Showing papers in "Journal of The Air & Waste Management Association in 2009"

Remote sensing of particulate pollution from space: have we reached the promised land?

Abstract: The recent literature on satellite remote sensing of air quality is reviewed. 2009 is the 50th anniversary of the first satellite atmospheric observations. For the first 40 of those years, atmospheric composition measurements, meteorology, and atmospheric structure and dynamics dominated the missions launched. Since 1995, 42 instruments relevant to air quality measurements have been put into orbit. Trace gases such as ozone, nitric oxide, nitrogen dioxide, water, oxygen/tetraoxygen, bromine oxide, sulfur dioxide, formaldehyde, glyoxal, chlorine dioxide, chlorine monoxide, and nitrate radical have been measured in the stratosphere and troposphere in column measurements. Aerosol optical depth (AOD) is a focus of this review and a significant body of literature exists that shows that ground-level fine particulate matter (PM2.5) can be estimated from columnar AOD. Precision of the measurement of AOD is +/-20% and the prediction of PM2.5 from AOD is order +/-30% in the most careful studies. The air quality needs that can use such predictions are examined. Satellite measurements are important to event detection, transport and model prediction, and emission estimation. It is suggested that ground-based measurements, models, and satellite measurements should be viewed as a system, each component of which is necessary to better understand air quality.

Aerosol Measurement: The Use of Optical Light Scattering for the Determination of Particulate Size Distribution, and Particulate Mass, Including the Semi-Volatile Fraction

Abstract: The GRIMM model 1.107 monitor is designed to measure particle size distribution and particulate mass based on a light scattering measurement of individual particles in the sampled air. The design and operation of the instrument are described. Protocols used to convert the measured size number distribution to a mass concentration consistent with U.S. Environmental Protection Agency protocols for measuring particulate matter (PM) less than 10 microm (PM10) and less than 2.5 microm (PM2.5) in aerodynamic diameter are described. The performance of the resulting continuous monitor has been evaluated by comparing GRIMM monitor PM2.5 measurements with results obtained by the Rupprecht and Patashnick Co. (R&P) filter dynamic measurement system (FDMS). Data were obtained during month-long studies in Rubidoux, CA, in July 2003 and in Fresno, CA, in December 2003. The results indicate that the GRIMM monitor does respond to total PM2.5 mass, including the semi-volatile components, giving results comparable to the FDMS. The data also indicate that the monitor can be used to estimate water content of the fine particles. However, if the inlet to the monitor is heated, then the instrument measures only the nonvolatile material, more comparable to results obtained with a conventional heated filter tapered element oscillating microbalance (TEOM) monitor. A recent modification of the model 180, with a Nafion dryer at the inlet, measures total PM2.5 including the nonvolatile and semi-volatile components, but excluding fine particulate water. Model 180 was in agreement with FDMS data obtained in Lindon, UT, during January through February 2007.

The relation between Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth and PM2.5 over the United States: a geographical comparison by U.S. Environmental Protection Agency regions.

Abstract: Aerosol optical depth (AOD) acquired from satellite measurements demonstrates good correlation with particulate matter with diameters less than 2.5 µm (PM2.5) in some regions of the United States and has been used for monitoring and nowcasting air quality over the United States. This work investigates the relation between Moderate Resolution Imaging Spectroradiometer (MODIS) AOD and PM2.5 over the 10 U.S. Environmental Protection Agency (EPA)-defined geographic regions in the United States on the basis of a 2-yr (2005–2006) match-up dataset of MODIS AOD and hourly PM2.5 measurements. The AOD retrievals demonstrate a geographical and seasonal variation in their relation with PM2.5. Good correlations are mostly observed over the eastern United States in summer and fall. The southeastern United States has the highest correlation coefficients at more than 0.6. The southwestern United States has the lowest correlation coefficient of approximately 0.2. The seasonal regression relations derived for each...

Methods to Assess Carbonaceous Aerosol Sampling Artifacts for IMPROVE and Other Long-Term Networks

Abstract: Volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) adsorb to quartz fiber filters during fine and coarse particulate matter (PM2.5 and PM10, respectively) sampling for thermal/optical carbon analysis that measures organic carbon (OC) and elemental carbon (EC). Particulate SVOCs can evaporate after collection, with a small portion adsorbed within the filter. Adsorbed organic gases are measured as particulate OC, so passive field blanks, backup filters, prefilter organic denuders, and regression methods have been applied to compensate for positive OC artifacts in several long-term chemical speciation networks. Average backup filter OC levels from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network were approximately 19% higher than field blank values. This difference is within the standard deviation of the average and likely results from low SVOC concentrations in the rural to remote environments of most IMPROVE sites. Backup filters from an urba...

