Search Results (51)

This study investigates hazardous emissions from foundry binder systems, comparing organic resins (phenolic urethane, furan, and alkaline-phenolic) and clay-bonded green sand with inorganic alternatives (sodium silicate and geopolymer). The research was conducted at the Fundaciόn Azterlan pilot plant (Spain), involving controlled chamber tests for the production of 60 kg iron alloy castings in 110 kg sand molds. The molds were evaluated under two configurations: homogeneous systems, where both mold and cores were manufactured using the same binder (five trials), and heterogeneous systems, where different binders were used for mold and cores (four trials). Each mold was placed in a metallic box fitted with a lid and an integrated gas extraction duct. The lid remained open during pouring and was closed immediately afterward to enable efficient evacuation of casting gases through the extraction system. Although the box was not completely airtight, it was designed to direct most exhaust gases through the duct. Along the extraction system line, different sampling instruments were strategically located for the precise measurement of contaminants: volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), phenol, multiple forms of particulate matter (including crystalline silica content), and gases produced during pyrolysis. Across the nine trials, inorganic binders demonstrated significant reductions in gas emissions and priority pollutants, achieving decreases of over 90% in BTEX compounds (benzene, toluene, ethylbenzene, and xylene) and over 94% in PAHs compared to organic systems. Gas emissions were also substantially reduced, with CO emissions lowered by over 30%, NO_x by more than 98%, and SO₂ by over 75%. Conducted under the Greencasting LIFE project (LIFE 21 ENV/FI/101074439), this work provides empirical evidence supporting sodium silicate and geopolymer binders as viable, sustainable solutions for minimizing occupational and ecological risks in metal casting processes. Full article

Soil microbial communities are essential for the natural attenuation of organic pollutants, yet their ecological responses under long-term contamination remain insufficiently understood. This study examined the bacterial community structure and the abundance of dechlorinating bacteria at a decommissioned pharmaceutical-chemical site in northern Jiangsu Province, China, where the primary pollutants were dichloromethane, 1,2-dichloroethane, and toluene. Eighteen soil samples from the surface (0.2 m) and deep (2.2 m) layers were collected using a Geoprobe-7822DT system and analyzed for physicochemical properties and microbial composition via 16S rRNA gene amplicon sequencing. The results showed that the bacterial community composition was significantly shaped by the soil pH, moisture content, pollutant type, and depth. Dechlorinating bacteria were detected at all sites but exhibited low relative abundance, with higher concentrations in the surface soils. Desulfuromonas, Desulfitobacterium, and Desulfovibrio were the dominant dechlorinators, while Dehalococcoides appeared only in the deep soils. A network analysis revealed positive correlations between the dechlorinators and BTEX-degrading and fermentative taxa, indicating potential cooperative interactions in pollutant degradation. However, the low abundance of dechlorinators suggests that the intrinsic bioremediation capacity is limited. These findings provide new insights into microbial ecology under complex organic pollution, and support the need for integrated remediation strategies that enhance microbial functional potential in legacy-contaminated soils. Full article

Sulfolane, an organic solvent widely used in the petrochemical industry, has raised concerns due to its potential health risks and environmental mobility. Toxicological studies suggest that it may negatively affect human and ecological health, highlighting the need for risk assessments. Alongside sulfolane, BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) are commonly present in petrochemical operations, and their migration may be influenced by sulfolane. This study developed a gas chromatography–mass spectrometry (GC-MS) method for simultaneous analyses of sulfolane and BTEX in water. The sample preparation was designed for simplicity to allow for easy implementation without specialized equipment. The method was characterized, validated, and its ruggedness was tested through experimental design. The method was then applied to evaluate the stability of water samples under various storage conditions, and to analyze 97 real water samples collected from a contaminated site in Alberta, Canada. The results identified 17 samples with sulfolane concentrations exceeding the maximum limits for aquatic life preservation, and three samples with detectable toluene levels. These findings highlight the need for further research to better understand contamination profiles and assess associated risks. Full article

