Important Volatile Organic Compounds Research Articles

Multi-generation oxidation mechanism of M-xylene: Unexpected implications for secondary organic aerosol formation

Secondary organic aerosol (SOA) affects air quality, human health and climate. The multi-generation reactions of volatile organic compounds (VOCs) have become key process for explaining the SOA formation. M-xylene, as one of the most important VOCs in urban atmosphere, has got extensive study. However, the reaction mechanism of the first-generation products hydroperoxides (M-ROOH) and organonitrates (M-RONO2) remain unknown. In this work, the hydroxyl radicals (·OH) initiated reactions of M-ROOH and M-RONO2 were investigated by employing quantum chemical methods and kinetics modeling. The results show that new ring-retaining epoxides, a range of dialdehydes and less volatile hydroperoxides and organonitrates are formed, contributing to SOA formation. By adopting the unveiled new mechanism into the SOSAA box modeling, we found that the yield of SOA from m-xylene oxidation is up to 38%, which is comparable to the experimental value (36%). This work advances current understanding of multi-generation chemistry and elucidates the role of aromatic hydrocarbons oxidation in the formation of SOA.

Single and mixed effects of multiple volatile organic compounds exposure on hematological parameters in the U.S. adult population

BackgroundMost research exploring the correlation between volatile organic compounds (VOCs) and hematological parameters have focused on single VOCs. Our study aimed to explore the single and combined effects of VOCs on hematological parameters through three statistical models. MethodsData from 4 cycles of the National Health and Nutrition Examination Survey (NHANES) were used in this study. The correlations between single exposure to 16 VOCs and hematological parameters in the general population were assessed by weighted multiple linear regression. Weighted quantile sum (WQS) and Bayesian kernel machine regression (BKMR) models were used to explore the relationship between the combined important VOCs selected by the least absolute shrinkage and selection operator (LASSO) and hematological parameters, as well as the effects of smoking status on them. ResultsA total of 4089 adults were included in the study. We found that a variety of VOCs were significantly associated with hematological parameters. Among them, N-acetyl-S-(benzyl)-l-cysteine (BMA) was significantly negatively correlated with white blood cell (WBC), red blood cell (RBC), lymphocyte, and neutrophil counts. N-acetyl-S-(3-hydroxypropyl-1-methyl)-l-cysteine (HPMMA) was significantly positively correlated with WBC, monocyte, lymphocyte, and neutrophil counts. In the WQS analysis, the WQS index of the VOCs mixtures was positively correlated with WBC (β: 0.031; P < 0.001), monocyte (0.023; P = 0.021), and neutrophil (0.040; P = 0.001) counts, while negatively associated with RBC (−0.013; P < 0.001) counts. The BKMR model revealed that combined exposure to VOCs levels ≥70th percentile was significantly associated with lower RBC counts, and BMA was identified as the dominant contributor. Smoking significantly influenced the relationship between VOCs and hematological parameters. ConclusionsOur study indicated the effects of single and overall VOCs exposure on hematological parameters and suggested the hematotoxicity as well as pro-inflammatory effects of VOCs, which had strong public health implications for reducing the potential health hazards of VOCs exposure to the hematologic system.

Multivariate analysis of carcinogenic equivalence (CEQ) to characterize carcinogenic VOC emissions in a typical petrochemical industrial park in Taiwan

Large industrial emissions of volatile organic compounds (VOCs) from the petrochemical industry are a critical concern due to their potential carcinogenicity. VOC emissions vary in composition depending on the source and occur in mixtures containing compounds with varying degrees of toxicity. We proposed the use of carcinogenic equivalence (CEQ) and multivariate analysis to identify the major contributors to the carcinogenicity of VOC emissions. This method weights the carcinogenicity of each VOC by using a ratio of its cancer slope factor to that of benzene, providing a carcinogenic equivalence factor (CEF) for each VOC. We strategically selected a petrochemical industrial park in southern Taiwan that embodies the industry's comprehensive nature and serves as a representative example. The CEQs of different emission sources in three years were analyzed and assessed using principal component analysis (PCA) to characterize the major contributing sectors, vendors, sources, and species for the carcinogenicity of VOC emissions. Results showed that while the study site exhibited a 20.7 % (259.8 t) decrease in total VOC emissions in three years, the total CEQ emission only decreased by 4.5 % (15.9 t), highlighting a potential shift in the emitted VOC composition towards more carcinogenic compounds. By calculating CEQ followed by PCA, the important carcinogenic VOC emission sources and key compounds were identified. More importantly, the study compared three approaches: CEQ followed by PCA, PCA followed by CEQ, and PCA only. While the latter two methods prioritized sources based on emission quantities, potentially overlooking less abundant but highly carcinogenic compounds, the CEQ-first approach effectively identified vendors and sources with the most concerning cancer risks. This distinction underscores the importance of selecting the appropriate analysis method based on the desired focus. Our study highlighted how prioritizing CEQ within the analysis framework empowered the development of precise control measures that address the most carcinogenic VOC sources.

