Volatile Volatile Organic Compounds Research Articles

Superamphiphobic coating prepared via a two-step spray method: An effective coating for reducing VOCs emission from crude oil tank

In the petrochemical industry, crude oil adhesion in storage tanks leads to volatilization of volatile organic compounds (VOCs), causing environmental harm and economic losses. Superamphiphobic coatings show promise in addressing this issue, but current options face challenges like complexity, limited durability, and poor corrosion resistance. This work introduces a durable and corrosion-resistant superamphiphobic coating on Q235 carbon steel using the "paint + adhesives" two-step spray method. The first layer comprises polytetrafluoroethylene (PTFE) and epoxy resin (E-44), while the second layer consists of fluorine modified silica nanoparticles (F-SiO2). The numerous and homogeneously dispersed fluorine on the coating imparts excellent liquid-repelling properties for both water and crude oil, with a water contact angle of 164.1 ± 2.4° and a sliding angle of 1.1 ± 0.1°, as well as a crude oil contact angle of 172.1 ± 0.9° and a sliding angle of 2.5 ± 0.5°. Systematic stability tests confirm the coating's mechanical and chemical stability, suggesting its potential in practical applications. Importantly, a crude oil tank with our superamphiphobic coating can reduce non-methane hydrocarbon (NMHC) volatilization by 77.4 % ± 7.8 % compared to an uncoated tank. This research provides a superamphiphobic coating to reduce crude oil loss and VOC volatilization in petrochemical enterprises, showing significant contribution to environmental sustainability.

Aqueous VOCs in complex water environment of oil exploitation sites: Spatial distribution, migration flux, and risk assessment

Pollution of the aqueous environment by volatile organic compounds (VOCs) has caused increasing concerns. However, the occurrence and risks of aqueous VOCs in oil exploitation areas remain unclear. Herein, spatial distribution, migration flux, and environmental risks of VOCs in complex surface waters (including River, Estuary, Offshore and Aquaculture areas) were investigated at a typical coastal oil exploitation site. Among these surface waters, River was the most polluted area, and 1,2-Dichloropropane—which emerges from oil extraction activities—was the most prevalent VOC. Positive matrix factorization showed that VOCs pollution sources changed from oil exploitation to offshore disinfection activities along River, Estuary, Offshore and Aquaculture areas. Annual volatilization of VOCs to the atmosphere was predicted to be ∼34.42 tons, and rivers discharge ∼23.70 tons VOCs into the Bohai Sea annually. Ecological risk assessment indicated that Ethylbenzene and Bromochloromethane posed potential ecological risks to the aquatic environment, while olfactory assessment indicated that VOCs in surface waters did not pose an odor exposure risk. This study provides the first assessment of the pollution characteristics of aqueous VOCs in complex aqueous environments of oil exploitation sites, highlighting that oil exploitation activities can have nonnegligible impacts on VOCs pollution profiles.

Absorption of volatile organic compounds (VOCs) by polymer tubing: implications for indoor air and use as a simple gas-phase volatility separation technique

Abstract. Previous studies have demonstrated volatility-dependent absorption of gas-phase volatile organic compounds (VOCs) to Teflon and other polymers. Polymer–VOC interactions are relevant for atmospheric chemistry sampling, as gas–wall partitioning in polymer tubing can cause delays and biases during measurements. They are also relevant to the study of indoor chemistry, where polymer-based materials are abundant (e.g., carpets and paints). In this work, we quantify the absorptive capacities of multiple tubing materials, including four nonconductive polymers (important for gas sampling and indoor air quality), four electrically conductive polymers and two commercial steel coatings (for gas and particle sampling). We compare their performance to previously characterized materials. To quantify the absorptive capacities, we expose the tubing to a series of ketones in the volatility range 104–109 µg m−3 and monitor transmission. For slow-diffusion polymers (e.g., perfluoroalkoxy alkane (PFA) Teflon and nylon), absorption is limited to a thin surface layer, and a single-layer absorption model can fit the data well. For fast-diffusion polymers (e.g., polyethylene and conductive silicone), a larger depth of the polymer is available for diffusion, and a multilayer absorption model is needed. The multilayer model allows fitting solid-phase diffusion coefficients for different materials, which range from 4×10-9 to 4×10-7 cm2 s−1. These diffusion coefficients are ∼ 8 orders of magnitude larger than literature values for fluorinated ethylene propylene (FEP) Teflon film. This enormous difference explains the differences in VOC absorption measured here. We fit an equivalent absorptive mass (CW, µg m−3) for each absorptive material. We found PFA to be the least absorptive, with CW ∼ 105 µg m−3, and conductive silicone to be the most absorptive, with CW ∼ 1013 µg m−3. PFA transmits VOCs easily and intermediate-volatility species (IVOCs) with quantifiable delays. In contrast, conductive silicone tubing transmits only the most volatile VOCs, denuding all lower-volatility species. Semi-volatile species (SVOCs) are very difficult to sample quantitatively through any tubing material. We demonstrate a system combining several slow- and fast-diffusion tubing materials that can be used to separate a mixture of VOCs into volatility classes. New conductive silicone tubing contaminated the gas stream with siloxanes, but this effect was reduced 10 000-fold for aged tubing, while maintaining the same absorptive properties. SilcoNert (tested in this work) and Silonite (tested in previous work) steel coatings showed gas transmission that was almost as good as PFA, but since they undergo adsorption, their delay times may be humidity- and concentration-dependent.

