Transboundary Air Pollution Research Articles

Regional Environmental Cooperation on Transboundary Air Pollution in the Middle East and North Africa

Regional Environmental Cooperation on Transboundary Air Pollution in the Middle East and North Africa Inkyoung Kim (bio) Introduction1 Since the United Nations Conference on the Human Environment in 1972, international communities have endeavored to clarify the right and responsibility of states regarding transboundary pollution. Principle 21 of the 1972 Declaration at this Conference stated that countries have "the responsibility to ensure that activities within their jurisdiction or control do not cause damage to the environment of other States or of areas beyond the limits of national jurisdiction."2 Europe has been successful in tackling transboundary air pollution through the Convention on Long-range Transboundary Air Pollution in 1979. Furthermore, the Agenda 21 of the 1992 Declaration of the United Nations Conference on Environment and Development urged European countries to share their successful experiences with other regional communities to help them solve transboundary pollution issues. Have European experiences on transboundary air pollution been shared [End Page 1] with the Middle East and North Africa (MENA) region? What are the main sources of transboundary air pollution in MENA? To address those issues, what kinds of cooperative mechanisms have been created in this region? While many studies have attempted to tease out the motivations, success, and limitations of European regional environmental cooperation, regional environmental cooperation in MENA has been understudied. This study aims to investigate regional environmental cooperation in MENA, focusing on transboundary air pollution. Transboundary Pollution Most pollution problems are caused by local or regional sources, but pollution does not stay within and stop at national borders. It can travel by air or water thousands of miles. Transboundary flows of pollutants occur among countries in the same region as well as between continents. The United Nations (UN) defines transboundary pollution as "pollution that originates in one country but, by crossing the border through pathways of water or air, is able to cause damage to the environment in another country."3 More specifically, the United Nations Economic Commission for Europe (UNECE) defines transboundary air pollution as "air pollution whose physical origin is situated wholly or in part within the area under the national jurisdiction of one State and which as adverse effects in the area under the jurisdiction of another State at such a distance that it is not generally possible to distinguish the contribution of individual emission sources or groups of sources" in Article 1 of the 1979 Convention on Long-range Transboundary Air Pollution.4 It is known that some air pollutants circulate even globally and deposit on land and water bodies far from their original sources.5 Acid rain problems in Europe have led 51 countries to adopt the Convention on the Long-range Transboundary Air Pollution and various numbers of countries to ratify eight protocols on the reduction of sulfur, nitrogen oxides, volatile organic compounds, persistent organic pollutants, and ozone emissions since 1979.6 East Asia has also addressed acid rain [End Page 2] and dust sandstorms since the 1990s. As the Sahara Desert in North Africa and the whole region of the Middle East are the two hot spots of primary dust storms around the world, it is important to understand what the main sources of dust storms are and if MENA has developed any significant cooperative mechanisms to tackle transboundary impact of dust storms originated in this region. MENA Different entities identify the MENA region differently. For example, the World Bank identifies MENA as one of six regions of the world.7 It classifies the 19 countries or territories as part of the Middle East and North Africa, including Algeria, Bahrain, Djibouti, Egypt, Iran, Iraq, Jordan, Kuwait, Lebanon, Libya, Morocco, Oman, Qatar, Saudi Arabia, Syria, Tunisia, United Arab Emirates, West Bank and Gaza, and Yemen.8 The OECD does not include Iran but does include Mauritania and Palestinian Authority instead of West Bank and Gaza. The UN does not identify MENA as one of its five regional groups.9 Its agencies and programs define the MENA region differently and sometimes contradictorily. For instance, United Nations Environment Programme has six regional offices including Africa, Asia Pacific, Europe, Latin American and the Caribbean, North America, and West Asia. The regional office for Africa covers the entire African continent...

