Biogenic Sulfur Research Articles

Sulfide addition accelerates anammox sludge granulation and promotes microbial cooperation

The granular anaerobic ammonium oxidation (anammox) system has attractive advantages in tolerance to environmental-stress and enhancement of nitrogen removal capacity. Sulfide addition can improve nitrogen removals in anammox systems via inducing sulfur denitrification, yet its function in the improvement of the property of anammox granular sludge remains unclear. Herein, we investigated the variations in the morphological and microbial properties of the anammox sludge response to different sulfide concentrations (Na2S: 10–100 mg/L) through a long-term experiment. By comparing the sludge diameter and heme c content, it comes that a relatively low sulfide (S/N [nitrate] molar ratio of 0.18–0.50) significantly promoted the average diameter and heme c concentration of sludge by 25–175 % and 75–95 %, respectively, compared to that of both without sulfide addition and a high sulfide addition (S/N > 0.85). This enhancement is primarily because a low amount of sulfide had stimulated the secretion of extracellular polymeric substance, induced slight biogenic sulfur accumulation as microbial nuclei, and facilitated the appropriate amount of filamentous bacteria proliferation. Microbial metabolism functions analyses revealed a robust granular anammox coupled with sulfur denitrification in the sulfide-mediated anammox reactor, and the assembled granules exhibited exceptional tolerance to environmental stress. Significantly, the anammox bacteria (Candidatus_Brocadia) dominating the granules displayed satisfactory anammox activity (21.8 ± 2.1 mg N/g VSS h), and their produced nitrate was efficiently removed by the sulfur-oxidizing bacteria (Thiobacillus) that predominantly occurred in the flocs. This collaboration ensured an efficient sulfide-mediated anammox granules system, achieving nitrogen removal efficiency exceeding 95 %. These results highlight the function of sulfide in improving the morphological property of anammox sludge as well as the creation of a favorable ecological niche for the functional microorganism, which is important to maintain the efficiency and robustness of the anammox process in treating wastewater.

Surface-air exchanges of H2S and SO2 in an urban wetland in eastern China

Wetlands are widely recognized as hot spots for the emission or deposition of biogenic sulfur gases, including hydrogen sulfur (H2S) and sulfur dioxide (SO2), which significantly affect air quality and climate change. With the expansion of urban wetlands, it is critical to know the roles that urban wetlands played in atmospheric H2S and SO2 budget. In this study, the surface-air exchange fluxes of H2S and SO2 were measured by the Dynamic Flux Chamber (DFC) method in a typical urban wetland in eastern China from Sep 2022 to July 2023. It was found that the urban wetland did not have the expected high H2S emission, might be caused by the relatively high pH value and low sulfate concentration in the soil. Although H2S showed emission in the daytime of spring and summer, an overall H2S flux of −0.04 kg S ha−1 yr−1 was observed throughout the year. Meanwhile, the urban wetland presented a net sink of SO2, with a deposition flux of 0.14 kg S ha−1 yr−1. The negative peaks of SO2 flux corresponded to the suddenly elevated SO2 concentration in the ambient air especially in spring and winter. Through linear fitting of SO2 flux and concentration, the concept of SO2 “compensation point” was proposed. The compensation point is the concentration level at which the observed SO2 flux equals zero. The “compensation point” changed with the season and was related to temperature and humidity. The “compensation point” in summer and autumn were larger, being 2.37 ppb and 1.40 ppb, respectively, while they were 1.07 ppb and 0.86 ppb in spring and winter respectively. Our results suggest that the urban wetland expansion may have little risk of increasing air H2S but could act as a significant sink of SO2 with high SO2 concentration in the urban region.