High-solution emission characters and health risks of volatile organic compounds for sprayers in automobile repair industries.

The increasing automobile repair industries (ARIs) with spray facilities have become an important volatile organic compound (VOC) pollution source in China. However, the VOC health risk assessment for long-term exposure in ARIs has not been well characterized. In this study, though sampled VOCs from 51 typical ARIs in Beijing, the relationship between emission patterns, average daily exposure concentrations (EC), and health risks was comprehensively analyzed with the health assessment method. Results showed that concentrations of 117 VOCs from the samples ranged from 68.53 to 19863.32 μg·m-3, while the ARI operator's daily VOC inhalation EC was 11.24-1460.70 μg·m-3. The organic VOC (OVOC) concentration accounted for 73.16 ~ 94.52% in the solvent-based paint workshops, while aromatics were the main VOC component in water-based paint spraying (WPS) workshops, accounting for 70.08%, respectively. And the method of inhalation exposure health risk assessment was firstly used to evaluate carcinogenicity and non-carcinogenicity risk for sprayers in ARIs. The cumulative lifetime carcinogenic risk (LCR) for 24 sampled VOCs were within acceptable ranges, while the mean hazard index (HI) for 1 year with 44 sampled VOCs was over 1. Among them, ethyl alcohol had a high carcinogenic risk in both mixed water-based paint (MP) and solvent-based paint workshops. The mean HI associated with aromatics were 2.88E - 3 and 4.30E - 3 for 1 h in MP and WPS workshops. O-ethyl toluene and acetone are VOC components that need to be paid attention to in future paint raw materials and spraying operations. Our study will provide the important references for the standard of VOC occupational exposure health limits in ARIs.

Ultrathin Langmuir-Blodgett film of functionalized single-walled carbon nanotubes for enhanced acetone sensing

Acetone is one of the important volatile organic compounds which needs to be detected from the industrial effluent and as a bio-marker from breath of diabetic patients. Here, ultrathin Langmuir-Blodgett (LB) film of octadecylamine- functionalized single-walled carbon nanotubes (ODA-CNT) was formed on interdigitated gold electrodes and was employed for acetone vapor sensing using the impedance spectroscopy (IS) at room temperature. The LB film deposited in liquid-like phase of the Langmuir monolayer of ODA-CNT revealed aligned nanotubes. Being a reducing agent, acetone interacts readily with the CNTs through the transfer of electrons. Using IS, multiparameter were measured with respect to both frequency and acetone vapor concentration. Principal component analysis (PCA) of the IS data revealed capacitance as the most suitable parameter for acetone vapor sensing using the ODA-CNT film. A very low limit of detection (0.5 ppm) and a wide detectable concentration range (1–300 ppm) for acetone sensing using the LB film of ODA-CNT was obtained. The 2D calibration map revealed that the sensing performance of acetone using LB film was much better as compared to that of drop-cast film of ODA-CNT and LB film of pristine CNTs. The superior sensing performance of the LB film of ODA-CNT is attributed to the uniform and aligned nature of the nanotubes, leading to a coherent behavior due to interaction with the acetone molecules. This study shows the potential of LB films of ODA-CNT for sensitive and low level detection of acetone vapor at room temperature.

