Primary Emissions Research Articles

VOC emission rates from an indoor surface using a flux chamber and PTR-MS

Arising from the Chemical Assessment of Surfaces and Air (CASA) 2022 study at the National Institute of Standards and Technology (NIST) Net-Zero Energy Residential Test Facility (NZERTF), this paper presents the first evaluation of indoor surface emissions to a house measured with a surface flux chamber coupled to an online, non-targeted volatile organic compound (VOC) mass spectrometric detection. These surface emissions are compared to those assessed using ambient, whole house indoor VOC measurements and the outdoor air change rate. Chamber emission rates varied by almost four orders of magnitude across 35 quantified VOCs. The whole house emissions measured by campaign-long ambient measurements and the flux chamber emissions (when scaled to the painted surface area of the house) are similar, with an average ratio between the two of 1.3 ± 1.0. The general agreement between these two approaches indicates that the flux chamber was not solely measuring primary emissions from building materials located below the chamber. Rather, the results suggest that over the 12-year house lifetime, VOCs have been widely distributed around the house, migrating from their primary sources to secondary surface reservoirs. With the house in a quasi-steady state, the thermodynamic activities (i.e., the vapor pressures) of the VOCs within the different reservoirs become similar. Emissions of aromatics and monoterpenes have declined since the house was built, whereas aldehyde emissions have remained relatively constant.

Comparative Analysis of Primary and Secondary Emission Mitigation Measures for Small-Scale Wood Chip Combustion

The objective of this study is to systematically investigate not only the influence of different additive types—beyond the much-considered case of aluminum-silicate-based additives—but also to carry out an additional comparison between primary and secondary emission mitigation measures during small-scale wood-chip combustion. Hence, combustion trials are realized within a 33-kW combustion plant. Pine wood chips additivated with 1.0 wt%a.r. of four additives have shown promising emission reduction effects in the past; namely kaolin (i.e., aluminum-silicate-based), anorthite (i.e., aluminum-silicate- and calcium-based), aluminum hydroxide (i.e., aluminum-based), and titanium dioxide (i.e., titanium-based). In addition to the primary mitigation measure (i.e., (fuel) additivation), an electrostatic precipitator (ESP) as a common secondary mitigation measure for total particulate matter (TPM) reduction is used for comparison. In addition to standard analyses (e.g., gravimetric determination of TPM emissions), an extended methodology (e.g., characterization of the elemental composition and ultrafine particle fraction of TPM emissions) is applied. The results show that the additivation of wood chips with kaolin and anorthite can lead to an operation of the combustion plant in compliance with the German legal TPM limit values by undercutting the absolute emission level achievable by the ESP. Additionally, kaolin and anorthite achieve significant reductions in carbon monoxide (CO) emissions, while kaolin simultaneously, and similarly to ESP, also leads to a shift in the particle size number distribution of PM emissions towards coarser particles. All additives show a significant reduction of potassium (K) emissions by the formation of high-temperature stable K compounds in the resulting ashes.

PM10 Organic Aerosol Fingerprints by Using Liquid Chromatography Orbitrap Mass Spectrometry: Urban vs. Suburban in an Eastern Mediterranean Medium-Sized Coastal City

This study compares the PM10 (particulate matter of diameter smaller than 10 μm) organic aerosol composition between urban and suburban stations in Heraklion, Crete, during winter 2024 in order to highlight the impact of local anthropogenic activities on urban atmospheric particulate matter pollution. Using an HPLC-ESI-MS Orbitrap analyzer (High Performance Liquid Chromatography-Electrospray Ionization-Mass Spectrometry) in full MS scan mode at a resolution of 140,000, 48 daily aerosol filter extracts were analyzed in both positive and negative modes, resulting in the detection of 2809 and 3823 features, respectively. Features with at least five times higher intensity in the urban environment compared to the suburban, and p < 0.05, were deemed significant. A correlation with black carbon (r > 0.6) was observed for 71% of significant urban features in positive mode. These features showed a predominance of low O:C ratios (<0.2) and the majority were classified as intermediate volatility organic compounds (IVOCs), indicating fresh primary emissions. A clear urban–suburban distinction was shown by PCA of positive mode features, unlike the negative mode features. Regarding the total intensity of the features, urban samples were on average 55% higher than suburban samples in positive mode and 39% higher in negative mode. This study reveals the molecular profile of locally emitted combustion related organics observed in positive mode in an urban environment.