This study presented a comprehensive comparison of soil gas sampling methodologies to monitor volatile organic compounds (VOCs) at two industrial sites in northern Italy. Utilizing active sampling techniques, such as stainless-steel canisters, vacuum bottles, and sorbent tubes, alongside passive methods like low-density polyethylene (PE) membranes, sorbent pens, and Waterloo Membrane Samplers (WMS), the research examines their effectiveness under varied environmental conditions. Five field campaigns were conducted in two areas of the industrial sites characterized by BTEX and chlorinated solvent contamination. The results highlighted that active sampling, while expensive, provides real-time, high-resolution VOC concentration data, often outperforming passive methods for heavier compounds (e.g., hexachlorobutadiene). However, using the active systems in certain campaigns, challenges such as high soil humidity or atmospheric air infiltration were observed, resulting in an underestimation of the soil gas concentrations. Passive sampling systems demonstrated cost-effective, efficient alternatives, offering consistent spatial and temporal coverage. These methods showed alignment with active techniques for lighter compounds (e.g., TCE and BTEX) but faced limitations in sorbent saturation and equilibrium time for heavier VOCs (e.g., hexachlorobutadiene), requiring adjustments in exposure duration to enhance accuracy. PE samplers provided results comparable to active methods, especially for BTEX and TCE, while WMS and sorbent pens exhibited lower sensitivity for certain analytes. This underscores the importance of optimizing sampler configurations and deployment strategies. The findings emphasize the value of integrating active and passive approaches to achieve robust VOC assessments in heterogeneous subsurface environments. Full article

Although bioremediation is considered the most environmentally friendly and sustainable technique for remediating contaminated soil and water, it is most effective when combined with physicochemical methods, which allow for the preliminary removal of large quantities of pollutants. This allows microorganisms to efficiently eliminate the remaining contaminants. In addition to requiring the necessary genes and degradation pathways for specific substrates, as well as tolerance to adverse environmental conditions, microorganisms may perform below expectations. One typical reason for this is the high toxicity of xenobiotics present in large concentrations, stemming from the vulnerability of bacteria introduced to a contaminated site. This is especially true for planktonic bacteria, whereas bacteria within biofilms or microcolonies have significant advantages over their planktonic counterparts. A physical matrix is essential for the formation, maintenance, and survival of bacterial biofilms. By providing such a matrix for bacterial immobilization, the formation of biofilms can be facilitated and accelerated. Therefore, bioremediation combined with bacterial immobilization offers a comprehensive solution for environmental cleanup by harnessing the specialized metabolic activities of microorganisms while ensuring their retention and efficacy at target sites. In many cases, such bioremediation can also eliminate the need for physicochemical methods that are otherwise required to initially reduce contaminant concentrations. Then, it will be possible to use microorganisms for the remediation of higher concentrations of xenobiotics, significantly reducing costs while maintaining a rapid rate of remediation processes. This review explores the benefits of bacterial immobilization, highlighting materials and processes for developing an optimal immobilization matrix. It focuses on the following four key areas: (i) the types of organic pollutants impacting environmental and human health, (ii) the bacterial strains used in bioremediation processes, (iii) the types and benefits of immobilization, and (iv) the immobilization of bacterial cells on various carriers for targeted pollutant degradation. Full article

Two common iron oxide-bearing wastes—a drinking water treatment residual and a passive mine water treatment sludge (MWTS)—were utilised with and without modification as media in microcosm experiments to treat artificial benzene, toluene, ethylbenzene, and xylene (BTEX)-contaminated wastewater. In all cases, the removal of BTEX was observed over the 160-day experiments, with benzene being the most recalcitrant. The solubilisation of iron was observed, which, alongside the syntropic relationship between the methanogens and firmicutes, allowed several anaerobic processes to occur, including iron reduction in concert with the biodegradation of BTEX. Nitrogen sparging prior to microcosm establishment, compared to aeration, was seen to lead to the greater subsequent removal of BTEX, indicating that anaerobic conditions favoured removal. The rates of BTEX removal indicated that these iron oxide-bearing wastes, an abundant waste stream, may be an interesting candidate for cost-effective media for BTEX remediation in applications such as permeable reactive barriers. Full article

This study presents a modern mobile laboratory to monitor outdoor air quality in Bucharest, Romania, with a focus on pollutants associated with transportation. Particulate matter (PM₂.₅, PM₁₀), carbon monoxide (CO), ozone (O₃), sulfur dioxide (SO₂), nitrogen oxides (NO, NO₂), and BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) were among the significant pollutants that were examined in the lab. Meteorological variables such wind direction and speed, temperature, humidity, and solar radiation were also routinely observed in order to assess their influence on pollution levels. The study looked at two locations—a bustling city road in Bucharest and a remote community 40 kmawayin Snagov—under a range of weather conditions, including sunny, rainy, warm, and chilly days. The findings showed that the primary source of pollution in the urban area, which had significantly higher pollution levels than the rural site, was transportation. Particularly in the city, alarming concentrations of harmful particulate matter and carcinogens like benzene were found, underscoring the need for continuous air quality monitoring. The weather has a major impact on the dispersal of contaminants. Because of washout effects, rainy days decreased airborne pollutants, but sunny days showed higher pollution deposition. This study highlights the importance of outdoor air quality monitoring, particularly in urban environments, where traffic and weather have a significant impact on pollution levels. These findings provide crucial data that policymakers can utilize to implement targeted pollution control measures that protect human health. Full article

