Dimethyl Sulfide Research Articles

High-resolution distribution and emission of dimethyl sulfide and its relationship with pCO2 in the Northwest Pacific Ocean

Ocean-derived dimethyl sulfide (DMS) is widely concerning because of its hypothesized influence on global climate change. This study aims to explore the distribution characteristics and influencing factors of DMS and partial pressure of carbon dioxide (pCO2) in the Northwest Pacific Ocean, as well as the potential relationship between DMS and pCO2. A high-resolution, underway, shipboard measurement device was used to determine the DMS and pCO2 of the surface seawater and atmosphere in the Northwest Pacific and its marginal seas during November 2019. The result show that atmospheric and surface seawater DMS concentrations ranged from 3 to 125 pptv and 0.63 to 2.28 nmol L-1, respectively, with mean values of 46 ± 19 pptv and 1.08 ± 0.34 nmol L-1. The average sea surface pCO2 was 371 ± 16 μatm (range from 332 to 401 μatm). The trends in the surface seawater DMS in different current systems were primarily associated with phytoplankton abundance and composition. Biological activity and physical processes such as cooling jointly influenced the sea surface pCO2. A cold eddy along the transect in the Northwest Pacific Ocean increased DMS at the sea surface by 10% and CO2 uptake by 3%. We found a significant negative correlation between DMS and pCO2 in the Northwest Pacific Ocean at the 0.1° resolution [DMS]seawater = -0.0161[pCO2]seawater + 7.046 (R2 = 0.569, P < 0.01). The DMS and pCO2 sea-air fluxes were estimated to range from 0.04 to 25.3 μmol m-2·d-1 and from -27.0 to 4.22 mmol m-2·d-1 throughout the survey area. The Northwest Pacific Ocean, especially the Oyashio Current, is an important sink of CO2 and a source of DMS.

Microstructure and phase evolution behavior of SiZrBC ceramic precursors synthesized via sol–gel method

ZrB2–SiC ceramics were successfully prepared via sol–gel method using phenyltrichlorosilane, borane dimethyl sulfide, and zirconium tetrachloride in stoichiometric amounts as the raw materials. The macromolecular network structure formed after the sol–gel process was investigated via Fourier transform infrared (FT–IR) spectroscopy. The phase evolution of the ZrB2–SiC ceramics were analyzed by FT–IR spectroscopy, X–ray diffraction, and transmission electron microscopy, whereas morphological and elemental analyses were performed using scanning electron microscopy. In particular, the change in phase composition was monitored after the pyrolysis from 1400 to 1500 ​°C, and the heat treatment of BZ6 precursor at 1500 ​°C enabled one to produce the ZrB2–SiC ceramic with a homogeneous crystal phase distribution. Therefore, the controllable microstructure adjustment of the ceramic phase composition could be achieved and a new way was paved for the structural and functional applications of ultra–high–temperature ceramics (UHTCs) series.

Advanced investigation of a putative adsorption process of nine non key food odorants (non-KFOs) on the broadly tuned human olfactory receptor OR2W1: Statistical physics modeling and molecular docking study

In the present paper, statistical physics formalism was used to understand the olfactory perception via the investigation of dose-olfactory response curves of a putative adsorption process of nine non key food odorants (non-KFOs) on the broadly tuned human olfactory receptor OR2W1, in order to quantitative characterize the interactions between the nine studied non-KFOs, i. e., furfuryl sulfide, furfuryl disulfide, benzyl methyl disulfide, furfuryl methyl disulfide, benzyl methyl sulfide, 1-phenylethanethiol, benzyl mercaptan, furfuryl methyl sulfide and 3-phenylpropanol molecules and OR2W1 binding sites at a molecular level. Two advanced adsorption models have been proposed: the advanced monolayer monoenergy model (monolayer model with identical and independent olfactory receptor binding sites) (Model 1) and the advanced monolayer model with two independent types of olfactory receptor binding sites (Model 2). It was concluded that the monolayer monoenergy model was selected as the most adequate model to fit the experimental dose-olfactory response curves tabulated in literature. Actually, the numerical values of the three fitted physico-chemical parameters (RM1, n and C1) were obtained by a non-linear regression. Indeed, modeling results suggested that the number of docked non-KFOs per OR2W1 binding site n values (1.24 < n < 1.94) was always superior to 1, which indicated the non-parallel orientation of the studied odorants on the olfactory receptor and the multi-molecular adsorption mechanism. The estimated molar adsorption energy ΔEa values (ranged from 6.07 to 12.16 kJ/mol) for the nine olfactory systems confirmed the physical the exothermic characters of the adsorption process since ΔEa values were lower than 40 kJ/mol and positive. Furthermore, these estimated parameters were applied to characterize stereographically and energetically the interaction between the nine non-KFOs and OR2W1 through the determination of the human receptor binding site size distributions (RSDs) and the adsorption energy distributions (AEDs), which were spread out from 0.25 to 6.50 nm and from 0 to 22.50 kJ/mol, respectively. The docking computation between these nine non-KFOs and OR2W1 proved that the estimated binding affinities were belonged to the adsorption energies spectrum in general and the specific adsorption energy band or the molecular vibration modes limited spectrum (between 2.50 kJ/mol and 17 kJ/mol) (approximate olfactory band).