Determination of Critical Loads for Eutrophying and Acidifying Air Pollutant Inputs for the Protection of Near-Natural Ecosystems in Germany

Under the Convention on Long-Range Transboundary Air Pollution (CLRTAP) of the UN Economic Commission for Europe, UNECE, to which Germany acceded in 1982, the harmful effects of air pollutants on the environment are to be steadily reduced and ultimately limited to a level that is compatible with nature. The ICP Modelling & Mapping (ICP M&M) under the Working Group on Effects (WGE) of CLRTAP maps critical loads for the entire Convention area and calculates the exceedance risks and associated risks to vegetation and biodiversity. A current data request was made in November 2015 with the aim of submitting new or updated ecosystem-specific critical loads for protection against acidification and eutrophication. For this task, critical loads were determined by the authors for one third of the territory of Germany using the simple mass balance (SMB) method according to the ICP Mapping Manual. The permissible eutrophying nitrogen input into the ecosystem CLnut(N), as well as the acidifying sulphur input CLmaxS, can be described as the setting of the equilibrium between substance inputs and outputs, provided that specific critical limits are met. The BERN database—created by the authors—serves as the basis for modelling vegetation-specific critical limits as a complement to the SMB model. The BERN database contains near-natural plant communities with clearly definable site constancy. The 25,600 German and a further 24,600 European vegetation records dating back to before 1960 were evaluated to determine the good ecological status of the plant communities. The results of the critical load calculation show that about half of the receptor areas have critical loads for eutrophying nitrogen below 10 kg ha−1 a−1 and critical loads for acidifying sulphur were below 1500 eq ha−1 a−1. It could be demonstrated that the BERN–SMB-modelled critical loads for eutrophying nitrogen inputs show lower values on average throughout Germany than those calculated using only the previous critical limits according to the ICP Mapping Manual. These values are closer to the empirical critical loads than the critical loads without BERN data. For the goal of the German National Biodiversity Strategy by 2007 and 2020 to define ecosystem-related impact thresholds for pollutants that describe the effects on biodiversity, the BERN/SMB critical loads for the protection of ecosystems provide a precautionary scientific basis.

Highly resolved mapping of NO2 vertical column densities from GeoTASO measurements over a megacity and industrial area during the KORUS-AQ campaign

Abstract. The Korea–United States Air Quality (KORUS-AQ) campaign is a joint study between the United States National Aeronautics and Space Administration (NASA) and the South Korea National Institute of Environmental Research (NIER) to monitor megacity and transboundary air pollution around the Korean Peninsula using airborne and ground-based measurements. Here, tropospheric nitrogen dioxide (NO2) slant column density (SCD) measurements were retrieved from Geostationary Trace and Aerosol Sensor Optimization (GeoTASO) L1B data during the KORUS-AQ campaign (2 May to 10 June 2016). The retrieved SCDs were converted to tropospheric vertical column densities using the air mass factor (AMF) obtained from a radiative transfer calculation with trace gas profiles and aerosol property inputs simulated with the Community Multiscale Air Quality (CMAQ) model and surface reflectance data obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS). For the first time, we examine highly resolved (250 m × 250 m resolution) tropospheric NO2 over the Seoul and Busan metropolitan regions and the industrial region of Anmyeon. We reveal that the maximum NO2 vertical column densities (VCDs) were 4.94×1016 and 1.46×1017 molec. cm−2 at 09:00 and 15:00 LT over Seoul, respectively, 6.86×1016 and 4.89×1016 molec. cm−2 in the morning and afternoon over Busan, respectively, and 1.64×1016 molec. cm−2 over Anmyeon. The VCDs retrieved from the GeoTASO airborne instrument were correlated with those obtained from the Ozone Monitoring Instrument (OMI) (r=0.48), NASA's Pandora Spectrometer System (r=0.91), and NO2 mixing ratios obtained from in situ measurements (r=0.07 in the morning, r=0.26 in the afternoon over the Seoul, and r>0.56 over Busan). Based on our results, GeoTASO is useful for identifying NO2 hotspots and their spatial distribution in highly populated cities and industrial areas.

