Quantifying the Chemical Composition and Mass Loading of Microplastic Submicron Particles (MPPs) in the Atmosphere using Real-time Aerosol Mass Spectrometry
SINING NIU, Ruizhe Liu, Sahir Gagan, Nicolas Aliaga Buchenau, Sarah Brooks, Jason Surratt, Xingmao Ma, Manjula Canagaratna, Yue Zhang,
Texas A&M University Abstract Number: 366
Working Group: Aerosol Chemistry
AbstractThe prevalence of microplastics detected in the ecosystem is an emerging problem worldwide. Microplastics have been shown to not only have adverse implications on human health, but also contribute to climate forcing in the aerosol form by efficiently scattering shortwave radiation and absorbing longwave radiation. Despite their increasing importance, a real-time detection method for atmospheric microplastic particles (MPPs) has not yet been established. Instead, analyzing atmospheric MPPs often involves complicated sample collection and preparation procedures, followed by offline analysis methods.
Herein, to our knowledge we provide the first real-time measurement study to quantify atmospheric MPP concentrations. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) is employed to detect submicron polystyrene (PS) particles, one of the most abundant microplastics produced. A calibration curve for determining the mass concentration of atmospheric MPPs is established by sampling monodisperse PS particles with the AMS, and the relative ionization efficiency is 2.0. Several tracer ions, including those at mass-to-charge ratios (
m/z) 78 and 104, are shown to be unique to PS-containing particles. Positive matrix factorization (PMF) is applied to AMS data collected from externally-mixed PS particles with laboratory-generated inorganic and secondary organic aerosols, to mimic complex aerosol mixtures. The MPPs PMF factor is successfully derived and highly corrected with the pure PS mass spectrum (R
2=0.93).
Ambient particles are also collected and analyzed by the constrained PMF (multilinear engine, ME-2) to determine the temporal distribution of MPPs. A distinct factor that is highly correlated to the pure PS profile is separated. The average PS mass concentration is estimated to be 17 ng/m
3 with a detection limit of 3 ng/m
3 during a 48-hour sampling period. The methodology and results of our study can improve the understanding of the atmospheric transport, life cycle and climate effect of MPPs (an emerging pollutant of rising concern).