Traffic-related Emissions Research Articles

Ameliorative Potency of Iridoid Glucoside Compound Catalpol on Inhibiting NF-κB-mediated Inflammation in Allergic Rhinitis-induced Mice

Background Over time, the prevalence of allergic rhinitis (AR) has surged due to various risk factors, notably attributed to global urbanization, rendering heightened levels of pollutants, including traffic-related emissions and particulate matter. About 25% of the global children population and 40% of the adult population were reported with AR. Even though AR is recognized as a systemic inflammatory disease, it often results in diverse other comorbidities, such as dermatitis, sinusitis, conjunctivitis, and otitis, requiring extensive and expensive treatment. Purpose We assessed the effectiveness of iridoid glucoside catalpol against AR in a mouse model. Catalpol is recommended in traditional Chinese medicine to treat diverse acute and chronic diseases. Methods AR was induced in mice with an ovalbumin-sensitized AR model and treated with 10 and 20 mg of catalpol. Nasal severity scoring was performed to confirm the AR induction in mice. Allergic mediators immunoglobulin E (IgE) and histamine were quantified in the serum to assess the anti-allergic response of catalpol. In nasal lavage fluid (NALF), the inflammatory mediators IgE Ab, prostaglandin D2, leukotriene C4, eosinophil cationic protein (ECP), and pro-inflammatory cytokines were measured to analyze the anti-inflammatory potency of catalpol. The binding capacity of nuclear factor-kappa B (NF-κB) to DNA was evaluated to assess the catalpol inhibitory potency against NF-κB-mediated inflammation in AR mice. To confirm the ameliorative potency of catalpol in AR mice, a histopathological analysis of nasal mucosa was performed. Results Catalpol treatment significantly decreased the nasal symptoms and reduced the allergic mediators in the serum of experimental animals. It effectively inhibited the synthesis of inflammatory mediators, ECP, and pro-inflammatory cytokines in the NALF, and also suppressed the NF-κB DNA-binding activity in AR mice. The decrease in ciliary loss, goblet cells, eosinophil infiltration, and vascular congestion observed with our nasal mucosa histopathological analysis confirmed the ameliorative potency of catalpol. Conclusion Our findings have proven catalpol inhibits NF-κB-mediated inflammatory response in AR mice. With further analysis, a potent natural compound, catalpol, can be formulated as a drug to treat AR.

Aerosol particle number concentration, ultrafine particle number fraction, and new particle formation measurements near the international airports in Berlin, Germany – First results from the BEAR study

Studies revealed airports as a prominent source of ultrafine particles (UFP), which can disperse downwind to residential areas, raising health concerns. To expand our understanding of how air traffic-related emissions influence total particle number concentration (PNC) in the airport’s surrounding areas, we conduct long-term assessment of airborne particulate exposure before and after relocation of air traffic from “Otto Lilienthal” Airport (TXL) to Berlin Brandenburg Airport “Willy Brandt” (BER) in Berlin, Germany. Here, we provide insights into the spatial–temporal variability of PNC measured in 16 schools recruited for Berlin-Brandenburg Air Study (BEAR).The results show that the average PNC in Berlin was 7900 ± 7000 cm−3, consistent with other European cities. The highest median PNC was recorded in spring (6700 cm−3) and the lowest in winter (5100 cm−3). PNC showed a bi-modal increase during morning and evening hours at most measurement sites due to road-traffic emissions. A comparison between measurements at the schools and fixed monitoring sites revealed good agreement at distances up to 5 km. A noticeable decline in this agreement occurred as the distance between measurement sites increased. After TXL was closed, PNC in surrounding areas decreased by 30 %. The opposite trend was not seen after BER was re-opened after the COVID-lock-down, as the air traffic has not reached the full capacity yet. The analysis of particle number size distribution data showed that UFP number fraction exhibit seasonal variations, with higher values in spring and autumn. This can be explained by nucleation events, which notably affected PNC.The presented findings will play a pivotal role in forthcoming source attribution and epidemiological investigations, offering a holistic understanding of airports’ impact on airborne pollutant levels and their health implications. The study calls for further investigations of air-traffic-related physical–chemical pollutant properties in areas found further away (> 10 km) from airports.