Estimating Precision Using Duplicate Measurements

Abstract: Precision is a concept for which there is no universally accepted metric. Reports of precision vary depending on the formula and inclusion criteria used to calculate them. To properly interpret and utilize reported precisions, the user must understand exactly what the precision represents. This paper uses duplicate Interagency Monitoring of Protected Visual Environments (IMPROVE) measurements to illustrate distinctions among different approaches to reporting precision. Three different metrics are used to estimate the precision from the relative differences between the duplicate measurements: the root mean square (RMS), the mean absolute value, and a percentile spread. Precisions calculated using the RMS relative difference yield wide distributions that tend to overestimate most of the observed differences. Precisions calculated using percentiles of the relative differences yield narrower distributions that tend to fit the bulk of the observed differences very well. Precisions calculated using the mean absolute relative difference lie between the other two precision estimates. All three approaches underestimate the observed differences for a small percentage of outliers.

Characterization of the sunset semi-continuous carbon aerosol analyzer.

Abstract: The field-deployable Sunset Semi-Continuous Organic Carbon/Elemental Carbon (Sunset OCEC) aerosol analyzer utilizes the modified National Institute for Occupational Safety and Health thermal-optical method to determine total carbon (TC), organic carbon (OC), and elemental carbon (EC) at near real-time. Two sets of OC and EC are available: thermal OC and EC, and optical OC and EC. The former is obtained by the thermal-optical approach, and the latter is obtained by directly determining EC optically and deriving optical OC from TC. However, the performance of the Sunset OCEC is not yet fully characterized. Two collocated Sunset OCEC analyzers, Unit A and Unit B, were used to determine the pooled relative standard deviation (RSD) and limit of detection (LOD) between September 18 and November 6, 2007 in Richland, WA. The LOD of Unit A was approximately 0.2 microgC/m3 (0.1 microgC/cm2) for TC, optical OC, and thermal OC, and 0.01 microgC/m3 (0.01 microgC/cm2) for optical EC. Similarly, Unit B had an LOD of approximately 0.3 microgC/m3 (0.2 microgC/cm2) for TC, optical OC, and thermal OC, and 0.02 microgC/m3 (0.01 microgC/cm2) for optical EC. The LOD for thermal EC is estimated to be 0.2 microgC/m3 (0.1 microgC/cm2) for both units. The pooled RSDs were 4.9% for TC (carbon mass loadings 0.6-6.0 microgC/cm2), 5.6% for optical OC (carbon mass loadings 0.6-5.4 microgC/cm2), 5.3% for thermal OC (carbon mass loadings 0.6-5.3 microgC/ cm2), and 9.6% for optical EC (carbon mass loadings 0-1.4 microgC/cm2), which indicates good precision between the instruments. The RSD for thermal EC is higher at 24.3% (carbon mass loadings 0-1.2 microgC/cm2). Low EC mass loadings in Richland contributed to the poor RSD of EC. The authors found that excessive noise from the nondispersive infrared (NDIR) laser in the Sunset OCEC analyzer could result in a worsened determination of OC and EC. It is recommended that a "quieter" NDIR laser and detector be used in the Sunset OCEC analyzer to improve quantification. Future work should re-evaluate the precision of the EC parameters in an environment favorable for EC collection. Investigation among quantification differences using various thermal-optical protocols to determine OC and EC is also in need.

Controls on Landfill Gas Collection Efficiency: Instantaneous and Lifetime Performance

Abstract: Estimates of landfill gas (LFG) collection efficiency are required to estimate methane emissions and the environmental performance of a solid waste landfill. The gas collection efficiency varies with time on the basis of the manner in which landfills are designed, operated, and regulated. The literature supports instantaneous collection efficiencies varying between 50% and near 100%, dependent on the cover type and the coverage of the LFG collection system. The authors suggest that the temporally weighted gas collection efficiency, which considers total gas production and collection over the landfill life, is the appropriate way to report collection efficiency. This value was calculated for a range of decay rates representative of refuse buried in arid and wet areas (i.e., >63.5 cm precipitation) and for bioreactor landfills. Temporally weighted collection efficiencies ranging from 67 to 91%, 62 to 86%, and 55 to 78% were calculated at decay rates of 0.02, 0.04, and 0.07 yr(-1), respectively. With aggressive gas collection, as would be implemented for a bioreactor landfill, estimated gas collection efficiency ranged from 84 to 67% at decay rates of 0.04 to 0.15 yr(-1), respectively.

Particle Emissions from Ships: Dependence on Fuel Type

Abstract: This paper presents the results of field emission measurements that have been carried out on the 4500-kW four-stroke main engine on-board a product tanker. Two fuel qualities-heavy fuel oil (HFO) and marine gas oil (MGO)-have been tested on the same engine for comparable load settings. A fuel switch within the marine sector is approaching and the aim of this study is to draw initial conclusions on the subsequent effects on ship exhaust gas composition and emission factors with a focus on particles. Measurements on exhaust gas concentrations of carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), total hydrocarbons (HCs), and particulate matter (PM) were conducted. The gases, except SO2, did not show any major differences between the fuels. Specific PM emissions were generally higher for HFO than for MGO; however, for the smallest size-fraction measured containing particles 0.300.40 mu m in diameter, the opposite is observed. This finding emphasizes that to minimize negative health effects of particles from ships, further regulation may be needed to reduce small-sized particles; a fuel shift to low sulfur fuel alone does not seem to accomplish this reduction. The average of this and previously published data from on-board studies on particle emissions from ships results in emissions factors of 0.33 and 1.34 g/kWh for marine distillate oil (MDO) and HFO, respectively. Accounting for 1 standard deviation in each direction from the average values gives a range of 0.18-0.48 g/kWh for MDO and 0.56-2.12 g/kWh for HFO.