This study aimed to explore the microbial communities present in aquifer groundwater at a petrochemical refinery and their relationship with groundwater quality parameters, with a focus on common contaminants such as benzene, toluene, ethylbenzene, and dichloroethane (DCA). Groundwater samples were collected from both the source and plume regions to analyze the spatial diversity of the microbial communities utilizing 16S rRNA analysis. The study demonstrated substantial variations in microbial diversity and composition across the sampled sites. The data showed that the operational taxonomic unit count, Shannon index, and Simpson index initially rose before declining with escalating contaminant concentration, suggesting that the level of contaminants significantly influences the abundance and diversity of microbial communities in the phreatic groundwater. Moreover, through SPSS analysis, the study quantitatively established the correlation between the physiochemical characteristics of the groundwater and the microbial community structure. The study disclosed that geochemical parameters, including total alkalinity, ferrous content, and DCA, play a role in shaping the abundance and diversity of microbial communities at the phylum, class, and genus levels. This research contributes to our comprehension of the intricate interplay between microbial communities, particularly those implicated in the biotransformation of benzene and DCA, and their surrounding physiochemical milieu within contaminated zones. Full article

Oil sand tailings from bitumen extraction contain various contaminants, including polycyclic aromatic hydrocarbons, BTEX, and naphthenic acids, which can leak into surrounding environments, threatening aquatic ecosystems and human health. These tailings also contribute to environmental issues such as habitat disruption and greenhouse gas emissions. Despite these challenges, oil sand tailings hold significant potential for waste-to-resource recovery as they contain valuable minerals like rare earth elements (REEs), titanium, nickel, and vanadium. Traditional metal extraction methods are environmentally damaging, requiring high energy inputs and generating dust and harmful emissions. Furthermore, the coating of hydrocarbons on mineral surfaces presents an additional challenge, as it can inhibit the efficiency of metal extraction processes by blocking access to the minerals. This highlights the need for alternative, eco-friendly approaches. Bioleaching, which uses microorganisms to extract metals, emerges as a sustainable solution to unlock the valuable metals within oil sand tailings. This review discusses the minerals found in oil sand tailings, the challenges associated with their extraction, methods from hydrocarbon removal from minerals, and bioleaching as a potential metal recovery method. Full article

This study was conducted to investigate the presence of benzene in the ground and drinking water in the eastern Niger Delta, where multiple oil and gas production facilities are present. Samples from drinking water wells were collected for measurements of benzene, toluene, ethylbenzene, and xylenes (BTEX). Additionally, the dissolved organic carbon (DOC) concentration was determined for the first time to establish the groundwater’s total hydrocarbon and non-hydrocarbon load. The groundwater BTEX and benzene levels were up to 3904 µg/L and 3500 µg/L, respectively. DOC concentrations were up to 49 mg/L. The highest benzene concentrations were detected in wells near an underground petroleum pipeline. However, the concentrations decreased with distance from the pipeline to levels less than 0.1 µg/L. Despite benzene contamination, the aquifer has shown promising aerobic attenuation potential, having up to a 7.5 (95%) mg/L DO level and 2.11 mg/L BTEX biodegradation capacity for DO. However, the high groundwater temperature of up to 32.5 °C may weaken attenuation. The benzene and BTEX point attenuation rates ranged from 0.128 to 0.693 day⁻¹ and 0.086 to 0.556 day⁻¹, respectively. Hence, by natural attenuation alone, up to 66.5 and 85 years would be required to reach Nigeria’s groundwater benzene and BTEX remediation goals, respectively. Full article

The global concern for risk control of organic contaminated sites is becoming more and more prominent. Traditional ex situ remediation techniques are costly and damage the site, seriously destroying the soil structure and ecological functions. Therefore, in situ means of combining material injection and microbial remediation have become a potential pathway for the green, economical, and efficient remediation of contaminated sites. In this work, a 200 m² test block was selected for the coupled injection of slow-release oxygen materials and microbial agents, and long-term monitoring of groundwater was carried out. The results showed that the slow-release materials could release oxygen for a period of 90 days, which provided an oxidizing environment for microorganisms to rapidly degrade BTEX. For the pre-adapted indigenous degradation bacterial agent test group, the degradation degree of BTEX was up to 98% after 40 days of injection. The results of the application on the field scale proved the feasibility of reinforcing biostimulation for remediation of underground organic contamination through the coupled injection of slow-release oxygen materials and microbial agents. The results provided theoretical and technical support for the in situ remediation of petroleum hydrocarbon-contaminated sites. Full article

