This study focuses on the relationship between hydrological and nutrient conditions in seawater surrounded by Dongsha Atoll. Dongsha Atoll is located in the northern South China Sea (NSCS), the water properties should be in coherence with the NSCS water masses. However, due to the semi-enclosed topography the water inside Dongsha Atoll is largely affected by local insolation and rainfall. Significant relationships between SiO2 or PO43- and salinity indicate that rainfall could be a major source of these nutrients. Insignificant relationship between N+N and salinity indicates that rainfall and nitrogen fixation both might affect the distribution of N+N. Temporal variations of temperature and chlorophyll a were alike, except for which occurred in July, 2011. It was probably caused by photo inhibition on phytoplankton growth. The inventory of chlorophyll a was positively correlated with both N+N and SiO2 but not with of PO43-, indicating that phytoplankton growth in Dongsha Atoll was mainly affected by N+N and SiO2. Phytoplankton growth maybe limited by N+N but not by SiO2, as the concentration of SiO2 was mostly beyond the limitation concentration for phytoplankton. According to close relationships between chlorophyll a and TSM, POC and PN, the particulate matter maybe mainly derived from biological origins. The inventory of chlorophyll a was positively correlated with both dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), manifesting the importance of biological origins for DOC and DON concentration. The ratios of DOC/DON, DON/DOP and DOC/DOP within the atoll were in ranges of 7.34-303 (mean: 30.4), 3.00-142 (mean: 22.7) and 104-2546 (mean: 421), respectively. The ratios are higher than those values in NSCS and East China Sea, implying the excretion of carbon-enriched DOM by phytoplankton. The concentration of chlorophyll a, DOC and POC were higher in the Small Lagoon than in the Atoll Lagoon, implying a relatively high productivity in the Small Lagoon. The fluxes of carbonate in the atoll was more than 30 times of the flux in the NSCS, due to its unique characteristics in the coral reef habitat. The organic matter of settling particulates was mainly derived from biological sources. The metal of enrichment factor of settling particulates reveals that Fe and Al are mainly derived from crustal sources, while Cu, Zn and Pb are likely influenced by anthropogenic sources.

This study reports the first sediment trap mooring results obtained under the SIBEX program (South China Sea Integrated Biogeochemical Experiments). Two strings of sediment traps were deployed respectively at M1 located to the southwest of Taiwan, and M2 in the northern basin of the South China Sea (SCS). Box cores were also taken at several sites to the south of M2. The main purposes are to measure settling particulate fluxes at various depths for the studies of temporal and spatial variations of the particulate flux and 210Pb activity. The box cores were used to determine the sedimentation rates. These are to enhance our understanding of the characteristics of the particulate distribution and the roles the particulate matter plays in the biogeochemical processes in the SCS. Particulate fluxes measured from different depths at M1 and M2 generally increase with depth. In temporal variation, M1 has higher amplitudes than M2, with highest amplitudes at 948 m where highest flux (2025 mg/m2/d) was observed. The particulate flux at 948 m has higher values than at 248 m, probably due to lateral transport. At M2, the particulate flux at 240 m has higher values with greater amplitudes than at greater depths, i.e. 1240 m, 2240 m and 3240 m, where their particulate fluxes show a synchronous trend with small amplitudes in temporal variation. The time-averaged particulate flux for each trap ranges from 199 to 554 mg/m2/d, consistently higher than previous observations (76~104 mg/m2/d). However, our values are comparable to the mean particulate flux (280 mg/m2/d) estimated from terrigenous inputs. The apparent changes in particulate flux in the SCS over the past ten years warrants further investigations. The temporal variations of Pb-210 show a synchronous trend and a rapid increase with depth as observed at M1 and M2. This rapid increase of Pb-210 with depth reflects effective scavenging by sinking particulates although particulate concentrations are low. The loss on ignition (L.O.I.) at M1 and M2 was inversely correlated with Pb-210, indicating that Pb-210 was expelled from biogenic particulates or organic matter. The particulate fluxes around 240 m at M1 and M2 were generally positively correlated with the L.O.I., suggesting that the high particulate fluxes are probably contributed by biogenic particulates or organic matter. The sedimentation rates as determined from excess Pb-210 profiles range from 9.01~23.13 cm/100yr. These rapid sedimentation rates reflect the effect of mixing and additional sediments accumulated through lateral transport. The surface layers of these cores were subject to perturbation and mixing, based on the penetration depths of the excess Pb-210. The Pb-210 flux estimated from the inventory of excess Pb-210 in the sediments is much greater than that observed from the traps, suggesting that additional Pb-210 has been accumulated via lateral transport and slumping of nearby surface sediments. Based on the mean particulate flux observed, one may roughly estimate the corresponding sedimentation rate of about 10 cm/ka, which is an order of magnitude lower than those determined by the excess Pb-210 method. Because the upper layers of the sediments have been strongly disturbed and mixed with the additional sediments accumulated through lateral transport, the sedimentation rates as determined by the excess Pb-210 method are probably over-estimated by a factor of 10 to 20.