Potential flue gas impurities in carbon dioxide streams separated from coal-fired power plants.

Abstract: For geological sequestration of carbon dioxide (CO2) separated from pulverized coal combustion flue gas, it is necessary to adequately evaluate the potential impacts of flue gas impurities on groundwater aquifers in the case of the CO2 leakage from its storage sites. This study estimated the flue gas impurities to be included in the CO2 stream separated from a CO2 control unit for a different combination of air pollution control devices and different flue gas compositions. Specifically, the levels of acid gases and mercury vapor were estimated for the monoethanolamine (MEA)-based absorption process on the basis of published performance parameters of existing systems. Among the flue gas constituents considered, sulfur dioxide (SO2) is known to have the most adverse impact on MEA absorption. When a flue gas contains 3000 parts per million by volume (ppmv) SO2 and a wet flue gas desulfurization system achieves its 95% removal, approximately 2400 parts per million by weight (ppmw) SO2 could be included in the separated CO2 stream. In addition, the estimated concentration level was reduced to as low as 135 ppmw for the SO2 of less than 10 ppmv in the flue gas entering the MEA unit. Furthermore, heat-stable salt formation could further reduce the SO2 concentration below 40 ppmw in the separated CO2 stream. In this study, it is realized that the formation rates of heat-stable salts in MEA solution are not readily available in the literature and are critical to estimating the levels and compositions of flue gas impurities in sequestered CO2 streams. In addition to SO2, mercury, and other impurities in separated CO2 streams could vary depending on pollutant removal at the power plants and impose potential impacts on groundwater. Such a variation and related process control in the upstream management of carbon separation have implications for groundwater protection at carbon sequestration sites and warrant necessary considerations in overall sequestration planning, engineering, and management.

Particulate air pollution and health effects for cardiovascular and respiratory causes in Temuco, Chile: a wood-smoke-polluted urban area.

Abstract: Temuco is one of the most highly wood-smoke-polluted cities in the world. Its population in 2004 was 340,000 inhabitants with 1587 annual deaths, of which 24% were due to cardiovascular and 11% to respiratory causes. For hospital admissions, cardiovascular diseases represented 6% and respiratory diseases 13%. Emergency room visits for acute respiratory infections represented 28%. The objective of the study presented here was to determine the relationship between air pollution from particulate matter less than or equal to 10 microm in aerodynamic diameter (PM10; mostly PM2.5, or particulate matter 65 yr of age) being the group that presented the greatest risk. The relative risk for respiratory causes, with an increase of 100 microg/m3 of PM10, was 1.163 with a 95% confidence interval (CI) of 1.057-1.279 for mortality, 1.137 (CI 1.096-1.178) for hospital admissions, and 1.162 for ARI (CI 1.144-1.181). There is evidence in Temuco of positive relationships between ambient particulate levels and mortality, hospital admissions, and ARI for cardiovascular and respiratory diseases. These results are consistent with those of comparable studies in other similar cities where wood smoke is the most important air pollution problem.

Combining Regional-and Local-Scale Air Quality Models with Exposure Models for Use in Environmental Health Studies

Abstract: Population-based human exposure models predict the distribution of personal exposures to pollutants of outdoor origin using a variety of inputs, including air pollution concentrations; human activity patterns, such as the amount of time spent outdoors versus indoors, commuting, walking, and indoors at home; microenvironmental infiltration rates; and pollutant removal rates in indoor environments. Typically, exposure models rely upon ambient air concentration inputs from a sparse network of monitoring stations. Here we present a unique methodology for combining multiple types of air quality models (the Community Multi-Scale Air Quality [CMAQ] chemical transport model added to the AERMOD dispersion model) and linking the resulting hourly concentrations to population exposure models (the Hazardous Air Pollutant Exposure Model [HAPEM] or the Stochastic Human Exposure and Dose Simulation [SHEDS] model) to enhance estimates of air pollution exposures that vary temporally (annual and seasonal) and spatially (at census-block-group resolution) in an urban area. The results indicate that there is a strong spatial gradient in the predicted mean exposure concentrations near roadways and industrial facilities that can vary by almost a factor of 2 across the urban area studied. At the high end of the exposure distribution (95th percentile), exposures are higher in the central district than in the suburbs. This is mostly due to the importance of personal mobility factors whereby individuals living in the central area often move between microenvironments with high concentrations, as opposed to individuals residing at the outskirts of the city. Also, our results indicate 20-30% differences due to commuting patterns and almost a factor of 2 difference because of near-roadway effects. These differences are smaller for the median exposures, indicating the highly variable nature of the reflected ambient concentrations. In conjunction with local data on emission sources, microenvironmental factors, and behavioral and socioeconomic characteristics, the combined source-to-exposure modeling methodology presented in this paper can improve the assessment of exposures in future community air pollution health studies.

