Abstract Heavy-duty vehicles (including non-road mobile machinery, eg excavators), aircrafts and ships are contributing significantly to emissions of green-house gases and health-relevant air pollutants, such as fine airborne particulate matter (PM2.5) as well as emerging pollutants. For decarbonization of the sector, several new fuels, ranging from hydrogen via ammonia to synthetic eFuels are considered. An important question is how these potential new fuels will influence emissions of air pollutants and climate relevant compounds. LowC will address if these new fuels for high-power engines have an impact on the emissions of air pollutants and climate-drivers, considering also upstream emissions and secondary pollutants formed under different atmospheric conditions (daytime photochemical aging or night-time atmospheric radical chemistry). LowC will apply a series of state-of-the-art technologies to generate and characterize the emissions and assess the effects in lung cell models. The toxicological testing will be applied in a tiered manner (screening and in-depth verification), in line with visions of Toxicity Testing in the 21st Century. Emission data, including regulated and emerging pollutants, will feed into integrated assessment and atmospheric transport models, currently used to underpin EU policy and the Zero Pollution Action Plan, to assess impacts on the EU environmental policy objectives. Finally, LowC will evaluate health and environmental impacts and provide guidance and recommendations to ensure that solutions to reduce CO2 emissions and prevent climate change are safe and sustainable. The work is supported by the European Union’s Horizon Europe research and innovation program under Grant Agreement No. 101192913.

Particulate matter (PM) from marine traffic interacts with solar radiation and clouds, ultimately influencing Earth's radiative balance. Ships operated with conventional fossil fuel oils emit light-absorbing carbonaceous PM that offsets aerosol-driven cooling and can even exert a net positive radiative forcing, i.e. warming effect. Radiative properties of PM are possibly further altered by atmospheric aging processes, the effects of which are not fully understood. We present black carbon (BC) emission factors (EF) and optical properties of fresh and photochemically aged particle emissions from a marine engine, operated using low-sulfur heavy fuel oil (LS-HFO) and marine gas oil (MGO), complying with recent maritime sulfur regulations by the International Maritime Organization (IMO). The fresh particle emissions comprised mostly BC, with average BC EFs of 144 and 43.2 mg/kWh for LS-HFO and MGO, respectively. Light absorption was mostly attributed to BC in particles from both fuels, with absorption & Aring;ngstr & ouml;m exponent (AAE, 370 to 880 nm) values 0.9-1.0 (interquartile range), and 870 nm single scattering albedo (SSA) values 0.15-0.24 during the full cycles. Fresh LS-HFO emissions exhibited lower SSA values than those of high-sulfur fuels reported in literature, primarily associated with reduced sulfate emissions. Photochemical aging led to an absorption enhancement (Eabs) of 1.2-1.5 and an increase in SSA relative to fresh emissions, although SSA remained below 0.5, and the estimated direct radiative forcing effect stayed positive. Our results show that sulfur-compliant marine fuels can emit highly absorbing particles with an atmospheric warming potential, which is mostly maintained even after photochemical aging.

Ship emissions significantly impact both the environment and human health. To address these concerns, the International Maritime Organization has imposed restrictions on the sulfur content in marine fuels. Specifically, the fuel sulfur content (FSC) must be below 0.5% m/m globally and below 0.1% m/m in designated sulfur emission control areas. These regulations apply to a range of fuels including distillate diesel-like fuels and low-sulfur heavy fuel oils (HFOs). As a result, there has been a reduction in emissions, particularly sulfur oxides and particulate matter (PM). However, the relationship between FSC and the toxicity of ship emissions remains unclear. This study aimed to investigate how the physical and chemical properties of PM from a marine engine operating on five marine fuels with varying FSCs, influence toxicological outcomes. For this scope, the study assessed cytotoxic, genotoxic, mutagenic, and pro-inflammatory effects of the emitted particles using lung cell models. The involvement of intracellular reactive oxygen species and xenobiotic metabolism was also exanimated. The results showed that PM from the combustion of different fuels reduced cell viability and clonogenicity at the highest concentration. However, other toxicological outcomes, such as genotoxic potential, were more strongly associated with the polycyclic aromatic hydrocarbon content of the PM than with FSC. Notably, an aromatic-rich HFO with intermediate FSC induced a significant increase in gene mutation frequency and alterations of cellular processes. In conclusion, while reducing FSC is an important step in mitigating ship emissions, this study underscores the need for a comprehensive evaluation of fuel properties.

