Acidity-driven gas-particle partitioning of nitrate regulates its transport to Arctic through the industrial era

Anthropogenic NO_x emissions have altered the biogeochemical nitrogen cycle since the Industrial Revolution, yet Arctic ice core nitrate (NO₃⁻) records are inconsistent with post-1970s NO_x emission reductions. Here we show a NO₃⁻ deposition history covering 1800–2020 using an ice core from the southeastern Greenland dome with high snow accumulation. The ice core NO₃⁻ concentrations are particularly disconnected from NO_x source regions during the peak pollution period and post-1990s. A global chemical transport model reproduced these discordances between total NO₃⁻ and NO_x emissions by altering gaseous HNO₃ and particulate NO₃⁻ (p-NO₃⁻) ratios and subsequently NO₃⁻ lifetime. This result and correlations with acidity parameters recorded in the ice core, suggest that acidity-driven gas-particle partitioning of NO₃⁻ regulates its transport to Arctic regions alongside changes in NO_x emissions. In the future, despite NO_x reductions, the increase in proportion of p-NO₃⁻ with longer atmospheric lifetime becomes crucial to control the Arctic NO₃⁻ burden.