Development and application of a three-dimensional finite element vapor intrusion model.

Abstract: Details of a three-dimensional finite element model of soil vapor intrusion, including the overall modeling process and the stepwise approach, are provided. The model is a quantitative modeling tool that can help guide vapor intrusion characterization efforts. It solves the soil gas continuity equation coupled with the chemical transport equation, allowing for both advective and diffusive transport. Three-dimensional pressure, velocity, and chemical concentration fields are produced from the model. Results from simulations involving common site features, such as impervious surfaces, porous foundation sub-base material, and adjacent structures are summarized herein. The results suggest that site-specific features are important to consider when characterizing vapor intrusion risks. More importantly, the results suggest that soil gas or subslab gas samples taken without proper regard for particular site features may not be suitable for evaluating vapor intrusion risks; rather, careful attention needs to be given to the many factors that affect chemical transport into and around buildings.

Particle Optics in the Rayleigh Regime

Abstract: Light scattering and absorption by particles suspended in the atmosphere modifies the transfer of solar energy in the atmosphere, thereby influencing global and regional climate change and atmospheric visibility. Of particular interest are the optical properties of particles in the Rayleigh regime, where particles are small compared with the wavelength of the scattered or absorbed light, because these particles experience little gravitational settlement and may have long atmospheric lifetimes. Optical properties of particles in the Rayleigh regime are commonly derived from electromagnetic theory using Maxwell's equations and appropriate boundary conditions. The size dependence of particle scattering and absorption are derived here from the most basic principles for coherent processes such as Rayleigh scattering (i.e., add amplitudes if in phase) and incoherent processes such as absorption (i.e., add cross sections), at the same time yielding understanding of the upper particle size limit for the Rayleigh regime. The wavelength dependence of Rayleigh scattering and absorption are also obtained by adding a basic scale invariance for particle optics. Simple consequences for particle single-scattering albedo ("whiteness") and the optical measurement of particle mass densities are explained. These alternative derivations complement the conventional understanding obtained from electromagnetic theory.

Evaluation of wood chip-based biofilters to reduce odor, hydrogen sulfide, and ammonia from swine barn ventilation air.

Abstract: A pilot-scale biofilter was developed in which two types of wood chips (western cedar [WC] and 2-in. hardwood [HW]) were examined to treat odor emissions from a deep-pit swine finishing facility in central Iowa. The biofilters were operated continuously for 13 weeks at different airflow rates resulting in variable empty bed residence times (EBRTs) from 1.6 to 7.3 sec. The effects of three media moisture levels were also evaluated. A dynamic forced-choice olfactometer was used to evaluate odor concentrations from both the control (inlet) plenum and biofilter treatments (outlet). Hydrogen sulfide (H2S) and ammonia (NH3) concentrations were also measured from these olfactometry samples. Solid-phase microextraction (SPME) polydimethylsiloxane (PDMS)/divinylbenzene (DVB) 65-microm fibers were used to extract volatile organic compounds from both the control plenum and biofilter treatments. Analyses of separated odors were carried out using a gas chromatography-mass spectrometry-olfactometry (GC-MS-O) system. Static sample results indicated that both types of chips achieved significant reductions in odor (average 70.1 and 82.3% for HW and WC, respectively), H2S (average 81.8 and 88.6% for HW and WC, respectively) and NH3 (average 43.4 and 74% for HW and WC, respectively) concentrations. GC-MS-O aromagram results showed both treatments reached high odor reduction efficiency (average 99.4 and 99.8% for HW and WC, respectively). The results also showed that maintaining proper moisture content and a minimum EBRT are critical to the success of wood chip-based biofilters.

Methodology to estimate particulate matter emissions from certified commercial aircraft engines.

Abstract: Today, about one-fourth of U.S. commercial service airports, including 41 of the busiest 50, are either in nonattainment or maintenance areas per the National Ambient Air Quality Standards. U.S. aviation activity is forecasted to triple by 2025, while at the same time, the U.S. Environmental Protection Agency (EPA) is evaluating stricter particulate matter (PM) standards on the basis of documented human health and welfare impacts. Stricter federal standards are expected to impede capacity and limit aviation growth if regulatory mandated emission reductions occur as for other non-aviation sources (i.e., automobiles, power plants, etc.). In addition, strong interest exists as to the role aviation emissions play in air quality and climate change issues. These reasons underpin the need to quantify and understand PM emissions from certified commercial aircraft engines, which has led to the need for a methodology to predict these emissions. Standardized sampling techniques to measure volatile and nonvo...

Analytical determination of the aerosol organic mass-to-organic carbon ratio.