Ambient volatile organic compounds in a typical industrial city in southern China: Impacts of aromatic hydrocarbons from new industry

New industrial parks, including fine chemical, medical manufacturers, etc., are emerging in modern cities in China, whereas their emissions and impacts have not been fully illuminated. In this study, ambient volatile organic compounds (VOCs) in Huizhou were measured in three functional zones, namely new industrial, roadside, and residential zones. The average mixing ratios of total VOCs were as follow: industrial (56.22 ± 15.06 ppbv) > roadside (39.30 ± 12.96 ppbv) > residential (26.03 ± 7.31 ppbv). The ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAP) of VOCs in the industrial zone were 1.5–2.3 and 1.7–3.1 times those in the other zones, respectively. Aromatics contributed the most to OFP (39.8 % - 44.8 %) and SOAP (78.9 % - 91.0 %), with much less contributions to VOCs mixing ratios (18.3 % - 21.2 %). Naphthalene was the most abundant aromatic species across the three zones and ranked among the top contributors to OFP and SOAP among all VOCs species. Source apportionment identified that new industrial emissions and solvent use was the largest VOCs contributor in the industrial zone (53.9 %), traffic-related emissions dominated in the roadside zone (40.7 %), while new industrial and traffic-related emissions contributed similar in the residential zone (32.9 % and 34.7 %, respectively). The carcinogenic and non-carcinogenic risks of hazardous VOCs were above the acceptable threshold, primarily due to new industrial and traffic-related emissions. Our results suggested to strengthen the control of new industrial emissions and aromatics sources in Huizhou city to improve air quality and protect human health.

The evolution of tire-road wear particles and road surface texture under rolling friction

Traffic-related non-exhaust emissions are an important part of air pollution, which can adversely affect human health when inhaled. Tire-road wear is a significant source of these emissions and originates from tire-road friction. To gain a deeper understanding of the relationship between tire-road wear particles and road surface texture under rolling friction, this study conducted long-term durability experiments using a Model Mobile Load Simulator at 1/3rd scale to form a closed environmental test system. The experiments were conducted under 30°C, 50 % relative humidity, 0.7 MPa tire-ground pressure, and 5.4 km/h rolling speed. Based on an analysis of asphalt concrete-13 Marshall samples’ British Pendulum Number (BPN) value, Mean Texture Depth (MTD), wear particle size distribution, particulate matter (PM) concentration, and thermogravimetric analysis during 1600,000 rolling times, this study draws the following conclusions: This indoor research has indicated that the weight ratio of tire and asphalt wear to aggregates and mineral fillers is approximately 4.5:5.5 (after stabilization). When the tire contacts the aggregate exposed after asphalt film peeling, it significantly increases PM10 concentration. Under the rolling friction of the tire-road contact, the quality loss of asphalt concrete follows an exponential decay curve with an R2 of 0.99. Road (asphalt concrete pavement) wear per square meter of tire-road contact was 5.32×10^−4 g and 2.13×10^−4 g (before and after asphalt film peeling). It is hoped that this study will contribute to the field of tire-road wear, including non-exhaust emissions, and provide methods and theoretical support for mitigating re-suspension dust.

Estimation of Traffic Emissions by Integrating COPERT and CUBE

Air pollution caused by motor vehicles is harmful to public health. Managing the cause of this type of pollution is very difficult. Effective prediction and management of pollution can be attained only by computing air pollution. It is difficult to measure emissions directly, so it is estimated using a variety of models developed worldwide. The current study made an attempt to integrate the emission model COPERT with the traffic assignment model in CUBE software for predicting the traffic-related emissions of pollutants SO2, NO2 & PM2.5 in mixed traffic conditions by considering passenger car and light duty vehicles (LDVS), two-wheeler, auto and bus. The study also aimed to include fuel variables and meteorological variable humidity along with fleet composition, average speed and average monthly temperature as inputs. This would enable us to control the rising vehicular emission, by assessing current and future air quality and thereby implementing policy decisions.

