Investigation of the airborne submicrometer particles emitted by dredging vessels using a plume capture method

• We demonstrate a system for measuring emissions factors in ship plumes.
• We measure emission factors and particle size distributions for two dredgers.
• The method is shown to work well at dilutions expected during airborne sampling.
• The results are independent of plume dilution as required for remote sampling.
• We examine relationships between the emission factors.

A method for investigating ship emissions, known as the plume capture and analysis system (PCAS) is described. The PCAS is applied to the task of measuring airborne pollutant emission factors (EFs) and particle size distributions aboard two dredgers, although the technique is also suitable for remote measurements. EFs were measured relative to the fuel consumption using the fuel combustion derived plume CO2. Each measurement typically took 6 min to complete and during one day, 40–50 measurements were possible. EFs for particle number (PN), NOx, SO2, and PM2.5 were independent within a targeted dilution factor range of 50–1000 suitable for onboard and remote sampling.For the Amity, the EF ranges were PN: 2.2–9.6 × 1015 (kg-fuel)−1; NOx: 35–72 g (NO2) (kg-fuel)−1, SO2 0.6–1.1 g (SO2) (kg-fuel)−1and PM2.5: 0.7–6.1 g (PM2.5) (kg-fuel)−1. For the Brisbane they were PN: 1.0–1.5 × 1016 (kg-fuel)−1, NOx: 3.4–8.0 g (NO2) (kg-fuel)−1, SO2: 1.3–1.7 g (SO2) (kg-fuel)−1 and PM2.5: 1.2–5.6 g (PM2.5) (kg-fuel)−1.Particle number emission factors as a function of size as well as the count median diameter (CMD), and geometric standard deviation of the size distributions are provided. This size distributions were consistently uni-modal in the range below 500 nm for both vessels, and this CMD always lay within the accumulation mode range.