Solvents Petroleum Research Articles

Ultra-sensitive CO2 switchable low temperature transition mixture for intensified retrieval of oily waste

One of the challenge in the remediation of contaminated soil by solvent washing is the retrieval of total petroleum hydrocarbons (TPH) and solvents. Herein, a CO2 switchable hydrophobic low temperature transition mixture ([DPA][EL]) composed of ethyl lactate (EL) and dipropylamine (DPA) is proposed, accompanied by a proof-of-concept for contaminated soil washing. The path and energy of hydrogen bond interactions in [DPA][EL] were revealed by the quantum chemical calculation using the quantum theory of atoms in molecule. [DPA][EL] achieved a thorough CO2-induced polarity and hydrophobicity transition undergoing an incomplete CO2 absorption that results in the partial formation of carbonate and carbamate. [DPA][EL] was regenerated after the removal of CO2 by heating at 85 °C for 2 min. Thanks to this peculiarity, the time required for hydrophobicity transition was 197 times shorter than that of the typical CO2 switchable hydrophobic solvent, N,N-dimethylcyclohexylamine. The polarity of [DPA][EL], quantified by the normalized polarity energy, increased by 346.69 % after the introduction of CO2 because of the synergistic effect of water. This ultra-sensitive transition behavior intensified the CO2-induced separation of oily compounds, e.g., kerosene and crude oil. The conceptual usage of [DPA][EL] in the contaminated soil washing was demonstrated. The TPH content of contaminated soil decrease from 8.27 % to 0.31 % by [DPA][EL] washing through tailoring the molar ratio of DPA to EL in [DPA][EL], temperature, and [DPA][EL] to contaminated soil ratio (L/S, mL/g). [DPA][EL] whose composition possesses different polarities compensated for the poor solubility of single solvents towards TPH, thereby improving the washing efficiency of contaminated soil. Afterwards, TPH was separated upon triggered by CO2/water in 2 min, and 91.33 % of [DPA][EL] was subsequently regenerated at 85 °C in 2 min.

Primary and oxidative source analyses of consumed VOCs in the atmosphere

Consumed VOCs are the compounds that have reacted to form ozone and secondary organic aerosol (SOA) in the atmosphere. An approach that can apportion the contributions of primary sources and reactions to the consumed VOCs was developed in this study and applied to hourly VOCs data from June to August 2022 measured in Shijiazhuang, China. The results showed that petrochemical industries (36.9 % and 51.7 %) and oxidation formation (20.6 % and 35.6 %) provided the largest contributions to consumed VOCs and OVOCs during the study period, whereas natural gas (5.0 % and 7.6 %) and the mixed source of liquefied petroleum gas and solvent use (3.1 % and 4.2 %) had the relatively low contributions. Compared to the non-O3 pollution (NOP) period, the contributions of oxidation formation, petrochemical industries, and the mixed source of gas evaporation and vehicle emissions to the consumed VOCs during the O3 pollution (OP) period increased by 2.8, 3.8, and 9.3 times, respectively. The differences in contributions of liquified petroleum gas and solvent use, natural gas, and combustion sources to consumed VOCs between OP and NOP periods were relatively small. Transport of petrochemical industries emissions from the southeast to the study site was the primary consumed pathway for VOCs emitted from petrochemical industries.

Characteristic, source apportionment and effect of photochemical loss of ambient VOCs in an emerging megacity of Central China