Adult-Onset Transcriptomic Effects of Developmental Exposure to Benzene in Zebrafish (Danio rerio): Evaluating a Volatile Organic Compound of Concern.

Urban environments are afflicted by mixtures of anthropogenic volatile organic compounds (VOCs). VOC sources that drive human exposure include vehicle exhaust, industrial emissions, and oil spillage. The highly volatile VOC benzene has been linked to adverse health outcomes. However, few studies have focused on the later-in-life effects of low-level benzene exposure during the susceptible window of early development. Transcriptomic responses during embryogenesis have potential long-term consequences at levels equal to or lower than 1 ppm, therefore justifying the analysis of adult zebrafish that were exposed during early development. Previously, we identified transcriptomic alteration following controlled VOC exposures to 0.1 or 1 ppm benzene during the first five days of embryogenesis using a zebrafish model. In this study, we evaluated the adult-onset transcriptomic responses to this low-level benzene embryogenesis exposure (n = 20/treatment). We identified key genes, including col1a2 and evi5b, that were differentially expressed in adult zebrafish in both concentrations. Some DEGs overlapped at the larval and adult stages, specifically nfkbiaa, mecr, and reep1. The observed transcriptomic results suggest dose- and sex-dependent changes, with the highest impact of benzene exposure to be on cancer outcomes, endocrine system disorders, reproductive success, neurodevelopment, neurological disease, and associated pathways. Due to molecular pathways being highly conserved between zebrafish and mammals, developmentally exposed adult zebrafish transcriptomics is an important endpoint for providing insight into the long term-effects of VOCs on human health and disease.

Chemical fingerprinting of volatile organic compounds from asphalt binder for quantitative detection

Asphalt material is an irreplaceable material in road construction. However, it releases VOCs (Volatile Organic Compounds), which do cause pollution to the surrounding environment, during its full life cycle, especially in high-temperature paving stage and summer service time. Asphalt VOCs release mechanism and effective emission reduction technologies are therefore urgently needed. The chemical analysis of VOCs from asphalt binder always invariably excludes a vast number of compounds of unknown relevance, making the quantitative analysis lower data accuracy. In order to address this problem, fingerprint database was developed and introduced in this study, with the detected VOCs data from 104 kinds of asphalt binders. The analysis parameters, including fingerprint components and calibration curves were optimized through quantitative study. With the help of a self-developed fingerprint database, the calculation formulas of single VOC and total released VOCs were established for quantitative analysis of VOCs from asphalt binder. In addition, the influencing mechanism of heating temperature and asphalt types on VOCs volatilization characteristic were explored to achieve emission reduction in asphalt industry.

Temperature dependency of VOCs release characteristics of asphalt materials under varying test conditions

Asphalt pavement is increasingly used in paving and roofing. However, the release of volatile organic compounds (VOCs) from asphalt harm both the environment and humans. Various methods were applied to characterize the VOCs for better understanding and inhibiting. However, asphalt VOCs have huge heating temperature dependency, which makes the asphalt VOCs' characterization complicated. In this research, three kinds of heating conditions, thermal gravimetric (TG) analyzer, pyrolysis (PY) analyzer, and thermal desorber (TD), were compared to determine the temperature dependency of VOC release characteristics. Gas chromatography and mass spectrometer (GC-MS) were then coupled for VOC detection. Results indicated that the TG heating condition can surely simulate the volatilization of VOCs from some asphalt that is not in contact with air (no oxygen) during the actual construction process, while PY and TD represent the substances released by the asphalt due to the boiling point at a certain temperature and under the actual construction process, respectively. The components detected by TG heating condition are both large and small molecules, while PY and TD heating condition will detect large molecules or small molecules, respectively. The VOC composition results under various heating conditions reflect the chemical reaction law of asphalt molecules in the heating process. When heating asphalt binders to a higher temperature, macromolecular substances will gradually crack and oxidize into small molecular substances, sulfides and nitrides. With the increase of temperature, the change trend of VOC components under different conditions is different.