The degradation of sediments in urban environments worldwide is driven by population growth, urbanization, and industrialization, highlighting the need for thorough quality assessment and management strategies. As a result of these anthropogenic activities, benzene, toluene, ethylbenzene, xylenes, and styrene (BTEXS) are persistently released into the environment, polluting sediment. This study employed self-organizing maps (SOMs), positive matrix factorization (PMF), and Monte Carlo simulation of source-oriented health risks to comprehensively investigate sediment in an urban shallow lake in a mid-sized city in central Serbia. The results indicated a mean ∑BTEXS concentration of 225 µg/kg, with toluene as the dominant congener, followed by m,p-xylene, benzene, ethylbenzene, o-xylene, and styrene. Three contamination sources were identified: waste solvents and plastic waste due to intensive recreational activities, and vehicle exhaust from heavy traffic surrounding the lake. Both non-carcinogenic and carcinogenic health risks were below the permissible limits. However, children were more susceptible to health risks. Benzene from vehicle exhaust is the most responsible for non-carcinogenic and carcinogenic health risks in both population groups. The results of this study can help researchers to find a suitable perspective on the dynamics and impacts of BTEXS in lake sediments. Full article

BTEX (benzene, toluene, ethylbenzene, and xylenes) are widely used in pesticide manufacturing industries. Due to their high volatility and toxicity, BTEX compounds often leak during production, storage, and transportation, posing significant threats to human health and the environment. In this study, soil and groundwater samples at a chemical pesticide industrial site in southern China were collected and analyzed. Soil concentrations ranged from 0.05–142 mg/kg for benzene, 0.05–315 mg/kg for toluene, 0.05–889 mg/kg for ethylbenzene, 0.05–2800 mg/kg for m-&p-xylene, and 0.05–668 mg/kg for o-xylene. Groundwater concentrations were 0.7–340,000 μg/L for benzene, 0.9–4070 μg/L for toluene, 0.5–1900 μg/L for ethylbenzene, 1.6–6000 μg/L for m-&p-xylene, and 0.6–1500 μg/L for o-xylene. While the average concentrations were relatively low, there were numerous locations where BTEX levels significantly exceeded national soil and groundwater standards. Despite the minimal health risks from soil BTEX pollution, utilizing groundwater for drinking or bathing could result in unacceptable cancer and non-cancer risks. These findings underscore the urgent need for remediation efforts, particularly concerning benzene contamination in groundwater, to ensure the sustainable utilization of the industrial site in question. Full article

The present study analyzed the presence of the principal volatile compounds of the BTEX type (benzene, toluene, ethylbenzene, and xylene [o-, m- and p-xylene]) in samples of water from wells located at residences and gas stations in two Amazonian towns—Tracuateua and Augusto Corrêa—in the Amazon region of northern Brazil. This innovative study is extremely relevant to the Amazonian towns surveyed, given that they lack systematic policies for the environmental control of gas stations and any municipal regulations on the quality of water destined for human consumption. A combination of mass spectrometry (MS) and gas chromatography (CG) techniques was applied to analyze these contaminants in 150 samples of local groundwater collected between 2020 and 2024. One of the four BTEX compounds (toluene) was identified in seven of the samples collected (4.66% of the total) at concentrations of 0.14–2.10 µg L⁻¹. The concentrations of contaminants were low, in general. None of the water samples analyzed here presented any critical loss of water quality for human consumption according to the Brazilian legislation concerning BTEX concentrations. Neither of the two towns surveyed in the present study has remediation programs for environmental contamination. The GC-MS approach produced satisfactory results for the assessment of the contamination of underground water reserves by gas stations in both study towns. Further research (e.g., geophysical methods) will be necessary to determine the source of the contamination and its connection with the levels of toluene identified in the underground water sampled in these Amazonian towns. Full article

Benzene, toluene, ethylbenzene and xylenes, collectively known as BTEX compounds, are significant emerging contaminants in municipal wastewater. Stricter effluent quality regulations necessitate their removal, especially with concerns about organic micropollutant concentrations. Water scarcity further underscores the need for wastewater treatment to ensure safe agricultural or drinking water supplies. Although biological treatment partially reduces BTEX levels through processes like biodegradation and sorption, additional purification using physico-chemical methods is crucial for substantial reduction. This paper aims to outline plant-wide simulation methods for treating BTEX-contaminated sewage and facilitating reuse, adhering to IWA Good Modelling Practice Guidelines. The model, built upon the MiniSumo process model, incorporates equations detailing BTEX metabolism and removal kinetics, informed by an extensive literature review. Using a variant of the Benchmark Simulation Model with granular activated carbon for water reuse, the study examines strategies for improving effluent quality and minimizing operational costs. These strategies include adjusting the sludge retention time and airflow to enhance BTEX degradation and stripping, respectively, and comparing maintenance approaches for the GAC tower. Full article