Low Volatile Compounds Research Articles

Production of Algae-Based Carbon Black Pigment and Its Use in Carbon Neutral Printing Technologies

Within the scope of the project, we focused on the innovation potential in printing technologies, which is a common problem for all sectors, taking into account the contribution of chemistry to sustainability in innovation-oriented sectors. Based on the importance of microalgae in biomass, we obtained biochar for the production of carbon black pigment. Biochar provided an important result especially in the production of a pigment that has the potential to replace petroleum-derived carbon black pigment from fresh and salty algae such as Spirulina and Nannochloropsis. By using the raw pigment material we obtained together with environmentally friendly vegetable resins, we turned it into a product with low volatile organic compounds and no heavy metals. In this context, we examined the potential of the product formed in many dierent sub-elds of biochar printing technologies such as direct printing, UV curing and printing. With biocompatibility experiments, we also examined the status of the project in terms of human and environmental health. Thus, we have obtained preliminary findings on the transition from biomass to printing technologies, which has the potential for an important sectoral change. It will be possible to obtain more qualified and comprehensive products with future experiments. This transformation has the potential to affect many stakeholders for production and consumption.

Identification of five volatile organic compounds that trigger hygienic and recapping behaviours in the honey bee (Apis mellifera).

Varroa destructor, the main parasite of the honey bee (Apis mellifera), is having a devastating effect on beekeeping worldwide. The development of resistance traits in some colonies, linked with Varroa-sensitive hygiene (VSH) and recapping (REC) behaviours, provide an ideal avenue for long-term sustainable control of the parasite. The most important step in these behaviours is the detection of parasitized brood cells. Several semiochemicals released from Varroa-infested brood cells, targeted by VSH behaviour, trigger this behaviour. Most of these compounds are not very volatile. In the current work, we focus on the study of volatile organic compound (VOC) emissions from Varroa-infested cells. This study describes the emission of nine VOCs characteristic of Varroa parasitism, of which five could be identified and triggered hygienic and recapping behaviours. These five compounds were also tested with compounds already described in the literature, in relation to the volatile nature of the compounds. Using solutions containing 1 - 15 compounds, we looked at the cleaning and recapping behaviours of the workers. Behavioural results highlight the importance of the VOCs found in this study in the detection, opening and recapping of brood cells, while low volatile compounds seem to play a particularly key role in the sacrifice of pupae. Similar to the Varroa parasitization-specific (VPS) compounds, including the tetracosyl acetate alone, the cleaning of brood cells triggered by one of the compounds identified in this study, n-tetradecane, appears to be linked to the colony's ability to carry out VSH behaviour. This study opens new perspectives in the understanding of resistance behaviour of honey bees against their main parasite Varroa destructor.

Thermal‐Oxidative Aging Behavior and Factors of Polystyrene‐Based Thermoplastic Elastomers‐Based Automotive Interior Skin

ABSTRACTCompared to traditional polyvinyl chloride (PVC), polyurethane (PU), and thermoplastic olefin (TPO) materials, thermoplastic elastomers (TPEs) offer advantages of complete recyclability, absence of plasticizers and solvents, superior mechanical properties, pleasing tactile characteristics, low volatile organic compounds (VOCs) emissions, and cost‐effective processing. Making it an exceptional choice for environmentally friendly automotive skin materials. The automotive skin is frequently subjected to harsh conditions, such as high temperatures and oxygen exposure during use, presenting a significant durability challenge. Therefore, this study focuses on polystyrene (PS)‐based thermoplastic elastomers (TPE‐S) as the subject and investigates the influence of molecular weight, PS content, and chain structure in the blend on the mechanical properties of TPE‐S using an accelerated thermal‐oxidative aging method. Meanwhile, the changes of TPE‐S during the aging process are discussed via molecular weight, crystalline structure, molecular chain structure, microphase separation structure, and tactile sensation, providing a scientific foundation for guiding the selection of TPE‐S in automobile skin and heat oxidative aging resistance ability.

Nontarget screening of a Siberian ice core reveals changes in the pre-industrial to industrial organic aerosol composition.

