PNNL

Abstract

New particle formation (NPF) substantially affects air pollution and climate change. However, as an NPF hotspot, the mechanisms and impacts of NPF across broad spatial and temporal scales over China remain poorly understood, largely owing to the lack of critical NPF processes in atmospheric models. This study developed a comprehensive model that integrates 12 NPF mechanisms, including recent insights on various iodine–oxoacid-driven pathways and cluster-dynamics-based rate calculations. The updated model reduces model–observation discrepancies from around or over an order of magnitude to within ±30% across different sites and seasons. Simulations revealed that NPF over mainland China is driven primarily by sulfuric acid (H2SO4), dimethylamine (DMA), and iodic acid (HIO3). Importantly, H2SO4–DMA nucleation is not only the dominant mechanism in urban atmospheres, but also a major contributor in agricultural and forested regions. Differently, the HIO3–(H2SO4)–DMA mechanism contributes substantially in southeastern coastal areas, while iodine–oxoacid–H2SO4 pathways dominate in marine regions. High H2SO4 levels are identified as the main driver of eastern China’s NPF hotspots, with temperature governing seasonal variations. Correspondingly, NPF contributes 10%–35% of cloud condensation nuclei (at 0.5% supersaturation) in the lower troposphere. Our models and findings support comprehensive understanding of NPF over China, and are also highly valuable for studying NPF in other regions with diverse emission sources and land cover types, and thereby contributing to accurate assessment of the environmental and climatic effects of aerosols.