Effects of Ammonia Mitigation on Secondary Organic Aerosol and Ammonium Nitrate Particle Formation in Photochemical Reacted Gasoline Vehicle Exhausts

Gaseous air pollutants emitted primarily by anthropogenic sources form secondary products through photochemical reactions, complicating the regulatory analysis of anthropogenic emissions in the atmosphere. We used an environmental chassis dynamometer and a photochemical smog chamber to conduct a parameter sensitivity experiment to investigate the formation of secondary products from a gasoline passenger car. To simulate the mitigation of ammonia emissions from gasoline vehicle exhausts assuming future emission controls and to allow photochemical oxidation and aging of the vehicle exhaust, ammonia was selectively removed by a series of five denuders installed between the vehicle and photochemical smog chamber. Overall, there were no differences in the formation of secondary organic aerosols and ozone with or without ammonia mitigation. However, the potential for ammonium nitrate particle formation was significantly reduced with ammonia mitigation. In addition, ammonia mitigation resulted in increased aerosol acidity due to nitric acid in the gas phase not being neutralized by ammonia and condensing onto the liquid particle phase, indicating a potentially important secondary effect associated with ammonia mitigation. Thus, we provide new insights into the effects of ammonia mitigation on secondary emissions from gasoline vehicle exhaust and into a potentially useful experimental approach for determining primary and secondary emissions.

Hydrogen blending with natural gas for combustion efficiency improvement toward decarbonisation of power plants

Abstract The 12th Malaysia Plan highlighted Malaysia’s commitment to reduce Greenhouse Gas (GHG) emissions by 45% based on Gross Domestic Product (GDP) in 2030 and reach net zero by 2050. To achieve this target, Malaysia has to decarbonise the energy sector as it is the primary emission source, contributing up to 75% of GHG emissions in Malaysia. Hydrogen fuel is getting much attention globally, and it has been said that it can be a new renewable energy source to replace fossil fuels. Hydrogen combustion is clean and only produces water and energy. However, several studies have identified that hydrogen combustion could produce NOx, which is more harmful to the environment than CO2. Studies on hydrogen application in the energy sector in Malaysia are limited, and the implementation of total hydrogen fuel in power plants may not happen shortly. Hence, a fundamental study was proposed on co-firing hydrogen and natural gas fuel. This study aimed to examine co-firing characteristics such as temperature, pressure, and air-to-fuel ratio on GHG emission and energy release to find the optimum natural gas-to-hydrogen ratio. The model was developed using Aspen Plus, and hydrogen-natural gas blend percentages varied from 0% to 30%. The findings showed that increased operating temperature led to higher NOx formation, while varying pressures did not impact the CO2 and NOx formation. The pure natural gas combustion system was more sensitive towards air-to-fuel ratio changes, and an increase in air-to-fuel ratio to 1.5 led to 160% higher NOx formation due to an increase in nitrogen content. The combustion of the hydrogen blend led to lower CO2 formation but higher NOx formation. Lastly, the energy released by the hydrogen blending system was lower due to the formation of water that absorbed the heat released by the combustion.

