Abstract View
A New Method to Quantify Particulate Sodium and Potassium Salts (Sulfate, Nitrate, and Chloride) by Thermal Desorption Aerosol Mass Spectrometry
YUYA KOBAYASHI, Nobuyuki Takegawa, Tokyo Metropolitan University
Abstract Number: 323
Working Group: Instrumentation and Methods
Abstract
Aerosol particles emitted from sea spray and biomass burning have significant contributions to the global budget of aerosols. The reaction of sea salt (or biomass burning) particles with sulfuric acid (H2SO4) and nitric acid (HNO3) leads to the displacement of chloride relative to sodium (or potassium). We have recently developed a new particle mass spectrometer to quantify non-refractory and refractory sulfate aerosols (referred to as the refractory aerosol thermal desorption mass spectrometer: rTDMS). The combination of a graphite particle collector and a carbon dioxide laser enables high desorption temperature (up to 1200 K). Ion signals originating from evolved gas molecules are detected by a quadrupole mass spectrometer. Here we propose a new method to quantify the mass concentrations of sodium chloride (NaCl: SC), sodium sulfate (Na2SO4: SS), sodium nitrate (NaNO3: SN), potassium chloride (KCl: PC), potassium sulfate (K2SO4: PS), and potassium nitrate (KNO3: PN) particles by using the rTDMS. Laboratory experiments were performed to test the sensitivities of the rTDMS to various types of particles. We measured ion signals originating from single-component particles for each compound, and found a good linearity (r2 > 0.8) between the major ion signals and mass loadings. We also measured ion signals originating from internally mixed SC/SS/SN (or PC/PS/PN) particles, and found that the temporal profiles of the ion signals at m/z 23 (or 39) were characterized by three sequential peaks associated with the evolution of the desorption temperature. We tested potential interferences in the quantification of sea salt particles under real-world conditions by artificially generating “modified” sea salt particles from the mixture of diluted seawater and SS/SN solution. Based on these experimental results, the applicability of the rTDMS to ambient measurements of sea salt and biomass burning particles is discussed.