Hyperspectral satellite reveals an unexpected increase of global SO2 over oceans over the last two decades

Hyperspectral satellite reveals an unexpected increase of global SO2 over oceans over the last two decades | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Hyperspectral satellite reveals an unexpected increase of global SO 2 over oceans over the last two decades Qihou Hu, Ziwei Li, Xiaohan Wang, Jin Ye, Yizhi Zhu, Ran Zhao, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3996146/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Sulfur dioxide(SO 2 ) is a major air pollutant over oceans, which exacerbates ecological and environmental issues like acid rain, ocean acidification, and air pollution. Over the past few decades, the robust growth of the shipping industry has led to a continuous increase in SO 2 emissions by ocean-going vessels. However, the trend of global SO 2 concentrations over the oceans is unclear due to rare in-situ observations at marine sites. Hyperspectral satellite remote sensing is an ideal method to obtain the spatiotemporal distribution of SO 2 , whereas accurately retrieving SO 2 concentrations in the marine atmosphere has traditionally been challenging due to issues like high noise levels and limitations in detecting lower concentrations close to the detection limits. In this study, we retrieved global SO 2 concentrations, particularly over oceans, from the space-borne Ozone Monitoring Instrument (OMI) through a series of remote sensing algorithm optimizations from spectral calibration to retrieve. Our research revealed that the average global SO 2 concentrations over lands almost unchanged although the concentrations in China and the United States decreased by 51% and 24%, respectively. Nevertheless, global SO 2 concentrations over oceans increased at an annual rate of 6.1%, with an increase over the inshore regions of India of 200% from 2005 to 2018, despite a notable decrease over inshore China at an annual rate of 4.2%. Our study revealed that the increase in shipments will not necessarily lead to an increase in SO 2 . Under green competitiveness, SO 2 per TEU over inshore China continuously decreased, which induced a great decrease in SO 2 with a 214% increase in throughput. Earth and environmental sciences/Environmental sciences/Environmental impact Earth and environmental sciences/Environmental social sciences/Environmental impact Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction SO 2 , a colorless and odorless trace gas with corrosive properties, is responsible for the onset of issues such as acid rain, the greenhouse effect, photochemical pollution, and eutrophication. In addition to its effects on global radiative forcing and atmospheric deposition, SO 2 is essential for maintaining environmental health worldwide 1 . Several research investigations examined the significant variations in worldwide SO 2 emissions during the past few decades in terrestrial regions, with differences in the changes noted across different regions 2, 3, 4 . The 20th century saw a significant rise in SO 2 emissions 5, 6 . At the end of the 20th century, heightened awareness of the detrimental impacts of air pollution on both the environment and human health prompted endeavors to enact legislation aimed at reducing emissions and controlling SO 2 pollution 7, 8 . Earlier research has shown that developed countries, particularly in Europe and North America, have successfully implemented air quality policies over recent decades to mitigate mainland SO 2 pollution, leading to significant reductions in SO 2 concentrations 9, 10, 11 . Through technological improvements and more stringent emission regulations, in 2000, Europe reduced its SO 2 emissions by 54% compared to 1990 by installing flue gas desulfurization systems 12 . In 1990, the United States implemented regulations such as the "Clean Air Act" 8 , which resulted in a 21% reduction in SO 2 emissions from 1990 to 2000. Besides, SO 2 emissions in China reached the peak in 2007 , with the onset of emission controls in power plants 13 . Therefore, the hyperspectral satellite instrument, Ozone Monitoring Instrument (OMI) captured a sharp decline in SO 2 in the Yangtze River Delta and Pearl River Delta regions of China in the past decade 14, 15 . However, from satellite observations, SO 2 concentrations in India increased by 200% from 2005 to 2015, owing to a lack of regulations to control SO 2 emissions from coal-fired power plants 3 . Moreover, after 2015, SO 2 emissions in India even surged dramatically, surpassing China and making it the world's largest SO 2 polluter 16 . In general, the trend of atmospheric SO 2 on continents is still ambiguous on a global scale. In addition, SO 2 emissions over the oceans have probably increased since the beginning of the 21st century, with the rapid increase in the global shipping industry under the backdrop of economic globalization. Europe, North America, and East Asia are the three most concentrated areas of ports in the world 17 . For several decades, large diesel engines burning heavy fuel oil (HFO) have dominated the energy systems of maritime shipping. These engines generate SO 2 , leading to a degradation of air quality in coastal areas 18 . With the growth of the shipping industry, air pollution from shipping has become an increasingly serious concern for both environmental quality and human health, especially in coastal regions 19, 20 . Additionally, the ocean acidification caused by SO 2 may be as detrimental as CO 2 , severely impacting the marine ecosystem 21, 22, 23, 24 . As a result, both domestic and international entities have formulated various measures aimed at reducing ship emissions 25, 26 . Under the International Maritime Organization (IMO) treaty known as the "International Convention For The Prevention Of Pollution" which came into effect in 2005, Europe, North America, and China responded by establishing emission control areas (ECAs). In these areas, the sulfur content of fuels used by vessels operating within them is regulated 27, 28, 29 . The majority of model-based studies have demonstrated the effectiveness of policy implementation in reducing SO 2 emissions from ships 30, 31, 32, 33, 34 . While these studies suggest that emission reduction regulations can yield substantial health and environmental benefits, they often focus on specific routes, ports, or regional sea areas of a country. Some studies contrarily indicated that despite the restrictions imposed by emission reduction regulations, SO 2 concentrations in specific ports continue to increase 33, 35 . In fact, the significant cost disparity between high-sulfur fuels (such as heavy fuel oil) and low-sulfur fuels (like marine gas oil and low-sulfur fuel oil) makes the transition from high-sulfur to low-sulfur fuels quite challenging 36, 37 . Due to a severe lack of marine SO 2 observations, there is little research on the actual observation of SO 2 , especially in different emission control areas and even on a global scale. In this study, we obtained the concentrations of global atmospheric SO 2 during 2005-2018 from OMI observation using our updated retrival algorithm, which includes on-orbit calibration, simulated irradiance, fitting window selection, ‘‘soft calibration” and measurement error correction. The trends of atmospheric SO 2 over both continents and oceans were traced based on satellite observations. Besides, the influence of transport from oceans on SO 2 over marine cities and the effects of green competitiveness on the emission reduction of SO 2 over oceans were evaluated. This study will contribute to a better understanding of global SO 2 pollution trends and its drivers, especially over oceans. Spatial and temporal patterns of global atmospheric SO2 As shown in Fig. 1 , high global SO 2 concentrations on land are primarily distributed in Eastern China, Northern India, and the Eastern United States. China, especially in the North China Plain, had the highest SO 2 concentrations in the world from 2005 to 2016, which reached a peak of 2.03 DU on average in 2007. During the "11th Five-Year Plan" period (2006–2010), China undertook a series of measures to improve energy efficiency and reduce emissions, including shutting down small thermal power units and installing flue gas desulfurization systems 38 , SO 2 in China has significantly decreased, gradually approaching the global average concentrations after 2017. Although there was a slight rebound after the 2011 financial crisis due to economic stimulus policies, emissions have steadily declined since 2012 3 . According to statistics, in 2015, the SO 2 emissions from coal-fired power generation in China witnessed a substantial reduction of 64.65% compared to the year of 2006 39 . Correspondingly, the average SO 2 concentrations decreased by 22.33% from 2006 to 2015. SO 2 hotspots in the United States are primarily located in the Eastern region, originating from coal-fired power plants and industrial activities 3 . From 2005 to 2011, the SO 2 concentrations in the United States decreased by 42.9%, possibly attributable