Characterizing organophosphate esters and chlorinated paraffins in surface soils affected by diverse e-waste disassembling process in South China: Occurrence, distinct emission, and risk assessment

E-waste recycling activities are a crucial emission source of organic pollutants, posing potential risks to the surrounding environment and human health. To understand the potential impact related to diverse e-waste dismantling activities, we investigated two categories of popular flame retardants (i.e., organophosphate esters (OPEs) and chlorinated paraffins (CPs) and their resultant possible ecological risk in 53 surface soil samples from Qingyuan, a well-known e-waste recycling region in South China. Varied concentrations of ΣOPEs (20.5–8720 ng/g) and ΣCPs (920–16800 ng/g) were observed at diverse dismantling sites, while relatively low levels of ΣOPEs (6.13–1240 ng/g) and ΣCPs (14.8–2870 ng/g) were found in surrounding soils. These results indicated that primitive e-waste dismantling processes were the primary emission source of OPEs and CPs in the studied area, with e-waste dumping and manual dismantling being the most important emission sources for OPEs and CPs. More importantly, CPs could be degraded/transformed into more toxic intermediates via dechlorination and decarbonization during the burning of e-waste. Furthermore, our results indicated the potential ecological risks posed by OPEs and CPs related to e-waste recycling.

Size resolved particle contribution to vehicle induced ultrafine particle number concentration in a metropolitan curbside region

The concentrations and behavior of nano particles (10–1000 nm) in Delhi, a densely populated megacity, in different seasons (winter, spring, summer, monsoon, and autumn) are examined, for the first time. The concentration of particles is classified into four different sizes as Nnuc (10–30 nm, nucleation), Nsatk (30–50 nm, small Aitken), Nlatk (50–100 nm, large Aitken), and Nacc (100–1000 nm, accumulation mode), and the total (10–1000 nm) particle number concentration (PNC) as Ntotal. PNC ranges between 104 cm−3 and 106 cm−3 over Delhi during the year, and the highest concentration occurs in winter. Winter concentration is 2, 1.6 and 1.3 times higher than monsoon, summer, autumn and spring concentrations, respectively. Nnuc, Nsatk, Nlatk and Nacc and their respective contributions to total PNC exhibit significant seasonal variations. During winter Nlatk and Nacc contribute more to total due to coagulation, with Nacc alone contributing >40% to total PNC. Nnuc, Nsatk, and Nlatk are higher in spring and summer during mid-day due to nucleation and/or ultrafine particle burst events. The direct primary emissions from engine exhaust produce a prominent double hump structure during morning and evening peak hours in winter and autumn. PNC and their contributions exhibit day-night variations as they are influenced by variations in emission sources and meteorological parameters (wind speed, relative humidity, temperature, solar radiation and boundary layer height) between day and night. Carbon monoxide correlates positively with Nacc in all seasons (R2 ≥ 0.5) as fossil fuel emission is a predominant source for gases and particles in the study environment. These quantitative results on seasonal variations of nano particles and air pollutants together with the knowledge on seasonal variations in meteorological parameters and atmospheric dynamics provide a foundation which can positively contribute better to the urban planning and devising mitigation measures aimed at improving air quality and public health.

International airport emissions and their impact on local air quality: chemical speciation of ambient aerosols at Madrid–Barajas Airport during the AVIATOR campaign

Abstract. Madrid–Barajas Airport (MAD) is the fourth-busiest airport in Europe. The aerosol chemical composition and the concentrations of other key pollutants were measured at the airport perimeter during October 2021 to assess the impact of airport emissions on local air quality. A high-fidelity ambient instrumentation system was deployed at Madrid–Barajas Airport to measure the following: concentrations of organic aerosols (with their composition), black carbon (eBC), carbon dioxide (CO2), carbon monoxide (CO), nitrogen dioxide (NOx), sulfur dioxide (SO2), particulate matter (PM2.5, PM10), total hydrocarbon (THC), and total particle number. The average concentrations of eBC, NOx, SO2, PM2.5, PM10, CO, and THC at the airport for the entire campaign were 1.07 µg m−3, 22.7 µg m−3, 4.10 µg m−3, 9.35 µg m−3, 16.43 µg m−3, 0.23 mg m−3, and 2.30 mg m−3, respectively. The source apportionment analysis of the non-refractory organic aerosol (OA) using positive matrix factorisation (PMF) allowed us to discriminate between different sources of pollution, namely less oxidised oxygenated organic aerosol (LO-OOA), alkane organic aerosol (AlkOA), and more oxidised oxygenated organic aerosol (MO-OOA). The results showed that LO-OOA and MO-OOA account for more than 80 % of the total organic particle mass measured near the runway. Trace gases correlate better with the AlkOA factor than LO-OOA and MO-OOA, indicating that AlkOA is mainly related to primary combustion emissions. Bivariate polar plots were used for pollutant source identification. Significantly higher concentrations of the obtained factors were observed at low wind speeds (<3 m s−1) from the southwest, where two of the runways and all terminals are located. Higher SO2/NOx and CO/eBC ratios were observed when the winds originated from the northeast, where the two northern runways are located. These elevated ratios are attributed to the aircraft activity being the major pollutant source in the northeast area.