Spatiotemporal distribution, trend, forecast, and influencing factors of transboundary and local air pollutants in Nagasaki Prefecture, Japan

The study of PM2.5 and NO2 has been emphasized in recent years due to their adverse effects on public health. To better understand these pollutants, many studies have researched the spatiotemporal distribution, trend, forecast, or influencing factors of these pollutants. However, rarely studies have combined these to generate a more holistic understanding that can be used to assess air pollution and implement more effective strategies. In this study, we analyze the spatiotemporal distribution, trend, forecast, and factors influencing PM2.5 and NO2 in Nagasaki Prefecture by using ordinary kriging, pearson's correlation, random forest, mann–kendall, auto-regressive integrated moving average and error trend and seasonal models. The results indicated that PM2.5, due to its long-range transport properties, has a more substantial spatiotemporal variation and affects larger areas in comparison to NO2, which is a local pollutant. Despite tri-national efforts, local regulations and legislation have been effective in reducing NO2 concentration but less effective in reducing PM2.5. This multi-method approach provides a holistic understanding of PM2.5 and NO2 pollution in Nagasaki prefecture, which can aid in implementing more effective pollution management strategies. It can also be implemented in other regions where studies have only focused on one of the aspects of air pollution and where a holistic understanding of air pollution is lacking.

Analysis of the air quality in upper atmospheric boundary layer in a high-density city in Asia using 3-year vertical profiles measured by the 3-Dimensional Real-Time Atmospheric Monitoring System (3DREAMS).

Past studies focused on ground-level air quality, whereas air quality in upper atmospheric boundary layer (ABL) remains unclear due to lack of long-term and high time-resolution profile data. This study utilized the 3-Dimensional Real-Time Atmospheric Monitoring System (3DREAMS) to provide vertical profiles of aerosol backscatter coefficients and wind for three years (2019-2021), along with DustTrak to describe and analyze the characteristics of aerosols in the upper ABL in a high-density city in Asia (Hong Kong, China). It is the first study to assess the long-term record and spatial variations of upper-level aerosol in a high-density city using a LiDAR network. Results show an opposite diurnal profile of aerosol comparing between ground-level and upper ABL, which is different with the diurnal pattern observed in ground measurements (higher air pollutant concentration level in daytime and lower in nighttime). The co-location vertical wind measurements provided the explanation of the opposite diurnal patterns. The 3-year vertical profiles also show the significant spatial variation of vertical distribution of aerosol at different locations, whereas the temporal variations can be affected by various factors such as emissions and transboundary air pollution. Our episode analysis clearly demonstrated the capability of 3DREAMS to monitor transboundary air pollution with detailed information of horizontal transport and vertical convection. 3DREAMS is therefore proved as a suitable system for transboundary air pollution monitoring. Our findings provide a critical reference for atmospheric scientists and decisionmakers to understand transboundary air pollution.

Transboundary Air Pollution and Hazy Accountability: Evidence from South Korea and China

Transboundary Air Pollution and Hazy Accountability: Evidence from South Korea and China

Improvement of local ozone phytotoxicity modelling for autochthonous grape cultivars

The grapevine is a key crop for Mediterranean environments and is both sensitive to climate warming and air pollutants, of which ozone is the most damaging to crop yield and quality. Ambient ozone effects on the grapevine have been noticed since the late fifties but risk assessments are still impaired by the lack of information concerning differences in cultivar sensitivity, and adaptation capacity to environmental factors including drought conditions. This study develops a specific parametrization for autochthonous grape cultivars within a leaf-level stomatal flux model, the DO3SE model, coupled with a meteorological and atmospheric chemical transport modelling system, the WRF-CHIMERE, by using a renowned wine producing area, the Douro wine region of Portugal, as case study. The DO3SE model parametrization introduced in this study included phenology, photosynthetic active radiation, air temperature, air vapour pressure deficit, and leaf water potential as a proxy of soil water content. The modelling experiments, which included simulations with the current default Convention on Long-Range Transboundary Air Pollution DO3SE parametrization and with the proposed parametrization, covered a reference grapevine growing season (from April to September 2017), during which a measuring campaign was carried out. Simulation results show that the proposed parametrization succeeded to replicate the observed grapevine leaf-level stomatal flux gradient in the region. Both field and modified DO3SE model values indicate that considerable areas in the Douro wine region of Portugal can exceed critical phytotoxic ozone dose (POD) values, although with a lower and different spatial extent when compared to the default DO3SE parametrization for the grapevine. However, under irrigated conditions, the POD values increase, and the values are close to those obtained with the default parametrization. Overall, the research results indicate that air quality management, in particular the reduction of ozone levels in the ambient air, must also be considered to define sustainable grape and wine production strategies in the context of climate and wine production management change.