Health risks of PM2.5-bound metals at a street canyon: implication for traffic non-exhaust emissions

Traffic non-exhaust emissions are a significant source of toxic metals in fine particular matter (PM2.5), and thus pose adverse effects on human health. PM2.5-bound metals were sampled at a street canyon and urban background site during ozone and haze periods in Zhengzhou. Higher metal concentrations were observed at the street canyon than at the urban background site, which was more affected by traffic non-exhaust, oil combustion, and dust emissions. Consequently, PM2.5-bound metals may cause significant non-carcinogenic and carcinogenic hazards to residents at the street canyon. Traffic non-exhaust and oil combustion were the primary contributors to the non-carcinogenic and carcinogenic risk at the street canyon, respectively. Furthermore, the severe health risk of PM2.5-bound metals from traffic non-exhaust emissions will remain for a long time at street canyons. This work reveals the health risks from vehicles at street canyons, which is beneficial for further reduction of traffic-related emissions.

Trends in Emissions from Road Traffic in Rapidly Urbanizing Areas

The process of urbanization has facilitated the exponential growth in demand for road traffic, consequently leading to substantial emissions of CO2 and pollutants. However, with the development of urbanization and the expansion of the road network, the distribution and emission characteristics of CO2 and pollutant emissions are still unclear. In this study, a bottom-up approach was initially employed to develop high-resolution emission inventories for CO2 and pollutant emissions (NOx, CO, and HC) from primary, secondary, trunk, and tertiary roads in rapidly urbanizing regions of China based on localized emission factor data. Subsequently, the standard road length method was utilized to analyze the spatiotemporal distribution of CO2 emissions and pollutant emissions across different road networks while exploring their spatiotemporal heterogeneity. Finally, the influence of elevation and surface vegetation cover on traffic-related CO2 and pollutant emissions was taken into consideration. The results indicated that CO2, CO, HC, and NOx emissions increased significantly in 2020 compared to those in 2017 on trunk roads, and the distribution of CO2 and pollutant emissions in Fuzhou was uneven; in 2017, areas of high emissions were predominantly concentrated in the central regions with low vegetation coverage levels and low topography but expanded significantly in 2020. This study enhances our comprehension of the spatiotemporal variations in carbon and pollutant emissions resulting from regional road network expansion, offering valuable insights and case studies for regions worldwide undergoing similar infrastructure development.

Techno-economic analysis of mixed battery and fuel cell electric bus fleets: A case study

Electric city buses are promising to reduce traffic-related emissions in city centres as their drive train emits zero local emissions in an urban context. However, battery electric buses (BEBs) have limited driving range and long charging times. Although this can be managed, as city buses operate on predetermined routes, fuel cell electric buses (FCEBs) can meet more operational requirements in terms of range and charging. Thus, many bus network operators want to design a mixed full electric bus network with BEBs and FCEBs, which involves several complex and interdependent planning tasks. We extend an existing planning model to accommodate the planning of BEBs and FCEBs with their respective charging and fuelling infrastructure, and apply it to a real-world case study. Our results indicate that a heterogeneous BEB fleet with a mix of depot and opportunity charging results in lower total costs than a depot charging concept or a homogeneous FCEB fleet. We additionally find that a heterogeneous fleet including FCEBs and BEBs with a mix of charging concepts can be beneficial under specific circumstances. More specifically, the results indicate, that FCEB are a viable technology to supplement full electric bus fleets as soon as the costs for FCEB fall below 625,000€or the costs for hydrogen fall below 4.33 €/kg H2. Interestingly, rising energy prices would not increase the utilization of FCEBs, but rather influence the choice of BEB-types.

