Presence Of Volatile Organic Compounds Research Articles

A hybrid technology for enhancing VOC transfer in liquid desiccant dehumidifiers: Combining surfactant and internal cooling

Indoor air pollution control has increasingly focused on addressing the presence of volatile organic compounds (VOCs). In this regard, liquid dehumidification is a potential method for VOC removal. However, most of the recent studies focus on the utilization of conventional liquid desiccants and dehumidifiers without demonstrating their potential in VOC removal. To realize this potential and improve removal efficiency, a proper enhancement strategy is needed. In this paper, a hybrid technology named “surfactant + internal cooling” is proposed to enhance the VOC transfer mechanism. A theoretical model is proposed for predicting VOC transfer employing the hybrid technology presented in this study. The proposed technology is compared against other two conventional technologies in terms of removal performance, parameter distribution, and enhancement mechanism. Additionally, the impacts of some of the key parameters on the VOC removal characteristics when employing the hybrid technology are identified, and their respective distributions are characterized and investigated. The results showed that after the implementation of surfactant technology and internal cooling technology, the improvement rates compared to traditional adiabatic dehumidifiers are 22 % and 42 %, respectively. However, with the hybrid technology combining the surfactant and internal cooling, a maximum improvement rate of 63 % is reported. This enhancement can be attributed to the collaborative reduction of the Henry’s law constant by 62 % at the dual-scale level of micro-solution and macro-structure. Overall, it is demonstrated in this paper that the use of the hybrid technology can simultaneously improve the micro and macro driving forces driving the VOC transfer, enhancing the VOC removal performance. The findings of this study provide new insights to improve the performance of liquid desiccant dehumidifiers in VOC removal applications.

Volatile organic contaminants in HDPE milk bottles along the mechanical recycling value chain, revealing origins and contamination pathways

To progress towards closed-loop recycling of plastic packages it is vital to understand the origin of contaminants and to develop effective mitigation strategies. High density polyethylene (HDPE) milk bottles were sampled at nine different locations along the recycling value chain and analysed with two gas chromatography – mass spectroscopy methods to study the presence of volatile organic compounds. The total approximated concentration of volatiles reduced over time from the production of the bottles up to the cross-docking facility for the separately collected lightweight packaging waste (from about 250 to 100 ppm), as alkanes and alkenes evaporate from the bottle. A clear maximum was observed in the number of identified of volatiles and in the total approximated concentration in milk bottles at the sorted HDPE product. Here contaminants peaked that originate from the milk, from other packaging components (labels, caps, inlays), from other packages and from the surrounding atmosphere. When only the milk bottles were manually separated out from this sorted product and these were mechanically recycled, flakes were obtained that contain the least amount of volatile compounds, much less than the freshly produced bottles (about 25–50 ppm). The type of volatiles present was, however, markedly different. In the freshly produced bottles alkanes, alkenes and intentionally added anti-oxidant were found, whereas in the recycled flakes mostly contaminants were found that originated from: the milk, the other packaging components, other packages and the surrounding atmosphere. Seven different contamination pathways were discerned. The gathered knowledge facilitates the future development of food-grade recycled HDPE.

Experimental and theoretical studies on effective synergistic low-temperature removal of NO and typical volatile organic compounds (VOCs) from flue gas based on Cu@VWTi catalyst