IPB-MSA&SO4: a daily 0.25° resolution dataset of in situ-produced biogenic methanesulfonic acid and sulfate over the North Atlantic during 1998–2022 based on machine learning

Abstract. Accurate long-term marine-derived biogenic sulfur aerosol concentrations at high spatial and temporal resolutions are critical for a wide range of studies, including climatology, trend analysis, and model evaluation; this information is also imperative for the accurate investigation of the contribution of marine-derived biogenic sulfur aerosol concentrations to the aerosol burden, for the elucidation of their radiative impacts, and to provide boundary conditions for regional models. By applying machine learning algorithms, we constructed the first publicly available daily gridded dataset of in situ-produced biogenic methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO4=) concentrations covering the North Atlantic. The dataset is of high spatial resolution (0.25° × 0.25°) and spans 25 years (1998–2022), far exceeding what observations alone could achieve both spatially and temporally. The machine learning models were generated by combining in situ observations of sulfur aerosol data from Mace Head Atmospheric Research Station, located on the west coast of Ireland, and from the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) cruises in the northwestern Atlantic with the constructed sea-to-air dimethylsulfide flux (FDMS) and ECMWF ERA5 reanalysis datasets. To determine the optimal method for regression, we employed five machine learning model types: support vector machines, decision tree, regression ensemble, Gaussian process regression, and artificial neural networks. A comparison of the mean absolute error (MAE), root-mean-square error (RMSE), and coefficient of determination (R2) revealed that Gaussian process regression (GPR) was the most effective algorithm, outperforming the other models with respect to simulating the biogenic MSA and nss-SO4= concentrations. For predicting daily MSA (nss-SO4=), GPR displayed the highest R2 value of 0.86 (0.72) and the lowest MAE of 0.014 (0.10) µg m−3. GPR partial dependence analysis suggests that the relationships between predictors and MSA and nss-SO4= concentrations are complex rather than linear. Using the GPR algorithm, we produced a high-resolution daily dataset of in situ-produced biogenic MSA and nss-SO4= sea-level concentrations over the North Atlantic, which we named “In-situ Produced Biogenic Methanesulfonic Acid and Sulfate over the North Atlantic” (IPB-MSA&SO4). The obtained IPB-MSA&SO4 data allowed us to analyze the spatiotemporal patterns of MSA and nss-SO4= as well as the ratio between them (MSA:nss-SO4=). A comparison with the existing Copernicus Atmosphere Monitoring Service ECMWF Atmospheric Composition Reanalysis 4 (CAMS-EAC4) reanalysis suggested that our high-resolution dataset reproduces the spatial and temporal patterns of the biogenic sulfur aerosol concentration with high accuracy and has high consistency with independent measurements in the Atlantic Ocean. IPB-MSA&SO4 is publicly available at https://doi.org/10.17632/j8bzd5dvpx.1 (Mansour et al., 2023b).

Biogenic Sulfur Gases as Biosignatures on Temperate Sub-Neptune Waterworlds

Theoretical predictions and observational data indicate a class of sub-Neptune exoplanets may have water-rich interiors covered by hydrogen-dominated atmospheres. Provided suitable climate conditions, such planets could host surface liquid oceans. Motivated by recent JWST observations of K2-18 b, we self-consistently model the photochemistry and potential detectability of biogenic sulfur gases in the atmospheres of temperate sub-Neptune waterworlds for the first time. On Earth today, organic sulfur compounds produced by marine biota are rapidly destroyed by photochemical processes before they can accumulate to significant levels. Domagal-Goldman et al. suggest that detectable biogenic sulfur signatures could emerge in Archean-like atmospheres with higher biological production or low UV flux. In this study, we explore biogenic sulfur across a wide range of biological fluxes and stellar UV environments. Critically, the main photochemical sinks are absent on the nightside of tidally locked planets. To address this, we further perform experiments with a 3D general circulation model and a 2D photochemical model (VULCAN 2D) to simulate the global distribution of biogenic gases to investigate their terminator concentrations as seen via transmission spectroscopy. Our models indicate that biogenic sulfur gases can rise to potentially detectable levels on hydrogen-rich water worlds, but only for enhanced global biosulfur flux (≳20 times modern Earth’s flux). We find that it is challenging to identify DMS at 3.4 μm where it strongly overlaps with CH4, whereas it is more plausible to detect DMS and companion byproducts, ethylene (C2H4) and ethane (C2H6), in the mid-infrared between 9 and 13 μm.

