Urban Roadside Research Articles

Apportionment of Sources to Determine Vehicular Emission Factors of BTEX in Kolkata, India

A yearlong (December 2003 to February 2005) monitoring program was undertaken for urban roadside measurement of benzene, toluene, ethyl benzene, m- and p-xylene, and o-xylene (BTEX) at three different sites of Kolkata, India. The concentrations of monoaromatic hydrocarbons were found to be sufficiently high. Chemical mass balance model was applied to identify the sources and estimate their percentage contribution. Vehicular exhaust emission was found to be the dominant source of the target compounds and contributed 38.8–44.8% toward total volatile organic compound (VOC) level. Assuming that the vehicular exhaust fraction of the ambient BTEX level was due to the vehicular activity in the adjacent road of the monitoring site, vehicular emission factors for individual VOCs were estimated by running CALINE4 dispersion model in an inverse way. The total emission factor, average for all vehicles, was found to be in the range of 9.1 to 43.1 mg vehicle−1 km−1 for BTEX. From the measured vehicular composition during sampling, the category-wise emission factors for light-duty vehicles (LDVs), medium-duty (MDVs), and heavy-duty vehicles (HDVs), were also estimated by constrained nonlinear regression analysis. The emission factor of benzene for heavy, medium, and light vehicles was found to be 13.4, 21.0, and 31.2 mg vehicle−1 km−1 respectively.

Concentrations of anthropogenic Pt and Pd in urban roadside soils in Xuzhou, China

The potential accumulation of platinum group elements (PGE) in the environment from automobile catalysts is high in urban areas, with the major sinks being roadside soils. Therefore, this investigation presented the detailed study on characterized concentrations of Pt and Pd and their enrichment ratios in urban roadside soils in Xuzhou, China in March 2003. Data from 21 roadside topsoil samples analyzed by inductively coupled plasma-mass spectrometer (ICP-MS) illustrated that the medians of concentrations of Pt and Pd were 2.9 and 2.8 ng/g, respectively. Hierarchical clustering analysis indicated that Pt and Pd were mainly from traffic emissions. Compared to unpolluted soils, computation of Pt and Pd enrichment ratios suggested that the Xuzhou roadside soils had average enrichment factors of 3.53 for Pt (in range of 1.22–5.73) and of 3.37 for Pd (in range of 1.35–4.46). Lower Pt/Pd ratios (in range of 0.35–2.86) in relation to similar studies in other countries were observed, which might be due to the different Pt/Pd ratios in Chinese automobile catalytic converters. Moreover, fine fraction (<250 μm) contained higher concentrations of Pt and Pd compared to the coarse fraction (250–500 μmm).

Magneto-biomonitoring of intra-urban spatial variations of particulate matter using tree leaves

Preliminary mineral magnetic results from a pilot project investigating the suitability of roadside tree leaves as depositories of vehicular pollution are presented. Tree leaf surfaces (Lime: Tilia europaea; Sycamore: Acer pseudoplatanus) at four roadside and one woodland location in Wolverhampton, UK, have been monitored (July 2003 to November 2003). Mineral magnetic technologies have revealed spatial variations of particulate pollution concentration throughout the conurbation and data analysis indicates that magnetic concentration parameters are suitable proxies for fine particulate pollution, which are particularly hazardous to health. Site-specific traffic management and associated vehicle behaviour appear to be chiefly responsible for the magnetic concentration differences between sites. Magneto-biomonitoring in this way allows the high-resolution spatial mapping of particulate matter (PM) pollution, which may also benefit epidemiology in better assessing exposure to vehicular-derived particulates. Given the speed, measurement sensitivity and non-destructive nature of the technique, it is proposed that this low-cost approach offers some advantages over centralised monitoring stations to monitor urban roadside particulate pollution.

