Urban Roadside Environments Research Articles

Consistent traffic noise impacts few fitness-related traits in a field cricket

BackgroundAnthropogenic habitat change is occurring rapidly, and organisms can respond through within-generation responses that improve the match between their phenotype and the novel conditions they encounter. But, plastic responses can be adaptive or maladaptive and are most likely to be adaptive only when contemporary conditions reasonably mimic something experienced historically to which a response has already evolved. Noise pollution is a ubiquitous anthropogenic stressor that accompanies expanding urbanization. We tested whether the amplitude of traffic noise influences a suite of fitness-related traits (e.g. survival, life history, reproductive investment, immunity) and whether that depends on the life stage at which the noise is experienced (juvenile or adult). Our treatments mimic the conditions experienced by animals living in urban roadside environments with variable vehicle types, but continuous movement of traffic. We used the Pacific field cricket, an acoustically communicating insect that was previously shown to experience some negative behavioral and life history responses to very loud, variable traffic noise, as a model system.ResultsAfter exposing crickets to one of four traffic noise levels (silence, 50dBA, 60dBA, and 70dBA which are commonly experienced in their natural environment) during development, at adulthood, or both, we measured a comprehensive suite of fifteen fitness-related traits. We found that survival to adulthood was lower under some noise treatments than under silence, and that the number of live offspring hatched depended on the interaction between a female’s juvenile and adult exposure to traffic noise. Both of these suggest that our noise treatments were indeed a stressor. However, we found no evidence of negative or positive fitness effects of noise on the other thirteen measured traits.ConclusionsOur results suggest that, in contrast to previous work with loud, variable traffic noise, when noise exposure is relatively constant, plasticity may be sufficient to buffer many negative fitness effects and/or animals may be able to habituate to these conditions, regardless of amplitude. Our work highlights the importance of understanding how the particular characteristics of noise experienced by animals influence their biological responses and provides insight into how commensal animals thrive in human-dominated habitats.

Assessment of Sources and Pollution Level of Airborne Toxic Metals through Foliar Dust in an Urban Roadside Environment

Concentrations of 19 elements (Al, Fe, Ca, K, Mg, Na, S, Ti, Ba, Sr, Zn, V, Cu, Mn, Cr, Pb, Ni, Co, and Cd) in foliar dust samples were determined from 6 different roadside locations of Bilaspur city (Chhattisgarh), India. Principal component analysis (PCA) indicated the significance of vehicular activities followed by sources such as firework events and other industrial/regional/transboundary sources in foliar dust in the area of study. Risk assessment of metal levels in foliar dust was performed using several indices based on the data collected from different sites. The geo-accumulation index (Igeo) analysis indicated foliar dust was moderately and extremely polluted with S and Cd, respectively, while practically unpolluted with most other elements (Al, Fe, Ca, K, Mg, Na, Ti, Ba, Sr, Zn, V, Cu, Mn, Cr, Pb, Ni, and Co). The values of pollution (IPOLL) index and contamination factor (CF) of Cd indicated a high pollution level. Comparable results were found for the ecological risk (Eri) of Cd (above 320) with a very high Eri at all sites. In addition, the overall Eri index (RI) of foliar dust at all sites was very high due to a greater Cd contribution.

Composition of Size-Segregated Atmospheric Aerosol Collected at an Urban Roadside Environment in Jeju Area

Composition of Size-Segregated Atmospheric Aerosol Collected at an Urban Roadside Environment in Jeju Area

Efficient Removal of Ultrafine Particles from Diesel Exhaust by Selected Tree Species: Implications for Roadside Planting for Improving the Quality of Urban Air.

