometry was developed to quantify emissions of six VFAs (acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid and 3-methyl butanoic acid) from non-enteric sources. The technique was then used to quantify VFA fluxes from a small dairy located on the campus of California State University Fresno. Both animal feed and animal waste are found to be major sources of VFAs, with acetic acid contributing 70–90% of emissions from the sources tested. Measured total acid fluxes during spring (with an average temperature of 20°C) were 1.84±0.01, 1.06±0.08, (1.3±0.5)×10⁻², (1.7±0.2)×10⁻² and (1.2±0.5)×10⁻²gm⁻²h⁻¹ from silage, total mixed rations, flushing lane, open lot and lagoon sources, respectively. VFA emissions from the sources tested total 390±80gh⁻¹. The data indicate high fluxes of VFAs from dairy facilities, but differences in the design and operation of dairies in the San Joaquin Valley as well as seasonal variations mean that additional measurements must be made to accurately determine emissions inventories for the region.

Keywords: Carboxylic acids; Cattle; Emissions; Ozone precursors

A note on the 2008 EU standards for particulate matter by Bert Brunekreef; Robert L. Maynard (pp. 6425-6430).

In the spring of 2008, the EU decided on the future PM regulations. In this note we first compare existing regulations for PM10 with updated regulations for PM10; then we discuss the decisions on PM2.5; and finally we compare the new EU regulations with US EPA standards for PM2.5.The conclusions are that PM10 regulations have been somewhat relaxed despite the fact that the numerical values of the Limit Values have not changed; that the annual PM2.5 Limit Value is at the upper end of exposure response curves from major epidemiological studies, and hence not protective of public health as major adverse effects on health have been observed at levels well below the adopted PM2.5 limit value; that the newly introduced instrument of the ‘exposure concentration obligation’ is unlikely to improve this; that the US EPA National Ambient Air Quality Standards for PM2.5 are lower than the EU limit values; and that, contrary to what is often suggested, the EU requirements for assessing compliance with the Limit Value for PM2.5 are not more stringent than the US EPA requirements for assessing compliance with the annual and 24h PM2.5 National Ambient Air Quality Standards.

Keywords: Particulate matter; PM10; PM2.5; Legislation; Limit values; Standards

A HRTEM/EDX approach to identification of the source of dust particles on urban tree leaves by S.G. Lu; Y.W. Zheng; S.Q. Bai (pp. 6431-6441).

Dust on tree leaves in the urban area of Hangzhou, China, was analyzed in terms of heavy metal contents and magnetic properties. Morphological and chemical composition of the dust particles were analyzed using a high resolution transmission electron microscope equipped with an energy-dispersive X-ray analyzer (HRTEM/EDX). Results indicated that the dusts contained high concentrations of Cd (mean 2.62), Cu (63.7), Zn (535.9) and Pb (150.9mgkg⁻¹). Magnetic susceptibility of the dusts was in a range of (16–856)×10⁻⁸m³kg⁻¹. It was shown that the dusts close to industrial area and busy road intersection had higher heavy metal contents and magnetic susceptibility. The dusts showed a strong positive inter-correlation for the concentrations of Fe, Mn, Cr, Zn, Pb, and Cu in addition to magnetic susceptibility, which suggests that the dusts had a common source for the heavy metals and magnetic carriers. We found that the dust particles were composed mainly of Fe-rich near-spherical, plate and agglomerate particles, and Ca-rich, S-rich and silicate particles, and that iron oxide spherules (0.2–0.5μm in diameter) and larger iron-bearing particles were the magnetic carriers. Ca in the dusts was present in the forms of CaCO₃ and CaCO₃/CaSO₄ internal mixture. The Fe-rich, Ca-rich and S-rich particles in dusts could be directly related to nearby polluting activities, such as coal combustion, traffic emission and industrial activity. The identification of the main sources of dusts on tree leaves can help in controlling the polluting sources in urban areas. The close correlation between magnetic susceptibility and heavy metal concentration makes it possible to use the magnetic technique as a non-destructive and time-efficient tool for biomonitoring of the atmospheric dust pollutants.

Keywords: Dust particles; Tree leaves; Heavy metal; Transmission electron microscopy; Magnetic susceptibility

Near source deposition of vehicle generated fugitive dust on vegetation and buildings: Model development and theory by E.R. Pardyjak; S.O. Speckart; F. Yin; J.M. Veranth (pp. 6442-6452).

