Vehicular Exhaust Research Articles

Assessing the Spatial Distribution of Soil PAHs and their Relationship with Anthropogenic Activities at a National Scale.

Soil polycyclic aromatic hydrocarbon (PAH) pollution is a major concern due to its negative impact on soil quality around the world. In China, accurate data on soil PAHs and information on the relationship with anthropogenic activities are limited. In this study, about 30,800 samples from 1833 soil sample sites were reviewed from 306 published reports to build a soil PAHs database. Based on the data obtained, the results demonstrated that 24.11% of surface soils in China are heavily contaminated. Meanwhile, the concentration of soil PAHs varied, in the order of independent mining and industrial areas (IMIA) > urban areas > suburban areas > rural areas, and the spatial distribution in China demonstrated a descending trend from north to south. Moreover, the characteristic ratio and PCA-MLR (principal component analysis-multiple linear regression) analysis demonstrated that coal combustion and vehicular exhaust emissions were the main sources of soil PAH pollution in China. On the other hand, provincial total Σ16PAHs in surface soil were significantly correlated with the per square kilometer GDP (gross domestic product) of industrial land, the per capita GDP, as well as the production and consumption of energy. These results indicate that anthropogenic factors have greatly affected the levels of soil PAHs in China. This study improves our understanding on the status and sources of soil PAH contamination in China, thereby facilitating the implementation of strategies of prevention, control, and remediation of soils.

Characteristics and Variability of Carbonaceous Aerosols over a Semi Urban Location in Garhwal Himalayas

Extraction of organic carbon (OC) and elemental carbon (EC) were carried out over Srinagar, India, an ecologically sensitive semi-urban site in Garhwal Himalays. The PM2.5 sampling was carried out during January to December, 2017 over the site. The OC and EC were extracted from PM2.5 samples using a thermo optical OC/EC analyzer. Highest OC and EC concncentrations were found during postmonsoon (17.67 ± 1.1 μg/m3 OC and 6.34 ± 0.75 EC) and Winter (17.31 ± 3.045 μg/m3 OC and 6.32 ± 0.585 μg/m3 EC) seasons are attributed to boundary layer dynamics and anthropogenic activities. The lower concentration of OC/EC was observed during monsoon season (11.64 ± 1.75 μgm−3 OC and 3.46 ± 0.19μgm−3 EC) owing to wet scavenging of aerosols and minimum count of forest fire/biomass buring incidences. Both pre-monsoon and post-monsoon season concentrations are also influenced by biomass burning in the IGP (Indo-Gangetic Plain) region and forest fires in the adjecent areas. The OC/EC ratio sounds that vehicular exhaust and biomass burning are the major source of OC/EC over the site. Generation of secondary organic carbon (SOC) at the region causes variability in OC/EC ratio in different seasons. It is found that 24–32% of PM2.5 is contributed by carbonaceous aerosols (OC and EC) over Srinagar. The pivotal role of meteorology in modulating OC/EC concentrations has been illustared in detail.

Outdoor Air Quality as Influenced by Vehicular Exhaust in Metropolitan City of Lahore, Pakistan

This study was conducted to estimate the contribution of vehicular exhaust gases towards ambient air quality in Lahore, Pakistan during 2017. LANDCOM-III flue gas analyzer was used for determination of vehicular exhaust pollutants (CO, SO2, NO2, NO, H2S, HC) for five vehicles groups (motor bikes, Qingqi rickshaw, local cars, imported cars and public transport vans) from April to September, 2017. Major pollutants were compared with their National Environmental Quality Standards (NEQS) for the country. Ambient air quality was monitored using Haz scanner HIM-6000 during smog formation in the city in October and November, 2017. From the study, it was concluded that except local and imported cars, all vehicles groups emit high concentration of pollutants as compared to the standard values. It is also observed that public transport vehicles i.e. Qingqi rickshaw and vans contribute more towards atmospheric pollution as compared to other vehicle groups in the city. During smog formation in the city, PM2.5 and PM10, NO, NO2 (NOx) concentration was decreased whereas concentration of O3, H2S and VOCs increased in November than October. Ozone concentration during the smog was below NEQS indicating that smog was not totally photochemical smog but mainly originated from vehicular and industrial exhaust gases.