Glaciers serve as natural archives for reconstructing past changes of atmospheric aerosol concentration and composition. While most ice-core studies have focused on inorganic species, organic compounds, which can constitute up to 90% of the submicrometer aerosol mass, have been largely overlooked. To our knowledge, this study presents the first nontarget screening record of secondary organic aerosol species preserved in a Belukha ice core (Siberia, Russian Federation), ranging from the pre-industrial to the industrial period (1800-1980 CE). We identified a total of 398 molecules, primarily polar and low-volatile compounds. Since the 1950s, the atmospheric aerosol composition has changed, with the appearance of organic molecules, including nitrogen-containing compounds, deriving from enhanced atmospheric reactions with anthropogenic NOx, or direct emissions. In addition, there was a significant increase in the oxygen-to-carbon ratio (+3%) and the average carbon oxidation state (+18%) of the detected molecules compared to the pre-industrial period, suggesting an increased oxidative capacity of the atmosphere.

Dual spatial region flexible chlorine based ionic hypercrosslinked polymer synergistically adsorb formaldehyde and carbon dioxide

Efficient adsorption and purification of low concentration volatile organic compounds (VOCs) and carbon dioxide (CO2) mixture in high-humidity environments remain a daunting challenge for researchers. In this study, a dual spatial region synergistic adsorption strategy was proposed to achieve synchronous and efficient capture of formaldehyde and CO2 on flexible chlorine (Cl) based ionic hypercross-linked polymer (Cl-IHCP). Through the ordered self-assembly of ionic monomers, the array-distributed free Cl, terminal Cl, and pyrrole nitrogen (N) sites were integrated into the skeletal network of Cl-IHCP and formed ultra-microporous environment with two different adsorption regions. Different adsorption regions exhibited varying adsorption affinities for formaldehyde and CO2 molecules on three sites, thereby weakening their competitive adsorption and achieving high adsorption for both. Besides, the strong binding force of formaldehyde and CO2 molecules in different regions makes the skeleton-responsive swelling of Cl-IHCP, and created new adsorption microenvironments for the other adsorbate. This manner considerably enhanced the adsorption capacity of Cl-IHCP for formaldehyde and CO2 in mixed-component, increasing by approximately 45% and 70% respectively compared to single component formaldehyde and CO2. These fascinating properties enabled Cl-IHCP to synergistically adsorb formaldehyde and CO2 mixtures in high humidity environments. This study innovatively proposed a simple and cost-effective strategy for removing VOCs and CO2 under high humidity, providing a feasible solution for green air purification technology.

Assessment of CPME as Sustainable Low VOC Alternative to Hexane: Optimization of Extraction Efficiency and Bioactive Compound Yield from Fenugreek Seed Oil Using Computational and Experimental Methods.

This study investigates the performance of cyclopentyl methyl ether (CPME) in the extraction of fenugreek seed oil, aiming to replace the conventionally used hexane. The efficiency of this alternative solvent was evaluated first through in silico methods (based on Hansen Solubility Parameters (HSPs) and Conductor-like Screening Model for Real Solvent (COSMO-RS) simulations), followed by experimental studies. Solubility computational predictions analysis revealed that CPME exhibits superior solvation power compared to hexane. Experimentally, CPME demonstrated a significantly higher oil yield (7.23%) compared to hexane (4.25%) and a better retention of beneficial unsaturated fatty acids than hexane. Additionally, the physicochemical properties of oils extracted with CPME showed enhanced oxidative stability, sterol, tocopherol, and phenolic contents, leading to superior antioxidant and antibacterial activities. Importantly, CPME's low volatile organic compound (VOC) emissions further establish it as a more sustainable and environmentally friendly alternative to hexane, aligning with contemporary goals of reducing harmful emissions in extraction processes. Thus, this paper highlights the functional advantages of CPME, focusing on its efficiency, selectivity, and enhanced retention of bioactive compounds, positioning it as a superior extraction solvent for fenugreek seed oil compared to hexane.