Human exposure to airborne ultrafine (≪1 μm) particulate pollution may pose substantial hazards to human health, particularly in urban roadside environments where very large numbers of people are frequently exposed to vehicle-derived ultrafine particles (UFPs). For mitigation purposes, it is timely and important to quantify the deposition of traffic-derived UFPs onto leaves of selected plant species, with particularly efficient particle capture (high deposition velocity), which can be installed curbside, proximal to the emitting vehicular sources. Here, we quantify the size-resolved capture efficiency of UFPs from diesel vehicle exhaust by nine temperate-zone plant species, in wind tunnel experiments. The results show that silver birch (79% UFP removal), yew (71%), and elder (70.5%) have very high capabilities for capture of airborne UFPs. Metal concentrations and metal enrichment ratios in leaf leachates were also highest for the postexposure silver birch leaves; scanning electron microscopy showed that UFPs were concentrated along the hairs of these leaves. For all but two species, magnetic measurements demonstrated substantial increases in the concentration of magnetic particles deposited on the leaves after exposure to the exhaust particulates. Together, these new data show that leaf-deposition of UFPs is chiefly responsible for the substantial reductions in particle numbers measured downwind of the vegetation. It is critical to recognize that the deposition velocity of airborne particulate matter (PM) to leaves is species-specific and often substantially higher (∼10 to 50 times higher) than the "standard" Vd values (e.g., 0.1-0.64 cm s-1 for PM2.5) used in most modeling studies. The use of such low Vd values in models results in a major under-estimation of PM removal by roadside vegetation and thus misrepresents the efficacy of selected vegetation species in the substantial (≫20%) removal of PM. Given the potential hazard to health posed by UFPs and the removal efficiencies shown here (and by previous roadside measurements), roadside planting (maintained at or below head height) of selected species at PM "hotspots" can contribute substantially and quickly to improve in urban air quality and reductions in human exposure. These findings can contribute to the development and implementation of mitigation policies of traffic-derived PM on an international scale.

The traffic signature on the vertical PM profile: Environmental and health risks within an urban roadside environment

In an attempt to investigate the traffic-impacted vertical aerosols profile and its relationship with potential carcinogenicity and/or mutagenicity, samples of different sized airborne particles were collected in parallel at the 1st and 5th floor of a 19 m high building located next to one of the busiest roads of Athens. The maximum daily concentrations were 65.9, 42.5 and 38.5 μg/m3, for PM10, PM2.5 and PM1, respectively. The vertical concentration ratio decreased with increasing height verifying the role of the characteristics of the area (1st/5th floor: 1.21, 1.13, 1.09 for PM10, PM2.5 and PM1, respectively). Chemically, strengthening the previous hypothesis, the collected particles were mainly carbonaceous (68%–93%) with the maximum budget of the polyaromatic hydrocarbons being recorded near the surface (1st/5th floor: 1.84, 1.07, 1.15 for PM10, PM2.5 and PM1, respectively). The detected PM-bound PAHs along with the elements as well as the carbonaceous and ionic constituents were used in a source apportionment study. Exhaust and non-exhaust emissions, a mixed source of biomass burning and high temperature combustion processes (natural gas, gasoline/diesel engines), sea salt, secondary and soil particles were identified as the major contributing sources to the PM pollution of the investigated area. With respect to the health hazards, the calculation of the Benzo[a]Pyrene toxicity equivalency factors underlined the importance of the height of residence in buildings for the level of the exposure (1st/5th floor: B[a]PTEQ: 1.82, 1.12, 1.10, B[a]PMEQ: 1.85, 1.13, 1.09 for PM10, PM2.5 and PM1, respectively). Finally, despite its verified significance as a surrogate compound for the mixture of the hydrocarbons (its contribution up to 72%, 79% on the level of the 1st and 5th floor, respectively), the importance of the incorporation of PAH species in addition to B[a]P when assessing PAH toxicity was clearly documented.

Evaluation of traffic exhaust contributions to ambient carbonaceous submicron particulate matter in an urban roadside environment in Hong Kong

Abstract. Road traffic has significant impacts on air quality particularly in densely urbanized and populated areas where vehicle emissions are a major local source of ambient particulate matter. Engine type (i.e., fuel use) significantly impacts the chemical characteristics of tailpipe emission, and thus the distribution of engine types in traffic impacts measured ambient concentrations. This study provides an estimation of the contribution of vehicles powered by different fuels (gasoline, diesel, LPG) to carbonaceous submicron aerosol mass (PM1) based on ambient aerosol mass spectrometer (AMS) and elemental carbon (EC) measurements and vehicle count data in an urban inner city environment in Hong Kong with the aim to gauge the importance of different engine types to particulate matter burdens in a typical urban street canyon. On an average per-vehicle basis, gasoline vehicles emitted 75 and 93 % more organics than diesel and LPG vehicles, respectively, while EC emissions from diesel vehicles were 45 % higher than those from gasoline vehicles. LPG vehicles showed no appreciable contributions to EC and thus overall represented a small contributor to traffic-related primary ambient PM1 despite their high abundance (∼ 30 %) in the traffic mix. Total carbonaceous particle mass contributions to ambient PM1 from diesel engines were only marginally higher (∼ 4 %) than those from gasoline engines, which is likely an effect of recently introduced control strategies targeted at commercial vehicles and buses. Overall, gasoline vehicles contributed 1.2 µg m−3 of EC and 1.1 µ m−3 of organics, LPG vehicles 0.6 µg m−3 of organics and diesel vehicles 2.0 µg m−3 of EC and 0.7 µg m−3 of organics to ambient carbonaceous PM1.

