Filterable and Condensable Particulate Nitrate Emissions from Plumes over North China

Particulate nitrate (NO₃⁻) over North China is commonly treated as a purely secondary product in chemical transport models (CTMs), yet persistent low bias suggests a missing source. Here, we quantified plume primary NO₃⁻ (P-NO₃⁻, filterable + condensable) over North China by integrating a sector-specific emissions framework, oxygen-isotope constraints, and WRF-CMAQ sensitivity simulations for January and August 2019. We compiled a China-specific source-profile database for filterable P-NO₃⁻ and constructed a comprehensive condensable particulate matter (CPM) inventory across 9 anthropogenic sectors. The plume P-NO₃⁻ emissions were dominated by the condensable fraction (91.5%) and industrial and power sources (92.5%). Adding CPM in CMAQ increased near-surface pNO₃⁻ by 0.98 ± 0.48 μg m⁻³ (10.1 ± 4.8%) in the summer and 0.99 ± 0.45 μg m⁻³ (4.6 ± 1.7%) in the winter, improving model performance with the response primarily expressed as enhanced emissions rather than aerosol chemistry. Similarly, a Bayesian δ¹⁸O model using a low-δ¹⁸O plume end member (20.2 ± 7.8‰) yields plume P-NO₃⁻ contributions of 13.1 ± 4.0% (summer) and 4.5 ± 2.0% (winter) and showed that omitting this end member systematically overestimated NO₃⁻ to the ·OH+NO₂ pathway. These findings highlighted CPM-driven plume P-NO₃⁻ as a missing source that should be explicitly represented in inventories, CTMs, and NO₃⁻ mitigation strategies.