Oceanic emissions of methyl halides and effect of nutrients concentration on their production: A case of the western Pacific Ocean (2°N to 24°N)

Shan-Shan Liu; Gui-Peng Yang; Zhen He; Xu-Xu Gao; Feng Xu

doi:10.1016/j.scitotenv.2020.144488

Oceanic emissions of methyl halides and effect of nutrients concentration on their production: A case of the western Pacific Ocean (2°N to 24°N)

Sci Total Environ. 2021 May 15:769:144488. doi: 10.1016/j.scitotenv.2020.144488. Epub 2021 Jan 6.

Authors

Shan-Shan Liu¹, Gui-Peng Yang², Zhen He³, Xu-Xu Gao¹, Feng Xu¹

Affiliations

¹ Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China.
² Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China; Institute of Marine Chemistry, Ocean University of China, Qingdao 266100, China.
³ Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China. Electronic address: zhenhe@ouc.edu.cn.

PMID: 33485203
DOI: 10.1016/j.scitotenv.2020.144488

Abstract

Methyl halides are important greenhouse gases responsible for the majority of the ozone layer depletion. This study investigated atmospheric and seawater methyl halides (CH₃Cl, CH₃Br, and CH₃I) in the western Pacific Ocean between 2°N and 24°N. Increases in methyl halides in the atmosphere were likely to have originated from Southeast Asian regions. Elevated CH₃I concentrations in seawater were mainly produced photochemically from dissolved organic carbon. Maximum methyl halide and chlorophyll a levels in the upper water column (0-200 m) were linked to biological activity and downwelling or upwelling caused by cold and warm eddies. Ship-based incubation experiments showed that nutrient supplementation promoted methyl halide emissions. The elevated methyl halide production was associated with increases in phytoplankton such as diatoms. The mean fluxes of CH₃Cl, CH₃Br, and CH₃I in study area of during the cruise were 82.91, 4.70, and 3.50 nmol m^-2 d^-1, respectively. The estimated emissions of CH₃Cl, CH₃Br, and CH₃I in the western Pacific Ocean accounted for 0.67%, 0.79% and 0.09% of global oceanic emissions, respectively, indicating that the open sea contribute insignificantly to the global oceanic emissions of these gases.

Keywords: Marine atmosphere; Methyl halides; Ship-based incubation experiments; Western Pacific Ocean.