Characterization, sources, and formation processes of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls in PM2.5 aerosols in New Delhi

Daytime and nighttime fine aerosol (PM2.5) samples were collected during a heavy pollution episode in November 2020, January 2021, and also during clean event (August 2020) in New Delhi. These samples (n = 20) were analyzed for water-soluble dicarboxylic acids (diacids) and related compounds, carbonaceous components, and inorganic ions to identify their sources and atmospheric processing in different episodes/seasons. Among the measured organics, oxalic acid (C2) was found to be the most abundant species followed by terephthalic (tPh), succinic (C4), phthalic (Ph), and azelaic (C9) acids. Such high abundance of tPh were different from those in other Asian cities where C3 is generally the second or third dominant species. tPh very well correlated with OC, Cl− and K+, indicating combustion of biomass and plastic-containing waste may be the possible sources. Significant high contents of diacids, oxoacids, and dicarbonyls were observed during heavy pollution episode, implying an enhanced emission and/or atmospheric processing of these species. Additionally, two important secondary formation pathways for C2 diacid were discussed in New Delhi, i.e. (i) biomass burning derived (biogenic) volatile organic precursors lead to formation of C2 diacid through transformation of oxoacids and dicarbonyls by oxidation, and (ii) oxidative degradation of the unsaturated fatty acids results in formation of C5 and C4 which subsequently decompose to C2 diacid. This study demonstrated that both primary emissions in clean event and secondary production during polluted event are important sources of aerosols in New Delhi.

Improving HONO Simulations and Evaluating Its Impacts on Secondary Pollution in the Yangtze River Delta Region, China

AbstractSecondary air pollution, especially ozone (O3) and secondary aerosols, are emerging air quality challenges confronting China. Nitrous acid (HONO), as the predominant source of hydroxyl radicals (OH), are acknowledged to be essential for secondary pollution. However, HONO concentrations are usually underestimated by current air quality models due to the inadequate representations of its sources. In the present study, we revised the Weather Research and Forecasting & Chemistry (WRF‐Chem) model by incorporating additional HONO sources, including primary emissions, photo‐/dark oxidation of NOx, heterogeneous uptake of NO2 on surfaces, and nitrate photolysis. By combining in‐situ measurements in the Yangtze River Delta (YRD) region, we found the improved model show much better performance on HONO simulation and is capable of reproducing observed high concentrations. The source‐oriented method is employed to quantitatively understand the relative importance of various processes, which showed that heterogeneous NO2 uptake on the ground surface was the major contributor to HONO formation in urban areas. Comparatively, photo‐oxidation of NOx is a main contributor in rural areas. The introduction of multiple sources of HONO led to an apparent increase in OH and hydroperoxyl (HO2) radicals. The promoted HO2 levels further increased diurnal O3 concentration by 4.5–12.9 ppb, while secondary inorganic and organic concentrations were also increased by 14%–32% during a typical secondary pollution event. The improved description of HONO emission and formation in the model substantially narrowed the gaps between simulations and observations, highlighting the great importance in understanding and numerical representations of HONO in secondary pollution study.