Abstract: Particulate matter (PM) with an aerodynamic diameter < or = 2.5 microm (PM2.5) was collected daily (mid-July 1998 to the end of December 1999) over a 24-hr sampling period in a mixed light industrial-residential area in Atlanta, GA, to provide a subset of data for the Aerosol Research and Inhalation Epidemiology Study (ARIES). This study included the measurement of organic carbon (OC), elemental carbon (EC), and individual organic compounds. OC and EC average mean concentrations were 4.50 +/- 0.33 and 2.08 +/- 0.19 microg/m3, respectively. The ratio of organic matter mass (OM) to OC in PM2.5 aerosols in Atlanta was measured using three different approaches: (1) solvent extract residue gravimetric masses to individual OC concentrations of sequential apolar to polar solvent extracts (dichloromethane, acetone, and water); (2) mass balance of the PM2.5 measured gravimetric mass minus the mass concentrations of the inorganic/elemental constituents to the total OC concentration; and (3) polar organic compound speciation with the concentration weighted ratio to the total OC concentration. We found very good agreement between approach 1 and 2. The average OM/OC ratio calculated from the extract residue mass was 2.14 +/- 0.17. The average OM/OC ratio determined by mass balance was 2.16 +/- 0.43 for the whole period. The concentration weighted ratio calculated from the concentrations of polar organic compounds ranged between 1.55 and 1.72, which was likely a lower limit for the ratio because of the limited number of the polar organic compounds that can be quantified using gas chromatographic methods. We found seasonal differences with an OM/OC range of 1.77 in December 1999 to 2.39 in July 1999. These results suggest that the previously accepted value of 1.4 for the OM/OC ratio was too low even for urban locations during the winter months. Molecular-level speciation of the PM2.5-associated organic compounds showed that the concentrations of the molecular markers for wood smoke represented approximately 12-15% of the total polar organic compound concentrations during the winter months.

Application of optimally scaled target factor analysis for assessing source contribution of ambient PM10.

Abstract: Speciated coarse particulate matter (PM10) data ob tained at three air quality monitoring sites in a highly industrialized area in Spain between 2002 and 2007 were analyzed for assessing source contribution of ambient particulate matter (PM). The source apportionment of PM in this area is an especially difficult task. There are industrial mineral dust emissions that need to be separately quantified from the natural sources of mineral PM. On the other hand, the diversity of industrial processes in the area results in a puzzling industrial emissions scenario. To solve this complex problem, a two-step methodology based on the possibilities of the Multilinear Engine was used. Application of positive matrix factorization to the dataset allowed the identification of nine factors relevant to the study area. This preliminary analysis permitted resolving two mineral factors. As a second step, a target rotation was implemented for transforming the mineral factors into experimentally characterized soil resu...

Effect of E85 on Tailpipe Emissions from Light-Duty Vehicles.

Abstract: E85, which consists of nominally 85% fuel grade ethanol and 15% gasoline, must be used in flexible-fuel (or "flex-fuel") vehicles (FFVs) that can operate on fuel with an ethanol content of 0-85%. Published studies include measurements of the effect of E85 on tailpipe emissions for Tier 1 and older vehicles. Car manufacturers have also supplied a large body of FFV certification data to the U.S. Environmental Protection Agency, primarily on Tier 2 vehicles. These studies and certification data reveal wide variability in the effects of E85 on emissions from different vehicles. Comparing Tier 1 FFVs running on E85 to similar non-FFVs running on gasoline showed, on average, significant reductions in emissions of oxides of nitrogen (NOx; 54%), non-methane hydrocarbons (NMHCs; 27%), and carbon monoxide (CO; 18%) for E85. Comparing Tier 2 FFVs running on E85 and comparable non-FFVs running on gasoline shows, for E85 on average, a signifi-cant reduction in emissions of CO (20%), and no signifi-cant effect on emissions of non-methane organic gases (NMOGs). NOx emissions from Tier 2 FFVs averaged approximately 28% less than comparable non-FFVs. However, perhaps because of the wide range of Tier 2 NOx standards, the absolute difference in NOx emissions between Tier 2 FFVs and non-FFVs is not significant (P =0.28). It is interesting that Tier 2 FFVs operating on gasoline produced approximately 13% less NMOGs than non-FFVs operating on gasoline. The data for Tier 1 vehicles show that E85 will cause significant reductions in emissions of benzene and butadiene, and significant increases in emissions of formaldehyde and acetaldehyde, in comparison to emissions from gasoline in both FFVs and non-FFVs. The compound that makes up the largest proportion of organic emissions from E85-fueled FFVs is ethanol.

Deciphering the Role of Radical Precursors during the Second Texas Air Quality Study

Abstract: The Texas Environmental Research Consortium (TERC) funded significant components of the Second Texas Air Quality Study (TexAQS II), including the TexAQS II Radical and Aerosol Measurement Project (TRAMP) and instrumented flights by a Piper Aztec aircraft. These experiments called attention to the role of short-lived radical sources such as formaldehyde (HCHO) and nitrous acid (HONO) in increasing ozone productivity. TRAMP instruments recorded daytime HCHO pulses as large as 32 parts per billion (ppb) originating from upwind industrial activities in the Houston Ship Channel, where in situ surface monitors detected HCHO peaks as large as 52 ppb. Moreover, Ship Channel petrochemical flares were observed to produce plumes of apparent primary HCHO. In one such combustion plume that was depleted of ozone by large emissions of oxides of nitrogen (NOx), the Piper Aztec measured a ratio of HCHO to carbon monoxide (CO) 3 times that of mobile sources. HCHO from uncounted primary sources or ozonolysis of und...