Possibility to adopt LRTAP against Transboundary Haze Pollution: What Should ASEAN Look For?

Transboundary pollution is part of air pollution originating from other countries has an impact on areas that are under the jurisdiction of other countries, The seasonal haze affected the health quality of ASEAN, it is evident that every time a forest fire occurs, the population with respiratory problems increases, including psychological stress. The objective of this paper is to investigate the problems and challenges that ATHP faces. It elaborates on the factors that contributed to LRTAP's relative success. It also analyzes and describes the measures taken in relation to the ATHP and compares its efficacy to LRTAP. The study used empirical-normative research method sourcing from literatures and journals. The study shows that ASEAN formed the Agreement on Transboundary Haze Pollution (ATHP) which has the aim of being a body that works to reduce and suppress air pollution in the ASEAN region, framed within the 1979 Convention on Long-Range Transboundary Air Pollution (LRTAP). In comparison to LRTAP, the aforementioned can be offered as a means of recommendation for the success of the AATHP. It is measurable that the importance placed on contribution, cooperation, scrutiny, democracy, and transparency in the agreement was a contributing factor in LRTAP's success.

Analysis of Chemical Components of Fine Particulate Matter Observed at Fukuoka, Japan, in Spring 2020 and Their Transport Paths

Focusing on the components of fine particulate matter, i.e., PM2.5, we have analyzed the factors that led to the high concentrations of each chemical component in PM2.5 during our observations in Fukuoka, Japan in spring 2020. The backward trajectory showed that air masses reached Fukuoka via the Yellow Sea and the southern part of South Korea when PM2.5 and each chemical component were high in concentrations. On the other hand, diurnal variations in ozone were also observed, suggesting that both transboundary and local air pollution are involved. Air masses reached the southern part of the Kyushu region when only sulfate concentrations were high. A volcano eruption led the high sulfate concentration. When only polycyclic aromatic hydrocarbons (PAHs) concentrations were high, air masses often reached the northern part of Kyushu, indicating that there may be a specific local source for PAHs.

Particulate Matter Concentrations over South Korea: Impact of Meteorology and Other Pollutants

Air pollution is a serious challenge in South Korea and worldwide, and negatively impacts human health and mortality rates. To assess air quality and the spatiotemporal characteristics of atmospheric particulate matter (PM), PM concentrations were compared with meteorological conditions and the concentrations of other airborne pollutants over South Korea from 2015 to 2020, using different linear and non-linear models such as linear regression, generalized additive, and multivariable linear regression models. The results showed that meteorological conditions played a significant role in the formation, transportation, and deposition of air pollutants. PM2.5 levels peaked in January, while PM10 levels peaked in April. Both were at their lowest levels in July. Further, PM2.5 was the highest during winter, followed by spring, autumn, and summer, whereas PM10 was the highest in spring followed by winter, autumn, and summer. PM concentrations were negatively correlated with temperature, relative humidity, and precipitation. Wind speed had an inverse relationship with air quality; zonal and vertical wind components were positively and negatively correlated with PM, respectively. Furthermore, CO, black carbon, SO2, and SO4 had a positive relationship with PM. The impact of transboundary air pollution on PM concentration in South Korea was also elucidated using air mass trajectories.

On the seasonality of long-range transport of acidic pollutants in East Asia

East Asia currently has the largest SO2 and NO x emissions in the world. The long-range transport (LRT) of acidic pollutants in this region is of great concern but the extent is not well understood. Here results from combined long-term (⩾20 years) atmospheric deposition monitoring and air trajectory analysis in East Asia were reported. The results showed that despite the large decrease of SO2 and NO x emissions in Taiwan, annual deposition of non-sea-salt sulfate (nss-) in northern Taiwan showed no decreasing trend during 1994–2020. However, when divided seasonally, both nss- and nitrate () deposition had a significant decreasing trend in the summer but not in the winter. Similar patterns were found for Japan and Korea. Air trajectory models in combination with a regional emission map indicate that LRT from eastern China contributed up to 70% of the winter deposition of nss- and in Taiwan and up to 50% in Japan and Korea. The results indicate that LRT obscured the efficacy of local pollution control measures in East Asia and suggest that transboundary air pollution regulations are required to combat acid deposition.