During the transportation from emission sources to sampling site, volatile organic compounds (VOCs) undergo photochemical losses which have significant effects for tropospheric ozone (O3) formation and VOCs source apportionment. In this study, based on hourly speciated VOC data from May 23, to July 8, 2019 with high O3 concentrations, the concentration level, chemical composition, and diurnal variation of observed VOCs were studied, and the initial concentration of VOCs was obtained by combining the local emission inventory in Zhengzhou, Central China. The impact of photochemical loss on source apportionment was evaluated using the Positive Matrix Factorization/Multilinear Engine 2-Species Ratio (PMF/ME2-SR) model based on observed and initial VOCs concentration (OC-PMF and IC-PMF). Results suggest that during the observed period, the average concentration of total VOCs (TVOCs) was 23.74 ± 9.20 ppbv, and alkanes (3.92 ± 2.40 ppbv) were the predominant component. The photochemical losses of TVOCs were approximately 10.15 ± 7.13 ppbv, with an average loss rate of 29.9%. The ozone formation potential (OFP) based on the initial VOCs concentration was 2.2 times higher than that observed VOCs concentration. Alkenes contributed the most to OFP and were also the largest contributors to photochemical losses. TVOC concentrations increased by 5.0% during O3 pollution compared to non-O3 pollution. Seven sources of VOCs were determined, including biomass burning, liquefied petroleum gas (LPG), vehicle emission, industrial emission, solvent usage, gasoline evaporation, and biogenic emission. Compared to the results of IC-PMF, the contributions of these sources in OC-PMF were underestimated by 15.4%, 14.4%, 13.0%, 11.7%, 31.5%, 7.6%, and 4.7%, respectively. This study still exhibits certain limitations in calculation method, and further exploration can be conducted in the future.

ANALYSIS OF DISSOLVING ABILITY OF LOWER ALCOHOLS AND ESTERS AQUEOUS AND HYDROCARBON SOLUTIONS TO ORGANIC MATTER OF BAZHENOV FORMATION ROCKS

This work is devoted to studying the characteristics of treatments with organic solvents on bazhenov formation rock samples, which contains a large amount of unconverted organic matter (kerogen, bitumen). This article contains the results of studying the dissolving abilities of individual low-molecular alcohols and esters, and solutions of these compounds in water and in a non-polar aromatic solvent (petroleum solvent). Among the individual solvents studied, esters of acetic acid showed the greatest dissolving ability; alcohols are less active. Petroleum solvent slightly dissolves the rock’s organic matter and needs the addition of more polar organic compounds. The dependences of dissolving ability of alcohols’ hydrocarbon solutions on alcohol concentration is extreme, with a maximum of 10 wt.%. Based on the obtained results, the mutual influence of solvents in the hydrocarbon fluid was additionally evaluated. It has been established that solutions of isopropanol and aromatic solvent show a synergistic effect to the dissolution of rock organic matter more than hydrocarbon solutions of esters. For the compositions that showed the greatest dissolving ability, a qualitative and semi-quantitative analysis was made for establishing changes in the composition of rock samples after extraction using X-Ray diffraction and Fourier-transform infrared spectroscopy. It is shown that mixtures of polar and non-polar solvents provide a more regular extraction of aliphatic and aromatic components of rock organic matter. Systems containing petroleum solvent, isopropanol and isopropyl acetate have been identified as the basis for the development of process fluids for increasing oil recovery in organic-rich reservoirs.

A comprehensive observation on the pollution characteristics of peroxyacetyl nitrate (PAN) in Beijing, China

Peroxyacetyl nitrate (PAN) is a typical secondary photochemical product in the atmospheric environment with significant adverse effects on human health and plant growth. In this study, PAN and other pollutants, as well as meteorological conditions were observed intensively from August to September in 2022 at a typical urban sampling site in Beijing, China. The mean and maximum PAN concentrations during the observation period were 1.00 ± 0.97 ppb and 4.84 ppb, respectively. Severe photochemical pollution occurred during the observation period, with the mean PAN concentration about 3.1 times higher than that during the clean period. There was a good positive correlation between O3 and PAN, and their correlation was higher during the O3 exposure period than that during the clean period. The simulated results by box-model coupled with the Master Chemical Mechanism (MCM v3.3.1) showed that the O3-related reactions were the largest sources of OH radicals during O3 exposure period, which was conducive to the co-contamination of PAN and O3. Acetaldehyde (CH3CHO) and methylglyoxal (MGLY) were the largest OVOCs precursors of peroxyacetyl radicals (PA), with the contributions to the total PA generated by OVOCs about 67 % – 83 % and 17 % – 30 %, respectively. The reduction of emissions from liquefied petroleum gas (LPG) and solvent usage has the highest reduction effect on PAN and O3, followed by the control of gasoline vehicle exhaust emissions. This study deepens the understanding of the PAN photochemistry in urban areas with high O3 background conditions and the impact of anthropogenic activities on the photochemical pollution. Meanwhile, the findings of this study highlight the necessity of strengthening anthropogenic emissions control to effectively reduce the co-contamination of PAN and O3 in Beijing in the future.

