Quantifying the Chemical Composition and Mass Concentration of Nanoplastic Particles in the Atmosphere Using Real-time Mass Spectrometry

Sining Niu, Sahir Gagan, Alana Dodero, Zezhen Cheng, Ruizhe Liu, Xingmao Ma, Qi Ying, Manjula Canagaratna, YUE ZHANG, Texas A&M University

     Abstract Number: 368
     Working Group: Nanoparticles and Materials Synthesis

Abstract
Nanoplastics have been shown to not only have adverse implications on human health and the ecosystem, but also contribute to climate forcing. Despite being increasingly important, there is no real-time detection of atmospheric nanoplastic particles (NPP) while previous offline methods often require days to weeks of collection.

Herein, we provide the first study to quantify real-time nanoplastics concentrations in the atmosphere and their chemical reaction process. 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 plastics produced. A calibration curve is established and tracer ions, including m/z 74 and 104, are shown to be unique to PS particles.

Ambient particles are also collected and analyzed by a constrained PMF (multilinear engine, ME-2) method to determine the temporal distribution of microplastic particles. A distinct factor that is highly correlated to the pure PS profile is separated. The mass concentration of PS nanoplastic particles is estimated to be 10-50 ng m^-3 with a detection limit of 3 ng m^-3 during our sampling periods in Texas.

In addition, the aging of PS particles reacting with hydroxyl radicals (OH·), ozone, and UV light are characterized using a Potential Aersosol Mass (PAM) reactor. The pseudo first order rate constant of PS particles against OH· radicals is calculated to be 1.374×10^-13 cm³ molecule^-1 s^-1 while the ozonolysis and photolysis rates were negligible. The half-life time of microplastic in the atmosphere is estimated to be less than 84 days, significantly shorter than their marine lifetime. Microscopic measurements also demonstrate that the NPP become more hygroscopic after aging, suggesting changes of their climate properties.

The above results may bridge important gaps in understanding the long range transportation abilities, environmental persistence, health implications, and potential climate forcing of the NPP.