Characteristics, sources, and cytotoxicity of atmospheric polycyclic aromatic hydrocarbons in urban roadside areas of Hangzhou, China

ABSTRACTThe primary objective of this study is to understand the profiles, sources and cytotoxic effects of atmospheric polycyclic aromatic hydrocarbons (PAHs), which are closely related to urban air contamination and public health, in urban roadside environments. On-road sampling campaigns were conducted from 2014 to 2015 at three urban road sites in Hangzhou, China. Sixteen gaseous and particulate matter (PM) 2.5-bound PAHs were identified and quantified using gas chromatography-mass spectrometry (GC-MS). The total PAH concentrations at the three sites ranged from 750 to1142 ng/m3 and 1050 to 1483 ng/m3 in summer and winter, respectively. Low molecular weight PAHs were the most abundant compounds (77–86%) and primarily existed in gas phase. The concentrations and phase distributions of high molecular weight PAHs were varied at three sites due to the differences in traffic volume, vehicle composition, engine loading, and nearby artificial activity. Diagnostic ratios of the principal mass (m/z,178, 202, 228 and 276) parent PAHs were statistically described to determine the PAH sources to urban roadsides; principal component analysis (PCA) was applied to apportion the sources. The results indicated that high- and low-temperature fuel processes, as well as residential and industrial emissions, were major contributors to roadside PAHs. The cytotoxic potential of the roadside PAHs was evaluated using a human epithelial lung cell line (A549). Cell viability was measured after a direct exposure to PAH extract. The results reflected the profiles of roadside PAHs at the three sites. The cytotoxicity of reference PAHs was evaluated to provide further insights into the cytotoxic potential of PAHs. We found that low molecular weight PAHs, which are less cytotoxic compounds, synergistically promoted the lethal effect of cytotoxic compounds, posing a potential threat to public health.

Development and Application of a Next Generation Air Sensor Network for the Hong Kong Marathon 2015 Air Quality Monitoring.

This study presents the development and evaluation of a next generation air monitoring system with both laboratory and field tests. A multi-parameter algorithm was used to correct for the impact of environmental conditions on the electrochemical sensors for carbon monoxide (CO) and nitrogen dioxide (NO2) pollutants. The field evaluation in an urban roadside environment in comparison to designated monitors showed good agreement with measurement error within 5% of the pollutant concentrations. Multiple sets of the developed system were then deployed in the Hong Kong Marathon 2015 forming a sensor-based network along the marathon route. Real-time air pollution concentration data were wirelessly transmitted and the Air Quality Health Index (AQHI) for the Green Marathon was calculated, which were broadcast to the public on an hourly basis. The route-specific sensor network showed somewhat different pollutant patterns than routine air monitoring, indicating the immediate impact of traffic control during the marathon on the roadside air quality. The study is one of the first applications of a next generation sensor network in international sport events, and it demonstrated the usefulness of the emerging sensor-based air monitoring technology in rapid network deployment to supplement existing air monitoring.

Characterization of volatile organic compounds at a roadside environment in Hong Kong: An investigation of influences after air pollution control strategies