Selection of track form in railway tunnel from a life cycle analysis perspective

AbstractThe use of greenhouse gas (GHG) emissions as a criterion for decision-making within the rail industry is increasing. The demand for considering this criterion affects the type of decision models acceptable by railway infrastructure managers in the planning, construction, and maintenance of railway assets. The total amount of GHG emitted from a track solution in tunnels during its service life depends on the track form (i.e., ballasted track or ballastless track), the type of construction, maintenance machines used, current traffic profile, and tunnel length. However, the development in the design of ballastless track systems during recent decades to make them environmentally friendly motivates infrastructure managers to rethink and consider the use of the system. This study examines the effect of several design and maintenance factors not adequately addressed in previous research. These factors are (i) the modulus of elasticity of track support affecting the design of track forms, (ii) differences in maintenance and renewal required for track forms in the corresponding line condition, and (iii) recent developments in optimizing the environmental impact of ballastless tracks. The GHG emissions, represented by life cycle carbon dioxide equivalent (CO2e) emissions, are calculated using the climate impact software developed by the Swedish Transport Administration Trafikverket. The result is compared with the estimated emission from the conventional ballasted tracks. The method proposed in this paper is applied in a case study to study the effect of applying the optimized ballastless track system Rheda 2000® in a railway tunnel (the Hallsberg-Stenkumla tunnel) as part of a new line project in Sweden. The model applied in the study is an integral part of an integrated decision support system for effectively selecting track solutions from a lifecycle perspective. The study´s findings are: (i) the life cycle CO2 equivalent emissions by a ballastless track during its life cycle are 10% lower than that of the ballasted track, (ii) the primary total emission driver for both track form solutions is the emissions generated at the manufacturing of rails. (iii) the second important emission factor for the ballasted track solution is the emission from the renewal of the track form during its life cycle, and (iv) the second important emission factor for the ballastless track solution is concrete manufacturing.

A Hot Mess: The Rich and Complex Soft Emitting Regions Surrounding the Reflection Dominated Flaring Central Engine of Mrk 1239

Previous X-ray works on Mrk 1239 have revealed a complex narrow-line Seyfert 1 that exhibits substantial absorption and strong emission from both collisionally ionized and photoionized plasmas. Here, we report on deep-pointed observations with XMM-Newton and NuSTAR, along with Swift monitoring, to understand the 0.3–30 keV continuum emission and the central engine geometry. A strong X-ray flare, where the AGN brightens by a factor of 5 in ∼30 ks, is captured between 4 and 30 keV and can be attributed to a brightening of the primary continuum. However, the lack of any variability below ∼3 keV on long or short timescales requires complete absorption of the AGN continuum with a neutral medium of column density ∼1023.5 cm−2. The timing and spectral properties are consistent with a blurred reflection interpretation for the primary emission. The variability and presence of a Compton hump disfavors ionized partial covering. The neutral absorber, if outflowing, could be crashing into the surrounding medium and interstellar medium to produce the low-energy continuum and collisionally ionized emission. Scattered emission off the inner torus could produce the photoionized emission. The intricate scenario is demanded by the data and highlights the complexity of the environment that is normally invisible when overwhelmed by the AGN continuum. Objects like Mrk 1239 serve as important sources for unveiling the interface between the AGN and host galaxy environments.

Optimization of a PM2.5 automatic monitoring network based on the modeling approach – A case study in Long An province, Vietnam