The transition metal-modified VWTi structural catalysts hold great promise for simultaneously removing nitrogen oxides (NOx) and volatile organic compounds (VOCs) from industrial flue gases. A series of Cu@VWTi catalysts were prepared to investigate their synergistic low-temperature removal performance towards NO and typical VOCs, including toluene, benzene, chlorobenzene (CB), p-chlorotoluene (p-CT), and dichloromethane (DCM). The copper-enhanced samples prepared via ultrasound-assisted impregnation exhibited irregular globular and varying crystallinity. The catalysts displayed a typical anatase crystal structure with high TiO2 content or high dispersion of V and W species along with a certain adjustment effect on the morphology. Various controlling factors affecting the synergistic removal of NO and VOCs were evaluated. It was observed that the presence of VOCs in flue gas has weak impact on NO removal, except for the waste incineration using the Cu@VWTi catalyst. However, a high initial NO concentration had an adverse effect on VOCs removal. Impressively, the optimized copper-doped catalyst (5 wt% Cu loaded of smelting plant and coal-fired power plant used catalyst) exhibited excellent performance for p-CT, toluene and DCM removal of 95.0%, 99.6% and 100% at 300 °C, respectively. The toluene and p-CT conversion efficiencies were highest over the catalyst used in the smelting plant after Cu loading, surpassing the benzene conversion efficiency. Cu@VWTi demonstrated excellent performance for p-CT, toluene, and DCM removal at 250 °C. Although 5 wt% Cu loading on the catalysts significantly enhanced the stability and anti-jamming of VOCs removal, as well as their tolerance to both SO2 and water vapor. The enhanced mechanism of Cu decoration attributed to the enhanced intensity of acid sites and the stable relative proportion of Oads/Olatt species in the used 5% Cu loaded catalyst due to the redox cycles of Cu and V species. Compared with Brønsted acid, which primarily adsorbs NH4+, Lewis acid mainly adsorbs gas phase acid and forms coordinated NH3 in gas phase. The bonding between toluene and the Cu site was enhanced with an adsorption energy of −130.9 kJ mol−1, as well as the cracking adsorption of the CH2Cl2 on the Ti site with a bonding energy of −436.7 kJ mol−1, both indicating strong chemical adsorption. The first step of dechlorination and demethylation was thermodynamically and kinetically favorable for DCM and toluene decomposition.

Application of hyperspectral imaging for characterization of VOC-induced historical glass corrosion

Hyperspectral imaging (HSI) provides high-resolution recording of the spectral information at every spatial point (pixel) of an object throughout a contiguous range of wavelengths. This paper reports an attempt at exploring the application of HSI in transmittance mode for the identification and quantification of corrosion in transparent historical glass, which is difficult to identify by visual inspection. This was done using model glass samples mimicking historical composition and subjected to artificial ageing in the presence of volatile organic compounds. Hyperspectral images of unaged and aged glass samples were recorded with two cameras covering visible and near infrared (VNIR, 400–1000 nm) and short-wave infrared range (SWIR, 1000–2500 nm) using a custom-made HSI set-up in transmission mode. The HSI data were further processed to classify and visualize corrosion in different ageing environments and ageing periods. The results show that HSI can be employed as a valuable tool to assess glass corrosion at early stages, especially by analysing the SWIR spectral region—which shows the water absorption by the glass matrix due to corrosion.

Experimental assessment and artificial neural network modeling of dynamic and steady-state methane biofiltration in the presence of volatile organic compounds

Experimental assessment and artificial neural network modeling of dynamic and steady-state methane biofiltration in the presence of volatile organic compounds

Effect of high DHA and ARA fortification on lipid oxidation of infant formula powder

ABSTRACT Our objective was to assess the impact of fortified high-dose docosahexaenoic acid (DHA) and arachidonic acid (ARA) in infant formula powders (IFs) on stability. We compared and evaluated the stability of IFs containing high and low doses of DHA and ARA over a 6-month storage period at 37°C. While most formulations showed minimal changes in unsaturated fatty acid content of during storage, significant losses of DHA and ARA were observed in some high-dose formulations. Furthermore, this study noted consistent trends in the changes of vitamin C and vitamin E across both formula groups. Notably, the high-dose group formulas exhibited a higher presence of volatile organic compounds (VOCs) during storage, along with a more pronounced increase in thiobarbituric acid-reactive substance values (TBARS). In conclusion, the inclusion of high doses of DHA and ARA in IFs may compromise their oxidative stability.