to the " Clean Air Act Amendments of 1990" 40 . In Europe, the SO 2 concentrations have kept at low levels with little variations in the past 14 years. Our research revealed that the average global SO 2 concentrations over land from 2005 to 2018 were almost unchanged, although the concentrations in China and the United States decreased by 51% and 24%, respectively. The rapid growth of SO 2 in India, Pakistan, and South America counteracted the effect of emission reduction by China and the United States. Particularly, over the past 14 years, SO 2 concentrations in India have increased by 57%. Since 2015, there has been a sharp increase in SO 2 concentrations in India, leading to India surpassing China as the world's largest anthropogenic SO2 emitter 16 . Some studies attributed India's SO 2 emissions to the rapid expansion of coal-fired power plants 41 and the predominance of organic sulfur compounds in local coal 42 , which made transitioning to cleaner fuels challenging. As shown in Fig. 2 , from 2005 to 2018, although the SO 2 concentrations in China and the United States decreased by 55% and 24%, respectively, the global marine SO 2 concentrations increased by 79.2% at a rate of 6.1% per year. Over nearshore areas, the reduction in SO 2 concentrations in China and the United States can be attributed to restrictions on sulfur content in fuels within emission control areas. However, despite the establishment of the North Sea emission control area in Europe, marine SO 2 concentrations in European waters increased by 5% from 2005 to 2018, indicating limited control effectiveness. This could be because the European shipping industry is shifting from maritime to road transportation in response to tighter sulfur content limits. This shift may have adverse effects on the environmental performance of shipping, and further examination of the impact of ECA regulations is warranted 32 . During this period, SO 2 concentrations over the Indian offshore area increased by 200%, with an annual growth rate of 8.5%, which was the largest contributor to the rapid increase in global marine SO 2 concentrations. The surge in maritime SO 2 concentrations in India could be attributed to the absence of emission control zones, resulting in a lack of effective oversight and regulation in coastal maritime areas. Besides, we observed significant SO 2 concentrations over the Persian Gulf, which may be associated with emissions from the region's oil and gas industry, gas flaring, and shipping 3 . From 2005 to 2010, global marine SO 2 concentrations increased by 116.8%. During this period, the United States and China saw decreases of 19.8% and 22.7% in maritime SO 2 concentrations, while Europe experienced a 4% reduction. In contrast, India witnessed a significant 200% rise in maritime SO 2 concentrations. In the subsequent period from 2010 to 2018, global marine SO 2 concentrations showed a relatively stable fluctuation due to the tightening of emission control policies. The United States and China experienced reductions of 20.8% and 41.8% in SO 2 concentrations, respectively, while the airspace near Europe saw a 9.5% increase. India's maritime SO 2 concentrations remained almost unchanged during this period. Despite tightening ship fuel controls after 2010, maritime SO 2 concentrations in Europe have increased. Overall, the ECAs advocated by the IMO have substantiated their efficacy in curtailing and managing SO 2 emissions by ocean-going vessels in the United States and China. Particularly, the tightening of emission control policies in the U.S. and the establishment of emission control areas in China after 2016 accelerated maritime SO 2 control in both countries. However, it cannot be ruled out that within specific ports, SO 2 emissions generated by ocean-going vessels may contribute more to urban pollution than land-based emission sources 24 , 43 , 44 . SO2 pollution over global major Ports SO 2 pollution over Chinese Ports . According to the 2016 World Port Rankings of the American Association of Port Authorities 45 , there are 19 ports located in Europe, North America, and Asia in the top 20 ports, with a proportion of 75% for Asira and 45% for China. In 2018, China's port throughput surged by 247% compared to 2005. Notably, Shanghai and Guangzhou ports secured top positions in the global throughput rankings. In response to the call of the IMO and to address pollution in Chinese waters, China established ECAs in 2016, requiring vessels at major ports within these control areas to use fuels with a sulfur content not exceeding 0.5% (m/m) since 2007 28 . Shanghai and Guangzhou ports are both international ports located within established emission control areas in China. As shown in Fig. 3 , the Shanghai and Guangdong ports show a continuous decrease in SO 2 concentrations on both land and marine. China's desulfurization policies led to a substantial decrease in land-based SO 2 concentrations at Shanghai Port from 2007 onwards. A minor uptick in SO 2 concentrations occurred in 2011 due to economic stimulus policies after the financial crisis. Since 2012, Shanghai Port's land-based SO 2 concentrations has rapidly decreased. By 2017, land and marine SO 2 concentrations had become comparable. In 2017, Shanghai's maritime SO 2 concentrations decreased by 12.4% compared to 2016 due to emission reduction policies. Additionally, Guangzhou Port's SO 2 concentrations mirror Shanghai Port's trends. Compared to Shanghai, Guangzhou's onshore SO2 concentrations began decreasing after 2006 without a notable rise after the financial crisis. Notably, Guangzhou Port exhibits environmental advantages over Shanghai. After 2014, Guangzhou's onshore SO 2 concentrations swiftly declined. By 2016, onshore and offshore SO 2 concentrations had aligned. Compared to 2016, fueled by emission reduction policies, Guangzhou witnessed a significant 31.7% drop in marine SO 2 concentrations in 2017. From 2005 to 2018, maritime SO 2 concentrations in Shanghai and Guangzhou ports decreased by 78.1% and 79.8%, respectively, signifying a notable improvement in China's maritime SO 2 concentrations. Although land-based SO 2 concentrations in these ports remain higher than maritime concentrations, the two have gradually approached parity over time. To explore the influence of SO 2 over oceans on air quality in port cities, a potential source contribution function (PSCF) analysis was conducted based on the in-situ observations of ground-level SO 2 . Figure 4 indicates that high SO 2 concentrations in Guangzhou Port may result from land-based sources, while Shanghai Port faces elevated SO 2 concentrations from the maritime direction. This highlights the need for stricter regulatory policies, particularly for Shanghai Port. SO 2 pollution over Indian Ports. According to the 2016 World Port Ranking by the American Association of Port Authorities 45 , the Port of Mumbai in India was the only one among the top 30 ports, ranking 30th. We chose the ports of Chennai and Mumbai, located on the southeast and west coasts of India, respectively. As shown in Fig. 3 , there is an increasing trend in both terrestrial and marine SO 2 concentrations in the ports of Mumbai and Chennai. For example, between 2005 and 2018, marine SO 2 concentrations increased by 110.9% in Mumbai and by 183.6% in Chennai. Due to the lack of emission regulations, SO 2 emissions from oceangoing vessels are unrestricted. Compared to Mumbai, Chennai's SO 2 concentrations increased even more rapidly, likely due to lower port transportation efficiency 46 . During the economic crisis from 2007 to 2008, SO 2 concentrations increased, possibly influenced by unregulated human activities in maritime areas during the economic downturn. The maritime SO 2 concentrations in Mumbai exceeded those on land in 2013 and 2018. Unfortunately, due to the delayed establishment of SO 2 observation stations in India, ground-level data for this period is unavailable. Therefore, we can only select 2020 for the PSCF analysis of Indian ports to assess the contribution of marine and terrestrial SO 2 sources. As shown in Fig. 4 , the high concentrations of SO 2 in the ports of Mumbai and Chennai are largely attributed to maritime pollution. The primary source of SO 2 emissions in Indian ports is associated with maritime activities 47 . Hence, the Indian government must urgently establish effective control measures to improve the environmental conditions in port cities, balancing environmental concerns with economic development. SO 2 pollution over European and American ports. Over the decades, ports in North America and Europe had exhibited a complex pattern of growth, stagnation, decline, or moderate growth 48 . In this study, we selected the ports of New York and Savannah in the United States, Rotterdam in the Nederlands and Valencia in Spain for further research. New York and Savannah are both located on the East Coast of the United States and must adhere to regulations regarding fuel sulfur content in the North American Emission Control Area. Since August 1, 2010, vessels operating within this region have been