Magnetic Properties as Indicators of Cu and Zn Contamination in Soils

Concentrations of copper (Cu) and zinc (Zn) and various magnetic parameters in contaminated urban roadside soils were investigated using chemical analysis and magnetic measurements. The results revealed highly elevated Cu and Zn concentrations as well as magnetic susceptibility in the roadside soils. The mean concentrations of Cu and Zn in these roadside soils were almost twice those in average Chinese soils, with the mean magnetic susceptibility of the roadside soils reaching about 179 × 10 −8 m 3 kg −1. This enhanced magnetic susceptibility was attributed to the presence of anthropogenic soft ferrimagnetic particles. A low frequency-dependent susceptibility (2.5% ± 1.0%) observed in the roadside soils indicated the coarse multidomain (MD) ferrimagnetic grains to be the dominant contributor to magnetic susceptibility. The Cu and Zn concentration of the soils had highly significant linear correlations with magnetic susceptibility (P ≤ 0.01), anhysteretic remanent magnetization ( P ≤ 0.01), and saturation isothermal remanent magnetization ( P ≤ 0.01). This suggested that heavy metals were associated with ferrimagnetic particles in soils, which were attributed to input of traffic emissions and industrial activities. Scanning electron microscopy and energy dispersive X-ray spectra of magnetic extracts of the roadside soils further suggested the link between the magnetic signal and concentrations of heavy metals. Thus, the magnetic parameters could provide a proxy measure for the level of heavy metal contamination and could be a potential tool for the detection and mapping of contaminated soils.

Size-segregated analysis of PM 10 at two sites, urban and rural, in Münster (Germany) using five-stage Berner type impactors

Airborne particulate matter was collected at two sites, using five-stage Berner type impactors. Their different exposures to the emission sources in Münster, Germany, was examined during a campaign in January 2006. The scope of this project was to identify the sources of particulate material with the help of size- and time-resolved chemical characterisation of the particle components. The major ions such as Ca 2+, Cl −, Mg 2+, Na +, NH 4 +, NO 3 −, SO 4 2−, and carbon were analysed. The mean mass concentration of particulate matter was higher at the urban roadside than at the regional background (rural site). The main difference exists for the carbon concentration, which is in the city 1.8 times higher than in the surrounding area. The ion concentrations showed identical concentration levels at both sites, with slightly higher concentrations at the roadside, due to Na +, Cl −, and Ca 2+. The mass concentrations of particulate matter vary both between the sites and with time. At daytime, clearly higher amounts of particulate matter can be found at the roadside. Slightly enhanced concentrations of the secondary ions NH 4+ and NO 3− were found at night, but the difference is smaller than the daily increase of the particle mass due to carbon.

Evaluation of a modelling system for predicting the concentrations of PM 2.5 in an urban area

We present a modelling system that contains a treatment of the emissions and atmospheric dispersion of fine particulate matter (PM 2.5) on an urban scale, combined with a statistical model for estimating the contribution of long-range transported aerosols. The model of PM 2.5 emissions includes exhaust emissions, cold starts and driving, as well as, non-exhaust emissions originated from urban vehicular traffic. The influence of primary vehicular emissions from the road and street network was evaluated using a roadside emission and dispersion model, CAR-FMI, in combination with a meteorological pre-processing model, MPP-FMI. We have computed hourly sequential time series of the PM 2.5 concentrations in 2002 in a numerical grid in the Helsinki Metropolitan Area. The predicted results were compared against measured data at two locations in central Helsinki: urban roadside station of Vallila and urban background station of Kallio. The predicted daily average PM 2.5 concentrations agreed well with the measured values; e.g., the index of agreement values were 0.83 and 0.86 at Vallila and Kallio, respectively, and the absolute values of fractional bias ⩽0.13. As expected, the scatter of data points is substantially wider for the hourly concentration values; e.g., the index of agreement values were 0.69 and 0.74. We also computed the spatial concentration distributions of PM 2.5. The predicted contribution from long-range transport to the street level PM 2.5 varied spatially from 40% in the most trafficked areas to nearly 100% in the outskirts of the area. The emissions originated from cold starts and driving were responsible for <4% of the annual average concentrations at the roadside and urban stations. The model can potentially be used as a practical tool of assessment of urban PM 2.5 contributions in various European regions.