Uncovering driving factors and spatiotemporal patterns of urban passenger car CO2 emissions: A case study in Hangzhou, China

While passenger cars offer the convenience of door-to-door travel, they are responsible for a substantial share of urban traffic-related carbon emissions, accounting for 44% of the global transport sector's emissions in 2022. Existing studies have not adequately identified the driving factors and spatiotemporal patterns of Passenger car CO2 Emissions (PCEs). To fill this gap, a comprehensive analytical framework for analysing PCE, encompassing several key components, has been developed. First, the PCE is estimated at a fine-grained level by utilising million-scale GPS trajectory data. Secondly, road network and urban functional features are extracted based on multi-source data, examining their nonlinear impacts on PCE. The driving factors of PCE during peak and off-peak periods are identified based on interpretable factor analysis. Finally, latent space clustering techniques are applied to reveal the spatiotemporal patterns of PCE, verified by significance tests. The effectiveness of this framework is demonstrated via a case study in Hangzhou, China. Notably, during peak hours, the driving factors of PCE are the road network's closeness centrality, service-related Points of Interest (POI) density, and trunk road density. In addition, five distinctive PCE patterns are identified. These findings facilitate the development of targeted and differentiated passenger car traffic management strategies, promoting carbon emission reduction in the transport sector.

Machine learning exploring the chemical compositions characteristics and sources of PM2.5 from reduced on-road activity

Particulate nitrate pollution has emerged as a major contributor to haze events in urban environment, due to the rapid increase of vehicle emissions. However, a comprehensive formation mechanisms of PM2.5 responses to vehicle emissions control still remains high uncertainties. In our study, hourly criteria air pollutants, meteorological parameters and chemical compositions of PM2.5 were continuously measured with or without reduced on-road activity at the coastal city in southeast China. XG Boost-SHAP models analysis showed that increasing concentrations of NO3−, NH4+, and BC contribute to elevated PM2.5 levels, due to the influence of vehicle emissions. Based on PMF model results, there was a notable increase in the contributions of traffic-related emissions, industrial activities, and dust sources to PM2.5, with increments of 13%, 4%, and 7%, respectively. In addition, metal elements such as Mn emerged as the primary contributor to hazard quotient (HQ) values, originated from non-exhaust emissions of vehicles, which might cause the potential toxic risks on human health, particularly during haze events. Hence, this study improve the understanding of air quality and human health both direct and indirect responses to vehicle emissions control in future urban management.

Combination of toxicological and epidemiological approaches for estimating the health impact of atmospheric pollutants. A proof of concept for NO2

BackgroundRegular monitoring of the air pollutant nitrogen dioxide (NO2), an indicator for traffic-related emissions, is a priority in urban environments. The health impacts associated with NO2 exposure are the result of a combination of factors, including concentration, duration of exposure, and interactions with other pollutants. WHO has established air quality guidelines based on epidemiological studies. ObjectiveThis study develops a new concept "Health Impact Pathways (HIPs)" using adversity as a probabilistic indicator of health effects. For this purpose, it integrates available toxicological and epidemiological information, using Adverse Outcome Pathways (AOPs), in order to understand chemical-biological interactions and their consequences on health. MethodsLiterature review and meta-analysis of toxicological data supported by expert judgment were performed to establish: a) adversity pathways, b) quantitative criteria for scoring the observed toxicological effects (adversity indicators), c) NO2 exposure - adversity relationship for both long-term (1–36 months) and shortterm (1–7 days). The NO2 daily concentrations from January 2001 to December 2022, were obtained from Madrid city Air Quality network monitoring database. Adversity levels were compared with relative risk levels for all-cause and respiratory mortality estimated using linear equations from WHO 2021 guidelines. ResultsNon-linear relations were obtained for all long- and short-term NO2 related adversity indicators; for long-term effects, the best fitting was obtained with a modified Haber's law model with an exponential coefficient for the exposure time of 0.25. Estimations are presented for a set of case studies for Madrid city, covering temporal and spatial variability. A clear improvement trend along the two decades was observed, as well as high inter- and intra-station variability; the adversity indicators provided integrated information on the temporal and spatial evolution of population level risk. DiscussionThe proposed HIP conceptual approach offers promising advances for integrating experimental and epidemiological data. The next step is linking the concentration-adversity relationship with population health impacts through probability estimations, the preliminary estimations confirm the need for assessing independently different population groups.