CONCERNING EFFECTS OF INERT CARRIER GAS ON DENSITIES OF ACTIVE SPECIES AND ZrO2 ETCHING KINETICS IN CHLORINE PLASMA

In this work, we investigated the influence of inert carrier gas on electro-physical plasma parameters, steady-state densities of active species and kinetics of their interaction with ZrO2 under the condition of “soft” reactive-ion etching in chlorine. This regime assumes the lower-than-usual negative bias voltage in order to reduce both ion bombardment energy and etched surface damage. The combination of plasma diagnostics by Langmuir probes and 0-dimensional plasma modeling allowed one to analyze formation and decay kinetics for neutral and charged species at various gas mixing ratios. It was found that the mixing of Cl2 with Ar or He at constant total gas pressure a) causes an increase in both electron temperature and plasma density; b) increases the Cl2 dissociation degree through the acceleration of electron-impact processes; and c) intensifies the ion bombardment by the change of ion flux. From etching experiments, it was found also that the ZrO2 etching rate is mostly composed by its chemical component, but does not correlate with the change in the Cl atom flux. The latter reveals that a) the dominant ZrO2 etching mechanism is the ion-assisted chemical reaction and b) an increase in the effective reaction probability toward Ar or He rich plasmas reflects the acceleration of ion-induced heterogeneous effects, such as the destruction of Zr-O bonds and/or the desorption of low-volatile ZrClx compounds. The lower neutral/charged ratio obtained in Ar-containing plasma allows one to assume the more anisotropic etching. It was shown that above findings are surely valid in the pressure range of 4–12 mTorr as well at bias powers of 100 – 300 W. For citation: Efremov A.M., Smirnov S.A., Betelin V.B., Kwon K.-H. Concerning effects of inert carrier gas on densities of active species and ZrO2 etching kinetics in chlorine plasma. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 11. P. 40-54. DOI: 10.6060/ivkkt.20246711.7073.

Unraveling the influence of boiling time on aroma generation in Huajiao (Zanthoxylum bungeanum Maxim.) water during boiling through molecular sensory science

Huajiao water (HW) has a wide range of applications in the new food service industry. However, few process and flavor studies have been conducted on HW. The aim of this study was to investigate the effect of boiling process on HW flavor as well as the mechanisms by which important aroma compounds affect the flavor. The results showed that HW-20 min had better flavor quality and typical flavor of Huajiao. Boiling time mainly affected the content of terpenoid, which subsequently affected the overall flavor of HW. Compared to dried Huajiao (DH), HW had significantly lower volatile compounds. Limonene and linalool were abundant volatile compounds in DH and HW. Finally, the potential degradation pathways of limonene and linalool were summarized based on model experiments and isotopic tracer techniques, respectively. This study provided a feasible solution for the investigation of the transformation pathway and the flavor regulation of HW in industry.

Nocturnal atmospheric synergistic oxidation reduces the formation of low-volatility organic compounds from biogenic emissions

Abstract. Volatile organic compounds (VOCs) are often subject to synergistic oxidation by different oxidants in the atmosphere. However, the exact synergistic-oxidation mechanism of atmospheric VOCs and its role in particle formation remain poorly understood. In particular, the reaction kinetics of the key reactive intermediates, organic peroxy radicals (RO2), during synergistic oxidation is rarely studied. Here, we conducted a combined experimental and kinetic modeling study of the nocturnal synergistic oxidation of α-pinene (the most abundant monoterpene) by O3 and NO3 radicals as well as its influences on the formation of highly oxygenated organic molecules (HOMs) and particles. We find that in the synergistic O3 + NO3 regime, where OH radicals are abundantly formed via decomposition of ozonolysis-derived Criegee intermediates, the production of CxHyOz HOMs is substantially suppressed compared to that in the O3-only regime, mainly because of the depletion of α-pinene RO2 derived from ozonolysis and OH oxidation by those arising from NO3 oxidation via cross reactions. Measurement–model comparisons further reveal that the cross-reaction rate constants of NO3-derived RO2 with O3-derived RO2 are on average 10–100 times larger than those of NO3-derived RO2 with OH-derived RO2. Despite a strong production of organic nitrates in the synergistic-oxidation regime, the substantial decrease in CxHyOz HOM formation leads to a significant reduction in ultralow- and extremely low-volatility organic compounds, which significantly inhibits the formation of new particles. This work provides valuable mechanistic and quantitative insights into the nocturnal synergistic-oxidation chemistry of biogenic emissions and will help to better understand the formation of low-volatility organic compounds and particles in the atmosphere.