Artificial Olfactory System for Distinguishing Oil-Contaminated Soils

Oil-contaminated soils are a major environmental problem for Kazakhstan. Oil spills or leaks lead to profound changes in the physical and agrochemical properties of the soil and the accumulation of hazardous substances. Whilst there are many remote sensing techniques and complex laboratory methods for oil spill detection, developing simple, reliable, and inexpensive tools for detecting the presence of pollutants in the soil is a relevant research task. The study aims to research the possibilities of an electronic nose combining a chemical sensor array with pattern recognition techniques to distinguish volatile organic compounds from several types of hydrocarbon soil pollutants. An electronic nose system was assembled in our laboratory. It includes eight gas metal oxide sensors, a humidity and temperature sensor, an analog-digital processing unit, and a data communication unit. We measured changes in the electrical conductivity of sensors in the presence of volatile organic compounds released from oil and petroleum products and samples of contaminated and uncontaminated soils. The list of experimental samples includes six types of soils corresponding to different soil zones of Kazakhstan, crude oil from three oil fields in Kazakhstan, and five types of locally produced fuel oil (including gasoline, kerosene, diesel fuel, engine oil, and used engine oil). We used principal component analysis to statistically process multidimensional sensor data, feature extraction, and collect the volatile fingerprint dataset. Pattern recognition using machine learning algorithms made it possible to classify digital fingerprints of samples with an average accuracy of about 92%. The study results show that electronic nose sensors are sensitive to soil hydrocarbon content. The proposed approach based on machine olfaction is a fast, accurate, and inexpensive method for detecting oil spills and leaks, and it can complement remote sensing methods based on computer vision.

Influence of humidity in the alteration of unstable glasses

AbstractThe control of humidity between certain limits is essential to avoid the alteration of historical objects, such as unstable historical glasses. However, the usual limits can be altered due to the presence of volatile organic compounds. This work presents the results of the exposure of soda, potash, and mixed‐alkali silicate glasses to neutral and acidic (formic) atmospheres with ∼30%, ∼70%, and ∼100% relative humidity. The hygroscopic capacity of the glass was analyzed by gravimetry, and the surface alteration was evaluated by infrared spectroscopy, optical microscopy, and ion chromatography. In all glasses, the alteration begins with alkali ions’ lixiviation followed by the silica network's hydrolytic attack. The results showed that soda and mixed‐alkali silicate glasses exhibit similar behavior, while the potash‐lime one experienced the fastest degradation due to its composition. Results also confirmed that high humidity increased the alteration rate causing a higher hygroscopicity and reactivity of glasses. Finally, acidic environments promoted the ion‐exchange reaction at high humidity, accelerating the lixiviation of alkaline ions and promoting the diffusion of water into the glass network.

Impact of soot deposits on waste gas-to-electricity conversion in a TiO2/WO3-based photofuel cell

An unbiased photo-fuel cell (PFC) is a device that integrates the functions of a photoanode and a cathode to achieve simultaneous light-driven oxidation and dark reduction reactions. As such, it generates electricity while degrading pollutants like volatile organic compounds (VOCs). The photoanode is excited by light to generate electron-hole pairs, which give rise to a photocurrent, and are utilized to oxidise organic pollutants simultaneously. Here we have systematically studied various TiO2/WO3 photoanodes towards their photocatalytic soot degradation performance, PFC performance in the presence of VOCs, and the combination of both. The latter thus mimics an urban environment where VOCs and soot are present simultaneously. The formation of a type-II heterojunction after the addition of a thin TiO2 top layer over a dense WO3 bottom layer, improved both soot oxidation efficiency as well as photocurrent generation, thus paving the way towards low-cost PFC technology for energy recovery from real polluted air.

Case Report: Presence of volatile organic compounds (VOCs) in the OPU-oocyte searching room and its effect on equine in vitro embryo production

