Receptor model-based source apportionment of particulate pollution in Hyderabad, India.

Air quality in Hyderabad, India, often exceeds the national ambient air quality standards, especially for particulate matter (PM), which, in 2010, averaged 82.2 ± 24.6, 96.2 ± 12.1, and 64.3 ± 21.2 µg/m(3) of PM10, at commercial, industrial, and residential monitoring stations, respectively, exceeding the national ambient standard of 60 µg/m(3). In 2005, following an ordinance passed by the Supreme Court of India, a source apportionment study was conducted to quantify source contributions to PM pollution in Hyderabad, using the chemical mass balance (version 8.2) receptor model for 180 ambient samples collected at three stations for PM10 and PM2.5 size fractions for three seasons. The receptor modeling results indicated that the PM10 pollution is dominated by the direct vehicular exhaust and road dust (more than 60%). PM2.5 with higher propensity to enter the human respiratory tracks, has mixed sources of vehicle exhaust, industrial coal combustion, garbage burning, and secondary PM. In order to improve the air quality in the city, these findings demonstrate the need to control emissions from all known sources and particularly focus on the low-hanging fruits like road dust and waste burning, while the technological and institutional advancements in the transport and industrial sectors are bound to enhance efficiencies. Andhra Pradesh Pollution Control Board utilized these results to prepare an air pollution control action plan for the city.

Quantification of organic carbon and black carbon emissions, distribution, and carbon variation in diverse vegetative ecosystems across India.

Black Carbon (BC) and Organic Carbon (OC) are the principal chemical aerosol components generated during combustion, both of which play a key role in air pollution, human health and climate change. Several studies of OC and BC have been conducted over India to assess the contribution from household and fossil fuel-based sources; however, studies on their emissions and their contribution from forest and cropland fires are quite limited. To address this issue, as part of this research, we derived a vegetation burning-based inventory of BC and OC aerosols over India at a resolution of 250 m × 250 m. Using a consumed biomass technique, we estimated emissions based on updated emission factor estimates. During the fire season in India (March-June), the mean OC and BC emissions were 2.1 ± 5.2 × 1013 kg per year and 1.8 ± 4.4 × 1012 kg per year, respectively. Andhra Pradesh had the highest total carbonaceous aerosol emissions during the study period. Forest fires were prevalent in the northeastern states, while agricultural fires were prevalent in Gujarat, Chhattisgarh, Odisha, Madhya Pradesh, Bihar, Tripura, Uttar Pradesh, and Andhra Pradesh. The previous inventory, conducted at a coarser resolution (25 km × 25 km), overestimated open burning by 5 Mt. Our results were highly correlated with global bottom-up model values, especially the Fire Inventory (FINN). Our analysis showed that vegetative burning contributed 80.32% of the total carbon stock, with agricultural burning being the largest source of vegetative burning. Based on these findings, measures and strategies to control agricultural burning which would reduce significantly the total emissions of BC and OC with implications to improvement in air quality, human health and climate should be planned.

Characterizing mineral dusts and other aerosols from the Middle East--Part 1: ambient sampling.

The purpose of the Enhanced Particulate Matter Surveillance Program was to provide scientifically founded information on the chemical and physical properties of dust collected over a period of approximately 1 year in Djibouti, Afghanistan (Bagram, Khowst), Qatar, United Arab Emirates, Iraq (Balad, Baghdad, Tallil, Tikrit, Taji, Al Asad), and Kuwait (northern, central, coastal, and southern regions). Three collocated low-volume particulate samplers, one each for the total suspended particulate matter, < 10 micro m in aerodynamic diameter (PM(10)) particulate matter, and < 2.5 micro m in aerodynamic diameter (PM(2.5)) particulate matter, were deployed at each of the 15 sites, operating on a '1 in 6' day sampling schedule. Trace-element analysis was performed to measure levels of potentially harmful metals, while major-element and ion-chemistry analyses provided an estimate of mineral components. Scanning electron microscopy with energy dispersive spectroscopy was used to analyze the chemical composition of small individual particles. Secondary electron images provided information on particle size and shape. This study shows the three main air pollutant types to be geological dust, smoke from burn pits, and heavy metal condensates (possibly from metals smelting and battery manufacturing facilities). Non-dust storm events resulted in elevated trace metal concentrations in Baghdad, Balad, and Taji in Iraq. Scanning-electron-microscopy secondary electron images of individual particles revealed no evidence of freshly fractured quartz grains. In all instances, quartz grains had rounded edges and mineral grains were generally coated by clay minerals and iron oxides.

Characterizing mineral dusts and other aerosols from the Middle East--Part 2: grab samples and re-suspensions.