This paper describes the development of a simple quasi-2D Eulerian atmospheric dispersion model that accounts for dry deposition of fugitive dust onto vegetation and buildings. The focus of this work is on the effects of atmospheric surface layer parameterizations on deposition in the “impact zone” near unpaved roads where horizontal advection of a dust cloud through roughness is important. A wind model for computing average and turbulent wind fields is presented for flow within and above a roughness canopy. The canopy model has been developed to capture the most essential transport and deposition physics while minimizing the number of difficult-to-obtain input parameters. The deposition model is based on a bulk sink term in the transport equation that lumps the various dry deposition physical process. Wind field, turbulence and deposition results are presented for a range of atmospheric stabilities and roughnesses. The canopy model produces results in which deposition within a canopy is enhanced under certain initial, atmospheric and roughness conditions, while under other conditions much less deposition occurs. The primary limitation of the model is the ability to accurately determine (typically using experimental data) the vegetative deposition parameter (clearance frequency). To understand the clearance frequency better, a dimensionless parameter called the deposition effectiveness is identified that can be used to estimate deposition in the canopy. In general, the model captures the essential physics of near source dust transport and provides a tool that can efficiently simulate site-specific conditions in practical situations.

Keywords: Fugitive dust; Near source deposition; Roughness; Vegetation; Vehicle generated dust

Characteristics of cabin air quality in school buses in Central Texas by Donghyun Rim; Jeffrey Siegel; Jarett Spinhirne; Alba Webb; Elena McDonald-Buller (pp. 6453-6464).

This study assessed in-cabin concentrations of diesel-associated air pollutants in six school buses with diesel engines during a typical route in suburban Austin, Texas. Air exchange rates measured by SF₆ decay were 2.60–4.55h⁻¹. In-cabin concentrations of all pollutants measured exhibited substantial variability across the range of tests even between buses of similar age, mileage, and engine type. In-cabin NO _x concentrations ranged from 44.7 to 148ppb and were 1.3–10 times higher than roadway NO _x concentrations. Mean in-cabin PM_2.5 concentrations were 7–20μgm⁻³ and were generally lower than roadway levels. In-cabin concentrations exhibited higher variability during cruising mode than frequent stops. Mean in-cabin ultrafine PM number concentrations were 6100–32,000 particlescm⁻³ and were generally lower than roadway levels. Comparison of median concentrations indicated that in-cabin ultrafine PM number concentrations were higher than or approximately the same as the roadway concentrations, which implied that, by excluding the bias caused by local traffic, ultrafine PM levels were higher in the bus cabin than outside of the bus. Cabin pollutant concentrations on three buses were measured prior to and following the phased installation of a Donaldson Spiracle Crankcase Filtration System and a Diesel Oxidation Catalyst. Following installation of the Spiracle, the Diesel Oxidation Catalyst provided negligible or small additional reductions of in-cabin pollutant levels. In-cabin concentration decreases with the Spiracle alone ranged from 24 to 37% for NO _x and 26 to 62% and 6.6 to 43% for PM_2.5 and ultrafine PM, respectively. Comparison of the ranges of PM_2.5 and ultrafine PM variations between repetitive tests suggested that retrofit installation could not always be conclusively linked to the decrease of pollutant levels in the bus cabin.

Keywords: Diesel; Mobile sources; Indoor air

An evaluation of Terra-MODIS sampling for monthly and annual particulate matter air quality assessment over the Southeastern United States by Pawan Gupta; Sundar A. Christopher (pp. 6465-6471).

Although satellites provide reliable and repeated measurements on a global basis, particulate matter air quality information can be derived from satellites only when clouds are absent and when surface conditions are favorable. However, ground measurements provide particulate matter information irrespective of cloud cover and surface conditions. Therefore there could be a sampling bias when using satellite data for air quality research. To examine this issue, we calculate particulate matter (PM2.5) mass concentration from daily ground-based measurements (ALLPM) on monthly to yearly time scales and compare these against the same ground measurements for only those days when satellite data is available (SATPM). To accomplish this, we use six years of PM2.5 mass concentration data from 38 stations along with Terra-MODIS satellite data over the Southeastern United States. Our results indicate that satellite data are generally available less than 50% of the time over these locations, although the interregional variability of data availability is between 32% and 57%. However, the mean differences between the ALLPM and SATPM, over monthly to yearly time scales over the Southeastern United States, is less than 2μgm⁻³ indicating that low sampling from satellites due to cloud cover and other reasons is not a major problem for studies that require long term PM2.5 data sets. These results have important implications for satellite studies especially over areas where ground-based measurements are not available.

