Direct Observation of Heterogeneous Chemistry in the Atmosphere

Abstract

The heterogeneous replacement of chloride by nitrate in individual sea-salt particles was monitored continuously over time in the troposphere with the use of aerosol time-of-flight mass spectrometry. Modeling calculations show that the observed chloride displacement process is consistent with a heterogeneous chemical reaction between sea-salt particles and gas-phase nitric acid, leading to sodium nitrate production in the particle phase accompanied by liberation of gaseous HCl from the particles. Such single-particle measurements, combined with a single-particle model, make it possible to monitor and explain heterogeneous gas/particle chemistry as it occurs in the atmosphere.

Characteristics of individual particles in the atmosphere of Guangzhou by single particle mass spectrometry

“…Differently, NaK-EC type shows the carbon ion clusters mainly in the negative mass spectra, combined with dominant peaks from 23 [Na] ) are present in mass spectra of Na-rich, indicating transport and evolution of sea salt particles (Gaston et al, 2011. The presence of nitrate in Na-rich particles implies the replacement of chloride by nitrate during long-range transport (Gard et al, 1998;Zhao and Gao, 2008). Fe-rich type is identified by strong peaks from iron at m/z 54, 56 and 57, according to their isotopic components.…”

Mixing state of biomass burning particles by single particle aerosol mass spectrometer in the urban area of PRD, China

“…Single particle mass spectrometer, such as aerosol time-of-flight mass spectrometer (ATOFMS), has been extensively used to measure the aerodynamic size and chemical composition of individual aerosol particles (Gard et al, 1997(Gard et al, , 1998Guazzotti et al, 2001;Liu et al, 2003;Toner et al, 2006;Shields et al, 2008;Spencer et al, 2008;Pratt and Prather, 2009). It has been proved to be a powerful tool for analyzing the mixing state and formation mechanisms of aerosols in single particle levels (Gaston et al, 2010;Angelino et al, 2001;Moffet et al, 2004;Freney et al, 2006;Denkenberger et al, 2007;Moffet and Prather, 2009;Wang et al, 2009a;Yang et al, 2009).…”

Continuous measurements of size‐resolved particle chemistry during INDOEX‐Intensive Field Phase 99

“…The presence of nss sulfates can result from heterogeneous oxidation reactions of SO• with sea-salt particles, condensation of sulfuric acid or organic sulfates (such as MSA) onto the particles, and/or cloud processing [Sievering et al, 1991[Sievering et al, , 1992 Some of the detected reacted/aged sea-salt particles show a peak at m/z 108 in their positive ion mass spectra that can be assigned to Na2NO3 +. The presence of this peak serves an indicator of the reaction of NOx species leading to formation of sodium nitrate with displacement of chlorine from the sea-salt particles [Gard et al, 1998]. Compared with data obtained in southern California, NOx heterogeneous reactions on sea-salt particles, tracked by monitoring the relative intensities of the ion peaks at m/z 81, Na2C1 +, and 108, Na2NO3 + [Gard et al, 1998], occurred to a lesser extent during 1NDOEX.…”

“…The presence of this peak serves an indicator of the reaction of NOx species leading to formation of sodium nitrate with displacement of chlorine from the sea-salt particles [Gard et al, 1998]. Compared with data obtained in southern California, NOx heterogeneous reactions on sea-salt particles, tracked by monitoring the relative intensities of the ion peaks at m/z 81, Na2C1 +, and 108, Na2NO3 + [Gard et al, 1998], occurred to a lesser extent during 1NDOEX. Also, some of the sea-salt particles show in their mass spectra peaks that allow for identification of organic matter.…”