Payments for environmental services strategy for transboundary air pollution: A stochastic differential game perspective

Air pollution has become a global threat to societal development. The main challenges of transboundary air pollution control include two perspectives: uneven socioeconomic development of regions and the diffusion of air pollution. This paper proposes an PES strategy to alleviate transboundary air pollution by coordinating regional economic interests and environmental preferences within the joint prevention and control of air pollution region. To make the model design more realistic, we introduce the stochastic differential game model to characterize the diffusion and uncertainty of air pollution. The optimal feedback Nash equilibrium is derived in three PES scenarios (no PES, dynamic PES, and fixed-fee PES) by using the Hamilton-Jacobi-Bellman equation. Numerical simulations and sensitivity analysis are implemented to compare the optimal strategies under the three PES scenarios. The dynamic PES strategy is shown to outperform the no PES strategy and the fixed-fee PES strategy by encouraging the backward region to cut more emissions. Besides, the confidence interval theory is used to estimate the variation range of air pollution stocks, which provides a powerful diagnostic tool for policy-makers.

Monsoon climate controls metal loading in global hotspot region of transboundary air pollution

Eastern Asia is a major source of global air pollution. The distribution and intensity of these emissions are becoming well characterized, but their impact on the earth surface considering regional hydroclimatological settings has yet to be quantified. Here we show high-resolution spatiotemporal trace metal distributions of precipitation samples collected throughout the Japanese archipelago in 2013, when the world’s coal consumption was the greatest, to depict the mass transportation and deposition of pollution. The results show that metals emitted through coal combustion transported from the continent via prevailing wind were intensively deposited along the western coast of the archipelago during winter due to heavy snowing, resulting in lead (Pb) concentration of precipitations exceed the critical level (> 10 μg l−1). About 1497 tons of Pb of continental origin loaded through wet deposition accounted for over ca. 87% of the total annual flux in 2013, which constituted ca. 18.5% of the total emissions from China in 2012. This study presents the first detailed picture of monsoon climate-controlled atmospheric metal transportation and loading in the hotspot region after the phase-out of leaded gasoline in the twentieth century. The dataset can serve as a base for evaluating the effect of countermeasures implemented recent year.

Real-Time Synchronous 3-D Detection of Air Pollution and Wind Using a Solo Coherent Doppler Wind Lidar

The monitoring and tracking of urban air pollution is a challenging environmental issue. The approach of synchronous 3-D detection of wind and pollution using a solo coherent Doppler wind lidar (CDWL) is developed and demonstrated. The 3-D distribution of pollutant is depicted by the backscatter coefficient based on signal intensity of CDWL. Then, a high-resolution wind field is derived to track the local air pollution source with its diffusion and to analyze transboundary air pollution episodes. The approach is experimentally implemented in a chemical industry park. Smoke plumes caused by point source pollutions are captured well using plan position indicator (PPI) scanning with low elevation. A typical source of pollution is located, combining the trajectory of the smoke plume and the horizontal wind vector. In addition, transboundary air pollution caused by the transport of dust storms is detected in a vertical profile scanning pattern, which is consistent with the results of national monitoring stations and backward trajectory models. Our present work provides a significant 3-D detection approach to air pollution monitoring with its sources, paths, and heights by using a solo-CDWL system.

Analysis of Pollutant Emission in Poland From Road Vehicles of the Generalised Category in Accordance With the Vehicle Application Criterion