This thesis seeks to assess the exposure of children in outdoor play areas of early childhood centres in Auckland City to traffic-related PM10 pollution. An estimated 400 premature deaths occur each year in New Zealand due to motor vehicle emissions. In addition to premature deaths, acute and chronic health effects including asthma, chronic obstructive pulmonary disease (COPD), heart disease and bronchitis, as well as increased hospitalisations and restricted activity days (sick days) are also associated with vehicle emissions. Epidemiological studies have shown that respiratory diseases such as asthma can be exacerbated by increases in the concentration of particulates of less than 10 microns in diameter (PM10) from motor vehicle emissions. Significant positive associations have been found between proximity to heavily travelled roads and increased childhood respiratory disease symptoms including hospitalisations for childhood asthma. In spite of this evidence, many early childhood centres in Auckland are located adjacent to busy roads. Children at these early childhood centres spend much of their time playing in the outdoor areas of these centres with the potential for particulates from motor vehicle emissions to exacerbate symptoms in those children already suffering from respiratory disease and asthma. Very little research has been carried out either in New Zealand or internationally on the air quality of outdoor play areas of early childhood centres in relation to motor vehicle emissions and childhood respiratory disease and asthma. The extent of monitoring is also limited and the amount of exposure data available in New Zealand relatively sparse, particularly in comparison with Europe. Levels of traffic-related PM10 in the outdoor play areas of early childhood centres were measured in centres located adjacent to busy roads and in centres away from a quiet road or adjacent to a very quiet road for comparison. Two of five early childhood centres located alongside busy roads had PM10 levels that exceeded the World Health Organization (WHO) guideline value. While PM10 levels monitored at the other three centres located alongside busy roads did not exceed the WHO guideline value, results were often only marginally within this guideline value. In contrast, PM10 levels monitored at two centres located away from a quiet road and one centre located adjacent to a very quiet road were well within the WHO guideline value. This pilot study provides preliminary evidence that children attending early childhood centres located alongside busy roads have greater exposure to traffic-related PM10 pollution than those attending early childhood centres located away from a quiet road or adjacent to a very quiet road. If the link between PM10 exposure and health effects is causal, as suggested by epidemiological studies, then children attending early childhood centres proximal to busy roads are at a greater risk of respiratory illness than children attending early childhood centres adjacent to quiet roads. Further work is required to confirm the findings in this small sample of air quality around early childhood centres in a larger sample, and possibly to undertake an epidemiological study to confirm the link to health effects. Drawing on the precautionary principle, prudent territorial local authorities should be encouraged to introduce regulations ensuring that any new early childhood centres are located at a specified distance from major roads, and that information for parents, ongoing PM10 monitoring and processes for issuing PM10 advisories when limits are exceeded are available in existing early childhood centres that are adjacent to busy roads.

No description available.

