Shipping Remains a Globally Significant Source of Anthropogenic PN Emissions Even after 2020 Sulfur Regulation

In vitro genotoxic and mutagenic potentials of combustion particles from marine fuels with different sulfur contents

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.

Ultrafine particles: Sources, toxicity, and deposition dynamics in the human respiratory tract -- experimental and computational approaches

Ultrafine particles (UFPs ≤ 100 nm) pose significant health risks, including respiratory and cardiovascular diseases, and cancer. This review consolidates main sources, toxicity, and exposure assessment approaches to elucidate the deposition dynamics of UFPswithin the human respiratory tract. Key factors influencing the deposition fraction (DF) are highlighted. Our findings indicate that the DF surpasses 50% for particles ≤50 nm and reaches up to 70% for particles ≤30 nm, impacting both adults and children. Vulnerable populations, such as children and individuals with pre-existing health conditions, are disproportionately affected, yet research focusing on these groups remains scarce. Methodological deficiencies, including high costs, simplifying assumptions, and computational constraints, challenge prediction accuracy. Experimental methods struggle to capture temporal fluctuations, while computational models fail to account for complex phenomena. Addressing these gaps is crucial for refining public health regulations and advancing nanomedicine. An improved understanding of UFPs dynamics will enhance protective measures and nanomedicine applications, particularly in targeted drug delivery and diagnostics. This review emphasizes the need for innovative experimental and computational methods to study UFPs deposition dynamics, ultimately advancing our understanding of UFPs' impact on human health.

In-depth characterization of exhaust particles performed on-board a modern cruise ship applying a scrubber

To comply with environmental regulations, ship operators may adopt exhaust after-treatment devices such as scrubbers or selective catalytic reduction (SCR). Beyond gaseous emission control, these technologies impact the exhaust particles emitted from marine engines to the atmosphere. This study characterizes comprehensively the chemical composition and physical properties of exhaust aerosol particles upstream and downstream a hybrid scrubber operating in open loop mode on-board a modern cruise ship. The study considers two engines, one equipped with SCR and both with scrubber, during engine load conditions of 75 % and 40 %, and the influence of marine gas oil (MGO) use in addition to heavy fuel oil (HFO). At least 4 different particle types were observed in the exhaust based on transmission electron microscopy (TEM) studies both upstream and downstream scrubber, and both scrubber and SCR affected the particle number size distribution (PSD). The geometric mean diameter (GMD) of the particles increased over scrubber both due to removal of nucleation mode particles and particle growth in the scrubber. The scrubber effectively decreased particle number (PN) and, also, non-volatile particles, but the effect depended on particle size and no significant decrease was observed in number of particles above 50 nm, typically comprising black carbon (BC) and in the case of HFO combustion, also asymmetrical metal containing particles. In addition to PN, concentrations of PAH compounds were reduced in the scrubber. The results may be further utilized when including the exhaust aerosol characteristics from ships applying scrubbers to emission inventories, as well as climate and air quality models.

Finer Particle Size Distribution and Potential Higher Toxicity of Elemental Carbon and Polycyclic Aromatic Hydrocarbons Emitted by Ships after Fuel Oil Quality Improvement

Ship emissions are a significant source of air pollution, and the primary policy to control is fuel oil quality improvement. However, the impact of this policy on particle size distribution and composition characteristics remains unclear. Measurements were conducted on nine different vessels (ocean-going vessels, coastal cargo ships, and inland cargo ships) to determine the impact of fuel upgrading (S < 0.1% m/m marine gas oil (MGO) vs S < 0.5% m/m heavy fuel oil (HFO)) on elemental carbon (EC) and polycyclic aromatic hydrocarbons (PAHs) emitted by ships. (1) Fuel improvement significantly reduced EC and PAH emission, by 31 ± 25 and 45 ± 38%, respectively. However, particle size distributions showed a trend toward finer particles, with the peak size decreasing from DP = 0.38-0.60 μm (HFO) to DP = 0.15-0.25 μm (MGO), and the emission factor of DP < 100 nm increased. (2) Changes in emission characteristics led to an increase in the toxicity of ultrafine particulate matter. (3) Ship types and engine conditions affected the EC and PAH particle size distributions. Inland ships have a more concentrated particle size distribution. Higher loads result in higher emissions. (4) The composition and engine conditions of fuel oils jointly affected pollutant formation mechanisms. MGO and HFO exhibited opposite EC emissions when emitting the same level of PAHs.