Biogenic sulfur as an effective source for sulfidogenesis via sulfur disproportionation (S0Disp)

Sulfidogensis via element sulfur disproportionation (S0Disp) has been recently suggested to be a cost-effective and low carbon footprint process to produce sulfide for wastewater treatment such as denitrification and the removal of heavy metals. However, studies on this process are limited in using the industrial grade chemical sulfur (Chem-S0). In this study, biogenic sulfur (Bio-S0), a solid waste produced from biogas bio-desulfurization, was investigated for the first time in the S0Disp process with the performance compared to the Chem-S0 with identical size. The results showed that the S0Disp process driven by Bio-S0 was initiated more rapidly than that by the Chem-S0 (8 d vs 13 d) and performed a 1.2-fold higher sulfide production rate in the steady phase. A series of characterizations were conducted to elucidate the difference between using these two types of S0 in disproportionation. The faster initiation of Bio-S0 sets was suggested to correlate its hydrophilic properties, while the higher sulfide production rate was likely due to its higher reactivity as indicated by the lower crystallinity and the presence of organic polysulfane with lower dissociation energy for the S-S bond. Additional tests demonstrated that the Bio-S0 could be more readily attacked by the sulfide to produce polysulfide, a putative rate-limiting step of S0 taken by bacteria in the S0Disp process. Moreover, the sulfur-disproportionating bacteria were found to be enriched more in the Bio-S0 set, which might also contribute to the higher sulfide production rate. This study extended the knowledge of Bio-S0 in good bioavailability and offered new opportunities for reusing this solid waste.

ГЕТЕРОЦИКЛИЧЕСКИЕ ТИОПРОИЗВОДНЫЕ КАМФЕНА С ФРАГМЕНТОМ ФЕНИЛТЕТРАЗОЛА

It is known that the tetrazole ring is an important pharmacophore fragment included in the structure of drugs with more than 20 types of biological activity. In order to obtain new biologically active thioterpenoids with heterocyclic fragments, we set the task of combining the natural terpene skeleton and the nitrogen-containing heterocyclic function through the biogenic sulfur atom. We have used thiylation and sulfenylchlorination of (+)-camphene and its derivatives, which are difficult to obtain synthetically (cyclopropene and allene), with 1-phenyltetrazole-5-thiol and 1-phenyltetrazole-5-sulfenyl chloride. Studying the structure of hetarene sulfide obtained by the reaction of camphene with 1-phenyltetrazole-5-thiol in the presence of a Lewis acid (boron trifluoride etherate), allowed us to conclude that during the reaction a Wagner-Meerwein rearrangement occurs. The rearrangement leads to isomerization of the initial camphane structure with the formation of a terpene sulfide of bornane structure with an exo-position of the sulfide group relative to the bicyclic skeleton of the molecule. In non-catalytic sulfenylchlorination reactions isomerization of the camphene skeleton is not observed. 2,2-Dimethylnorbornane-3-spirocyclopropene forms the product of the “normal” addition of 1-phenyltetrazole-5-sulphenyl chloride to the double bond of cyclopropene. A mixture of two regioisomers with a trans-position of the sulfide group and a chlorine atom is observed. In this case, the chlorine atom is located on the endo side of the cyclopropane ring relative to the gem-dimethyl group, while the sulfide group is on the exo side. Sulfenylchlorination of 2,2-dimethyl-3-ethenylidenenorbornane occurs regio- and stereospecifically at a sterically less hindered double bond, with the sulfide group located at the C-10 atom and the chlorine atom at the C-11 atom.

Response of distributions and emissions of summer biogenic sulfur in the Pacific Arctic to enhanced Pacific Water inflow

AbstractThe inflow of warm and nutrient‐rich Pacific Water (PW) through the Bering Strait into the Arctic Ocean is likely to have far‐reaching consequences for the ecosystem and biogenic sulfur cycle in the Earth's sensitive subarctic–arctic region of the Pacific sector, even impacting climate change under global warming scenarios. We performed a detailed biogeochemical study of summer biogenic sulfur cycling from cold (2012) to warm (2014) years in the Bering Strait and the Chukchi Sea, so as to highlight the importance of enhanced Pacific inflow in driving dimethylsulfide (DMS) variability. In the Bering Strait, the enhanced Pacific inflow led to the vertical expansion of the eastern high‐DMS regions due to the vertical extension of Alaska Coastal Water, and the horizontal expansion of the western surface high‐DMS regions due to the westward intrusion of Bering Shelf Water. The enhanced extension of PW potentially stimulated seawater warming, the northward retreat of the ice edge, and the enlargement of sea ice‐free areas in the Chukchi Sea. The northern ice melting zone at 71°N with a bloom of phytoplankton was an area of locally high dimethylsulfoniopropionate concentrations and slow DMS consumption in 2012. A hotspot for dimethylated sulfur compound concentrations and DMS sea–air flux occurred in the convergence region near 67.7°N during 2014, due to enhanced mixing caused by increased Bering Sea Water. Owing to the increased advection of PW during 2012–2014, surface DMS and its emission to the atmosphere increased sharply by threefold in the Chukchi Sea.