Abstract This paper presents the results of analyses that were focused on pollutant emissions from road vehicles classified into the generalised categories with respect to vehicle use. The analyses were performed using the authorised results of Poland's pollutant emission inventory, carried out in 1990–2020 by the National Centre for Emissions Management (KOBiZE) at the Institute of Environmental Protection – National Research Institute (IOŚ-PIB) in order to meet requirements for the national emissions reporting under EU legislation and the UNECE Convention on Long-range Transboundary Air Pollution. The following road vehicle categories were analysed: passenger cars, light duty vehicles, heavy-duty trucks, buses (urban buses and coaches) and L category (motorcycles, mopeds, quads, microcars). The emissions of selected pollutants that are harmful to the health of living beings were studied, i.e. nitrogen oxides, non-methane volatile organic compounds, sulfur compounds, particulate matter size fractions, carbon monoxide and lead compounds. The shares of national annual pollutant emissions from each studied vehicle category of the total pollutant emissions from road transport were determined. With the aim to assess trends in improving environmental properties of road vehicles, there were determined changes of the energy emission factors for individual pollutants in all the vehicle categories under the study. The results obtained showed dynamic decreases in the energy emission factors for nitrogen oxides, non-methane volatile organic compounds and carbon monoxide. In the case of particulate matter emission, the improvement was not as pronounced. The evident reduction in the emissions of sulfur and lead compounds in the 21st century was confirmed to be a consequence of practical elimination of these compounds from road vehicle fuels.

Transboundary air pollution and cross-border cooperation: Insights from marine vessel emissions regulations in Hong Kong and Shenzhen

• We offer causal evidence on the effects of legally binding air pollution regulations. • City-to-city dyads can effectively address locally specific air pollution. • Shenzhen's vessel fuel policy lowered SO 2 by as much as 1.47 μg/m 3 in Hong Kong. • Contiguous cities can cooperate to rapidly reduce transboundary air pollution. Many coastal cities regulate shipping emissions within their jurisdictions. However, the transboundary nature of air pollution makes such efforts largely ineffective unless they are accompanied by reciprocal, legally-binding regulatory agreements with neighbouring cities. Due to various technical, economic, and institutional barriers, it has thus far been difficult to isolate the effects of legally-binding cross-border cooperation on vessel emissions at the city-level. We exploit the unique administrative characteristics of Hong Kong and its relationship with neighbouring cities in China's Pearl River Delta to isolate the effect of legally-binding cross-border cooperation. Using a regression discontinuity design, we find that Hong Kong's unilateral implementation of marine vessel fuel control policy left the city exposed to SO 2 from marine vessel emissions originating in Shenzhen. Only when Shenzhen implemented its own legally binding policy did such pollution in Hong Kong reduce significantly across all seasons. While international agreements on air pollution are important, they face well-known difficulties related to scale and multilateral complexity. Our findings therefore suggest that contiguous cities—whether or not they straddle an international border—can play an important role in the timely development of effective emissions standards.

Assessment of Current Risks of Excessive Heavy Metal Accumulation in Soils Based on the Concept of Critical Loads: A Review

At the international level, the concept of critical loads developed under the Convention on Long-Range Transboundary Air Pollution directed by the United Nations Economic Commission for Europe is actively used to assess the risks of excessive inputs of pollutants into ecosystems. The review considers the main principles of the concept of critical loads and methods of its application for assessing the current risks of excessive accumulation of heavy metals (HMs) in soil as a component of terrestrial ecosystems from the standpoint of ecotoxicological effects (on plants, soil invertebrates, and microorganisms). Under this concept, the critical concentrations of Cd, Pb, Cu, and Zn for soils are for the first time estimated using the functions of critical concentrations taking into account the properties of soils (primarily, acidity and the contents of organic matter and clay). The main attention is paid to the rationale and development of the models for assessment of the critical concentrations and transfer functions connecting the concentrations of HM compounds in soils and soil solutions. The current environmental risks of excessive HM accumulation are assessed by comparing them with their critical concentrations. Current challenges and future prospects for analyzing the current environmental risks based on the concept of critical loads include the reduction in the uncertainty of estimates, combined effect of different metals in a multicomponent pollution, field validation of processes and modeling results, and the impacts of climate change and land use.

Source apportionment of PM2.5 in Seoul, South Korea and Beijing, China using dispersion normalized PMF

