Diverse changes in shipping emissions around the Western Pacific ports under the coeffect of the epidemic and fuel oil policy

Ship emissions and reduction potential under domestic policies and international cooperation: A case study in Hainan, China

Ship emissions contribute considerably to air pollution and are expected to decline under domestic policies and international cooperation such as green shipping corridors (GSCs). However, evaluation of the emission reduction potential by the Domestic Emission Control Area (DECA) policy and GSC cooperation is still lacking. Here, a series of multi-year high spatiotemporal ship emission inventories around Hainan, a representative island province of China, were developed with the state-of-the-art Shipping Emission Inventory Model. The improved origin-destination identification algorithm allowed emission allocation to port level. The emission reduction potential of the DECA policy and Hainan's joining GSC was analyzed. In 2022, ship emission intensity in waters 12 Nm from Hainan (Hainan-12Nm) were 6.4 %-7.4 % of that in waters 12 Nm from China. From 2019 to 2022, Hainan-12Nm emissions dropped by 66.7 %-77.8 % for SO2 and PM2.5. Ideally, with adequate ultra-low-sulfur fuel, DECA can reduce SO2 and PM2.5 emissions by 16.6 % and 22.4 % yearly compared with no-DECA scenario. However, emission reduction would drop markedly if ultra-low-sulfur fuel is short in supply. Emissions of voyages passing through 200 Nm from Hainan took up 1 %-4 % of international shipping emissions, implying great emission reduction potential for Hainan's establishing GSCs, especially considering the flourishing South-South trade. This study provides a thorough assessment of the current state of shipping emissions around Hainan as well as offers excellent data support for Hainan to further advance the future upgrade of ship emission management policies.

Environmental and health impacts of reduced PM2.5 and trace metals from ship emissions under low-sulfur fuel oil policy in Shanghai, China

Ship emissions can significantly exacerbate air pollution in coastal cities, threatening public health; however, a low-sulfur fuel oil policy, which restricts sulfur content in marine fuels, can effectively mitigate such pollution-driven challenges. This study employed a high-resolution ship emission inventory to assess the impacts of the fuel oil switch on air quality and public health in Shanghai from 2017 to 2021. Results showed a 37.3 % reduction in primary PM2.5 emissions from ships, with even steeper declines of 46.7 and 91.6 % in Ni and V emissions, respectively, leading to notable air quality improvements. Health assessments revealed a reduction in premature mortality attributable to long-term exposure to the contribution of ships to atmospheric PM2.5 concentrations, with deaths decreasing from 630 cases in 2017 to 481 in 2021. Similarly, short-term exposure-related deaths fell from 43 to 29. The port and waterfront areas experienced the most pronounced health benefits. The non-carcinogenic risks posed by trace metals (Ni and V), which were detected along the Huangpu River in 2017, dropped to 0.1 by 2021. Nonetheless, the carcinogenic risk from V persisted as a concern for adults in 2021. An analysis of ship-influenced episodes showed that population-weighted concentrations and short-term premature mortality decreased by over 50 % in densely populated areas and key ports. Despite the low population density in port areas such as Wusongkou and Waigaoqiao, the human health risks linked to ship emissions remained significant. This study demonstrates the effectiveness of low-sulfur fuel oil policy in reducing emissions and health risks, providing a scientific basis for refined pollution control strategies in port cities.

Synergistic effects of CO2 and air pollutants from ship emissions in Shanghai, China: Spatial-temporal characteristics, prediction assessment, policy implications

Currently, the goal of achieving net-zero emissions for ships presents a significant challenge to CO2 reduction policies. A comprehensive analysis of ship air pollutants and CO2 emissions is crucial for mitigating greenhouse effect and air pollution. To realize the overall control policies of ship emissions, this study established a high-resolution emissions inventory for air pollutants (CO, HC, NOx, PM2.5, PM10, SO2) and CO2 from 11 types of ships in Shanghai, and conducted analyses of spatiotemporal characteristics, spatial heterogeneity and consistency, and synergistic effects. Results indicated significant monthly and weekly variability in ship emissions. Due to the varying contribution rates of large ocean-going vessels, the temporal-spatial distributions of CO, HC, NOx, and CO2 revealed significant differences compared to PM2.5, PM10, and SO2. CO2 had a positive synergy in emissions with CO, HC, NOx according to the spatial heterogeneity and consistency analysis. Phasing out of old ships and implementing carbon capture technology were more conducive to CO2 reduction, while the replacement of clean energy contributed greater potential in reducing air pollutant emissions. Comprehensive mitigation measures hold effective co-benefits in air pollutants and CO2 reductions, with the synergistic effect index approaching 1. The implementation of strengthened control measures would minimize the ship emissions, achieving a 78.1% reduction in CO2, and have a positive long-term effect on co-control emission reduction. This study combines high-precision analysis, prediction assessment, and synergistic effects, providing a reference for the development of refined ship management policies in megacities worldwide.

