Development of an analytical methodology for obtaining quantitative mass concentrations from LAAP-ToF-MS measurements

Overview & Synopsis

Laser ablation aerosol particle-time of flight mass spectrometer (LAAP-ToF-MS) measures the size number of particles, and chemical composition of individual particles in real-time. LAAP-ToF-MS measurements of chemical composition are difficult to quantify, mostly because the instrument sensitivities to various chemical species in the multicomponent atmospheric aerosol particles are unknown. In this study, we investigate a field-based approach for quantitative measurements of ammonium, nitrate, sulfate, OC, and EC, in size-segregated atmospheric aerosols, by LAAP-ToF-MS using concurrent measurements from high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), and multi-angle absorption photometer (MAAP). An optical particle counter (OPC) and a high-resolution nanoparticle sizer (scanning mob ility particle sizer, or SMPS), were used to measure the particle size distributions of the particles in order to correct the number concentrations. The intercomparison reveals that the degree of agreement of the mass concentrations of each compound measured with LAAP-ToF-MS and HR-ToF-AMS/MAAP increases in the following order NH4+