Sulfur dioxide pollution by ship emissions can be efficiently decreased by using exhaust gas scrubbers, yet particles can pass through the scrubber and be released into the atmosphere. Here, we studied the impact of using a wet scrubber on the composition of particle emissions, by single-particle analysis. At low engine loads, results show no significant changes in particle composition of metals, salts, and polycyclic aromatic hydrocarbons (PAH). At high engine loads, the scrubber reduced soot and PAH signatures about fourfold. Particles passing through the scrubber undergo minimal chemical changes, except for sulfate uptake. The cleaning effect of wet scrubbers is attributed to the removal of water-soluble gas-phase compounds, diffusion-dominated uptake of ultrafine particles, and wet deposition of coarse particles. The scrubber has little effect on reducing the health and environmental impacts of the remaining particles that pass through it. These emitted particles, primarily in the 60–200 nm size range, constitute a significant portion of the inhalable particle mass and have the potential for long-range transport.

The enforcement of global fuel sulfur content (FSC) regulations has significantly reduced SO2 and particulate matter (PM) emissions from ships. However, the impact of the International Maritime Organization's (IMO) sulfur reduction policy on gaseous hydrocarbon emissions, including volatile and intermediate volatility organic compounds (VOCs/IVOCs), remains underexplored. In this study, a 4-stroke single cylinder marine engine was operated using marine gas oil (MGO, FSC = 0.01%) and low-sulfur heavy fuel oil (LS-HFO, FSC = 0.5%) across various engine loads, ranging from 20 kW to a maximum of 80 kW. Emissions were photochemically aged in the oxidation flow reactor "PEAR," simulating an equivalent photochemical aging period from 1.4 +/- 0.2 to 4.6 +/- 0.8 days related to the OH exposure. Emission factors (EFs) of all targeted VOCs/IVOCs varied significantly, ranging from 20.0 +/- 2.5 to 180 +/- 20 mg kWh-1 and from 26.0 +/- 11.0 to 280 +/- 100 mg kWh-1 from a high (80 kW) to low engine load (20 kW) for MGO and LS-HFO, respectively. Monoaromatics dominated total fresh emissions for MGO (64%) and LS-HFO (76%), followed by alkanes. Naphthalene and alkylated naphthalene content declined more than monoaromatic and alkane content, thus changing the VOC/IVOC emission pattern after photochemical aging. Estimated SOA from targeted VOC/IVOC precursors accounted for 41% of the measured secondary organic aerosol (SOA) for MGO, while a lower contribution (34%) was observed for LS-HFO at 20 kW engine load, highlighting the role of unmeasured VOCs/IVOCs in SOA formation. Expanding the research on the effects of atmospheric aging on marine emissions will offer valuable insights into this underexplored area.

Emissions from ships significantly contribute to global air pollution, especially in coastal regions. Marine engines emit high levels of particulate matter (PM), which may contain toxic heavy metals depending on the fuel used. Current regulations on fuel sulphur content (FSC) permit the use of heavy fuel oils (HFOs) only with wet sulphur scrubbers, but do not regulate the PM and heavy metal content directly. This study examines emission factors (EFs) of heavy metals bound to PM2.5 from a maritime research engine operating on various fuels: marine gas oil (MGO), hydrotreated vegetable oil (HVO), ultra-low sulphur heavy fuel oil (ULS-HFOar), and high-sulphur HFOs (HFO 0.5 and HFO 2.2). The impact of wet scrubbing technology and engine load variations (20 kW, 40 kW, 60 kW, 80 kW) was also assessed. Results show that HFO fuels, both with and without scrubbers, produce significantly higher emissions of PM2.5, particle number (PN), and heavy metals compared to MGO, HVO, and ULS-HFOar. While wet scrubbers effectively reduced sulphur emissions, they had limited or no impact on PM2.5, PN, or metal emissions associated with particles. At engine loads of 20 kW and 60 kW, switching from HFO 2.2 to HFO 0.5-following IMO 2020 sulphur regulations-reduced PM2.5 emissions by 23 % and 28 %, respectively, and PN by 30 % and 58 %. Heavy metal emissions decreased dramatically by 74 % and 81 %. The findings underscore the urgent need for particulate emission regulations in marine shipping, akin to those for road traffic, to protect public health from fine and ultrafine particles. Use of HFO in sulphur emission control areas should be reconsidered, even with wet scrubbers, to better address health and environmental risks.