Wine Cork Closures Impacts on Dimethyl Sulfide (DMS) and Precursors (DMSP) Equilibrium of Different Shiraz Wines during Accelerated Bottle Ageing

Dimethyl sulfide (DMS) is a flavor compound, characteristic of the truffle aroma in red wines, and is well-known to be a fruity exhauster. DMS comes from the degradation of dimethyl sulfide potential (DMSP) during winemaking. Up to now, little is known about the role of the closure on the DMSP degradation during ageing. For that purpose, the effect of four micro-agglomerated wine cork closures was studied on the DMS/DMSP equilibrium, along with six other volatile sulfur compounds (VSC), was investigated in six Shiraz wines. After three months of accelerated bottle ageing, DMS levels increased significantly in all bottles. The most permeable closures induced a lesser accumulation of DMS, suggesting that DMS could be dependent on the redox status of the wine. At the same time, the DMSP decrease was proportional to the permeability of the closures. For the first time, a possible implication of closure permeability on DMSP degradation was observed.

New Insights into the Formation of CH3OCH3 and CH3SCH3 without and with the Assistance of Na+ Ions and Some Implications for Interstellar Chemistry: An In Silico Approach

As new facets of reaction chemistry are getting unraveled frequently, obtaining new insights and understanding the possible formation of the simplest ethers CH3OCH3 (dimethyl ether: DME) and CH3SCH3 (dimethyl sulfide: DMS) in DMS/DME chemistry are not well-studied so far and so are the description of the molecular reaction mechanisms by the structural evolution and sequence of bond breaking and bond formation. In this context, in silico studies have been accomplished using the density functional theory (DFT) and meta-hybrid-DFT approaches, and benchmarking compound methods. Theoretical investigations have been carried out along with a collective implementation of the potential energy surface (PES) (i.e., energy profile), rendering the energetics of the reaction, followed by the intrinsic reaction coordinate (IRC) approach. The PES examination acquired from the formation pathways of both species gives the impression that the construction of the DMS molecule appears to be energetically more favorable than that of the DME species. The role of the metal cation (here, the Na cation is chosen) in the chemistry occurring in the proposed reactions is not well-researched so far; herein, it is found that incorporation of an alkali metal cation (Na+) lowers the energy barrier significantly for both organic species and facilitates the molecular reactions. Out of five proposed reactions (without and with the assistance of the Na+ ion), the formation of DMS species for two reactions appeared to be the most feasible among all. The NCI plot and a few selected and important topological parameters analyzed from the quantum theory of atoms in molecules (QTAIM) tool are capable of recognizing the evolution of types, nature, and strength of interactions (H-bonding, NCIs, etc.), recuperating the bonding patterns along with the proceeding of the whole chemical process. Interestingly, as DMS is yet to be detected (or not known experimentally) in the interstellar medium (ISM), understanding theoretically the formation of DMS via possible reaction paths under the suitable/putative conditions in the ISM will be an interesting workout in future work.