The purpose of the Enhanced Particulate Matter Surveillance Program was to provide scientifically founded information on the chemical and physical properties of dust collected during a period of approximately 1 year in Djibouti, Afghanistan (Bagram, Khowst), Qatar, United Arab Emirates, Iraq (Balad, Baghdad, Tallil, Tikrit, Taji, Al Asad), and Kuwait (northern, central, coastal, and southern regions). To fully understand mineral dusts, their chemical and physical properties, as well as mineralogical inter-relationships, were accurately established. In addition to the ambient samples, bulk soil samples were collected at each of the 15 sites. In each case, approximately 1 kg of soil from the top 10 mm at a previously undisturbed area near the aerosol sampling site was collected. The samples were air-dried and sample splits taken for soil analysis. Further sample splits were sieved to separate the < 38 micro m particle fractions for mineralogical analysis. Examples of major-element and trace-element chemistry, mineralogy, and other physical properties of the 15 grab samples are presented. The purpose of the trace-element analysis was to measure levels of potentially harmful metals while the major-element and ion-chemistry analyses provided an estimate of mineral components. X-ray diffractometry provided a measure of the mineral content of the dust. Scanning electron microscopy with energy dispersive spectroscopy was used to analyze chemical composition of small individual particles. From similarities in the chemistry and mineralogy of re-suspended and ambient sample sets, it is evident that portions of the ambient dust are from local soils.

Fugitive dust emissions from paved road travel in the Lake Tahoe basin.

The clarity of water in Lake Tahoe has declined substantially over the past 40 yr. Causes of the degradation include nitrogen and phosphorous fertilization of the lake waters and increasing amounts of inorganic fine sediment that can scatter light. Atmospheric deposition is a major source of fine sediment. A year-round monitoring study of road dust emissions around the lake was completed in 2007 using the Testing Re-entrained Aerosol Kinetic Emissions from Roads (TRAKER) system developed at the Desert Research Institute (DRI). Results of this study found that, compared with the summer season, road dust emissions increased by a factor of 5 in winter, on average, and about a factor of 10 when traction control material was applied to the roads after snow events. For winter and summer, road dust emission factors (grams coarse particulate matter [PM10] per vehicle kilometer traveled [g/vkt]) showed a decreasing trend with the travel speed of the road. The highest emission factors were observed on very low traffic volume roads on the west side of the lake. These roads were composed of either a 3/8-in. gravel material or had degraded asphalt. The principle factors influencing road dust emissions in the basin are season, vehicle speed (or road type), road condition, road grade, and proximity to other high-emitting roads. Combined with a traffic volume model, an analysis of the total emissions from the road sections surveyed indicated that urban areas (in particular South Lake Tahoe) had the highest emitting roads in the basin.

Real-world particulate matter and gaseous emissions from motor vehicles in a highway tunnel.

Recent studies have linked atmospheric particulate matter with human health problems. In many urban areas, mobile sources are a major source of particulate matter (PM) and the dominant source of fine particles or PM2.5 (PM smaller than 2.5 pm in aerodynamic diameter). Dynamometer studies have implicated diesel engines as being a significant source of ultrafine particles (< 0.1 microm), which may also exhibit deleterious health impacts. In addition to direct tailpipe emissions, mobile sources contribute to ambient particulate levels by brake and tire wear and by resuspension of particles from pavement. Information about particle emission rates, size distributions, and chemical composition from in-use light-duty (LD) and heavy-duty (HD) vehicles is scarce, especially under real-world operating conditions. To characterize particulate emissions from a limited set of in-use vehicles, we studied on-road emissions from vehicles operating under hot-stabilized conditions, at relatively constant speed, in the Tuscarora Mountain Tunnel along the Pennsylvania Turnpike from May 18 through 23, 1999. There were five specific aims of the study. (1) obtain chemically speciated diesel profiles for the source apportionment of diesel versus other ambient constituents in the air and to determine the chemical species present in real-world diesel emissions; (2) measure particle number and size distribution of chemically speciated particles in the atmosphere; (3) identify, by reference to data in years past, how much change has occurred in diesel exhaust particulate mass; (4) measure particulate emissions from LD gasoline vehicles to determine their contribution to the observed particle levels compared to diesels; and (5) determine changes over time in gas phase emissions by comparing our results with those of previous studies. Comparing the results of this study with our 1992 results, we found that emissions of C8 to C20 hydrocarbons, carbon monoxide (CO), and carbon dioxide (CO2) from HD diesel emissions substantially decreased over the seven-year period. Particulate mass emissions showed a similar trend. Considering a 25-year period, we observed a continued downward trend in HD particulate emissions from approximately 1,100 mg/km in 1974 to 132 mg/km (reported as PM2.5) in this study. The LD particle emission factor was considerably less than the HD value, but given the large fraction of LD vehicles, emissions from this source cannot be ignored. Results of the current study also indicate that both HD and LD vehicles emit ultrafine particles and that these particles are preserved under real-world dilution conditions. Particle number distributions were dominated by ultrafine particles with count mean diameters of 17 to 13 nm depending on fleet composition. These particles appear to be primarily composed of sulfur, indicative of sulfuric acid emission and nucleation. Comparing the 1992 and 1999 HD emission rates, we observed a 48% increase in the NOx/CO2 emissions ratio. This finding supports the assumption that many new-technology diesel engines conserve fuel but increase NOx emissions.

