Contaminant Emissions Research Articles

A comparative evaluation of dark fermentative bioreactor configurations for enhanced hydrogen production.

Energy from renewable resources has been growing in popularity, which ultimately helps reduce emissions of greenhouse gases (GHGs) and contaminants. Since hydrogen (H2) has a higher combustion production of energy than hydrocarbon fuels, it has been identified as a clean, sustainable, and environmentally friendly energy source. There are several benefits to producing biohydrogen (bioH2) from renewable sources, including lower cost and increased sustainability. Among the bioH2 production processes, dark fermentation supports commercialization and scale-up for industrial applications. This paper considers the various bioreactors, such as anaerobic sequencing batch, continuous stirred, up-flow, fixed-bed, and membrane reactors, and their operational approaches for bioH2 production. This review paper also performs the bibliometric analysis method to identify historical and current developments in a particular field of reactor configuration studies. Furthermore, the main variables influencing reactor performance and methods for increasing process efficiency considering economic and environmental aspects are addressed. The results revealed that continuously stirred reactors are widely utilized for bioH2 production as a cost-effective reactor configuration. Moreover, the membrane bioreactors and fixed-bed reactors areyielded higher bioH2 performance than other configurations. Nevertheless, high energy consumption and costs have presented the need for further development of reactors. Consequently, future recommendations to solve the critical problems faced in reactor configurations, the gaps in the literature, and the points that need improvement were comprehensively reported.

Computational evaluation of micropores wetting effect on the removal process of CO2 through the membrane contactor

In the current years, gas–liquid membrane contactors (GLMCs) have been introduced as a promising, versatile and easy-to-operate technology for mitigating the emission of major greenhouse contaminants (i.e., CO2 and H2S) to the ecosystem. This paper tries to computationally study the role of membrane pores wettability on the removal performance of CO2 inside the HFMC. To fulfill this purpose, a mathematical model based on finite element procedure (FEP) has been employed to solve the momentum and mass transport equations in the partial-wetting (50% wetting of micropores) and non-wetting (0% wetting of micropores) modes of membrane during operation. Additionally, a comprehensive simulation was ensembled to predict the results. In this research, 2-amino-2-methyl-l-propanol (AMP) has been employed as a relatively novel alkanolamine absorbent to separate CO2 form CO2/N2 mixture. Analysis of the results implied that the wetting of membrane micropores significantly deteriorated the removal efficiency due to the enhancing mass transfer resistance towards transferring CO2 (75% in the non-wetting mode > 8% considering 50% wetting of micropores).

Active phytoextraction of toluene shifts the microbiome and enhances degradation capacity in hybrid poplar.

Hybrid poplars are widely recognized for their effectiveness in remediating subsurface aromatic hydrocarbon contaminants, including benzene, toluene, ethylbenzene, and xylene isomers (BTEX). While BTEX compounds are frequently found in the transpiration streams of poplars at contaminated sites, the microbial dynamics within these trees, particularly in response to hydrocarbon exposure, remain underexplored. This study utilized high-throughput amplicon sequencing to investigate the trunk microbiome in hybrid poplars at a field-scale toluene phytoremediation site. Across the plant growth season (spring to late summer), we observed a significant seasonal increase in bacterial diversity and richness, particularly in trees located in areas with the highest groundwater and in planta toluene concentrations. During late summer, the microbiomes of these trees were enriched with hydrocarbon-degrading taxa, including Acinetobacter, Pseudomonas, Burkholderia, Sandaracinobacter, and Allorhizobium-Rhizobium, and exhibited enhanced capacities for aerobic toluene degradation based on functional predictions. These findings reveal selective pressures exerted by hydrocarbons on endophytic microbial communities and underscore their role in mitigating volatile contaminant emissions. This study advances our understanding of microbial dynamics in phytoremediation systems and highlights the potential for leveraging endophytes to optimize contaminant degradation.

Evolution of research on air emissions from agricultural activities: A comprehensive review.