Abstract Vehicular emission is one of the important anthropogenic pollution sources for volatile organic compounds (VOCs). Four characterization campaigns were conducted at a representative urban roadside environment in Hong Kong between May 2011 and February 2012. Carbon monoxide (CO) and VOCs including methane (CH4), non-methane hydrocarbons (NMHCs), halocarbons, and alkyl nitrates were quantified. Both mixing ratios and compositions of the target VOCs show ignorable seasonal variations. Except CO, liquefied petroleum gas (LPG) tracers of propane, i-butane and n-butane are the three most abundant VOCs, which increased significantly as compared with the data measured at the same location in 2003. Meanwhile, the mixing ratios of diesel- and gasoline tracers such as ethyne, alkenes, aromatics, halogenated, and nitrated hydrocarbons decreased by at least of 37%. The application of advanced multivariate receptor modeling technique of positive matrix factorization (PMF) evidenced that the LPG fuel consumption is the largest pollution source, accounting for 60 ± 5% of the total quantified VOCs at the roadside location. The sum of ozone formation potential (OFP) for the target VOCs was 300.9 μg-O3 m−3, which was 47% lower than the value of 567.3 μg-O3 m−3 measured in 2003. The utilization of LPG as fuel in public transport (i.e., taxis and mini-buses) contributed 51% of the sum of OFP, significantly higher than the contributions from gasoline- (16%) and diesel-fueled (12%) engine emissions. Our results demonstrated the effectiveness of the switch from diesel to LPG-fueled engine for taxis and mini-buses implemented by the Hong Kong Special Administrative Region (HKSAR) Government between the recent ten years, in additional to the execution of substitution to LPG-fueled engine and restrictions of the vehicular emissions in compliance with the updated European emission standards.

Contributions of vehicular carbonaceous aerosols to PM<sub>2.5</sub> in a roadside environment in Hong Kong

Abstract. Hourly measurements of elemental carbon (EC) and organic carbon (OC) were made at Mong Kok, a roadside air quality monitoring station in Hong Kong, for a year, from May 2011 to April 2012. The monthly average EC concentrations were 3.8–4.9 μg C m−3, accounting for 9.2–17.7% of the PM2.5 mass (21.5–49.7 μg m−3). The EC concentrations showed little seasonal variation and peaked twice daily, coinciding with the traffic rush hours of a day. Strong correlations were found between EC and NOx concentrations, especially during the rush hours in the morning, confirming vehicular emissions as the dominant source of EC at this site. The analysis by means of the minimum OC / EC ratio approach to determine the OC / EC ratio representative of primary vehicular emissions yields a value of 0.5 for (OC / EC)vehicle. By applying the derived (OC / EC)vehicle ratio to the data set, the monthly average vehicle-related OC was estimated to account for 17–64% of the measured OC throughout the year. Vehicle-related OC was also estimated using receptor modeling of a combined data set of hourly NOx, OC, EC and volatile organic compounds characteristic of different types of vehicular emissions. The OCvehicle estimations by the two different approaches were in good agreement. When both EC and vehicle-derived organic matter (OM) (assuming an OM-to-OC ratio of 1.4) are considered, vehicular carbonaceous aerosols contributed ~ 7.3 μg m−3 to PM2.5, accounting for ~ 20% of PM2.5 mass (38.3 μg m−3) during winter, when Hong Kong received significant influence of air pollutants transported from outside, and ~ 30% of PM2.5 mass (28.2 μg m−3) during summertime, when local emission sources were dominant. A reduction of 3.8 μg m−3 in vehicular carbonaceous aerosols was estimated during 07:00–11:00 (i.e., rush hours on weekdays) on Sundays and public holidays. This could mainly be attributed to less on-road public transportation (e.g., diesel-powered buses) in comparison with non-holidays. These multiple lines of evidence confirm local vehicular emissions as an important source of PM2.5 in an urban roadside environment and suggest the importance of vehicular emission control in reducing exposure to PM2.5 in busy roadside environments.

Traffic-related trace element fate and uptake by plants cultivated in roadside soils in Toronto, Canada

