Dimethyl Sulfide Research Articles

Responses of biogenic dimethylated sulfur compounds to environmental changes in the northwestern Pacific continental sea

AbstractContinental seas are facing rapid environmental shifts, but how biogenic dimethylated sulfur compounds, including dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO), will respond to these environmental changes remains poorly understood. Here we investigated the effects of nutrient input, ocean acidification, and dust deposition on the phytoplankton community and organic sulfur cycle in the East China Sea. Nutrient input promoted phytoplankton growth and increased the concentrations of DMS, DMSP, and DMSO. With sufficient nutrients, especially nitrate, the dissolved DMSP degradation was inhibited, and the bacterial DMSP‐cleavage pathway (inferred by dddP gene abundance) was enhanced, causing increased DMS production. The sensitivity of phytoplankton biomass and DMS to ocean acidification varied with different initial nutrient levels, demonstrating insensitivity under eutrophic conditions and negative responses under nutrient‐limited conditions. The ocean acidification promoted the dissolved DMSP degradation and bacterial DMSP‐demethylation pathway (inferred by dmdA gene abundance) and weakened the DMS production, causing the decreases of DMS and DMSP. The nutrient from dust deposition (2 mg L−1) was identified as the key factor in enhancing phytoplankton biomass and the organic sulfur compounds concentrations, but trace metals input from dust deposition had no significant effect. This study has identified environmental drivers and suppressors of phytoplankton and biogenic dimethylated sulfur compounds in a changing marine environment, which will enable the effective modeling of future climate change.

Emissions and uptake of volatiles by sampling components in breath analysis

The first and most crucial step in breath research is adequate sampling, which plays a pivotal role in quality assurance of breath datasets. In particular, the emissions or uptake of volatile organic compounds (VOCs) by sampling interface materials present a risk of disrupting breath gas samples. This study investigated emissions and uptake by three interface components, namely a silicon facemask, a reusable 3D-printed mouthpiece adapter, and a pulmonary function test filter compatible with the commercial Respiration Collector for In-Vitro Analysis (ReCIVA) breath sampling device. Emissions were examined before and after (hydro-)thermal treatment of the components, and uptake was assessed by exposing each material to 12 representative breath VOCs comprising alcohols, aldehydes, ketones, carboxylic acids, terpenes, sulphurous and nitrogenous compounds at different target concentration ranges (∼10 ppbV and ∼100 ppbV). Chemical analyses of VOCs were performed using proton transfer reaction-time-of-flight-mass spectrometry (PTR-TOFMS) with supporting analyses via thermal desorption comprehensive two-dimensional gas chromatography-TOFMS (TD-GC×GC-TOFMS). The filter exhibited the lowest overall emissions compared to the mask or adapter, which both had equivalently high emissions (albeit for different compounds). Treatment of the materials reduced the total VOC emissions by 62% in the mask, 89% in the filter and 99% in the adapter. Uptakes of compounds were lowest for the adapter and most pronounced in the mask. In particular, 1-butanol, acetone, 2-butanone, 1,8-cineole and dimethyl sulphide showed negligible uptake across all materials, whereas ethanol, nonanal, acetic acid, butanoic acid, limonene and indole exhibited marked losses. Knowledge of emissions and/or uptake by sampling components is key to reducing the likelihood of erroneous data interpretation, ultimately expediting progress in the field of breath test development.

A DFT Study on Single Brønsted Acid Sites in Zeolite Beta and Their Interaction with Probe Molecules

Zeolites are subjects of intensive research, as they have vast industrial applications. However, exact nature of catalytic active sites remains elusive. With this research, we attempt to shed light on the Brønsted acid sites in zeolite beta modification A and correlate the widely used TPD methods of their identification with the theoretically determined strongest and weakest acid sites. A diverse set of probe molecules with a wide range of acid strength of their conjugated acids is applied to determine the heats of their adsorption over protonated zeolite beta samples. The molecules studied were acetonitrile, dimethyl sulfide, dimethyl sulfoxide, isothiazole, pyridine, tetrahydrofuran, and ammonia. It was found that the heat of adsorption of the probe molecules correlated with the acid strength of acid sites only partially. Only some of the strong acid sites were able to be identified, while the weakest acid site was often identified correctly. To conclude, the widely used method of zeolites acid sites studies delivers only partially correct results, and the conclusions from such TPD studies should be treated with caution.

