The concurrent observation of methyl iodide and dimethyl sulphide in marine air; implications for sources of atmospheric methyl iodide

Continuous atmospheric measurements of methyl iodide and dimethyl sulphide were carried out at Mace Head, western Ireland, over a 4-week period in July 1996. The concurrent observations of methyl iodide and dimethyl sulphide reported here display a clear association, indeed statistical analysis indicated a very significant degree of covariance. A simple yet informative use of modelled 5-day back trajectories was employed in tandem with examination of local meteorology to illuminate the geographical source regions of methyl iodide and dimethyl sulphide. The interpretation of the atmospheric observations in terms of air-mass flow has elucidated part of the global methyl iodide cycle and provides evidence for two distinct source regions of methyl iodide:1. Under certain synoptic meteorological conditions, long-range transport of methyl iodide and dimethyl sulphide was observed from discrete areas of the sub-tropical Atlantic Ocean located in a region between 30–50°N and 20–50°W.2. Measurements taken under different conditions led us to believe that there was an additional source of methyl iodide that influenced the Mace Head atmosphere, most likely produced by coastal macroalgae which inhabit waters off the western coast of Ireland.     

Field measurements of hydrogen sulphide oxidation

The rate of production of SO₂ from H₂S was measured in a series of experiments in a broad, ground-level plume from geothermal vents in New Zealand. The mean rate constant for the reaction was 3.5 ± 1.3 × 10⁻³ min⁻¹ which produced a mean lifetime for H₂S oxidation of 500 ± 240 min. It is likely that the major oxidant of H₂S in the atmosphere is the OH radical, but it is also necessary to consider additional unknown mechanisms to fully explain the results.     

The role of a changing Arctic Ocean and climate for the biogeochemical cycling of dimethyl sulphide and carbon monoxide

Dimethyl sulphide (DMS) and carbon monoxide (CO) are climate-relevant trace gases that play key roles in the radiative budget of the Arctic atmosphere. Under global warming, Arctic sea ice retreats at an unprecedented rate, altering light penetration and biological communities, and potentially affect DMS and CO cycling in the Arctic Ocean. This could have socio-economic implications in and beyond the Arctic region. However, little is known about CO production pathways and emissions in this region and the future development of DMS and CO cycling. Here we summarize the current understanding and assess potential future changes of DMS and CO cycling in relation to changes in sea ice coverage, light penetration, bacterial and microalgal communities, pH and physical properties. We suggest that production of DMS and CO might increase with ice melting, increasing light availability and shifting phytoplankton community. Among others, policy measures should facilitate large-scale process studies, coordinated long term observations and modelling efforts to improve our current understanding of the cycling and emissions of DMS and CO in the Arctic Ocean and of global consequences.     

Catalytic combustion of methane over commercial catalysts in presence of ammonia and hydrogen sulphide

The performance of different commercially available catalysts (supported Pd, Pt, Rh, bimetallic Pd-Pt, and Cr-Cu-Ti oxide catalyst) for the oxidation of methane, alone and in presence of ammonia and hydrogen sulphide is studied in this work. Catalysts performance was evaluated both in terms of activity and resistance to poisoning. The main conclusions are that supported Pd and Rh, present the highest activities for methane oxidation, both alone and in presence of ammonia, whereas they are severely poisoned in presence of H2S. Pt and Cr-Cu-Ti are less active but more sulphur resistant, but their activity is lower than the residual activity of sulphur-deactivated Pd and Rh catalysts. The Pd-Pt catalyst exhibits low activity and it is quickly deactivated in presence of hydrogen sulphide.     

Cationic surfactant as a sensitizer for the spectrophotometric determination of hydrogen sulphide in air and evaluation of a new absorbing medium containing triethanolamine-zinc acetate-sodium hydroxide

An extractive spectrophotometric method for the determination of trace amounts of hydrogen sulphide after fixing the gas in triethanolamine (TEA)-zinc acetate-sodium hydroxide solution is described. The method is based on the reaction of iodate with hydrogen sulphide in the presence of acid and excess chloride ion leading to the formation of ICl2- species which is used to iodinate 2',7'-dichlorofluorescein to form 2',7'-dichloro-4',5'-diiodofluorescein. The iodinated product formed is extracted into an organic solvent and sensitized by equilibrating with a cationic surfactant, cetrimide, in the presence of acetate buffer (pH 5.9 +/- 0.1). The colour system obeys Beer's law over the range 0-1 microg of hydrogen sulphide and the relative standard deviation is 2.4% for 10 determinations at 0.75 microg of hydrogen sulphide. The effect of interfering gases on the determination is discussed. The proposed absorbing solution has been evaluated using a hydrogen sulphide permeation device. This absorbing solution has an absorption efficiency of > 93% at a flow rate of 1.5 litre min(-1) for a sampling period of 2 h. The fixed H2S is stable for 40 days. The method has been applied to determine residual H2S levels in a laboratory fume hood and in the vicinity of sewage pumping station. The method can be used to determine as little as 0.05 microg of hydrogen sulphide.     