Unveiling the importance of VOCs from pesticides applicated in main crops for elevating ozone concentrations in China

Volatile organic compounds (VOCs) are considered as important precursors of ozone in the air, while the contribution of VOCs from pesticide application (PVOCs) to ozone production is unknown. Utilizing data from the Ministry of Agriculture and Rural Affairs of the People's Republic of China and ChinaCropPhen1km, this paper developed PVOC emission inventories with a resolution of 1 km for the main crops (rice, maize, and wheat) from 2012 to 2019 in China. The results revealed that pesticide application is an important VOC emission source in China. Specially, the PVOC emissions from the major grain-producing regions in June accounted for approximately 30% of the annual total PVOC emissions in the local regions. The simulation with the Weather Research and Forecasting Community Multiscale Air Quality model (WRF-CMAQ) indicated that the PVOC emissions increased the mean maximum daily 8-hour average (MDA8) ozone concentration across China by 2.5 ppb in June 2019. During the same period, PVOCs in the parts of North China Plain contributed 10% of the ozone formation. Under the comprehensive emission reduction scenario, it is anticipated that by 2025, the joint implementation of measures including reducing pesticide application, improving pesticide utilization efficiency and promoting solvent substitution will decrease PVOC emissions by 60% compared with 2019, thereby mitigating ozone pollution.

Quorum Sensing Regulates the Production of Methanethiol in Vibrio harveyi.

Methanethiol (MeSH) and dimethyl sulfide (DMS) are important volatile organic sulfur compounds involved in atmospheric chemistry and climate regulation. However, little is known about the metabolism of these compounds in the ubiquitous marine vibrios. Here, we investigated MeSH/DMS production and whether these processes were regulated by quorum-sensing (QS) systems in Vibrio harveyi BB120. V. harveyi BB120 exhibited strong MeSH production from methionine (Met) (465 nmol mg total protein-1) and weak DMS production from dimethylsulfoniopropionate (DMSP) cleavage. The homologs of MegL responsible for MeSH production from L-Met widely existed in vibrio genomes. Using BB120 and its nine QS mutants, we found that the MeSH production was regulated by HAI-1, AI-2 and CAI-1 QS pathways, as well as the luxO gene located in the center of this QS cascade. The regulation role of HAI-1 and AI-2 QS systems in MeSH production was further confirmed by applying quorum-quenching enzyme MomL and exogenous autoinducer AI-2. By contrast, the DMS production from DMSP cleavage showed no significant difference between BB120 and its QS mutants. Such QS-regulated MeSH production may help to remove excess Met that can be harmful for vibrio growth. These results emphasize the importance of QS systems and the MeSH production process in vibrios.

Comparative Evaluation of Volatile Organic Compounds in Two Bottle Gourd Accessions with Distinct Fruit Shapes.

Bottle gourd (Lagenaria siceraria L.) belongs to the cucurbit family and has a long history of cultivation in tropical and subtropical regions worldwide, both for food and medicine. Popularized by its unique fruit shapes, gourds are used to make ornaments and musical instruments. However, there is limited information on volatile organic compounds (VOCs) in the bottle gourd fruit. In the present study, we conducted a comparative analysis of VOCs profiled in two accessions (USVL5 and USVL10) with distinct fruit shapes: bottle and cylinder. While USVL5 only produced long cylinder fruits, USVL10 produced two fruit types, cylinder (USVL10CYN) and bottle (USVL10A and USVL10B). VOCs in each line were analyzed using headspace solid-phase microextraction-gas chromatography/mass spectrometry (HS-SPME-GC/MS). Aliphatic aldehydes and alcohols were the most abundant compounds found in these bottle gourd accessions. Based on the functional profile of the identified VOCs, our results reveal the suitability of our tested line (USVL10), enriched in functionally important VOCs such as hexanal (abundance = 381.07), nonanal (abundance = 9.85), 2-methoxy-2-methylpropane (abundance = 21.26) and D-limonene (abundance = 31.48). The VOCs profiling and functional analyses support the notion that the bottle gourd accession USVL10 can be a good candidate for its use in agriculture, the health care industry and domestic uses.

Dopant Site Engineering on 2D Co3O4 Enables Enhanced Toluene Oxidation in a Wide Temperature Range.

Development of cost-effective oxide catalysts holds the key to the removal of toluene, one of the most important volatile organic compounds. However, the catalysts follow varied working mechanisms at different reaction temperatures, posing a challenge to achieving efficient toluene removal over a wide temperature range. Here we report an agitation-assisted molten salt method, which achieves the rational doping on a two-dimensional Co3O4 catalyst and forms two different structures of active sites to enhance catalytic oxidation of toluene in specific temperature intervals, enabling a facile tandem design for working in a wide temperature range. Specifically, Co3O4 is doped with Cu at the octahedral site (Cu-Co3O4) and Zn at the tetrahedral site (Zn-Co3O4) to form CuOh-O-CoTe and ZnTe-O-CoOh structures on the surface, respectively. Mechanistic studies reveal the different working mechanisms of these two active sites toward remarkable performance enhancement at specific temperature intervals, and the improved performance derived from accelerated consumption of intermediates adsorbed on the catalyst surface. Taken together, Cu-Co3O4 and Zn-Co3O4 achieve excellent toluene purification performance over a wide temperature range. This work provides insights into the mechanism-oriented design of active sites at the atomic level.