Ship traffic is known as an important contributor to air pollution. Regulations aimed at reducing sulfur oxide pollution by limiting the fuel sulfur content (FSC) may also decrease primary particulate matter (PM) emitted from ships. However, there is a knowledge gap regarding how the FSC affects secondary aerosol formation. The emissions from a research ship engine operated with either low sulfur heavy fuel oil (LS-HFO) (FSC = 0.5%) or marine gas oil (MGO) (FSC = 0.01%), were photochemically processed in the oxidation flow reactor “PEAR” to achieve an equivalent photochemical age between 0 and 9 days in the atmosphere. FSC was found to have no significant impact on secondary organic aerosol formation after 3 days of aging, at 1.7 ± 0.4 g/kg for MGO and 1.5 ± 0.4 g/kg for LS-HFO. Furthermore, the composition and oxidative pathways remained similar regardless of FSC. However, because of the higher secondary SO4 formation and primary aerosol emissions, LS-HFO had significantly higher total PM than MGO.

Aviation is an important source of urban air pollution, but the impacts of photochemical processing on the exhaust emissions remain insufficiently characterized. Here, the physical-chemical properties of fresh and photochemically aged emissions from a laboratory-scale jet engine burner operated with JP-8 kerosene were studied in detail with a range of online and offline methods. The fresh emissions contained high amounts of organic matter present predominantly in the gaseous phase. Photochemical aging in an oxidation flow reactor caused substantial formation of oxidized organic aerosol, increasing the particle mass approximately 300-fold. During aging, aromatic hydrocarbons and alkanes in the gas-phase decayed, while gas-phase oxidation products, such as small carbonyls and oxygenated aromatics, increased. The composition of organic matter became more complex by photochemical processing, with the average particulate carbon oxidation state increasingly growing throughout the addressed exposure range (equivalent to 0.2 to 7 d in the atmosphere) with a Delta H:C/Delta O:C slope of -0.54. Simultaneously, the near-UV wavelength absorption by the particles increased due to enhanced particulate mass. The imaginary refractory indices of organic particulate matter were 0.0071 and 0.00013 at the wavelength of 520 nm for the fresh and photochemically processed particles, respectively, indicating secondary production of weakly absorbing brown carbon. The direct radiative forcing by the exhaust particles was estimated by a Mie model, which revealed a prominent shift from a warming to cooling climate effect upon photochemical aging. The results highlight the importance of considering secondary aerosol formation when assessing the environmental impacts of aviation.

Sulphur Emission Control Areas (SECAs), mandated by the International Maritime Organization (IMO), regulate fuel sulphur content (FSC) to mitigate the environmental and health impact of shipping emissions in coastal areas. Currently, FSC is limited to 0.1% (w/w) within and 0.5% (w/w) outside SECAs, with exceptions for ships employing wet sulphur scrubbers. These scrubbers enable vessels using non-compliant fuels such as high-sulphur heavy fuel oils (HFOs) to enter SECAs. However, while sulphur reduction via scrubbers is effective, their efficiency in capturing other potentially harmful gases remains uncertain. Moreover, emerging compliant fuels like highly aromatic fuels or low-sulphur blends lack characterisation and may pose risks. Over three years, we assessed emissions from an experimental marine engine at 25% and 75% load, representative of manoeuvring and cruising, respectively. First, characterizing emissions from five different compliant and non-compliant fuels (marine gas oil MGO, hydro-treated vegetable oil HVO, high-, low- and ultra-low sulphur HFOs), we calculated emission factors (EF). Then, the wet scrubber gas-phase capture efficiency was measured using compliant and non-compliant HFOs. NOx EF varied among fuels (5200-19700 mg/kWh), with limited scrubber reduction. CO (EF 750-13700 mg/kWh) and hydrocarbons (HC; EF 122-1851 mg/kWh) showed also insufficient abatement. Carcinogenic benzene was notably higher at 25% load and about an order of magnitude higher with HFOs compared to MGO and HVO, with no observed scrubber reduction. In contrast, carbonyls such as carcinogenic formaldehyde and acetaldehyde, acting as ozone precursors, were effectively scrubbed due to their polarity and water solubility. The ozone formation potential (OFP) of all fuels was examined. Significant EF differences between fuels and engine loads were observed, with the wet scrubber providing limited or no reduction of gaseous emissions. We suggest enhanced regulations and emission abatements in the marine sector to mitigate gaseous pollutants harmful to human health and the environment.