Statistical analysis and environmental impact of pre-existing particle growth events in a Northern Chinese coastal megacity: A 725-day study in 2010-2018

Pre-existing particles usually constitute the major fraction of atmospheric particles, except during some episodes in the presence of strong emissions and/or secondary generation of fresh particles. Previous case studies have investigated the growth of pre-existing particles and their potential environmental and climate impacts. However, there is limited knowledge about the statistical characteristics of these growth events and related effects. In this study, we examine pre-existing particle growth events using a large dataset (725 days from 2010 to 2018) collected at a coastal megacity in northern China. The occurrence frequency of pre-existing particle growth events was 12.4 % (90 out of 725 days). When these events were related to measured criteria air pollutants, no significant differences were found in PM2.5, SO2, NO2 and NO2 + O3 concentrations between periods with and without pre-existing particle growth events. These 90-day events can be further classified into two categories, i.e., Category 1, with 68 % of events representing the growth of pre-existing particles alone, and Category 2, with 32 % of events representing the simultaneous growth of pre-existing and newly formed particles. In Category 2, the growth rates of pre-existing particles and newly formed particles were close in 21 % of the cases, while pre-existing particles exhibited significantly larger growth rates in 69 % of the cases. Conversely, in 10 % of the cases, the growth rates of newly formed particles were larger. The different growth rate mechanisms were discussed in terms of the volatility of atmospheric condensation vapors. In addition, we present case studies on the impact of pre-existing particle growth on cloud condensation nuclei simultaneously measured, specifically considering the chemistry of condensation vapors and pre-existing particles.

Analysis of the uncertainty of the AIS-based bottom-up approach for estimating ship emissions

Although the AIS-based bottom-up approach has become the dominant method for estimating ship emissions, there are still inherent uncertainties due to the numerous complex factors involved. This paper aims to investigate the development process of the AIS-based bottom-up approach and identify the primary sources of uncertainty by conducting a systematic review of 29 articles published since 2015. The result shows three sources of uncertainty for estimating ship emissions, i.e., the acquisition and processing of AIS data, ship characteristic information and engine load calculation, and the determination of emission factors. This paper suggests that the accuracy of ship emission inventories can be improved by enhancing the reliability of datasets, uniformly defining engine load calculation formulas, and making more extensive measurements of local emissions to provide substantial support for ship emissions management and facilitate the development of more effective emission reduction strategies.

Particle lung deposited surface area (LDSAal) size distributions in different urban environments and geographical regions: Towards understanding of the PM2.5 dose-response

Recent studies indicate that monitoring only fine particulate matter (PM2.5) may not be enough to understand and tackle the health risk caused by particulate pollution. Health effects per unit PM2.5 seem to increase in countries with low PM2.5, but also near local pollution sources (e.g., traffic) within cities. The aim of this study is to understand the differences in the characteristics of lung-depositing particles in different geographical regions and urban environments. Particle lung deposited surface area (LDSAal) concentrations and size distributions, along with PM2.5, were compared with ambient measurement data from Finland, Germany, Czechia, Chile, and India, covering traffic sites, residential areas, airports, shipping, and industrial sites. In Finland (low PM2.5), LDSAal size distributions depended significantly on the urban environment and were mainly attributable to ultrafine particles (<100 nm). In Central Europe (moderate PM2.5), LDSAal was also dependent on the urban environment, but furthermore heavily influenced by the regional aerosol. In Chile and India (high PM2.5), LDSAal was mostly contributed by the regional aerosol despite that the measurements were done at busy traffic sites. The results indicate that the characteristics of lung-depositing particles vary significantly both within cities and between geographical regions. In addition, ratio between LDSAal and PM2.5 depended notably on the environment and the country, suggesting that LDSAal exposure per unit PM2.5 may be multiple times higher in areas having low PM2.5 compared to areas with continuously high PM2.5. These findings may partly explain why PM2.5 seems more toxic near local pollution sources and in areas with low PM2.5. Furthermore, performance of a typical sensor based LDSAal measurement is discussed and a new LDSAal2.5 notation indicating deposition region and particle size range is introduced. Overall, the study emphasizes the need for country-specific emission mitigation strategies, and the potential of LDSAal concentration as a health-relevant pollution metric.

The Solent Strait: Water quality trends within a heavily trafficked marine environment, 2000 to 2020

This study presents an important long-term historical analysis of water quality in an internationally crucial waterway (the Solent, Hampshire, UK), in the context of increasing adoption of open-loop Exhaust Gas Cleaning Systems by shipping. The pollutants studied were acidification (pH), zinc, and benzo [a] pyrene, alongside temperature. We compared baseline sites to locations likely to be impacted by pollution. The Solent's average water temperature is slightly increasing, with temperatures at wastewater sites significantly higher. Acidification suggests a complex story, with a highly significant small overall increase in pH during the study period but significantly different values at wastewater and port sites. Zn concentrations have significantly reduced but increased in enclosed waters such as marinas. BaP showed no long-term trend with values at marinas significantly and consistently higher. The findings provide valuable long-term background data and insights that can feed into the upcoming review of the European Union's Marine Strategy Framework Directive and ongoing discussions about the regulation of, and future monitoring and management strategies for coastal/marine waterways.