required to use fuel with a sulfur content not exceeding 1.00% (m/m). This limit was further reduced to 0.10% (m/m) on January 1, 2015. Figure 3 demonstrates that in the United States, SO 2 concentrations on land are consistently higher than those over the ocean. The SO 2 concentrations decreased on land in New York Port, while remaining stable in Savannah Port. Both ports experienced an increase in marine SO 2 concentrations in 2008, with New York rising by 9.3% and Savannah by 62% compared to 2007, possibly due to relaxed environmental controls during the financial crisis. Following the implementation of sulfur reduction policies in 2010 and further tightening in 2015, port areas, especially New York Harbor, witnessed notable declines in marine SO 2 concentrations. Specifically, there was a reduction of 20.1% in 2010 and 10.5% in 2015. However, after 2010, New York's marine SO 2 concentrations gradually increased, showing a trend of convergence between marine and land-based pollution, particularly in 2017. Nevertheless, the primary source of SO 2 concentrations in U.S. port cities comes from land. In our PSCF analysis, no instances were identified where high concentrations of SO 2 in ports originated from the ocean. Rotterdam, which is situated in the Netherlands, is under the control of the North Sea ECAs, which have been effective since November 22, 2007, in accordance with Annex VI of the International Convention for the Prevention of Pollution from Ships. This regulation mandates a sulfur content of 1.00% (m/m) for fuels 49 . Valencia is a Spanish port located in the Mediterranean, it is not within the jurisdiction of the North Sea ECA. Rotterdam and Valencia ports exhibit similar trends in SO 2 concentrations. During the financial crisis, both ports experienced increases in both land and marine SO 2 concentrations. Despite the initial effectiveness of the 2010 policy implementation, the control proved to be short-lived. Since 2011, pollution has continued to increase significantly, with Rotterdam and Valencia experiencing a 70.5% and 46.1% rise, respectively, in nearshore SO 2 concentrations in 2014 compared to pre-sulfur limit levels in 2009. This could be attributed to the impact of the Russian oil crisis 50 . However, in reality, after 2015, SO 2 concentrations in both ports decreased rapidly. By 2018, Rotterdam and Valencia ports witnessed a reduction of 60.1% and 46.8%, respectively, compared to 2014. The influence of port green competitiveness on SO2 over port cities With the rapid development of the shipping industry against the background of economic globalization, SO 2 concentrations over oceans would continue to increase if no measures were taken to reduce emissions 51 . Fortunately, port green competitiveness, which includes optimizing port infrastructure and functions, as well as developing energy-saving and emission reduction technologies, could reduce the emission per TEU and further mitigate air pollution over the offshore areas of the port cities 52 . Here we compare the green competitiveness of ports among the global major ports by examining the SO 2 concentrations per TEU. A smaller numerical value indicates that the port has greater green competitiveness, effectively balancing shipping trade and environmental benefits. As shown in Fig. 5 , the ranking of green competitiveness from highest to lowest is Guangzhou Port, Shanghai Port, Savannah Port, Rotterdam Port, New York Port, Valencia Port, Mumbai Port, and Chennai Port. The SO 2 concentrations per TEU in Shanghai dropped significantly by 90.6% from 2005 to 2018. Similarly, Guangzhou initially maintained stability but witnessed a noteworthy 73.3% reduction from 2016 to 2018 following the implementation of emission control areas. From 2005 to 2018, SO 2 concentrations per TEU declined by 32.8% and 45.8% in Savannah and New York ports, respectively. Rotterdam and Valencia in Europe experienced a slight increase in SO 2 concentrations, but the concentrations per unit throughput decreased significantly by 60.2% and 73.5%, respectively. Conversely, Mumbai and Chennai witnessed an increase of 9.8% and 29.7% in SO 2 concentrations per TEU, respectively. Compared to Guangzhou, Shanghai Port handles more containers and has higher transportation efficiency, but exhibits lower green competitiveness 53 . Shanghai Port generates more SO 2 concentrations per TEU than Guangzhou. However, through continuous emission control efforts, Shanghai Port's SO 2 concentrations per TEU decreased to a level comparable to that of Guangzhou. Despite the increase in throughput at Indian ports in recent years, container terminals in India still have untapped throughput potential 54 .The green competitiveness of both Indian ports is lower than that of China, with Chennai port having the lowest green competitiveness and a decreasing trend. The SO 2 concentrations per TEU steadily increases. Furthermore, the New York and Savannah ports exhibit greater green competitiveness than the European ports in Rotterdam and Valencia, with slightly lower SO 2 concentrations per TEU. Compared to Rotterdam, although the SO 2 concentrations levels in Valencia are not high, its green competitiveness is lower. Methods Observational data. We apply an optimal estimation algorithm originally developed at the Smithsonian Astrophysical Observatory (SAO) for retrieving ozone profiles and tropospheric ozone from the GOME and OMI instruments 55 to retrieve SO 2 . The algorithm used for retrieval and detailed information on ground validation can be found in our previous work 56 . OMI was launched in July 2004 on board the Aura satellite, of the National Aeronautics and Space Administration (NASA), which is in a sun-synchronous ascending polar orbit at 705 km altitude with a 13:45 local equator-crossing time. OMI covers a spectral range from ultraviolet to visible, enabling daily global coverage 57 .We regridded OMI SO 2 data into a latitude-longitude grid of 0.1° × 0.1°. To ensure the reliability of the analysis results, we excluded satellite SO 2 observations with poor quality flags, such as those associated with cloudy scenes (cloud radiance fraction > 0.3) and high-latitude regions (latitude > 60). The research presented here spans from 2005 to 2018. To enhance the accuracy of the SO 2 data, a multistep process, including error screening and stripe removal, was conducted. To mitigate the impact of volcanic eruptions on the statistical outcomes, data corresponding to periods of significant volcanic activity were excluded 58 . Analysis of wind screening. To mitigate the influence of land-sea interactions on marine SO 2 concentrations, wind data within half an hour of OMI satellite passes were collated from the ERA5 wind speed dataset. Specifically, for the assessment of marine SO 2 concentrations, the influence of strong winds blowing from the land toward the ocean was excluded. Simultaneously, when evaluating land-based SO 2 concentrations, the data excluded the impact of strong winds blowing from the sea toward the land. Declarations Data availability The wind data utilized in this study is sourced from the fifth generation of the European Centre for Medium-Range Weather Forecasts atmospheric reanalysis (ERA5) datasets 59 (available from https://climate.copernicus.eu/climate-reanalysis, last accessed on July 25, 2023). The wind variables were acquired at a moderate resolution of 0.25°, encompassing u-components and v-components of the 10 m wind (u and v). The throughput data used in this study is sourced from the CEIC database (available at https://www.ceicdata.com.cn/zh-hans, last accessed on July 25, 2023). The Potential Source Contribution Function (PSCF) analysis employed the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model from the NOAA Air Resources Laboratory, available at http://www.ready.noaa.gov. The throughput data selected for this study is a global dataset covering major ports from 2005 to 2018. To evaluate a port's green competitiveness, divide the port's SO 2 concentrations by its throughput. The global SO 2 concentrations data used in this study are stored at the Supercomputing Center of the University of Science and Technology of China due to its large data storage and can be made available from the corresponding author upon request. Acknowledgements This research was supported by the National Natural Science Foundation of China (42225504), the National Key Research and Development Program of China (2022YFC3700100), the Key Research Program of Frontier Sciences, CAS (No. ZDBS-LY-DQC008), the Youth Innovation Promotion Association of CAS (2021443), the Major Project of High Resolution Earth Observation System (30-Y60B01-9003-22/23), the New Cornerstone Science Foundation through the XPLORER PRIZE (2023-1033), the HFIPS Director’s Fund (BJPY2022B07 and YZJJQY202303), and the Hefei Comprehensive National Science Center. Contributions Qihou Hu and Cheng Liu contributed to the design of the study, whereas Ziwei Li authored this paper. Xiaohan Wang, Jin Ye, Yizhi Zhu, and Ran Zhao participated in the data analysis. Competing interests The authors declare no competing interests. References Zipper CE, Gilroy L. Sulfur Dioxide Emissions and Market Effects under the Clean Air Act Acid Rain Program. 