Free tropospheric halogen oxidation drives mercury deposition in the Asia Pacific region
Abstract
Asian outflow represents 50% of global anthropogenic mercury emissions, but the atmospheric oxidation pathways controlling its deposition to the adjacent Pacific Ocean remain poorly constrained. Using multi-year snow and atmospheric mercury isotope measurements from Mt. Halla, Jeju Island, Korea, we delineate the mercury sources and oxidation pathways governing deposition to marginal Asia and the western Pacific. Mass-independent fractionation of even-number mercury isotopes (even-MIF; Δ 200 Hg) correlates with both air mass transport distance and trajectory altitude, indicating the importance of free tropospheric mercury photo-oxidation triggering even-MIF. Coupled anomalies between Δ 200 Hg and oxygen isotopes of nitrate (Δ 17 O(NO 3 -)) in snow indicate that reactive bromine, generated from debromination of local sea salt aerosol, sustains oxidative capacity in the free troposphere and drives active mercury deposition to Mt. Halla snow. Isotope mixing models quantify that halogen-mediated free tropospheric mercury oxidation (68%) exceeds near-surface oxidation (32%). Our results provide field-based evidence for a bromine-driven free tropospheric photooxidation mechanism regulating mercury deposition to Asia-Pacific ecosystems.
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BibTeX
@article{lee2026free,
title = {{Free tropospheric halogen oxidation drives mercury deposition in the Asia Pacific region}},
author = {Ju Hyeon Lee and Young-Gwang Kim and Hoin Lee and Seung Hyeon Lim and Joël Savarino and Alfonso Saiz-Lopez and Jeroen E. Sonke and Kitae Kim and Ki-Tae Park and Eunho Jang and Yeongcheol Han and Aryeh Feinberg and Hélène Angot and Ilann Bourgeois and Sae Yun Kwon},
journal = {Communications Earth \& Environment},
year = {2026},
month = oct,
doi = {10.1038/s43247-026-04144-0},
url = {https://www.nature.com/articles/s43247-026-04144-0},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Free tropospheric halogen oxidation drives mercury deposition in the Asia Pacific region
AU - Ju Hyeon Lee
AU - Young-Gwang Kim
AU - Hoin Lee
AU - Seung Hyeon Lim
AU - Joël Savarino
AU - Alfonso Saiz-Lopez
AU - Jeroen E. Sonke
AU - Kitae Kim
AU - Ki-Tae Park
AU - Eunho Jang
AU - Yeongcheol Han
AU - Aryeh Feinberg
AU - Hélène Angot
AU - Ilann Bourgeois
AU - Sae Yun Kwon
PY - 2026
DA - 2026/10/21
JO - Communications Earth & Environment
DO - 10.1038/s43247-026-04144-0
UR - https://www.nature.com/articles/s43247-026-04144-0
AB - Asian outflow represents 50% of global anthropogenic mercury emissions, but the atmospheric oxidation pathways controlling its deposition to the adjacent Pacific Ocean remain poorly constrained. Using multi-year snow and atmospheric mercury isotope measurements from Mt. Halla, Jeju Island, Korea, we delineate the mercury sources and oxidation pathways governing deposition to marginal Asia and the western Pacific. Mass-independent fractionation of even-number mercury isotopes (even-MIF; Δ 200 Hg) correlates with both air mass transport distance and trajectory altitude, indicating the importance of free tropospheric mercury photo-oxidation triggering even-MIF. Coupled anomalies between Δ 200 Hg and oxygen isotopes of nitrate (Δ 17 O(NO 3 -)) in snow indicate that reactive bromine, generated from debromination of local sea salt aerosol, sustains oxidative capacity in the free troposphere and drives active mercury deposition to Mt. Halla snow. Isotope mixing models quantify that halogen-mediated free tropospheric mercury oxidation (68%) exceeds near-surface oxidation (32%). Our results provide field-based evidence for a bromine-driven free tropospheric photooxidation mechanism regulating mercury deposition to Asia-Pacific ecosystems.
SN - 2662-4435
ER -