Comparison of Gas–Particle Partitioning of Glyoxal and Methylglyoxal in the Summertime Atmosphere at the Foot and Top of Mount Hua

Glyoxal and methylglyoxal are important volatile organic compounds in the atmosphere. The gas–particle partitioning of these carbonyl compounds makes significant contributions to O3 formation. In this study, both the gas- and particle-phase glyoxal and methylglyoxal concentrations at the foot and top of Mount Hua were determined simultaneously. The results showed that the gaseous-phase glyoxal and methylglyoxal concentrations at the top were higher than those at the foot of the mountain. However, the concentrations for the particle phase showed the opposite trend. The average theoretical values of the gas–particle partitioning coefficients of the glyoxal and methylglyoxal concentrations (4.57 × 10−10 and 9.63 × 10−10 m3 μg−1, respectively) were lower than the observed values (3.79 × 10−3 and 6.79 × 10−3 m3 μg−1, respectively). The effective Henry’s law constants (eff.KH) of the glyoxal and methylglyoxal were in the order of 108 to 109 mol/kgH2O/atm, and they were lower at the foot than they were at the top. The particle/gas ratios (P/G ratios) of the glyoxal and methylglyoxal were 0.039 and 0.055, respectively, indicating more glyoxal and methylglyoxal existed in the gas phase. The factors influencing the partitioning coefficients of the glyoxal and methylglyoxal were positively correlated with the relative humidity (RH) and negatively correlated with the PM2.5 value. Moreover, the partitioning coefficient of the glyoxal and methylglyoxal was more significant at the top than at the foot of Mount Hua.

Variation in supplemental lighting quality influences key aroma volatiles in hydroponically grown 'Italian Large Leaf' basil.

The spectral quality of supplemental greenhouse lighting can directly influence aroma volatiles and secondary metabolic resource allocation (i.e., specific compounds and classes of compounds). Research is needed to determine species-specific secondary metabolic responses to supplemental lighting (SL) sources with an emphasis on variations in spectral quality. The primary objective of this experiment was to determine the impact of supplemental narrowband blue (B) and red (R) LED lighting ratios and discrete wavelengths on flavor volatiles in hydroponic basil (Ocimum basilicum var. Italian Large Leaf). A natural light (NL) control and different broadband lighting sources were also evaluated to establish the impact of adding discrete and broadband supplements to the ambient solar spectrum. Each SL treatment provided 8.64 mol.m-2.d-1 (100 µmol.m-2.s-1, 24 h.d-1) photon flux. The daily light integral (DLI) of the NL control averaged 11.75 mol.m-2.d-1 during the growth period (ranging from 4 to 20 mol.m-2.d-1). Basil plants were harvested 45 d after seeding. Using GC-MS, we explored, identified, and quantified several important volatile organic compounds (VOCs) with known influence on sensory perception and/or plant physiological processes of sweet basil. We found that the spectral quality from SL sources, in addition to changes in the spectra and DLI of ambient sunlight across growing seasons, directly influence basil aroma volatile concentrations. Further, we found that specific ratios of narrowband B/R wavelengths, combinations of discrete narrowband wavelengths, and broadband wavelengths directly and differentially influence the overall aroma profile as well as specific compounds. Based on the results of this study, we recommend supplemental 450 and 660 nm (± 20 nm) wavelengths at a ratio of approximately 10B/90R at 100-200 µmol.m-2.s-1, 12-24 h.d-1 for sweet basil grown under standard greenhouse conditions, with direct consideration of the natural solar spectrum and DLI provided for any given location and growing season. This experiment demonstrates the ability to use discrete narrowband wavelengths to augment the natural solar spectrum to provide an optimal light environment across variable growing seasons. Future experiments should investigate SL spectral quality for the optimization of sensory compounds in other high-value specialty crops.