Thermodynamic modeling of adsorption of dimethyl sulfide on raw and modified activated carbon by simplified local density model

The simplified local density (SLD) model was employed to analyze the experimental results of the adsorption of dimethyl sulfide (DMS) from a model fuel (n-hexane) on raw and modified walnut shell activated carbon (WSAC) with different impregnated amounts of silver ions (Ag-2, 4, 6, 8, and 10 mass percent). Modified Peng–Robinson equation of state was used in the liquid phase and the 6-12 Lenard Jones (LJ) potential function was implemented to represent the solid-fluid interactions. The LJ parameters for pure DMS and n-hexane were obtained from the Tsonopoulos correlation for the Second Virial coefficient data. Published experimental results of DMS and n-hexane adsorption were used for the physical properties and the molecular parameters needed in SLD model. Excess adsorption amounts of DMS were then calculated and compared with the experimental data. The average absolute deviations (AAD) between the experimental data and calculated results were 0.0072, 0.0727, 0.0377, 0.0601, 0.0605, and 0.0634 mmol/gr adsorbent for WSAC, WSAC-Ag-2, WSAC-Ag-4, WSAC-Ag-6, WSAC-Ag-8, and WSAC-Ag-10, respectively. For the same adsorbents the percent average absolute relative deviation (AARD%) were 14.11, 15.50, 7.70, 15.48, 16.16, and 29.09, respectively. The applicability of the SLD model in liquid-phase adsorption is validated.

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.

Variability of DMS in the East China Sea and its response to different ENSO categories

Dimethylsulfide (DMS) produced by marine phytoplankton is the most important volatile sulfur compound in ocean surface seawater and has a distinct contribution to global climate change. To assess DMS-climate feedbacks, the interannual variations in seawater DMS concentrations in the East China Sea (ECS) were examined, and their periodic characteristic patterns related to different El Niño-Southern Oscillation (ENSO) categories were discussed. Based on satellite surface seawater temperature (SST) and chlorophyll-a (Chl-a) datasets, a 23-year (1998–2020) dataset of DMS concentrations in the ECS was hindcasted by using a generalized additive mixed model (GAMM). The ENSO events from 1998 to 2020 were selected and divided into persistent, recession and transformed types according to their development process. The variability of surface seawater DMS concentration in the Yangtze River Estuary and its adjacent seas, the coast of Zhejiang and Fujian, and the coast of northern Jiangsu are more strongly influenced by ENSO events than the remainder of the ECS. Furthermore, ENSO alters the seasonal variability in DMS concentrations in the Yangtze River Estuary. The DMS concentrations of Apr-Jul were reduced (enhanced) by approximately 3.05 (0.61) nmol/L during Persistent El Niño (PEN) (Persistent La Niña (PLN)) events, which were reduced by approximately 0.51 and 1.10 nmol/L during recessionary El Niño (REN) event and recessionary La Niña (RLN) event, respectively. However, the DMS concentrations were enhanced by approximately 0.53 (1.29) nmol/L during El Niño-La Niña transition (ELT) (La Niña-El Niño transition (LET)) events. ENSO events affected the DMS concentrations in the surface seawater of the study area by influencing Chl-a and SST, where the short-period interannual variability (2–3 years) of DMS was mainly affected by SST, while the interannual variability of the long period (6 years) was mainly affected by Chl-a. The findings can be applied to the development of DMS concentration prediction methods.

Peculiarities of CH4 and CO2 Distribution in Sediments of the Arctic Seas

The distribution of the concentrations of CH4 and CO2 and other gases in the sediments of the Kara, Laptev and East Siberian seas was studied. A correlation was found between CH4 and CO2 in most sediment cores. The correlation coefficient R for the sediments of the Kara Sea ranges from 0.58 to 0.97 and does not depend on the gas distribution with depth. Methanogenesis in marine sediments is presumably associated with sulfate reduction, and hydrogenotrophic methanogenesis leads to an increase in CH4 concentration against the background of high CO2 concentration. The high concentration of dimethyl sulfide in the sediments indicates the simultaneous formation of CH4 and CO2 through methylotrophic methanogenesis with the participation of CH3SCH3. In the upper layers of the sediment, opposite trends in the CH4 and CO2 distribution can be observed. The fact that the correlation coefficients between CH4 and CO2 gases in the sediments of the Laptev Sea acquire both negative and positive values is probably related to the fact that gas formation processes in the upper layers of the sediment captured by short columns differ from those of deep layers.