Distribution characteristics and health risk assessment of volatile organic compounds in the groundwater of Lanzhou City, China.

Volatile organic compounds (VOCs) typically exist in the aqueous environment due to global anthropogenic activities. The distribution and contaminated profile (or characteristics) of VOCs in the groundwater of Lanzhou, China, were investigated in this study. Groundwater samples were collected from 30 sampling points in December 2015, and a total of 17 VOCs were analyzed by purge and trap gas chromatography-mass spectrometry. Thirteen types of VOCs were detected at 29 sampling points in the study area. Of these, dichloromethane and toluene, which were found at 22 sampling points, had the highest detection frequency (73.3%), followed by benzene (66.7%), 1,2-dichloroethane (50%), and xylenes (50%). The highest average concentration among the detected VOCs was found for chloroform (5151.5μg/L). The spatial distribution of VOC contamination in four major urban areas of Lanzhou and the variation in VOC concentration caused by land use transitions were also analyzed. The results showed that Xigu district was the most polluted area in Lanzhou, mainly due to land use for industrial proposes. On the contrary, the samples for Anning district showed lower VOC concentrations because of better groundwater quality, which is associated with the absence of manufacturing industries in this region. The health risk assessment model developed by the United States Environmental Protection Agency was employed in this study to evaluate safety for drinking water use. This study found that despite considering the volatilization of VOCs from water due to heating, six sampling points (G05 in Qilihe district; G07 and G09 in Xigu district; G16, G17, and G15 in Chengguan district) showed non-carcinogenic risks, ranging from 1.63 to 14.2, while three points (G16 in Chengguan district, and G10 and G07 in Xigu district) exhibited high carcinogenic risks for human health, ranging from 2.94 × 10-4 to 6.85 × 10-4. Trichloroethylene, tetrachloroethylene, and 1,2-dichloroethylene were identified as the dominant VOCs, presenting high non-carcinogenic risk. 1,2-dichloroethane and vinyl chloride were the primary factors for high carcinogenic risk. The high-risk areas were concentrated in Xigu and Chengguan districts, suggesting the need to alert the relevant local government departments.

Rationale for Soil‐Gas Sampling to Improve Vapor Intrusion Risk Assessment in China

Rationale for Soil‐Gas Sampling to Improve Vapor Intrusion Risk Assessment in China

Preparation of a new high-efficiency resin deodorant from coal gasification fine slag and its application in the removal of volatile organic compounds in polypropylene composites

Deodorizing materials are often restricted from large-scale industrial production due to the high preparation cost. By utilizing the simple acid leaching technology, this study made use of the coal gasification fine slag (FS) as raw material to prepare a cost effective FS-based deodorant (FSD) with a specific surface area of 393 m2 g−1 and a pore volume of 0.405 cm3 g−1. The propane adsorption test on FSD showed the maximum adsorption capacity to be as high as 121.61 mg g−1 at 273 K. The partition coefficient values at 10% and 100% breakthrough (BT) for FSD to adsorb propane were 1.5 × 10−3 and 3.2 × 10−4 mol kg−1 Pa−1, respectively. Furthermore, the FSD was applied in the removal of volatile organic compounds (VOCs) pollutants from polypropylene resin (PP). It showed that the deodorizing effect of the FSD was nearly three times as good as the commonly used zeolite deodorants, which was able to decrease 50 percent of the VOCs volatilization amount in PP resin. Moreover, the FSD can better strengthen the mechanical properties of PP resin. This work provides a new method for the industrial production of deodorants as well as a new direction for the recycle of coal gasification wastes.