Link between Flavor Perception and Volatile Compound Composition of Dark Chocolates Derived from Trinitario Cocoa Beans from Dominican Republic.

The chemical composition of dark chocolate has a significant impact on its complex flavor profile. This study aims to investigate the relationship between the volatile chemical composition and perceived flavor of 54 dark chocolate samples made from Trinitario cocoa beans from the Dominican Republic. The samples were evaluated by a trained panel and analyzed using gas chromatography-mass spectrometry (GC-MS) to identify and quantify the volatile compounds. Predictive models based on a partial least squares regression (PLS) allowed the identification of key compounds for predicting individual sensory attributes. The models were most successful in classifying samples based on the intensity of bitterness and astringency, even though these attributes are mostly linked to non-volatile compounds. Acetaldehyde, dimethyl sulfide, and 2,3-butanediol were found to be key predictors for various sensory attributes, while propylene glycol diacetate was identified as a possible marker for red fruit aroma. The study highlights the potential of using volatile compounds to accurately predict chocolate flavor potential.

Analysis of Trace Volatile Compounds Emitted from Flat Ground and Formed Bed Anaerobic Soil Disinfestation in Strawberry Field Trials on California’s Central Coast

Anaerobic soil disinfestation (ASD) is emerging globally as an alternative to fumigant pesticides. To investigate ASD mechanisms, we monitored microbially produced volatile organic compounds (VOCs) and other volatile gases in situ using Fourier Transform Infrared Spectroscopy. Study plots infested with Fusarium oxysporum, Macrophomina phaseolina, and/or Verticillium dahliae included: organic flat ground (fASD, 6.7 + 13.5 megagrams per hectare, Mg/ha, rice bran/broccoli) and uncovered soil treated with mustard seed meal (MSM, 3.4 Mg/ha) at one site performed in fall of 2018; formed bed (bASD, 20 Mg/harice bran), control (UTC) and fumigant (FUM) at a second field site in fall of 2019 and 2021. Here, we present VOC diversity and temporal distribution. fASD generated 39 VOCs and GHGS, including known pathogen suppressors: dimethyl sulfide, dimethyl disulfide, and n-butylamine. bASD produced 17 VOCs and greenhouses gases (GHGs), 12 of which were also detected in fASD but in greater concentrations. Plant mortality and wilt score (fASD: 3.75% ± 4.79%, 2.8 ± 0.8; MSM: 6.25% ± 12.50%, 2.7 ± 0.3; bASD: 61.27% ± 11.26%, 4.1 ± 0.5; FUM: 13.89% ± 7.17%, 2.3 ± 0.2; UTC: 76.63% ± 25.11%, 4.3 ± 1.0) were significantly lower for fASD and MSM versus bASD and UTC (p < 0.05). Only FUM was not statistically different from fASD and MSM, and was significantly lower than UTC and bASD (bASD-FUM, p < 0.05; UTC-FUM, p < 0.05). The cumulative strawberry yield from bASD-treated plots was not different from FUM or UTC (bASD: 60.3 ± 13.6; FUM: 79.4 ± 9.19; UTC: 42.9 ± 12.4 Mg/ha). FUM yield was significantly greater than UTC (p = 0.005). These results, and to a far greater extent, additional challenges faced during both bASD trials, suggest that bASD is not as effective or as feasible at maintaining overall plant health as fASD or traditional fumigants. However, differences in management practices and environmental conditions at both sites across years cannot be fully excluded from consideration and many of our observations remain qualitative in nature.

Dimethyl Sulfide (DMS) in Amarone Wines: Influence of Aging, Withering, Grape Variety, and Geographical Origin.