Zeolite formation from coal fly ash and its adsorption potential.

Abstract: The possibility in converting coal fly ash (CFA) to zeolite was evaluated. CFA samples from the local power plant in Prachinburi province, Thailand, were collected during a 3-month time span to account for the inconsistency of the CFA quality, and it was evident that the deviation of the quality of the raw material did not have significant effects on the synthesis. The zeolite product was found to be type X. The most suitable weight ratio of sodium hydroxide (NaOH) to CFA was approximately 2.25, because this gave reasonably high zeolite yield with good cation exchange capacity (CEC). The silica (Si)-to-aluminum (Al) molar ratio of 4.06 yielded the highest crystallinity level for zeolite X at 79% with a CEC of 240 meq/100 g and a surface area of 325 m2/g. Optimal crystallization temperature and time were 90 degrees C and 4 hr, respectively, which gave the highest CEC of approximately 305 meq/100 g. Yields obtained from all experiments were in the range of 50-72%.

Comparison of GOES and MODIS Aerosol Optical Depth (AOD) to Aerosol Robotic Network (AERONET) AOD and IMPROVE PM2.5 Mass at Bondville, Illinois

Abstract: Collocated Interagency Monitoring of Protected Visual Environments (IMPROVE) particulate matter (PM) less than 2.5 microm in aerodynamic diameter (PM2.5) chemically speciated data, mass of PM less than 10 microm in aerodynamic diameter (PM10), and Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) and size distribution at Bondville, IL, were compared with satellite-derived AOD. This was done to evaluate the quality of the Geostationary Operational Environmental Satellite (GOES) and Moderate Resolution Imaging Spectroradiometer (MODIS) AOD data and their potential to predict surface PM2.5 concentrations. MODIS AOD correlated better to AERONET AOD (r = 0.835) than did GOES AOD (r = 0.523). MODIS and GOES AOD compared better to AERONET AOD when the particle size distribution was dominated by fine mode. For all three AOD methods, correlation between AOD and PM2.5 concentration was highest in autumn and lowest in winter. The AERONET AOD-PM2.5 relationship was strongest with moderate relative humidity (RH). At low RH, AOD attributable to coarse mass degrades the relationship; at high RH, added AOD from water growth appears to mask the relationship. For locations such as many in the central and western United States with substantial coarse mass, coarse mass contributions to AOD may make predictions of PM2.5 from AOD data problematic. Seasonal and diurnal variations in particle size distributions, RH, and seasonal changes in boundary layer height need to be accounted for to use satellite AOD to predict surface PM2.5.

Current understanding of ultrafine particulate matter emitted from mobile sources.

Abstract: The physics and chemistry of ultrafine particulate matter (UFPM) associated with mobile source emissions is reviewed. UFPM includes those particles that are less than 0.1 μm in diameter. Measurements of UFPM emitted from mobile sources have been conducted in the laboratory, on roadways, and downwind of roadways. In addition, UFPM formation and evolution have been modeled and the modeling results have been compared with available measurements. The results of those measurement programs and modeling studies are synthesized into a coherent description of the formation of UFPM in mobile source emissions and its subsequent evolution in the ambient atmosphere. Recommendations are provided to address the gaps in our current understanding of the processes leading to the formation of UFPM, its chemical composition, and its evolution in the atmosphere

The social distribution of neighborhood-scale air pollution and monitoring protection.

Abstract: The potential for inequities between population subgroups in air pollution exposures and in regulatory protection because of small-scale intraurban differences in outdoor air pollution and air quality monitoring are studied here. The focus subgroups are blacks, Hispanics, whites, and the population living below poverty, with Tampa, FL, used as the case study area for quantitative analyses. A geographical database is developed for the surrounding county that includes population demographics, source locations, monitor locations, and air pollutant concentrations. Data included are residential population demographics at the block-group spatial scale from the year 2000 U.S. Census, U.S. Environmental Protection Agency (EPA) Toxic Releases Inventory source locations and air source release amounts, EPA Air Quality System monitoring data, and Florida major highway source locations and roadway traffic data. This database is applied for analysis of the spatial relationships between residence locations of population subgroups and outdoor air pollution surrogates. A quantitative index to evaluate the inequity between subpopulations is developed and applied. Findings include that blacks, Hispanics, and people living in poverty are disproportionately living closer to sources of air pollution and further from regulatory air quality monitoring sites compared with the overall county population. Conversely, whites are disproportionately living away from sources and near monitoring sites. Analysis of the regulatory monitoring guidelines indicates that recent changes in those guidelines may exacerbate existent inequities. The results suggest disparities in exposures to air pollution, disparities in regulatory monitoring representation, and the need for more monitoring and analyses at smaller spatial scales.

