RESUMEN
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.
RESUMEN
The processes affecting photochemical reactions and regional transport of ozone and its precursors in ambient air are very complicated. In this study, statistical analysis of the spatial and temporal distributions of ozone pollution in Zhoushan was carried out based on monitoring data from state monitoring stations in Zhoushan in 2014. Specifically, ozone formation was simulated by CMAQ (the community multiscale air quality) model, and the source contribution rate was calculated using the Integrated Source Apportionment Method (ISAM) source tracking algorithm. The results showed that ozone pollution was more severe in spring and autumn than in summer and winter, and the highest ozone concentrations mostly appeared during 13:00-15:00 in the afternoon. Putuo Station had the highest ozone concentration while Lincheng Station, located in the downtown area of the city, had the lowest ozone concentration. The overall average ozone concentration was not high; however, peak concentrations that exceeded the standards usually occurred, which occurs most often in May. Local ozone formation in Zhoushan City is controlled by the VOC concentration, and source tracking results showed that non-local sources accounted for 69.46% of the total contribution. Among local emission sources, fuel burning boiler sources, industry process sources, on-road mobile sources, and non-road mobile sources made similar contributions to ozone formation. Moreover, they showed significant characteristics of a port city. The contribution rates from shipping sources, petrochemical sources, and storage and transportation sources were 4.45%, 1.01%, and 1.80%, respectively. In conclusion, control of the ozone pollution in Zhoushan City should be based on simultaneous reduction and coordinated prevention involving multiple sources (VOCs as the main one) both locally and in surrounding areas.