A quantitative description of vehicle exhaust particle size distributions in a highway tunnel.

During the period May 18-May 22, 1999, a comprehensive study was conducted in the Tuscarora Mountain Tunnel on the Pennsylvania Turnpike to measure real-world motor-vehicle emissions. As part of this study, size distributions of particle emissions were determined using a scanning mobility particle sizer. Each measured size distribution consisted of two modes: a nucleation mode with midpoint diameter less than 20 nm and an accumulation mode with midpoint diameter less than 100 nm. The nucleation and accumulation components in some distributions also exhibited second maxima, which implies that such particle size distributions are superpositions of two particle size distributions. This hypothesis was utilized in fitting the particle size distributions that exhibited second maxima with four lognormal distributions, two for the nucleation mode and two for the accumulation mode. The fitting assumed that the observed particle size distribution was a combination of two bimodal log-normal distributions, one attributed to the heavy-duty diesel (HDD) vehicles and another attributed either to a different class of HDD vehicles or to the light-duty spark ignition vehicles. Based on this method, estimated particle production rates were 1.8 x 10(13) and 2.8 x 10(14) particles/vehicle-km for light-duty spark ignition and HDD vehicles, respectively, which agreed with independently obtained estimates.

Development and validation of a lead emission inventory for the Greater Cairo area.

Studies that investigate the environmental health risks to Cairo residents invariably conclude that lead is one of the area's major health hazards. The Cairo Air Improvement Project (CAIP), which was implemented by a team led by Chemonics International, funded by USAID in partnership with the Egyptian Environmental Affairs Agency (EEAA), started developing a lead emission inventory for the greater Cairo (GC) area in 1998. The inventory contains a list by major source of the annual lead emissions in the GC area. Uses of the inventory and associated database include developing effective regulatory and control strategies, assessing emissions trends, and conducting modeling exercises. This paper describes the development of the current lead emissions inventory (1999-2010), along with an approach to develop site specific emission factors and measurements to validate the inventory. This paper discusses the major sources of lead in the GC area, which include lead smelters, Mazout (heavy fuel oil) combustion, lead manufacturing batteries factories, copper foundries, and cement factories. Included will be the trend in the lead emissions inventory with regard to the production capacity of each source category. In addition, the lead ambient measurements from 1999 through 2010 are described and compared with the results of Source Attribution Studies (SAS) conducted in 1999, 2002, and 2010. Due to EEAA/CAIP efforts, a remarkable decrease in more than 90% in lead emissions was attained for 2007.

Urban PM source apportionment mapping using microscopic chemical imaging.

To evaluate the health impacts of particulate matter and develop effective pollutant abatement strategies, one needs to know the source contributions to the observed concentrations. The most common approach involves the collection of ambient air samples on filters, laboratory analyses to quantify the chemical composition, and application of receptor modeling methods. This approach is expensive and time consuming and limits the ability to monitor the temporal and spatial impacts from different pollutant sources. An alternative method for apportioning the sources of ambient PM is the application of microscopic chemical imaging (MCI). The MCI method involves measuring individual particle's fluorescence and source attribution is based on the individual particle analysis coupled with identification from a source library. Using this approach, the apportionment of ambient PM can be performed in near real time, which allows for the generation of temporal and spatial maps of pollutant source impacts in an urban area.

Evaluating vehicle re-entrained road dust and its potential to deposit to Lake Tahoe: a bottom-up inventory approach.