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Barriers to adopting least-cost particulate control strategies for Indian power plants. Energy Policy 1998, 26(14): 1053–1063. Fan Q, Zhang Y, Ma W, Ma H, Feng J, Yu Q, et al. Spatial and Seasonal Dynamics of Ship Emissions over the Yangtze River Delta and East China Sea and Their Potential Environmental Influence. Environ Sci Technol 2016, 50(3): 1322–1329. Dalsoren SE, MS; Endresen, O; Mjelde, A; Gravir, G; Isaksen, ISA. Update on emissions and environmental impacts from the international fleet of ships: the contribution from major ship types and ports. Atmospheric Chem Phys 2009, 9(6): 2171–2194. World Port Rankings.(Authorities AAoP, accessed 11 January 2024); https://www.aapa-ports.org/unifying/content.aspx?ItemNumber=21048 Nanyam VPSN, Kumar Jha N. Modeling challenges affecting the performance of major ports of India. The Asian Journal of Shipping and Logistics 2023, 39(3): 26–38. Joseph J, Patil RS, Gupta SK. Estimation of air pollutant emission loads from construction and operational activities of a port and harbour in Mumbai, India. Environ Monit Assess 2009, 159(1–4): 85–98. Merk O. The Competitiveness of Global Port-Cities: Synthesis Report. 2013. Wang S, Peng C. Model and analysis of the effect of China’s potential domestic emission control area with 0.1% sulphur limit. Maritime Business Review 2019, 4(3): 298–309. Vestreng V. Twenty-five years of continuous sulphur dioxide emission reduction in Europe. Atmospheric Chemistry and Physics 2007. Li Y, Jia P, Jiang S, Li H, Kuang H, Hong Y, et al. The climate impact of high seas shipping. Natl Sci Rev 2023, 10(3): nwac279. Kuang H, Zhu J, Bai Z. Study on the Interaction between Green Competitiveness of Coastal Ports and Hinterland Economy. Sustainability 2023, 15(2). R JJaZWaQ. Green Competitiveness Evaluation of Ports Based on Entropy Method. The Sixteenth International Conference on Management Science and Engineering Management; 2022; 2022. p. 353–364. Nanyam VPSN, Jha KN. Conceptual Model for the Operational Performance of the Container Terminals in India. Journal of Waterway, Port, Coastal, and Ocean Engineering 2022, 148(4). Liu X, Chance K, Sioris CE, Spurr RJD, Kurosu TP, Martin RV, et al. Ozone profile and tropospheric ozone retrievals from the Global Ozone Monitoring Experiment: Algorithm description and validation. Journal of Geophysical Research: Atmospheres 2005, 110(D20). Xia C, Liu C, Cai Z, Zhao F, Su W, Zhang C, et al. First sulfur dioxide observations from the environmental trace gases monitoring instrument (EMI) onboard the GeoFen-5 satellite. Sci Bull (Beijing) 2021, 66(10): 969–973. Lu Z, Streets DG, de Foy B, Krotkov NA. Ozone monitoring instrument observations of interannual increases in SO2 emissions from Indian coal-fired power plants during 2005–2012. Environ Sci Technol 2013, 47(24): 13993-14000. Tournigand P-Y, Cigala V, Lasota E, Hammouti M, Clarisse L, Brenot H, et al. A multi-sensor satellite-based archive of the largest SO2volcanic eruptions since 2006. Earth System Science Data 2020, 12(4): 3139–3159. Hersbach H, Bell B, Berrisford P, Hirahara S, Horányi A, Muñoz-Sabater J, et al. The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society 2020, 146(730): 1999–2049. Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3996146","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":276398078,"identity":"91a2e018-55eb-45f5-af88-154d3561b53e","order_by":0,"name":"Qihou Hu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAt0lEQVRIiWNgGAWjYDACCR4Ghg8MEgzsDaRoYZwB1MJzgBQtzECLSNDCd7v3mLRNjYUcj9gBxg8/GOzyCGqRvHMuTTrnmIQxj3QCs2QPQ3IxQS0GN3LMpHPYJBL3SycwSDMwHEhsIEqLxT+JxB6gLb+J18LYBtbCRpwtkjdyjC17+0B+SWyz7DFIJqyF70aO4Y0f3+rkeKSTD9/4UWFHWAvDATiLEajYgKB6FC2jYBSMglEwCnAAABWxNYTPxSF1AAAAAElFTkSuQmCC","orcid":"","institution":"Hefei Institutes of Physical Science, Chinese Academy of Sciences","correspondingAuthor":true,"prefix":"","firstName":"Qihou","middleName":"","lastName":"Hu","suffix":""},{"id":276398079,"identity":"81e993ff-b1e9-4e2a-b038-e66d2cdeeea3","order_by":1,"name":"Ziwei Li","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Ziwei","middleName":"","lastName":"Li","suffix":""},{"id":276398080,"identity":"18f0b18a-d7a9-421b-9762-9ed1607975dc","order_by":2,"name":"Xiaohan Wang","email":"","orcid":"","institution":"Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Xiaohan","middleName":"","lastName":"Wang","suffix":""},{"id":276398081,"identity":"9fc72b97-002c-4f65-b9fb-b6cce679b992","order_by":3,"name":"Jin Ye","email":"","orcid":"","institution":"School of Environmental Science and Optoelectronic Technology, University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Jin","middleName":"","lastName":"Ye","suffix":""},{"id":276398082,"identity":"6589caed-1abe-495f-94ca-8f5a73f506cc","order_by":4,"name":"Yizhi Zhu","email":"","orcid":"","institution":"School of Environmental Science and Engineering, Suzhou University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yizhi","middleName":"","lastName":"Zhu","suffix":""},{"id":276398083,"identity":"9b7e83c1-04ca-4de7-8f77-f9819e71057a","order_by":5,"name":"Ran Zhao","email":"","orcid":"","institution":"School of Environmental Science and Optoelectronic Technology, University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Ran","middleName":"","lastName":"Zhao","suffix":""},{"id":276398084,"identity":"7bdd91f1-42bc-440a-a8a7-657cf3807b76","order_by":6,"name":"Cheng Liu","email":"","orcid":"","institution":"University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Cheng","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2024-02-28 08:45:59","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3996146/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3996146/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":52079823,"identity":"5cbc666b-35d8-4e83-8694-02dfaf87d126","added_by":"auto","created_at":"2024-03-06 11:07:50","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":732188,"visible":true,"origin":"","legend":"\u003cp\u003eGlobal distribution and time series of SO\u003csub\u003e2\u003c/sub\u003e land-based pollution. Parts (a) and (c) show the land-based SO\u003csub\u003e2\u003c/sub\u003e distributions in 2005 and 2018. Parts (b) and (d) show the trends in land-based SO\u003csub\u003e2\u003c/sub\u003e concentrations from 2005 to 2018.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-3996146/v1/146e8678d81720fcf8808ece.png"},{"id":52079824,"identity":"38baa03a-18f4-4dd2-a25a-9ce28268afbf","added_by":"auto","created_at":"2024-03-06 11:07:50","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1251409,"visible":true,"origin":"","legend":"\u003cp\u003eGlobal distribution and time series of SO\u003csub\u003e2\u003c/sub\u003e marine pollution. Parts (a) and (c) show the marine SO\u003csub\u003e2\u003c/sub\u003e distributions in 2005 and 2018. Parts (b) and (d) show the trends in marine SO\u003csub\u003e2\u003c/sub\u003e concentrations from 2005 to 2018.\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-3996146/v1/c7a07d81e3bd359f7f94788c.png"},{"id":52080322,"identity":"634f8aff-73b8-4fbb-838f-c5eead4b90bd","added_by":"auto","created_at":"2024-03-06 11:15:50","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":208240,"visible":true,"origin":"","legend":"\u003cp\u003eThe changes in land and marine SO\u003csub\u003e2\u003c/sub\u003e concentrations in port cities of (a) Shanghai, (b) Savannah, (c) Guangzhou, (d) New York, (e) Mumbai, (f) Valencia, (g) Chennai, and (h) Rotterdam.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-3996146/v1/feb449280be32be6a647f69b.png"},{"id":52080323,"identity":"b849aa96-3ef9-4712-9234-501372e030d0","added_by":"auto","created_at":"2024-03-06 11:15:51","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":271591,"visible":true,"origin":"","legend":"\u003cp\u003eBased on the HYSPLIT model, a backward trajectory analysis of the air mass was conducted, and a potential source contribution function (PSCF) analysis of the air mass trajectory was performed\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3996146/v1/6e75cf2eb65e03449902d7b0.jpg"},{"id":52079827,"identity":"2aa037c6-9f82-49e0-9e67-7e49fc6e9c94","added_by":"auto","created_at":"2024-03-06 11:07:50","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":417496,"visible":true,"origin":"","legend":"\u003cp\u003eSO\u003csub\u003e2\u003c/sub\u003e pollution per TEU (Twenty-foot Equivalent Unit), Parts (a-h) depict the trends in land and marine SO\u003csub\u003e2\u003c/sub\u003e concentrations per TEU for Shanghai, Savannah, Guangzhou, New York, Mumbai, Valencia, Chennai, and Rotterdam.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-3996146/v1/5d3957991c25c8c25a34c98b.png"},{"id":53568956,"identity":"7449731e-7c62-444e-84ea-9a1f52688251","added_by":"auto","created_at":"2024-03-27 14:55:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2267058,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3996146/v1/e01c3349-73ec-4406-a372-93ea2cdf971c.