Shipborne measurements of ClNO 2 in the Mediterranean Sea and around the Arabian Peninsula during summer

Eger, Philipp G.; Friedrich, Nils; Schuladen, Jan; Shenolikar, Justin; Fischer, Horst; Tadic, Ivan; Harder, Hartwig; Martinez, Monica; Rohloff, Roland; Tauer, Sebastian; Drewnick, Frank; Fachinger, Friederike; Brooks, James; Darbyshire, Eoghan; Sciare, Jean; Pikridas, Michael; Lelieveld, Jos; Crowley, John N.

Shipborne measurements of nitryl chloride (inline-formulaClNO2), hydrogen chloride (HCl) and sulfur dioxide (inline-formulaSO2) were made during the AQABA (Air Quality and climate change in the Arabian BAsin) ship campaign in summer 2017. The dataset includes measurements over the Mediterranean Sea, the Suez Canal, the Red Sea, the Gulf of Aden, the Arabian Sea, the Gulf of Oman, and the Arabian Gulf (also known as Persian Gulf) with observed inline-formulaClNO2 mixing ratios ranging from the limit of detection to inline-formula≈600 pptv. We examined the regional variability in the generation of inline-formulaClNO2 via the uptake of dinitrogen pentoxide (inline-formulaN2O5) to Cl-containing aerosol and its importance for Cl atom generation in a marine boundary layer under the (variable) influence of emissions from shipping and the oil industry. The yield of inline-formulaClNO2 formation per inline-formulaNO3 radical generated was generally low (median of inline-formula≈1 %–5 % depending on the region), mainly as a result of gas-phase loss of inline-formulaNO3 dominating over heterogeneous loss of inline-formulaN2O5, the latter being disfavoured by the high temperatures found throughout the campaign. The contributions of inline-formulaClNO2 photolysis and OH-induced HCl oxidation to Cl-radical formation were derived and their relative contributions over the diel cycle compared. The results indicate that over the northern Red Sea, the Gulf of Suez, and the Gulf of Oman the formation of Cl atoms will enhance the oxidation rates of some volatile organic compounds (VOCs), especially in the early morning.



Eger, Philipp G. / Friedrich, Nils / Schuladen, Jan / et al: Shipborne measurements of ClNO2 in the Mediterranean Sea and around the Arabian Peninsula during summer. 2019. Copernicus Publications.


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