We investigated the fuel-dependent single-particle mass spectrometric signatures of polycyclic aromatic hydrocarbons (PAHs) from the emissions of a research ship engine operating on marine gas oil (MGO), hydrotreated vegetable oil (HVO) and two heavy fuel oils (HFO), one with compliant and one with non-compliant fuel sulfur content. The PAH patterns are only slightly affected by the engine load and particle size, and contain sufficient dissimilarity to discriminate between the marine fuels used in our laboratory study. Hydrotreated vegetable oil (HVO) produced only weak PAH signals, supporting that fuel residues, rather than combustion conditions, determine the PAH emissions. The imprint of the fuel in the resulting PAH signatures, combined with novel single-particle characterization capabilities for inorganic and organic components, opens up new opportunities for source apportionment and air pollution monitoring. The approach is independent of metals, the traditional markers of ship emissions, which are becoming less important as new emission control policies are implemented and fuels become more diverse. Single-particle mass spectrometric information on PAHs in ship emissions can indicate the type of fuel used.

Ship traffic substantially contributes to air pollution, thus affecting climate and human health. Recently introduced regulations by the International Maritime Organization (IMO) on the fuel sulfur content (FSC) caused a shift in marine fuel onsumption from heavy fuel oils (HFO) to diesel-like distillate fuels, but also to alternative hybrid fuels and the operation of sulfur scrubbers. Using multi-wavelength thermal-optical carbon analysis (MW-TOCA), our study provides emission factors (EF) of carbonaceous aerosol particles and link the fuel composition to features observed in the soot microstructure, which may be exploited in online monitoring by single-particle mass spectrometry (SPMS). Particulate matter from distillate fuels absorbs stronger light of the visible UV and near-infrared range than HFO. However, Simple Forcing Efficiency (SFE) of absorption weighted by EF of total carbon compensated the effect, leading to a net reduction by >50% when changing form HFO to distillate fuels.

A novel marker approach can detect individual particles from ship emissions in the atmosphere via resonant ionization of aromatic hydrocarbons.

Humic-like substances (HULIS), known for their substantial impact on the atmosphere, are identified in marine diesel engine emissions obtained from five different fuels at two engine loads simulating real world scenarios as well as the application of wet sulfur scrubbers. The HULIS chemical composition is characterized by electrospray ionization (ESI) ultrahigh resolution mass spectrometry and shown to contain partially oxidized alkylated polycyclic aromatic compounds as well as partially oxidized aliphatic compounds, both including abundant nitrogen- and sulfur-containing species, and clearly different to HULIS emitted from biomass burning. Fuel properties such as sulfur content and aromaticity as well as the fuel combustion efficiency and engine mode are reflected in the observed HULIS composition. When the marine diesel engine is operated below the optimum engine settings, e.g., during maneuvering in harbors, HULIS-C emission factors are increased (262-893 mg kg(-1)), and a higher number of HULIS with a shift toward lower degree of oxidation and higher aromaticity is detected. Additionally, more aromatic and aliphatic CHOS compounds in HULIS were detected, especially for high-sulfur fuel combustion. The application of wet sulfur scrubbers decreased the HULIS-C emission factors by 4-49% but also led to the formation of new HULIS compounds. Overall, our results suggest the consideration of marine diesel engines as a relevant regional source of HULIS emissions.