Polycyclic Aromatic Hydrocarbons (PAHs) in Road Dust Collected from Myanmar, Japan, Taiwan, and Vietnam.

In this study, we determined the concentrations of polycyclic aromatic hydrocarbons (PAHs) in road dust from Myanmar, Japan, Taiwan, and Vietnam. PAHs were detected in urban and rural areas of Myanmar at mean concentrations of 630ng/g dry weight and 200ng/g dry weight, respectively. PAHs were also detected in road dust from Vietnam (mean 1700ng/g) and Taiwan (2400ng/g). PAH diagnostic ratios suggested that fossil fuel vehicular exhaust and biomass combustion are major sources of PAHs in road dust in Myanmar. Road dust samples from Japan, Taiwan, and Vietnam had similar PAH diagnostic ratios, implying that PAH sources are similar. We assessed the human health risks posed by PAHs in road dust using carcinogenic equivalents (CEQs) and incremental lifetime cancer risk (ILCR). Mean CEQs were decreased in the order Taiwan (173ng/g) > Vietnam (162ng/g for Hanoi) > Myanmar (42 and 31ng/g for Yangon and Pathein, respectively) > Japan (30ng/g for Kumamoto). Benz[a]pyrene, fluoranthene, and benzo[b]fluoranthene, the predominant PAHs, contributed > 70% of total CEQs. High ILCR values were found for Taiwan (5.9 × 10-4 and 9.9 × 10-4 for children and adults, respectively) and Vietnam (6.5 × 10-4 and 9.2 × 10-4 for children and adults, respectively, in Hanoi), indicating that PAHs in road dust pose cancer risks to the inhabitants of Taiwan and Hanoi. To our knowledge, this is the first report to identify PAH pollution in the environment and to evaluate the human health risks of these PAHs in Myanmar.

Consideration of exposure to traffic-related air pollution in bicycle route planning

IntroductionActive transportation modes such as bicycling are key elements of sustainable transportation. In order to promote bicycling as an alternative form of transportation, a holistic approach to improving the quality of the biking experience is needed. The planning of bicycle routes typically takes into consideration available right-of-way, existing roadway infrastructure, and safety concerns, among other factors. Exposure to traffic-related air pollution, on the other hand, is rarely considered despite bicyclists being vulnerable to the harmful air pollution due to their direct exposure to vehicular exhaust and increased breathing rate during biking. MethodsThis paper presents a method for incorporating exposure to traffic-related air pollution as another consideration in the bicycle route planning process. The method first applies a streamlined process for estimating the level of near-road air pollution concentration. Then a bicycle route planning tool is developed which allows planners and engineers to compare the exposure of bicyclists to traffic-related air pollution among different bicycle route options. Additionally, this paper demonstrates how to apply the method in two case studies in the City of Riverside, California. ResultsThrough the case studies, it is shown that considering exposure to traffic-related air pollution can change the results of bicycle route planning. ConclusionsThe presented case studies illustrate how the consideration of exposure to traffic-related air pollution could impact the results of bicycle route planning. Planners may refer to the presented method or use the information in the analysis differently based on their needs in specific projects. Planners and stakeholders may jointly determine how important the different factors, including exposure to traffic-related air pollution, are in relation to one another and what tradeoff between different factors will be.

Characteristics, distribution, source and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in sediments along the Yangtze River Estuary Deepwater Channel

Characteristics, distribution, source, and ecological risk level of polycyclic aromatic hydrocarbons (PAHs) in sediments along Yangtze River Estuary Deepwater Channel were investigated. Total concentration of fifteen PAHs of study area ranged between 89.52 and 208.02 ng/g (mean value 140.48 ng/g). PAHs ratios and the statistical analysis showed that local fossil fuels high-temperature combustion (vehicular exhaust, anthropogenic combustion and pyrogenic sources) was the main PAHs origin. According to sediment quality guidelines (SQGs) and other criteria, the potential ecological risks of PAHs in sediments along Yangtze River Estuary Deepwater Channel are at low to medium levels, but the presence of dibenzo[a,h]anthracene (DBahAnt) requires more study and evaluation of potential toxicological effects.