NSF/ANSI 53 lead-certified point-of-use filters (POUs) have been distributed to consumers in many cities facing water lead crises, including Washington D.C., Flint, MI, Newark, NJ, and University Park, IL. It is expected that these filters would reduce water lead to levels that are safe for consumption as residents wait for municipalities to provide more permanent solutions (e.g., corrosion control, lead service line replacement). These filters are certified by the National Sanitation Foundation (NSF) after meeting the challenges of treating two lab synthesized waters with 150 μg/L of soluble and particulate lead. In Flint, as in Washington, there were initial concerns that the filters would not be effective when exposed to lead levels far above the NSF/ANSI 53 150 μg/L Pb level used for certification. However, the EPA conducted a 2016 study in Flint, MI, with over 240 homes with lead up to 4080 μg/L, revealing that all POUs reduced lead levels below 1 μg/L. Newark, NJ, in response to Lead and Copper Rule (LCR) violations, distributed over 40,000 NSF/ANSI 53 lead-certified pitcher and faucet POUs to protect consumers from high water lead levels. In the summer of 2019, preliminary tests in some homes with the highest lead in water concentrations revealed that 2 of 3 POUs used in Newark had effluent lead levels above 15 μg/L. The publication of these results caused citywide angst, distrust, and EPA mandated a switch to bottled water. However, a later and more extensive study revealed that 97.5% of homes (n=198) with properly used filters had effluent lead levels below 10 μg/L. As a result, the EPA approved Newark's request to discontinue bottled water distribution and only provide POUs to residents. Nevertheless, the experience indicated that it is vital to understand the limitations of POUs. This dissertation comprises three manuscripts that examine the efficacy of POUs under laboratory and field conditions. The first manuscript sought to provide perspective into potential causes of the filter failures observed in the field. We conducted an extensive laboratory investigation that examined the performance of 10 pitcher and faucet POU brands under extreme conditions (e.g., up to 200% of rated capacity, influent lead levels ≈ 1000 μg/L). Our tests confirmed successful performance documented in some field testing and replicated underperformance observed in others. In this investigation, we observed structural failures due to poor manufacturing (i.e., leaking units, a filter with a large hole in the media) and performance failures (filtered water >10 μg/L Pb). Some of the performance failures occurred when we tested particulate lead waters, which we created, proving to be very difficult to treat relative to those used for NSF/ANSI testing. While the POUs almost always reduce consumer lead exposure, even when operated beyond their rated capacity, this study highlights instances where treated water could far exceed 10 μg/L lead. High particulate iron (Fe) and manganese (Mn) concentrations often co-occur with high lead in many low-income, rural communities with small community water systems (CWS) or in homes with private wells. These communities are more likely to depend on POUs for protection from waterborne lead as they typically do not have the funds to maintain and upgrade infrastructure, improve corrosion control, or replace service lines. Waters with high levels of Fe and Mn could potentially impact the performance of the POU lead filters. However, such problems would not be detected in NSF/ANSI certification testing because these constituents are not included within the test water. The second manuscript validated anecdotal reports of premature POU failure due to clogging in rural communities with high iron concentrations in their water. POU pitcher filters were tested with waters containing high lead and iron up to 100% of their rated capacity, or until they clogged as defined by a 75% reduction in initial flowrate. Iron levels above the 0.3 mg/L Secondary Maximum Contaminant Level (SMCL) resulted in rapid clogging, markedly increasing treatment costs, and decreasing consumer satisfaction. At 0.3 mg/L Fe, half of the 6 POU filters tested were clogged at between 38-68% of their rated capacity. When considering the cost of using POU filters vs. purchasing bottled water, the POU devices were often more cost-effective at iron levels at or below 0.3 mg/L. However, as iron concentrations increased, bottled water often became cost-effective depending on the circumstance. The presence of iron did not have an adverse effect on lead removal but significantly affected the cost and reduced flow rates in treating water. The third manuscript presents a two-phase field study that sought to monitor the long-term filter performance in residential homes in New Orleans and Enterprise, LA. Previous field studies have captured POU removal efficiencies in single event (grab) samples; however, this study quantified filter performance for all the water treated up to POU practical capacity (i.e., filter life) based on consumer judgment regarding acceptable flow rate. The first phase was a rigorously controlled study