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"\u003cp\u003eHyperspectral satellite reveals an unexpected increase of global SO\u003csub\u003e2\u003c/sub\u003e over oceans over the last two decades\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSO\u003csub\u003e2\u003c/sub\u003e, a colorless and odorless trace gas with corrosive properties, is responsible for the onset of issues such as acid rain, the greenhouse effect, photochemical pollution, and eutrophication. In addition to its effects on global radiative forcing and atmospheric deposition, SO\u003csub\u003e2\u003c/sub\u003e is essential for maintaining environmental health worldwide\u003csup\u003e1\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eSeveral research investigations examined the significant variations in worldwide SO\u003csub\u003e2\u003c/sub\u003e emissions during the past few decades in terrestrial regions, with differences in the changes noted across different regions\u003csup\u003e2, 3, 4\u003c/sup\u003e. The 20th century saw a significant rise in SO\u003csub\u003e2\u003c/sub\u003e emissions\u003csup\u003e5, 6\u003c/sup\u003e. At the end of the 20th century, heightened awareness of the detrimental impacts of air pollution on both the environment and human health prompted endeavors to enact legislation aimed at reducing emissions and controlling SO\u003csub\u003e2\u003c/sub\u003e pollution\u003csup\u003e7, 8\u003c/sup\u003e. Earlier research has shown that developed countries, particularly in Europe and North America, have successfully implemented air quality policies over recent decades to mitigate mainland SO\u003csub\u003e2\u003c/sub\u003e pollution, leading to significant reductions in SO\u003csub\u003e2\u003c/sub\u003e concentrations\u003csup\u003e9, 10, 11\u003c/sup\u003e. Through technological improvements and more stringent emission regulations, in 2000, Europe reduced its SO\u003csub\u003e2\u003c/sub\u003e emissions by 54% compared to 1990 by installing flue gas desulfurization systems\u003csup\u003e12\u003c/sup\u003e. In 1990, the United States implemented regulations such as the \u0026quot;Clean Air Act\u0026quot;\u003csup\u003e8\u003c/sup\u003e, which resulted in a 21% reduction in SO\u003csub\u003e2\u003c/sub\u003e emissions from 1990 to 2000. Besides, SO\u003csub\u003e2\u003c/sub\u003e emissions in China reached the peak in 2007 , with the onset of emission controls in power plants\u003csup\u003e13\u003c/sup\u003e. Therefore, the hyperspectral satellite instrument, Ozone Monitoring Instrument (OMI) captured a sharp decline in SO\u003csub\u003e2\u003c/sub\u003e in the Yangtze River Delta and Pearl River Delta regions of China in the past decade\u003csup\u003e14, 15\u003c/sup\u003e. However, from satellite observations, SO\u003csub\u003e2\u003c/sub\u003e concentrations in India increased by 200% from 2005 to 2015, owing to a lack of regulations to control SO\u003csub\u003e2 \u003c/sub\u003eemissions from coal-fired power plants\u003csup\u003e3\u003c/sup\u003e. Moreover, after 2015, SO\u003csub\u003e2\u003c/sub\u003e emissions in India even surged dramatically, surpassing China and making it the world\u0026apos;s largest SO\u003csub\u003e2\u003c/sub\u003e polluter\u003csup\u003e16\u003c/sup\u003e . In general, the trend of atmospheric SO\u003csub\u003e2\u003c/sub\u003e on continents is still ambiguous on a global scale.\u003c/p\u003e\n\u003cp\u003eIn addition, SO\u003csub\u003e2\u003c/sub\u003e emissions over the oceans have probably increased since the beginning of the 21st century, with the rapid increase in the global shipping industry under the backdrop of economic globalization. Europe, North America, and East Asia are the three most concentrated areas of ports in the world\u003csup\u003e17\u003c/sup\u003e. For several decades, large diesel engines burning heavy fuel oil (HFO) have dominated the energy systems of maritime shipping. These engines generate SO\u003csub\u003e2\u003c/sub\u003e, leading to a degradation of air quality in coastal areas\u003csup\u003e18\u003c/sup\u003e. With the growth of the shipping industry, air pollution from shipping has become an increasingly serious concern for both environmental quality and human health, especially in coastal regions\u003csup\u003e19, 20\u003c/sup\u003e. Additionally, the ocean acidification caused by SO\u003csub\u003e2\u003c/sub\u003e may be as detrimental as CO\u003csub\u003e2\u003c/sub\u003e, severely impacting the marine ecosystem\u003csup\u003e21, 22, 23, 24\u003c/sup\u003e. As a result, both domestic and international entities have formulated various measures aimed at reducing ship emissions\u003csup\u003e25, 26\u003c/sup\u003e. Under the International Maritime Organization (IMO) treaty known as the \u0026quot;International Convention For The Prevention Of Pollution\u0026quot; which came into effect in 2005, Europe, North America, and China responded by establishing emission control areas (ECAs). In these areas, the sulfur content of fuels used by vessels operating within them is regulated\u003csup\u003e27, 28, 29\u003c/sup\u003e. The majority of model-based studies have demonstrated the effectiveness of policy implementation in reducing SO\u003csub\u003e2\u003c/sub\u003e emissions from ships\u003csup\u003e30, 31, 32, 33, 34\u003c/sup\u003e. While these studies suggest that emission reduction regulations can yield substantial health and environmental benefits, they often focus on specific routes, ports, or regional sea areas of a country. Some studies contrarily indicated that despite the restrictions imposed by emission reduction regulations, SO\u003csub\u003e2\u003c/sub\u003e concentrations in specific ports continue to increase\u003csup\u003e33, 35\u003c/sup\u003e. In fact, the significant cost disparity between high-sulfur fuels (such as heavy fuel oil) and low-sulfur fuels (like marine gas oil and low-sulfur fuel oil) makes the transition from high-sulfur to low-sulfur fuels quite challenging\u003csup\u003e36, 37\u003c/sup\u003e. Due to a severe lack of marine SO\u003csub\u003e2\u003c/sub\u003e observations, there is little research on the actual observation of SO\u003csub\u003e2\u003c/sub\u003e, especially in different emission control areas and even on a global scale.\u003c/p\u003e\n\u003cp\u003eIn this study, we obtained the concentrations of global atmospheric SO\u003csub\u003e2\u003c/sub\u003e during 2005-2018 from OMI observation using our updated retrival algorithm, which includes on-orbit calibration, simulated irradiance, fitting window selection, \u0026lsquo;\u0026lsquo;soft calibration\u0026rdquo; and measurement error correction. The trends of atmospheric SO\u003csub\u003e2\u003c/sub\u003e over both continents and oceans were traced based on satellite observations. Besides, the influence of transport from oceans on SO\u003csub\u003e2\u003c/sub\u003e over marine cities and the effects of green competitiveness on the emission reduction of SO\u003csub\u003e2\u003c/sub\u003e over oceans were evaluated. This study will contribute to a better understanding of global SO\u003csub\u003e2\u003c/sub\u003e pollution trends and its drivers, especially over oceans.\u003c/p\u003e"},{"header":"Spatial and temporal patterns of global atmospheric SO2","content":"\u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, high global SO\u003csub\u003e2\u003c/sub\u003e concentrations on land are primarily distributed in Eastern China, Northern India, and the Eastern United States. China, especially in the North China Plain, had the highest SO\u003csub\u003e2\u003c/sub\u003e concentrations in the world from 2005 to 2016, which reached a peak of 2.03 DU on average in 2007. During the \"11th Five-Year Plan\" period (2006\u0026ndash;2010), China undertook a series of measures to improve energy efficiency and reduce emissions, including shutting down small thermal power units and installing flue gas desulfurization systems\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e, SO\u003csub\u003e2\u003c/sub\u003e in China has significantly decreased, gradually approaching the global average concentrations after 2017. Although there was a slight rebound after the 2011 financial crisis due to economic stimulus policies, emissions have steadily declined since 2012\u003csup\u003e3\u003c/sup\u003e. According to statistics, in 2015, the SO\u003csub\u003e2\u003c/sub\u003e emissions from coal-fired power generation in China witnessed a substantial reduction of 64.65% compared to the year of 2006\u003csup\u003e39\u003c/sup\u003e. Correspondingly, the average SO\u003csub\u003e2\u003c/sub\u003e concentrations decreased by 22.33% from 2006 to 2015.