Application of Graphene Oxide Aerogel to the Adsorption of Polycyclic Aromatic Hydrocarbons Emitted from the Diesel Vehicular Exhaust

For reducing the carcinogenic BaP and polycyclic aromatic hydrocarbons (PAHs) from the moving and stationary pollution source in the atmosphere, this study demonstrated useful adsorbent of graphene oxide aerogel (GOA). The application of GOA to the adsorption of polycyclic aromatic hydrocarbons (PAHs) emitted from diesel vehicular exhaust via the dynamometer was investigated. The surface morphology and microstructure of GOA were characterized by SEM, TEM, elemental analysis, Raman, and TGA. According to the result of XRD, the grain size of GOA after 5 hours of oxidation time increased to 28.0 nm with 38 layers estimated. It demonstrated that more oxidation time greatly enhanced the crystalline structure and reformation between the GOA sheets. The GOA sheets possessed the molecular sieving property for the filtration and adsorption of carcinogenic PAH molecules due to the strong hydrogen bonding interaction along the edges and the Van der Waal's force interactions. Naphthalene, acenaphthene, benzo[a]pyrene (BaP), and dibenz[a,h]anthracene, were chosen to carry out the pre-test adsorption experiments. Especially, the BaP compound was known to be carcinogens and mutagens for humans because of their carcinogenicity and genotoxicity. From the result of pre-test adsorption of PAHs, the BAP adsorption capacity of the GOA adsorbent (310 ng BaP / 1 g GOA) in 1 hour was much better than that of XAD16 resin (0.060 ng / 1 g XAD16), which is the standard adsorbents of PAHs announced by the Environmental Protection Administration of Taiwan. Furthermore, the sample collection of PAHs emitted from the diesel exhaust was performed by using the vehicle dynamometer. At the idling speed, the best adsorption capacity of total PAHs per gram GOA was 12.1 μg g−1, and better than that of XAD16 (1.03 μg g−1). Moreover, the adsorption sleeve and adsorbent of GOA material could be recycled and reused repeatedly. The structure of the GOA adsorbent has maintained after three runs of the Soxhlet extraction and drying. Nevertheless, the structure of XAD16 resin is decomposed obviously and decreased after the Soxhlet extraction. Owing to the superior adsorption capacity of PAHs and low synthesis cost, the GOA material is possible to be one of the excellent environmental and air pollution adsorbent material in the future.

A case study on the characterization of non-methane hydrocarbons over the South China Sea: Implication of land-sea air exchange.

We present the characteristics of non-methane hydrocarbons (NMHCs) over the northern South China Sea (SCS) during a cruise campaign from September to October 2013. The mixing ratios of the total NMHCs ranged from 1.45 to 7.13 ppbv with an average of 3.54 ± 1.81 ppbv. Among the measured NMHCs, alkanes and aromatics were the major groups, accounting for 45.8 ± 8.7% and 28.7 ± 12.3% of the total NMHCs, respectively. Correlations of NMHCs with typical source tracers suggest that light alkanes and benzene were largely contributed by vehicular exhaust via long-range transport, while the other aromatics might be related to industrial sources and marine ship emissions. The spatial variations of NMHCs were observed with higher mixing ratios of NMHCs in the samples collected in the offshore areas than those in the coastal areas. Air mass back-trajectory analysis and diagnostic ratios of NMHCs show that the elevations of the total NMHCs were caused by the regional pollution transport from the southeast coast of China and/or southern China. The ozone formation potentials (OFPs) of NMHCs were calculated and the results show that the aromatics associated with marine ship emissions were the important contributors to the total OFP. This study provides useful information on the interaction between continental outflow and marine atmosphere.