that tested the POUs (100-gal capacity) at up to 200% of their rated capacity in two New Orleans unoccupied homes. Historically, the first home had consistently high lead levels (10-25 μg/L) even after flushing for > 8 min. Duplicate POUs treated that water to below 5 μg/L at up to 100% capacity, with only two exceptional samples with 12 μg/L Pb in 10-gallon batches of the treated water. The second home had a disturbed lead service line (LSL), resulting in varying concentrations of influent particulate lead ranging from 9-3000 μg/L. The duplicate POUs had difficulty producing water lead levels <10 μg/L before reaching filter capacity, with eight exceedances prior to 100% capacity. This work demonstrated that flushing alone for extended periods (>8 minutes) is not guaranteed to reduce lead levels in all homes with LSLs and highlights some limitations of POU filters in treating water with high levels of particulate lead. The second phase of the field study monitored POU faucet filter performance in the homes of 21 residents in New Orleans (8) and Enterprise (13), LA. New Orleans is a large urban area with low to moderate water lead levels with many partial LSL replacements. Enterprise (population <300) is a rural, low-income community with an unincorporated water system with moderate to high water lead, iron, and manganese levels. Overall, the POUs consistently reduced lead to <1 μg/L, iron <171 μg/L, and manganese <180 μg/L. Enterprise's high influent concentrations of iron significantly impacted filter capacity due to reduced flow and clogging. Enterprise homes saw an average 62% flowrate reduction, and most of the homes did not reach 50% of the filter's rated capacity before consumers decided the filters were clogged. Most New Orleans residents did not experience clogging, and the homes that did saw only a 16% flow rate reduction. Overall, the New Orleans POUs were 2.3X faster in treating water by the study's end than Enterprise. There was no simple correlation between average iron concentration and days of filter life amongst residents in Enterprise as would be expected given variations in the volume of water used daily and consumer subjectivity in deciding when to end the study due to clogging. However, residents in Enterprise and similar communities would likely need to purchase 2-4 times as many filter cartridges due to clogging when compared to cities like New Orleans with lower iron concentrations. This study shows how POUs have promise for the removal of Pb and Fe in residential homes, but clogging has emerged as an important practical limitation to widespread successful POU deployment. This dissertation highlighted the multifaceted nature of the question: "How well do POU filters work and under what conditions?" Overall, the POUs have shown their ability to reduce water lead levels effectively <5 μg/L, with a few exceptions primarily attributed to particulate lead and manufacturing quality control issues. However, when treating waters with high levels of iron and other contaminants, POU clogging can cause consumer dissatisfaction and make purchasing bottled water a more favorable solution than POU filters. / Doctor of Philosophy / Lead-certified point-of-use filters (POUs) have been distributed to consumers in many cities facing water lead crises, including Washington D.C., Flint, MI, Newark, NJ, and University Park, IL. In Flint, as in Washington, there were initial concerns that the filters would not be effective when exposed to lead levels far above the 150 μg/L lead concentration used for certification. The EPA conducted a 2016 study in Flint, MI (>400 homes) that showed all POUs successfully reduced lead levels below 1 μg/L. Newark, NJ, distributed over 40,000 lead-certified pitcher and faucet POUs to protect consumers from high water lead levels. In the summer of 2019, preliminary tests in some homes with the most challenging particulate lead in water concentrations revealed that 2 of 3 POUs used in Newark had effluent lead levels above 15 μg/L. The publication of these results caused citywide angst, distrust and an EPA mandated a switch to bottled water. A few weeks later, a more extensive study revealed that over 97.5% of homes had filters that effectively reduced lead. Millions of dollars invested in the POU filters in Newark were wasted as many residents discontinued use despite positive counter-messaging of overall POU performance. Newark's filter experience illuminated how vital it is to understand the limitations of lead-certified filters as our reliance on these POUs for lead remediation increases. This dissertation comprises three manuscripts that examine the efficacy of lead-certified POUs under laboratory and field conditions. The first manuscript provides some perspective into potential causes of the filter failures observed in the field. We conducted an extensive laboratory investigation that examined the performance of 10 pitcher and faucet POU brands under extreme conditions (i.e., used well past capacity and with high lead concentrations). Our tests confirmed successful performance documented in some field testing and replicated underperformance observed in