Occurrence of dimethyl sulfide (DMS), a potent aroma compound accumulating during aging, was investigated in commercial and experimental Amarone wines. In commercial Amarone, DMS was observed in concentrations ranging from 2.9 to 64.3 μg/L. Model aging studies on experimental wines indicated that DMS in Amarone is strongly associated with aging and that wines from different vineyards can vary significantly in their ability to accumulate DMS during aging. The capacity of certain vineyards to give wines with higher DMS-forming potential was consistent across three consecutive vintages, representing a true terroir factor to be expressed with aging. Wine content of primary amino acids (PAN), a commonly analyzed enological parameter of grape must, was shown to be positively correlated with DMS accumulation during aging. Grape withering also increased DMS-forming potential mostly due to increased PAN resulting from concentration due to water loss. Increased pH due to withering also contributed to a higher DMS content of withered wines, but to a lower extent. In certain vineyard sites, an influence of vintage conditions on DMS-forming potential was also observed.

Effect of cobalt modification onto a Beta zeolite for the direct catalytic decomposition of dimethyl sulfide

For the development of small-scale desulfurization processes such as fuel cell systems, catalytic decomposition of dimethyl sulfide (DMS) to H2S without H2 addition was investigated using a Co/H-Beta zeolitic catalyst, with its acidity controlled via post-synthesis modification. The protonated zeolite (H-Beta) exhibited little catalytic activity at 400 °C, but Co modification significantly promoted DMS decomposition, with a high H2S yield of 50% observed. The optimum Co amount was equivalent to half of the ion-exchange capacity of the original H-Beta zeolite. While the Co/SiO2 did not display catalytic activity, and thus, the coexistence of acid and Co ion sites is necessary in DMS decomposition. The Co species were introduced at the cation sites of the zeolite, suppressing Co sulfurization, which contributed to the high catalytic activity.

Ozone catalytic oxidation of dimethyl sulfide and surface analysis of iodine catalyst

This study reports on the ozone catalytic oxidation of dimethyl sulfide; a major odor material in wastewater facilities. A xenon excimer lamp (XEL) was used for ozone generation, and iodine compounds (I− and IO3 −) were utilized as a catalyst. The three types of activated carbon tested as catalysts were: activated carbon impregnated with iodine compounds and sulfate (AC-I/S), activated carbon impregnated with iodine (AC-I) and activated carbon without impregnation (AC). Only AC-I/S had catalytic activity in the dynamic adsorption experiment. The breakthrough time of dimethyl sulfide increased by 10 times upon adding ozone to the AC-I/S. Catalyst characterization by pH measurement and XPS analysis suggested that the catalytic activity of iodine compounds was influenced by the surface acidity. These results suggest that the XEL and AC-I/S are applicable for ozone catalytic oxidation in gas treatments.

Oxidation State Tuning of Room Temperature Phosphorescence and Delayed Fluorescence in Phenothiazine and Phenothiazine-5,5-dioxide Dimers.

Heterocyclic dimers consisting of combinations of butterfly-shaped phenothiazine (PTZ) and its chemically oxidized form phenothiazine-5,5-dioxide (PTZ(SO2 )) have been synthesized. A twist is imposed across the dimers by ortho-substituents including methyl ethers, sulfides and sulfones. X-ray crystallography, cyclic voltammetry and optical spectroscopy, underpinned by computational studies, have been employed to study the interplay between the oxidation state, conformational restriction, and emission mechanisms including thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP). While the PTZ(SO2 ) dimers are simple fluorophores, the presence of PTZ induces triplet-mediated emission with a mixed PTZ-PTZ(SO2 ) dimer displaying concentration dependent hallmarks of both TADF and RTP.

Observations of biogenic volatile organic compounds over a mixed temperate forest during the summer to autumn transition

