Emissions of trace gases and particles from two ships in the southern Atlantic Ocean

Measurements were made of the emissions of particles and gases from two diesel-powered ships in the southern Atlantic Ocean off the coast of Namibia. The measurements are used to derive emission factors from ships of three species not reported previously, namely, black carbon, accumulation-mode particles, and cloud condensation nuclei (CCN), as well as for carbon dioxide, carbon monoxide (CO), methane (CH4), non-methane hydrocarbons, sulfur dioxide (SO2), nitrogen oxides (NOx), and condensation nuclei. The effects of fuel grade and engine power on ship emissions are discussed. The emission factors are combined with fuel usage data to obtain estimates of global annual emissions of various particles and gases from ocean-going ships. Global emissions of black carbon, accumulation-mode particles, and CCN from ocean-going ships are estimated to be 19–26 Gg yr−1, (4.4–6.1)×1026 particles yr−1, and (1.0–1.5)×1026 particles yr−1, respectively. Black carbon emissions from ocean-going ships are 0.2% of total anthropogenic emissions. Emissions of NOx and SO2 from ocean-going ships are 10–14% and 3–4%, respectively, of the total emissions of these species from the burning of fossil fuels, and 40% and 70%, respectively, of the total emissions of these species from the burning of biomass. Global annual emissions of CO and CH4 from ocean-going ships are 2% and 2–5%, respectively, of natural oceanic emissions of these species.