Identifying hotspot areas impacted by emissions of dust from roadways is an essential step for mitigation. This paper develops a detailed road dust PM10 emission inventory using a bottom-up approach and evaluates the potential for the dust to deposit to Lake Tahoe where it can affect water clarity. Previous studies of estimates of quantities of atmospheric deposition of fine sediment particles ("FSP", <16 µm in diameter) to the lake were questioned due to low confidence in the results and insufficient data. A bottom-up approach that integrates measured road dust emission factors, five years of meteorological data, a traffic demand model and GIS analysis was used to estimate the near field deposition of airborne particulate matter <16 µm, and assess the relationship between trip location and the potential magnitude of this source of atmospheric deposition to the lake. Approximately ~20 Mg year(-1) of PM10 and ~36 Mg year(-1) Total Suspended Particulate (TSP) from roadway emissions of dust are estimated to reach the lake. We estimate that the atmospheric dry deposition of particles to the lake attributable to vehicle travel on paved roads is approximately 0.6% of the Total Maximum Daily Loadings (TMDL) of FSP that the lake can receive and still meet water quality standards.

Motor vehicle contributions to ambient PM10 and PM2.5 at selected urban areas in the USA.

A source apportionment study was carried out to estimate the contribution of motor vehicles to ambient particulate matter (PM) in selected urban areas in the USA. Measurements were performed at seven locations during the period September 7, 2000 through March 9, 2001. Measurements included integrated PM(2.5) and PM(10) concentrations and polycyclic aromatic hydrocarbons (PAHs). Ambient PM(2.5) and PM(10) were apportioned to their local sources using the chemical mass balance (CMB) receptor model and compared with results obtained using scanning electron microscopy (SEM). Results indicate that PM(2.5) components were mainly from combustion sources, including motor vehicles, and secondary species (nitrates and sulfates). PM(10) consisted mainly of geological material, in addition to emissions from combustion sources. The fractional contributions of motor vehicles to ambient PM were estimated to be in the range from 20 to 76% and from 35 to 92% for PM(2.5) and PM(10), respectively.

Measurements of Dioxin and Furan Emission Factors from Heavy-Duty Diesel Vehicles.

This note describes the results of a study of the on-road emissions of dioxins and furans from mobile sources. This work was performed in response to the U.S. Environmental Protection Agency's (EPA) draft document on dioxin reassessment, which used data from sources outside the United States to estimate an emission factor of 0.8 ng-TEQ/veh-mi for the U.S. fleet. The primary objective of this work was to measure on-road chlorinated dioxin and furan emission factors from in-use vehicles operating in the United States, with emphasis on heavy-duty vehicles. The experimental approach was to measure emissions in the Fort McHenry Tunnel in Baltimore, MD. All air entering and leaving the tunnel was sampled for concentrations of dioxins and furans (during 10 24-h sampling periods). The difference between the mass of material entering and the mass of material leaving the tunnel was taken to be the amount produced by the vehicles in transit. These measurements were combined with information on vehicle counts (obtained through videotapes) and tunnel length to determine average emission factors. For the limited range of vehicle operating conditions present in the tunnel experiment, the average heavy-duty diesel emission factor determined in this study was 0.28 ± 0.13 ng-TEQ/veh-mi, a factor of 3 lower than the EPA estimate.

The Impact of California Phase 2 Reformulated Gasoline on Real-World Vehicle Emissions.

In mid-1996, California implemented Phase 2 Reformulated Gasoline (RFG). The new fuel was designed to further decrease emissions of hydrocarbons (HCs), oxides of nitrogen (NOx), carbon monoxide (CO), sulfur dioxide (SO2), and other toxic species. In addition, it was formulated to reduce the ozone-forming potential of the HCs emitted by vehicles. Previous studies have observed that emissions from on-road vehicles can differ significantly from those predicted by mobile source emissions models, and so it is important to quantify the change in emissions in a real-world setting. In October 1995, prior to the introduction of California Phase 2 RFG, the Desert Research Institute (DRI) performed a study of vehicle emissions in Los Angeles' Sepulveda Tunnel. This study provided a baseline against which the results of a second experiment, conducted in July 1996, could be compared to evaluate the impact of California Phase 2 RFG on emissions from real-world vehicles. Compared with the 1995 experiment, CO and NOx emissions exhibited statistically significant decreases, while the decrease in non-methane hydrocarbon emissions was not statistically significant. Changes in the speciated HC emissions were evaluated. The benzene emission rate decreased by 27% and the overall emission rate of aromatic compounds decreased by 22% comparing the runs with similar speeds. Emissions of alkenes were virtually unchanged; however, emissions of combustion related unsaturates (e.g., acetylene, ethene) increased, while heavier alkenes decreased. The emission rate of methyl tertiary butyl ether (MTBE) exhibited a larger increase. Overall changes in the ozone-forming potential of the emissions were not significantly different, with the increased contributions to reactivity from paraffins, ole-fins, and MTBE being offset by a large decrease in reactivity due to aromatics.