Abstract. The exchange of trace gases between the biosphere and the atmosphere is an important process that controls both chemical and physical properties of the atmosphere with implications for air quality and climate change. The terrestrial biosphere is a major source of reactive biogenic volatile organic compounds (BVOCs) that govern atmospheric concentrations of the hydroxy radical (OH) and ozone (O3) and control the formation and growth of secondary organic aerosol (SOA). Common simulations of BVOC surface–atmosphere exchange in chemical transport models use parameterizations derived from the growing season and do not consider potential changes in emissions during seasonal transitions. Here, we use observations of BVOCs over a mixed temperate forest in northern Wisconsin during broadleaf senescence to better understand the effects of the seasonal changes in canopy conditions (e.g., temperature, sunlight, leaf area, and leaf stage) on net BVOC exchange. The BVOCs investigated here include the terpenoids isoprene (C5H8), monoterpenes (MTs; C10H16), a monoterpene oxide (C10H16O), and sesquiterpenes (SQTs; C15H24), as well as a subset of other monoterpene oxides and dimethyl sulfide (DMS). During this period, MTs were primarily composed of α-pinene, β-pinene, and camphene, with α-pinene and camphene dominant during the first half of September and β-pinene thereafter. We observed enhanced MT and monoterpene oxide emissions following the onset of leaf senescence and suggest that senescence has the potential to be a significant control on late-season MT emissions in this ecosystem. We show that common parameterizations of BVOC emissions cannot reproduce the fluxes of MT, C10H16O, and SQT during the onset and continuation of senescence but can correctly simulate isoprene flux. We also describe the impact of the MT emission enhancement on the potential to form highly oxygenated organic molecules (HOMs). The calculated production rates of HOMs and H2SO4, constrained by terpene and DMS concentrations, suggest that biogenic aerosol formation and growth in this region should be dominated by secondary organics rather than sulfate. Further, we show that models using parameterized MT emissions likely underestimate HOM production, and thus aerosol growth and formation, during early autumn in this region. Further measurements of forest–atmosphere BVOC exchange during seasonal transitions as well as measurements of DMS in temperate regions are needed to effectively predict the effects of canopy changes on reactive carbon cycling and aerosol production.

Volatile Organic Compounds Released by Oxyrrhis marina Grazing on Isochrysis galbana

A range of volatile organic compounds (VOCs) have been found to be released during zooplankton grazing on microalgae cultivated for commercial purposes. However, production of grazing-derived VOCs from environmentally relevant species and their potential contribution to oceanic emissions to the atmosphere remains largely unexplored. Here, we aimed to qualitatively explore the suite of VOCs produced due to grazing using laboratory cultures of the marine microalga Isochrysis galbana and the herbivorous heterotrophic dinoflagellate Oxyrrhis marina with and without antibiotic treatment. The VOCs were measured using a Vocus proton-transfer-reaction time-of-flight mass spectrometer, coupled to a segmented flow coil equilibrator. We found alternative increases of dimethyl sulfide by up to 0.2 nmol dm−3 and methanethiol by up to 10 pmol dm−3 depending on the presence or absence of bacteria regulated by antibiotic treatment. Additionally, toluene and xylene increased by about 30 pmol dm−3 and 10 pmol dm−3, respectively during grazing only, supporting a biological source for these compounds. Overall, our results highlight that VOCs beyond dimethyl sulfide are released due to grazing, and prompt further quantification of this source in budgets and process-based understanding of VOC cycling in the surface ocean.

Sensomics-Assisted Characterization of Key Flowery Aroma Compounds in Lu’an Guapian Green Tea Infusion (Camellia sinensis)

The volatile fraction was isolated from the premium and common grade of Lu'an Guapian green tea infusion by solvent-assisted flavor evaporation distillation. With the application of aroma extract dilution analysis, a total of 52 aroma-active compounds were revealed in the flavor dilution (FD) factor area of 32-8192. Besides, five additional odorants with higher volatility were identified using solid-phase microextraction. The aroma profiles, FD factors, and quantitative data of premium Guapian (PGP) and common Guapian (CGP) showed apparent differences. The intensity of the flowery attribute was significantly higher in PGP than in CGP, while cooked vegetable-like was the most outstanding odor note in CGP. The recombination experiment and the omission test of PGP clarified that dimethyl sulfide, (E,E)-2,4-heptadienal, (E)-β-ionone, (E,Z)-2,6-nonadienal, 2-methylbutanal, indole, 6-methyl-5-hepten-2-one, hexanal, 3-methylbutanal, γ-hexalactone, methyl epijasmonate, linalool, geraniol, and (Z)-3-hexen-1-ol were the key odorants of PGP tea infusion. The omission and addition tests of flowery odorants manifested that (E)-β-ionone, geraniol, and (E,E)-2,4-heptadienal, with higher odor activity values in PGP than in CGP, contributed to the flowery attribute most. The difference in the concentration of the abovementioned odorants with flowery odor notes could be one of the main factors which led to the difference in aroma quality between the two grades of Lu'an Guapian.

