Exploring the atmospheric sulfur trends and the potential contribution of sulfate-reducing microorganism activities to the atmospheric sulfur budget at Saturna Island, B.C

<p>Anthropogenic and biogenic activities, along with the fluxes of sea salt, volcanic, wildfire and oceanic sulfate-reducing microorganisms (SRM), contribute significantly to the atmospheric sulfur budget.<sup>(1,2)</sup></p><p>There is still uncertainty and debate between studies about the magnitude of the importance of oceanic hydrogen sulfide (H<sub>2</sub>S) produced by SRM, as well as its ability to diffuse to the upper water column and its contribution to the atmospheric sulfur budget. While some studies believe that the majority of H<sub>2</sub>S is re-oxidized and is less likely to reach the atmosphere <sup>(3,4)</sup>, there is evidence of the existence of H<sub>2</sub>S in the upper water columns and even in the atmosphere <sup>(2,5)</sup>. H<sub>2</sub>S produced by SRM, emitted to the atmosphere, along with the anthropogenic sulfur dioxide (SO<sub>2</sub>) and dimethyl sulfide (DMS), undergo atmospheric oxidation processes. Sulfate (SO<sub>4</sub><sup>2-</sup>), as one of the main oxidized products, may nucleate with water vapor, ammonia and organic oxides <sup>(6,7)</sup>, and subsequently grow to bigger particle sizes. These particles affect the climate directly and indirectly and change the radiation balance of the Earth-atmosphere system. <sup>(8,9,10)</sup></p><p>This study assessed the seasonal trends of major atmospheric sulfur species including SO<sub>2</sub>, sulfate, and biogenic and anthropogenic sulfate of gas, aerosol and precipitation samples, collected by Canadian Air and Precipitation Monitoring Network (CAPMoN), Environment of Canada, at Saturna Island, B.C, between 1998-2010. We then explored the oceanic phytoplankton activities and DMS production, based on sulfur isotope composition and found the importance of DMS contribution to the summertime atmospheric sulfur budget. A handful of samples (~10-30%) displayed negative sulfur isotope compositions, outside the range of anthropogenic and biogenic isotope values. Potential factors that could produce such negative sulfur isotope composition values include isotopic fractionation, fluxes from mineral dust events, volcanic eruptions, wildfires and microbial sulfate reduction (MSR). Our study found that MSR was the only feasible explanation for these very negative sulfur isotope compositions in non-sea salt sulfate samples. H<sub>2</sub>S in our study was a 4<sup>th</sup> potential contributor to the atmospheric sulfur budget, along with the 3 major sources of anthropogenic, biogenic DMS, and sea-salt sulfate, in this long-term atmospheric sulfur study.</p><p> </p>

Phanerozoic variation in dolomite abundance linked to oceanic anoxia

The abundance of dolomitic strata in the geological record contrasts with the general rarity of locations where dolomite forms today, a discrepancy that has long posed a problem for their interpretation. Recent culture experiments show that dolomite can precipitate at room temperature, raising the possibility that many ancient dolomites may be of syngenetic origin. We compiled a large geodata set of secular variations in dolomite abundance in the Phanerozoic, coupled with compilations of genus richness of marine benthic invertebrates and sulfur-isotope variations in marine carbonates. These data show that dolomite abundance is negatively correlated to genus diversity, with four dolomite peaks occurring during mass extinctions. Dolomite peaks also correspond to the rapid increase in sulfur-isotope composition (δ34S), an indicator of enhanced sulfate reduction, in anoxic oceans. These results confirm that variations in dolomite abundance during the Phanerozoic were closely linked with changes in marine benthic diversity, with both in turn related to oceanic redox conditions.

Large sulfur isotope fractionation in lunar volcanic glasses reveals the magmatic differentiation and degassing of the Moon

Sulfur isotope variations in mantle-derived lavas provide important constraints on the evolution of planetary bodies. Here, we report the first in situ measurements of sulfur isotope ratios dissolved in primitive volcanic glasses and olivine-hosted melt inclusions recovered from the Moon by the Apollo 15 and 17 missions. The new data reveal large variations in 34S/32S ratios, which positively correlates with sulfur and titanium contents within and between the distinct compositional groups of volcanic glasses analyzed. Our results uncover several magmatic events that fractionated the primordial sulfur isotope composition of the Moon: the segregation of the lunar core and the crystallization of the lunar magma ocean, which led to the formation of the heterogeneous sources of the lunar magmatism, followed by magma degassing during generation, transport, and eruption of the lunar lavas. Whether the Earth’s and Moon’s interiors share a common 34S/32S ratio remains a matter of debate.

Isotopic systematics point to wild origin of mummified birds in Ancient Egypt

Millions of mummified birds serving for religious purpose have been discovered from archeological sites along the Nile Valley of Egypt, in majority ibises. Whether these birds were industrially raised or massively hunted is a matter of heavy debate as it would have a significant impact on the economy related to their supply and cult, and if hunted it would have represented an ecological burden on the birds populations. Here we have measured and analysed the stable oxygen, carbon and radiogenic strontium isotope compositions as well as calcium and barium content of bones along with the stable carbon, nitrogen and sulfur isotope composition of feathers from 20 mummified ibises and birds of prey recovered from various archeological sites of Ancient Egypt. If these migratory birds were locally bred, their stable oxygen, radiogenic strontium and stable sulfur isotopic compositions would be similar to that of coexisting Egyptians, and their stable carbon, nitrogen and oxygen isotope variance would be close, or lower than that of Egyptians. On one hand, isotopic values show that ibises ingested food from the Nile valley but with a higher isotopic scattering than observed for the diet of ancient Egyptians. On the other hand, birds of prey have exotic isotopic values compatible with their migratory behaviour. We therefore propose that most mummified ibises and all the birds of prey analysed here were wild animals hunted for religious practice.