Physical and Chemical Phenomena during the Production of Hydrogen in the Microwave Discharge Generated in Liquid Hydrocarbons with the Barbotage of Various Gases

The physical and chemical characteristics of the microwave discharge in petroleum solvent during hydrogen production processes involving Ar, He, and CO2 barbotage were studied. Gas chromatography, emission spectroscopy, high-speed photography, and shadow photography were used for diagnosis. The results demonstrated the dependence of hydrogen yield on the flow rates of Ar, He, and CO2. The maximum yield values of hydrogen were 791 mL/min and 811 mL/min, while the maximum energy efficiency reached 135.6 NL/kWh and 162.2 NL/kWh in Nefras with Ar and He barbotage, respectively. The dynamics of discharge structure and the rotational and vibrational temperatures of C2 molecules were studied.

Parental occupational exposure to solvents and risk of developing testicular germ cell tumors among sons: a French nationwide case-control study (TESTIS study).

The etiology of testicular germ cell tumors (TGCT) is suspected to be related to prenatal environmental risk factors. Some solvents have potential endocrine disrupting or carcinogenic properties and may disrupt male genital development in utero. The aim of this study was to examine the association between parental occupational exposure to solvents and TGCT risk among their offspring. A French nationwide case-control study, TESTIS included 454 TGCT cases and 670 controls frequency-matched on region and 5-year age strata. Participants were interviewed via telephone and provided information on parental occupations at birth. Job-exposure matrices (JEM) developed in the French Matgéné program were used to assign exposure to five petroleum-based solvents, five solvents or groups of oxygenated solvents, and five chlorinated solvents. Odds ratios (OR) for TGCT and 95% confidence intervals (CI) were estimated using conditional logistic regression, adjusting for TGCT risk factors. Occupational exposure to at least one solvent during the year of their son's birth was 41% among fathers and 21% among mothers. Paternal exposure to at least one solvent showed OR 0.89 (95% CI 0.68-1.15). Exposure to perchloroethylene (OR 1.41, 95% CI 0.55-3.61), methylene chloride (OR 1.13, 95% CI 0.54-2.34) and diesel/kerosene/fuel oil (OR 1.17, 95% CI 0.80-1.73) disclosed OR >1 but with low precision. Our results suggest a possible modest increase in non-seminoma risk for sons whose fathers were highly exposed to trichloroethylene (OR 1.44, 95% CI 0.79-2.63). Maternal exposure to at least one solvent showed OR 0.90 (95% CI 0.65-1.24). When stratifying by birth year, men born in the 1970s experienced an increased TGCT risk following maternal exposure to fuels and petroleum-based solvents (OR 2.74, 95% CI 1.11-6.76). Overall, no solid association was found between parental occupational exposure to solvents and TGCT risk. The association found with maternal occupational exposure to fuels and petroleum solvents among older men needs further investigation.