The effect of drying, cell disruption and storage on the sensory properties of Nannochloropsis sp.

Adding microalgae into food could strongly influence the flavor of the final product which is the key factor for consumer acceptation. To assist food processors in the development of tasteful food products containing microalgae, it is necessary to understand the impact of processing and storage on the flavor of freshly harvested microalgae biomass. In this study, the effect of commonly used drying techniques (freeze-drying, spray drying and thin-layer oven drying) and cell disruption (high pressure homogenization) on the sensory quality of fresh Nannochloropsis sp. biomass was investigated. Furthermore, the impact of storage on the flavor properties of intact (non-disrupted) and disrupted Nannochloropsis paste was examined. Sensory evaluation by a trained panel indicated that the flavor of Nannochloropsis was not affected by freeze-drying. Whereas thin-layer oven drying at 60 °C resulted in a strong bitter taste and a musty odor. This odor is positively correlated with volatile organic compounds (VOCs) including Strecker aldehydes that arise from the Strecker degradation in the course of the Maillard reaction. Spray drying reduced the odor intensity and grassy odor of Nannochloropsis which could be attributed to the loss of several VOCs including esters, saturated alcohols and dimethyl sulfide. Furthermore, cell disruption of Nannochloropsis using high pressure homogenization resulted in intense grassy and fish oil odors features due to high amounts of fatty acid-derived unsaturated aldehydes, ketones and alcohols. Finally, dark storage of fresh intact and disrupted Nannochloropsis paste at ambient temperature strongly impacts the volatile profile due to the rapid formation of several VOCs, which negatively impact the palatability of the Nannochloropsis biomass. Our results provide the basis to be applied in downstream food processing of harvested Nannochloropsis biomass in order to maintain or optimize the flavor properties for specific food products.

The Effect of Zooplankton on the Distributions of Dimethyl Sulfide and Dimethylsulfoniopropionate in the Bohai and Yellow Seas

AbstractDimethyl sulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) are ubiquitous sulfur compounds in the ocean. DMS is emitted into the atmosphere and has potential climatic effects. The distributions of DMS and DMSP are affected by various biological factors (i.e., bacterial catabolism and phytoplankton and zooplankton community composition). The horizontal and vertical distributions of DMSP, DMSP lyase activity (DLA), DMS, and the abundances of bacteria, DMSP‐consuming bacteria, dimethyl sulfoxide‐consuming bacteria, and picophytoplankton were investigated in the Bohai Sea (BS) and Yellow Sea (YS) during autumn 2020. DLA was significantly correlated with chlorophyll a, DMS, and dissolved DMSP concentrations. Our data show that bacteria Clade_I SAR11 was a significant contributor to DLA. A dilution experiment indicated that the highest microzooplankton grazing rate coincided with the highest DMS concentration and DMS production rate. A proportion of 16%–62% of the DMSPt was converted to DMS in the dilution experiment. Copepods dominated the mesozooplankton community. Calanus sinicus was the predominant copepod in the BS and YS. C. sinicus grazing stimulated DMS production. DMS concentration increased 299% after C. sinicus grazing on physically broken algal cells for 48 hr. These results will help with a better understanding of the control of DMS and DMSP concentrations by zooplankton and the DMS release mechanisms that occur through zooplankton grazing.

Examining the impact of dimethyl sulfide emissions on atmospheric sulfate over the continental U.S.

