Study of metal aerosol systems as a sink for atmospheric SO2

Abstract

The chemical removal of SO 2 in the presence of different aerosol systems has been investigated in laboratory experiments using a dynamic flow reactor. The aerosols consisted of wetted particles containing one of the following substances: MnC12, Mn(NO3)2, MnSO4, CuCI2, Cu(NO3)2, CuSO4, FeC13, NaCI. The SO2 removal rate R was measured as a function of the SO2 gas phase concentration (SO 2)g, the spatial metal concentration CMe , and the relative humidity rH in the reactor. A first-order dependence with regard to (SO 2)g was observed for each type of aerosol. For the Mn(II) and Cu(II) aerosols R was found to be a non-linear function of CMe except for MnSO a and Cu(NO 3)2 particles. The removal rate showed a significant increase with the relative humidity particularly when rH was close to the deliquescence point of the wetted particles. Among the Mn(II) and Cu(II) aerosols investigated Mn(NO3) 2 was found to be most efficient for the chemical removal of SO 2 at atmospheric background conditions, especially in haze and fog droplets. The results further indicate that the catalytic oxidation of S(IV) in such aerosol systems may be as efficient as its oxidation by H20 2 in cloud water.

Tropospheric volcanic aerosol

“…Allen et al, 2002]. The potential mech anism is as yet unclear, but it has been suggested that nucle ation on ultrafine metal chlorides may play a role, with the metallic cations enhancing the reaction rate [Berresheim and Jaeschke, 1986]. Once formed, this sulfuric acid may modify trace metal speciation by revolatilisation of HC1 and the for mation of metal sulfates: 2XC1 (s) + H 2 S0 4 (1) <=> X 2 S0 4 (s/aq) + 2HC1 (g) Etna volcano frequently shows distinctive differences between the emissions from lava flows, degassed at low pressures, and the summit plumes [e.g.…”

Missing SO&lt;sub&gt;2&lt;/sub&gt; oxidant in the coastal atmosphere? – observations from high-resolution measurements of OH and atmospheric sulfur compounds

“…Heterogeneous oxidation (on the surface of aerosol particles and in cloud and fog droplets) is dominated by reactions with either dissolved ozone, hydrogen peroxide, or molecular oxygen, the latter pathway being catalyzed by transition metal ions (Harris et al, 2013;Berresheim and Jaeschke, 1986). However, recent studies have revived an interest in the formation and fate of atmospheric Criegee intermediates (radical species produced from reactions of ozone with alkenes; Calvert et al, 2000;Criegee, 1975), which to this day have eluded direct measurements in the atmosphere since Cox and Penkett (1971) first suggested their potentially important role.…”

On the Source of the Submicrometer Droplet Mode of Urban and Regional Aerosols

“…Martin and Hill (1987) reported an inhibition effect of ionic strength on the rate of the manganese catalyzed oxidation of sulfur; this inhibition effect may be important for the aerosol-phase chemistry due to its high-ionic-strength characteristics. On the other hand, Berresheim and Jaeschke (1986) studied the removal of SO, directly in the presence of different aerosol systems. By using a metal concentration of 55 ng m-3 and RH = 94%, they obtained an SO, removal rate of 2-5% h e ' for Mn(NO,),, 1.5% h-' and 0.09% h -' for MnCl, and MnSO,, respectively, at pH's as low as 1.5.…”