Air pollutant emissions from the agricultural sector are among the most critical issues affecting human health and the environment. This sector releases a complex mixture of biological, microbial, and inorganic contaminants into the air from land preparation, crop production, fertilization, harvesting, biomass burning, machinery use, livestock production, manure management, waste management, and deforestation. This article aims to identify the evolution and global research trends related to air contaminant emissions, specifically from the agricultural sector. This study systematically analyzed the knowledge map derived from 4016 scientific publications from 1990 to 2023. From an evolutionary perspective, the bibliometric and networking analysis revealed a consistent increase in scientific publications over the past 34years, with the contribution of 117 countries, more than 1600 authors, and 1300 journals. Additionally, it sheds light on the most studied pollutants, measurement techniques, and modeling employed to comprehend and mitigate the impact of these pollutants on yield, human health, biodiversity, and climate change. Furthermore, the research facilitates the identification of emerging air pollutants considering agricultural activities such as crop production, waste crop management, livestock production, manure management, deforestation, and land change use. These findings underscore the evolution of the research, identifying the main topics of interest, the emerging topics, and the future of research on air pollutant emissions.

What makes the synergy between pollution and carbon emission control effective? Based on an evaluation of the carbon emissions trading pilot policy

Abstract To accomplish clean air and carbon peaking and neutrality goals in the new development stage, it is essential to synergize air contamination and carbon emission reduction. This research assesses the synergistic effect between air contamination and carbon emission reduction of the carbon emissions trading (CET) pilot policy in China using the difference-in-differences (DID) model. The results demonstrate that, first, this policy has a dual impact by considerably reducing both carbon emissions and PM2.5 emissions. Second, the pilot policy can decrease carbon emissions through "pollution-to-carbon" synergistic control effect, which enables the incentive and restraint functions to be strengthened for trading carbon emissions. Nevertheless, the synergistic control effect of "carbon-to-pollution" is not significant since the replacement effect produced by investment pressure. Third, the synergy between air contamination and carbon emission management in pilot areas substantially reduces pollution emissions, suggesting that a greater degree of synergistic control generates more effective incentive or restraint effect.

Is soil contamination a missing driver of soil heterotrophic respiration in land surface models? A study case with copper –

Land Surface Models (LSMs) are crucial elements of Earth System Models used to estimate the effects of anthropogenic greenhouse gas (GHG) emissions on Earth's climate. Nevertheless, as well as land use change and direct GHG emissions, anthropogenic activities are also associated with contaminant emissions and depositions. Although contamination has a recognized impact on soil processes such as GHG emissions, soil contamination is currently not considered as an important process to consider into LSMs.In this study we hypothesized that soil contamination has significant impact on soil CO2 emissions such as heterotrophic respiration (Rh). To this end, we analyzed how soil contamination may account for residuals of modeled Rh from 11 LSMs as compared to Rh products derived from observations over Europe. We used generalized least squared mixed models to evaluate the primary factors driving of the model residuals. Among contaminants, we focused on copper (Cu), which is widely used in industry or agriculture, causing significant diffuse contamination. Additionally, research demonstrated a strong correlation between soil Rh and Cu availability to soil fauna and various soil pedological and climatic parameters. Hence, we completed our analysis by including pedo-environmental parameters and by analyzing Rh against a proxy of bioavailable Cu.Our findings indicate that Cu is a non-negligible variable in explaining the Rh models inaccuracy considering either total or free Cu forms. Therefore, it can be concluded that Cu should not be disregarded as a key factor in predicting Rh.

Ten years of monitoring pharmaceuticals and pesticides in the aquatic environment nearby a solid-waste treatment plant: Historical data, trends and risk assessment.