A direct immersion-solid-phase microextraction method for the automated determination of 3- to 6-ring polycyclic aromatic hydrocarbons in saliva by gas-chromatography-tandem mass spectrometry

This work presents a novel method for the analysis of polycyclic aromatic hydrocarbons (PAHs) in saliva samples using solid phase microextraction (SPME) coupled with gas chromatography-triple quadrupole mass spectrometry (GC-QqQ-MS). The protocol utilizes the latest commercially available overcoated fiber (PDMS/DVB/PDMS) for direct immersion extraction of the target analytes, enabling the determination of thirteen PAHs, including low-volatile compounds. The SPME extraction method was optimized using a central composite design (CCD). The evaluation of the fiber coating's robustness over time demonstrated excellent extraction performance with no significant degradation. The validation procedure confirmed good performance for all parameters, with LOQ values (100 ng/L for ten analytes and 500 ng/L for three analytes) comparable to other chromatographic methods. The environmental impact of the protocol was objectively assessed using two recently proposed metrics: the Green Analytical Procedure Index (GAPI) and the Analytical Greenness metric for sample preparation (AGREEprep). Both metrics indicated good overall environmental friendliness, with AGREEprep providing a satisfactory comprehensive score despite the use of highly impactful instrumentation. These characteristics make the developed method suitable for routine analysis in environmental and epidemiological monitoring.

Analysis of forensic polymer samples using double shot pyrolysis gas chromatography – Mass spectrometry

Polymers are present in many different products, such as paints, plastics, and rubbers, which are routinely encountered in forensic casework. Comparison of such samples involves an initial visual examination followed by comparison of the chemical compositions of the exhibits. Techniques such as Fourier transform infrared spectroscopy (FTIR) and pyrolysis gas chromatography – mass spectrometry (PyGC-MS) have been reported for determining the chemical compositions of polymers in forensic samples. Double-shot pyrolysis gas chromatography – mass spectrometry (DS-PyGC-MS) is an extension of single-shot pyrolysis gas chromatography – mass spectrometry (SS-PyGC-MS) which is the current PyGC-MS method used in most forensic laboratories. DS-PyGC-MS involves a preliminary thermal desorption GC-MS step, followed by the pyrolysis GC-MS step, with this second step being analogous to SS-PyGC-MS. The pyrolyser furnace operates at a lower temperature during the thermal desorption step, allowing low volatility compounds, such as additives, to be thermally desorbed and detected, minimising interference from the polymeric component of the sample. This pilot study analysed four different polymeric substrates, commonly encountered in forensic casework, by DS-PyGC-MS. The substrates chosen were tyre rubber, road cones, cling film, and shotgun wads. The aim was to investigate whether more chemical information was generated by DS-PyGC-MS compared to SS-PyGC-MS, potentially providing increased discrimination of such samples. Qualitative results showed that tyre rubber and road cones were ideal substrates for DS-PyGC-MS. A wide range of additives were detected in these samples in the thermal desorption step, which were not detected using SS-PyGC-MS. All of the rubber tyres (n=5) and road cones (n=6) were able to be uniquely distinguished using DS-PyGC-MS. Some additional compounds were detected in the thermal desorption analysis of shotgun wads (n=4), providing increased discrimination compared to SS-PyGC-MS. For the cling film samples analysed (n=7) the polyethylene-based cling films (n=6) could not be distinguished from each other, with no compounds detected in the thermal desorption step. The other cling film sample contained a mixture of polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) and could easily be distinguished from the polyethylene-based cling films using either SS- or DS-PyGC-MS, or other common analytical methods such as Fourier transform infrared spectroscopy (FTIR). This pilot study has demonstrated that DS-PyGC-MS has the potential to provide more comprehensive chemical composition information for some polymeric substrates and is a promising method for the forensic comparison of polymer evidence.