Crude algal biomass for the generation of thin-film composite solvent-resistant nanofiltration membranes

Sustainable development of membrane technologies requires novel source materials for membrane production which are not fossil fuel derived and do not use petroleum solvents for their fabrication. Here, we demonstrate eco-friendly and straightforward manufacturing of thin-film composite (TFC) membranes using crude soluble algal biomass without the need for chemical purification. Both sterilized clean-water and unsterilized wastewater-grown green algal biomasses generated similar results. The complex mixture of polysaccharides and soluble proteins provided reactive groups for crosslinking. The thickness of the selective layer made of algal biomass ranged from 13 to 94 nm. The algae-based TFC membranes exhibited robust stability in long-term tests performed in a continuous crossflow filtration system for 7 days. The sustainability and economic efficiency of our algal TFC membranes were compared to the state-of-the-art membrane fabrication and demonstrate, for the first time, that crude biomass, without excessive purification of bio-monomers or -polymers, can be successfully upcycled into membrane separation materials. The results provide a novel venue for conversion of algal biomasses that may not be suited for other consumer-use avenues like those produced from genetically modified strains or in wastewaters, into a useful material.

Forensic characterization and differentiation of automotive lubricating greases using Fourier Transform Infrared spectroscopy and Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy

Automotive lubricating greases may be recovered as stains on the ground at vehicular accident scenes or on the garments of persons of interest (i.e., suspects or victims) allegedly involved in events under investigation. Numerous studies have been performed differentiating automotive motor oil for forensic applications, however little research has been conducted to characterize and differentiate automotive greases for forensic purposes. This study aims to determine physical and chemical properties of greases to help with their characterization and differentiation in a forensic setting. Thirty-five commercially available grease samples were obtained from major US hardware stores and were initially characterized using light microscopy methods; then they were subsequently examined using attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The initial microscopical assessment showed the presence of microscopic particles that were part of the original formulation of the grease samples. In terms of shapes, sizes, colors, optical properties, and concentration, these particles differed considerably between the grease samples. Three classes of particles were identified and consequently labelled as opaque, isotropic, and anisotropic. ATR-FTIR spectroscopy enabled obtaining a common infrared profile characteristic of all for grease samples. Close inspection of the spectra also highlighted the presence of minor infrared absorption bands that were useful to the differentiation of different grease samples. Because of the high interference of the lubricating medium of the grease samples during SEM-EDS analyses, an oil-solid separation procedure to extract the observed microscopic particles from the grease medium was developed based on the investigation of three solvents – two petroleum solvents, hexane, and pentane, and one green solvent, D-limonene – which led to the selection of D-limonene. The developed extraction method enabled the successful isolation of the detected particles for conducting SEM-EDS analyses. The opaque particles were identified as solid lubricant additives, containing various amounts of molybdenum and niobium. Grease samples that did not contain opaque particles were missing these heavy elements. These differences in composition offered increased discriminating capabilities for the differentiation of automotive greases, also considering that such particles are not present in other automotive lubricating fluids like motor oils or brake fluids.

CO2 Decomposition in Microwave Discharge Created in Liquid Hydrocarbon

The task of CO2 decomposition is one of the components of the problem associated with global warming. One of the promising directions of its solution is the use of low-temperature plasma. For these purposes, different types of discharges are used. Microwave discharge in liquid hydrocarbons has not been studied before for this problem. This paper presents the results of a study of microwave discharge products in liquid Nefras C2 80/120 (petroleum solvent, a mixture of light hydrocarbons with a boiling point from 33 to 205 °C) when CO2 is introduced into the discharge zone, as well as the results of a study of the discharge by optical emission spectroscopy and shadow photography methods. The main gas products are H2, C2H2, C2H4, CH4, CO2, and CO. No oxygen was found in the products. The mechanisms of CO2 decomposition in the discharge are considered. The formation of H2 occurs simultaneously with the decomposition of CO2 in the discharge, with a volumetric rate of up to 475 mL/min and energy consumption of up to 81.4 NL/kWh.