This research examines traffic-related trace element emissions and their uptake by plants grown in urban roadside environments in Toronto, Canada. Oregano (Origanum vulgare), beets (Beta vulgaris) and eggplants (Solanum melongena) were cultivated at four locations with variable traffic-related metal inputs in 2010. The top 30cm of soil at the medium-traffic location was first replaced with a triple mix soil (topsoil, compost and peat) to control for pre-existing contamination. The same soil was used to cultivate at the two no/low traffic locations. Soil at the heavy traffic location was not remediated. Soil, plant tissue and plant rhizosphere samples were collected for the analysis of a range of traffic-related metal(loids) using ICP-MS, including Cr, Mn, Cu, Ni, Cd, As, Sb and Pb. Samples were digested with HNO3 and HCl using a microwave-assisted digestion procedure and then treated with HF prior to analysis. Two certified reference materials, San Joaquin soil (NIST 2709a) and trace elements in spinach leaves (NIST 1570a), were used for QA/QC purposes.Metal(loid) concentrations and accumulation over time were highly variable at the medium traffic site where the soil was replaced. Mn (p<0.10), As (p<0.10) and Sb (p<0.01) concentrations significantly increased in bulk soils from May to November 2010, while Ce (p<0.01) and Cd (p<0.10) levels decreased. For instance, median As concentrations increased from 4.39 to 8.40mg/kg over this period. Metals were found to be more bioaccessible to O. vulgare grown in the new soil at the medium traffic volume site, compared to the aged soil at the heavy traffic location. Several elements, most notably Cd, were also found to accumulate in the root zone of sampled S. melongena. Metal concentrations in S. melongena rhizosphere were better predictors of plant tissue levels, providing evidence that soil quality guidelines based on total metal concentrations for bulk soils are inadequate.

Influence of Traffic Activity on Heavy Metal Concentrations of Roadside Farmland Soil in Mountainous Areas

Emission of heavy metals from traffic activities is an important pollution source to roadside farmland ecosystems. However, little previous research has been conducted to investigate heavy metal concentrations of roadside farmland soil in mountainous areas. Owing to more complex roadside environments and more intense driving conditions on mountainous highways, heavy metal accumulation and distribution patterns in farmland soil due to traffic activity could be different from those on plain highways. In this study, design factors including altitude, roadside distance, terrain, and tree protection were considered to analyze their influences on Cu, Zn, Cd, and Pb concentrations in farmland soils along a mountain highway around Kathmandu, Nepal. On average, the concentrations of Cu, Zn, Cd, and Pb at the sampling sites are lower than the tolerable levels. Correspondingly, pollution index analysis does not show serious roadside pollution owing to traffic emissions either. However, some maximum Zn, Cd, and Pb concentrations are close to or higher than the tolerable level, indicating that although average accumulations of heavy metals pose no hazard in the region, some spots with peak concentrations may be severely polluted. The correlation analysis indicates that either Cu or Cd content is found to be significantly correlated with Zn and Pb content while there is no significant correlation between Cu and Cd. The pattern can be reasonably explained by the vehicular heavy metal emission mechanisms, which proves the heavy metals’ homology of the traffic pollution source. Furthermore, the independent factors show complex interaction effects on heavy metal concentrations in the mountainous roadside soil, which indicate quite a different distribution pattern from previous studies focusing on urban roadside environments. It is found that the Pb concentration in the downgrade roadside soil is significantly lower than that in the upgrade soil while the Zn concentration in the downgrade roadside soil is marginally higher than in the upgrade soil; and the concentrations of Cu and Pb in the roadside soils with tree protection are significantly lower than those without tree protection. However, the attenuation pattern of heavy metal concentrations as a function of roadside distance within a 100 m range cannot be identified consistently.

Lead pollution in urban roadside environments of Dar es Salaam city

Lead is among the most toxic elements in nature. It is non-biodegradable and its toxicity does not change with time. Use of leaded gasoline in motor vehicles is known as the major source of lead pollution in cities in the world. Dar es Salaam, the main city of Tanzania, has thousands of cars traveling along its roads. The lead contaminating urban roadside environments of Dar es Salaam was determined. Soil and vegetation samples were collected at various distances from the road edges of the New Bagamoyo, Sam Nujoma and Mandela roads in Dar es Salaam and analyzed for lead using Atomic Absorption Spectrophotometric methods. The results show that the soils and grasses along these major highways of Dar es Salaam were contaminated with lead. The highest lead contents (152.5 ppm in soil and 35.7 ppm in couch grass) were found in soils and vegetation within 1 to 5 meters from the road edge. The background lead levels measured at 150 meters from the road side were less than 1.2 ppm in both soil and vegetation. The lead levels along these roads exhibited strong correlation with the average traffic density (r = 0.912 for soil and r = 0.88 for grass). The levels of lead decreased exponentially with increasing distance away from the road. This suggests the major source of lead contamination of these areas was emissions from automobile traffic on these highways. The high levels of lead at 0 – 10 m from the roadside edge also suggest that soil and vegetation close to the roadside were a potential health hazard to both humans and animals. Tanzania Journal of Science Vol. 32 (2) 2006: pp. 61-68

