Five-S-isotope evidence of two distinct mass-independent sulfur isotope effects and implications for the modern and Archean atmospheres

Abstract

SignificanceAnomalous sulfur isotopic compositions preserved in sedimentary rocks older than ∼2.5 billion years have been widely interpreted as the products of UV photolysis of sulfur dioxide in an anoxic atmosphere and used to track the history of primitive Earth and evolution of early life. In this study, we present strong observational evidence that there is an additional process that produces similar anomalous sulfur isotope signatures. This previously unknown origin not only offers a tool for quantifying the present-day atmospheric sulfur budget and evaluating its influences on climate and public health but also implies that anomalous sulfur isotopic compositions in some of the oldest rocks on Earth might have been produced in a way different from that previously thought.

Use of Isotope Effects To Understand the Present and Past of the Atmosphere and Climate and Track the Origin of Life

“…In this case,t he exit channels such as aerosol formation and deposition become important. Am ost recent study revealed complex radical chain reactions of hydrocarbon in the inner zone of combustion flame before exposure to oxygen or OH radical in ambient air, [184] and therefore sulfur recombination reactions probably also occur in the combustion flame before oxidizing to SO 2 or sulfate.B ased on the observational evidence of combustionassociated D 36 S, [176] symmetric effect of sulfur-bearing species experimentally determined by Bains-Sahota and Thiemens, [129] and new theoretical investigation by Babikov, [181] Lin et al [176] proposed that symmetry-relevant and radical driven recombination reactions in combustion (e.g., SH + S! Thepossible mass independent isotope effect in the formation of S 2 ,t he starting molecule in as eries of sulfur recombination reactions,i sf urther investigated by calculating energy transfer mechanism and scattering resonance property.…”

“…The 35 S nuclide is ac osmogenic isotope predominately produced in the stratosphere via the spallation of argon by cosmic rays. [179] By measuring all five sulfur isotopes ( 32 S, 33 S, 34 S, 35 S, and 36 S) in the same sulfate aerosols, Lin et al [176] found that D 33 Sv alues correlated with concentrations of stratospherically-sourced 35 S, while D 36 Sanomalies Figure 7. [179] By measuring all five sulfur isotopes ( 32 S, 33 S, 34 S, 35 S, and 36 S) in the same sulfate aerosols, Lin et al [176] found that D 33 Sv alues correlated with concentrations of stratospherically-sourced 35 S, while D 36 Sanomalies Figure 7.…”

“…[179] By measuring all five sulfur isotopes ( 32 S, 33 S, 34 S, 35 S, and 36 S) in the same sulfate aerosols, Lin et al [176] found that D 33 Sv alues correlated with concentrations of stratospherically-sourced 35 S, while D 36 Sanomalies Figure 7. [173] Thestudy by Lin et al [176] is not the final answer for the mysterious sulfur isotope effects in the modern atmosphere,b ut is am ajor discovery because the five-sulfur-isotope approach not only offers an ew way to understand stratospheric photochemistry,s tratosphere-troposphere interactions,a nd the atmospheric sulfur cycles,b ut also points to an ew direction for searching previously unknown mass independent sulfur isotope effects:t hermochemical reactions.T he possible physical chemistry basis of this potentially new reaction and its implications to the Archean record will be reviewed and discussed in the next section. Data compilation is obtained from Lin et al, [176] Shaheen et al, [117] and Au Yang et al [185] Angewandte Chemie Kurzaufsätze did not correlate with 35 Sb ut with varying biomass burning tracers (such as levoglucosan, mannosan, and potassium) and an index quantifying primary sulfates of combustion origins.It was preliminary concluded that there are at least two mass independent sulfur isotope effects in the modern atmosphere: (i)ana ltitude-dependent process (likely SO 2 photolytic reactions in the stratosphere or an unknown reaction in the troposphere required further identification) leading to large D 33 Sanomalies (small j D 36 S/D 33 S j values);(ii)acombustionrelated process resulting in large D 36 Sanomalies (large j D 36 S/ D 33 S j values), which are in line with the early combustion chamber experiment.…”

“…Coal burning is am ajor sulfur source in the modern atmosphere and most sulfate aerosols are produced via SO 2 oxidation. [176] Consequently,t he mass independent sulfur isotope effects observed in sulfate aerosols must be from sulfate formation processes during combustion and/or SO 2 oxidation in the ambient atmosphere (troposphere or stratosphere). Multiple sulfur isotopic measurements in SO 2 emitted from combustion also reveal near-zero D 33 Sa nd D 36 Sv alues.…”

“…Using as tate-of-the-art analytical technique (originally developed by Brothers et al [177] and further improved by Lin and Thiemens [178] ), cosmogenic 35 Sinaerosol samples can be measured in ah igh precision way and is demonstrated to be asensitive chemical tracer for identification of air masses originating from high altitudes. Data compilation is obtained from Lin et al, [176] Shaheen et al, [117] and Au Yang et al [185] Angewandte Chemie Kurzaufsätze did not correlate with 35 Sb ut with varying biomass burning tracers (such as levoglucosan, mannosan, and potassium) and an index quantifying primary sulfates of combustion origins.It was preliminary concluded that there are at least two mass independent sulfur isotope effects in the modern atmosphere: (i)ana ltitude-dependent process (likely SO 2 photolytic reactions in the stratosphere or an unknown reaction in the troposphere required further identification) leading to large D 33 Sanomalies (small j D 36 S/D 33 S j values);(ii)acombustionrelated process resulting in large D 36 Sanomalies (large j D 36 S/ D 33 S j values), which are in line with the early combustion chamber experiment. Mass independent sulfur isotope effects observed in coal, tropospheric aerosols and SO 2 in the modern atmosphere.…”