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

Anthropogenic NOx emissions have altered the biogeochemical nitrogen cycle since the Industrial Revolution, yet Arctic ice core nitrate (NO3−) records are inconsistent with post-1970s NOx 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 NOx source regions during the peak pollution period and post-1990s. A global chemical transport model reproduced these discordances between total NO3− and NOx 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 NOx emissions. In the future, despite NOx reductions, the increase in proportion of p-NO3− with longer atmospheric lifetime becomes crucial to control the Arctic NO3− burden.