Carbonyl compounds and toxicity assessments of emissions from a diesel engine running on biodiesels

Abstract: This study elucidates the effect of biodiesel on the emission of carbonyl compounds generated from a diesel engine (generator), and the related biotoxicity characteristics. The Microtox test and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay were conducted to evaluate the acute toxicity and cytotoxicity, respectively, of gaseous extracts from diesel engine exhaust. The engine was tested using diesel fuel and biodiesel blends (10, 30, 50, 75, and 100% of biodiesel by volume). The operating conditions of the diesel engine were set as idling, 10, 33, and 55% loads. The regulated emissions of carbon monoxide (CO), nitrogen oxides (NOx), and carbon dioxide (CO2) were monitored. The carbonyl compounds in the exhaust were collected in 2,4-dinitrophenylhydrazine (2,4-DNPH) solution in an impinger and converted to corresponding hydrazone derivatives, which were then analyzed using high performance liquid chromatography (HPLC) with an ultraviolet (UV) detector. Analysis results indicate that the carbonyl compound emissions increased when the engine was run on biodiesels at all of the loadings; however, the total concentration of emitted carbonyls did not increase with the biodiesel content. The dominant carbonyls (formalde-hyde, acetaldehyde, acrolein, and acetone) accounted for 70 to 90% of all carbonyl emissions in the engine exhaust. The concentrations of CO2 and NOx from B10 were quite similar to those from diesel. Finally, in the toxicity assessments, B10 had a higher acute toxicity and cytotoxicity than diesel, indicating that blending with biodiesel may have adverse health effects because of toxic gas emissions. At various engine loads, higher toxicities were associated with greater carbonyl emissions in diesel exhaust, but not in B10, indicating that the carbonyls may not be the major pollutants that induce the toxicity of emissions from biodiesel.

Effect of Open Channel Filter on Particle Emissions of Modern Diesel Engine

Abstract: Particle emissions of modern diesel engines are of a particular interest because of their negative health effects. The special interest is in nanosized solid particles. The effect of an open channel filter on particle emissions of a modern heavy-duty diesel engine (MAN D2066 LF31, model year 2006) was studied. Here, the authors show that the open channel filter made from metal screen efficiently reduced the number of the smallest particles and, notably, the number and mass concentration of soot particles. The filter used in this study reached 78% particle mass reduction over the European Steady Cycle. Considering the size-segregated number concentration reduction, the collection efficiency was over 95% for particles smaller than 10 nm. The diffusion is the dominant collection mechanism in small particle sizes, thus the collection efficiency decreased as particle size increased, attaining 50% at 100 nm. The overall particle number reduction was 66-99%, and for accumulation-mode particles the number concentration reduction was 62-69%, both depending on the engine load.

A new method for determining the initial mobile formaldehyde concentrations, partition coefficients, and diffusion coefficients of dry building materials.

Abstract: The initial mobile formaldehyde concentration, C(m,0); the partition coefficient, K; and the diffusion coefficient, D, of a dry building material are key parameters to characterize formaldehyde emissions from the building material. The solvent extraction method and direct thermal desorption method can overestimate C(m,0) because of high temperature. A new method has been developed to determine C(m,0) under similar conditions to common indoor environment, together with K and D. In the proposed method, the tested materials are placed in an airtight environmental chamber for which the temperature can be controlled by a water bath, then the materials undergo a multisorption/emission process and the instantaneous formaldehyde concentration in the chamber is recorded. The K and C(m,0) are determined from the equilibrium concentrations after every sorption by means of the linear least-square regression, and D is obtained by fitting the concentration at the emission stage into a mass-transfer-based model in the literature. Four kinds of wooden medium-density boards are tested. The C(m,0) measured using this method is the mobile formaldehyde concentration in the material, which differs significantly from the total formaldehyde concentration in the material measured by using the traditional method recommended by the Chinese standard (GB/T 17657-1999) extraction method. This means that the mobile formaldehyde takes only a small portion of the total quantity in the tested material. The K, D, and C(m,0) values measured using this new method are used to predict formaldehyde concentrations for sorption processes. The results agree well with experimental data. In addition, some factors influencing the accuracy are analyzed.

Methods for Characterizing Fine Particulate Matter Using Ground Observations and Remotely Sensed Data: Potential Use for Environmental Public Health Surveillance

Abstract: This study describes and demonstrates different techniques for surface fitting daily environmental hazards data of particulate matter with aerodynamic diameter less than or equal to 2.5 μm (PM2.5) for the purpose of inte grating respiratory health and environmental data for the Centers for Disease Control and Prevention (CDC) pilot study of Health and Environment Linked for Information Exchange (HELIX)–Atlanta. It presents a methodology for estimating daily spatial surfaces of ground-level PM2.5 concentrations using the B-Spline and inverse distance weighting (IDW) surface-fitting techniques, leveraging National Aeronautics and Space Administration (NASA) Moderate Resolution Imaging Spectrometer (MODIS) data to complement U.S. Environmental Protection Agency (EPA) ground observation data. The study used measurements of ambient PM2.5 from the EPA database for the year 2003 as well as PM2.5 estimates derived from NASA’s satellite data. Hazard data have been processed to derive the surrogate PM2.5 e...

Modeling regional/urban ozone and particulate matter in Beijing, China.