Use of combined receptor modeling technique for prediction of possible sources of particulate pollution in Kozhikode, India

PM10 (particular matter having size 10 µm or lesser) was sampled at three sites in Kozhikode district, India, and was found to vary between 20.83 and 83.8 µg m−3 at Site 1; 20.78 and 99.76 µg m−3 at Site 2; and 45.6 and 123.7 µg m−3 at Site 3. A dual-channel dust sampler was used for sampling. Average concentration (87.21 µg m−3) was found highest at Site 3. Among the species identified, Fe, Ca, SO42− and Na+ were the predominant ones in all the sites. A coupled receptor model used for source apportionment was initially tested using synthetic data and then used for experimental values. Sources predicted at Site 1 were paved road dust, marine aerosol, garden waste combustion, vehicular exhaust, and diesel generators, and their percentage contributions obtained were 56, 10.2, 27.2, 0.5, 6.1 from chemical mass balance and 50.8, 11.8, 22.2, 4.5, 10.7 from positive matrix factorization, respectively. In Site 2, fertilizer, vehicular exhaust, LPG combustion, marine aerosol and dust were the main sources with percentage contributions of 43.4, 9.6, 22.3, 0.5, 24.2 from chemical mass balance and 31.4, 24.7, 11.7, 2, 30.2 from positive matrix factorization, respectively. The model suggested four sources at Site 3: diesel generator, incineration, construction and vehicular exhaust with percentage contributions of 80, 0.5, 13.5, 6 from chemical mass balance and 74.8, 1.5, 9.4, 14.2 from positive matrix factorization, respectively. Stringent rules and regulations from the policymakers can curb source emissions to a great extent. Results from the present study can be used as a base to develop the same.

Characteristics and sources of PM2.5 and reactive gases near roadways in two metropolitan areas in Canada

With concern in recent years about adverse health effects for populations living or spending significant amounts of time near large roadways, an investigation of the air quality characteristics and potential sources influencing levels of PM and its chemical composition was undertaken in Toronto and Vancouver. Three near-road monitoring stations were established in the downtown area and beside a large highway in Toronto, and beside a major trucking route in Vancouver. 24-hour integrated samples were concurrently collected at these near-road and nearby urban background sites. This study has provided detailed chemical data for PM2.5 and reactive gases (NH3, HONO and HNO3) for a year in 2015–2016. Differences between pollutant concentrations at the near-road and background urban sites were identified, and compared with observations at other urban locations. The traffic contribution was quantified as the concentration increment between the near-road and background sites. The highest increments due to traffic were observed for elemental carbon, select trace metals (e.g. Fe, Ba, Cu, Sb, Zn) and reactive gases (NH3, HONO). In general, the percent contribution of local traffic-related emissions followed a descending order of Toronto highway > Vancouver truck route > downtown Toronto for most of these pollutants. It appears that the influence of traffic-related emissions on air pollution near roads depends more on the proportion of large trucks in the fleet than the total traffic volume. Application of principal component analysis (PCA) coupled with multi-linear regression (MLR) analysis to the local traffic increment pollutant data, as well as knowledge of chemical markers representative of different sources, helped to identify the possible sources of traffic-related PM2.5. These sources include non-exhaust (brake wear abrasion, resuspended road dust) and vehicular exhaust (mixed gasoline/diesel, diesel and lubricating oil combustion) emissions. The contribution of each of the sources varied between sites. In particular, the contribution of diesel exhaust emissions, presumably from highly polluting heavy-duty vehicles and trucks, was significant at the truck route (Vancouver) and the highway (Toronto) sites. Furthermore, the substantial contribution of non-exhaust emissions (brake wear and resuspension of road dust) to PM2.5, and thus metals, with differences between sites due to traffic characteristics or local meteorology was identified. Emissions related to lube oil combustion were not statistically significant. Overall, this work delivered valuable information that serves as input for further studies involving other roads and cities in order to generate reliable and representative results for air quality management and associated health outcomes.