Rethinking hydrocarbons build-up on urban roads: A perspective on volatilisation under global warming scenarios

Stormwater is viewed as an alternative resource to mitigate water shortages. However, stormwater reuse is constrained due to the presence of many toxic pollutants such as hydrocarbons. Effective mitigation requires robust mathematical models for stormwater quality prediction based on an understanding of pollutant processes. However, the rise in global temperatures will impose changes to pollutant processes. This study has proposed a new perspective on modelling the build-up process of hydrocarbons, with a focus on volatile organic compounds (VOCs). Among organic compounds, VOCs are the most susceptible to changes as a result of global warming due to their volatility. Seven VOCs, namely, benzene, toluene, ethylbenzene, para-xylene, meta-xylene, ortho-xylene and styrene in road dust were investigated. The outcomes are expected to lay the foundation to overcoming the limitations in current modelling approaches such as not considering the influence of temperature and volatility, on the build-up process. A new conceptualisation is proposed for the classical build-up model by mathematically defining the volatility of VOCs in terms of temperature. Uncertainty in the re-conceptualised build-up model was quantified and was used to understand the build-up patterns in the future scenarios of global warming. Results indicated that for the likely scenarios, the variability in VOCs build-up gradually increases at the beginning of the dry period and then rapidly increases after around seven days, while the build-up reaches a near-constant value in a shorter dry period, limiting the variability. These initial research outcomes need to be further investigated given the expected impacts of global warming into the future.

Assessment of the chemical-physical variables affecting the evaporation of organic compounds from aqueous solutions in a sampling wind tunnel

The aim of this work is the evaluation and the analysis of the different chemical-physical variables that affect the emission of volatile organic compounds (VOC) and odours from passive liquid area sources inside a wind tunnel, which is typically used for emission sampling. Three different compounds (acetone, butanol and ethanol), having different volatilization properties (e.g., boiling point, solubility), were studied in solution with water at different concentrations. The following physical parameters affecting the VOC volatilization in the Wind Tunnel system were evaluated: the velocity of the air flowing through the device, in a range from 0.01 to about 0.05 m/s, and the temperature of both the liquid source and the sweep air flow, in a range from 12 °C to 42 °C. The experimental results were compared with the existing volatilization models available in literature. In most cases the proposed theoretical model predicts well the experimentally measured concentration. Some discrepancies were observed for lower velocities and also by moving from the room temperature (20 °C); and those were discussed by making some considerations about the volatilization phenomenon. Moreover, the study clearly shows that it is not the gas phase temperature that controls the emission, but the temperature of the liquid phase, due to the effect of the latter on the vapour pressure of the compound, which is the main driving force of the phenomenon.

Influence of Environmental Factors and Vehicle Factors on VOC Volatilization Characteristics in Automobiles

From the two aspects of external environmental factors and vehicle factors, this paper studies the influence of in-car temperature, humidity, vehicle type, vehicle mileage, vehicle exhaust displacement and other factors on the harmful volatile organic compounds (VOC) in the automobiles. The research results show that: in terms of external environmental factors, the increase of temperature and relative humidity in the car will cause the in-car VOC concentration to increase, and the temperature has a more significant influence on the VOC concentration in the car; being in area with poor environment and serious exhaust emissions for a long time will increase the VOC concentration in the car; when the natural wind speed increases, the concentration of VOC pollutants in the car gradually decreases. In terms of vehicle factors, the VOC concentration in high-end cars is significantly higher than that in low-end cars, and the VOC concentration of new cars is higher than that of old cars. As the car age and mileage increase, the VOC concentration in the car begins to decrease. The vehicle exhaust displacement is proportional to the VOC concentration in the vehicle, and the interior space is inversely proportional to the VOC concentration. The influence of the change in the interior space on the harmful VOC concentration is relatively small.

Biofiltration of benzo[α]pyrene, toluene and formaldehyde in air by a consortium of Rhodococcus erythropolis and Fusarium solani: Effect of inlet loads, gas flow and temperature

Volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) are air contaminants with serious effects on human health. They include compounds with very different physicochemical properties, ranging from low to high volatility and low to high hydrophobicity. The objective of this research is to assess the feasibility of the simultaneous abatement of formaldehyde, a soluble and slightly polar VOC, toluene a hydrophobic and volatile VOC and benzo[α]pyrene (BaP), a representative PAH in a biofiltration reactor inoculated with the fungi Fusarium solani and the bacteria Rhodococcus erythropolis. Results obtained at an extended range of inlet loads: 3.7 to 447.7, 9.0 to 273.1 and 6.9 to 247.4gm−3h−1 of toluene, formaldehyde and BaP, respectively, show that the elimination capacity and removal efficiencies of the contaminants were largely independent of each other. Moreover, the system can accommodate a fivefold increase in inlet gas flow maintaining removal efficiencies close to 60% for all the contaminants tested when the inlet loads of contaminants were kept constant. The most dramatic decrease in elimination capacity and removal efficiency in the system was obtained by changing the temperature of the system, where a decrease from 25°C to 17°C reduced the formaldehyde removal efficiency from 67% to 43%. BaP and toluene removal efficiencies were less affected by the decrease in system’s temperature. This study shows the high flexibility of a biofiltration system inoculated with F. solani and R. erythropolis for the abatement of toluene, formaldehyde and BaP.

