Photothermal conditions and upwelling enhance very short-lived brominated halocarbons emissions in the western tropical Pacific Ocean

Jie Ni; Shan-Shan Liu; Gao-Bin Xu; Xuan Ji; Zhen He; Gui-Peng Yang

doi:10.1016/j.scitotenv.2024.173035

Photothermal conditions and upwelling enhance very short-lived brominated halocarbons emissions in the western tropical Pacific Ocean

Sci Total Environ. 2024 Jul 1:932:173035. doi: 10.1016/j.scitotenv.2024.173035. Epub 2024 May 7.

Authors

Jie Ni¹, Shan-Shan Liu¹, Gao-Bin Xu¹, Xuan Ji¹, Zhen He², Gui-Peng Yang³

Affiliations

¹ 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.
² 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; Laboratory for Marine Ecology and Environmental Science, Qingdao Marine Science and Technology Center, Qingdao 266237, China. Electronic address: zhenhe@ouc.edu.cn.
³ 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; Laboratory for Marine Ecology and Environmental Science, Qingdao Marine Science and Technology Center, Qingdao 266237, China; Institute of Marine Chemistry, Ocean University of China, Qingdao 266100, China. Electronic address: gpyang@mail.ouc.edu.cn.

PMID: 38719031
DOI: 10.1016/j.scitotenv.2024.173035

Abstract

Sea-to-air emissions of very short-lived brominated halocarbons (VSLBrHs) are known to contribute to 30 % of stratospheric and tropospheric ozone depletion. However, empirical data on their occurrence in open ocean are scarce, which makes it difficult to estimate the significant contribution of open ocean releases to the global budget of halocarbons. This study was conducted in 2022 to explore the spatial variations of VSLBrHs and their controlling factors in the western tropical Pacific Ocean (WTPO). The findings highlighted that high biological productivity and the resulting dissolved organic matter (DOM) as well as upwelling dynamics significantly influenced the distribution and production of VSLBrHs in seawater, with atmospheric levels primarily governed by oceanic emissions. Based on the simultaneous observation of seawater and atmospheric concentrations, the mean sea-to-air fluxes of CH₂Br₂, CHBr₃, CHBrCl₂, and CHBr₂Cl were estimated to be 1.01, 6.65, 9.31, and 7.25 nmol m^-2 d^-1, respectively. Sea-to-air fluxes of these gases in the upwelling regions were 9.0, 4.6, 2.9, and 6.8 times those in the non-upwelling regions, respectively. Additionally, in-situ incubation experiments revealed that the enzymatic mediated biosynthesis pathways of VSLBrHs were enhanced under temperature and light-induced stress and in waters rich in humus-like substances. Therefore, we tentatively concluded that abundant photothermal conditions and the existence of upwelling in the WTPO made it a potential hotspot for the emission of VSLBrHs. This study offers critical insights into the environmental dynamics of VSLBrHs emissions and underscores the importance of regional oceanic conditions in influencing atmospheric greenhouse gas compositions.

Keywords: Distribution; Enzyme-mediated production; Sea-to-air fluxes; Very short-lived brominated halocarbons; Western tropical Pacific Ocean.