From the HINDAS Project : Excitation Functions for Residual Nuclide Production by Proton-Induced Reactions

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Global 3D model analysis of the seasonal cycle of atmospheric carbonyl sulfide: Implications for terrestrial vegetation uptake

We use a global 3-D simulation of atmospheric carbonyl sulfide (COS) to interpret observations at a network of surface sites. We aim to identify the primary factors underlying observed seasonal variations and to constrain COS uptake by terrestrial vegetation. Model simulations are based on a recent estimate of global COS fluxes, with closure between sources and sinks. We find that the dominant influences on seasonal variation of COS are terrestrial vegetation uptake in the northern extratropics, and ocean fluxes in the southern extratropics. Simulations underestimate the amplitude of the observed seasonal cycle in the northern hemisphere, particularly at terrestrial sites, indicating that COS uptake by terrestrial vegetation has been underestimated in recent budgets. Fitting the observed seasonal variation at northern hemisphere sites in the model requires a doubling of the global vegetation sink to ~490 Gg S y-1, while fitting the southern hemisphere data suggests a reduction of ~50 Gg S y-1 in the southern extratropical ocean source. Balancing these changes in COS fluxes requires an additional source (~235 Gg S y-1, equivalent to 40% of identified sources) missing from present budget estimates. Discrepancies between annual mean observations and simulated concentrations, derived from our best estimates of seasonal fluxes, are largest in the tropics, suggesting an underestimate of COS sources at these latitudes

A 350-year atmospheric history for carbonyl sulfide inferred from Antarctic firn air and air trapped in ice

Carbonyl sulfide (COS) and other trace gases were measured in firn air collected near South Pole (89.98°S) and from air trapped in ice at Siple Dome, Antarctica (81.65°S). The results, when considered with ambient air data and previous ice core measurements, provide further evidence that atmospheric mixing ratios of COS over Antarctica between 1650 and 1850 A.D. were substantially lower than those observed today. Specifically, the results suggest annual mean COS mixing ratios between 300 and 400 pmol mol−1 (ppt) during 1650–1850 A.D. and increases throughout most of the twentieth century. Measurements of COS in modern air and in the upper layers of the firn at South Pole indicate ambient, annual mean mixing ratios between 480 and 490 ppt with substantial seasonal variations. Peak mixing ratios are observed during austral summer in ambient air at South Pole and Cape Grim, Tasmania (40.41°S). Provided COS is not produced or destroyed in firn, these results also suggest that atmospheric COS mixing ratios have decreased 60–90 ppt (10–16%) since the 1980s in high latitudes of the Southern Hemisphere. The history derived for atmospheric mixing ratios of COS in the Southern Hemisphere since 1850 is closely related to historical anthropogenic sulfur emissions. The fraction of anthropogenic sulfur emissions released as COS (directly or indirectly) needed to explain the secular changes in atmospheric COS over this period is 0.3–0.6%

Bacterial CS2 Hydrolases from Acidithiobacillus thiooxidans Strains Are Homologous to the Archaeal Catenane CS2 Hydrolase

Contains fulltext : 119229.pdf (publisher's version ) (Closed access)Carbon disulfide (CS2) and carbonyl sulfide (COS) are important in the global sulfur cycle, and CS2 is used as a solvent in the viscose industry. These compounds can be converted by sulfur-oxidizing bacteria, such as Acidithiobacillus thiooxidans species, to carbon dioxide (CO2) and hydrogen sulfide (H2S), a property used in industrial biofiltration of CS2-polluted airstreams. We report on the mechanism of bacterial CS2 conversion in the extremely acidophilic A. thiooxidans strains S1p and G8. The bacterial CS2 hydrolases were highly abundant. They were purified and found to be homologous to the only other described (archaeal) CS2 hydrolase from Acidianus strain A1-3, which forms a catenane of two interlocked rings. The enzymes cluster in a group of beta-carbonic anhydrase (beta-CA) homologues that may comprise a subclass of CS2 hydrolases within the beta-CA family. Unlike CAs, the CS2 hydrolases did not hydrate CO2 but converted CS2 and COS with H2O to H2S and CO2. The CS2 hydrolases of A. thiooxidans strains G8, 2Bp, Sts 4-3, and BBW1, like the CS2 hydrolase of Acidianus strain A1-3, exist as both octamers and hexadecamers in solution. The CS2 hydrolase of A. thiooxidans strain S1p forms only octamers. Structure models of the A. thiooxidans CS2 hydrolases based on the structure of Acidianus strain A1-3 CS2 hydrolase suggest that the A. thiooxidans strain G8 CS2 hydrolase may also form a catenane. In the A. thiooxidans strain S1p enzyme, two insertions (positions 26 and 27 [PD] and positions 56 to 61 [TPAGGG]) and a nine-amino-acid-longer C-terminal tail may prevent catenane formation