The effect of high oxygen modified atmospheres on the quality degradation of packed live blue mussels (Mytilus edulis)

Oxygen (O2) plays a vital role in the blue mussel (Mytilus edulis) survival, microbial growth, and volatile organic compounds (VOCs) formation during transport and storage. This study measures the impact of different atmospheres (% CO2/O2/N2): 30/40/30; 40/60/0; and 0/60/40 on blue mussels' spoilage. Quality parameters were monitored at 4 °C for up to 16 days of storage, including headspace composition (% CO2/O2), pH, mortality, microbial analysis, and VOCs concentrations. Selected-ion flow-tube mass spectrometry (SIFT-MS) was used for real-time VOCs measurements. At the end of storage, odor activity values (OAVs) were calculated to assess VOCs that contributed to the overall odor profiles (OAV ≥1). Different atmospheres result in a different shelf life in which B60 condition (% CO2/O2/N2: 40/60/0) prolonged the life span of blue mussels for nine days of storage. A total of 23 compounds were identified in packed blue mussels. The evolution of ethanol; 3-methyl-1-butanol; 2,3-butanediol; acetone; 2,3-butanedione; dimethylamine (DMA); dimethyl sulfide; dimethyl disulfide; and methyl mercaptan were associated with mortality and total plate count (TPC >7 log CFU g−1). This study identifies dimethyl sulfide and methyl mercaptan as the primary contributors to malodor of blue mussels at the end of storage (OAVs = 182–66716).

Importance of Atmospheric Transport on Methanesulfonic Acid (MSA) Concentrations in the Arctic Ocean During Summer Under Global Warming

AbstractThe climatic effects of aerosols derived from dimethyl sulfide (DMS) (e.g., methanesulfonic acid [MSA]) have long been of concern, particularly in the rapidly warming Arctic Ocean. Melting sea ice and increase in primary productivity can result in increased DMS emissions and MSA. However, the processes affecting MSA are complex. In addition to local sources, atmospheric chemistry processes, deposition, long‐distance transport, and regional heterogeneities influence MSA. This study used aerosol samples from the Chinese Polar Research Expedition during the summer of 2010–2016 and divided them into the Chukchi Sea (CS), high Arctic Ocean (HAO), and sea near Greenland (NG) to study the factors that influence the changes in MSA. For CS, MSA concentrations were primarily influenced by long‐distance transport from the Bering Sea air mass. Moreover, owing to the North Atlantic Oscillation, an increase in the Bering Sea temperature and a decrease in rainfall during air mass transport led to a significant increase in the concentration of MSA in the CS in 2016. When the sea ice concentration was between 0.2 and 0.6, high solar radiation likely promoted MSA formation in the HAO. For NG, the sources, rainfall and atmospheric chemical processes influenced the variations in MSA. This study highlights the importance of MSA transport in the CS and sea ice for MSA in the HAO under global warming.

High Yield Autoclave Synthesis of pure M2B12H12 (M = Na, K)

Metal dodecaborates (MxB12H12) are a versatile class of materials used in polymer chemistry and cancer treatment and are promising candidates as electrolytes for solid-state batteries. However, a general and scalable approach has not yet been developed for producing high-purity B12H122- derivatives. In this work, we report a simple, efficient, and environmentally benign solvothermal method to prepare diffraction and 11B NMR pure Na2B12H12 (85% yield) and K2B12H12 (84% yield). This new synthetic approach is based on the use of the borane dimethyl sulfide complex (DMS·BH3) and borohydrides (NaBH4, KBH4) heated at different temperatures in diglyme in an autoclave. It was found that high-purity Na2B12H12·diglyme solvate is obtained via an intermediate formation of B3H8-, B9H14-, and B11H14-, which are all soluble in diglyme. Heating under vacuum is shown to be efficient for removing the coordinated diglyme, allowing the formation of unsolvated Na2B12H12. Autoclave synthesis starting from KBH4 directly yields solvent-free K2B12H12, and ball-milling KBH4 prior to the synthesis enabling us to significantly improve the final yield. The new synthetic method paves the way for large-scale synthesis of MxB12H12 derivatives, enabling to envisage a wider scope of practical applications.