Maternal occupational exposure to organic solvents and intrauterine growth in the ELFE cohort

BackgroundIn developed countries, about 15% of women are occupationally exposed to solvents. Associations between this maternal occupational exposure and intrauterine fetal growth are inconsistent, but almost no existing study has investigated this relation by solvent family (oxygenated, petroleum, and chlorinated), although they may affect fetal growth differently. ObjectivesTo investigate the relations between maternal occupational solvent exposure, by solvent family, and the risk of neonates born small for gestational age (SGA), or with low birthweight, or with small head circumference (HC). MethodsAmong the 18,040 women enrolled in the Elfe rather than included in the Elfe birth cohort, we included 13,026 women who worked during pregnancy (72% of the cohort). Information about maternal occupations and industrial activities during pregnancy was collected by questionnaire at the maternity ward, and completed at 2-month when necessary. Using Matgéné job-exposure matrices, we assessed maternal occupational exposure to solvents. Logistic and multiple linear regressions were used to assess the association between maternal occupational solvent exposure and SGA status, birth weight, and HC. Analyses were conducted for exposure during pregnancy and also stratified by the trimester that pregnancy leave began. ResultsWe observed a higher risk of SGA newborns among mothers occupationally exposed during pregnancy to petroleum solvents (ORadjusted = 1.26; 95%CI: 1.01 to 1.57). Among women working until the third trimester of pregnancy, we observed a higher risk of SGA newborns to those occupationally exposed to oxygenated solvents (ORadjusted = 1.75; 95%CI: 1.11 to 2.75), a significantly lower birthweight for infants of mothers exposed to petroleum solvents (βadjusted = −47.37 g; −89.33 to −5.42), and a lower HC among newborns of those occupationally exposed to oxygenated solvents (βadjusted = −0.28; −0.49 to −0.07) and to chlorinated solvents (βadjusted = −0.29; −0.53 to −0.05). DiscussionOur results suggest that maternal occupational solvent exposure may influence fetal growth, especially exposure into the third trimester of pregnancy.

Obtaining of Formaldehyde Modified Tars and Road Materials on Their Basis

The process of chemical modification of tar and oxidized bitumen with formalin (a 37% aqueous solution of formaldehyde) in a hermetic container was investigated and the effectiveness of the proposed process was proven. It is shown that the most effective raw material for the process is tar, not oxidized bitumen. The expediency and impact of using different types of solvents (toluene, p-xylene and petroleum solvent, and n-octane) in the modification process were studied. It was established that the solvent should be used in the modification of oxidized bitumens, not tars. The low efficiency of the process of tar modification with formaldehyde without the use of a catalyst was proven, and it was shown that the most active catalyst in the process is sulfuric acid. The influence and optimal values of the main factors controlling the process of chemical modification of tar with formaldehyde were established, namely temperature, duration, and content of the modifier—formaldehyde. On the basis of the found regularities and optimal conditions of the modification process, samples of binding materials (of different brands) with different operational characteristics were obtained, and their comprehensive research was carried out. With the help of FTIR spectroscopy, the chemical interaction of tar with formaldehyde in the presence of an acid catalyst was confirmed. The design of the compositions of asphalt concrete mixtures using formaldehyde-modified tar was carried out, from which cylindrical samples of stone mastic asphalt (SMA-15 brand) were obtained, which were tested according to the main indicators: average density, water-saturation, compression strength at 20 and 50 °C, compression strength after water-saturation (MPa) at 50 °C.

Kinetics of dissolution of asphalt-resin-paraffin deposits when adding dispersing agents

The study is devoted to the determination of kinetic parameters of the process of asphalt-resin-paraffin deposits dissolution by oil fractions, solvents and compositions based on them. The study of the kinetics of deposits dissolution and the effect of additives on this process is relevant, as the use of solvents will reduce the cost of cleaning and repairing process equipment of refineries. A series of experiments was performed to determine the kinetic regularities of dissolution of different types of asphalt-resin-paraffin deposits in petroleum solvents of different fractional composition and the effect of dispersing agents on this process. Crude distilled oil fractions 110–1500С, 150–2000С and 140–2430С were shown to be the most effective for dissolving the asphalt-resin-paraffin deposits. The use of dispersant agents increases the degree of solubility of the components of the asphalt-resin-paraffin deposits. The kinetics of dissolution process obeys the Erofeyev-Kolmogorov equation.