Abstract Currently, fine particulate matter (PM2.5) pollution is one of the well-recognized serious environmental health risks. In particular, PM2.5 has remarkably impacted the human respiratory, cardiovascular, and circulatory systems. Vietnam has frequently ranked among the countries with the highest annual mean PM2.5 levels in Southeast Asia and worldwide. Thus, building a real-time continuous ambient PM2.5 monitoring network is an important environmental management tool to reduce health effects attributable to PM2.5 exposure. Nevertheless, measurement locations of an air quality monitoring (AQM) network depend strongly on meteorological conditions in the area and sensitivity to local primary emission sources, which significantly determines the AQM network’s operational efficiency. This study aims to estimate and optimize outdoor PM2.5 monitoring sites of an automatic air quality monitoring (AAQM) network using a system of low-cost sensors in Long An province, based on the spatio-temporal distribution assessment results of PM2.5 concentrations from WRF (Weather Research and Forecasting Model)/CMAQ (the Community Multiscale Air Quality) models. The prominent study outcomes have shown that the 2018 average PM2.5 concentration in Long An province exceeded the threshold of QCVN 05:2023/BTNMT (25 μg/m3) from 5.6 to 7.9 times. Moreover, this study has proposed four optimal monitoring sites (AQ1, AQ2, AQ3, and AQ4) for the automatically real-time PM2.5 observation in the areas of Tan An City, Can Giuoc District, the ring roads 3 and 4, and Kien Tuong Town. The study has provided an important scientific basis and support for local air quality management activities; furthermore, the newly proposed monitoring locations will complement the province’s periodic monitoring program towards 2025.

Assessing the nonlinearity of wintertime PM2.5 formation in response to precursor emission changes in North China with the adjoint method

Abstract While China’s clean air actions implemented since 2013 have been effective in mitigating PM2.5 air pollution, the large emission reductions during the COVID-19 lockdown period in early 2020 did not similarly alleviate PM2.5 pollution in North China, reflecting a distinct nonlinear chemical response of PM2.5 formation to emission changes. Here we apply emission-concentration relationships for PM2.5 diagnosed using the adjoint approach to quantitatively assess how chemical nonlinearity affects PM2.5 over Beijing in February 2020 in response to two emission reduction scenarios: the COVID-19 lockdown and 2013–2017 emission controls. We find that, in the absence of chemical nonlinearity, the COVID-19 lockdown would decrease PM2.5 in Beijing by 17.9 μg m–3, and the 2013–2017 emission controls resulted in a larger decrease of 54.2 μg m–3 because of greater reductions of SO2 and primary aerosol emissions. Chemical nonlinearity offset the decrease for Beijing PM2.5 by 3.4 μg m–3 during the lockdown due to enhanced sensitivity of aerosol nitrate to NO x emissions, but enhanced the efficiency of 2013–2017 emission controls by 11.9 μg m–3 due to the weakened heterogeneous reaction of sulfate. Such nonlinear chemical effects are important to estimate and consider when designing or assessing air pollution control strategies.

МОДЕЛЮВАННЯ ЕНЕРГОЕФЕКТИВНОСТІ ЖИТЛОВОЇ БУДІВЛІ ЗА УМОВ РІЗНИХ ДЖЕРЕЛ ТЕПЛОВОЇ ЕНЕРГІЇ

The paper presents the results of modeling the process of energy consumption in public, residential, and commercial buildings as a result of the use of various sources of thermal energy. Buildings with such energy sources as: a) a low-temperature gas boiler with a capacity of up to 120 kW for the needs of heat supply of a residential building and freon air conditioning systems for the needs of cooling the building; b) a gas condensing boiler with a thermal capacity of up to 120 kW with a temperature regime of 55/45°C for heat supply and freon air conditioning systems for cooling; c) reversible heat pumping unit of the “ground-water” type with a temperature regime of 35/28°C for the needs of the heating and cooling system and a reversible heat pumping machine with a regime of 55/45°C for the needs of hot water supply; d) a reversible air-to-air heat pump for heating and cooling systems and electric boilers for hot water supply; e) a biomass solid fuel boiler with manual fuel loading with a heat output of more than 100 kW for heat supply and freon systems for cooling; f) a fuel pellet boiler with automatic mechanized fuel loading with a heat output of more than 100 kW for building heating and cooling and freon systems for cooling; g) centralized heating system of the building. The results of calculations of the specific primary energy consumption and specific greenhouse gas emissions for each of the above heat sources are presented. It is established that biomass boilers have the lowest values of primary energy consumption and specific greenhouse gas emissions. The lowest efficiency is achieved by a district heating system with a centralized energy source. The modeling was conducted for the climatic conditions of Vinnytsia. At the same time, the disadvantage of using solid fuel boilers is the limitation of their use in densely populated areas, which is explained by the complexity of flue gas cleaning and regular biomass supply. Therefore, it has been determined that the most efficient source of thermal energy for buildings of various types to achieve the standardized energy efficiency indicators is a ground-to-water heat pump system. This installation, along with providing buildings with thermal energy, allows for cooling in the warm season, operating in reverse mode.

