Enhanced emission of intermediate-volatility/semi-volatile organic matter in gas and particle phases from ship exhausts with low-sulfur fuels

The widespread utilization of low-sulfur fuels in compliance with global sulfur limit regulations has significantly mitigated the emissions of sulfur dioxide (SO2) and particulate matter (PM) on ships. However, significant uncertainties still persist regarding the impact on intermediate-volatility/semi-volatile organic compounds (I/SVOCs). Therefore, onboard tests of I/SVOCs from three ocean-going vessels (OGVs) and four inland cargo ships (ICSs) with low-sulfur fuels (<0.50 % m/m) in China were carried out in this study. Results showed that the emission factors of total I/SVOCs were 881 ± 487, 1181 ± 421, and 1834 ± 667 mg per kg fuel for OGVs with heavy fuel oil (HFO), marine gas oil (MGO), and ICSs with no. 0 diesel, respectively. The transition from low-sulfur-content (<0.50 % m/m) to ultra-low-sulfur-content (<0.10 % m/m) fuels had evidently enhanced the emission factor of I/SVOCs, with unignorable contributions from particle-phase I/SVOCs, thereby further amplifying the secondary organic aerosol formation potential (SOAFP). Fuel type, engine type, and operating conditions comprehensively influenced the emission factor level, compositions, and volatility distribution of I/SVOCs. Notably, a substantial proportion of fatty acids had been identified in ship exhausts, necessitating heightened attention. Furthermore, organic diagnostic markers of hopanes, in conjunction with the C18:0-to-C14:0 acid ratio, could be considered potential markers for HFO exhausts. The findings suggest that there is a need to optimize the implementation of a global policy on ultra-low-sulfur oil in the near future.