Partial enzymatic cell wall disruption of Oocystis sp. for simultaneous cultivation and extraction

A green extraction process is proposed to reduce energy and petroleum solvent’s consumption while maintaining environmental safety and quality that allows multiple product recovery. The goal of the study was to generate a highly permeable cell, through the use of crude fungal enzymes, that could permit simultaneous cultivation and extraction. A novel pretreatment method is developed which combines partial enzymatic digestion of cell walls of microalgae, while maintaining their viability, thus enabling further product recovery from the same biomass and has not been reported in literature yet. Partial digestion of the cell wall was accomplished through regulation of the contact time of crude enzymes with the microalgal cells leading to a highly permeable cell that is viable and actively growing. Experimentally this was achieved through controlling the time of incubation of microalgal cells with the crude enzymes. The effects of enzymatic treatment using crude fungal enzymes from Trichoderma reesei (cellulase 10.98 ± 0.17 U/ml and amylase 20.28 ± 0.13 U/ml) were investigated on the structural properties of marine microalga Oocystis sp. Results showed over 2-fold increase in protein efflux; 41% increase in released sugars and 24% decrease in cell count after 1 h of enzyme treatment at 33% (v/v) enzyme concentration. Controlled hydrolysis of algal cells could be achieved through optimizing the contact time (1 h) of enzymes with microalgal cells which retained their viability. This was validated through FTIR, SEM, XRD and Flow Cytometric analysis. The carotenoid content increased by approximately 9% and lipid content rose by nearly 6.2%.

Comparison of VOCs Pollution Characteristics Between an Urban Site and a Background Site in Summer in Zibo

To study the differences in volatile organic compound (VOCs) pollution characteristics between an urban site and a background site in summer, ambient VOCs were monitored using an online gas chromatograph (GC) at an urban site and a background site (Mt. Lu) in Zibo in July 2020. The VOCs pollution characteristics and chemical reactivity were analyzed, and the sources of VOCs were identified using the positive matrix factorization model(PMF). The results showed that ρ(TVOC) and ρ(NOx) were higher at the urban site, but ρ(O3) was higher at the background site. Diurnal average characteristics of ρ(TVOC) and ρ(NOx) were high at night and low during the day at the urban site, and there were no obvious variation characteristics at the background site. The diurnal average characteristics of ρ(O3) were consistent at the urban and background sites, showing low level at night and high level during the day; however, the peak in the background site was later than that at the urban site. The average ρ(TVOC) at the urban site and background site were (44.9±27.5) μg·m-3 and (17.3±9.1) μg·m-3, respectively, and the mass fraction of each component was ordered as alkanes>aromatics>alkenes>alkynes in both sites. The average ozone formation potentials(OFP)were (115.5±63.1) μg·m-3 and (38.0±20.2) μg·m-3, and the contribution of each component was ordered as alkenes>aromatics>alkanes>alkynes. The respective average values of·OH radical loss rate(L·OH) were (3.9±2.3) s-1 and (1.0±0.6) s-1, with the highest contribution of alkenes and the lowest contribution of alkynes in both sites. The average values of secondary organic aerosol formation potential(SOAp) were (0.5±0.3) μg·m-3 and (0.2±0.06) μg·m-3, respectively, with aromatic being the most abundant group. According to the source appointment by the PMF model, the main source of VOCs in the urban site was traffic sources (52.4%), followed by petroleum evaporation (19.2%), solvent evaporation (17.3%), and oil and biological sources (11.1%). The source of VOCs in the background site mainly came from traffic sources (40.2%), followed by solvent evaporation (31.3%), combustion sources (19.3%), and biological sources (9.2%). Zibo City should strengthen the management and control of motor vehicle emissions, petroleum evaporation, and the use of industrial solvents.

