Influence of vessel characteristics and atmospheric processes on the gas and particle phase of ship emission plumes: in situ measurements in the Mediterranean Sea and around the Arabian Peninsula

Abstract

Abstract. A total of 252 emission plumes of ships operating in the Mediterranean Sea and around the Arabian Peninsula were investigated using a comprehensive dataset of gas- and submicron-particle-phase properties measured during the 2-month shipborne AQABA (Air Quality and Climate Change in the Arabian Basin) field campaign in summer 2017. The post-measurement identification of the corresponding ship emission events in the measured data included the determination of the plume sources (up to 38 km away) as well as the plume ages (up to 115 min) and was based on commercially available historical records of the Automatic Identification System. The dispersion lifetime of chemically inert CO2 in the ship emission plumes was determined as 70±15 min, resulting in levels indistinguishable from the marine background after 260±60 min. Emission factors (EFs) as quantities that are independent of plume dilution were calculated and used for the investigation of influences on ship emission plumes caused by ship characteristics and the combustion process as well as by atmospheric processes during the early stage of exhaust release and during plume ageing. Combustion efficiency and therefore emission factors of black carbon and NOx were identified to depend mostly on the vessel speed and gross tonnage. Moreover, larger ships, associated with higher engine power, were found to use fuel with higher sulfur content and have higher gas-phase SO2, particulate sulfate, particulate organics, and particulate matter EFs. Despite the independence of EFs of dilution, a significant influence of the ambient wind speed on the particle number and mass EFs was observed that can be traced back to enhanced particle coagulation in the case of slower dilution and suppressed vapour condensation on particles in the case of faster dilution of the emission plume. Atmospheric reactions and processes in ship emission plumes were investigated that include NOx and O3 chemistry, gas-to-particle conversion of NOx and SO2, and the neutralisation of acids in the particle phase through the uptake of ambient gas-phase ammonia, the latter two of which cause the inorganic particulate content to increase and the organic fraction to decrease with increasing plume age. The results allow for us to describe the influences on (or processes in) ship emission plumes quantitatively by parameterisations, which could be used for further refinement of atmospheric models, and to identify which of these processes are the most important ones.

Measurements of carbonyl compounds around the Arabian Peninsula: overview and model comparison

“…This indicates that the direct biogenic acetaldehyde emissions from the ocean are probably insufficient to explain the measured acetaldehyde. More likely, acetaldehyde and other small carbonyl compounds can be formed in the sea, especially in the surface microlayer (SML) via photodegradation of coloured dissolved organic matter (CDOM) (Kieber et al, 1990;Zhou and Mopper, 1997;Ciuraru et al, 2015). Zhou and Mopper (1997) calculated the exchange direction of small carbonyls based on measurement results and identified that the net flux of acetaldehyde was from the sea to the air, whereas formaldehyde was taken up by the sea.…”

Net ozone production and its relationship to nitrogen oxides and volatile organic compounds in the marine boundary layer around the Arabian Peninsula

“…Low-NO x environments such as the clean MBL and the lower free troposphere are considered net O 3 destruction regimes, whereas the upper troposphere and areas with anthropogenic emissions of O 3 precursors are considered regions of net O 3 production (Klonecki and Levy, 1997;Bozem et al, 2017). Measurements performed in the Houston Ship Channel revealed NOPRs of the order of several tens of part per billion per hour (Chen et al, 2010;Ren et al, 2013).…”

“…However, in Asia, India and the Middle East, NO x emissions have substantially increased during the last decade so that the global NO x burden has essentially remained constant (Miyazaki et al, 2017). NO x emissions from ocean-going vessels have attracted considerable attention, as they are reported to account for 15 % of the global NO x emission burden (Celik et al, 2020). Model calculations suggest that the Arabian Gulf, with an estimated annual NO x emission density of about 1 ton km −2 from ship traffic, is among the regions with the highest NO x emission densities worldwide (Johansson et al, 2017).…”

Reactive nitrogen around the Arabian Peninsula and in the Mediterranean Sea during the 2017 AQABA ship campaign

“…The slope is similar to that derived by Celik et al (2020) (2.7 ± 0.8) who examined single ships plumes in a more detailed analysis and with literature values that range from 6.8 ± 6.3 near the coast of Texas (Williams et al, 2009) to 11.2 ± 10.9 (Diesch et al, 2013) at the Elbe river near Hamburg/Germany. In comparison to Celik et al (2020), however, the two other literature studies only sampled very fresh and unprocessed ship plumes, from a distance of less than ca. 5 kilometres to the emission source.…”