Data from: Positive matrix factorization reveals volatility-resolved composition from new particle formation during α-pinene ozonolysis

Atmospheric aerosols influence climate and human health, yet the
mechanisms governing new particle formation (NPF) and early growth remain
incompletely understood, in part because ultrafine particle composition
and volatility are difficult to measure and interpret. Here we combine
size- and temperature-resolved Thermal Desorption Chemical Ionization Mass
Spectrometer measurements with positive matrix factorization (PMF) to
reduce chemical complexity in particles formed during α-pinene ozonolysis
in a continuous-flow chamber. PMF resolves seven factors: six parent
ion-dominated factors spanning semi-volatile to low-volatility behavior
with factor log C* ranging from 2.48 to -3.67, and one decomposition
factor dominated by thermal and ionization fragments. Representative ions
indicate a systematic volatility progression from semi-volatile carboxylic
acids to low-volatility multifunctional acids and diacids. An absorptive
partitioning model using size distribution-derived total particulate mass
shows that low-volatility factors remain effectively in the particle phase
across the experiment, while semi-volatile factors increase their
particle-phase fraction as condensed mass increases. Size-resolved factor
contributions across sampled volume mean diameters 30-130 nm show that
particles below 75 nm are enriched in low-volatility factors, whereas
semi-volatile compounds become important only after substantial growth to
~75-100 nm, consistent with reduced Kelvin limitations at larger sizes.
This framework provides volatility- and size-resolved constraints on
nanoparticle chemical evolution, advancing NPF understanding by
identifying which volatility regimes control growth as particles
transition from nucleation to accumulation of condensable mass.