\u003c/p\u003e \u003cp\u003eSO\u003csub\u003e2\u003c/sub\u003e hotspots in the United States are primarily located in the Eastern region, originating from coal-fired power plants and industrial activities\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. From 2005 to 2011, the SO\u003csub\u003e2\u003c/sub\u003e concentrations in the United States decreased by 42.9%, possibly attributable to the \" Clean Air Act Amendments of 1990\"\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. In Europe, the SO\u003csub\u003e2\u003c/sub\u003e concentrations have kept at low levels with little variations in the past 14 years. Our research revealed that the average global SO\u003csub\u003e2\u003c/sub\u003e concentrations over land from 2005 to 2018 were almost unchanged, although the concentrations in China and the United States decreased by 51% and 24%, respectively. The rapid growth of SO\u003csub\u003e2\u003c/sub\u003e in India, Pakistan, and South America counteracted the effect of emission reduction by China and the United States. Particularly, over the past 14 years, SO\u003csub\u003e2\u003c/sub\u003e concentrations in India have increased by 57%. Since 2015, there has been a sharp increase in SO\u003csub\u003e2\u003c/sub\u003e concentrations in India, leading to India surpassing China as the world's largest anthropogenic SO2 emitter\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. Some studies attributed India's SO\u003csub\u003e2\u003c/sub\u003e emissions to the rapid expansion of coal-fired power plants\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e and the predominance of organic sulfur compounds in local coal\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e, which made transitioning to cleaner fuels challenging.\u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, from 2005 to 2018, although the SO\u003csub\u003e2\u003c/sub\u003e concentrations in China and the United States decreased by 55% and 24%, respectively, the global marine SO\u003csub\u003e2\u003c/sub\u003e concentrations increased by 79.2% at a rate of 6.1% per year. Over nearshore areas, the reduction in SO\u003csub\u003e2\u003c/sub\u003e concentrations in China and the United States can be attributed to restrictions on sulfur content in fuels within emission control areas. However, despite the establishment of the North Sea emission control area in Europe, marine SO\u003csub\u003e2\u003c/sub\u003e concentrations in European waters increased by 5% from 2005 to 2018, indicating limited control effectiveness. This could be because the European shipping industry is shifting from maritime to road transportation in response to tighter sulfur content limits. This shift may have adverse effects on the environmental performance of shipping, and further examination of the impact of ECA regulations is warranted\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. During this period, SO\u003csub\u003e2\u003c/sub\u003e concentrations over the Indian offshore area increased by 200%, with an annual growth rate of 8.5%, which was the largest contributor to the rapid increase in global marine SO\u003csub\u003e2\u003c/sub\u003e concentrations. The surge in maritime SO\u003csub\u003e2\u003c/sub\u003e concentrations in India could be attributed to the absence of emission control zones, resulting in a lack of effective oversight and regulation in coastal maritime areas. Besides, we observed significant SO\u003csub\u003e2\u003c/sub\u003e concentrations over the Persian Gulf, which may be associated with emissions from the region's oil and gas industry, gas flaring, and shipping\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. From 2005 to 2010, global marine SO\u003csub\u003e2\u003c/sub\u003e concentrations increased by 116.8%. During this period, the United States and China saw decreases of 19.8% and 22.7% in maritime SO\u003csub\u003e2\u003c/sub\u003e concentrations, while Europe experienced a 4% reduction. In contrast, India witnessed a significant 200% rise in maritime SO\u003csub\u003e2\u003c/sub\u003e concentrations. In the subsequent period from 2010 to 2018, global marine SO\u003csub\u003e2\u003c/sub\u003e concentrations showed a relatively stable fluctuation due to the tightening of emission control policies. The United States and China experienced reductions of 20.8% and 41.8% in SO\u003csub\u003e2\u003c/sub\u003e concentrations, respectively, while the airspace near Europe saw a 9.5% increase. India's maritime SO\u003csub\u003e2\u003c/sub\u003e concentrations remained almost unchanged during this period. Despite tightening ship fuel controls after 2010, maritime SO\u003csub\u003e2\u003c/sub\u003e concentrations in Europe have increased. Overall, the ECAs advocated by the IMO have substantiated their efficacy in curtailing and managing SO\u003csub\u003e2\u003c/sub\u003e emissions by ocean-going vessels in the United States and China. Particularly, the tightening of emission control policies in the U.S. and the establishment of emission control areas in China after 2016 accelerated maritime SO\u003csub\u003e2\u003c/sub\u003e control in both countries. However, it cannot be ruled out that within specific ports, SO\u003csub\u003e2\u003c/sub\u003e emissions generated by ocean-going vessels may contribute more to urban pollution than land-based emission sources\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"SO2 pollution over global major Ports","content":"\u003cp\u003e\u003cstrong\u003eSO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e \u003c/sub\u003e \u003cstrong\u003epollution over Chinese Ports\u003c/strong\u003e. According to the 2016 World Port Rankings of the American Association of Port Authorities\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e, there are 19 ports located in Europe, North America, and Asia in the top 20 ports, with a proportion of 75% for Asira and 45% for China. In 2018, China's port throughput surged by 247% compared to 2005. Notably, Shanghai and Guangzhou ports secured top positions in the global throughput rankings. In response to the call of the IMO and to address pollution in Chinese waters, China established ECAs in 2016, requiring vessels at major ports within these control areas to use fuels with a sulfur content not exceeding 0.5% (m/m) since 2007\u003csup\u003e28\u003c/sup\u003e. Shanghai and Guangzhou ports are both international ports located within established emission control areas in China. As shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e, the Shanghai and Guangdong ports show a continuous decrease in SO\u003csub\u003e2\u003c/sub\u003e concentrations on both land and marine. China's desulfurization policies led to a substantial decrease in land-based SO\u003csub\u003e2\u003c/sub\u003e concentrations at Shanghai Port from 2007 onwards. A minor uptick in SO\u003csub\u003e2\u003c/sub\u003e concentrations occurred in 2011 due to economic stimulus policies after the financial crisis. Since 2012, Shanghai Port's land-based SO\u003csub\u003e2\u003c/sub\u003e concentrations has rapidly decreased. By 2017, land and marine SO\u003csub\u003e2\u003c/sub\u003e concentrations had become comparable. In 2017, Shanghai's maritime SO\u003csub\u003e2\u003c/sub\u003e concentrations decreased by 12.4% compared to 2016 due to emission reduction policies. Additionally, Guangzhou Port's SO\u003csub\u003e2\u003c/sub\u003e concentrations mirror Shanghai Port's trends. Compared to Shanghai, Guangzhou's onshore SO2 concentrations began decreasing after 2006 without a notable rise after the financial crisis. Notably, Guangzhou Port exhibits environmental advantages over Shanghai. After 2014, Guangzhou's onshore SO\u003csub\u003e2\u003c/sub\u003e concentrations swiftly declined. By 2016, onshore and offshore SO\u003csub\u003e2\u003c/sub\u003e concentrations had aligned. Compared to 2016, fueled by emission reduction policies, Guangzhou witnessed a significant 31.7% drop in marine SO\u003csub\u003e2\u003c/sub\u003e concentrations in 2017. From 2005 to 2018, maritime SO\u003csub\u003e2\u003c/sub\u003e concentrations in Shanghai and Guangzhou ports decreased by 78.1% and 79.8%, respectively, signifying a notable improvement in China's maritime SO\u003csub\u003e2\u003c/sub\u003e concentrations. Although land-based SO\u003csub\u003e2\u003c/sub\u003e concentrations in these ports remain higher than maritime concentrations, the two have gradually approached parity over time. To explore the influence of SO\u003csub\u003e2\u003c/sub\u003e over oceans on air quality in port cities, a potential source contribution function (PSCF) analysis was conducted based on the in-situ observations of ground-level SO\u003csub\u003e2\u003c/sub\u003e. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e indicates that high SO\u003csub\u003e2\u003c/sub\u003e concentrations in Guangzhou Port may result from land-based sources, while Shanghai Port faces elevated SO\u003csub\u003e2\u003c/sub\u003e concentrations from the maritime direction. This highlights the need for stricter regulatory policies, particularly for Shanghai Port.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e \u003c/sub\u003e \u003cstrong\u003epollution over Indian Ports.