Complementarity of two-dimensional gas chromatography and two-dimensional liquid chromatography for the analysis of depolymerised lignin

Two-dimensional gas chromatography (GC × GC) and two-dimensional liquid chromatography (LC × LC) are nowadays widely used in academia and industry due to their high separation power. However, as far as we know, the complementarity of these two techniques has not yet been thoroughly studied based on the analysis of the same sample. Therefore, this was undertaken here by analysing the liquid fraction obtained after depolymerising a natural waste – lignin – with GC × GC and off-line comprehensive LC × SFC (SFC: supercritical fluid chromatography). Using complementary techniques is also important for lignin valorisation, as thorough structural characterisation of the depolymerised product can aid with developing and improving valorisation processes. For the tentative identification, NIST library was used for GC × GC–MS results and MS-DIAL together with SIRIUS for LC × SFC-MS/MS data. This allowed to study which compounds are detectable with the different 2D methods but also to discuss the limitations of the data analysis processes. The previous knowledge that LC techniques are more suitable than GC × GC for the analysis of larger oligomers and other low volatility compounds was confirmed; however, it was seen that GC × GC enabled the analysis of smaller compounds, such as aliphatic alcohols and saturated compounds. Overall, the study demonstrates the complementarity of the two techniques but also draws attention to the different detectable compound groups and classifications that the two techniques can provide.

The role of solar photolysis in the atmospheric removal of methacrolein oxide and the methacrolein oxide-water van-der Waals complex in pristine environments.

Biogenic hydrocarbons are emitted into the Earth's atmosphere by terrestrial vegetation as by-products of photosynthesis. Isoprene is one such hydrocarbon and is the second most abundant volatile organic compound emitted into the atmosphere (after methane). Reaction with ozone represents an important atmospheric sink for isoprene removal, forming carbonyl oxides (Criegee intermediates) with extended conjugation. In this manuscript, we argue that the extended conjugation of these Criegee intermediates enables electronic excitation of these compounds, on timescales that are competitive with their slow unimolecular decay and bimolecular chemistry. We show that the complexation of methacrolein oxide with water enhances the absorption cross section of the otherwise dark S1 state, potentially revealing a new avenue for forming lower volatility compounds via tropospherically relevant photochemistry.

Field study on the uptake pathways and their contributions to the accumulation of organophosphate esters, phthalates, and polycyclic aromatic hydrocarbons in upland rice

Plant uptake of organic contaminants generally occurs through either root, gas-phase foliar, or particle-phase foliar uptake. Understanding these pathways is essential for food-system practitioners to reduce human exposures, and to clean contaminated-sites with phytoremediation. Herein, we conducted a field-based experiment using an improved specific exposure chamber to elucidate the uptake pathways of organophosphate esters, phthalates, and polycyclic aromatic compounds, and quantitatively assessed their contributions to organic contaminant accumulations in field-grown rice. For most target compounds, all three uptake pathways (root, foliar gas, and foliar particle uptakes) contributed substantially to the overall contaminant burden in rice. Compounds with lower octanol–water partition coefficients (Kow) were more readily translocated from roots to leaves, and compounds with higher octanol−air partition coefficients (Koa) tended to enter rice leaves mostly through particle deposition. Most compounds were mostly stored in the inner leaves (55.3–98.2 %), whereas the relatively volatile compounds were more readily absorbed by the waxy layer and then transferred to the inner leaves. Air particle desorption was a key process regulating foliar uptake of low-volatility compounds. The results can help us to better understand and predict the environmental fate of those contaminants, and develop more effective management strategies for reducing their human exposure through food ingestion.