Knowledge-based planning of groundwater treatment trains for an efficient drinking water supply system in urban areas

This paper presents knowledge-based planning of the most appropriate treatment schemes for drinking water supply (DWS) systems, jointly applying statistical tools and experimental tests. Milan City was chosen as the case study, its DWS system being composed of more than 20 DWS units, widespread in the urban area. First, multivariate statistical techniques (factor analysis and cluster analysis) were applied to groundwater monitoring data, to identify specific contaminations of the captured groundwater and their spatial distribution. In detail, eight typical compositions of captured groundwater and their distribution in DWS units were identified, leading to the selection of different treatment processes to be adopted in DWS units. Then, process performances were experimentally evaluated on representative groundwater samples. Heterotrophic denitrification was tested at pilot-scale on groundwater contaminated by nitrate, identifying optimal operating and design parameters for complying with regulation limits. Granular activated carbon (GAC) adsorption was tested at laboratory-scale for the removal of volatile organic compounds (VOCs) and pesticides, present in various ratios in groundwater samples: removal efficiencies were obtained and the occurrence of competition phenomena was highlighted. Air stripping was tested at pilot-scale for removing the most volatile VOCs (trichloroethylene, tetrachloroethylene), highlighting its usefulness as pre-treatment before adsorption to increase GAC lifetime.

Predicting the lifetime of organic vapor cartridges exposed to volatile organic compound mixtures using a partial differential equations model

ABSTRACTIn this study, equilibria, breakthrough curves, and breakthrough times were predicted for three binary mixtures of four volatile organic compounds (VOCs) using a model based on partial differential equations of dynamic adsorption coupling a mass balance, a simple Linear Driving Force (LDF) hypothesis to describe the kinetics, and the well-known Extended-Langmuir (EL) equilibrium model. The model aims to predict with a limited complexity, the BTCs of respirator cartridges exposed to binary vapor mixtures from equilibria and kinetics data obtained from single component. In the model, multicomponent mass transfer was simplified to use only single dynamic adsorption data. The EL expression used in this study predicted equilibria with relatively good accuracy for acetone/ethanol and ethanol/cyclohexane mixtures, but the prediction of cyclohexane uptake when mixed with heptane is less satisfactory. The BTCs given by the model were compared to experimental BTCs to determine the accuracy of the model and the impact of the approximation on mass transfer coefficients. From BTCs, breakthrough times at 10% of the exposure concentration t10% were determined. All t10% were predicted within 20% of the experimental values, and 63% of the breakthrough times were predicted within a 10% error. This study demonstrated that a simple mass balance combined with kinetic approximations is sufficient to predict lifetime for respirator cartridges exposed to VOC mixtures. It also showed that a commonly adopted approach to describe multicomponent adsorption based on volatility of VOC rather than adsorption equilibrium greatly overestimated the breakthrough times.

Measurement and prediction of desorption behavior of five volatile organic compounds (acetone, n-hexane, methanol, toluene, and n-decane) from activated carbon for supercritical carbon dioxide regeneration

Measurement and prediction of desorption behavior of five volatile organic compounds (VOCs) (acetone, n-hexane, methanol, toluene, and n-decane) from activated carbon by using supercritical carbon dioxide regeneration were studied. Measurements of the desorption behavior were performed with a fixed bed method at temperatures from 313 to 353K and pressures from 10.0 to 15.0MPa. The measured desorption rates varied greatly for each VOC, which could be attributed to differences in two properties, affinity of VOCs for activated carbon and the volatility of VOCs. The measured desorption rates increased with increasing pressure and decreasing temperature, which could be explained by increasing CO2 density. A kinetic model was applied to correlate the desorption behavior. The model demonstrated satisfactory correlations of the desorption behavior with only one fitting parameter. Generalization of the fitting parameter to predict the desorption behavior were also investigated. The proposed prediction model could roughly represent the desorption behavior of VOCs over a wide range of supercritical carbon dioxide conditions.

Distribution of volatile organic compounds (VOCs) in surface water, soil, and groundwater within a chemical industry park in Eastern China.