The emissions of marine diesel engines have gained both global and regional attentions because of their impact on human health and climate change. To reduce ship emissions, the International Maritime Organization capped the fuel sulfur content of marine fuels. Consequently, either low-sulfur fuels or additional exhaust gas cleaning devices for the reduction in sulfur dioxide (SO2) emissions became mandatory. Although a wet scrubber reduces the amount of SO2 significantly, there is still a need to consider the reduction in particle emissions directly. We present data on the particle removal efficiency of a scrubber regarding particle number and mass concentration with different marine fuel types, marine gas oil, and two heavy fuel oils (HFOs). An open-loop sulfur scrubber was installed in the exhaust line of a marine diesel test engine. Fine particulate matter was comprehensively characterized in terms of its physical and chemical properties. The wet scrubber led up to a 40% reduction in particle number, whereas a reduction in particle mass emissions was not generally determined. We observed a shift in the size distribution by the scrubber to larger particle diameters when the engine was operated on conventional HFOs. The reduction in particle number concentrations and shift in particle size were caused by the coagulation of soot particles and formation/growing of sulfur-containing particles. Combining the scrubber with a wet electrostatic precipitator as an additional abatement system showed a reduction in particle number and mass emission factors by >98%. Therefore, the application of a wet scrubber for the after-treatment of marine fuel oil combustion will reduce SO2 emissions, but it does not substantially affect the number and mass concentration of respirable particulate matters. To reduce particle emission, the scrubber should be combined with additional abatement systems.

Current regulations of particulate matter (PM) based on ambient mass concentrations does not encompass source dependent variation in toxicity or the impact of high numbers of ultrafine PM (UFPs) which contribute little to total PM mass. UFPs may pose risks due to their small size and high number/surface area concentrations and propensity to penetrate tissue barriers and reach the circulation and secondary target organs. ULTRHAS (2021-2025) is a project funded under the EU’s Research and Innovation program Horizon 2020 (Grant Agreement No. 955390). The project will specifically address (i) the impact of different transport modes, fuel technologies and wear components, including atmospheric ageing processes, on the physicochemical characteristics of particulate and gaseous emissions; and how these processes and characteristics affects (ii) the biological responses leading to harmful effects in the lung and beyond by applying state-of-the-art emission measurement, exposure and toxicity-testing approaches under highly controlled laboratory conditions. ULTRHAS will (iii) rank the health hazards of different transport mode emissions and (iv) apply an advanced health impact assessment framework incorporating burden of disease methods to quantify baseline and policy scenario impacts for development and prioritization of mitigation measures; and (v) evaluate the future impact and acceptance of new policies on public health, taking into account social aspects. ULTRHAS aims to provide enhanced understanding of health threats posed by nanoparticles from different transport modes; optimize a framework for toxicity and hazard assessment of aerosols; provide guidance for prioritization of mitigation measures for future legislation on air pollutants.

The comprehensive chemical description of air pollution is a prerequisite for understanding atmospheric transformation processes and effects on climate and environmental health. In this study, a prototype vacuum photoionization Orbitrap mass spectrometer was evaluated for field-suitability by an online on-site investigation of emissions from a ship diesel engine. Despite remote measurements in a challenging environment, the mass spectrometric performance could fully be exploited. Due to the high resolution and mass accuracy in combination with resonance-enhanced multiphoton ionization, the aromatic hydrocarbon profile could selectively and sensitively be analyzed. Limitations from commonly deployed time-of-flight platforms could be overcome, allowing to unraveling the oxygen- and sulfur-containing compounds. Scan-by-scan evaluation of the online data revealed no shift in exact m/z, assignment statistics with root mean square error (RMSE) below 0.2 ppm, continuous high-resolution capabilities, and good isotopic profile matches. Emissions from three different feed fuels were investigated, namely, diesel, heavy fuel oil (HFO), and very low sulfur fuel oil (VLSFO). Regulations mainly concern the fuel sulfur content, and thus, exhaust gas treatment or new emerging fuels, such as the cycle-oil-based VLSFO, can legally be applied. Unfortunately, despite lower CHS-class emissions, a substantial amount of PAHs is emitted by the VLSFO with higher aromaticity compared to the HFO. Hence, legislative measures might need to take further chemical criteria into account.

Regarding the entire drive train using a combustion engine today is close-coupled to an exhaust gas aftertreatment (EAT) system. Only by using an efficient EAT concept it is possible to attain highest conversion rates and fulfill the emission limits. In doing so it is not only necessary to match the limits for type approval and initial operation but also to guarantee compliance over the engines life time cycle.