\u003c/strong\u003e According to the 2016 World Port Ranking by the American Association of Port Authorities\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e, the Port of Mumbai in India was the only one among the top 30 ports, ranking 30th. We chose the ports of Chennai and Mumbai, located on the southeast and west coasts of India, respectively. As shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e, there is an increasing trend in both terrestrial and marine SO\u003csub\u003e2\u003c/sub\u003e concentrations in the ports of Mumbai and Chennai. For example, between 2005 and 2018, marine SO\u003csub\u003e2\u003c/sub\u003e concentrations increased by 110.9% in Mumbai and by 183.6% in Chennai. Due to the lack of emission regulations, SO\u003csub\u003e2\u003c/sub\u003e emissions from oceangoing vessels are unrestricted. Compared to Mumbai, Chennai's SO\u003csub\u003e2\u003c/sub\u003e concentrations increased even more rapidly, likely due to lower port transportation efficiency\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e. During the economic crisis from 2007 to 2008, SO\u003csub\u003e2\u003c/sub\u003e concentrations increased, possibly influenced by unregulated human activities in maritime areas during the economic downturn.\u003c/p\u003e\n\u003cp\u003eThe maritime SO\u003csub\u003e2\u003c/sub\u003e concentrations in Mumbai exceeded those on land in 2013 and 2018. Unfortunately, due to the delayed establishment of SO\u003csub\u003e2\u003c/sub\u003e observation stations in India, ground-level data for this period is unavailable. Therefore, we can only select 2020 for the PSCF analysis of Indian ports to assess the contribution of marine and terrestrial SO\u003csub\u003e2\u003c/sub\u003e sources. As shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e, the high concentrations of SO\u003csub\u003e2\u003c/sub\u003e in the ports of Mumbai and Chennai are largely attributed to maritime pollution. The primary source of SO\u003csub\u003e2\u003c/sub\u003e emissions in Indian ports is associated with maritime activities\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e. Hence, the Indian government must urgently establish effective control measures to improve the environmental conditions in port cities, balancing environmental concerns with economic development.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e \u003c/sub\u003e \u003cstrong\u003epollution over European and American ports.\u003c/strong\u003e Over the decades, ports in North America and Europe had exhibited a complex pattern of growth, stagnation, decline, or moderate growth\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e. In this study, we selected the ports of New York and Savannah in the United States, Rotterdam in the Nederlands and Valencia in Spain for further research. New York and Savannah are both located on the East Coast of the United States and must adhere to regulations regarding fuel sulfur content in the North American Emission Control Area. Since August 1, 2010, vessels operating within this region have been required to use fuel with a sulfur content not exceeding 1.00% (m/m). This limit was further reduced to 0.10% (m/m) on January 1, 2015. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e demonstrates that in the United States, SO\u003csub\u003e2\u003c/sub\u003e concentrations on land are consistently higher than those over the ocean. The SO\u003csub\u003e2\u003c/sub\u003e concentrations decreased on land in New York Port, while remaining stable in Savannah Port. Both ports experienced an increase in marine SO\u003csub\u003e2\u003c/sub\u003e concentrations in 2008, with New York rising by 9.3% and Savannah by 62% compared to 2007, possibly due to relaxed environmental controls during the financial crisis. Following the implementation of sulfur reduction policies in 2010 and further tightening in 2015, port areas, especially New York Harbor, witnessed notable declines in marine SO\u003csub\u003e2\u003c/sub\u003e concentrations. Specifically, there was a reduction of 20.1% in 2010 and 10.5% in 2015. However, after 2010, New York's marine SO\u003csub\u003e2\u003c/sub\u003e concentrations gradually increased, showing a trend of convergence between marine and land-based pollution, particularly in 2017. Nevertheless, the primary source of SO\u003csub\u003e2\u003c/sub\u003e concentrations in U.S. port cities comes from land. In our PSCF analysis, no instances were identified where high concentrations of SO\u003csub\u003e2\u003c/sub\u003e in ports originated from the ocean. Rotterdam, which is situated in the Netherlands, is under the control of the North Sea ECAs, which have been effective since November 22, 2007, in accordance with Annex VI of the International Convention for the Prevention of Pollution from Ships. This regulation mandates a sulfur content of 1.00% (m/m) for fuels\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e. Valencia is a Spanish port located in the Mediterranean, it is not within the jurisdiction of the North Sea ECA. Rotterdam and Valencia ports exhibit similar trends in SO\u003csub\u003e2\u003c/sub\u003e concentrations. During the financial crisis, both ports experienced increases in both land and marine SO\u003csub\u003e2\u003c/sub\u003e concentrations. Despite the initial effectiveness of the 2010 policy implementation, the control proved to be short-lived. Since 2011, pollution has continued to increase significantly, with Rotterdam and Valencia experiencing a 70.5% and 46.1% rise, respectively, in nearshore SO\u003csub\u003e2\u003c/sub\u003e concentrations in 2014 compared to pre-sulfur limit levels in 2009. This could be attributed to the impact of the Russian oil crisis\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e. However, in reality, after 2015, SO\u003csub\u003e2\u003c/sub\u003e concentrations in both ports decreased rapidly. By 2018, Rotterdam and Valencia ports witnessed a reduction of 60.1% and 46.8%, respectively, compared to 2014.\u003c/p\u003e"},{"header":"The influence of port green competitiveness on SO2 over port cities","content":"\u003cp\u003eWith the rapid development of the shipping industry against the background of economic globalization, SO\u003csub\u003e2\u003c/sub\u003e concentrations over oceans would continue to increase if no measures were taken to reduce emissions\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e. Fortunately, port green competitiveness, which includes optimizing port infrastructure and functions, as well as developing energy-saving and emission reduction technologies, could reduce the emission per TEU and further mitigate air pollution over the offshore areas of the port cities\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e. Here we compare the green competitiveness of ports among the global major ports by examining the SO\u003csub\u003e2\u003c/sub\u003e concentrations per TEU. A smaller numerical value indicates that the port has greater green competitiveness, effectively balancing shipping trade and environmental benefits. As shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e, the ranking of green competitiveness from highest to lowest is Guangzhou Port, Shanghai Port, Savannah Port, Rotterdam Port, New York Port, Valencia Port, Mumbai Port, and Chennai Port. The SO\u003csub\u003e2\u003c/sub\u003e concentrations per TEU in Shanghai dropped significantly by 90.6% from 2005 to 2018. Similarly, Guangzhou initially maintained stability but witnessed a noteworthy 73.3% reduction from 2016 to 2018 following the implementation of emission control areas. From 2005 to 2018, SO\u003csub\u003e2\u003c/sub\u003e concentrations per TEU declined by 32.8% and 45.8% in Savannah and New York ports, respectively. Rotterdam and Valencia in Europe experienced a slight increase in SO\u003csub\u003e2\u003c/sub\u003e concentrations, but the concentrations per unit throughput decreased significantly by 60.2% and 73.5%, respectively. Conversely, Mumbai and Chennai witnessed an increase of 9.8% and 29.7% in SO\u003csub\u003e2\u003c/sub\u003e concentrations per TEU, respectively. Compared to Guangzhou, Shanghai Port handles more containers and has higher transportation efficiency, but exhibits lower green competitiveness\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e. Shanghai Port generates more SO\u003csub\u003e2\u003c/sub\u003e concentrations per TEU than Guangzhou. However, through continuous emission control efforts, Shanghai Port's SO\u003csub\u003e2\u003c/sub\u003e concentrations per TEU decreased to a level comparable to that of Guangzhou. Despite the increase in throughput at Indian ports in recent years, container terminals in India still have untapped throughput potential\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e54\u003c/span\u003e\u003c/sup\u003e.The green competitiveness of both Indian ports is lower than that of China, with Chennai port having the lowest green competitiveness and a decreasing trend. The SO\u003csub\u003e2\u003c/sub\u003e concentrations per TEU steadily increases. Furthermore, the New York and Savannah ports exhibit greater green competitiveness than the European ports in Rotterdam and Valencia, with slightly lower SO\u003csub\u003e2\u003c/sub\u003e concentrations per TEU. Compared to Rotterdam, although the SO\u003csub\u003e2\u003c/sub\u003e concentrations levels in Valencia are not high, its green competitiveness is lower.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eObservational data.