others. In addition, this investigation observed structural failures due to poor manufacturing and performance failures (> 10 μg/L Pb) when testing particulate lead waters. While the POUs almost always reduce consumer lead exposure, even when operated beyond their rated capacity, this study highlights instances where filtered water could far exceed 10 μg/L lead. The second manuscript validated anecdotal reports of premature POU failure due to clogging in rural communities with high iron concentrations in their water. Particulate iron (Fe) and manganese (Mn) often co-occur with high lead concentrations and cause most discoloration seen in drinking water (i.e., orange and black water). Low-income rural communities with small water systems are more likely to depend on POUs to protect them from waterborne lead as they typically do not have the funds to maintain and upgrade infrastructure, improve corrosion control, or replace service lines. In this study, POU pitcher filters were tested with waters containing high lead and iron up to 100% of their rated capacity, or until they clogged as defined by a 75% reduction in initial flowrate. The presence of iron did not have an adverse effect on lead removal. However, iron significantly affected POU water treatment costs and reduced flow rates. Iron levels above the 0.3 mg/L Secondary Maximum Contaminant Level (SMCL) resulted in rapid clogging prior to reaching rated capacity, resulting in increased treatment costs and decreased consumer satisfaction and convenience. When considering the cost of using POU filters vs. purchasing bottled water, the POU devices were often more cost-effective at iron levels 0.3 mg/L. However, as iron concentrations increased, bottled water often became cost-effective depending on the circumstance. The third manuscript presents a two-phase field study that sought to monitor the long-term filter performance in residential homes in New Orleans and Enterprise, LA. Previous field studies have captured POU removal efficiencies in single event (grab) samples. However, this study captures filter performance for all the water treated up to POU practical capacity (i.e., filter life) based on consumer judgment regarding acceptable flow rate. The first phase was a controlled rig study that tested the POUs filters (100-gal capacity) up to 200% capacity in two New Orleans unoccupied homes. Historically, the first home had consistently high lead levels (10-25 μg/L) even after flushing for > 8 min. Throughout the 20-day study, the duplicate POUs in this home supplied filtered water with <5 μg/L Pb up to 100% capacity, with only two exceptions (each sample had 12 μg/L Pb). The second home had a disturbed lead service line (LSL), resulting in varying concentrations of influent particulate lead ranging from 9-3000 μg/L. The duplicate POUs in this home did not consistently produce filtered water with <10 μg/L Pb, as they had eight exceedances before reaching 100% capacity. This work demonstrated that flushing the tap is not guaranteed to reduce lead levels in all homes with LSLs, even when flushing >8 minutes. It also highlighted some limitations of POU filters in treating water with high levels of particulate lead. The second phase of the field study monitored POU faucet filter performance in the homes of 21 residents in New Orleans (8) and Enterprise (13), LA. New Orleans is a large urban area with low to moderate water lead levels with many partial LSL replacements. Enterprise (population <300) is a rural, low-income community with an unincorporated water system with moderate to high water lead, iron, and manganese levels. Overall, the POUs consistently reduced lead to <1 μg/L, iron <171 μg/L, and manganese <180 μg/L. Enterprise's high influent concentrations of iron significantly impacted filter capacity due to reduced flow and clogging. Most of the homes in Enterprise did not reach 50% of the filter's rated capacity before consumers decided the filters were clogged. The New Orleans residents did not experience POU clogging, and many filters reached capacity. The New Orleans filters were also 2.3X faster in treating water by the study's end than Enterprise. There was no statistical correlation between iron concentration and filter life; however, residents in Enterprise and similar communities would likely need to purchase 2-4 times as many filter cartridges due to clogging compared to cities like New Orleans with lower iron concentrations. This study shows how POUs have promise for the removal of Pb and Fe in residential homes. However, clogging has emerged as an important practical limitation to successful POU deployment. This dissertation highlighted the multifaceted nature of the question: "How well do POU filters work and under what conditions?" Overall, the POUs have shown their ability to reduce water lead levels effectively <5 μg/L, with a few exceptions primarily attributed to particulate lead and manufacturing quality control issues. However, when treating waters with high levels of iron and other contaminants, POU clogging can cause consumer dissatisfaction and make purchasing bottled water a more favorable solution than POU filters.