The emission of contaminants of emerging concern (CECs) from wastewater treatment plants has been extensively studied; however, less attention has been paid to municipal solid waste treatment plants (MSWTPs), which can also be a potential source for CECs into surface water (SW) and groundwater (GW) ecosystems. In this work, the environmental impact of a MSWTP located in the province of Castelló, Spain, was studied along a period of ten years (from 2012 to 2022). A total of 173 water samples (including SW and GW) collected from the surrounding of this plant were monitored for 93 compounds (pharmaceuticals and pesticides) by using liquid chromatography coupled to tandem mass spectrometry with triple quadrupole. This study reveals the presence of several pharmaceuticals (e.g. primidone, gabapentin, azithromycin, clarithromycin, tramadol), particularly in GW samples collected near areas related to composting and storage of biostabilized material. The presence of antibiotic residues in GW raises concerns about the potential development of antimicrobial resistance. In addition, agricultural activities in the study area emerge as potential contributor to GW pollution by pesticides, as the MSWTP is located in an important agricultural area where citrus is the predominant crop. Some compounds that are currently prohibited for agricultural use (e.g. atrazine, simazine, chlorpyrifos) were also found, which highlights the importance of continuing their monitoring to assess their long-term environmental impacts. Several pesticide and pharmaceutical compounds exceeded the threshold values established by the EU groundwater directive. Therefore, a hazard assessment for GW ecosystems and for humans drinking contaminated GW resources was conducted. Our data indicated that some organophosphate insecticides (i.e., chlorpyrifos, carbofuran, pyridaphention) may pose high risks for groundwater crustaceans, while the risks for the human population were considered to be very low.

Evaluating the impacts of printing operations on indoor air quality in a printing press

PurposeBuilding operations and human activities indoors continuously affect air quality, contaminating the air and sometimes exceeding permissible limits which can be health threatening either in the short or long time. This implies a need for strict awareness and compliance with air quality standards, particularly in workplaces prone to air contaminants emissions. This study aims to evaluate printing-related pollutant concentrations and their effects on indoor air quality (IAQ). The study investigated a printing press's total volatile organic compounds (TVOC), particulate matter (PM), carbon monoxide and carbon dioxide emissions.Design/methodology/approachThis study used mainly an experimental research design supported by physical assessment by identifying the major printing-related pollutants, assessing the existing situation and measuring pollutant concentration levels using literature reviews, walkthrough inspections and experiments, respectively. The measurements were conducted in two scenarios: with and without printing activities, and the results were compared with relevant standards and guidelines.FindingsThe outcomes indicate that TVOC concentration reaches 120 ppb during printing and binding activities, exceeding the 75 ppb acceptable limit based on the time-weighted average. The PM2.5 concentrations reach 49 µg/m3 and PM10 up to 150 µg/m3, exceeding acceptable levels given by the US Environmental Protection Agency (EPA), which are 35 µg/m3 and 150 µg/m3 for PM2.5 and PM10, respectively. These high concentrations of TVOC and PM indicate a significant risk to the health of building occupants, particularly those with respiratory conditions. PM concentrations do not exceed permissible levels when no printing or bookbinding occurs, suggesting that printing-related activities can contribute to elevated TVOC and PM concentrations.Social implicationsThe social implication of the study lies in its ability to promote awareness among workers and improve their well-being which in turn relates to productivity. The study outcome could also encourage businesses to adopt more responsible environmental and social practices as part of corporate social responsibility practices.Originality/valueThe study's findings, which highlight the need for improved ventilation in printing halls, have the potential to significantly benefit building system designers, facility managers, policymakers and decision-makers. By providing information and theoretical support, the research can help integrate policies that regulate IAQ by reducing pollutant concentrations. This protects workers' health and helps update and enforce stricter IAQ regulations for industrial operations.

Multiphase flow modelling of gas migration from a hypothetical integrity-compromised petroleum well in the peace region of North-eastern British Columbia, Canada