East Asian countries experience severe air pollution owing to their rapid development and urbanization induced by substantial economic activities. South Korea and China are among the most polluted East Asian countries with high mass concentrations of PM2.5. Although the occurrence of transboundary air pollution among neighboring countries has been recognized for a long time, studies involving simultaneous ground-based PM2.5 monitoring and source apportionment in South Korea and China have not been conducted to date. This study performed simultaneous daily ground-based monitoring of PM2.5 in Seoul and Beijing from January to December 2019. The mass concentrations of PM2.5 and its major chemical components were analyzed simultaneously during 2019. Positive matrix factorization (PMF) as well as dispersion normalized PMF (DN-PMF) were utilized for the source apportionment of ambient PM2.5 at the two sites. 23 h average ventilation coefficients were applied for daily PM2.5 chemical constituents' data. Nine sources were identified at both sites. While secondary nitrate, secondary sulfate, mobile, oil combustion, biomass burning, soil, and aged sea salt were commonly found at both sites, industry/coal combustion and incinerator were identified only at Seoul and incinerator/industry and coal combustion were identified only at Beijing. Reduction of the meteorological influences were found in DN-PMF compare to C-PMF but the effects of DN on mobile source were reduced by averaging over the 23 h sampling period. The DN-PMF results showed that Secondary nitrate (Seoul: 25.5%; Beijing: 31.7%) and secondary sulfate (Seoul: 20.5%; Beijing: 17.6%) were most dominant contributors to PM2.5 at both sites. Decreasing secondary sulfate contributions and increasing secondary nitrate contributions were observed at both sites.

Trans-boundary air pollution in a Southeast Asian megacity: Case studies of the synoptic meteorological mechanisms and impacts on air quality

Local and regional sources contribute to degraded air quality in many urban areas, however, the influence of trans-boundary air pollution on surface PM2.5 is still poorly characterized in Southeast Asia (SEA) megacities. This study, for the first time, utilizes multi-platform datasets to elucidate two trans-boundary PM2.5 episodes in Ho Chi Minh City (HCMC), Vietnam, over the periods 25–29 Oct 2013 and 05–08 Oct 2015. Both events persisted with limited diurnal fluctuations and more than 60% of the Air Quality Index (AQI) values at an unhealthy level. PM2.5 concentrations during the events were 100% and 115% higher on average compared to local accumulation periods in the same months, highlighting the importance of trans-boundary pollution to local HCMC air quality. Backward trajectories, MERRA-2 AOD data, and CALIPSO images revealed the origin and synoptic meteorology conditions facilitating both trans-boundary pollution events. Anthropogenic PM2.5 emissions in continental East Asia fed the 2013 event, which was then transported by strong northeasterly winds triggered by an upper-level ridge near the Tibetan Plateau and a low-pressure system in western Pacific Ocean. In contrast, the 2015 event was the result of Indonesia biomass burning (BB), which was enhanced and transported by a westward propagating Western Pacific Subtropical High triggered by a strong El Niño event. Future climate change will likely increase the number of extreme El Niño events, leading to the increase of transboundary Indonesia BB events to HCMC. This study lays the groundwork for detailing the impact of trans-boundary pollution on local air quality in SEA megacities.

NH3 and CO Emissions from Fifteen Euro 6d and Euro 6d-TEMP Gasoline-Fuelled Vehicles

Ammonia (NH3) plays a key role in atmospheric chemistry and largely contributes to the PM2.5 measured in urban areas around the globe. For that reason, the National Emission Ceilings directive, Gothenburg Protocol under the United Nations Convention on Long-Range Transboundary Air Pollution, and International Panel for Climate Change (IPCC) directive required a reduction of the emissions of NH3. Nonetheless, the European Environment Agency (EEA) indicated that road transport emissions of NH3 have increased. Moreover, recent studies reported that, not only vehicle NH3 emissions are greater than agricultural emissions in areas that gather > 40% of the U.S. population, but urban emissions of NH3 for passenger cars are underestimated by a factor of 17 in UK. In this study, fifteen gasoline-fuelled vehicles, meeting the most recent European emission standards, Euro 6d or Euro 6d-TEMP, were investigated in laboratory tests over the type-approval worldwide-harmonized light-duty vehicles test cycle (WLTC), at 23 °C and −7 °C, as well as over the motorway cycle Bundesautobahn (BAB). Results show that all the vehicles tested emitted NH3 over the different duty cycles, and presented emissions level that are comparable to those previously reported for Euro 4–Euro 6b vehicles. Finally, good agreement between the CO and the NH3 emissions was registered during the acceleration events, and, in general, a fair correlation, with R2 > 0.75, was obtained, when comparing the CO and NH3 emissions of the studied vehicles.