Heavy Metals in Pyrolysis of Contaminated Wastes: Phase Distribution and Leaching Behaviour

Pyrolysis is a recognized alternative for the sustainable management of contaminated organic waste, as it yields energy-rich gas, oil, and a carbon-rich biochar product. Low-volatility compounds, however, such as heavy metals (HMs; As, Cd, Cu, Cr, Ni, Pb, and Zn) typically accumulate in biochars, limiting their application potential, especially for soil improvement. The distribution of HMs in pyrolysis products is influenced by treatment temperature and the properties of both the HMs and the feedstock. There is a significant knowledge gap in our understanding of the mass balances of HMs in full-scale industrial pyrolysis systems. Therefore, the fate of HMs during full-scale relevant pyrolysis (500–800 °C) of seven contaminated feedstocks and a clean wood feedstock were investigated for the first time. Most of the HMs accumulated in the biochar (fixation rates (FR) >70%), but As, Cd, Pb, and Zn partly partitioned into the flue gas at temperatures ≥ 600 °C, as demonstrated by FRs of <30% for some of the feedstocks. Emission factors (EFs, mg per tonne biochar produced) for particle-bound HMs (<0.45 µm) were 0.04–7.7 for As, 0.002–0.41 for Cd, 0.01–208 for Pb, and 0.09–342 for Zn. Only minor fractions of the HMs were found in the condensate (0–11.5%). To investigate the mobility of HMs accumulated in the biochars, a novel leaching test for sustained pH drop (at pH 4, 5.5 and 7) was developed. It was revealed that increasing pyrolysis temperature led to stronger incorporation of HMs in the sludge-based biochar matrix: after pyrolysis at 800 °C, at pH 4, <1% of total Cr, Cu, Ni, and Pb and < 10% of total As and Zn contents in the biochars were leached. Most interestingly, the high HM mobility observed in wood-based biochars compared to sewage-sludge-based biochars indicates the need to develop specific environmental-management thresholds for soil application of sewage-sludge biochars. Accordingly, more research is needed to better understand what governs the mobility of HMs in sewage-sludge biochars to provide a sound basis for future policy-making.

Thermal property characterization and modeling of SMAW electrode coating flux using ANN and regression analysis

The design and development of SMAW electrode coating fluxes, along with their thermal property characterization, are discussed. Using an extreme vertices design approach, 27 flux mixture combinations have been prepared. The TGA-DSC and hot disk analysis are done to quantify the thermal response of the fluxes. Results show that increase in CaF2 and SiO2 reduces weight loss. Increase in CaO increases weight loss, whereas increase in BaO shows minimal effect on weight loss. Enthalpy change of flux was found to influence mainly with CaF2 and CaO. Thermally stable flux has lower volatile compounds such as crystallization water and moisture, which helps to minimize gaseous entrapment in weld pool. An increase in CaF2 shows slight decreases and then increase in thermal diffusivity. The increase in thermal diffusivity leads to instant heat flow in the coating. Regression analysis is done, and the effect of individual and interaction of flux constituents on thermal properties is discussed. The artificial neural network is employed for predictive modeling in the domain of the mixture design approach, its prediction accuracy is compared with regression analysis. Water vapor solubility of slag was estimated between 3.169 and 3.947 and sulfide capacity of slag was − 2.479 to −1.892.

Using the Multicomponent Aerosol FORmation Model (MAFOR) to Determine Improved VOC Emission Factors in Ship Plumes.

International shipping's particulate matter primary emissions have a share in global anthropogenic emissions of between 3% and 4%. Ship emissions of volatile organic compounds (VOCs) can play an important role in the formation of fine particulate matter. Using an aerosol box model for the near-plume scale, this study investigated how the changing VOC emission factor (EF) for ship engines impacts the formation of secondary PM2.5 in ship exhaust plumes that were detected during a measurement campaign. The agreement between measured and modeled particle number size distribution was improved by adjusting VOC emissions, in particular of intermediate-, low-, and extremely low-volatility compounds. The scaling of the VOC emission factor showed that the initial emission factor, based on literature data, had to be multiplied by 3.6 for all VOCs. Information obtained from the box model was integrated into a regional-scale chemistry transport model (CTM) to study the influence of changed VOC ship emissions over the Mediterranean Sea. The regional-scale CTM run with adjusted ship emissions indicated a change in PM2.5 of up to 5% at the main shipping routes and harbor cities in summer. Nevertheless, overall changes due to a change in the VOC EF were rather small, indicating that the size of grid cells in CTMs leads to a fast dilution.

Natural Marine Precursors Boost Continental New Particle Formation and Production of Cloud Condensation Nuclei.

