The impact of photochemical aging on secondary aerosol formation from a marine engine

Ship traffic is known as one important contributor to air pollution. Recent regulations aimed at reducing sulfur oxide (SOx) pollution by limiting the fuel sulfur content (FSC) may also decrease fresh particulate matter (PM) emitted from ships. However, there is a knowledge gap regarding how the FSC affects secondary aerosol formation. Aerosol particle emissions from a research ship engine operated with either low sulfur heavy fuel oil (LS-HFO) (FSC=0.5%) or marine gas oil (MGO) (FSC=0.01%), were studied. The emissions were photochemically processed in the oxidation flow reactor “PEAR” to equivalent photochemical aging between 0-9 days in the atmosphere. It was found that FSC had no significant impact on secondary organic aerosol (SOA) formation after 3 days of aging, at 1.8±0.4g/kg and 1.5±0.4g/kg for MGO and LS-HFO, respectively. Furthermore, the composition and oxidative pathways remained similar regardless of FSC. However, as a result of the higher secondary SO4 formation and fresh aerosol emissions, LS-HFO had significantly higher total PM1 than MGO. Black carbon (BC) specifically was found to be 3 times higher for HFO than MGO. While the fuel with the lower sulfur content produces significantly less PM, the SOA formation remains similar regardless of FSC.