Industrial-era decline in Arctic methanesulfonic acid is offset by increased biogenic sulfate aerosol.

Marine phytoplankton are primary producers in ocean ecosystems and emit dimethyl sulfide (DMS) into the atmosphere. DMS emissions are the largest biological source of atmospheric sulfur and are one of the largest uncertainties in global climate modeling. DMS is oxidized to methanesulfonic acid (MSA), sulfur dioxide, and hydroperoxymethyl thioformate, all of which can be oxidized to sulfate. Ice core records of MSA are used to investigate past DMS emissions but rely on the implicit assumption that the relative yield of oxidation products from DMS remains constant. However, this assumption is uncertain because there are no long-term records that compare MSA to other DMS oxidation products. Here, we share the first long-term record of both MSA and DMS-derived biogenic sulfate concentration in Greenland ice core samples from 1200 to 2006 CE. While MSA declines on average by 0.2 µg S kg-1 over the industrial era, biogenic sulfate from DMS increases by 0.8 µg S kg-1. This increasing biogenic sulfate contradicts previous assertions of declining North Atlantic primary productivity inferred from decreasing MSA concentrations in Greenland ice cores over the industrial era. The changing ratio of MSA to biogenic sulfate suggests that trends in MSA could be caused by time-varying atmospheric chemistry and that MSA concentrations alone should not be used to infer past primary productivity.

In situ biomass burning enhanced the contribution of biogenic sources to sulfate aerosol in subtropical cities

Sulfurous gases released by biogenic sources play a key role in the global sulfur cycle. However, the contribution of biogenic sources to sulfate aerosol in the urban atmosphere has received little attention. Emission sources and formation process of sulfate in Guangzhou, a subtropical mega-city in China, were clarified using multiple methods, including isotope tracers and chemical markers. The δ18O of sulfate suggested that secondary sulfate was the dominant component (84 %) of sulfate aerosol, which mainly formed by transition metal ion (TMI) catalyzed oxidation (31 %) and OH radical oxidation (30 %). The factors driving secondary sulfate formation were revealed using a tree boosting model, which suggested that NH3, temperature, and oxidants were the most important factors. The δ34S of sulfate indicated that biogenic sources accounted for annual average of 26.0 % of the sulfate, which increased to 30.4 % in winter monsoon period. Rice straw burning enhanced sulfate formation by promoting the release of reduced sulfur from soil, which is rapidly converted into sulfate under a subtropical urban atmosphere with high concentration of NH3 and oxidants. This study revealed the important influence of rice straw burning on biogenic sulfur emission during the rice harvest, thereby providing insight into the sulfur cycle and regional air pollution.

Evaluating the effectiveness of low-sulphur marine fuel regulations at improving urban ambient PM2.5 air quality: Source apportionment of PM2.5 at Canadian Atlantic and Pacific coast cities with implementation of the North American Emissions Control Area