Keywords: Air quality; Satellite remote sensing; Particulate matter

Impact of the open biomass fires in spring and summer of 2006 on the chemical composition of background air in south-eastern Finland by Pia Anttila; Ulla Makkonen; Heidi Hellén; Katriina Kyllönen; Sirkka Leppänen; Helena Saari; Hannele Hakola (pp. 6472-6486).

In the spring and summer of 2006 the air quality in southern Finland was affected by two major biomass fire smoke episodes. At the Virolahti background station, closest to the eastern fire areas, the episodes lasted altogether several weeks. The high point in spring was 25 April and in summer 13 August. In spring the aerosol detected at Virolahti originated at distances of even hundreds of kilometres to the south and south-east, and consequently was a mixture of material from biomass burning and from other sources (both LRT and local), all of which contributed to the detected elevation of PM₁₀ concentrations. The elevated concentrations of trace elements (Cd, Pb, Zn) during the most intense biomass fire episode were associated with other anthropogenic emissions.In contrast, during August 2006, the PM₁₀ at Virolahti was quite exclusively impacted by close (ca. 50–100km) biomass fire sources. The presumably organic component comprised, at its highest, as much as 90% of the total PM₁₀. In addition to record high PM₁₀ and PM_2.5 concentrations, the concentrations of polycyclic aromatic hydrocarbons were considerably elevated, even reaching values more typical of wintertime urban environments. During the peaks of the episodes in August, the total gaseous mercury concentration in the air was more than double its background value. In general, the trace elements did not exceed their background values.

Keywords: Open biomass fires; PM; ₁₀; Total gaseous mercury; Polycyclic aromatic hydrocarbons; Trace elements

Arsenic speciation study of PM_2.5 in an urban area near a copper smelter by A.M. Sánchez de la Campa; J.D. de la Rosa; D. Sánchez-Rodas; V. Oliveira; A. Alastuey; X. Querol; J.L. Gómez Ariza (pp. 6487-6495).

An arsenic speciation study has been performed in selected PM_2.5 samples collected at an urban background monitoring station of the city of Huelva during 2001 and 2002, which registers the emission derived from a nearby copper smelter. The mean total As concentration of the PM_2.5 samples analyzed during 2001 (6.4ngm⁻³) and 2002 (7.9ngm⁻³) slightly exceed the mean annual 6ngm⁻³ target value proposed for PM₁₀ by the European Commission for 2013.The speciation analysis shows that arsenate [As(V)] is the main arsenic species found, followed by arsenite [As(III)] (mean 5.8 and 1.2ngm⁻³ for As(V) and As(III), in PM_2.5, respectively, during 2001–2002).Three atmospheric and emission scenarios have been distinguished from a cluster analysis using trace elements (Pb, Zn, Cu and Se) and As species derived from the copper smelter: (a) Anthropogenic, (b) Anthropogenic plus African dust outbreak and (c) Atlantic advection. Highest As_total mean concentration was found during the anthropogenic episodes (23.3ngm⁻³), followed by the anthropogenic plus African dust outbreak episodes (9.2ngm⁻³) and Atlantic advection days (2.2ngm⁻³). These scenarios have been identified in a previous work on the As species analysis in PM₁₀.During Atlantic advection days, the As(III)/As(V) ratio in PM_2.5 and PM₁₀ was high, whereas low As(III)/As(V) ratio in both PM_2.5 and PM₁₀ samples has been displayed during the anthropogenic scenarios. The As(III)/As(V) may be considered as a fingerprint of the origin of the particulate matter.

Keywords: Atmospheric particles; PM; _2.5; Arsenic speciation; Copper smelter; SW Spain

Relative exposure to fine particulate matter and VOCs between transport microenvironments in Dublin: Personal exposure and uptake by A. McNabola; B.M. Broderick; L.W. Gill (pp. 6496-6512).

