Sulfuric acid decomposition chemistry above Junge layer in Earth's atmosphere concerning ozone depletion and healing

Montu K Hazra,Prabhash Mahata,Sourav Ghoshal,Biswajit Maiti

doi:10.1038/s42004-019-0178-4

Abstract

Sulfuric acid (H2SO4) is the seed molecule for formation of stratospheric sulfate aerosol layer that assists ozone depletion by activation of halogen species. The impact of increased stratospheric sulfate aerosols due to large volcanic eruptions and possible side effect claimed in the geoengineering scheme of global climate using man-made injected stratospheric sulfate aerosols is ozone depletion. Given that both volcanic eruptions and geoengineering scheme are ultimately connected with increased upper stratospheric concentrations of H2SO4, here we show by theoretical approach that the pressure-independent H2SO4 + O(1D) insertion/addition reactions via barrierless formation of peroxysulfuric acid (H2SO5) or HSO4 + OH radicals or sulfur trioxide (SO3) + hydrogen peroxide (H2O2) molecules are the potential routes towards H2SO4 loss above the stratospheric sulfate aerosol layer, and for the regeneration or transportation of consumed lower-middle stratospheric OH radical in the upper stratosphere at the cost of O(1D)/ozone.

Highlights

Sulfuric acid (H2SO4) is the seed molecule for formation of stratospheric sulfate aerosol layer that assists ozone depletion by activation of halogen species
It is seen from our calculations that the VRC-VTST predicted rate constants are pressure independent in atmospheric pressures (Supplementary Note-3 and Supplementary Tables 13−15) and here, we only focus upon the overall rate constants (k = k1) of Channel-I to III relevant to 35 to 65 km altitude of the Earth's atmosphere (Table 1), as our main aim is to understand the potential impact of H2SO4 + O(1D) reaction in upper stratosphere and lower mesosphere
In the hunt of atmospheric sinks of H2SO4, the present study suggests that the O(1D)−insertion/addition reaction mechanism is competitive with the H2SO4 visible photolysis in the upper stratosphere

Summary

Introduction

Sulfuric acid (H2SO4) is the seed molecule for formation of stratospheric sulfate aerosol layer that assists ozone depletion by activation of halogen species. In the quest for an answer to the question about the decomposition of H2SO4 molecule in the Earth's upper stratosphere, the visible solar radiation (hν) pumping photolysis of H2SO4 vapor (H2SO4 + hν → SO3 + H2O) is the potential mechanism This mechanism has been proposed by Vaida et al.[17] in 2003, and absorption of visible sunlight by the H2SO4 molecule is the prerequisite step for the occurrence of its unimolecular decomposition[17,18,19]. The dominant photo-dissociation mechanism of H2SO4 above 70 km altitude is the absorption of Lyman−α radiation by high energy Rydberg excited states[30] These two mechanisms are two important pathways towards the upper atmospheric loss of H2SO4 molecule. We show that the barrierless fast H2SO4 + O(1D)

Methods

Results

Conclusion