Ambient fine size fraction particulate matter (PM2.5) sources were resolved by positive matrix factorization at two Canadian cities on the Atlantic and Pacific coast over the 2010–2016 period, corresponding to implementation of the North American Emissions Control Area (NA ECA) low-sulphur marine fuel regulations. Source types contributing to local PM2.5 concentrations were: ECA regulation-related (residual oil, anthropogenic sulphate), urban transportation and residential (gasoline, diesel, secondary nitrate, biomass burning, road dust/soil), industry (refinery, Pb-enriched), and largely natural (biogenic sulphate, sea salt). Anthropogenic sources accounted for approximately 80 % of PM2.5 mass over 2010–2016. Anthropogenic and biogenic sources of PM2.5-sulphate were separated and apportioned. Anthropogenic PM2.5-sulphate was approximately 2–3 times higher than biogenic PM2.5-sulphate prior to implementation of the NA ECA low-S marine fuel regulations, decreasing to 1–2 times higher after regulation implementation. Non-marine anthropogenic sources (gasoline, road dust, local industry factors) were shown to together contribute 38 % - 45 % of urban PM2.5. At both coastal cities, the residual oil and anthropogenic sulphate factors clearly reflected the effects of the low-S fuel regulations at reducing primary and secondary sulphur-related PM2.5 emissions. Comparing a pre-regulation and post-regulation period, residual oil combustion PM2.5 decreased by 0.24–0.25 μg/m3 (94%–95 % decrease) in both cities and anthropogenic sulphate PM2.5 decreased by 0.78 μg/m3 in Halifax (47 % decrease) and 0.71 μg/m3 in Burnaby (58 % decrease). Regulation-related PM2.5 across these factors decreased by approximately 1 μg/m3 after regulation implementation, providing a quantified lower estimate of the beneficial influence of the regulations on urban ambient PM2.5 concentrations. Further reductions in coastal city ambient PM2.5 may best consider air quality strategies that include multiple sources, including marine shipping and non-marine anthropogenic source types given this analysis found that marine vessel emissions remain an important source of urban ambient PM2.5.

Low contributions of dimethyl sulfide (DMS) chemistry to atmospheric aerosols over the high Arctic Ocean

The Arctic Ocean is continuously warming, resulting in sea ice retreat, which significantly impacts the marine biogenic sulfur cycle. The formation of aerosols from DMS oxidation and their climatic effects in polar regions are of great concern. However, the impact of DMS chemistry on atmospheric aerosols in the high Arctic Ocean (AO) is still unclear due to the limitation of field observations and datasets. Gaseous methanesulfonic acid (MSA) and aerosol chemical species (MSA, SO42− and DMA, etc.) were determined simultaneously with a high time resolution (1 h) in the AO and Pacific Ocean (PO) to reveal the DMS chemistry in these regions. The particulate MSA concentration indicated significant spatial variation with a decreasing tendency from the low latitude oceans to high AO. Extremely low particulate MSA concentrations were observed in the high AO, with an average of only 7.42 ± 6.6 ng·m−3. In contrast, highest particulate MSA concentrations, with an average of 168.6 ± 167.6 ng·m−3 were observed in the mid-latitude regions (45°–60°N) in July. Sea salt aerosols were the most dominant source in the high Arctic Ocean, accounting for 88.78% of the total suspended particle mass, which was much larger than the values in the other regions. Low DMS chemistry was determined based on the low DMS emissions in the high latitude (HL, 75°–85°N) region. These results highlight the contribution of DMS chemistry to atmospheric aerosols and extend the knowledge of how biogenic aerosols impact the regional atmosphere in the high AO.

Bioleaching of the α-alumina layer of spent three-way catalysts as a pretreatment for the recovery of platinum group metals

Acid bioleaching of Al by Acidithiobacillus thiooxidans has been explored as an environmentally friendly pretreatment to facilitate the extraction of platinum group metals from spent three-way catalysts (TWC). Biogenic sulfur obtained from desulfurization bioreactors improved the production of acid by A. thiooxidans compared to commercially available elemental sulfur. The lixiviation abilities of bacteria-free biogenic acid and biogenic acid with exponential or stationary phase bacteria were compared against a control batch produced by commercial H2SO4. The maximum Al leaching percentage (54.5%) was achieved using biogenic acids with stationary-phase bacteria at a TWC pulp density of 5% w/v whereas bacteria-free biogenic acid (23.4%), biogenic acid with exponential phase bacteria (21.7%) and commercial H2SO4 (24.7%) showed lower leaching abilities. The effect of different pulp densities of ground TWC (5, 30, and 60% w/v) on Al leaching and bacterial growth was determined. While greater Al leaching yields were obtained at lower TWC pulp density solutions (54.5% at 5% w/v and 2.5% at 60% w/v), higher pulp densities enhanced microbial growth (2.3 × 109 cells/mL at 5% w/v and 9.5 × 1010 cells/mL at 60% w/v). The dissolution of the metal from the solid into the liquid phase triggered the production of biological polymeric substances that were able to absorb traces of both Al (up to 24.80% at 5% w/v) and Pt (up to 0.40% at 60% w/v).