Temporal Refinement of Major Primary Air Pollutant Emissions Based on Electric Power Big Data: A Case of the Cement Industry in Tangshan City

Temporal Refinement of Major Primary Air Pollutant Emissions Based on Electric Power Big Data: A Case of the Cement Industry in Tangshan City

Investigation into the nocturnal ozone in a typical industrial city in North China Plain, China

Ozone (O3) concentrations usually peak at midday by photochemical reactions and gradually decline after sunset due to chemical destruction and dry deposition. However, an increase in the frequency of elevated nocturnal ozone enhancement (NOE) and high nocturnal ozone value (HNOV) has been frequently observed in urban areas of eastern China, but the reasons are not well understood. In this study, taking a typical industrial city, ZiBo as a case study, we analyzed the trends, characteristics, and causes of the NOE and HNOV events in historical years by combining observations and model simulations. During the warm season (April–September) of 2017–2023, HNOV events are accompanied by low humidity, high temperature, large friction velocity, and a high boundary layer (52 days in total), whereas NOE events coincide with increases in humidity, wind speed, friction velocity, and boundary layer height (141 days in total). During the HNOV and NOE events, the nighttime average concentrations of Ox were 77 ± 7 and 12 ± 6 μg m−3 higher than the non-nocturnal O3 period, indicating enhanced atmospheric oxidizing capacity during nighttime. The modeling results indicate that both the HNOV and NOE events were mainly driven by vertical mixing and regional transport. We selected a typical period with high O3 pollution and frequent NOE and HNOV events to conduct the modeling study. Three typical nocturnal O3 events are identified: Case I was mainly driven by horizontal transport; while in the two subsequent cases, the vertical transport contribution was 80 μg m−3 h−1 (20:00 LT on June 21, 2021) and 35 μg m−3 h−1 (02:00 LT on June 26, 2021), respectively. Our study reveals that the O3 pollution in industrial cities has been extending to nighttime, primarily attributed to vertical mixing and horizontal transport within the boundary layer. This highlights the critical role of implementing regional joint control action to reduce primary emissions and eliminate residual ozone.

Hydrogen Blending in Natural Gas Grid: Energy, Environmental, and Economic Implications in the Residential Sector

The forthcoming implementation of national policies towards hydrogen blending into the natural gas grid will affect the technical and economic parameters that must be taken into account in the design of building heating systems. This study evaluates the implications of using hydrogen-enriched natural gas (H2NG) blends in condensing boilers and Gas Adsorption Heat Pumps (GAHPs) in a residential building in Rome, Italy. The analysis considers several parameters, including non-renewable primary energy consumption, CO2 emissions, Levelized Cost of Heat (LCOH), and Carbon Abatement Cost (CAC). The results show that a 30% hydrogen blend achieves a primary energy consumption reduction of 12.05% and 11.19% in boilers and GAHPs, respectively. The presence of hydrogen in the mixture exerts a more pronounced influence on the reduction in fossil primary energy and CO2 emissions in condensing boilers, as it enhances combustion efficiency. The GAHP system turns out to be more cost-effective due to its higher efficiency. At current hydrogen costs, the LCOH of both technologies increases as the volume fraction of hydrogen increases. The forthcoming cost reduction in hydrogen will reduce the LCOH and the decarbonization cost for both technologies. At low hydrogen prices, the CAC for boilers is lower than for GAHPs; therefore, replacing boilers with other gas technologies rather than electric heat pumps increases the risk of creating stranded assets. In conclusion, blending hydrogen into the gas grid can be a useful policy to reduce emissions from the overall natural gas consumption during the process of end-use electrification, while stimulating the development of a hydrogen economy.