Abstract: This paper examines Beijing air quality in the winter and summer of 2001 using an integrated air quality modeling system (Fifth Generation Mesoscale Meteorological Model [MM5]/Community Multiscale Air Quality [CMAQ]) in nested mode. The National Aeronautics and Space Administration (NASA) Transport and Chemical Evolution over the Pacific (TRACE-P) emission inventory is used in the 36- (East Asia), 12- (East China), and 4-km (greater Beijing area) domains. Furthermore, we develop a local Beijing emission inventory that is used in the 4-km domain. We also construct a corroborated mapping of chemical species between the TRACE-P inventory and the Carbon Bond IV (CB-IV) chemical mechanism before the integrated modeling system is applied to study ozone (O3) and particulate matter (PM) in Beijing. Meteorological data for the integrated modeling runs are extracted from MM5. Model results show O3 hourly concentrations in the range of 80-159 parts per billion (ppb) during summer in the urban areas and up to 189 ppb downwind of the city. High fine PM (PM2.5) concentrations (monthly average of 75 microg x m(-3) in summer and 150 microg x m(-3) in winter) are simulated over the metropolitan and down-wind areas with significant secondary constituents. A comparison against available O3 and PM measurement data in Beijing is described. We recommend refinements to the developed local Beijing emission inventory to improve the simulation of Beijing's air quality. The 4-km modeling configuration is also recommended for the development of air pollution control strategies.

Impact of fly ash composition on mercury speciation in simulated flue gas.

Abstract: The impact of different fly ash samples on mercury speciation in simulated flue gas at 140 degrees C was evaluated in this study. Experiments were conducted in a fixed bed reactor to determine the impact of fly ash morphological characteristics and chemical composition on mercury uptake and oxidation. No homogeneous mercury oxidation was observed at 140 degrees C. Mercury uptake tests with different fly ash samples revealed that loss on ignition (LOI), surface area, and particle size all had positive effects on mercury oxidation and adsorption (i.e., as the above parameters increased, mercury adsorption and oxidation also increased). Experiments with pure inorganic components showed that alumina (A12O3), silica (SiO2), calcium oxide (CaO), magnesium oxide (MgO), and titania (TiO2) do not promote mercury oxidation or adsorption. Ferric oxide (Fe2O3) and unburned carbon, on the other hand, showed significant mercury oxidation and capture.

Remote Sensing of Particulate Pollution from Space: Have We Reached the Promised Land?

Abstract: The Critical Review of Hoff and Christopher, along with the discussants, provides an important perspective on the interface between satellite measurement science and air quality observations. A top-down picture of the usefulness of satellite observations in terms of air quality regulatory and technical support requirements can be summarized. The air quality requirements are (1) determination of compliance with the ambient air quality standards, (2) inference of human and ecosystem exposure, (3) identification of intra- and intercontinental events relevant to EE, (4) establishment of trends in ambient concentrations relevant to accountability, (5) regulatory and forecast model applications, and (6) extension of fundamental knowledge relevant to air quality. Each of these topics is important to air quality management, and each has detailed technical issues associated with spatial and temporal resolution, accuracy, and precision, etc. In any case, one can summarize the broad capabilities of measurement systems to address these requirements as listed in Table 1. From this rather superficial summary table, investigators should be encouraged to forward increased interaction between the various measurement communities and to facilitate the utility of a comprehensive portfolio of measurements and adjunct analyses for improved air quality applications. The Critical Review has done much to educate air quality scientists on the possibilities for using satellite remote sensing for various purposes. However, space scientists also need a better education on air quality science. Recently published reviews on PM air quality measurements are available that complement the Hoff-Christopher paper on this topic. The need for greater collaboration of air quality and space scientists is evident in an article published in the July issue of the journal. Al-Hamdan et al. provide an interesting and useful analysis of relationships between surface air quality and space-based satellite AOD to estimate human exposure. They obtain mostly urban PM data from EPA's Air Quality System (AQS), but they neglect the potentially more useful PM2.5 and chemical speciation data from the nonurban Interagency Monitoring of Protected Visual Environments (IMPROVE) and the Southeastern Aerosol Research and Characterization (SEARCH) networks. They correlate PM2.5 mass with optical depth, although visibility assessments show that light extinction is better represented by a weighted sum of PM2.5 sulfate, nitrate, organic carbon, elemental carbon, and soil dust. Their comparison of hourly measurements with filter measurements does not specify the source of the hourly values as TEOM or BAM. Spatial outliers for ground-level measurements are removed to improve the correlation of PM2.5 with AOD, although these "outliers" are probably real values that relate to human exposure or a nearby source effect. The point here is not to overly criticize a good publication that will be highly cited. The intent is to demonstrate the value of air quality and space scientists working together more closely on this topic. This is something the review authors alluded to in their review, but if, as they concluded, the "promised land" has not been reached, then perhaps it is an appropriate time for the atmospheric community to ask, "Can near-term satellite observations play a role in characterizing broad-based (outdoor) exposure to pollutants and consequently influence public health improvement?" and, if so, then, "What comprehensive, integrated system is needed if satellite observations are to be used together with ground-based observations and modeling to continue improving air quality management options?"