How oxygen deficiency in the Baltic Sea proper has spread and worsened: The role of ammonium and hydrogen sulphide

Even large inflows of oxygen-rich seawater to the Baltic Proper have in recent decades given only short-lived relief from oxygen deficiency below the halocline. We analyse long-term changes in oxygen deficiency, and calculate the “total oxygen debt” ΣOD, the oxygen required to oxidize the hydrogen sulphide (H₂S) and ammonium (NH₄) that builds up during stagnation periods. Since the early 1990s, oxygen below 65m has gradually decreased during successive stagnation periods, and the ΣOD has increased, with NH₄ more important than previously recognised. After the major inflow in 2014, the Baltic Proper ΣOD has reached its highest level so far. The gradual shift of the ΣOD to shallower sub-halocline waters in the western and northern basins has increased the risk of periodic coastal hypoxia and export of hypoxic water to the Bothnian Sea. The potential for inflows large enough to more than eliminate the ΣOD seems limited in the near term.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-022-01738-8.     

Chemisorption of hydrogen sulphide and methanethiol by light expanded clay aggregates (Leca)

Removal of volatile sulphur compounds from livestock waste air by biological air filtration may be enhanced by application of packing materials with reactive properties. In this study, light expanded clay aggregates (Leca®) was tested with respect to sorption and potential chemical degradation of H₂S, Methanethiol (MT) and Dimethyl sulphide (DMS). Leca was selected due to its content of minerals, including iron, and due to its high specific surface area. The performance of Leca was evaluated based on breakthrough curves and by comparing the difference between the inlet and outlet gas concentrations. Whereas DMS did not appear to be removed by Leca, both H₂S and MT were removed with variable efficiency depending on the specific conditions. Dimethyl disulphide (DMDS) and dimethyl trisulphide (DMTS) were demonstrated to be produced during the degradation process in relatively high yields. A comparison between ambient air and nitrogen gas conditions showed that the chemisorption of H₂S and MT did not necessarily need oxygen to be present. X-ray analysis of Leca showed an abundance of Fe₂O₃. It is therefore hypothesized that Fe₂O₃ in Leca can remove H₂S and MT by chemisorption. Both air velocity and moisture content clearly affected the capacity of Leca for removal of H₂S and MT. Lower removal is seen at higher air velocities, whereas higher moisture content enhances removal. However, chemisorption of MT by Leca appears to be limited above a threshold moisture level. Potential reaction mechanisms are discussed in relation to the observed effects. The results implicate that Leca can be used as a filter material with reactive properties provided that moisture content is controlled and that an adequate air velocity is used.     

铁氧化物多孔陶粒生物滴滤塔净化硫化氢气体

采用装有凹凸棒石基铁氧化物多孔陶粒作为填料的生物滴滤塔,进行了长期实验室H2S脱臭实验。结果表明,该生物滴滤塔H2S的进气浓度低于500 mg/m3 时,循环营养液喷淋量高于1.5 L/h,气体最佳停留时间为54.9 s,去除率在95 % 以上。代谢产物以SO42-为主,转化速率在52.42 g/(m3·d)左右。该滴滤塔系统可稳定而有效运行。生物相观察表明,滴滤塔填料表面附着大量微生物,铁氧化物陶粒具有化学和生物惰性,有利于微生物的附着。     

Development of effective hydrogen sulphide removing equipment using Thiobacillus sp.IW

Hydrogen sulphide is one of the commonest odours emitted by chemical plants. To remove the hydrogen sulphide biologically, a three phase fluidised bed bioreactor was used in which Thiobacillus sp.IW was immobilised on activated carbon. The optimum operating conditions of the bioreactor were 30 degrees C, pH7, aspect ratio (L/D) = 1 and at these conditions, the system removed over 94% of the hydrogen sulphide in the concentration range of 100-200 ppm and flow rate of 1.0-2.0 litre min(-1). From the upset and recovery test, the system proved stable within the moderate inlet concentration changes investigated.     