Marine Submicron Aerosols from the Gulf of Mexico: Polluted and Acidic with Rapid Production of Sulfate and Organosulfates

We measured submicron aerosols (PM₁) at a beachfront site in Texas in Spring 2021 to characterize the "background" aerosol chemical composition advecting into Texas and the factors controlling this composition. Observations show that marine "background" aerosols from the Gulf of Mexico were highly processed and acidic; sulfate was the most abundant component (on average 57% of total PM₁ mass), followed by organic material (26%). These chemical characteristics are similar to those observed at other marine locations globally. However, Gulf "background" aerosols were much more polluted; the average non-refractory (NR-) PM₁ mass concentration was 3-70 times higher than that observed in other clean marine atmospheres. Anthropogenic shipping emissions over the Gulf of Mexico explain 78.3% of the total measured "background" sulfate in the Gulf air. We frequently observed haze pollution in the air mass from the Gulf, with significantly elevated concentrations of sulfate, organosulfates, and secondary organic aerosol associated with sulfuric acid. Analysis suggests that aqueous oxidation of shipping emissions over the Gulf of Mexico by peroxides in the particles might potentially be an important pathway for the rapid production of acidic sulfate and organosulfates during the haze episodes under acidic conditions.

Development of a spectrum-based ship fuel sulfur content real-time evaluation method

Although maritime transport plays an essential role in the global economy, it inevitably imposes negative impacts on our living environment, especially for ships using fuel with high sulfur content. Nowadays, ship emission monitoring highly depends on manual inspection, which is time-consuming and labor-intensive. This study proposes a decision framework based on spectrum technology and the sulfur‑carbon ratio method to measure the ship fuel sulfur content. Specifically, after the Gaussian plume model optimization from four aspects, a multistep-based emission contribution evaluation method is developed to improve the evaluation accuracy. The proposed framework is validated by a suspected ship and a series of exempted ships from the Maritime Safety Administration in Nanjing, China. The validation results imply that the proposed framework has a certain enhancement in detection rate, evaluation accuracy and extensibility. It may provide an efficient and accurate supervision approach for the Maritime Safety Administration on ship fuel sulfur content measurement.

Ambient ultrafine particle (PM0.1): Sources, characteristics, measurements and exposure implications on human health

The problem of ultrafine particles (UFPs; PM_0.1) has been prevalent since the past decades. In addition to become easily inhaled by human respiratory system due to their ultrafine diameter (<100 nm), ambient UFPs possess various physicochemical properties which make it more toxic. These properties vary based on the emission source profile. The current development of UFPs studies is hindered by the problem of expensive instruments and the inexistence of standardized measurement method. This review provides detailed insights on ambient UFPs sources, physicochemical properties, measurements, and estimation models development. Implications on health impacts due to short-term and long-term exposure of ambient UFPs are also presented alongside the development progress of potentially low-cost UFPs sensors which can be used for future UFPs studies references. Current challenge and future outlook of ambient UFPs research are also discussed in this review. Based on the review results, ambient UFPs may originate from primary and secondary sources which include anthropogenic and natural activities. In addition to that, it is confirmed from various chemical content analysis that UFPs carry heavy metals, PAHs, BCs which are toxic in its nature. Measurement of ambient UFPs may be performed through stationary and mobile methods for environmental profiling and exposure assessment purposes. UFPs PNC estimation model (LUR) developed from measurement data could be deployed to support future epidemiological study of ambient UFPs. Low-cost sensors such as bipolar ion and ionization sensor from common smoke detector device may be further developed as affordable instrument to monitor ambient UFPs. Recent studies indicate that short-term exposure of UFPs can be associated with HRV change and increased cardiopulmonary effects. On the other hand, long-term UFPs exposure have positive association with COPD, CVD, CHF, pre-term birth, asthma, and also acute myocardial infarction cases.

Aerosol emissions from a marine diesel engine running on different fuels and effects of exhaust gas cleaning measures

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.