Measurement report: Long-range transport and the fate of dimethyl sulfide oxidation products in the free troposphere derived from observations at the high-altitude research station Chacaltaya (5240 m a.s.l.) in the Bolivian Andes

Abstract. Dimethyl sulfide (DMS) is the primary natural contributor to the atmospheric sulfur burden. Observations concerning the fate of DMS oxidation products after long-range transport in the remote free troposphere are, however, sparse. Here we present quantitative chemical ionization mass spectrometric measurements of DMS and its oxidation products sulfuric acid (H2SO4), methanesulfonic acid (MSA), dimethylsulfoxide (DMSO), dimethylsulfone (DMSO2), methanesulfinic acid (MSIA), methyl thioformate (MTF), methanesulfenic acid (MSEA, CH3SOH), and a compound of the likely structure CH3S(O)2OOH in the gas phase, as well as measurements of the sulfate and methanesulfonate aerosol mass fractions. The measurements were performed at the Global Atmosphere Watch (GAW) station Chacaltaya in the Bolivian Andes located at 5240 m above sea level (a.s.l.). DMS and DMS oxidation products are brought to the Andean high-altitude station by Pacific air masses during the dry season after convective lifting over the remote Pacific ocean to 6000–8000 m a.s.l. and subsequent long-range transport in the free troposphere (FT). Most of the DMS reaching the station is already converted to the rather unreactive sulfur reservoirs DMSO2 in the gas phase and methanesulfonate (MS−) in the particle phase, which carried nearly equal amounts of sulfur to the station. The particulate sulfate at Chacaltaya is however dominated by regional volcanic emissions during the time of the measurement and not significantly affected by the marine air masses. In one of the FT events, even some DMS was observed next to reactive intermediates such as methyl thioformate, dimethylsulfoxide, and methanesulfinic acid. Also for this event, back trajectory calculations show that the air masses came from above the ocean (distance &gt;330 km) with no local surface contacts. This study demonstrates the potential impact of marine DMS emissions on the availability of sulfur-containing vapors in the remote free troposphere far away from the ocean.

Malformation in coccolithophores in low pH waters: evidences from the eastern Arabian Sea.

Oceanic calcifying plankton such as coccolithophores is expected to exhibit sensitivity to climate change stressors such as warming and acidification. Observational studies on coccolithophore communities along with carbonate chemistry provide important perceptions of possible adaptations of these organisms to ocean acidification. However, this phytoplankton group remains one of the least studied in the northern Indian Ocean. In 2017, the biogeochemistry group at the Council for Scientific and Industrial Research-National Institute of Oceanography (CSIR-NIO) initiated a coccolithophore monitoring study in the eastern Arabian Sea (EAS). Here, we document for the first time a detailed spatial and seasonal distribution of coccolithophores and their controlling factors from the EAS, which is a well-known source of CO2 to the atmosphere. To infer the seasonality, data collected at three transects (Goa, Mangalore, and Kochi) during the Southwest Monsoon (SWM) of 2018 was compared with that of the late SWM of 2017. Apart from this, the abundance of coccolithophores was studied at the Candolim Time Series (CaTS) transect, off Goa during the Northeast Monsoon (NEM). The most abundant coccolithophore species found in the study region was Gephyrocapsa oceanica. A high abundance of G. oceanica (1800 × 103cells L-1) was observed at the Mangalore transect during the late SWM despite experiencing low pH and can be linked to nitrogen availability. The high abundance of G. oceanica at Mangalore was associated with high dimethylsulphide (DMS). Particulate inorganic carbon (PIC) and scattering coefficient retrieved from satellites also indicated a high abundance of coccolithophores off Mangalore during the late SWM of 2017. Interestingly, G. oceanica showed malformation during the late SWM in low pH waters. Malformation in coccolithophores could have a far-reaching impact on the settling fluxes of organic matter and also on the emissions of climatically important gases such as DMS and CO2, thus influencing atmospheric chemistry. The satellite data for PIC in the EAS indicates a high abundance of coccolithophore in recent years, especially during the warm El Nino years (2015 and 2018). This warrants the need for a better assessment of the fate of coccolithophores in high-CO2 and warmer oceans.

Oceanographic controls on Southern Ocean dimethyl sulfide distributions revealed by machine learning algorithms