The characteristics and local-regional contributions of atmospheric black carbon over urban and suburban locations in Shanghai, China

Black carbon (BC), produced from the incomplete combustion of carbonaceous fuels, has emerged as a major contributor to global climate change with adverse health effects. Based on one-year (2016.06.01–2017.06.30) equivalent black carbon (eBC) measurements, this study analyzed the characteristics of eBC concentrations and the local-regional contributions at an urban site (Pudong, PD) and a suburban site (Qingpu, QP) in Shanghai, China. The results showed that the annual average eBC concentrations were 1.17 ± 0.61 μg m−3 and 2.09 ± 0.97 μg m−3 at PD and QP, respectively. The high eBC concentrations occurred in winter and at weekends both for PD and QP. There were significant negative correlation coefficients between the daily eBC, the daily wind speed (WS) and the daily boundary layer height (BLH) at PD (rws: 0.45, rblh = −0.35, p < 0.01) and QP (rws: 0.49, rblh = −0.32, p < 0.01). And the relative higher eBC concentrations coincided with southerly, southwesterly and westerly winds although these winds had lower frequencies. This could be related to the agricultural fire in these directions during summer harvesttime. The significant partial correlation coefficients of eBC-CO (ru:0.37–0.64, rs:0.18–0.44, p < 0.01) and eBC-NO2 (ru:0.49–0.74, rs:0.38–0.75, p < 0.01) could suggest that eBC mainly come from vehicular exhaust emissions in Shanghai. Besides, the higher eBC/PM2.5 (5.29% ± 1.94%) and eBC/CO(0.30% ± 0.14%) at QP indicated the more combustion activities and diesel-powered vehicle emissions in suburban areas. The concentration weighted trajectory (CWT) analysis indicated that the surrounding areas at the junction of Shanghai, Jiangsu, and Zhejiang provinces seemed to be relatively the most important sources outside of Shanghai.

Application of hopcalite catalyst for controlling carbon monoxide emission at cold-start emission conditions

Abstract Carbon monoxide (CO) is a poisonous gas particularly to all leaving being present in the atmosphere. An estimate has shown that the vehicular exhaust contributes the largest source of CO pollution in developed countries. Due to the exponentially increasing number of automobile vehicles on roads, CO concentrations have reached an alarming level in urban areas. To control this vehicular exhaust pollution, the end-of-pipe-technology using catalytic converters is recommended. The catalysts operating efficiently in a catalytic converter are a challenging class of materials for applications in cold start of engines to maintain indoor air quality. In the cold start period, the catalytic converter was entirely inactive, because the catalytic converter had not been warmed up. The cold start phase is also depending upon the characteristics of vehicles and property of catalysts. The increasing cost of noble metals with the increasing number of vehicles motivates the investigation of material concepts to reduce the precious metal content in automotive catalysts or to find a substitute for noble metals. Hopcalite (CuMnOx) catalyst could work very well at the low temperature; thus, it can overcome the problem of cold-start emissions if used in a catalytic converter. Further, low cost, easy availability and advanced synthesis methods with stabilizer, promoter, etc., advocates for the use of hopcalite as an auto exhaust purification catalyst. Although there are numerous research articles present on this topic until now, no review has been presented for demanding this issue. So there is a space in this area, and it has been made an attempt to seal this hole and progress the future scope for hopcalite catalyst for purification of exhaust gases by this review.

A comparative chemical study of PM10 in three Latin American cities: Lima, Medellín, and São Paulo

The study was part of the South American Emissions, Megacities and Climate Project (SAEMC). The objective was to identify and quantify organic and elemental carbon (OC and EC), monosaccharides, polycyclic aromatic hydrocarbons (PAHs), oxy and nitro-PAHs, water-soluble ions (WSI), and elements in particulate matter collected in intensive campaigns during a period (June, 2010) in Sao Paulo (Brazil), Lima (Peru), and Medellin (Colombia). PM10 concentration was higher in Sao Paulo than in the other two sites and 75% of the samples had concentrations above the World Health Organization (WHO) guideline. High concentrations of levoglucosan, a biomass burning tracer, highlighted the importance of this source in the Brazilian megacity. Levoglucosan-to-mannosan ratios for Sao Paulo suggested sugarcane burning, which in 2010 occurred in 70% of the state municipalities during harvest. Vehicular-related elements (Fe and Cu) had higher concentrations in Sao Paulo. As and Pb in Medellin were attributed to industrial emissions. Ni in Lima was associated with emissions from metal smelting facilities and ship heavy oil combustion. Higher total PAH concentrations and benzo[a]pyrene equivalent (BaPE) index in Sao Paulo indicated a stronger influence of vehicular exhaust in this megacity. The results highlighted the importance of biomass burning and vehicular sources for Sao Paulo, vehicular exhaust, biomass burning, and industrial sources for Medellin, and marine aerosol, together with vehicular, industrial, and ship exhaust, for Lima.