Analysis of Important Volatile Organic Compounds and Genes Produced by Aroma of Pepper Fruit by HS-SPME-GC/MS and RNA Sequencing.

Pepper is an important condiment, and its aroma affects its commercial value. In this study, transcriptome sequencing and combined headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS) were used to analyze the differentially expressed genes and volatile organic compounds in spicy and non-spicy pepper fruits. Compared with non-spicy fruits, there were 27 up-regulated volatile organic compounds (VOCs) and 3353 up-regulated genes (Up-DEGs) in spicy fruits. The results of KEGG enrichment analysis of the Up-DEGs combined with differential VOCs analysis showed that fatty acid biosynthesis and terpenoid biosynthesis may be the main metabolic pathways for aroma differences between non-spicy and spicy pepper fruits. The expression levels of the fatty acid biosynthesis-related genes FAD, LOX1, LOX5, HPL, and ADH and the key terpene synthesis gene TPS in spicy pepper fruits were significantly higher than those in non-spicy pepper fruits. The differential expression of these genes may be the reason for the different aroma. The results can provide reference for the development and utilization of high-aroma pepper germplasm resources and the breeding of new varieties.

Screening of Breast Cancer from Sweat Samples Analyzed by 2-Dimensional Gas Chromatography-Mass Spectrometry: A Preliminary Study.

Breast cancer (BC) remains one of the most commonly diagnosed malignancies in women. There is increasing interest in the development of non-invasive screening methods. Volatile organic compounds (VOCs) emitted through the metabolism of cancer cells are possible novel cancer biomarkers. This study aims to identify the existence of BC-specific VOCs in the sweat of BC patients. Sweat samples from the breast and hand area were collected from 21 BC participants before and after breast tumor ablation. Thermal desorption coupled with two-dimensional gas chromatography and mass spectrometry was used to analyze VOCs. A total of 761 volatiles from a homemade human odor library were screened on each chromatogram. From those 761 VOCs, a minimum of 77 VOCs were detected within the BC samples. Principal component analysis showed that VOCs differ between the pre- and post-surgery status of the BC patients. The Tree-based Pipeline Optimization Tool identified logistic regression as the best-performing machine learning model. Logistic regression modeling identified VOCs that distinguish the pre-and post-surgery state in BC patients on both the breast and hand area with sensitivities close to 1. Further, Shapley additive explanations and the probe variable method identified the most important and pertinent VOCs distinguishing pre- and post-operative status which are mostly of distinct origin for the hand and breast region. Results suggest the possibility to identify endogenous metabolites linked to BC, hence proposing this innovative pipeline as a stepstone to discovering potential BC biomarkers. Large-scale studies in a multi-centered VOC analysis setting must be carried out to validate obtained findings.

Control of the pore chemistry in metal-organic frameworks for efficient adsorption of benzene and separation of benzene/cyclohexane

Control of the pore chemistry in metal-organic frameworks for efficient adsorption of benzene and separation of benzene/cyclohexane

Characteristics of volatile organic compounds in 11 cities along Taihang Mountain, an industrial region in Northern China

The cities along Taihang Mountain, one of the most important industrial regions in China, have faced challenges in atmospheric pollution control due to the development of industries. However, few studies have focused on the pollution characteristics of volatile organic compounds (VOCs) in this region. The concentrations, composition, sources, and chemical reactivity of VOCs were analyzed in 11 cities along Taihang Mountain. The average VOC concentration in the 11 cities (31.4 ± 11.3 ppbv) was higher than that for most cities in China, which was attributed to emissions from coal combustion and industrial processes. Four cities in Hebei province had the highest VOC concentration (32.9 ± 10.9 ppbv). Alkene (7.4 ± 3.9 ppbv) and alkyne (2.6 ± 1.9 ppbv) concentrations in the 11 cities were higher than those in other Chinese cities (2.4–5.9 and 1.0–3.8 ppbv, respectively). Shanxi Province had the largest contributions of alkenes (23.6%) and alkynes (9.7%). Based on the benzene/toluene (B/T) ratio, the 11 cities were divided into three categories: four had B/T ratios of 0.5–0.6, and were classified the “traffic” cities, and four with B/T ratios of 1.5–2.2 were classified as “coal combustion” cities. The chemical reactivity results showed that alkenes were the most important VOCs in terms of ozone formation. Coal combustion and industrial processes were the main emission sources affecting VOCs and O3 pollution in the 11 cities along Taihang Mountain. VOC researchers should pay more attention to this region, and more refined research should be conducted.