No / This study presents the data elements to develop a new processing route to transform elastomeric waste residue (particulates) into acoustic and thermal insulation materials that can compete with commercial products. The approach is to bind these grain and fibre particulates with a foaming polyurethane or a similar polymer, the chemistry of which can be manipulated to control the structure stiffness and the evolution of the foaming gas into open or closed cells. Here the study uses two examples of such residues, tyre and carpet shreds both composed of fibres trapping grains of either rubber or PVC. Compounds were made from these systems with different PU binders and the structural properties (density, porosity, air flow resistivity, tortuosity and stiffness) and performance properties (sound absorption, sound transmission, impact sound insulation and thermal conductivity) were measured as a function of binder loading and chemistry. The data obtained show clearly that performance can be tailored by tailoring structural properties resulting with materials that match or even outperform commercial products. The data set obtained here can be usefully exploited with available acoustic and thermal insulation materials model to take the approach further and extended to other waste systems.

Master of Science / Department of Mechanical and Nuclear Engineering / Mohammad H. Hosni / Byron W. Jones / Gas turbine engine oil is contaminating the bleed air of an aircraft with enough frequency and intensity that health concerns are of public interest. While previous work measured micro particles and used only a simulator, this work mainly consists of measurements in the nanoparticle and ultrafine range using both the simulator and two different gas turbine engines. No previous research has been conducted using working jet engines to simulate a bleed air system and characterize the oil particulate contamination. Oil was injected into a bleed air simulator and an Allison 250 CC18 turbine engine in order to observe the particle size distributions resulting from thermal degradation and was measured with three particle sizing counters and an FTIR. The aerosol size distributions are given for various temperature and pressure ranges consistent with the process conditions associated with the bleed air in a commercial aircraft. Particle sizes of approximately 80nm to 100nm were observed at temperatures over 200°C while particles similar to injection distributions and smaller than measureable size were observed at lower power settings. Temperature is thought to be the controlling factor affecting particle size above 200°C while blade shear is likely the dominant factor for lower temperatures. The bleed air simulator produced results similar to the gas turbine engine results at higher temperatures, but did not replicate the size characteristics at lower temperatures. The observed particles are ultrafine and situated in the size range that may impact health safety more than larger particles.

No description available.

No description available.

Nenhuma / A poluição urbana é um sério problema ambiental que vem se agravando nos países em desenvolvimento. No Brasil, as concentrações de poluentes atmosféricos têm crescido rapidamente nas principais regiões urbanas durante as últimas décadas. Esta expansão tem ocorrido principalmente devido ao crescente número de veículos automotivos em circulação. As emissões causadas por veículos contêm diversas substâncias tóxicas que podem produzir efeitos negativos à saúde, incluindo problemas respiratórios e cardiovasculares. Um dos principais poluentes atmosféricos originados dessas emissões é o Material Particulado (MP), classificado em MP2,5 (diâmetro aerodinâmico < 2,5 &#956;m) e MP10 (diâmetro aerodinâmico < 10 &#956;m). Os efeitos do MP sobre a saúde humana dependem de sua maior ou menor capacidade de penetração no sistema respiratório. O município de Belo Horizonte (BH) possui cerca de 2,4 milhões de habitantes e uma frota de mais de um milhão de veículos. Essa situação, aliada às características poluentes dos combustíveis veiculares e às condições do trânsito na região, cria um cenário preocupante em relação à qualidade do ar. Portanto, avaliar a influência das emissões veiculares de MP seria fundamental para o levantamento de informações que possam respaldar proposições para a melhoria da qualidade do ar no município. Diversos estudos que avaliam a qualidade do ar utilizam modelos numéricos associados a medições ambientais. O modelo CAL3QHCR, desenvolvido pelo Departamento de Transportes da Califórnia é