Phytochemical Investigation and Biological Screening of Ethyl Acetate Fraction of Salvia hispanica L. Aerial Parts

Introduction: Salvia hispanica L. is an annual herbaceous plant commonly known as "Chia", native of southern Mexico and northern Guatemala. The aim of this study is isolation, identification of secondary metabolites and evaluation of biological activities of ethyl acetate fraction of Salvia hispanica L. aerial parts. Methods: Air dried powdered of Salvia hispanica L. aerial parts was extracted by maceration and fractionated using light petroleum, dichloromethane and ethyl acetate solvents. Ethyl acetate fraction was subjected to column and thin layer chromatography for isolation of secondary metabolites that are characterized by UV-Vis, FT-IR, EI-MS, 1D and 2D NMR spectral analyses. UPLC-ESI-MS/MS technique was used on the same fraction. In-vitro biological evaluation of the fraction carried out for anti-oxidant activity using DPPH assay, anti-obesityactivity using pancreatic lipase inhibitory assay,anti-diabetic activity usingα -amylase inhibition assay andanti-cancer activities usingcell viability assay. Results: Six compounds were isolated including 1,2,4,5 tetrahydroxy benzene (1), leucantho flavone (2), rhamnetin (3), apigenin-7-O-β- D-glucoside(4), rosmarinic acid (5) and kaempferol-7-O-β-D-glucoside (6). The identification of thirty seven compounds byUPLC-ESI-MS/MS analysis. A strong DPPH scavenging activity with IC50 13.11compared to ascorbic acid, anti-obesity activity with IC50 59.3 compared to orlistate, anti-diabetic activity with IC50 95.2 compared to acarbose. High cytotoxic activity against lung carcinoma, colon carcinoma and moderately cytotoxic activity against prostate carcinoma cell lines. Conclusions: Salvia hispanica L. is a strong antioxidant and anti-carcinogenic against lung and colon cancer. Key words: Anti-oxidant, Anti-obesity, Leucantho flavone, Salvia hispanica, 1,2,4,5-tetrahydroxy benzene, UPLC-ESI-MS/MS.

Characteristics and sources of volatile organic compounds during summertime in Tai'an, China

Continuous measurements of volatile organic compounds (VOCs) were conducted at an urban site in Tai'an, Shandong province of China from 15 May to 10 June 2019. The concentration of total VOCs (TVOCs) was 28.73 ± 15.20 ppbv, and oxygenated VOCs (OVOCs) comprised the dominant proportion (46.4%) among five VOC groups. The most abundant VOC species was formaldehyde, followed by propane, ethane, acetaldehyde, acetone and ethylene. Six VOC sources were identified by positive matrix factorization (PMF) model, including coal combustion (26.2%), OVOCs-related source (20.2%), liquefied petroleum gas (LPG) usage (18.9%), vehicle emission (17.1%), biogenic source (11.1%) and solvent usage (6.5%). The results of conditional bivariate probability function (CBPF) showed that LPG usage, vehicle exhaust and solvent usage were mainly affected by local emissions, while other three sources were greatly affected by regional transmission. Based on the China Ambient Air Quality Standard, O3 episode and non-O3 episode days were identified, and the concentrations of TVOCs were 32.80 ± 15.78 ppbv (O3 episode days) and 24.01 ± 14.47 ppbv (non-O3 episode days), respectively. During different O3 pollution episodes, OVOCs contributed the highest proportion to VOC concentration and ozone formation potential (OFP), while aromatics contributed the greatest potential for secondary organic aerosol potential (SOAP). Moreover, coal combustion and LPG usage were significantly associated with the increase in VOC pollution on O3 episode days.