Anthropogenic VOCs in the Long Island Sound, NY Airshed and their role in ozone production

Cities like New York and areas downwind have poor air quality due to pollution generated by human activity. Ozone (O3), a harmful pollutant, is produced in the atmosphere from photochemical reactions involving volatile organic compounds (VOCs) and nitrogen oxides (NOx). Aircraft measurements of VOCs obtained during an O3 event in May 2017 over the New York City metropolitan area, Long Island Sound, and Connecticut show concentrations of O3 exceeding 100 ppb between ∼200 and 500 m above the surface. During this campaign, 35 whole air canisters were collected, and 50 VOC species were measured. Biogenic isoprene often dominates VOC reactivity in summer months, but analysis of the chemistry in the middle of the Planetary Boundary Layer (PBL) indicates that primary anthropogenic VOCs such as propylene and isopentane played a major, possibly dominant role in this Spring 2017 O3 event and are suitable targets for control.The most important measured anthropogenic VOCs ranked by OH reactivity were propylene and isopentane, with n-butane and 1-pentene also playing a substantial role. The most important anthropogenic VOCs ranked by Ozone Formation Potential (OFP) were again propylene and isopentane, but aromatic species like toluene were also large contributors. Isoprene ranked tenth in importance for OFP. For VOC species with short lifetimes, like isoprene and propylene, mixing of air parcels throughout the PBL means air above the surface may quickly become depleted of these VOCs, allowing longer-lived, anthropogenic VOCs to have a proportionally greater impact on photochemical O3 production aloft. Our observations indicate that VOC reactivity was much larger in the morning than in the afternoon, suggesting controls of propylene, isopentane, and aromatics overnight may be useful for reducing morning concentrations of VOCs and therefore possibly reduce maximum concentrations of O3 observed in the afternoon. Finally, because formaldehyde (HCHO) was not measured during these flights, and since oxygenates also contribute to O3 formation, we estimate the relative contribution of isoprene and propylene to HCHO formation using a box model. Propylene produces ∼25% and isoprene produces ∼4% of HCHO within the box model.

Response of heritage and modern wheat varieties to altitude induced stresses by synthesis of volatile compounds. A multivariate statistical analysis

The genotype × altitude interactive effect on crops quality is a crucial topic for researchers who face the challenge of climate changes. In this study, three common and durum wheat, including two old varieties, were grown for three years in different organic farms sited at three altitudes in the Abruzzo region (Italy). Volatile organic compounds (VOCs), along with agronomic yield and protein content were analysed. Genotype × altitude interaction resulted always statistically significant and altitude of cultivation negatively affected yield and protein content. A multivariate statistical approach permitted to unravel the most important VOCs useful to predict the effect of altitude of cultivation on wheat species. Durum wheat synthetized a higher number of VOCs than common wheat as a response to altitude-induced stress. Elevation of cultivation determined also a strong variety-dependent adaptative response, with characteristic VOCs patterns for any specific wheat. Heritage wheat emitted a higher number of volatiles in response to altitude changes, with (E)-2-Nonenal being a putative marker of these varieties. These results reveal the complexity behind the plants system defence against abiotic and biotic stresses induced by altitude and could open new perspectives for the study of the dependence of wheat production and quality on the territory.

Gas Chromatography Mass Spectrometry (GCMS) analysis of the antagonistic potential of &lt;i&gt;Trichoderma hamatum&lt;/i&gt; against &lt;i&gt;Fusarium oxysporum&lt;/i&gt; f. sp. cepae causing basal rot disease of onion