Study on the real-world emission characteristics of gaseous and particulate pollutants from an inland ship using a portable emission measurement system

The emissions of pollutants from inland ships endanger the urban environment and human health, deserving quantitative study to make reduction measurements to achieve clean emissions. In this study, the real-world gaseous emissions (CO, THC, SO₂, NOx) and particulate emissions including particle mass (PM) and particle number (PN) as well as the particle size distribution and particle compositions from an inland ship were investigated using a portable emission measurement system (PEMS) method. The results showed that the emission concentrations of CO, THC, PM and PN at departure and idling conditions were significantly higher than those at other conditions, while the emission concentrations of NOx and SO₂ at cruising condition were the highest. The particle size distribution always presented a bimodal distribution ranged at 40 nm and 200 nm respectively at different conditions and engine loads. The proportion of nucleation mode particles was the highest at departure condition, and a larger engine load resulted in a declined proportion of nucleation mode particles. The anions of the emitted particles mainly included nitrite ion (NO₂^-), nitrate ion (NO₃^-), sulfate ion (SO₄^2-), and cations mainly included ammonium ion (NH₄⁺), sodium ion (Na⁺) and potassium ion (K⁺). The main components of organic carbon (OC) in soot were OC1 and OC2, accounting for more than 80 %, while the main component of elemental carbon (EC) was EC2, accounting for 83.9 %. The emission factors based on fuel consumption of CO and THC were significantly higher at idling conditions than other conditions, and the emission factor of NOx was higher at cruising conditions, while the emission factors of PM and PN were higher at departure and idling conditions than other conditions.

Quantification and physical analysis of nanoparticle emissions from a marine engine using different fuels and a laboratory wet scrubber

A marine test-bed diesel engine was used to study how international fuel sulfur content (FSC) regulations and wet scrubbing can affect physical properties of submicron exhaust particles. Particle size distributions, particle number and mass emission factors as well as effective densities of particulate emissions were measured for three distillate fuels of varying FSC and a laboratory wet scrubber. While particle number concentrations were reduced by up to 9% when switching to low FSC fuels, wet scrubbing led to increased ultrafine particulate emissions (<30 nm). Exhaust processed through the scrubber was also found to have particles with greater effective densities, a result that directly contradicts the particulate characteristics of low FSC fuel emissions. The results demonstrate that alternative pathways to comply with marine FSC regulations can have opposing effects and thus may have very different implications for important atmospheric processes. The relevance for air quality, and the potential implications for cloud and climate interactions are discussed.

Real-world particle emissions and secondary aerosol formation from a diesel oxidation catalyst and scrubber equipped ship operating with two fuels in a SECA area

SO_x Emissions Control Areas (SECAs) have been established to reduce harmful effects of atmospheric sulfur. Typical technological changes for ships to conform with these regulations have included the combustion of low-sulfur fuels or installment of SO_x scrubbers. This paper presents experimental findings from high-end real-time measurements of gaseous and particulate pollutants onboard a Roll-on/Roll-off Passenger ship sailing inside a SECA equipped with a diesel oxidation catalyst (DOC) and a scrubber as the exhaust aftertreatment. The ship operates between two ports and switched off the SO_x scrubbing when approaching one of the ports and used low-sulfur fuel instead. Measurement results showed that the scrubber effectively reduced SO₂ concentrations with over 99% rate. In terms of fuel, the engine-out PM was higher for heavy fuel oil than for marine gas oil. During open sea cruising (65% load) the major chemical components in PM having emission factor of 1.7 g kg_fuel^-1 were sulfate (66%) and organics (30%) whereas the contribution of black carbon (BC) in PM was low (∼4%). Decreased engine load on the other hand increased exhaust concentrations of BC by a factor exceeding four. As a novel finding, the secondary aerosol formation potential of the emitted exhaust measured with an oxidation flow reactor and an aerosol mass spectrometer was found negligible. Thus, it seems that either DOC, scrubber, or their combination is efficient in eliminating SOA precursors. Overall, results indicate that in addition to targeting sulfur and NO_x emissions from shipping, future work should focus on mitigating harmful particle emissions.

Suitability of Different Methods for Measuring Black Carbon Emissions from Marine Engines

Black carbon (BC) emissions intensify global warming and are linked to adverse health effects. The International Maritime Organization (IMO) considers the impact of BC emissions from international shipping. A prerequisite for the anticipated limits to BC emissions from marine engines is a reliable measurement method. The three candidate methods (photoacoustic spectroscopy (PAS), laser-induced incandescence (LII), and filter smoke number (FSN)) selected by the IMO were evaluated with extensive ship exhaust matrices obtained by different fuels, engines, and emission control devices. A few instruments targeted for atmospheric measurements were included as well. The BC concentrations were close to each other with the smoke meters (AVL 415S and 415SE), PAS (AVL MSS), LII (Artium-300), MAAP 5012, aethalometers (Magee AE-33 and AE-42), and EC (TOA). In most cases, the standard deviation between instruments was in the range of 5–15% at BC concentrations below 30 mg Sm−3. Some differences in the BC concentrations measured with these instruments were potentially related to the ratio of light-absorbing compounds to sulphates or to particle sizes and morphologies. In addition, calibrations, sampling, and correction of thermophoretic loss of BC explained differences in the BC results. However, overall differences in the BC results obtained with three candidate methods selected by the IMO were low despite challenging exhaust compositions from marine diesel engines. Findings will inform decision making on BC emission control from marine engines.