We examine the impact of dimethylsulfide (DMS) emissions on sulfate concentrations over the continental U.S. by using the Community Multiscale Air Quality (CMAQ) model version 5.4 and performing annual simulations without and with DMS emissions for 2018. DMS emissions enhance sulfate not only over seawater but also over land, although to a lesser extent. On an annual basis, the inclusion of DMS emissions increase sulfate concentrations by 36% over seawater and 9% over land. The largest impacts over land occur in California, Oregon, Washington, and Florida, where the annual mean sulfate concentrations increase by ~25%. The increase in sulfate causes a decrease in nitrate concentration due to limited ammonia concentration especially over seawater and an increase in ammonium concentration with a net effect of increased inorganic particles. The largest sulfate enhancement occurs near the surface (over seawater) and the enhancement decreases with altitude, diminishing to 10-20% at an altitude of ~5 km. Seasonally, the largest enhancement of sulfate over seawater occurs in summer, and the lowest in winter. In contrast, the largest enhancements over land occur in spring and fall due to higher wind speeds that can transport more sulfate from seawater into land.

Metabolic Changes during Sprouting of Rapeseed and Their Consequences for the Volatilome of Cold‐Pressed Oil

AbstractAll the procedures before pressing seeds have a great influence on the flavor of cold‐pressed rapeseed oil. However, the studies on the modification of aroma caused by inappropriate storage leading to sprouting are scarce. Therefore, this study aims to determine the effects of sprouting on the metabolome and volatilome of rapeseed cold‐pressed oil and press cakes. The presence of 56 and 21 nonvolatile metabolites is detected in seeds/press cakes and oil, respectively. Sprouting significantly affects the total contents of all groups of compounds, except sugars. At the same time, 375 volatile organic compounds (VOCs) are detected. The abundance of VOCs in sprouted oil is almost threefold higher compared to control oil, with the biggest contribution of sulfur‐containing compounds (dimethyl sulfide), glucosinolate derivatives (4‐isothiocyanato‐1‐butene), and aldehydes (3‐methylbutanal). A similar tendency is observed in press cake. Moreover, sprouting results in the biggest number of VOCs detected only in this oil (61). The abundance of aroma‐active compounds is much higher in sprouted products compared to corresponding controls, which has a confirmation in sensory analysis. This study shows that simultaneous volatilomics and metabolomics can be used to track the changes in the oil quality caused by the inappropriate storage of seeds. Sprouting leads to metabolic changes in seeds, which intensify the formation of new VOCs and consequently aroma of oils.Practical applications: The results of this study will help to understand the formation of volatile organic compounds (VOCs) during the processing and production of cold‐pressed rapeseed oil. The combination of VOCs with nonvolatile precursors can help to understand the pathways involved in VOCs formation. Moreover, the oil obtained from sprouted seeds is characterized by many VOCs not present in control oil, which can potentially be used to develop tools for quick evaluation if the seeds used for pressing initiated sprouting, which can lead to changes in its sensory quality.

Reaction of Atmospherically Relevant Sulfur-Centered Radicals with RO2 and HO2

The atmospheric oxidation of dimethyl sulfide and other emitted sulfur species leads to the formation of the methylthio radical, CH3S, which can be further oxidized to the CH3SO and CH3SO2 radicals. We investigated computationally the reactions of these three sulfur-centered radicals with the peroxy radicals ROO and HOO. Our results demonstrate that CH3S and CH3SO react with these peroxy radicals to form short-lived peroxide intermediates, which then decompose via a concerted O-O bond scission and S═O double bond formation that results in an increased valence of the sulfur atom. In contrast, CH3SO2 reacts to form stable CH3S(O)2OOR and CH3S(O)2OOH peroxide products, as sulfur is already at its highest valence. Multireference methods were used to describe these reactions in which the valence of the sulfur atom changes.