To compare the relative exposure to and uptake of air pollutants between modes of commuter transport, measurements of personal exposure to PM_2.5 and traffic-related VOCs were obtained over an 18-month period. In total, 468 samples were recorded comprising journeys equally divided between the four main modes of commuter transport in Dublin, Ireland: the private car, pedestrian, public bus and cyclist. Samples were recorded along two fixed routes approaching/exiting the city centre at fixed times of the day (morning and evening peak traffic flows, 08:00–09:00 and 17:00–18:00). Samples were measured using a high flow gravimetric personal sampler for PM_2.5 and a low flow vacuum operated bag sampler for VOCs. Sampling was always carried out simultaneously between two modes of transport to ensure a direct comparison regardless of meteorological and traffic conditions. Significant differences were found between the personal exposures recorded in the four modes investigated. The car commuter was found to have the highest exposure to VOCs, while the bus commuter was found to have the highest exposure to PM_2.5. The pedestrian was consistently found to have the lowest exposure. Significant differences were also found between the two fixed routes investigated. However, as there were differences in physiological states, exposure durations and exposure levels between the four modes of transport, it was deemed necessary to estimate the total uptake of pollutants by means of a numerical human respiratory tract model. The results showed the cyclist to have the highest deposition of PM_2.5 in the lungs followed by the bus, pedestrian and car. The car passenger had the highest absorption of VOCs followed by the cyclist, pedestrian and bus. Hence, the findings of the human respiratory tract model give a significantly different impression of relative uptake of pollutants to the relative exposure concentrations found initially.

Keywords: PM; _2.5; Benzene; Personal exposure; Commuter transport; Pollutant uptake; Direct comparisons

The open-top chamber impact on vapour pressure deficit and its consequences for stomatal ozone uptake by K. Piikki; L. De Temmerman; P. Högy; H. Pleijel (pp. 6513-6522).

The vapour pressure deficit (VPD) in open-top chambers (OTCs) was analysed in relation to time of day and ambient meteorology. Effects of observed VPD differences (ΔVPD) between OTCs and the ambient air (AA) on stomatal conductance ( g_s) were simulated using 10 model functions from the literature. The dataset originated from 17 OTC crop experiments performed in Belgium, Germany and Sweden. ΔVPD is the resulting difference between the OTC effect on e_s( T), which is the temperature-dependent saturation pressure of water vapour and the OTC effect on e_a, which is the prevailing partial pressure of water vapour in the air (ΔVPD=Δ e_s( T)−Δ e_a). Both Δ e_s( T) and Δ e_a were positive during daylight hours. ΔVPD was small in comparison and sensitive to changes in Δ e_s( T) or Δ e_a. ΔVPD was negative between 07:30 and 10:30 and positive thereafter with a maximum at 20:30 (local time). The positive afternoon ΔVPD was due to an early decrease in Δ e_a, probably caused by ceased transpiration, while the positive Δ e_s( T) persisted throughout the evening, most likely because of restrained cooling in the OTCs. Both the negative morning ΔVPD and the positive evening ΔVPD were more pronounced during clear, warm and dry weather. Circumstances when VPD had a stronger limiting effect on g_s inside the OTCs compared to in the ambient air coincided with high ambient ozone concentrations ([O₃]). Calculated wheat O₃ uptake over an [O₃] threshold of 40nmolmol⁻¹ was reduced by 8.7% in OTCs, assuming that VPD was the only factor limiting g_s and that g_s was the only resistance for O₃ uptake. VPD is one factor of considerable importance for g_s and the OTC impact on VPD may contribute to an underestimation of O₃ effects expressed in relation to the external O₃ exposure.

Keywords: Open-top chamber; Ozone; Ozone index; Ozone uptake; Risk assessment; Vapour pressure deficit

Influence of sea breeze circulation and road traffic emissions on the relationship between particle number, black carbon, PM1, PM2.5 and PM2.5–10 concentrations in a coastal city by Sergio Rodríguez; Emilio Cuevas; Yenny González; Ramón Ramos; Pedro Miguel Romero; Noemí Pérez; Xavier Querol; Andrés Alastuey (pp. 6523-6534).

