Impact of Shipping Emission Regulations on Atmospheric Vanadium Along U.S. North Atlantic Coast and Over the Western North Atlantic Ocean

Kurzfassung

Ship emissions from high sulfur residual fuel oil (RFO) are a major source of air pollution in coastal and marine environments. Emissions include sulfur oxides as well as fine particulate matter (PM2.5) enriched in vanadium (V) and nickel (Ni). Near coasts, the International Maritime Organization (IMO) has implemented Sulfur Emission Control Areas where ships must operate on low sulfur marine fuel. In this study, we integrate 15 years of chemically speciated PM2.5 data collected at IMPROVE sites along the U.S. east coast with in-cloud observations from the 2020–2022 NASA ACTIVATE flight campaign over the northwest Atlantic to assess the impact of maritime regulations on ambient V concentrations. We find statistically significant reductions in coastal atmospheric V (80%–89%) after IMO regulation implementation. Reductions in particulate Ni (67%–79%) and sulfate (53%–59%) levels were also observed. While the V/Ni ratio is traditionally used as a tracer for RFO-operated marine engines, we show measurements in shipping lanes comparable to those in areas not affected by shipping emissions. This means that V/Ni is no longer a reliable marker for detecting plume exhaust from ships running on low-sulfur fuel, while V alone represents a stronger tracer. Under a low-sulfur fuel regime, cloud water V concentrations over the northwest Atlantic are an order of magnitude lower than in PM2.5 at coastal sites. Vanadium concentrations above the 75th percentile were observed in cloud droplets enriched in non-sea-salt sulfate (nss sulfate) and nitrate, suggesting a potential role of ship-emitted vanadium in catalyzing in-cloud oxidation reactions.