Of study enthusiasts and homebirds: students’ everyday mobility and sustainability dilemmas in online higher education

PurposeOnline education enables location-independent learning, potentially providing university students with more flexible study programs and reducing traffic-related CO2 emissions. This paper aims to examine whether online education can contribute to university-related sustainable everyday mobility, with particular consideration given to aspects of social sustainability and potential rebound effects. Specifically, it explores sustainability dilemmas that arise from conflicting social and ecological effects.Design/methodology/approachDrawing on qualitative data from mobility diaries and extensive semistructured interviews (n = 26) collected at Osnabrück University of Applied Sciences in Germany, this study deploys thematic analysis and a typification approach to analyze and classify students’ daily practices related to studying, mobility and dwelling, which may be impacted by online education.FindingsThe study identifies six distinct student types with diverse practices in studying, mobility and dwelling. Comparisons between student types reveal stark differences regarding professional and social goals that students associate with their studies, influencing university-related mobility and residential choices. This leads to varying assessments of online education, with some students expecting benefits and others anticipating severe drawbacks.Practical implicationsThe typology developed in this paper can assist Higher Education Institutions (HEIs) in comparable contexts in understanding the distinct needs and motivations of students, thereby proactively identifying sustainability dilemmas associated with online education. By leveraging these findings, HEIs can effectively balance diverse interests and contribute meaningfully to sustainability.Originality/valueTo the best of the authors’ knowledge, this study is among the first to systematically investigate conflicts and rebound effects of online education in the context of sustainable mobility within HEIs.

Low-fare public transport and modal shift – Lessons from Bonn, Germany

The air quality in many German cities does not comply with EU-wide standards. Vehicle emissions, in particular, have been identified as an important cause of air pollution. As a result, driving bans for diesel vehicles with critical pollutant groups have been imposed by courts in many places in recent history. Against the backdrop of the growth of major German cities over the last few years, the question has become whether and how a change in the modal split in favor of more environmentally and climate-friendly public transport sector can be achieved. The Federal City of Bonn is one of five model cities that is testing measures to reduce traffic-related nitrogen dioxide emissions through a Climate Ticket as a mobility flat rate for one year for 365 €, which is part of the two-year "Lead City" project funded by the federal government. A quantitative survey (n = 1,315) of Climate Ticket users as well as the logistic regression carried out confirm that a change in individual mobility behavior in favor of public transport is possible by subsidizing the ticket price. The results show that individual traffic could be saved on the city's main congestion axes. In order to achieve a sustainable improvement in air quality, such a Climate Ticket must be granted on a permanent basis, with a well-designed mobility offer and must be generous in terms of the group of authorized persons and the area of validity.

Uncovering the spatiotemporal patterns of traffic-related CO2 emission and carbon neutrality based on car-hailing trajectory data

Traffic-related carbon dioxide (CO2) emissions constitute a significant portion of greenhouse gas emissions in urban areas, necessitating a comprehensive understanding of their spatiotemporal patterns and their implications for carbon neutrality. While previous studies have focused on exploring CO2 emission patterns, they often overlook the current carbon neutrality associated with these emissions. This study addresses this gap by investigating spatiotemporal patterns and carbon neutrality using car-hailing trajectory data from Xi'an, China. Initially, a link-based CO2 emission model is formulated by considering various driving conditions. Subsequently, the spatiotemporal patterns of traffic-related CO2 emissions are examined by kernel density estimation (KDE) and Getis-Ord models. Finally, carbon neutrality is assessed using the coupling coordination degree (CCD) model, which explores the relationship between traffic-related CO2 emissions and urban vegetation coverage. Empirical experiments found that hotspots of traffic-related CO2 emissions are concentrated at main roads or intersections, while coldspots are dispersed on residential roads. The findings highlight the significant influence of land use type, public services, and road levels on CO2 emission patterns, as well as the critical role of vegetation coverage in improving carbon neutrality levels. Based on these findings, several strategies are recommended to foster low-carbon city development, including expanding public transport services, integrating subway stations along main roads, optimizing traffic lights, increasing urban green spaces, and diversifying commercial facilities in traffic-related areas. These strategies emphasize the importance of incorporating carbon neutrality into urban planning and policy-making to achieve sustainable urban development.