AbstractWe developed two machine learning models to map the Southern Ocean distribution of the climate‐active gas dimethyl sulfide (DMS) at 20 km resolution. Results obtained from ensembles of random forest regressions and artificial neural networks reproduce observed DMS distributions with significantly higher accuracy than traditional statistical techniques, and are less prone to biases and spatial distortions than existing interpolation‐based climatologies. Both models predict persistently low offshore DMS concentrations associated with the Antarctic circumpolar current, suggesting that wind‐driven overturning mixing is the dominant regional control on DMS distributions. In addition, 60% of the variance in DMS seasonality is explained by changes in mixed layer depth and sea surface temperature, with a significant correlation between DMS concentrations and sea‐ice cover in coastal waters. We further identify the tracer Si* (defined as ) as a potentially important predictor for regional DMS distributions in Southern Ocean waters. At finer scales, our models capture various oceanographic features, including eddies, hydrographic fronts and jets that appear to play a role in driving DMS variability. Our results yield an estimated Southern Ocean sea‐air DMS flux of 8.7 ± 2.1 Tg S integrated across the phytoplankton growing season (October to April), representing 30.8% of total global oceanic S emissions, and highlighting the region's importance to the marine sulfur cycle. Our work provides new insights into the drivers of spatial variability in Southern Ocean DMS concentrations and sea‐air fluxes, and their potential responses to future climate‐dependent changes.

Dimethyl sulfide cycling in the sea surface microlayer in the southwestern Pacific – Part 1: Enrichment potential determined using a novel sampler

Abstract. Elevated dimethyl sulfide (DMS) concentrations in the sea surface microlayer (SML) have been previously related to DMS air–sea flux anomalies in the southwestern Pacific. To further address this, DMS, its precursor dimethylsulfoniopropionate (DMSP), and ancillary variables were sampled in the SML and also subsurface water at 0.5 m depth (SSW) in different water masses east of New Zealand. Despite high phytoplankton biomass at some stations, the SML chlorophyll a enrichment factor (EF) was low (&lt; 1.06), and DMSP was enriched at one station with DMSP EF ranging from 0.81 to 1.25. DMS in the SML was determined using a novel gas-permeable tube technique which measured consistently higher concentrations than with the traditional glass plate technique; however, significant DMS enrichment was present at only one station, with the EF ranging from 0.40 to 1.22. SML DMSP and DMS were influenced by phytoplankton community composition, with correlations with dinoflagellate and Gymnodinium biomass, respectively. DMSP and DMS concentrations were also correlated between the SML and SSW, with the difference in ratio attributable to greater DMS loss to the atmosphere from the SML. In the absence of significant enrichment, DMS in the SML did not influence DMS emissions, with the calculated air–sea DMS flux of 2.28 to 11.0 µmol m−2 d−1 consistent with climatological estimates for the region. These results confirm previous regional observations that DMS is associated with dinoflagellate abundance but indicate that additional factors are required to support significant enrichment in the SML.

Analysis of volatile compounds and flavor fingerprint in hairtail (Trichiurus lepturus) during air-drying using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS).

In the present study, changes in volatile compounds during processing were analyzed using the headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), to investigate the generation of aroma in hairtails (Trichiurus lepturus) during air-drying. Physicochemical indices, such as moisture content and thiobarbituric acid reactive substances (TBARS), were also detected. Flavor fingerprints were studied and developed to distinguish the samples of fresh hairtails (0 day) from air-dried hairtails (2 and 4 days). A total of 75 volatile organic compounds (VOCs) were identified in hairtails, in which alcohols, aldehydes, ketones, and esters were the principal contributors to the formation of the overall flavor of hairtails during air-drying. Seven flavor compounds (ethanol, 3-methyl-1-butanol, 1-pentanol, hexanal, octanal, benzaldehyde, and 3-methylbutanal), two flavor compounds (acetoin and dimethyl sulfide), and eight flavor compounds (1-hexanol, 1-octen-3-ol, nonanal, heptanal, 2-heptanone, ethyl acetate, trimethylamine, and ammonia) were identified in 0, 2, and 4 air-dried hairtails as biomarkers, respectively. The results showed that HS-GC-IMS could detect VOCs in different air-dried hairtails rapidly and comprehensively.

Malodorous volatile organic compounds (MVOCs) formation after dewatering of wastewater sludge: Correlation with the extracellular polymeric substances (EPS) and microbial communities