Pharmaceutical blister waste recycling using biogenic sulfuric acid: Effect of sulfur source and blister material on bioleaching efficiency

Several thousand tons of plastic are produced globally for pharmaceutical blister packages every year, leading to an expected consumption of over 2.8 million tons by 2026. Comprising a complex multilayer structure, blisters cannot be recycled in conventional recycling processes, leading to a loss of aluminium and valuable polymers during incineration and landfilling. As a promising secondary source of aluminium, new recycling strategies need to be developed to selectively separate the different layers. In this study, three types of blister packaging materials consisting of 13–68% (w/w) aluminium were investigated regarding aluminium and polymer recovery by using biogenic sulfuric acid for bioleaching. Waste elemental sulfur from biogas desulfurisation was assessed for biogenic sulfuric acid production by the two sulfur-oxidizing bacteria Acidithiobacillus thiooxidans and Acidithiobacillus caldus and compared to commercial elemental sulfur. For biogenic sulfur, higher sulfate production yield (320 mM), lower pH-value (pH = 0.56) and complete sulfur oxidation within 14 days was observed when compared to commercial sulfur. Application of a more concentrated biogenic acid (pH = 0.22) led to more effective and complete (∼100%) aluminium bioleaching up to 7.5% (w/v) blister waste within 7–9 days of incubation compared to 83% and 63% chemical leaching efficiency of transparent and white blisters using commercial sulfuric acid at the same pH, respectively. In addition, the plastic fraction after bioleaching was characterized and tested regarding re-processability. Results showed that sulfur from a biological origin can be oxidized faster by bacteria and biogenic acid is more effective in aluminium bioleaching compared to commercial sulfuric acid. Furthermore, results indicated that the plastic material is suitable for re-processing making this process an economically and environmentally friendly treatment option.

Taurine as a key intermediate for host-symbiont interaction in the tropical sponge Ianthella basta

Marine sponges are critical components of marine benthic fauna assemblages, where their filter-feeding and reef-building capabilities provide bentho-pelagic coupling and crucial habitat. As potentially the oldest representation of a metazoan-microbe symbiosis, they also harbor dense, diverse, and species-specific communities of microbes, which are increasingly recognized for their contributions to dissolved organic matter (DOM) processing. Recent omics-based studies of marine sponge microbiomes have proposed numerous pathways of dissolved metabolite exchange between the host and symbionts within the context of the surrounding environment, but few studies have sought to experimentally interrogate these pathways. By using a combination of metaproteogenomics and laboratory incubations coupled with isotope-based functional assays, we showed that the dominant gammaproteobacterial symbiont, ‘Candidatus Taurinisymbion ianthellae’, residing in the marine sponge, Ianthella basta, expresses a pathway for the import and dissimilation of taurine, a ubiquitously occurring sulfonate metabolite in marine sponges. ‘Candidatus Taurinisymbion ianthellae’ incorporates taurine-derived carbon and nitrogen while, at the same time, oxidizing the dissimilated sulfite into sulfate for export. Furthermore, we found that taurine-derived ammonia is exported by the symbiont for immediate oxidation by the dominant ammonia-oxidizing thaumarchaeal symbiont, ‘Candidatus Nitrosospongia ianthellae’. Metaproteogenomic analyses also suggest that ‘Candidatus Taurinisymbion ianthellae’ imports DMSP and possesses both pathways for DMSP demethylation and cleavage, enabling it to use this compound as a carbon and sulfur source for biomass, as well as for energy conservation. These results highlight the important role of biogenic sulfur compounds in the interplay between Ianthella basta and its microbial symbionts.

Light stress induced DMS(P) production in Skeletonema costatum: An experimental approach and field observation

Dimethylsulphide is a dominant biogenic sulphur anti-greenhouse gas produced by marine phytoplankton. A non-axenic culture of Skeletonema costatum was studied to comprehend the effects of different growth stages and light stress on DMSP/DMS production. The intracellular DMSP concentration increased during late exponential to mid-stationary phase and attained a maximum (0.59 pg S cell−1) during the stationary phase, indicating more contribution from actively dividing smaller cells. Likewise, exposure to first light after a 12-hour dark phase caused stress, invariably leading to elevated levels of DMS (~9 fold). These observations were upheld by additional laboratory and field experiments, and a field time-series observation, which recorded higher DMS concentrations during exposure to first light after a dark cycle and during early mornings, respectively. While our study depicts the variable DMSP and DMS concentrations during different growth stages of S. costatum, it gives new information on the effect of light stress on DMS production.

