Kinetics of the formation and decomposition of hydroxymethanesulfonate

Abstract

The kinetics of the formation and decomposition of hydroxymethanesulfonate (HMSA) have been examined at pH 4 and 5. The second‐order rate constant for the formation of HMSA at 25°C was measured to be 1.94 ± 0.11 and 12.60 ± 1.04 mol−1 s−1 at pH values of 4 and 5, respectively. The rate constant of HMSA decomposition to form formaldehyde (HCHO) and aqueous sulfur dioxide S(IV) at pH 4 and 5 was 4.8 ± 0.4 × 10−7 and 3.5 ± 0.2 × 10−6 s−1, respectively. In addition, no reaction between hydrogen peroxide (H2O2) and HMSA was observed when a tenfold molar excess of H2O2 was present at pH values of 4 and 5.

Direct observation of aqueous secondary organic aerosol from biomass-burning emissions

“…HMS is formed from the complexation of sulfite and bisulfite with aqueous formaldehyde (25)(26)(27)(28). During both campaigns, HMS was detected by the HR-ToF-AMS and was also measured by proton NMR (H-NMR) (Methods and Supporting Information, 2.…”

Real-time secondary aerosol formation during a fog event in London

“…3c) confirm this finding, showing an increase of particles at about 0.8-1.0 µm in association with the detection of the ATOFMS HMS particle type. The formation and stability of HMS has been shown to be highly dependent on the pH of the particle or droplet, as well as the concentrations of other chemical species (Kok et al, 1986;Lagrange et al, 1999). HMS is exclusively formed in the aqueous phase, so its presence in particles is a valuable tracer for processing by aqueous phase chemistry.…”

Sulfur dioxide in rain clouds: Gas-liquid scavenging efficiencies and wet deposition rates in the presence of formaldehyde

“…Although a rise in temperature would cause a small fraction of HMS to decompose, the process is slow. The time constant for the decomposition of HMS at pH = 5.6 is 105 sec and it increases further with decreasing pH (Deister et al, 1986;Kok et al, 1986). The transit time for rain drops from cloud base to ground level is much shorter, namely about 10 3 sec (Pruppacher and Klett, 1980).…”

“…The forward rate constant kcf=5.4× 106M-ls-I has been measured by Boyce and Hoffmann (1984) and the reverse rate constant kor may be estimated from the data of Kok et al (1986) and Deister et al (1986) as kcr~4× 103M-Is-l. In the pH range 4-6, the concentration of OH-is 10-8-10 -I° .…”

“…The reaction mechanism thus involves the following steps The ion equilibria are rapidly established, so that the rate of HMS formation is essentially determined by the rates of steps (a) and (c). For high concentrations of S(IV), the dissociation of CH2(OH)2 is the rate-limiting reaction, whereas for S(IV)~< 10 BM and pH ~< 6, it ceases to be rate-limiting and the rate of HMS formation is then determined by step (c) (Olson and Hoffmann, 1986;Kok et al, 1986). This is the condition applicable to clouds.…”