Multiple-Year Changes (2014-2018) in Particulate Vanadium Linked to Shipping Regulations in the World's Largest Port Region

China introduced an emission control area (ECA) along the coastline of the Yangtze River Delta (YRD) region in 2016 in a bid to reduce its shipping emissions. Performed at a costal site in the YRD region from 2014 to 2018, we found a significant reduction (16-22%, p < 0.01) in vanadium concentrations, the exclusive marker for heavy fuel oil combustion, after the full-scale implementation of lower sulfur fuel change for marine ships. Another site closer to the coastline showed a larger reduction (24- 30%, p < 0.01) during the corresponding period. The reduction of vanadium was consistent with an overall decrease rate of 17% in the annual SO2 concentrations of 10 sites across the region from 2016 to 2017. We thus provide a robust assessment of the positive effects of regulating shipping emissions on air quality in coastal China. The future trajectories of shipping-related emissions are also discussed.