Pt and Pd concentrations and source in urban roadside soils from Xuzhou, China

This investigation represented the preliminary study to characterize Pt and Pd concentrations and enrichment ratios in urban roadside soils. Roadside soil samples were analyzed by ICP-MS. Data from 21 roadside topsoil samples show medians of Pt and Pd concentrations are 2.9 and 2.8ngg−1, respectively. These values are higher than those of upper crust that average 0.4 and 0.4ngg−1, respectively. The relatively lower Pt and Pd concentrations are expected due to recent introduction of catalysts to China compared to the prolonged use of catalysts in Europe. Hierarchical clustering analysis indicates that Pt and Pd in Xuzhou urban roadside soils were mainly from the traffic emissions. Computation of enrichment ratios using the upper crust values as background levels suggests that the roadside soils had enrichment medians of 6.4 for Pt (range 2.5–11.75) and of 6.75 for Pd (range 2.75–9.25). Lower Pt/Pd ratios (range 0.35–2.86) in relation to similar studies in other countries were observed due to the different automobile catalytic converters. In general, fine fraction (<250μm) contains higher Pt and Pd concentrations compared to the coarse fraction (250–500μm).

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.

Pragmatic mass closure study for PM 1.0, PM 2.5 and PM 10 at roadside, urban background and rural sites

Airborne particulate matter in the PM 10, PM 2.5 and PM 1.0 size ranges has been sampled at three sites within 20 km of one another, representing urban background, urban roadside and rural locations. The samples have been subject to chemical analysis for major constituents and the gravimetrically measured mass reconstructed using the pragmatic mass closure model of Harrison et al. [2003. A pragmatic mass closure model for airborne particulate matter at urban background and roadside sites. Atmospheric Environment 37, 4927–4933]. Despite the separation in both time and space and the inclusion of a rural site, the coefficients determined in the earlier mass closure study provide an equally good mass closure on the current dataset. This extends also to the PM 1.0 fraction when the coefficients determined for PM 2.5 are applied. The mass and composition data for PM 2.5 and PM 1.0 are intercompared and perhaps surprisingly the differences are accounted for more by components typical of fine fraction particles such as ammonium sulphate and ammonium nitrate than those residing primarily in the coarse fraction such as sea salt, calcium- and iron-rich dusts. A comparison of the composition of 24-h samples collected on days when average PM 10 exceeded 50 μg m −3 with data for all days demonstrates the immense importance of nitrates, which together with their strongly bound water, account for on average 39% of PM 10 and 46% of PM 2.5 during episode conditions, which is more than double their contribution to the overall dataset.

PM10 source characterization at urban and highway roadside locations

Levels of PM(10) were measured at two different roadside locations in the Stockholm region in Sweden, one highway south of Stockholm and one urban street canyon in the center of the city. PM(10) samples were taken during six separate campaigns over one full year, and analyzed for 29 metals, in order to help characterize sources of PM(10). Five contributing factors were identified by multivariate receptor modeling using positive matrix factorization. Factors were classified, based on their seasonal variation and published data on metal composition of different sources, as: 1) resuspension; 2) vehicle derived; 3) road salt; 4) regional combustion and 5) long-range transport. Resuspension and long-range transport were shown to be important contributors to the PM(10) levels at both sites. In fact, long-range transport was the main contributor to the PM(10) levels at the highway roadside. The vehicle source was only of major importance at the urban roadside, where it frequently contributed between 10 and 20 microg m(-3). Brake wear was an important component in the vehicle source. Vehicle exhaust was not detected as a separate source and was not identified as a major source for PM(10). To our knowledge, this is the first study identifying brake wear as a major source of PM(10) during urban driving.

PAHs associated with the leaves of Quercus ilex L.: Extraction, GC–MS analysis, distribution and sources : Assessment of air quality in the Palermo (Italy) area

In this study, the leaves of Quercus ilex L. were selected as possible bioaccumulators of polycyclic aromatic hydrocarbons (PAHs). Quercus is an evergreen plant that occurs widely in both urban and rural areas. Several sites (urban roadside, urban, urban park, suburban and rural) in and around Palermo city were investigated. The purpose of this research was to optimize analytical method for quercus leaves, investigate the degree of contamination in the urban area of Palermo by comparing PAH concentration in leaves of quercus from the several sites, establish distribution patterns and relate them to possible sources of PAHs. To this aim, the 16 recommended as priority pollutants by the Environmental Protection Agency (EPA) and perylene were analyzed. PAHs were positively correlated to atmospheric particulate gravimetrically determined on filters aspiring a known volume of air in the various stations. The analyses have been performed by gas chromatography coupled to mass spectrometry (GC–MS) in selected ion monitoring (SIM) mode. The total PAH content in the samples ranged from 92 to 1454 μg kg −1 d.w. The higher amounts of PAHs detected in leaves of quercus from the urban area of Palermo compared with the control site are diagnostic of air contamination, in particular in the zones with heavy traffic. The determination of PAHs in the leaves of quercus allows us, with very simple and fast procedures, to assess the quality of the air over a longer period, since PAHs are accumulated over the whole lifetime of the leaves, irrespective of atmospheric conditions at the moment of sampling.