\u003c/strong\u003e We apply an optimal estimation algorithm originally developed at the Smithsonian Astrophysical Observatory (SAO) for retrieving ozone profiles and tropospheric ozone from the GOME and OMI instruments\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e to retrieve SO\u003csub\u003e2\u003c/sub\u003e. The algorithm used for retrieval and detailed information on ground validation can be found in our previous work\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e. OMI was launched in July 2004 on board the Aura satellite, of the National Aeronautics and Space Administration (NASA), which is in a sun-synchronous ascending polar orbit at 705 km altitude with a 13:45 local equator-crossing time. OMI covers a spectral range from ultraviolet to visible, enabling daily global coverage\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e57\u003c/span\u003e\u003c/sup\u003e.We regridded OMI SO\u003csub\u003e2\u003c/sub\u003e data into a latitude-longitude grid of 0.1\u0026deg; \u0026times; 0.1\u0026deg;. To ensure the reliability of the analysis results, we excluded satellite SO\u003csub\u003e2\u003c/sub\u003e observations with poor quality flags, such as those associated with cloudy scenes (cloud radiance fraction\u0026thinsp;\u0026gt;\u0026thinsp;0.3) and high-latitude regions (latitude\u0026thinsp;\u0026gt;\u0026thinsp;60). The research presented here spans from 2005 to 2018. To enhance the accuracy of the SO\u003csub\u003e2\u003c/sub\u003e data, a multistep process, including error screening and stripe removal, was conducted. To mitigate the impact of volcanic eruptions on the statistical outcomes, data corresponding to periods of significant volcanic activity were excluded\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e58\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAnalysis of wind screening.\u003c/strong\u003e To mitigate the influence of land-sea interactions on marine SO\u003csub\u003e2\u003c/sub\u003e concentrations, wind data within half an hour of OMI satellite passes were collated from the ERA5 wind speed dataset. Specifically, for the assessment of marine SO\u003csub\u003e2\u003c/sub\u003e concentrations, the influence of strong winds blowing from the land toward the ocean was excluded. Simultaneously, when evaluating land-based SO\u003csub\u003e2\u003c/sub\u003e concentrations, the data excluded the impact of strong winds blowing from the sea toward the land.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe wind data utilized in this study is sourced from the fifth generation of the European Centre for Medium-Range Weather Forecasts atmospheric reanalysis (ERA5) datasets\u003csup\u003e59\u003c/sup\u003e (available from https://climate.copernicus.eu/climate-reanalysis, last accessed on July 25, 2023). The wind variables were acquired at a moderate resolution of 0.25\u0026deg;, encompassing u-components and v-components of the 10 m wind (u and v). The throughput data used in this study is sourced from the CEIC database (available at https://www.ceicdata.com.cn/zh-hans, last accessed on July 25, 2023). The Potential Source Contribution Function (PSCF) analysis employed the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model from the NOAA Air Resources Laboratory, available at http://www.ready.noaa.gov. The throughput data selected for this study is a global dataset covering major ports from 2005 to 2018. To evaluate a port\u0026apos;s green competitiveness, divide the port\u0026apos;s SO\u003csub\u003e2\u003c/sub\u003e concentrations by its throughput. The global SO\u003csub\u003e2\u003c/sub\u003e concentrations data used in this study are stored at the Supercomputing Center of the University of Science and Technology of China due to its large data storage and can be made available from the corresponding author upon request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was supported by the National Natural Science Foundation of China (42225504), the National Key Research and Development Program of China (2022YFC3700100), the Key Research Program of Frontier Sciences, CAS (No. ZDBS-LY-DQC008), the Youth Innovation Promotion Association of CAS (2021443), the Major Project of High Resolution Earth Observation System (30-Y60B01-9003-22/23), the New Cornerstone Science Foundation through the XPLORER PRIZE (2023-1033), the HFIPS Director\u0026rsquo;s Fund (BJPY2022B07 and YZJJQY202303), and the Hefei Comprehensive National Science Center.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eContributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eQihou Hu and Cheng Liu contributed to the design of the study, whereas Ziwei Li authored this paper. Xiaohan Wang, Jin Ye, Yizhi Zhu, and Ran Zhao participated in the data analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZipper CE, Gilroy L. Sulfur Dioxide Emissions and Market Effects under the Clean Air Act Acid Rain Program. Journal of the Air \u0026amp; Waste Management Association 2011, 48(9): 829\u0026ndash;837.\u003c/li\u003e\n\u003cli\u003eHoesly RM, Smith SJ, Feng L, Klimont Z, Janssens-Maenhout G, Pitkanen T, \u003cem\u003eet al.\u003c/em\u003e Historical (1750\u0026ndash;2014) anthropogenic emissions of reactive gases and aerosols from the Community Emissions Data System (CEDS). 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Environ Sci Technol 2013, 47(24): 13993-14000.\u003c/li\u003e\n\u003cli\u003eTournigand P-Y, Cigala V, Lasota E, Hammouti M, Clarisse L, Brenot H, \u003cem\u003eet al.\u003c/em\u003e A multi-sensor satellite-based archive of the largest SO2volcanic eruptions since 2006. \u003cem\u003eEarth System Science Data\u003c/em\u003e 2020, 12(4): 3139\u0026ndash;3159.\u003c/li\u003e\n\u003cli\u003eHersbach H, Bell B, Berrisford P, Hirahara S, Hor\u0026aacute;nyi A, Mu\u0026ntilde;oz-Sabater J, \u003cem\u003eet al.\u003c/em\u003e The ERA5 global reanalysis.\u0026nbsp;\u003cem\u003eQuarterly Journal of the Royal Meteorological Society\u003c/em\u003e 2020, 146(730): 1999\u0026ndash;2049.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-3996146/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3996146/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSulfur dioxide(SO\u003csub\u003e2\u003c/sub\u003e) is a major air pollutant over oceans, which exacerbates ecological and environmental issues like acid rain, ocean acidification, and air pollution. Over the past few decades, the robust growth of the shipping industry has led to a continuous increase in SO\u003csub\u003e2\u003c/sub\u003e emissions by ocean-going vessels. However, the trend of global SO\u003csub\u003e2\u003c/sub\u003e concentrations over the oceans is unclear due to rare in-situ observations at marine sites. Hyperspectral satellite remote sensing is an ideal method to obtain the spatiotemporal distribution of SO\u003csub\u003e2\u003c/sub\u003e, whereas accurately retrieving SO\u003csub\u003e2\u003c/sub\u003e concentrations in the marine atmosphere has traditionally been challenging due to issues like high noise levels and limitations in detecting lower concentrations close to the detection limits. In this study, we retrieved global SO\u003csub\u003e2 \u003c/sub\u003econcentrations, particularly over oceans, from the space-borne Ozone Monitoring Instrument (OMI) through a series of remote sensing algorithm optimizations from spectral calibration to retrieve. Our research revealed that the average global SO\u003csub\u003e2\u003c/sub\u003e concentrations over lands almost unchanged although the concentrations in China and the United States decreased by 51% and 24%, respectively. Nevertheless, global SO\u003csub\u003e2\u003c/sub\u003e concentrations over oceans increased at an annual rate of 6.1%, with an increase over the inshore regions of India of 200% from 2005 to 2018, despite a notable decrease over inshore China at an annual rate of 4.2%. Our study revealed that the increase in shipments will not necessarily lead to an increase in SO\u003csub\u003e2\u003c/sub\u003e. Under green competitiveness, SO\u003csub\u003e2\u003c/sub\u003e per TEU over inshore China continuously decreased, which induced a great decrease in SO\u003csub\u003e2\u003c/sub\u003e with a 214% increase in throughput.\u003c/p\u003e","manuscriptTitle":"Hyperspectral satellite reveals an unexpected increase of global SO2 over oceans over the last two decades","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-06 11:07:45","doi":"10.21203/rs.3.rs-3996146/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f653c126-b437-40fa-849d-d2698936006b","owner":[],"postedDate":"March 6th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":29166048,"name":"Earth and environmental sciences/Environmental sciences/Environmental impact"},{"id":29166049,"name":"Earth and environmental sciences/Environmental social sciences/Environmental impact"}],"tags":[],"updatedAt":"2024-03-27T14:47:24+00:00","versionOfRecord":[],"versionCreatedAt":"2024-03-06 11:07:45","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3996146","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3996146","identity":"rs-3996146","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}