Arctic observations of Hydroperoxymethyl Thioformate (HPMTF) – seasonal behavior and relationship to other oxidation products from Dimethyl Sulfide at the Zeppelin Observatory, Svalbard
Abstract. Dimethyl sulfide (DMS), a gas produced by phytoplankton, is the largest source of atmospheric sulfur over marine areas. DMS undergoes oxidation in the atmosphere to form a range of oxidation products, out of which methanesulfonic acid (MSA) and sulfuric acid (SA) are well-known for participating in the formation and growth of atmospheric aerosol particles. Recently, a new oxidation product of DMS, hydroperoxymethyl thioformate (HPMTF) was discovered and later also measured in the atmosphere. Little is still known about the fate of this compound and its potential to partition to the particle phase. In this study, we present a full year (2020) of concurrent gas- and particle-phase observations of HPMTF, MSA, SA and other DMS oxidation products at the Zeppelin Observatory (Ny-Ålesund, Svalbard) located in the Arctic. This is the first time HPMTF has been measured in Svalbard and attempted to be observed in atmospheric particles. The results show that gas-phase HPMTF concentrations largely follow the same pattern as MSA during the sunlit months (April–September), indicating production of HPMTF around Svalbard. However, HPMTF was not observed in significant amounts in the particle phase, despite high gas-phase levels. Particulate MSA and SA were observed during the sunlit months, although the highest median levels of particulate SA were measured in February, coinciding with the highest gaseous SA levels with assumed anthropogenic origin. We further show that gas- and particle-phase MSA and SA are coupled in May–July, whereas HPMTF lies outside of this correlation due to the low particulate concentrations. These results provide more information about the relationship between HPMTF and other DMS oxidation products in a part of the world where these have not been explored yet, and about HPMTF’s ability to contribute to particle growth and cloud formation.
Karolina Siegel et al.
Status: open (until 04 Apr 2023)
- RC1: 'Comment on egusphere-2023-146', Anonymous Referee #1, 09 Mar 2023 reply
- RC2: 'Comment on egusphere-2023-146', Anonymous Referee #2, 17 Mar 2023 reply
Karolina Siegel et al.
Karolina Siegel et al.
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Siegel et al. presented gas-phase and particle-phase measurements of SA, MSA and HPMTF during the full year of 2020 at the Zeppelin Observatory, Ny-Ålesund, Svalbard. They report high gas-phase concentrations of HPMTF between April and September when DMS emissions are high, but observe no significant concentration of HPMTF in the particle-phase. The paper is well written and provides an important insight into the role of HPMTF in the atmosphere. I recommend that the paper be published after addressing the comments bellow.
Page 1 - line 2: "methanesulfonic acid (MSA) and sulfuric acid (SA) are well-known for participating in the formation and growth of atmospheric aerosol particles". While it is well known that SA contributes to new particle formation, I would not say that MSA is well-known to do so. Recent studies have found it plausible that MSA contributes to NPF, but it has not been definitely established.
Page 2 - line 29: "Up to 42% of global natural sulfur emissions can be traced back to DMS". This is a low estimate, and other studies have reported that DMS may comprise more than 50% of the global natural sulfur emission. Therefore, I would not use the phrasing, 'up tp 42%'.
Figure 1: I find the schematic for SO2 and SO3 production a bit confusing. While SO2 produces SO3 which in turn produces SA, SO3 is also formed directly from CH3SO3 (which is the dominant pathway leading to SO3 and thus SA production from DMS). Consider making an arrow that branches into both SO2 and SO3 production to indicate that they are produced from two separate pathways.
Page 15 - line 296: "the summer months are known for higher particle number concentrations due to new particle formation (Tunved et al., 2013), where condensation of SA from DMS oxidation and formation of MSA are the main drivers". Rephrase this statement. It is not the condensation of SA and MSA that drives the increase in PN. It is the new particle formation from SA (and maybe also MSA) that causes an increase in PN.
Figure 4: Why would you show a combined R2 value for SA and MSA, and not just report R2 for both species?
Figure 2: Consider using (a), (b), (c), (d) instead of upper left, upper right, etc.
Page 10 - line 218: "to be able to produce DMS". Write, "in order to produce DMS".
Figure 4: No need to have the same y-axis ticks all three plots. Just keep the ones on the left plot.
Figure 4: What is the unit for the gas-phase and particle-phase measurements?
Page 19 - line 381: "Although it seems not likely". Write, "Although it seems unlikely".
Page 21 - Line 421: "and the almost unknown HPMTF one". Write, "and the almost unknown one of HPMTF".