Volatile organic compounds (VOCs) are hydrocarbon-based organic compounds with known detrimental effects on mammalian in vitro embryo development. Only strict air quality monitoring guarantees optimal culture conditions. Our VOC-free laboratory receives bovine and equine oocytes collected by OPU from nine different stations, to produce bovine and equine embryos in vitro by in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) respectively. During fourteen consecutive equine OPU sessions, the mean blastocyst rate obtained from the oocytes collected at one of the stations were the lowest (10.4 %), when compared to the others (31.8 %). The quality of the air was suspected and passive absorption badges were placed for 5 days near where oocytes were searched for and further processed before transport (Old Room). The badges were returned for chromatographic analysis and the results indicated a poor air quality. Alcohol compounds exceeded by two-fold the recommended threshold for offices and living rooms (Ethanol: 335 ppb and Isopropanol: 129 ppb). The oocyte searching room was then moved to a different location within the station (New Room), to allow restricted access and improved air quality conditions. In vitro embryo production rates were monitored for anothereleven OPU sessions after moving the oocyte searching room to the new location. The OPU, ICSI and in vitro culture (IVC) conditions remained the same throughout the experiment. Briefly, oocytes were collected by ovum pick up (OPU) and transported to the laboratory overnight in 5 ml tubes, containing in vitro maturation (IVM) medium (IVF-Bioscience, UK) in a portable incubator at 38.2 ˚C and 5 % CO2. After 32 h of IVM, ICSI was performed on all MII oocytes and injected oocytes were cultured for nine days in Global medium (Cooper Surgical, Denmark), at 38˚C, 5 % CO2 and 5 % O2. The oocyte maturation, cleavage and blastocyst rates obtained from oocytes selected and packed in the Old vs. New Room were analyzed by ANOVA and compared by Fisher's exact test. There was no significant difference between the maturation (51.06 % vs. 48.94 %) and cleavage rates (68.75 % vs. 82.61 %) using oocytes selected and packed in the Old vs. New Room respectively. Blastocyst rates significantly improved after moving the oocyte search room to the new location: 10.42 % (5/48) for Old Room vs. 39.13 % (9/23) for New Room (P<0.01). The present work demonstrates the importance of controlling the conditions in the OPU oocyte collection room, with evidence suggesting an effect of VOCs on in vitro embryo development.

Toxicity evaluation of landfill leachate after treatment by simple distillation using Danio rerio biomarkers

Landfill leachate is an effluent characterized by a great heterogeneity in its composition, and may contain the most diverse types of organic and inorganic contaminants. Therefore, the leachate needs an efficient treatment before being released into the environment. For this, a lot of treatment processes are being developed and studied, such as simple distillation. To evaluate the efficiency of the treatment, the use of ecotoxicological assays with fish is a useful tool to determine the effects on the aquatic environment of the residual compounds present after the treatment. The aim of this study was to evaluate the efficiency of the simple distillation process in a landfill leachate. For this, in addition to the physical-chemical characterization, the presence of volatile organic compounds (VOC), metals, pharmaceuticals, hormones, and pesticides in the raw (RL) and distilled raw leachate (DRL) was evaluated. Finally, biochemical biomarkers were evaluated in Danio rerio fish exposed to different concentrations of RL and DRL. High concentrations of chemical (COD) and biochemical (BOD) demand for oxygen, nitrogen compounds, sulfates, and chlorides were detected, in addition to fatty acids, long-chain alkanes, alcohols and esters, heavy metals, and six pharmaceuticals. After the distillation process, most of these compounds were reduced by more than 90% and some were removed completely. The biomarkers showed greater changes in the groups exposed to LR and were influenced by the exposure concentration. Thus, the treatment of simple distillation of the leachate proved to be efficient because, in addition to reducing/removing the contaminants, it also reduced the toxicity in D. rerio.

Development of self-cleaning cement mortar exposed to indoor and outdoor environment

The presence of volatile organic compounds and other gaseous contaminants in both the indoor and outdoor environments causes the building's aesthetics and human health to deteriorate. It is vital to clean the indoor and outdoor environments to address this difficult problem. The development of self-cleaning concrete will provide a remedy for this issue. Self-cleaning characteristics can be incorporated in to cement with the addition of photocatalytic substances, such as Titanium Dioxide (TiO2). This enables the preservation of building surfaces and the decrease of air pollution in the environment. In the present study, TiO2 in cement mortar containing barites powder is utilized to evaluate the self-cleaning behavior and setting time of cement mortar. The self-cleaning experiment was conducted in two ways: coating mortar samples with dye and dipping mortar samples in Methylene Blue dye. The samples of mortar are then subjected to sunlight and LED light. The efficacy of self-cleaning was measured by measuring the concentration of Methylene Blue and observing it physically. In all situations, the self-cleaning ability of mortar samples was greater when exposed to sunlight than LED light. Moreover, coated samples were more efficient than immersion samples. Higher TiO2 dosage has demonstrated enhanced performance.