Well-integrity failure occurs in a small subset of petroleum wells, resulting in release of fugitive gas into intersected geologic formations. Released fugitive gas from geoenergy systems is a growing environmental concern that can contaminate groundwater aquifers and emit greenhouse gases (GHGs) to atmosphere. Currently, the roles of well-cement quality and properties of intersected geologic formations on the environmental outcomes of well-integrity failure is poorly understood. To advance understanding, we numerically modelled a hypothetical fugitive methane release from a petroleum well intersecting the Sunset Paleovalley aquifer system in Northeast British Columbia, Canada. We simulate a 10-year release and migration of fugitive gas into a two dimensional, two-phase, two-component advective flow field with the subsurface properties informed by field and laboratory data. We evaluate the effects of cement quality, gas release depth, and geologic heterogeneity on fugitive-gas containment or emission by defining and/or evaluating three key numbers: a) emission-retention ratio (ERR), b) well integrity index (WII), and c) fugitive gas mobility ratio (MR) over relevant spatiotemporal scales. We show that ERR and WII capture the bifurcated impacts of fugitive gas from petroleum wells, including groundwater contamination and atmospheric emissions. A WII close to one reduces vertical fugitive-gas migration along the well bore, fosters lateral migration into intersected geologic materials and significantly limits GHG emissions to atmosphere. MR and ERR values show fugitive-gas migration and fate are primarily controlled by the casing annulus cement quality, particularly when fugitive gas is released at shallow depths. We conclude that the quality of petroleum-well cement is among the parameters controlling the migration pathways, impacts, and fate of fugitive-gas release.

Arsenic Reduces Methane Emissions from Paddy Soils: Insights from Continental Investigation and Laboratory Incubations.

Arsenic (As) contamination and methane (CH4) emissions co-occur in rice paddies. However, how As impacts CH4 production, oxidation, and emission dynamics is unknown. Here, we investigated the abundances and activities of CH4-cycling microbes from 132 paddy soils with different As concentrations across continental China using metagenomics and the reverse transcription polymerase chain reaction. Our results revealed that As was a crucial factor affecting the abundance and distribution patterns of the mcrA gene, which is responsible for CH4 production and anaerobic CH4 oxidation. Laboratory incubation experiments showed that adding 30 mg kg-1 arsenate increased 13CO2 production by 10-fold, ultimately decreasing CH4 emissions by 68.5%. The inhibition of CH4 emissions by As was induced through three aspects: (1) the toxicity of As decreased the abundance and activity of the methanogens; (2) the adaptability and response of methanotrophs to As is beneficial for CH4 oxidation under As stress; and (3) the more robust arsenate reduction would anaerobically consume more CH4 in paddies. Additionally, significant positive correlations were observed between arsC and pmoA gene abundance in both the observational study and incubation experiment. These findings enhance our understanding of the mechanisms underlying the interactions between As and CH4 cycling in soils.

Bacterial contamination and greenhouse gas emissions: A randomised study of reuse versus single-use of infusion-set components for intravenous anaesthesia.

Reusing anaesthesia infusion-set components may reduce the climate impact from plastic waste and discarded medications. Infusion-set contents can be shielded from patient contact by single use of an infusion line fitted with dual antireflux valves, preventing retrograde entry of microorganisms, and eliminating the risk for patient-to-patient cross-contamination. However, infusion-set contamination from compromised aseptic handling could affect quality of care. To determine the prevalence of infusion-set bacterial contamination and compare the climate effects, we randomised operating rooms scheduled for total intravenous anaesthesia to handle procedures by infusion-set reuse or single-use. Both methods used dual single-use antireflux valves. The primary outcome was infusion-set bacterial contamination assessed by aerobic culture of infusion-set fluid collected after each procedure. The secondary outcome was CO 2 emissions (CO 2 -eq) estimated by life cycle assessment of component and medication use. To assess feasibility of detecting an inter-method difference in bacterial contamination, an interim analysis was planned after including at least 150 procedures per group. After allocating 54 operating rooms per method, 189 and 159 procedures of reuse and single use were included. Reuse permitted a median of three procedures per infusion set (range 1 to 8). Positive cultures occurred in two procedures per method [mean (95% CI)]; prevalence 1.15% (0.03 to 2.27); relative risk of reuse versus single use 0.84 (0.12 to 5.93), P = 0.861. As prespecified, inclusion was stopped due to futility. The median (95% CI) per-procedure climate emissions were 0.43 (0.41 to 0.47) and 1.39 (1.37 to 1.40) kg CO 2 -eq for reuse and single-use respectively; difference -0.96 (-0.99 to -0.93), P < 0.0005. The main sources for climate emissions were production of infusion-set components and waste handling. We conclude that the prevalence of bacterial contamination was low for both methods. A much larger study would be needed to detect an inter-method difference. Reuse of infusion-set components allowed significantly reduced intravenous anaesthesia climate emissions.