Marine dimethyl sulfide (DMS) emissions are the dominant source of natural sulfur in the atmosphere. DMS oxidizes to produce low-volatility acids that potentially nucleate to form particles that may grow into climatically important cloud condensation nuclei (CCN). In this work, we utilize the chemistry transport model ADCHEM to demonstrate that DMS emissions are likely to contribute to the majority of CCN during the biological active period (May-August) at three different forest stations in the Nordic countries. DMS increases CCN concentrations by forming nucleation and Aitken mode particles over the ocean and land, which eventually grow into the accumulation mode by condensation of low-volatility organic compounds from continental vegetation. Our findings provide a new understanding of the exchange of marine precursors between the ocean and land, highlighting their influence as one of the dominant sources of CCN particles over the boreal forest.

Development of a multiphase chemical mechanism to improve secondary organic aerosol formation in CAABA/MECCA (version 4.7.0)

Abstract. During the last few decades, the impact of multiphase chemistry on secondary organic aerosols (SOAs) has been demonstrated to be the key to explaining laboratory experiments and field measurements. However, global atmospheric models still show large biases when simulating atmospheric observations of organic aerosols (OAs). Major reasons for the model errors are the use of simplified chemistry schemes of the gas-phase oxidation of vapours and the parameterization of heterogeneous surface reactions. The photochemical oxidation of anthropogenic and biogenic volatile organic compounds (VOCs) leads to products that either produce new SOA or are taken up by existing aqueous media like cloud droplets and deliquescent aerosols. After partitioning, aqueous-phase processing results in polyols, organosulfates, and other products with a high molar mass and oxygen content. In this work, we introduce the formation of new low-volatility organic compounds (LVOCs) to the multiphase chemistry box model CAABA/MECCA. Most notable are the additions of the SOA precursors, limonene and n-alkanes (5 to 8 C atoms), and a semi-explicit chemical mechanism for the formation of LVOCs from isoprene oxidation in the gas and aqueous phases. Moreover, Henry's law solubility constants and their temperature dependences are estimated for the partitioning of organic molecules to the aqueous phase. Box model simulations indicate that the new chemical scheme predicts the enhanced formation of LVOCs, which are known for being precursor species to SOAs. As expected, the model predicts that LVOCs are positively correlated to temperature but negatively correlated to NOx levels. However, the aqueous-phase processing of isoprene epoxydiols (IEPOX) displays a more complex dependence on these two key variables. Semi-quantitative comparison with observations from the SOAS campaign suggests that the model may overestimate methylbutane-1,2,3,4-tetrol (MeBuTETROL) from IEPOX. Further application of the mechanism in the modelling of two chamber experiments, one in which limonene is consumed by ozone and one in which isoprene is consumed by NO3 shows a sufficient agreement with experimental results within model limitations. The extensions in CAABA/MECCA are transferred to the 3D atmospheric model MESSy for a comprehensive evaluation of the impact of aqueous- and/or aerosol-phase chemistry on SOA at a global scale in a follow-up study.

Alkene Cross-Metathesis with 2,5-Dimethyl-2,4-Hexadiene Enables Isobutylenyl/Prenyl Functionalizations and Rubber Valorization.

2,5-Dimethyl-2,4-hexadiene is a readily available and easily managable compound, whose symmetric and polymethylated dienic structure should be prone to engage in cross-metathesis reactions with other alkenes, but this has not been apparently exploited so far. Here we show that this reactant enables the easy synthesis of tri- and tetra-susbtituted alkenes (i. e. isobutylenyl and prenyl groups) from simple alkenes under mild reaction conditions, not only with the conventional 2nd generation Grubbs catalyst but also with other Grela-type catalyts such as StickyCat,TM AquaMetTM and GreenCatTM. The use of liquid and low volatile 2,5-dimethyl-2,4-hexadiene avoids the use of gaseous alkene reactants and, besides, showcases the reactivity of polyisoprene (rubber), thus allowing to optimize the reaction conditions for rubber upcycling, after metathesis reaction of the pristine or used polymer with simple alkenes. These results bring low volatile isoprene-type compounds as privileged poly-substituted reactants for alkene cross-metathesis reactions.