The physical characterisation of metrics representative of ambient air particle concentration is becoming a topic of great interest for urban air quality monitoring and human exposure assessment. In this article, the influence of sea breeze circulation and primary road traffic emissions on the relationship between the urban aerosol number (N3, particles >3nm), black carbon <10μm (BC), PM1, PM2.5, PM2.5–10 (PM x) concentrations was studied in a coastal city (Santa Cruz de Tenerife, Canary Islands). The daily cycles of sea and mountain breezes (inland during daylight and seaward at night) and road traffic emissions exerted a great, and well differentiated, influence on the BC, N3 and PM x concentrations. In this scenario, the following major aerosol features were observed: (1) fresh vehicle exhaust emissions resulted in high BC and N3 concentrations, in such a way that these two metrics increased when the “road traffic intensity (vehiclesh⁻¹)/wind speed” ratio increased, (2) PM1 and PM2.5 levels were lower during daylight (due to inland entry of relatively clean marine air masses) than at night (due to the seaward drainage airflow resulting in the transport of aged particulate pollutants from the city), (3) although N3 and BC concentrations exhibited a significant correlation during the whole study period, the N3/BC ratio experienced a daily evolution with a maximum during daylight. Thus, high N3 concentrations associated with high N3/BC ratios and high solar irradiance conditions were recorded during the daylight inland breeze period due to an enhancement of processes favouring new particle formation. Data analysis points out that this enhancement in the new particle formation processes is strongly related to the nucleation of photo-oxidized vapours under the relatively low PM x (and consequently low aerosol surface area) concentrations prompted by the inland entry of clean marine air due to the daylight breeze blowing. The results obtained show that, in addition to the vehicle exhaust emissions, new particle formation in coastal urban areas due to photo-oxidation processes may significantly contribute to the ultrafine particle concentration.

Keywords: Ultrafine particles; New particle formation; Black carbon; Soot; Vehicle exhausts

Observation of transformation of calcite to gypsum in mineral aerosols by Ca K-edge X-ray absorption near-edge structure (XANES) by Yoshio Takahashi; Takuro Miyoshi; Sadayo Yabuki; Yasuhiro Inada; Hiroshi Shimizu (pp. 6535-6541).

Calcium K-edge XANES was employed for the speciation of Ca in mineral aerosols collected by an Andersen-type air sampler in Aksu, close to the Taklimakan Desert in China. The sampling was conducted in April 2002 when dust events occurred. Additionally, the sample collected in January 2002 was studied for comparison purposes as well. It was found that the XANES spectra of mineral aerosols can be well simulated by those of calcite and gypsum, which can provide the ratio of gypsum to calcite (or total Ca minerals) in the samples. Moreover, we measured the XANES in both the fluorescence (FL) and conversion electron/He-ion yield (CEY) modes, which are bulk and surface-sensitive analysis, respectively. Based on the XANES data, several conclusions were deduced in this study: (1) the similarity of spectra recorded in the two modes in April suggests that the gypsum fraction (∼10%) in the period reflects the ratio of gypsum to the total Ca minerals in the source area without a significant effect of the formation of the secondary gypsum produced at the surface of the mineral aerosols; (2) a larger gypsum fraction detected in the CEY mode than in the FL mode in January reveals that gypsum is mainly found at the particle surfaces, suggesting that the gypsum in this period was mainly produced secondarily by the reaction of calcite with the acidic SO_x species (=SO₂, sulfuric acid, and acidic sulfate salts) during the transport; (3) considering the neutralization of acidic SO_x species by calcite in mineral aerosols, the Ca speciation data obtained here may be explained by (i) the large supply of mineral aerosols including calcite in April as well as (ii) the large anthropogenic emission of SO₂ generally found in winter in China (which is in January).

Keywords: Mineral aerosol; XANES; Calcium; Gypsum; Neutralization

Chemical composition and sources of fine and coarse aerosol particles in the Eastern Mediterranean by E. Koulouri; S. Saarikoski; C. Theodosi; Z. Markaki; E. Gerasopoulos; G. Kouvarakis; T. Mäkelä; R. Hillamo; N. Mihalopoulos (pp. 6542-6550).

Size-segregated aerosol samples have been collected at a coastal site on Crete Island, Eastern Mediterranean, during the period July 2004–July 2006. In total, 180 samples have been collected and analyzed for the main anions, cations, elements, OC and EC at both fine ( D_a<1.3μm) and coarse (1.3μm< D_a<10μm) fractions. The fine and coarse mode OC and EC values reported in this work are the first long-term data published for the Eastern Mediterranean basin. A significant part of OC in the coarse mode (up to 20%) originates from carbonates, and subsequently particulate organic matter (POM) concentration would be overestimated without carbonate exclusion. The carbonate corrected, coarse mode OC correlates significantly with the dust content, indicating that mineral dust particles can serve as reaction surfaces for different species, including those of man-made origin. In the coarse mode the relative contribution of ionic mass, dust and POM are 50%, 39% and 11%, respectively. In the fine mode up to 60% of the total mass is due to ionic mass and about 30% is due to POM. Factor analysis has identified three components/sources in the coarse mode namely crustal, photochemical and marine while two additional groups were discriminated in the fine mode, residual oil and secondary/combustion aerosols. In particular, natural sources (dust and sea salt) account for up to 60% of the coarse mode variance (versus 20% of the man-made sources), whereas in the fine fraction these two components have almost equal contribution (about 40%).