Machine learning for prediction of daily sea surface dimethylsulfide concentration and emission flux over the North Atlantic Ocean (1998–2021)

As the most ubiquitous natural source of sulfur in the atmosphere, dimethylsulfide (DMS) promotes aerosol formation in marine environments, impacting cloud radiative forcing and precipitation, eventually influencing regional and global climate. In this study, we propose a machine learning predictive algorithm based on Gaussian process regression (GPR) to model the distribution of daily DMS concentrations in the North Atlantic waters over 24 years (1998–2021) at 0.25° × 0.25° spatial resolution. The model was built using DMS observations from cruises, combined with satellite-derived oceanographic data and Copernicus-modelled data. Further comparison was made with the previously employed machine learning methods (i.e., artificial neural network and random forest regression) and the existing empirical DMS algorithms. The proposed GPR outperforms the other methods for predicting DMS, displaying the highest coefficient of determination (R2) value of 0.71 and the least root mean square error (RMSE) of 0.21. Notably, DMS regional patterns are associated with the spatial distribution of phytoplankton biomass and the thickness of the ocean mixed layer, displaying high DMS concentrations above 50°N from June to August. The amplitude, onset, and duration of the DMS annual cycle vary significantly across different regions, as revealed by the k-means++ clustering. Based on the GPR model output, the sea-to-air flux in the North Atlantic from March to September is estimated to be 3.04 Tg S, roughly 44 % lower than the estimates based on extrapolations of in-situ data. The present study demonstrates the effectiveness of a novel method for estimating seawater DMS surface concentration at unprecedented space and time resolutions. As a result, we are able to capture high-frequency spatial and temporal patterns in DMS variability. Better predictions of DMS concentration and derived sea-to-air flux will improve the modeling of biogenic sulfur aerosol concentrations in the atmosphere and reduce aerosol-cloud interaction uncertainties in climate models.

Effects of atmospheric oxidation processes on the latitudinal distribution differences in MSA and nss-SO42- in the Northwest Pacific

Dimethyl sulfide (DMS) derived aerosols play an important role in the oceanic atmosphere. The methanesulfonic acid (MSA)/non-sea-salt sulfate (nss-SO42-) ratio is often used to determine the contribution of the DMS sulfate source. However, there is competition between the pathways of DMS to MSA and sulfate, and the importance of the differences in the reaction pathways for MSA/nss-SO42- remains unclear. Here, the MSA, nss-SO42-, and other environmental data from the Northwest Pacific Ocean in July and September were used to evaluate the impact of atmospheric oxidation processes on the ratio. In July, nss-SO42- was mostly contributed by anthropogenic sources, and in September, it was mostly produced mainly from DMS (biogenic sulfate [bio-SO42-]). Differences in sources explain most of the spatiotemporal distribution characterization of MSA and nss-SO42-. However, the atmospheric oxidation process was the main factor responsible for the difference in the spatial distribution of MSA and bio-SO42- in September. The air temperature, surface incoming shortwave flux, ozone and relative humidity affect atmospheric oxidation processes and thus the MSA/bio-SO42– ratio. Therefore, when nss-SO42- is mainly from the DMS source and the net primary production (NPP) is similar between sea areas, the MSA/nss-SO42- ratio needs to be used carefully to evaluate the sulfate contribution from the DMS source. In addition, it should be noted that the contribution of the DMS source aerosol to the Northwest Pacific is not negligible (up to 45%) with gentle wind and high NPP.

Insights into the Superior Bioavailability of Biogenic Sulfur from the View of Its Unique Properties: The Key Role of Trace Organic Substances.