Driving factors of ship-induced nitrogen dioxide concentrations over coastal seas of China: Implications for ship emission management

Ships generate large amounts of air pollutants, including nitrogen dioxide (NO2) that profoundly impacts air quality and poses serious threats to human health. It is crucial to understand the dynamics and drivers of ship-induced NO2 concentrations in China to support the prevention and control of fine particulate matter (PM2.5) and ozone (O3) pollution. This study built Generalized Additive Models (GAMs) to reveal the nonlinear effects of meteorological factors and ship emissions on ship-induced NO2 concentrations based on the Tropospheric Monitoring Instrument (TROPOMI) satellite data, AIS based emission model and meteorological data. A detrend analysis technique was applied to eliminate the NO2 background influenced by land-based emissions, leaving NO2 signals affected by shipping activities from 2019 to 2021 and within 200 nautical miles from the coastline of China. The detrended NO2 Vertical Column Density (VCD) exhibits a U-shaped distribution, with high values found in winter and low values in summer. The NO2 signals along major ship tracks and around primary port clusters are visible, with the measured NO2 downwind of its source in winter. The nonlinear effects of meteorological factors and ship emissions on ship-induced NO2 concentrations over three major shipping routes and two primary port clusters were explored. For every 10% increase in the monthly shipping emission, the detrended monthly NO2 VCD rises by 0.05%-1.53% in different regions, demonstrating the regional heterogeneity in the driving forces of ship-induced NO2 concentrations. The creation of site-specific and stricter emission reduction strategies is proposed for ship emission management. The results of this study can potentially offer a scientific foundation for air pollution prevention and control in the coastal areas of China.

Ship emission variations during the COVID-19 from global and continental perspectives

The COVID-19 pandemic and the International Maritime Organization's (IMO) 2020 fuel-switching policy have profoundly impacted global maritime activities, leading to unprecedented changes in shipping emissions. This study aimed to examine the effects from different scales and investigate the underlying drivers. The big data model Ship Emission Inventory Model (SEIM) was updated and applied to analyze the spatiotemporal pattern of global ship emissions as well as the main contributors in 2019 and 2020. Overall, ships emitted NOx, CO, HC, CO2, and N2O declined by 7.4 %-13.8 %, while SO2, PM2.5, and BC declined by 40.9 %-81.9 % in 2020 compared with 2019. The decline in CO2 emissions indicated a comparable reduction across vessel tonnages. Ship emissions occurring at cruising status accounted for over 90 % of the ship's CO2 emission reduction. Container ships, chemical tankers, and Ro-Ro vessels were the primary contributors to the emission reductions, with container ships alone responsible for 39.4 % of the CO2 decrease. The ship's CO2 emissions variations revealed the decline-rebound patterns in response to the pandemic. Asian-related routes saw emissions drop in February 2020, followed by a rebound in May, while European and American routes experienced declines starting in May, with a recovery in August. Further analysis of CO2 emission in Exclusive Economic Zones (EEZs) showed high temporal consistency between vessel CO2 emissions, sailing speeds, and international trade volumes across continents, and exhibited heterogeneity in main contributing ship type of emission reduction on continental scale. Our study reveals the short-term fluctuation characteristics of global ship emissions during the pandemic, particularly focusing on their spatiotemporal evolution and the inherent disparities. The results highlight the correlation between global ship emissions and trade, as well as the operational status of ships, and their rigidity.

Monetizing shipping emission reduction: Environmental benefit analysis of domestic emission control areas policy 2.0 in China

Shipping is a major contributor to anthropogenic emissions, exerting complex effects on both the environment and climate. To improve the air quality of coastal areas, China adopted an upgraded policy on domestic emission control areas (DECA 2.0) for shipping in December 2018, which expanded the geographical scope of ECAs from three designated heavy-traffic coastal regions to the entire 12 nautical mile-territorial seas and also introduced more stringent ship emission requirements. Based on data from the Automatic Identification System, this study first evaluates the environmental effects of ship emissions' reduction brought by DECA policy 2.0. Results reveal that implementation of DECA policy 2.0 has resulted in a cumulative reduction (2019-2021) of 8.43 × 105 tons, 1.3 × 105 tons, and 1.49 × 105 tons of sulfur dioxide (SO2), particulate matter <2.5 μm diameter (PM2.5) and PM <10 μm (PM10) emissions, respectively. Based on the external cost method, we further monetize the environmental benefits arising from reduction of air pollution emissions, averaging $3.6 billion USD per year. This number equates to ca. 4 % of the total output value of China's marine transportation industry over the three-year period. Finally, we calculate the fuel replacement cost arising from the implementation of DECA policy 2.0, which is on average $1.23 billion USD. This indicates that the net environmental benefits of DECA policy 2.0 equate nearly double the associated costs.