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.

Correlations between heavy metals and organic carbon extracted by dry oxidation procedure in urban roadside soils

The organic fraction in soils has a significant influence on heavy metal transport. In this study, the organic carbon content was measured by dry oxidation procedure from 21 Xuzhou urban roadside soils to assess the relationships between the concentrations of heavy metals (Pb, Cu, Zn, and Cr) and the amount of organic carbon. The anthropogenic heavy metals (e.g. Pb, Cu, Zn) were strongly correlated with organic carbon (denoted by Corg−c) extracted by dry oxidation while natural heavy metal (e.g. Cr) showed no correlation to the Corg−c. The anthropogenic heavy metals were also strongly correlated with the amount of the total carbon. These results show that the anthropogenic heavy metals are mainly enriched in the organic matter in the Xuzhou urban roadside soils.

Polycyclic aromatic hydrocarbons in leaf cuticles and inner tissues of six species of trees in urban Beijing

Leaf samples of six tree species were collected along urban roadsides and a campus site in Beijing for measurement of polycyclic aromatic hydrocarbons (PAHs). PAHs in leaves were attributed to two fractions, leaf cuticles and inner leaf tissues, using sequential extraction. Total concentrations of 16 PAHs in the cuticles and the inner tissues were 69.3 ± 64.6 μg g −1(d.w.) and 1.07 ± 0.2 μg g −1(d.w.) at roadside and 57.5 ± 52.6 μg g −1 and 0.716 ± 0.2 μg g −1 on campus, respectively. The lipid-normalized inner tissue PAHs varied from 5.8 μg g −1 to 15.0 μg g −1. Similarities in PAH spectra between leaf cuticles and airborne particles and between the inner tissues and gaseous phase imply that airborne particulates and gaseous PAHs are likely the sources of PAHs for cuticles and the inner tissues, respectively. Difficulty in migration of heavier PAHs into inner tissues could be another reason.

Leaching Characteristics of Heavy Metals and As from Two Urban Roadside Soils

The leaching tests, including the Toxicity Characteristic Leaching Procedure (TCLP), EDTA extraction and BCR sequential extractions before and after EDTA treatments, were performed on two specific soils to elucidate heavy metal-associated mineral fractions and general leachability. The TCLP illustrated the low leachability of heavy metals in soils from two sites. EDTA is a strong chelator and therefore had higher extraction efficiency compared to that of TCLP. The lower extraction percentages by EDTA for As and Sb were found compared to the other heavy metals derived from anthropogenic sources. Sequential extractions showed that the importance of acid-extractable, organically-bound and Fe-Mn oxide fractions was identified for anthropogenic heavy metals with the exception of As and Ni while the importance of residual fraction was identified for endogenous metals. Changes in sequential fractions of heavy metals after leaching with EDTA are very complex and it is difficult to generalize on which fraction was more mobile than the others. These combined results are helpful in elucidating the association of heavy metals to soil fractions and the mobility characteristics of heavy metals under certain environmental conditions.

Leaching Characteristics of Arsenic and Heavy Metals in Urban Roadside Soils Using a Simple Bioavailability Extraction Test

Regular ingestion of soils could pose a potential health threat due to long-term toxic element exposure. In order to estimate the human bioavailability quotients for As and heavy metals, 12 urban roadside soil samples were collected and analyzed for As, Pb, Cu, Zn, Ni, Co, and Cr using Simple Bioavailability Extraction Test (SBET). The quantities of As, Pb, Cu, Zn, Ni, Co, and Cr leached from soils within the simulated human stomach for 1 h indicated, on average, 27.3, 71.7, 40.4, 59.3, 17.7, 27.2 and 5.6% bioavailability, respectively. Significant positive correlations were observed between the amounts leached using SBET and the total amounts dissolved with HNO(3)-HCl-HF acid mixtures. Stepwise multiple regression analysis indicated that the amounts leached with SBET for As, Pb, Zn, Ni, and Co were not related to any of the physic-chemical parameters measured (i.e., soil texture, pH, total organic matter). These results may be valuable for providing input data for risk assessment at sites subject to anthropogenic soil contamination.