Malodorous volatile organic compounds (MVOCs) are often the key odorants in determining sludge odor character and odor impact. However, the emission characterization and generation mechanisms of MVOCs from various dewatered sludge have not been sufficiently understood partly due to the diverse and complex composition and low concentration of odorants. In this study, waste activated sludge (WAS) was collected to examine the variation of MVOC emission from sludge after different dewatering treatment in lab-scale trials. The MVOCs were measured using the electronic nose (eNose), headspace gas chromatography-coupled ion mobility spectrometry (HS-GC-IMS), and headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC–MS). The results showed that centrifugation treatment promoted the generation of various odorous volatiles. The identified key odorants included dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), geosmin, and p-cresol according to their odor activity values (OAVs). The effects of the enhanced dewatering on volatile production were greater than thickening, however, the key odorants of dewatered sludge using gravity thickening varied more greatly than sludges from centrifuge thickening. The distribution of extracellular polymeric substances (EPS) and variation of microbial community showed correlations with the production of key odorants. Tryptophan-like substances in the inner layer of EPS (LB-EPS and TB-EPS) were better correlated with the key odorants. The bound EPS released by centrifugation may play the role of precursor for odorous microbial volatiles. According to the predicted functions of differential microbial genera, Desulfobulbus (Desulfobacterota), Gordonia (Actinobacteriota), and Hyphomicrobium (Proteobacteria) were associated with the production of DMS, DMDS, and DMTS, while Gordonia and Hyphomicrobium were related to p-cresol production.

Dual-Function Detoxifying Nanofabrics against Nerve Agent and Blistering Agent Simulants

The development of functional materials that can detoxify multiple chemical warfare agents (CWAs) at the same time is of great significance to cope with the uncertainty of CWA use in real-world situations. Although many catalysts capable of detoxifying CWAs have been reported, there is still a lack of effective means to integrate these catalytic-active materials on practical fibers/fabrics to achieve effective protection against coexistence of a variety of CWAs. In this work, by a combination of electrospinning and in situ solvothermal reaction, PAN@Zr(OH)4@MOF-808 nanofiber membranes were prepared for detoxification of both nerve agent and blistering agent simulants dimethyl 4-nitrophenyl phosphate (DMNP) and 2-chloroethyl ethyl sulfide (CEES). Under the catalytic effect of the MOF-808 component, DMNP hydrolysis with a half-life as short as 1.19 min was achieved. Meanwhile, an 89.3% CEES removal rate was obtained within 12 h by adsorption and catalysis of MOF-808 and Zr(OH)4 components at ambient conditions, respectively. PAN@Zr(OH)4@MOF-808 nanofiber membranes also showed a superior blocking effect on CEES compared to bare PAN and PAN@Zr(OH)4 nanofiber membranes. Simultaneous protection against DMNP and CEES showed effective inhibition of both simulants for at least 2 h. The preparation method also imparted intrinsically good interfacial adhesion between the components, contributing to the excellent recycling stability of PAN@Zr(OH)4@MOF-808 nanofiber membranes. Therefore, the prepared composite nanofabrics have great application potential, which provides a new idea for the construction of broad-spectrum protective detoxification materials.

Biogeochemical controls on climatically active gases and atmospheric sulfate aerosols in the western Pacific

The Pacific Ocean plays an important role in regulating the budget of climatically active gases and the burden of sulfate aerosols. Here, a field investigation was conducted to clarify the key processes and factors controlling climatically active gases, including dimethyl sulfide (DMS), carbonyl sulfide (OCS), carbon disulfide (CS2), and carbon dioxide (CO2), in both surface seawater and the lower atmosphere of the western Pacific. In addition, the relative contributions of different sources to atmospheric sulfate aerosols were quantitatively estimated, and their causes were explored. The maximum concentrations of DMS, OCS and CS2 and the minimum partial pressure of CO2 (pCO2) were observed in the Kuroshio-Oyashio Extension. Kuroshio-induced mesoscale eddies brought abundant nutrients and organic matter from the subsurface layer of Oyashio into the euphotic layer, thus enhancing primary productivity and accelerating the photoreaction of organic matter. These processes led to higher concentrations of DMS, OCS and CS2 and lower pCO2. However, the oligotrophic subsurface layer in the subtropical gyre and the strong barrier layer in the equatorial waters suppressed the upward fluxes of nutrients and organic matter, resulting in lower surface concentrations of DMS, OCS, and CS2 in these areas. Being far from the continents, atmospheric concentrations of DMS, OCS and CS2 and pCO2 in the western Pacific generally were observed to depend on the local sea-to-air exchange and may be regulated by atmospheric oxidation and mixing of air masses. In general, oceanic DMS emissions played an important role in the formation of sulfate aerosols in the western Pacific (accounting for ∼19.5% of total sulfate aerosols), especially in the Kuroshio-Oyashio Extension (∼32.3%). These processes in seawater may also determine the variations and emissions of other climatically active gases from biogenic and photochemical sources.