On the effect of wind speed on submicron sea salt mass concentrations and source fluxes

Abstract

[1] A High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was evaluated for its ability to quantify submicron sea salt mass concentrations. The evaluation included both laboratory and field studies. Quantification of the sea salt signal in the HR-ToF-AMS was achieved by taking the 23 Na 35 Cl + ion as a surrogate for sea salt and then identifying a calibration scaling factor through a comparison with mono-disperse laboratory generated sea salt aerosol. Ambient sea salt concentrations calculated using this method agreed well with those obtained by ion chromatography of filter samples, following a 1:1 regression slope and a correlation coefficient R = 0.93. A key advantage of this AMS-based method is that it allows for high time resolution measurements of sea salt (5 min) along with the speciation of other chemical compounds, including primary organics contributing to sea spray. The high-time resolution sea salt measurement capability enabled the quantification of sea salt mass in both increasing and decreasing wind speed regimes up to 26 m s À1 . A mass flux source function was also derived and found to have a power law wind speed dependency with an exponent of 3.1 for increasing winds and 2.3 for decreasing winds. Comparison of the mass flux relationship in this study suggests that previous schemes based on the Monahan whitecap-wind speed approach significantly over-estimate the submicron mass flux. Both the whitecap-wind speed component and the differential whitecap-aerosol productivity component of the source flux function contribute toward the over-estimation.

Aerosol mass spectrometry: particle–vaporizer interactions and their consequences for the measurements

“…Water also contributes to the AMS mass spectra; however it is typically not quantified due to multiple interferences. Nevertheless, several other species or elements have been observed in measurements performed, e.g., in marine air (Zorn et al, 2008, Ovadnevaite et al, 2012, Schmale et al, 2013 or in urban air (Salcedo et al, 2010(Salcedo et al, , 2012, or in measurements of emissions from pyrotechnical devices (Drewnick et al, 2006;Faber et al, 2013). From our experience, as an empirical proxy, a substance can typically be measured in the AMS with some efficiency if its melting point is not far (< 200 • C) above the vaporizer temperature.…”

“…However, under certain conditions, e.g., when measuring close to anthropogenic sources or in the marine environment, the limitations of these assumptions are sometimes reached and the standard analysis could result in misinterpretation of the mass spectra. Nevertheless, under such conditions additional information extending beyond the standard AMS species can often be retrieved from the mass spectra: in measurements of the marine aerosol, NaCl, which is generally claimed to be refractory and therefore not measurable with the AMS, was unambiguously measured with this instrument (Zorn et al, 2008;Ovadnevaite et al, 2012;Schmale et al, 2013). In the measurements of fireworks (Drewnick et al, 2006) and hand flare emissions (Faber et al, 2013) several metal-containing species (e.g., with Fe, Mg, K, Cu, Li, Na) and their fragments have been identified, albeit not quantified in the mass spectra.…”

“…In order to extract quantitative information on such species, different approaches have been applied. These include the determination of relative ionization efficiencies (RIEs), either by comparison with external measurements (Drewnick et al, 2006) or by laboratory experiments (Ovadnevaite et al, 2012), or modeling of the mass concentration of a semi-refractory species from the beam-open and beam-closed signals of the mass spectra (Salcedo et al, 2010).…”

Estimating N&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt; uptake coefficients using ambient measurements of NO&lt;sub&gt;3&lt;/sub&gt;, N&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;5&lt;/sub&gt;, ClNO&lt;sub&gt;2&lt;/sub&gt; and particle-phase nitrate

“…As the AMS detects marine chloride (i.e. refractory chloride) with 1 to 2 orders of magnitude lower sensitivity than non-refractory chloride (Zorn et al, 2008;Ovadnevaite et al, 2012;Schmale et al, 2013;Drewnick et al, 2015) it is reasonable to assume that the majority of the Cl − reported by the AMS is due to NH 4 Cl arising from uptake of gas-phase HCl which may have marine or anthropogenic origin. The AMS was calibrated using the measurement of standard ammonium nitrate particles of known particle size via a differential mobility analyser.…”

What do we learn from long-term cloud condensation nuclei number concentration, particle number size distribution, and chemical composition measurements at regionally representative observatories?

“…Table 1 lists which 30 species are available at each station; missing species mean that their concentrations were below detection limit. At Mace Head, the sea salt content of the submicrometer aerosol is given in addition based on a specific method introduced by Ovadnevaite et al (2012).…”