This paper focuses on the distribution of volatile organic compounds (VOCs) in the surface water, soil, and groundwater within a chemical industry park in Eastern China. At least one VOC was detected in each of the 20 sampling sites, and the maximum number of VOCs detected in the surface water, groundwater, and soil were 13, 16, and 14, respectively. Two of the 10 VOCs with elevated concentrations detected in surface water, groundwater, and soil were chloroform and 1,2-dichloroethane. The characteristics of VOCs, which include volatility, boiling point, and solubility, could significantly affect their distribution in surface water, soil, and groundwater. However, due to the direct discharging of chemical industry wastewater into surface water, higher concentrations of VOCs (except chloroform) were detected in surface water than in soil and groundwater. Fortunately, the higher volatility of VOCs prevents the VOCs from impacting groundwater, which helps to maintain a lower concentration of VOCs in the groundwater than in both surface water and soil. This is because pollutants with relatively higher boiling points and lower solubilities have higher detection frequencies in soil, and contaminants with relatively lower boiling points and higher solubilities have higher detection frequencies in water, notably in surface water.

A headspace needle-trap method for the analysis of volatile organic compounds in whole blood

Needle trap devices (NTDs) are a relatively new and promising tool for headspace (HS) analysis. In this study, a dynamic HS sampling procedure is evaluated for the determination of volatile organic compounds (VOCs) in whole blood samples. A full factorial design was used to evaluate the influence of the number of cycles and incubation time and it is demonstrated that the controlling factor in the process is the number of cycles. A mathematical model can be used to determine the most appropriate number of cycles required to adsorb a prefixed amount of VOCs present in the HS phase whenever quantitative adsorption is reached in each cycle. Matrix effect is of great importance when complex biological samples, such as blood, are analyzed. The evaluation of the salting out effect showed a significant improvement in the volatilization of VOCs to the HS in this type of matrices. Moreover, a 1:4 (blood:water) dilution is required to obtain quantitative recoveries of the target analytes when external calibration is used. The method developed gives detection limits in the 0.020–0.080μgL−1 range (0.1–0.4μgL−1 range for undiluted blood samples) with appropriate repeatability values (RSD<15% at high level and <23% at LOQ level). Figure of merits of the method can be improved by using a smaller phase ratio (i.e., an increase in the blood volume and a decrease in the HS volume), which lead to lower detection limits, better repeatability values and greater sensibility. Twenty-eight blood samples have been evaluated with the proposed method and the results agree with those indicated in other studies. Benzene was the only target compound that gave significant differences between blood levels detected in volunteer non-smokers and smokers.

Gas-phase and Transpiration-driven Mechanisms for Volatilization through Wetland Macrophytes

Natural and constructed wetlands have gained attention as potential tools for remediation of shallow sediments and groundwater contaminated with volatile organic compounds (VOCs). Wetland macrophytes are known to enhance rates of contaminant removal via volatilization, but the magnitude of different volatilization mechanisms, and the relationship between volatilization rates and contaminant physiochemical properties, remain poorly understood. Greenhouse mesocosm experiments using the volatile tracer sulfur hexafluoride were conducted to determine the relative magnitudes of gas-phase and transpiration-driven volatilization mechanisms. A numerical model for vegetation-mediated volatilization was developed, calibrated with tracer measurements, and used to predict plant-mediated volatilization of common VOCs as well as quantify the contribution of different volatilization pathways. Model simulations agree with conclusions from previous work that transpiration is the main driver for volatilization of VOCs, but also demonstrate that vapor-phase transport in wetland plants is significant, and can represent up to 50% of the total flux for compounds with greater volatility like vinyl chloride.

Predicting VOC Concentration Measurements: Cognitive Approach for Sensor Networks

Volatile organic compounds (VOCs) belong to special pollutants included in Kyoto protocol and in its updated versions. They are responsible for great and dangerous air pollution. The volatility of VOCs make them difficult to be computed and to be measured by means of appropriate sensors in terms of accuracy. Nowadays different methods have been adopted and approved by specific authorities. One of the most important is EPA25 issued by the American Environmental Protection Agency. As a matter of fact, EPA25 only works on set of complete data. In case of noncomplete set of data, we mean missing data issue due to different troubles, namely dysfunction concerning networks of sensors, thermal drifts, etc., EPA25 as well as other methods are not able to overcome the above issue that affects the prediction and the reliability. This research proposes an alternative and effective way, based on cognitive approach, to process VOC data delivered by a network of sensors by using a mixed genetic algorithm with an additional fuzzy-based procedure. A comparison with other techniques based on neural networks is also envisaged. The proposed modified genetic algorithm offers the best accuracy.