Outer membrane vesicles of Dinoroseobacter shibae transport a volatile aldehyde

Outer Membrane Vesicles (OMVs) of the Gram-negative marine bacterium Dinoroseobacter shibae, a member of the Roseobacteraceae, were investigated for the presence of volatile organic compounds (VOCs). Extracts of vesicles were analyzed by gas chromatography/mass spectrometry (GC/MS). In these analyses the short fatty acid (Z)-5-dodecenoic acid (1) and the related, more volatile aldehyde (Z)-5-dodecenal (8) were identified as VOCs of the OMVs. The aldehyde 8 has not yet been reported before from bacteria. Due to their possible function as signaling molecules, both compounds were tested for Quorum Sensing (QS) inhibition in a bioassay against the QS sensor strain Pseudomonas putida F117 (pKRC12) responsive to long-chain N-acylhomoserine lactones, the effectors of the sensor. Both compounds showed QS inhibitory activity. The potential function of VOCs in OMVs which has not been observed previously is discussed.

Continuous monitoring of volatile organic compounds through sensorization. Automatic sampling during pollution/odour/nuisance episodic events

Volatile organic compounds (VOCs) are a highly diverse class of chemical contaminants and between 50 and 300 of them may be found in ambient air. In urbanized areas, VOCs are emitted from industrial activities, as well as from vehicle-related and combustion sources. VOCs outdoors can be detected in a broad range of concentrations, usually varying seasonally. The presence of VOCs at relatively high concentrations has been related to poor air quality, discomfort and odorous nuisances. Additionally, they can have negative health effects to the human organism. Hence, in locations where recurrent sporadic situations of high VOCs levels take place, episodic samples' evaluation is necessary instead of 24 h or longer sampling period's evaluations. The use of commercially available metal oxide semiconductor gas sensors for a continuous monitoring of VOCs concentrations in outdoor air is an interesting and innovative technology. Additionally, the use of these sensors for the activation of a VOCs sampler when episodic events of nuisance/odorous annoyance occur was successfully evaluated. The sensor activation is induced by higher VOCs concentrations from a wide number of VOC chemical families. Two sensor stations, developed at our laboratory and provided with sampling pumps, were located in the municipality of Santa Margarida i els Monjos (Catalunya, Spain) in January 2021. The stations started recording data continuously from two different types of VOCs sensors, temperature, relative humidity and pressure in 1.5-min periods. Automatic VOCs sampling was conducted, using multi-sorbent bed tubes, during the months of June–July when the sensors electronic values exceeded a set point value. Samples were analysed through TD-GC/MS. TVOC concentrations in episode samples ranged between 78-669 and 12–159 μg m−3 in Site 1 and Site 2, respectively. Although TVOC concentrations were not high in all cases, relevant concentrations of chloroform were observed, especially in Site 1, with concentrations ranging from 19 to 159 μg m−3.

Layer-by-Layer Deposited Multi-Modal PDAC/rGO Composite-Based Sensors.

Different environmental parameters, such as temperature and humidity, aggravate food spoilage, and different volatile organic compounds (VOCs) are released based on the extent of spoilage. In addition, a lack of efficient monitoring of the dosage of pesticides leads to crop failure. This could lead to the loss of food resources and food production with harmful contaminants and a short lifetime. For this reason, precise monitoring of different environmental parameters and contaminations during food processing and storage is a key factor for maintaining its safety and nutritional value. Thus, developing reliable, efficient, cost-effective sensor devices for these purposes is of utmost importance. This paper shows that Poly-(diallyl-dimethyl ammonium chloride)/reduced Graphene oxide (PDAC/rGO) films produced by a simple Layer-by-Layer deposition can be effectively used to monitor temperature, relative humidity, and the presence of volatile organic compounds as indicators for spoilage odors. At the same time, they show potential for electrochemical detection of organophosphate pesticide dimethoate. By monitoring the resistance/impedance changes during temperature and relative humidity variations or upon the exposure of PDAC/rGO films to methanol, good linear responses were obtained in the temperature range of 10-100 °C, 15-95% relative humidity, and 35 ppm-55 ppm of methanol. Moreover, linearity in the electrochemical detection of dimethoate is shown for the concentrations in the order of 102 µmol dm-3. The analytical response to different external stimuli and analytes depends on the number of layers deposited, affecting sensors' sensitivity, response and recovery time, and long-term stability. The presented results could serve as a starting point for developing advanced multi-modal sensors and sensor arrays with high potential for analytical applications in food safety and quality monitoring.

