Determining Volatile Organic Compounds (VOC) and Particulate Matter (PM1) shipping Emission Factors from land-based, high time resolution observations in an Emission Control Area of northern France

Exhaust gases and particles from ships are a significant and growing contributor to the total emissions from transport. Globally, the sector is a significant contributor to global emissions of NO_x and SO₂.^1,2 Recently, the International Maritime Organisation (IMO) has reduced the sulphur content of marine fuels globally through Annex VI of MARPOL, and sulphur emissions are further restricted in specific Sulphur Emission Control Areas (SECA), such as the English Channel between France and the UK. Similarly, NO_x emission limits have been set for ships built after 2016 in NO_x Emission Control Areas (NECA).

However, other pollutants such as Volatile Organic Compounds (VOCs) or Particulate Matter (PM), are not regulated in relation to ship emissions. Here, we present new emission factors (EFs) for regulated and non-regulated pollutants from ship emissions derived from a land-based measurement campaign in the port of Dunkirk, France in the framework of the PIRATE and SHIPAIR projects. A comprehensive suite of gas-phase and particulate-phase pollutants was investigated with a focus on VOCs, based on PTR-MS measurements, and PM₁ composition, based on AMS measurements. About 150 plumes were detected from three similar ferries, and EFs were calculated for 84 pollutants.

Despite being located in an Emission Control Area (ECA) for SO_x and NO_x, we show that SO₂ remains a reliable tracer of ship emissions for land-based measurements in the port area. A sensitivity test of the EF with respect to background considerations was performed, showing significant discrepancies depending on the method of background calculation. This underlines the importance of explicit background considerations in EF calculations.

The EF of the particulate phase is dominated by the organic fraction (OA), between 0.05 and 15.88 g/kg fuel, two to three orders of magnitude higher than nitrate and sulphate. Particle Number (PN) EFs vary between 1.08·10¹⁴ and 1.60·10¹⁷ part./kg_fuel, with a unimodal mode centred at 90 nm. The VOC EFs are dominated by oxygenated species, such as acetaldehyde (30.7 - 404.8 mg/kg fuel). The second most emitted group of VOCs are C₅ cyclic compounds, of which cyclopentane has the highest EF (12.8 - 439.6 mg/kg fuel). Aromatic VOCs, such as benzene, toluene and xylenes, are also detected, with EFs below 80 mg/kg fuel. We also present the emissions as a function of the navigation phases, suggesting that certain pollutants are emitted more during the arrival of the ferries than during their departure. In particular, the speciated VOC EFs are expected to improve current emission inventories.

References :

(1) Aakko-Saksa, P. T. et al. Reduction in greenhouse gas and other emissions from ship engines: Current trends and future options. Progress in Energy and Combustion Science 94, 101055 (2023). (2) Lehtoranta, K. et al. Particulate Mass and Nonvolatile Particle Number Emissions from Marine Engines Using Low-Sulfur Fuels, Natural Gas, or Scrubbers. Environmental Science and Technology 53, 3315–3322 (2019).