Characteristics of life-cycle carbon dioxide emissions of arterial highway maintenance and the influencing factors

With the focus of highway development transitioning from construction to maintenance, a comprehensive understanding of the characteristics and influencing factors of carbon dioxide (CO2) emissions from highway maintenance activities is crucial for formulating effective strategies to promote the low-carbon development of road infrastructure. However, the quantitative relationships between CO2 emissions from highway maintenance schemes and factors such as pavement deterioration, traffic volume, and road grade remain unclear owing to a lack of comprehensive, multi-category, and real data. Using real maintenance data from 340 arterial highway segments in China, this study conducts the life cycle assessment (LCA) to estimate CO2 emissions from maintenance activities and examines the primary emission sources among various structural layers and materials. Furthermore, multiple linear regression (MLR) analysis is conducted to investigate the impact of traffic volume, road grade, and pavement deterioration on CO2 emissions from maintenance projects, and factors influencing the early-stage degradation of pavement performance. The results demonstrate that average CO2 emissions from heavy rehabilitation projects are 6.97 times higher than those from medium rehabilitation projects. Emissions from heavy rehabilitation projects exhibit a significantly negative linear relationship with the riding quality index (RQI) before maintenance (p < 0.05), and emissions from medium rehabilitation projects show a significant negative linear relationship with the pavement condition index (PCI) before maintenance (p < 0.05). Emissions from heavy and medium rehabilitation projects are significantly positively correlated with heavy vehicle traffic volume before maintenance (p < 0.05). Moreover, the early-stage degradation of PCI after heavy rehabilitation and RQI after medium rehabilitation exhibit significantly negative linear relationships with their respective indicators before maintenance (p < 0.05). The early-stage degradation of RQI after heavy rehabilitation is significantly positively correlated with CO2 emissions from the base course and cushion layers (p < 0.05). The findings emphasize that timely maintenance and reduction of CO2 emissions from asphalt mixing equipment are essential for mitigating emissions from road maintenance. This study offers valuable insights for advancing the low-carbon development of highways in temperate regions.

Understanding the Social Determinants of Household Carbon Emissions for Carbon Mitigation Policies: The Case of Mersin, Turkey

Households are the main consumer-side source of carbon emissions. In Europe, consumer-based CO2 consumption per capita fell from 10.8 tons to 7.8 tons between 1990 and 2022, but in Turkey, the same data showed a rise from 4 tons to 5 tons. Strategies to reduce carbon emissions have recently shifted their focus from the production side to the consumption side. However, because different social segments have varying levels of price sensitivity and differing levels of necessity regarding consuming different items, a simple tax policy only targeting the consumption side is doomed to fail. This has prompted a discussion of the factors influencing carbon emissions on the consumption side and how those factors affect the amount of emissions. This study aims to identify the social determinants affecting household carbon emission levels and to demonstrate that such differences play an important role in effective and efficient carbon emission reduction strategies. In this case study, an appropriate testing method was used to test whether there are significant differences in dependent variables (carbon emissions) between categories of independent variables (the social determinants of households). As our literature review demonstrates, the social determinants of households and the local context were found to have an impact on carbon emissions in the case study. Nevertheless, we found that the degree of association lessens when the relationship between the dependent variables and the independent variables is re-evaluated while controlling for income level. Consequently, it may be concluded that the primary element influencing carbon emissions is income. In our field study, on the other hand, poverty stood out as another important factor affecting the level of carbon emissions. Poverty affects total household carbon emissions in two different ways, causing both carbon-intensive consumer goods and household appliances with low energy efficiency to be preferred because they are cheap to purchase. Therefore, the fight against poverty should be recognized as an important component of carbon reduction policies in Turkey, and the issue of environmental justice should not be ignored, because we know that 30% of the population was living in poverty (compared to the other 70% receiving the national median income) in 2022.