Decomposing PM2.5 concentrations in urban environments into meaningful factors 2. Extracting the contribution of traffic-related exhaust emissions

Vehicle-emitted fine particulate matter (PM2.5) has been associated with significant health outcomes and environmental risks. This study estimates the contribution of traffic-related exhaust emissions (TREE) to observed PM2.5 using a novel factorization framework. Specifically, co-measured nitrogen oxides (NOx) concentrations served as a marker of vehicle-tailpipe emissions and were integrated into the optimization of a Non-negative Matrix Factorization (NMF) analysis to guide the factor extraction. The novel TREE-NMF approach was applied to long-term (2012–2019) PM2.5 observations from air quality monitoring (AQM) stations in two urban areas. The extracted TREE factor was evaluated against co-measured black carbon (BC) and PM2.5 species to which the TREE-NMF optimization was blind. The contribution of the TREE factor to the observed PM2.5 concentrations at an AQM station from the first location showed close agreement (R2=0.79) with monitored BC data. In the second location, a comparison of the extracted TREE factor with measurements at a nearby Surface PARTiculate mAtter Network (SPARTAN) station revealed moderate correlations with PM2.5 species commonly associated with fuel combustion, and a good linear regression fit with measured equivalent BC concentrations. The estimated concentrations of the TREE factor at the second location accounted for 7–11 % of the observed PM2.5 in the AQM stations. Moreover, analysis of specific days known to be characterized by little traffic emissions suggested that approximately 60–78 % of the traffic-related PM2.5 concentrations could be attributed to particulate traffic-exhaust emissions. The methodology applied in this study holds great potential in areas with limited monitoring of PM2.5 speciation, in particular BC, and its results could be valuable for both future environmental health research, regional radiative forcing estimates, and promulgation of tailored regulations for traffic-related air pollution abatement.

Significantly underestimated traffic-related ammonia emissions in Chinese megacities: Evidence from satellite observations during COVID-19 lockdowns

Ammonia (NH3) plays an important role in the formation of atmospheric particulate matter, but the contribution of traffic-related emissions remains unclear, particularly in megacities with a large number of vehicles. Taking the opportunity of the stringent COVID-19 lockdowns implemented in Beijing and Shanghai in 2022, this study aims to estimate the traffic-related NH3 emissions in these two megacities based on satellite observations. Differences between urban and suburban areas during the lockdown and non-lockdown periods are compared. It was found that despite different dominating sources, the overall NH3 concentrations in urban and suburban areas were at a similar level, and the lockdown resulted in a more prominent decrease in urban areas, where traffic activities were most heavily affected. The traffic-related contribution to the total emission was estimated to be ∼30% in megacities, and ∼40% in urban areas, which are about 2–10 times higher than that in previous studies. The findings indicate that the traffic-related NH3 emissions have been significantly underestimated in previous studies and may play a more critical role in the formation of air pollution in megacities, especially in winter, when agricultural emissions are relatively low. This study highlights the importance of traffic-related NH3 emissions in Chinese megacities and the need to reassess the emissions and their impacts on air quality.

The relative contributions of traffic and non-traffic sources in ultrafine particle formations in Tehran mega city

Emissions of ultrafine particles (UFPs; diameter < 100 nm) are strongly associated with traffic-related emissions and are a growing global concern in urban environments. The aim of this study was to investigate the variations of particle number concentration (PNC) with a diameter > 10 nm at nine stations and understand the major sources of UFPs (primary vs. secondary) in Tehran megacity. The study was carried out in Tehran in 2020. NOx and PNC were reported from a total of nine urban site locations in Tehran and BC concentrations were examined at two monitoring stations. Data from all stations showed diurnal changes with peak morning and evening rush hours. The hourly PNC was correlated with NOx. PNCs in Tehran were higher compared to those of many cities reported in the literature. The highest concentrations were at District 19 station (traffic) and the lowest was at Punak station (residential) such that the average PNC varied from 8.4 × 103 to 5.7 × 104 cm−3. In Ray and Sharif stations, the average contributions of primary and secondary sources of PNC were 67 and 33%, respectively. Overall, we conclude that a decrease in primary emission leads to a decrease in the total concentration of aerosols, despite an increase in the formation of new particles by photo nucleation.