Enhanced detection of low concentration volatile organic compounds using advanced doped zinc oxide sensors.

Pure zinc oxide nanoparticles, as well as those doped with 3% calcium, aluminum, and gallium, were synthesized using a sol-gel method and then deposited onto an alumina substrate for sensing tests. The resulting nanoparticles were characterized using a variety of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), UV-VIS-NIR absorption spectroscopy, and photoluminescence (PL) measurements, to examine their structural, morphological, and optical properties. The prepared nanoparticles were found to have the hexagonal wurtzite structure of ZnO with a P63mC space group. The UV-Vis-IR spectra showed that the samples are highly absorbent in the UV range, while the PL spectra confirmed the presence of many defects in the ZnO structure, such as oxygen vacancies and zinc interstitials. The doped samples exhibited more defects than the pure sample. SEM images of the deposited film surface showed agglomerates with a spherical shape and confirmed the nanometer scale size of our prepared samples, as corroborated by the TEM images. The EDX spectra indicated the high purity of the ZnO deposited films, with a high presence of Zn and O and the presence of the doped elements (Ca, Al, and Ga) in each doped sample. Sensing tests were performed on ZnO, Ca3%-doped ZnO (C3ZO), Al3%-doped ZnO (A3ZO), and Ga3%-doped ZnO (G3ZO) sensors in the presence of volatile organic compounds (VOCs) gases such as ethanol, formaldehyde, methanol, and acetone at low concentrations. The sensors exhibited high responses to low ppm level concentrations of the VOCs gases. At a low operational temperature of 250 °C, the C3ZO sensor had the highest response to 5 ppm of ethanol, methanol, and formaldehyde gases compared to the pure and other doped sensors. Additionally, the A3ZO sensor exhibited the highest response to acetone gas. In conclusion, our findings suggest that the doping of zinc oxide can enhance the low concentration detection of VOCs gases, with the C3ZO and A3ZO sensors showing the highest response to specific gases.

Hansen Solubility Parameters (HSPs): A Reliable Tool for Assessing the Selectivity of Pristine and Hybrid Polymer Nanocomposites in the Presence of Volatile Organic Compounds (VOCs) Mixtures

AbstractPolymeric materials are widely employed for monitoring volatile organic compounds (VOCs). Compared to other sensitive materials, polymers can provide a certain degree of selectivity, based on their chemical affinity with organic solvents. The addition of conductive nanoparticles within the polymer layer is a common practice in recent years to improve the sensitivity of these materials. However, it is still unclear the effect that the nanoparticles have on the selectivity of the polymer membrane and vice versa. The current work proposes a methodology based on the Hansen solubility parameters, for assessing the selectivity of both pristine and hybrid polymer nanocomposites. The impedance response of thin polydimethylsiloxane (PDMS) films is compared to the response of hybrid polymer films, based on the addition of multi‐walled carbon nanotubes (MWCNTs). With the addition of just 1 wt.% of MWCNTs, fabricated sensors showcased a significant improvement in sensitivity, faster response times, as well as enhanced classification of non‐polar analytes (&gt;22% increase) compared to single PDMS layers. The methodology proposed in this work can be employed in the future to assess and predict the selectivity of polymers in single or array‐based gas sensors, microfluidic channels, and other analytical devices for the purpose of VOCs discrimination.

Comparative evaluation of bacterial and fungal removal of indoor and industrial polluted air using suspended and packed bed bioreactors.

