Impact of SOx, NOx and NH3 emission reductions on PM2.5 concentrations across Europe: Hints for future measure development

Reducing biomass burning is key to decrease PM2.5 exposure in European cities

Throughout the world, ambient fine particulate matter (PM2.5) is the environmental factor that poses the greatest risk to health and most European citizens continue to be exposed to PM2.5 levels well above World Health Organization guidelines. Here we present a comprehensive PM2.5 modelling-based source allocation assessment in 708 urban areas in Europe. The results show that urban cores, together with their commuting zones, contribute an average of 22% to urban PM2.5 concentrations levels. The residential sector is the highest source sector in 56% of cities. Its average contribution to PM2.5 formation is 27%, with a cluster of cities in Northern Italy and Eastern Europe contributing to more than 50%. Industry, agriculture and road transport show average contributions of 18%, 17% and 14%, respectively. Most emissions from residential sectors are anthropogenic primary PM2.5 which includes a condensable fraction. Furthermore, anthropogenic primary PM2.5 represents the precursor with the highest contribution in most cities (72%), contributing an average of 35% to urban PM2.5 levels. Emissions of anthropogenic primary PM2.5 by the residential sector are almost entirely (with exceptions of few countries) due to biomass burning. These results suggest that the residential sector should be a key target of any policy to improve air quality and that climate policies promoting biomass as a climate-neutral fuel could have a detrimental effect on air quality. A more integrated approach to climate and air quality policy design is desirable.

Optimal reactive nitrogen control pathways identified for cost-effective PM2.5 mitigation in Europe

Excess reactive nitrogen (Nr), including nitrogen oxides (NO_x) and ammonia (NH₃), contributes strongly to fine particulate matter (PM_2.5) air pollution in Europe, posing challenges to public health. Designing cost-effective Nr control roadmaps for PM_2.5 mitigation requires considering both mitigation efficiencies and implementation costs. Here we identify optimal Nr control pathways for Europe by integrating emission estimations, air quality modeling, exposure-mortality modeling, Nr control experiments and cost data. We find that phasing out Nr emissions would reduce PM_2.5 by 2.3 ± 1.2 μg·m^-3 in Europe, helping many locations achieve the World Health Organization (WHO) guidelines and reducing PM_2.5-related premature deaths by almost 100 thousand in 2015. Low-ambition NH₃ controls have similar PM_2.5 mitigation efficiencies as NO_x in Eastern Europe, but are less effective in Western Europe until reductions exceed 40%. The efficiency for NH₃ controls increases at high-ambition reductions while NO_x slightly decreases. When costs are considered, strategies for both regions uniformly shift in favor of NH₃ controls, as NH₃ controls up to 50% remain 5-11 times more cost-effective than NO_x per unit PM_2.5 reduction, emphasizing the priority of NH₃ control policies for Europe.

Preparation of MoS2 Nanospheres using a Hydrothermal Method and Their Application as Ammonia Gas Sensors Based on Delay Line Surface Acoustic Wave Devices

An ammonia sensor based on a delay-line surface acoustic wave (SAW) device is developed in this study by coating the delay line area of the device with a nano-structured molybdenum disulfide (MoS₂) sensitive material. A SAW device of 122 MHz was designed and fabricated with a pair of interdigital transducers (IDTs) defined on a 128° y-cut LiNbO₃ substrate using photolithography technologies, and the aluminum IDT electrodes were deposited by a DC magnetron sputtering system. By adjusting the pH values of precursor solutions, molybdenum disulfide (MoS₂) nanospheres were prepared with various structures using a hydrothermal method. Finally, an NH₃ gas sensor with high sensitivity of 4878 Hz/ppm, operating at room temperature, was successfully obtained. The excellent sensitivity performance may be due to the efficient adsorption of NH₃ gas molecules on the surfaces of the nanoflower-like MoS₂, which has a larger specific surface area and provides more active sites, and results in a larger change in the resonant frequency of the device due to the mass loading effect.

A Source Apportionment and Emission Scenario Assessment of PM2.5- and O3-Related Health Impacts in G20 Countries

Exposure to air pollution is a leading risk factor for premature death globally; however, the complexity of its formation and the diversity of its sources can make it difficult to address. The Group of Twenty (G20) countries are a collection of the world's largest and most influential economies and are uniquely poised to take action to reduce the global health burden associated with air pollution. We present a framework capable of simultaneously identifying regional and sectoral sources of the health impacts associated with two air pollutants, fine particulate matter (PM_2.5) and ozone (O₃) in G20 countries; this framework is also used to assess the health impacts associated with emission reductions. This approach combines GEOS-Chem adjoint sensitivities, satellite-derived data, and a new framework designed to better characterize the non-linear relationship between O₃ exposures and nitrogen oxides emissions. From this approach, we estimate that a 50% reduction of land transportation emissions by 2040 would result in 251 thousand premature deaths avoided in G20 countries. These premature deaths would be attributable equally to reductions in PM_2.5 and O₃ exposure which make up 51% and 49% of the potential benefits, respectively. In our second application, we estimate that the energy generation related co-benefits associated with G20 countries staying on pace with their net-zero carbon dioxide targets would be 290 thousand premature deaths avoided in 2040; action by India (47%) would result in the most benefits of any country and a majority of these avoided deaths would be attributable to reductions in PM_2.5 exposure (68%).

Modelling the Impact of the Introduction of the EURO 6d-TEMP/6d Regulation for Light-Duty Vehicles on EU Air Quality

In this manuscript, we evaluated different emission scenarios for light-duty road transport to evaluate their impact on air quality in the EU, with a focus on a number of cities by means of the EMEP (European Monitoring and Evaluation Programme) modelling system. In addition to the reference case scenario, where exhaust emission factors from COPERT (Computer Programme to calculate Emissions from Road Transport) corresponding to the existing fleet were used, we also tested future potential scenarios considering: (a) all passenger cars and light commercial vehicles meet the EURO 6 emissions standard and EDGAR (Emission Database for Global Atmospheric research) EURO 6 emission factors; (b) all passenger cars and light commercial vehicles meet the EURO 6 emissions standard and real-world emission factors derived from actual Euro 6d-TEMP/6d vehicles. Results show how the replacement of old vehicles by newer ones with better emission control technologies can help improve air quality in the EU in terms of reductions in NO2 and PM2.5 concentrations. However, reduced NOx emissions in cities (as foreseen in the two scenarios analysed) will cause tropospheric O3 to increase.