Polycyclic aromatic hydrocarbons in tree barks, gaseous and particulate phase samples collected near an industrial complex in São Paulo (Brazil)

Urban trees are a new tool for pollutant monitoring since gaseous and particulate pollutants can deposit in its barks. Polycyclic aromatic hydrocarbons (PAHs) levels were determined in gaseous phase samples collected in polyurethane foam (PUF), total suspended particles (TSP) samples collected in quartz fiber filters and tree bark samples (Tipuana and Sibipiruna) collected in the surroundings of an industrial complex in the metropolitan area of São Paulo. Benzo(b)fluoranthene presented the highest average concentration in the TSP samples and phenanthrene, the highest average concentration in the PUF samples; the sum of carcinogenic equivalents for benzo(a)pyrene (BaPEq) for both phases was above 20 ng m−3, representing a high cancer risk. The most abundant PAH for tree barks was fluoranthene; low weight PAHs presented a higher abundance than the observed in TSP. Coronene (vehicular exhaust marker) presented good correlations with fluoranthene in the tree bark samples, suggesting an influence of vehicular emissions. A tree bark sample collected near the petrochemical area presented biomarkers of petrogenic origin (hopanoids) in the mass spectrum and an unresolved complex mixture (UCM) profile. The results suggested an influence of both vehicular and industrial sources on the air quality observed in the atmosphere and tree barks samples.

Urban VOC profiles, possible sources, and its role in ozone formation for a summer campaign over Xi’an, China

To insight the urban volatile organic compound (VOC) profiles and its contribution to ozone, four-time per day (8:00-9:00, 15:00-16:00, 19:00-20:00, and 23:00-24:00) off-line VOC samples were collected from 16th July to 28th July 2018 for a summer investigation campaign over Xi'an, China. The diurnal variation was significant that the lowest TVOC concentrations were observed in the midnight period (28.4 ± 25.6ppbv) while the highest was shown in the morning (49.6 ± 40.1ppbv). The differences of total non-methane VOCs (TVOCs) between weekdays and weekend were also significant that the weekend showed significantly high VOC levels than weekdays (p< 0.05) but did not lead to significant ambient O3 increase (p> 0.05). Isopentane, a general marker for vehicle exhaust, showed descending concentrations from morning to midnight and good correlation with vehicle numbers on road, indicating a potential source to the VOCs at this site. The results from PMF proved that vehicular exhaust was the largest source to the VOCs in this study (64.4%). VOC categories showed a reverse sequence in abundance of concentrations and OFP contributions that alkenes showed the highest OFPs although with the lowest abundance in TOVCs due to their high reactivity in photochemical reactions. High OFPs from ethylene and isopentane indicated that vehicular emissions could be the largest potential OFP source in this site. OFPs from isoprene (from 1.85 to 13.4ppbv) indicated that biogenic VOCs should not be negligible in urban Xi'an city when controlling O3 pollutants. Comparison of two OFP methods was conducted and MIR method was proved to be more reasonable and scientific in summer Xi'an. Therefore, vehicular emission, the largest contributor to ambient VOCs and also OFPs, as well as biological source should be priority controlled in guiding VOC emissions and reducing O3 control policies.