Simultaneous use of relaxed eddy accumulation and gradient flux techniques for the measurement of sea-to-air exchange of dimethyl sulphide

The sea-to-air flux of the biogenic volatile sulphur compound dimethyl sulphide was assessed with the relaxed eddy accumulation (REA) and the gradient flux (GF) techniques from a stationary platform in the coastal Atlantic Ocean. Fluxes varied between 2 and 16 μmol m⁻² d⁻¹. Fluxes derived from REA were on average 7.1±5.03 μmol m⁻² d⁻¹, not significantly different from the average flux of 5.3±2.3 μmol m⁻² d⁻¹ derived from GF measurements. Gas transfer velocities were calculated from the fluxes and seawater DMS concentrations. They were within the range of gas transfer rates derived from the commonly used parameterizations that relate gas transfer to wind speed.     

Biodegradation of hydrogen sulphide by inoculated Rhodococcus sp.zw11 in a pilot-scale biotrickling filter

A strain of autotrophic micro-organism, Rhodococcus sp.zw11, was isolated from pharmaceutical wastewater containing hydrogen sulphide (H₂S). The shape, physiological and biochemical characteristics and oxidation capacity of Rhodococcus sp.zw11 were studied, and the effect of inlet concentration and volumetric loading of H₂S on the removal efficiency was evaluated by the biotrickling filter inoculated with Rhodococcus sp.zw11. The results suggested that the optimal temperature of Rhodococcus sp.zw11 (aerobic bacilli, short rod and gram-negative) was from 20°C to 28°C and the optimal pH was from 5.5 to 6.5. The criteria necessary for a scale-up design of the biotrickling filter were established, and pressure drops at the start and end of the experiment were investigated. The optimal inlet loading could be noted as 180 g/m³h, corresponding to H₂S removal efficiency close to 100%. Furthermore, the inoculated biotrickling filter had good ability to resist shock loading, which was a potential industrialisation method to control H₂S emissions.     

Geothermal power plants at Mt. Amiata (Tuscany-Italy): mercury and hydrogen sulphide deposition revealed by vegetation

At Mt. Amiata (Italy) geothermal energy is used, since 1969, to generate electricity in five plants with a nominal capacity of 88 MW. Anomalous levels of mercury characterise geothermal fluids of Mt. Amiata, an area renowned for its vast cinnabar deposits and for the mercury production carried out in the past. Mercury emission rates range from 300 to 400 g/h, or 3-4 g/h per MW electrical installed capacity. These emissions are coupled with a release of 7-8 kg/(h MW) of hydrogen sulphide (H2S). Mercury is discharged as Hg0 gaseous species and reaches the atmosphere with the non-condensable gas fraction. In this fraction, CO, is the major component (94-98%), H2S is around 1% and mercury concentration is as high as 1-10 mg/Nm3. Leaves of a spontaneous grass (Avena sterilis), at the end of the vegetative cycle, were used as mercury bioconcentrators to map deposition near geothermal power plants and to calculate the corresponding average levels of Hg0 in the air. Direct measurements of mercury and hydrogen sulphide vapours in the air reached by power plant emissions showed a ratio of about 1-2000. This ratio was applied to calculate average levels of hydrogen sulphide starting from mercury deposition mapping: typical concentrations of mercury and hydrogen sulphide were of the order of 10-20 ng/m3 and 20-40 microg/m3, respectively.     

Biological treatment process of air loaded with an ammonia and hydrogen sulfide mixture

The physico-chemical characteristics of granulated sludge lead us to develop its use as a packing material in air biofiltration. Then, the aim of this study is to investigate the potential of unit systems packed with this support in terms of ammonia and hydrogen sulfide emissions treatment. Two laboratory scale pilot biofilters were used. A volumetric load of 680 g H2S m(-3) empty bed day(-1) and 85 g NH3 m(-3) empty bed day(-1) was applied for eight weeks to a unit called BGSn (column packed with granulated sludge and mainly supplied with hydrogen sulfide); a volumetric load of 170 g H2S m(-3) empty bed day(-1) and 340 g NH3 m(-3) empty bed day(-1) was applied for eight weeks to the other called BGNs (column packed with granulated sludge and mainly supplied with ammonia). Ammonia and hydrogen sulfide elimination occur in the biofilters simultaneously. The hydrogen sulphide and ammonia removal efficiencies reached are very high: 100% and 80% for BGSn; 100% and 80% for BGNs respectively. Hydrogen sulfide is oxidized into sulphate and sulfur. The ammonia oxidation products are nitrite and nitrate. The nitrogen error mass balance is high for BGSn (60%) and BGNs (36%). This result could be explained by the denitrification process which would have occurred in anaerobic zones. High percentages of ammonia or hydrogen sulfide are oxidized on the first half of the column. The oxidation of high amounts of hydrogen sulfide would involve some environmental stress on nitrifying bacterial growth and activity.