um modelo numérico para avaliação da dispersão de poluentes atmosféricos veiculares. Este modelo permite estimar as concentrações de MP nas proximidades das vias de tráfego com base em informações sobre as condições meteorológicas, o tráfego de veículos, as emissões veiculares e a sinalização. Neste trabalho, o modelo CAL3QHCR foi utilizado para avaliar a contribuição das emissões de MP de origem veicular na qualidade do ar de uma microrregião localizada no centro de BH. Os dados meteorológicos (direção e velocidade do vento, temperatura e classe de estabilidade atmosférica); de tráfego de veículos; de emissão veicular; e de sinalização das vias de interesse foram coletados e tratados de acordo com o formato exigido pelo modelo CAL3QHCR. Devido à inexistência de fatores de emissão veicular de MP para a região estudada, utilizaram-se os fatores estabelecidos para a região metropolitana de São Paulo. Os resultados de concentração obtidos nas simulações foram comparados com dados experimentais de concentração de MP2,5 e MP10, obtidos a partir da amostragem desses poluentes em uma estação de monitoramento da qualidade do ar localizada na microrregião estudada. Para todos os cenários considerados, os valores de concentração previstos pelo modelo apresentaram-se menores que os observados. O estudo de análise de sensibilidade revelou que o parâmetro de entrada que apresenta maior influência nos resultados das concentrações é o fator de emissão veicular. Uma das medidas que poderia contribuir para a obtenção de dados mais reais desse fator seria a implantação de um programa de inspeção veicular ambiental no município de Belo Horizonte. / Urban pollution is a severe environmental problem that has become increasingly worse in developing countries. In Brazil, during recent decades, the concentrations of atmospheric pollutants have risen drastically, especially in the major urban regions. This expansion occurred mainly due to the growing number of automobiles in circulation. Vehicular exhaust emissions contain several toxic substances that may bring health risks, including respiratory and cardiovascular complications. One of the main atmospheric pollutants coming from these emissions is the Particulate Matter (PM), which is classified as PM2.5 (aerodynamic diameter below 2.5 &#956;m) and PM10 (aerodynamic diameter below 10 &#956;m). The effects of PM on human health depend on its lesser or greater capacity to penetrate into the pulmonary system. Belo Horizonte city comprises roughly 2.4 million citizens and over 1 million motor vehicles in circulation. This, together with the pollutant potential of vehicular fuel and traffic conditions in the area, creates a distressing scenario concerning air quality. Therefore, assessing the influence of PM from vehicular exhausts is critical to collect information which could be used to suggest ways to improve air quality in the region. Several air quality researchers use numerical simulation combined with environmental measurements. The CAL3QHCR model has been developed by the California Department of Transportation and it is a numerical model to evaluate the dispersion of atmospheric pollution from vehicles. This model allows estimating PM concentrations in the vicinity of traffic lanes based on data from meteorological conditions, roadway traffic, vehicular emissions, and signalized intersections. In this study, the CAL3QHCR model was used to assess the contribution of PM from vehicular exhausts to the air quality of a specific site in downtown Belo Horizonte. The meteorological, traffic, signalization, and vehicular emissions data were collected and analyzed according to the CAL3QHCR models requirements. Due to the absence of PM emission factors for Belo Horizonte region, this study has opted to use previously established factors for vehicles as measured in the São Paulo metropolitan area. Concentration results obtained through simulations were compared to the experimental data for the concentrations of PM2.5 and PM10 which consisted of collected samples from a monitoring station for air quality located in the micro-region selected for this research. For all the scenarios taken into consideration, the concentration values predicted by the model were lower than the experimental concentrations. The sensitivity analysis showed that the vehicular emission factor influenced the concentration results more than the other input parameters. One of the measures that could contribute to obtaining more realistic data about this factor would be the establishment of an environmental program for vehicle inspection.