Modifications on the coastal atmospheric sulfur and cloud condensation nuclei along the Eastern China seas by shipping fuel transition

Marine fuel combustion from shipping releases SO2 and forms sulfate particles, which may alter low cloud characteristics. A series of strategies were implemented to control the sulfur content of ship fuel oil from 2018 to 2020, offering insights into the effects of the ship fuel oil transition on sulfur-related pollutants and the consequent cloud condensation nuclei (CCN) in the atmosphere. Compared to 2018 in the southeast China waters, shipping SO2 emission decreased by 78 % in 2020, resulting in a 76 % reduction in ship-related total sulfur concentration, and a decrease of 54 % in CCN number concentration under supersaturation 0.2 % (CCN0.2) contributed by shipping. The response of CCN0.2 to ship-related sulfate modification is more pronounced in relatively clean environments than polluted environments, highlighting the uneven changes in coastal CCN along the Eastern China Sea induced by the ship fuel policies. CCN can trigger the formation of cloud droplets, 2020 fuel regulation may have and will reduce the cooling radiative forcing effect with strong spatial heterogeneity. The study provides insights into the variations in coastal atmospheric sulfur-related pollutants and CCN in uneven response to changes in ship fuel oil, prompting the need for further comprehensive assessments of the climate effects resulting from potential shifts in ship fuel use in the future.

Carbon footprints: Uncovering multilevel spatiotemporal changes of ship emissions during 2019-2021 in the U.S

Quantifying and understanding changes in carbon emissions is essential for the U.S. shipping industry to reduce carbon emissions, especially after its return to the Paris Agreement. We estimated carbon emissions from 48,321 ships in the U.S. Exclusive Economic Zone (EEZ) using the power-based method based on 3.6 billion Automatic Identification System (AIS) reports. We explored the characterization of carbon emissions from the national, regional, and port levels during 2019-2021 by allocating emissions on a 1 km*1 km grid through an activity-weighted method. The results show: (1) Due to the COVID-19 pandemic, emissions within the EEZ show a temporal trend of decreased and then rebound, specifically from 32.628 Tg in 2019 to 30.741 Tg in 2020 and then bounced to 31.786 Tg in 2021. The spatial differences in emissions show significant heterogeneity; (2) There are significant differences in emissions by vessel type, flag, and operational mode for the four regions of the U.S. (Great Lakes, Gulf Coast, Pacific Coast, and Atlantic Coast). Thus, emissions in these regions show different variability patterns over three years. Notably, "port congestion" led to record high emissions on the Pacific Coast; (3) Containerized cargo contributes the most to port core area emissions, so most ports with higher throughputs have higher emissions, with Long Beach and Los Angeles having the highest. Emissions from coastal ports are high and volatile, while inland ports are low and stable. This study provides the U.S. with a high spatiotemporal resolution inventory of carbon emissions from ships, and the findings are expected to provide some reference for controlling ship emissions.

Impacts of Ship Emissions on Air Quality in Southern China: Opportunistic Insights from the Abrupt Emission Changes in Early 2020

In early 2020, two unique events perturbed ship emissions of pollutants around Southern China, proffering insights into the impacts of ship emissions on regional air quality: the decline of ship activities due to COVID-19 and the global enforcement of low-sulfur (<0.5%) fuel oil for ships. In January and February 2020, estimated ship emissions of NOx, SO2, and primary PM2.5 over Southern China dropped by 19, 71, and 58%, respectively, relative to the same period in 2019. The decline of ship NOx emissions was mostly over the coastal waters and inland waterways of Southern China due to reduced ship activities. The decline of ship SO2 and primary PM2.5 emissions was most pronounced outside the Chinese Domestic Emission Control Area due to the switch to low-sulfur fuel oil there. Ship emission reductions in early 2020 drove 16 to 18% decreases in surface NO2 levels but 3.8 to 4.9% increases in surface ozone over Southern China. We estimated that ship emissions contributed 40% of surface NO2 concentrations over Guangdong in winter. Our results indicated that future abatements of ship emissions should be implemented synergistically with reductions of land-borne anthropogenic emissions of nonmethane volatile organic compounds to effectively alleviate regional ozone pollution.