The abatement of indoor volatile organic compounds (VOCs) represents a major challenge due to their environmental risk, wide nature and concentration variability. Biotechnologies represent a cost-effective, robust and sustainable platform for the treatment of hazardous VOCs at low and fluctuating concentrations. However, they have been scarcely implemented for indoor air purification. Thus, little is known about the influence of the reactor configuration or the VOC nature and concentration variability on the removal, resilience and the microbial population of bioreactor configurations susceptible to be implemented, both in indoors and industrial environments. The present study aims at comparing the removal performance of four VOCs with different hydrophobicity and molecular structure -acetone, n-hexane, α-pinene and toluene-at two inlet concentrations (5 and 400 mg m−3), which mimics the concentrations of contaminated indoor and industrial air. To this aim a stirred tank, flat biofilm and latex-based biocoated flat bioreactor were comparatively evaluated. The results demonstrated the superior performance of the stirred tank reactor for the removal of hydrophilic VOCs at high inlet concentrations, which achieved removals >99% for acetone and toluene. At low concentrations, the removal efficiencies of acetone, toluene and α-pinene were >97% regardless of the bioreactor configuration tested. The most hydrophobic gas, n-hexane, was more efficiently removed in the flat biofilm reactor without latex. The microbial community analyses showed that the presence of VOCs as the only carbon and energy source didn't promote the growth of dominant bacterial members and the populations independently evolved in each reactor configuration and operation mode. The fungal population was more diverse in the biofilm-based bioreactors, although, it was mainly dominated by uncultured fungi from the phylum Cryptomycota.

Occurrence, health risk, and removal efficiency assessment of volatile organic compounds in drinking water treatment plants (DWTPs): An investigation of seven major river basins across China

The presence of volatile organic compounds (VOCs) in drinking water has the potential to harm human health and undermine public confidence. Hence, this is the first study to comprehensively investigate concentrations of 25 VOCs in the 146 drinking water treatment plants (DWTPs) in 24 cities across seven major river basins (including the Yangtze River, Yellow River, Haihe River, Songhua River, Liaohe River, Pearl River, and Huaihe River), China. The occurrence, human health, and olfactory risks, as well as removal efficiency of VOCs in DWTPs, were evaluated. The findings revealed that 21 VOCs were detected, with concentrations ranging from not detected to 99.10 μg/L (trichloromethane). The maximum concentrations of trichloroacetaldehyde (54.90 μg/L) and trichloromethane (99.10 μg/L) exceeded China's regulated values (GB 5749–2006/2022). The concentrations of VOCs and water quality parameters showed a strong positive correlation. Human health and olfactory risks assessment indicated that drinking water exposures do not pose carcinogenic (CR < 10−6) and non-carcinogenic (HI < 1) health risks to consumers, nor do olfactory and taste hazards (OHI <1). However, it is worth mentioning that due to the relatively high concentrations of some VOCs (trichloroacetaldehyde, acrolein, and trichloromethane), the health risk posed by them are still a major concern that needs to be addressed. Finally, the removal efficiency of VOCs is low in 146 DWTPs (mean of 12.91%–76.79%). Taken together, adding advanced treatment procedures for the purpose of improving the removal efficiency of pollutants of DWTPs in the future is an urgent priority.

Home is Where the Pipeline Ends: Characterization of Volatile Organic Compounds Present in Natural Gas at the Point of the Residential End User.

The presence of volatile organic compounds (VOCs) in unprocessed natural gas (NG) is well documented; however, the degree to which VOCs are present in NG at the point of end use is largely uncharacterized. We collected 234 whole NG samples across 69 unique residential locations across the Greater Boston metropolitan area, Massachusetts. NG samples were measured for methane (CH4), ethane (C2H6), and nonmethane VOC (NMVOC) content (including tentatively identified compounds) using commercially available USEPA analytical methods. Results revealed 296 unique NMVOC constituents in end use NG, of which 21 (or approximately 7%) were designated as hazardous air pollutants. Benzene (bootstrapped mean = 164 ppbv; SD = 16; 95% CI: 134–196) was detected in 95% of samples along with hexane (98% detection), toluene (94%), heptane (94%), and cyclohexane (89%), contributing to a mean total concentration of NMVOCs in distribution-grade NG of 6.0 ppmv (95% CI: 5.5–6.6). While total VOCs exhibited significant spatial variability, over twice as much temporal variability was observed, with a wintertime NG benzene concentration nearly eight-fold greater than summertime. By using previous NG leakage data, we estimated that 120–356 kg/yr of annual NG benzene emissions throughout Greater Boston are not currently accounted for in emissions inventories, along with an unaccounted-for indoor portion. NG-odorant content (tert-butyl mercaptan and isopropyl mercaptan) was used to estimate that a mean NG-CH4 concentration of 21.3 ppmv (95% CI: 16.7–25.9) could persist undetected in ambient air given known odor detection thresholds. This implies that indoor NG leakage may be an underappreciated source of both CH4 and associated VOCs.