Time resolved study of ignition of microwave discharge in liquid hydrocarbons

AbstractResults of the study of acoustic phenomena and changes in the structure of the microwave (2.45 GHz) discharge in liquid hydrocarbons in time are presented. Discharge was ignited at the tip of microwave antennas with conical or rounded ends. Petroleum solvent Nefras was chosen as representative of liquid hydrocarbons. Electret microphone and high‐speed video cameras were used to study the discharge. It is shown that the discharge is always attached to the top of the cone in the case of the conical end of the antenna whereas ignition of the discharge generates in the gas part of the reactor a set of acoustic oscillations with frequencies corresponding to the characteristic oscillations of the reactor.

Spatiotemporal Distributions of Ambient Volatile Organic Compounds in China: Characteristics and Sources

Ambient volatile organic compounds (VOCs) play a critical role in air quality as important precursors for the formation of ozone and secondary organic aerosols. The characteristics of ambient VOCs vary among different regions. In this study, characteristics and sources of VOCs from 33 sites in 32 major cities across China were compiled from field measurements and literature. The annual average VOC concentrations ranged from 6.7 to 75.0 ppbv and featured spatial variations, with a high value in northwestern China (62.7 ± 17.5 ppbv) but no significant difference among northern, central, southern, and southwestern China (32.0–36.0 ppbv). The VOC concentrations in Qingdao and Fuzhou were consistent with the background values for the region (7.6 ± 1.2 ppbv). VOC concentrations exhibited different seasonal variations across China. High concentrations occurred in winter and autumn, especially in cities in northern China, attributed to the combined contributions from weather and heating activities. The annual average chemical compositions of ambient VOCs across China were dominated by alkanes (36.5%–69.3%), followed by aromatics (7.7%–47.8%), alkenes (6.9%–53.4%), and alkynes (0.7%–15.0%). Chemical compositions also exhibited different seasonal variations across China, depending on the emission and consumption of VOCs. Vehicle exhaust, natural gas/liquefied petroleum gas, fuel combustion, and solvent usage were the dominant VOC contributors, followed by industrial, fuel evaporation, and biogenic sources. Listing VOCs as a mandatory monitoring pollutant for environmental monitoring stations in China and developing accurate source apportionment methods are critical to guide policy making and for understanding of the spatiotemporal distribution of ambient VOCs.

Photochemical ozone pollution in five Chinese megacities in summer 2018

To investigate photochemical ozone (O3) pollution in urban areas in China, O3 and its precursors and meteorological parameters were simultaneously measured in five megacities in China in summer 2018. Moderate wind speeds, strong solar radiation and high temperature were observed in all cities, indicating favorable meteorological conditions for local O3 formation. However, the unusually frequent precipitation caused by typhoons reaching the eastern coastline resulted in the least severe air pollution in Shanghai. The highest O3 level was found in Beijing, followed by Lanzhou and Wuhan, while relatively lower O3 value was recorded in Chengdu and Shanghai. Photochemical box model simulations revealed that net O3 production rate in Lanzhou was the largest, followed by Beijing, Wuhan and Chengdu, while it was the lowest in Shanghai. Besides, the O3 formation was mainly controlled by volatile organic compounds (VOCs) in most cities, but co-limited by VOCs and nitrogen oxides in Lanzhou. Moreover, the dominant VOC groups contributing to O3 formation were oxygenated VOCs (OVOCs) in Beijing and Wuhan, alkenes in Lanzhou, and aromatics and OVOCs in Shanghai and Chengdu. Source apportionment analysis identified six sources of O3 precursors in these cities, including liquefied petroleum gas usage, diesel exhaust, gasoline exhaust, industrial emissions, solvent usage, and biogenic emissions. Gasoline exhaust dominated the O3 formation in Beijing, and LPG usage and industrial emissions made comparable contributions in Lanzhou, while LPG usage and solvent usage played a leading role in Wuhan and Chengdu, respectively. The findings are helpful to mitigate O3 pollution in China.