Keywords: Mass closure; Aerosols; Chemical composition and sources; Eastern Mediterranean

Hydroxyl radical from the reaction between hypochlorite and hydrogen peroxide by Riccardo Castagna; Jason P. Eiserich; Madhu S. Budamagunta; Pierluigi Stipa; Carroll E. Cross; Elisa Proietti; John C. Voss; Lucedio Greci (pp. 6551-6554).

We studied the reaction between hypochlorite anion (⁻OCl) and hydrogen peroxide (H₂O₂) by using spin-trapping agents such as 5,5-dimethyl-1-pyrroline- N-oxide (DMPO) and 5-diethoxy-phosphoryl-5-methyl-1-pyrroline- N-oxide (DEPMPO). The obtained data demonstrate that hydroxyl radical is produced in this reaction. Thus,⁻OCl and H₂O₂^{could assume new relevance in environmental chemistry by representing a potential source of hydroxyl radicals and other oxidant species, such as HO–OCl and}OCl radical.

Keywords: EPR; Hydrogen peroxide; Hydroxyl radical; Singlet oxygen; Sodium hypochlorite

Studies on potential emission of hazardous gases due to uncontrolled open-air burning of waste vehicle tyres and their possible impacts on the environment by Pawan R. Shakya; Pratima Shrestha; Chirika S. Tamrakar; Pradeep K. Bhattarai (pp. 6555-6559).

Uncontrolled open-air burning of waste vehicle tyres causing environmental pollution has become a popular practice in Nepal despite official ban considering the environment and public health hazards. In this study, an experimental model was set up in a laboratory scale in an attempt to understand the potential emission of hazardous gases such as CO, SO₂ and NO₂ due to such activities in Kathmandu Valley and their possible impacts on the environment. For this purpose, four types of tyre were collected representing two from passenger car and two from motorbike category. The emission level of CO in the tyre smoke was measured with a CO gas detector tube while SO₂ and NO₂ were determined by UV–visible spectrophotometer. Among the three types of the gases analyzed, SO₂ was emitted in significantly high levels by all the representative tyre samples. The emission levels of CO, SO₂ and NO₂ ranged from 21to 49, 102to 820 and 3to 9μgg⁻¹, respectively. Results revealed that the emission levels also varied with the tyre types and qualities. The potential emission of the hazardous gases per representative scrap tyre mass was also estimated. Results indicate that the gaseous pollutants due to the tyre fires could make a significant contribution for deterioration of the environmental condition of the Valley or elsewhere.

Keywords: Environmental pollution; Hazardous gases; Kathmandu Valley; Scrap tyre

Effects of sulfur and aromatic contents in gasoline on motorcycle emissions by Yung-Chen Yao; Jiun-Horng Tsai; An-Lin Chang; Fu-Tien Jeng (pp. 6560-6564).

By investigating the effect of sulfur and aromatic contents in gasoline on the criteria pollutant emissions [CO, total hydrocarbons (THCs), and NO x] and on air toxics in the exhaust from a non-catalyst four-stroke motorcycle engine, inferences can be made concerning the effect of fuel composition on motorcycle emissions. The fuels were blended with different contents of sulfur (40 and 150ppmw) and aromatics (20 and 30vol%). The data indicate that the sulfur content does not correlate with the emissions of the criteria pollutants from the catalyst free engine. Instead, lowering aromatic content in gasoline reduced the THC emission by over 30%, especially in the cruising test. The NO x emission, however, showed an inverse correlation with the aromatic content in gasoline. While a reduction of aromatic content in gasoline may decrease emissions of benzene and toluene, it will increase the emission of aldehyde. Since the percentage changes of emission factor of THC and air toxics in the motorcycle were larger than those in passenger cars, the benefit of emission reduction due to fuel composition changes in motorcycles may have significant impacts in health risk analysis.

Keywords: Fuel composition; Four-stroke engine; Exhaust emission; Air toxics

New Directions: It’s time to put the human receptor into air pollution control policy by William W. Nazaroff (pp. 6565-6566).

Sections

Personal tools

Atmospheric Environment (v.42, #26)

Sections

Personal tools

Local resources

Atmospheric Environment (v.42, #26)