Heavy Metals in Urban Roadside Plants from Amman, Jordan

Heavy Metals in Urban Roadside Plants from Amman, Jordan

Relationships between heavy metals and iron oxides, fulvic acids, particle size fractions in urban roadside soils

Urban roadside soils are the “recipients” of large amounts of heavy metals from a variety of sources including vehicle emissions, coal burning waste and other activities. The behavior of heavy metals in urban roadside soils depends on the occurrence as well as the total amount. Accordingly, knowledge of the interactions between heavy metals and other constituents in the soil is required to judge their environmental impact. In this study, correlations of heavy metal concentrations (Pb, Zn, Cu, Ag, Se, Ni, Cr and Ba) to iron extracted using dithionite–citrate–bicarbonate (DCB) buffer (FeDCB), fulvic acids and particle size fractions were examined from the Xuzhou urban roadside soils. Heavy metals except for Cr and fulvic acids had a positive significant correlation with FeDCB, indicating these metals and fulvic acids are principally associated with the surfaces of iron oxides of the soils. Significant positive correlations were also found between the contents of fulvic acids and heavy metals, showing these heavy metals (especially for Cu, Ni and Cr) form stable complexes with fulvic acids. Such finding is of importance with regard to the increased mobilization of heavy metals, e.g., into freshwater ecosystems. Ag, Se and Cr are independent of particle size fractions because of their low concentrations of Ag and Se in the studied soils. Pb, Zn, Cu, Ba and Ag are mainly enriched in the finer soil particles (especially <16 μm).

Roadside measurement and prediction of CO and PM 2.5 dispersion from on-road vehicles in Hong Kong

This study investigates the traffic induced gaseous and particle emissions dispersion characteristics from the typical urban roadside sites in Hong Kong. Concentrations of carbon monoxide, CO, fine particles, PM 2.5 pollutants, and the traffic and ambient atmospheric conditions at three selected local urban road sites were simultaneously measured. A developed local general finite line source model (GFLSM) was used to predict the local roadside CO and fine particle concentrations. A high level of agreement found between the measured and calculated CO and PM 2.5 data. Generally, the roadside concentrations of gaseous and PM 2.5 pollutants decrease with the distance away from the road and the exposure to both gaseous and particle pollutants in the vicinity of the selected urban road sites is interrelated to on-road vehicle emissions. It has also demonstrated that the developed local general finite line source model has the capability of reasonably predicting the characteristics of gaseous and particle pollutant dispersion from on-road vehicles for the local urban air quality.

Heavy meals in urban roadside soils, part 1: effect of particle size fractions on heavy metals partitioning

Urban roadside soils are important environmental media for assessing heavy metal concentrations in urban environment. However, among other things, heavy metal concentrations are controlled by soil particle grain size fractions. In this study, two roadside sites were chosen within the city of Xuzhou (China) to reflect differences in land use. Bulk soil samples were collected and then divided by particle diameter into five physical size fractions, 500–250, 250–125, 125–74, 74–45, < 45 μm. Concentrations of metals (Ti, Cr, Al, Ga, Pb, Ba, Cd, Co, Cu, Mn, Ni, V, Zn, Mo, As, Sb, Se, Hg, Bi, Ag) were determined for each individual fraction. These metals could be roughly classified into two groups: anthropogenic element (Pb, Ba, Cd, Cu, Zn, Mo, As, Sb, Se, Hg, Bi, Ag) and lithophile element (Ti, Cr, Al, Ga, Co, Mn, Ni, V) in terms of values of enrichment factor. As expected, higher concentrations of anthropogenic heavy metals (Cu, Zn, Mo, As, Hg, Bi, Ag) are observed in the finest particle grain size fraction (i.e. < 45 μm). However, heavy metals Se, Sb and Ba behave independently of selected grain size fractions. From the viewpoint of mass loading, more than 30% of the concentrations for all anthropogenic heavy metals are contributed by the particle grain size fractions of 45–74 μm at site 1 and more than 70% of the concentrations for all heavy metals are contributed by the particle grain size fractions of 45–74 and 74–125 μm at site 2. These results are important for transport of soil-bound heavy metals and pollution control by various remedial options.