ENV-01 Halogens in the marine environment
Comprehensive investigation on marine-derived halocarbons over the coastal and open ocean of the western Pacific sources, emissions, and environmental effects
Zhen He* , Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China
Shan-Shan Liu, Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China
Jie-Ni, Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China
Gui-Peng Yang, Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China

Oceanic emissions and concentrations of the halocarbons CH3Cl, CH3Br, CH3I, C2H5I, and C2Cl4 were studied in the East China Sea (ECS), South China Sea (SCS), and western Pacific during 2017–2020. Atmospheric concentrations of CH3Cl and CH3Br increased by 6.9–26.8% in areas affected by air masses from China, Korea, and Philippines, indicating that terrestrial atmospheric transport from these regions was a significant source of these halocarbons. Whereas in the western Pacific, CH3Cl and CH3Br were most abundant in high-productivity areas (Kuroshio-Oyashio Extension), and coincided with high values of Chl-a, suggesting that biological production was an important source of these gases in the open sea. CH3I and C2H5I showed evidence of photochemical production, with particularly high concentrations observed in 20–30°N of the oligotrophic subtropical western Pacific. CH3Cl (CH3Br) emissions were estimated to be 4.95 (0.07) Gg/y for the marginal seas (ECS and SCS) and 5.75 (0.10) Gg/y for the western Pacific, accounting for 0.72% (0.55%) and 0.83% (0.78%) of global oceanic emissions, respectively. This highlighted the importance of western Pacific emissions as a “missing source” in halocarbon budgets.