Characterizing summer and winter carbonyl compounds in Beijing atmosphere

Carbonyl compounds (carbonyls) play important roles in atmospheric photochemistry, serving as reservoirs of radicals (OH, HO2, and RO2) and precursors of secondary organic aerosols (SOA). Field measurements of gaseous and particulate carbonyls were taken over urban Beijing during summer and winter, and field-measured gas-particle partitioning coefficients (Kp) were determined. Compared with theoretical values, field-measured Kp values were 4–6 orders of magnitude higher for the six detected carbonyls, which underlined the importance of heterogeneous reactions. In winter, the Kp values of carbonyl compounds were one order of magnitude higher than those in summer owing to the effect of temperature. This study applied the positive matrix factorization (PMF) model to the source apportionment of carbonyl compounds. Five factors were identified for both summer and winter, whereas the biogenic factor was only identified in summer and coal burning was only found in winter. In summer, secondary formation was the largest contributor (39%) to the measured total carbonyl compounds levels. In contrast, vehicular exhaust was the largest source of the measured total carbonyl compounds in winter (37%), although secondary formation still had an important contribution of 31%. The contribution of coal burning to ambient carbonyls was reduced by half compared with prior results. As the most abundant carbonyl compound in the atmosphere, formaldehyde in summer mainly came from secondary production (42%) and primary anthropogenic emissions (48%), while biogenic sources had a minor contribution (10%). However, 78% of formaldehyde was attributed to primary anthropogenic emissions in winter, which indicated that these winter emissions were more important sources of carbonyl compounds. Glyoxal was always dominated by secondary formation, with contributions of 56% in summer and 52% in winter.

Seasonal and diurnal characteristics of carbonyls in the urban atmosphere of Changsha, a mountainous city in south-central China

Seasonal and diurnal variations of carbonyl compounds were investigated in the ambient air of a mountainous city in China, from September 2014 to July 2015. The most abundant carbonyl compounds are formaldehyde, acetaldehyde and acetone, propionaldehyde and methacryladehyde (MACR), which were all measured in most samples. The average concentrations of formaldehyde, acetaldehyde, acetone, propionaldehyde and MACR in the atmosphere in Changsha were broken down into each season: 6.57, 3.29, 3.66, 0.67 and 0.54 μg/m3 respectively during Spring, 14.09, 8.28, 9.02, 1.28 and 0.6 μg/m3, respectively during Summer, 9.24, 5.48, 8.62, 0.73 and 0.62 μg/m3, respectively during Autumn, and 5.88, 4.84, 7.84, 0.87 and 0.26 μg/m3 respectively during Winter. And majority of the species had higher concentration during noon, showing photochemical oxidation and human activities played an important role in diurnal variation. The highest average C1/C2 (formaldehyde/acetaldehyde) ratio was observed in summer (2.10) compared to those (1.33–2.03) in other seasons, implying the photochemical activities had a positive effect on increasing the ratio of C1/C2. In this study, the monthly concentration of formaldehyde produced from isoprene accounts for 4.8%–39.1% of formaldehyde in ambient air. Strong correlation among some carbonyl compounds means that they came from the same sources. Photochemical reaction was the main source of carbonyl compounds in summer and vehicular exhaust (gasoline and diesel engines) in winter. Changsha is not a completely urbanized city and it is rich in vegetation of broadleaf evergreen shrubs. Both atmospheric photochemical reactions and anthropogenic sources, including vehicular exhaust and industrial processes, dominate the levels of carbonyls. The ILTCR and HQ values of formaldehyde and acetaldehyde are 1.23E-04 and 1.34E-05, 2.80E-01 and 1.86E-01, respectively.