Fusarium oxysporum f. sp. cepae causing basal rot disease of onion is a destructive phytopathogen resulting in 30-50% yield loss and remains as a major constraint in onion productivity. The management of disease through application of fungicide is not feasible and economically viable. Hence, the present study is focused on investigation of effective Trichoderma sp. and identifying the effective volatile organic compounds produced by it against the basal rot pathogen in onion. A total of ten Trichoderma spp. were isolated from rhizospheric soil of healthy onion plants and tested against virulent Fusarium oxysporum f. sp. cepae isolate FCIM1. The Trichoderma isolate (TIM2) showed 77.40% inhibition on mycelial growth of pathogen followed by the isolate (TIV1) with 70.36% inhibition. The molecular identification of effective Trichoderma isolate through the analysis of the rDNA of Internal Transcribed Spacers (ITS) region revealed isolate TIM2 as Trichoderma hamatum. The GC-MS analysis of Trichoderma hamatum unravelled the important volatile organic compounds like Methyl stearate, n-Hexadecanoic, Eicosane, 9-cyclohexy, Heptadecane, Dodecane, 2-cyclohexyl, to 2H-Pyran-2-one, 6-pentyl, 5-Hydroxymethylfurfural, Tetrapentacontane, 1-Dodecanol, 2-Propenoic acid, pentadecyl ester, Benzene, (2-methylbutyl) and 1,2-Dimethyltryptamine with peak area and retention time. These bioactive compounds exert a strong antifungal activity against Fusarium oxysporum f. sp. cepae. The scanning electron micrographs of Fusarium paired with effective Trichoderma (TIM2) showed the swollen hyphae with cell wall damage which is clear evident of antagonistic interaction of volatile compounds produced by Trichoderma hamatum.

Genomic, metabonomic and transcriptomic analyses of sweet osmanthus varieties provide insights into floral aroma formation

Sweet osmanthus is an important ornamental evergreen tree or shrub, which has been widely used in the world's subtropical landscapes and the fragrance industry due to its deliciously fragrant flowers. In this study, whole-genome resequencing, RNA sequencing, and GC-MS analysis were used to compare 30 accessions of Osmanthus fragrans to gain insights into taxonomic classification and the diversity of volatile floral scents. A total of 13,466,389 high confidence SNPs were identified from the accessions with an average sequencing depth of 16.96 × . Phylogenetic analysis of the sequences of the 30 ancient or improved O. fragrans genotypes with diverse origins could be roughly divided into two differentiated sweet osmanthus populations, corresponding to the autumn-flowering and the four-seasons flowering characteristics. The odor activity values and orthogonal projections to latent structures-discriminant analysis of GC-MS metabolomics data indicated that linalool was one of the most important volatile organic compounds (VOCs) which can determine the scent diversity among different sweet osmanthus cultivars. Weighted gene co-expression network analysis (WGCNA) identified 23 distinct modules, four of which were highly associated with important floral VOCs. Based on WGCNA analysis, a critical enzyme gene OfHDR2.1 in the MEP pathway and its 12 co-expression transcription factors from the turquoise module were considered to play important roles in linalool synthesis among differently scented O. fragrans populations. Thus, our study provided new clues for the classification of O. fragrans cultivars and valuable genetic resources for future molecular breeding of O. fragrans accessions improved with respect to floral aroma.

OH-initiated degradation of 1,2,3-trimethylbenzene in the atmosphere and wastewater: Mechanisms, kinetics, and ecotoxicity

1,2,3-Trimethylbenzene (1,2,3-TMB) is an important volatile organic compound (VOC) present in petroleum wastewater and the atmosphere. This compound can be degraded by OH radicals via abstraction, addition and substitution mechanisms. Results show that the addition mechanism is dominant and H-abstraction is subdominant, while methyl abstraction and substitution mechanisms are negligible in the gas and aqueous phases. Moreover, H-abstraction products undergo further reactions with O2, NO, NO2, H2O, and OH radicals in the atmosphere. Time-dependent density functional theory (TDDFT) calculations show that the degraded products, including 2,3,4-trimethylphenyl-nitroperoxoite, 1,2,3-trimethyl-4-nitrobenzene, 1,2,3-trimethyl-5-nitrobenzene, 2,6-dimethylbenzyl nitroperoxoite, 2,3-dimethylphenyl nitroperoxoite, 2,6-dimethylbenzaldehyde, and 2,3-dimethylbenzaldehyde, can photolyze under the sunlight. Kinetically, the calculated total rate constant is 5.57 × 10−11 cm3 molecule−1·s−1 at 1 atm and 298 K, which is consistent with available experimental values measured in the atmosphere. In addition, the calculated total reaction rate constant in water is close to that in the gas phase. In terms of ecotoxicity, all degradation products are less toxic than the initial reactant to fish, green algae and daphnia. For mammals represented by rats, 1,2,3-TMB and its products are moderately toxic, except for 2,3-dimethylphenol and 2,6-dimethylphenol, which are slightly toxic.