Long-term study of NO x behavior at urban roadside and background locations in Seoul, Korea

In this study, the fundamental aspects governing the environmental behavior of nitrogen oxides were explored from two air quality-monitoring stations (AQM) in Seoul, Korea, over an 11-year period (1996–2006). The two stations were selected to represent an urban roadside (U-RS) and urban background station (U-BG). The mean concentration levels of NO x at the U-RS area exhibited a gradual decrease through years (from ∼290 ppb (1996) to 100 ppb (2003)), while those measured at the U-BG site maintained fairly stable values (∼70 ppb) throughout the years. The mean concentration levels of NO and NO 2 at the U-BG site were almost the same (∼35 ppb), while the U-RS site showed that the mean value of NO (∼127 ppb) is significantly higher than that of NO 2 (∼60 ppb). The observation of larger differences in NO level between the two sites reflects the direct impact of vehicular emissions at the U-RS site. Both correlation and factor analyses were conducted between the hourly data sets of NO x species ( N=∼90,000) and relevant environmental variables for both the sites. The results of both tests confirm the prominent role of vehicular activities in determining the level of nitrogen oxides at urban roadside environments, although such effects appear to be rather intricate at U-BG. Our comparative analysis of NO x data sets collected over varying temporal scales indicate that their distributions in the urban environment can be distinguished more clearly in spatial factors (i.e., between urban background and urban roadside) than other criteria.

An integrated multi-model approach for air quality assessment: Development and evaluation of the OSCAR Air Quality Assessment System

This paper reports on the development and evaluation of a new modelling system for studying air quality on local scales. A multi-model approach has been adopted to develop the OSCAR Air Quality Modelling System to conduct assessments at different levels of complexity. This work focuses on the evaluation of the performance of two of the models, CAR II (semi-empirical, annual averaged model) and CAR-FMI (line-source Gaussian model for hourly predictions), as integrated into the OSCAR System and employing consistent emissions and meteorological inputs. The models have been evaluated using measured NO x, NO 2, PM 10 and PM 2.5 data for 2003 from the Vallila (Helsinki) and Cromwell Road (London) monitoring stations; both of these stations are located in urban roadside environments. The evaluation consists of comparisons of annual averaged and hourly predicted and measured data, as well as detailed statistical analysis of the model performance. Overall, closer agreement between the modelled and measured data is observed for the Vallila site, where traffic levels are medium, but the models show significant underestimation for Cromwell Road which is subject to high traffic levels. The paper also discusses possible reasons for this underestimation. The wider implications of the work are also stated for development and evaluation of environmental models.

Exploratory cross-sectional investigations on ambient submicrometer particles in Salzburg, Austria

Pilot cross-sectional investigations of ambient submicrometer particles were conducted in five locations in the region of Salzburg, Austria. In conclusion, particle size distributions in the urban roadside environment of Salzburg are characterised by three peaks at approximately 0.04, 0.07 and 0.16 μm, the relative height of which varying for different days. Particle concentrations at the sampling sites located in the vicinity of traffic routes are up to 39×10 4 particles cm −3 and are on average an order of magnitude higher than at the suburban location isolated from an immediate impact of traffic. The mountainous non-roadside sites’ particle size distributions are different to those in the urban environment and are characterised by broader peaks shifted towards larger diameters. These sites have particle concentrations lower than Salzburg background. Traffic emissions did not affect airborne concentrations of other monitored pollutants to the same effect as particle number concentrations.

Exploratory cross-sectional investigations on ambient submicrometer particles in Salzburg, Austria

Abstract Pilot cross-sectional investigations of ambient submicrometer particles were conducted in five locations in the region of Salzburg, Austria. In conclusion, particle size distributions in the urban roadside environment of Salzburg are characterised by three peaks at approximately 0.04, 0.07 and 0.16 μm, the relative height of which varying for different days. Particle concentrations at the sampling sites located in the vicinity of traffic routes are up to 39×10 4 particles cm −3 and are on average an order of magnitude higher than at the suburban location isolated from an immediate impact of traffic. The mountainous non-roadside sites’ particle size distributions are different to those in the urban environment and are characterised by broader peaks shifted towards larger diameters. These sites have particle concentrations lower than Salzburg background. Traffic emissions did not affect airborne concentrations of other monitored pollutants to the same effect as particle number concentrations.