Elemental sulfur (S0) is widely utilized in environmental pollution control, while its low bioavailability has become a bottleneck for S0-based biotechnologies. Biogenic sulfur (bio-S0) has been demonstrated to have superior bioavailability, while little is known about its mechanisms thus far. This study investigated the bioavailability and relevant properties of bio-S0 based on the denitrifying activity of Thiobacillus denitrificans with chemical sulfur (chem-S0) as the control. It was found that the conversion rate and removal efficiency of nitrate in the bio-S0 system were 2.23 and 2.04 times those of the chem-S0 system. Bio-S0 was not pure orthorhombic sulfur [S: 96.88 ± 0.25% (w/w)]. Trace organic substances detected on the bio-S0 surface were revealed to contribute to its hydrophilicity, resulting in better dispersibility in the aqueous liquid. In addition, the adhesion force of T. denitrificans on bio-S0 was 1.54 times that of chem-S0, endowing a higher bacterial adhesion efficiency on the sulfur particle. The weaker intermolecular binding force due to the low crystallinity of bio-S0 led to enhanced cellular uptake by attached bacteria. The mechanisms for the superior bioavailability of bio-S0 were further proposed. This study provides a comprehensive view of the superior bioavailability of bio-S0 and is beneficial to developing high-quality sulfur resources.

Climate Roles of Non-Sea Salt Sulfate and Sea Spray Aerosol in the Atmospheric Marine Boundary Layer: Highlights of 40 Years of PMEL Research

The Pacific Marine Environmental Laboratory (PMEL) began measurements of dimethylsulfide (DMS) in 1982 to better understand the seawater sulfur cycle and the contribution of seawater DMS emissions to the global atmospheric sulfur budget. These measurements led to a global ocean database of DMS seawater concentrations currently hosted at PMEL, with contributions from researchers worldwide. In the mid-1980s, PMEL followed DMS from the ocean into the atmosphere and began aerosol measurements. It was found that DMS-derived, biogenic sulfate can make up a large fraction of the submicron aerosol in the remote marine atmosphere. In addition, it was found that a significant and variable fraction of submicron aerosol over the ocean was composed not only of biogenic sulfate but also included sea spray aerosol and long-range transported components. These measurements were pioneering in providing evidence that marine aerosols are a complex mixture of chemical components that should be included in climate models in order to accurately model Earth’s radiation budget. Measurements from 27 cruises have helped form a coherent view of species responsible for aerosol light scattering and cloud drop nucleation in the marine boundary layer. This global database of aerosol properties is publicly available on PMEL web pages for use by the modeling and satellite communities. Most recently, PMEL has developed payloads for uncrewed aerial systems to extend surface shipboard measurements up to 3,000 m in altitude and to include measurements of cloud properties.

CMIP6 projections of ocean warming and the impact on dimethylsulfide emissions from the Great Barrier Reef, Australia

Coral reefs are important regional sources of biogenic sulfur to the tropical marine atmosphere, through stress-induced emissions of dimethylsulfide (DMS). Recent estimates suggest that the Great Barrier Reef (GBR), Australia emits 0.02-0.05 Tg yr-1 of DMS (equivalent to 0.010-0.026 Tg yr-1 S), with potential implications for local aerosol-cloud processes. However, the impact of ocean warming on DMS emissions from coral reefs remains uncertain, complicating efforts to improve the representation of coral reefs in DMS climatologies and climate models. We investigate the influence of predicted changes in sea surface temperature (SST), photosynthetically active radiation (PAR) and wind speed on contemporary DMS emissions from the GBR using model output from the Coupled Model Intercomparison Project Phase 6 (CMIP6). A multiple linear regression is used to calculate seawater surface DMS (DMSw) concentration in the GBR in a contemporary (2001-2020) and end-of-century (2081-2100) scenario, as simulated by CMIP6 models under a SSP2-4.5 and SSP5-8.5 Shared Socioeconomic Pathway. By the end of this century, a 1.5-3.0°C rise in annual mean SST and a 1.1-1.7 mol m-2 d-1 increase in PAR could increase DMSw concentration in the GBR by 9.2-14.5%, leading to an increase in DMS flux of 9.5-14.3%. Previous model studies have suggested that the aerosol system has a low sensitivity to relatively large changes in coral reef-derived DMS. Therefore, the predicted change in contemporary DMS emissions is unlikely to influence the regional atmosphere. Further research is needed to understand the combined effects of temperature, light, pH, salinity and ecosystem structure on DMS production in coral reefs to better predict potential changes in emissions. Nevertheless, the findings provide insight into how predicted ocean warming may affect present-day DMS emissions and the source-strength of the GBR to the atmospheric sulfur budget.