Abatement of gaseous volatile organic compounds: A process perspective

Abstract Volatile organic compounds (VOCs) are a class of liquid compounds with low saturation vapor pressures, which enables them to change phases even at ambient conditions. This causes a huge problem when it comes to emissions. A large portion of VOCs cause catastrophic health effects such as cancer or liver damage even at very low concentrations (ppm), and the control of these compounds is vital in ensuring good air quality. Many VOCs are used in common household implements such as wood finishes or paints and can even be emitted off improperly ventilated cooking. This significantly alters indoor air quality, and as such, a large portion of research into these compounds have focused on indoor air. On the other hand, their widespread use as solvents in most industries along with their emission rates from vehicular exhausts results in contamination of outdoor air as well. The combination of these VOCs and NOx pollutants tends to cause ground level ozone formation, which has a large bio-toxicity and causes the formation of a smog. Densely populated cities have also seen a sharp rise in VOC emissions due to the increase in both vehicular traffic and industrialization. A myriad of options is available for the abatement of VOCs, and they are similar to other pollution control strategies. These methods can be broadly be classified into destruction, separation and hybrid methods. This review discusses the different perspectives to be considered for this scenario, along with descriptions of the different methods available to the industry, along with some novel technologies that have been introduced recently. The influential parameters for each method have been investigated, along with optimum catalyst/material selection. In addition to this, a mathematical modeling perspective has also been examined, with significance to simulation studies performed for the control of VOC emission technologies.

Profiling and potential cancer risk assessment on children exposed to PAHs in playground dust/soil: a comparative study on poured rubber surfaced and classical soil playgrounds in Seoul.

Children can get affected by polycyclic aromatic hydrocarbons (PAHs) while they interact with play area soil/rubber surfacing and exposed to PAHs by dermal contact, inhalation and hand-to-mouth activity. A comparative study has been conducted on PAHs profiling and probable cancer risk of children from PAHs present in uncovered playground surface soil and poured rubber surfaced playground dust. Surface soil and dust samples have been collected from 14 different children parks around the Korea University campus, Seoul, Republic of Korea. Concentrations of 16 PAHs in the soils/dust were found to be in a range of 2.82-57.93μgg-1. Profiling of the PAHs from the playground soils/dust reveals 3-ring PAHs are dominating with 79.9% of total PAHs content, on an average. The diagnostic ratio analysis confirms that vehicular exhaust and fossil fuel burning are likely the main sources of high molecular weight carcinogenic PAHs, whereas low molecular weight PAHs have pyrogenic origin. The probabilistic health risk assessment using Monte Carlo simulations for the estimation of the 95% cancer risk exposed to the PAHs from the surfaced playgrounds shows a little higher value than the USEPA safety standard (1.3 × 10-5). Sensitivity analysis revealed exposure duration and relative skin adherence factor for soil as the most influential parameters of the assessment. Noticeably, cancer risk is approximately 10 times higher in poured rubber surfaced playgrounds than in uncovered soil playgrounds.

Investigation of emission characteristics of NMVOCs over urban site of western India

This is the first study to characterize the variation and emission of C2-C5 non-methane volatile organic compounds (NMVOCs) in a semi-urban site of western India based on measurements during February–December 2015. Anthropogenic NMVOCs show clear seasonal dependence with highest in winter and lowest in monsoon season. Biogenic NMVOCs likes isoprene show highest mixing ratios in the pre-monsoon season. The diurnal variation of NMVOC species can be described by elevated values from night till morning and lower values in the afternoon hours. The elevated levels of NMVOCs during night and early morning hours were caused mainly by weaker winds, temperature inversion and reduced chemical loss. The correlations between NMVOCs, CO and NOx indicate the dominant role of various local emission sources. Use and leakage of liquefied petroleum gas (LPG) contributed to the elevated levels of propane and butanes. Mixing ratios of ethylene, propylene, CO, NOx, etc. show predominant emissions from combustion of fuels in automobiles and industries. The Positive Matrix Factorization (PMF) source apportionments were performed for the seven major emission sectors (i.e. Vehicular exhaust, Mixed industrial emissions, Biomass/Fired brick kilns/Bio-fuel, Petrochem, LPG, Gas evaporation, Biogenic). Emissions from vehicle exhaust and industry-related sources contributed to about 19% and 40% of the NMVOCs, respectively. And the rest (41%) was attributed to the emissions from biogenic sources, LPG, gasoline evaporation and biomass burning. Diurnal and seasonal variations of NMVOCs were controlled by local emissions, meteorology, OH concentrations, long-range transport and planetary boundary layer height. This study provides a good reference for framing environmental policies to improve the air quality in western region of India.