EMERGING TOOL FOR CONTROLLING POLLUTION : A REVIEW ARTICLE

The term "biotechnology" refers to the use of living organisms in man-made systems. Effluent treatment and fermentation both benefit from the employment of microorganisms. The widespread use of these methods could have a significant economic influence in fields including the development of novel pharmaceuticals, foods, and chemicals, the enhancement of agricultural goods, and the degradation of toxic wastes in substantial quantities. When it comes to cleaning the air in factories and cities of unpleasant odors and harmful chemicals, biotechnology provides the most cost-effective and eco-friendly solution. The environment and human health are both negatively impacted by the emission of volatile organic compounds (VOCs) and inorganic odorants. Odor-causing substances in the environment include ammonia, amines, hydrogen sulfide, methyl mercaptan, dimethyl sulfide. The need for air pollution control systems to provide peaceful, breathing air is developing as a result of rising population density and the construction of new residential areas and industrial units. This article offers a survey of the several biotechnological strategies now in use for reducing air pollution and unpleasant odors. Legal restrictions necessitate the elimination of odors and volatile organic compounds (VOCs) due to public complaints about poor air quality on-site and emission monitoring by enforcement agencies. Keywords- volatile organic compound (VOC), biotechnology, air pollution control. Cite this article- Akshita Tiwari, Shweta Sharma, Shweta Sharma, Parul Singh and Nupur Raghav, 2023 “Emerging Tool for Controlling Pollution: A Review Article” Journal of Science Innovations and Nature of Earth, Vol. 3(1), page- 52-58 www.doi.org/10.59436/https://jsiane.com/archives3/12/74

Evaluation of air quality simulation with a coupled atmosphere-ocean model: A case study on natural marine and biogenic emissions

In this study, a chemical transport model (i.e., Community Multi-scale Air Quality (CMAQ) modeling system with brute-force method (BFM)) was used in combination with atmosphere-ocean coupling to evaluate the impact of natural emissions (e.g., marine dimethyl sulfide (DMS), sea salt aerosol (SSA), and biogenic compounds) on the air quality of South Korea in the spring of 2019 (May 1–31). Overall, the coupled simulation results exhibited good agreement with the observations for meteorological fields and air quality (fine particulate matter (PM2.5) and ozone (O3)) compared to those obtained using the non-coupled simulation. The coupling effect in the study area tended to be strong in the presence of relatively strong winds (≥4 m s−1). The mean contributions of natural marine (DMS and SSA) and biogenic emissions to total PM2.5 mass reached ~8.2 % over the marine area and ~ 9.1 % over the land area, respectively. On average, biogenic emissions contributed 8.6 %, 29.3 % (and 27.3 %) to the concentrations of O3, secondary organic aerosol (SOA) (and organic carbon (OC)), respectively, over the land area. Isoprene and monoterpene contributed 40 % and 20 %, respectively, to biogenic SOA production over the land area and biogenic SOA accounted for 1.7 % and 7.8 % of the total O3 and PM2.5, respectively. Secondary aerosol formation was enhanced by gas-to-particle conversion processes due to the coupling effect. Therefore, this modeling study confirmed the non-negligible impact of natural emissions on the air quality in the study area. In addition, the study area is likely to be associated with VOC-limited conditions because of significantly enhanced photochemical O3 production owing to biogenic emissions.

Observational evidence linking ocean sulfur compounds to atmospheric dimethyl sulfide during Icelandic Sea phytoplankton blooms

In two Icelandic Sea spring blooms (May 2018 and 2019) in the North Atlantic Ocean (62.9–68.0°N, 9.0–28.0°W), chlorophyll-a and dimethylsulfoniopropionate (DMSP) concentrations and DMSP lyase activity (the DMSP-to-dimethyl sulfide (DMS) conversion efficiency) were measured at 67 stations, and the hourly atmospheric DMS mixing ratios were concurrently measured only in May 2019 at Storhofdi on Heimaey Island, located south of Iceland (63.4°N, 20.3°W). The ocean parameters for biology (i.e., chlorophyll-a, DMSP, and DMSP lyase activity) were broadly associated in distribution; however, the statistical significance of the association differed among four ocean domains and also between 2018 and 2019. Specifically, the widespread dominance of Phaeocystis, coccolithophores, and dinoflagellates (all rich in DMSP and high in DMSP lyase activity) across the study area is a compelling indication that variations in DMSP-rich phytoplankton were likely a main cause of the variations in statistical significance. For all the ocean domains defined here, we found that the DMS production capacity (calculated using the exposures of air masses to ocean biology prior to their arrivals at Heimaey and the atmospheric DMS mixing ratios of those air masses at Heimaey) was surprisingly consistent with in situ ocean S data (i.e., DMSP and DMSP lyase activity). Our study shows that the proposed computational approach enabled the detection of changes in DMS production and emission in association with changes in ocean primary producers.