Accumulation of Atmospheric PAHs in White Mustard – Can the Seeds Be Affected?

Traffic-related particulate matter emissions have been considerably reduced due to stringent regulations in Europe. However, emission of diesel-powered vehicles still poses a significant environmental threat, affecting rural ecosystems and agriculture. Several studies have reported that polycyclic aromatic hydrocarbons (PAHs), a group of potentially toxic organic compounds, can accumulate in crops and vegetables. In our study, white mustard (Sinapis alba L.) plants were experimentally treated with an extract of diesel exhaust. PAH concentrations were measured in the different plant compartments (stems, leaves and seeds), bioconcentration factors (BCFs) were also calculated. Significant accumulation was measured in the leaves and seeds, stems showed lower accumulation potential. All plant matrices showed high tendency to accumulate higher molecular weight PAHs, BCF was the highest in the 6-ring group. The fact that considerable accumulation was experienced in the seeds might show the risk of cultivating crops nearby roads highly impacted by traffic-related emissions.

Large-scale automated emission measurement of individual vehicles with point sampling

Abstract. Currently, emissions from internal combustion vehicles are not properly monitored throughout their life cycle. In particular, a small share of vehicles (&lt; 20 %) with malfunctioning after-treatment systems and old vehicles with outdated engine technology are responsible for the majority (60 %–90 %) of traffic-related emissions. Remote emission sensing (RES) is a method used for screening emissions from a large number of in-use vehicles. Commercial open-path RES systems are capable of providing emission factors for many gaseous compounds, but they are less accurate and reliable for particulate matter (PM). Point sampling (PS) is an extractive RES method where a portion of the exhaust is sampled and then analyzed. So far, PS studies have been predominantly conducted on a rather small scale and have mainly analyzed heavy-duty vehicles (HDVs), which have high exhaust flow rates. In this work, we present a comprehensive PS system that can be used for large-scale screening of PM and gas emissions, largely independent of the vehicle type. The data analysis framework developed here is capable of processing data from thousands of vehicles. The core of the data analysis is our peak detection algorithm (TUG-PDA), which determines and separates emissions down to a spacing of just a few seconds between vehicles. We present a detailed evaluation of the main influencing factors on PS measurements by using about 100 000 vehicle records collected from several measurement locations, mainly in urban areas. We show the capability of the emission screening by providing real-world black carbon (BC), particle number (PN) and nitrogen oxide (NOx) emission trends for various vehicle categories such as diesel and petrol passenger cars or HDVs. Comparisons with open-path RES and PS studies show overall good agreement and demonstrate the applicability even for the latest Euro emission standards, where current open-path RES systems reach their limits.

Source-specific light absorption and radiative effects decreases and indications due to the lockdown

The ‘extreme’ emission abatement during the lockdown (from the end of 2019 to the early 2020) provided an experimental period to investigate the corresponding source-specific effects of aerosol. In this study, the variations of source-specific light absorption (babs) and direct radiative effect (DRE) were obtained during and after the lockdown period by using the artificial neural network (ANN) and source apportionment environmental receptor model. The results showed that the babs decreased for all sources during the two periods. The most reductions were observed with ∼90% for traffic-related emissions (during the lockdown) and ∼85% for coal combustion (after the lockdown), respectively. Heightened babs (370 nm) values were obtained for coal and biomass burning during the lockdown, which was attributed to the enhanced atmospheric oxidization capacity. Nevertheless, the variations of babs (880 nm) after the lockdown was mainly due to the weakening of oxidation and reduced emissions of secondary precursors. The present study indicated that the large-scale emission reduction can promote both reductions of babs (370 nm) and DRE (34–68%) during the lockdown. The primary emissions decrease (e.g., Traffic emission) may enhance atmosphere oxidation, increase the ultraviolet wavelength light absorption and DRE efficiencies. The source-specific emission reduction may be contributed to various radiation effects, which is beneficial for the adopting of control strategies.