Impacts of alternative fuel combustion in cement manufacturing: Life cycle greenhouse gas, biogenic carbon, and criteria air contaminant emissions

Waste products destined for landfills with high calorific value are increasingly being explored for potential use in a variety of industries. One example is the potential use of these wastes in cement kilns to reduce greenhouse gas (GHG) emissions from cement production. This study develops a cradle-to-gate life cycle assessment (LCA) model to estimate the GHG emissions, criteria air contaminants (CAC), and the impact of biogenic carbon accounting methods in biomass-containing alternative fuels (AFs) on life cycle GHG emissions when replacing natural gas with AFs at a cement facility. The proposed AF mixture includes landfill wastes like construction and demolition waste, asphalt shingles, tire fluff, carpet, textiles, and plastics. While many LCAs assume the biogenic fraction's climate impact is carbon-neutral, its actual effects depend on a range of new methods being proposed to account for the climate impacts associated with biogenic carbon. The findings of this study demonstrate a reduction of approximately 7–13% in life cycle GHG emissions. The preliminary estimates suggest that the change to CACs will likely not be materially different from the current use of natural gas. It also emphasizes the importance of accounting for the biogenic fraction in biomass-based AFs, indicating a potential overall reduction of up to 7.2% in life cycle GHG emissions when the biogenic fraction is treated as carbon-neutral. While factoring in the benefits of shorter rotation and longer storage periods results in a 12.7% reduction in life cycle GHG emissions. The LCA model developed in this study holds the potential for broad application among cement facilities that are considering fossil to alternative fuels as part of their GHG emission reduction strategies.

Short-term temporal variability of volatile contaminant concentrations in soil gas related to soil-atmosphere interface dynamics: Two case studies in the Veneto region (Italy).

The study of the variability of soil gas concentrations is crucial for defining effective monitoring and remediation strategies and for the risk assessment related to the emission of vapors from the subsurface. The traditional soil gas monitoring strategy consists of seasonal surveys based on short-time-averaged sampling. Soil gas monitoring results are often used to assess the risk associated with the emission of volatile contaminants from the subsurface, using models mainly based on molecular diffusion and therefore assuming continuous emission from the soil. At two contaminated sites located in the Veneto region (Italy), continuous monitoring using a photoionization detector, pressure gauges, and an ultrasonic anemometer was used to relate soil gas variability to surface and subsurface physical parameters. At both sites a cyclic diurnal variation of volatile organic compounds concentration in soil gas was observed, correlated with the variation of several meteorological parameters and in particular with the variation of the differential pressure between soil and atmosphere and the buoyancy vertical flux. These findings question the reliability of the conventional methodology employed in the collection and assessment of soil gas data. Integr Environ Assess Manag 2024;20:2023-2032. © 2024 SETAC.

An integrated model for flexible simulation of biomass combustion in a travelling grate-fired boiler

Grate-fired boiler is of considerable interest for burning biomass owing to its reduced sensitivity to variations in fuel composition and size. However, grate-fired technology exhibits unsatisfactory performance in terms of combustion efficiency, contaminant emissions, and flame stability. CFD modelling can provide reasonable optimizations to overcome these drawbacks and ultimately achieve clean and efficient energy production. Conventional approach simulates the fuel-bed and freeboard combustion separately using an in- and over-bed coupling procedure, where data of the gases leaving from the packed-bed top and the radiative heat flux emitted by the high-temperature flame onto the bed cannot be interacted in real-time. This may cause distinct deviations in the calculations. In this paper, a three-dimensional (3D) full-scale integrated model is developed for the simulation of grate-fired boiler, in which the intensive combustion of both the freeboard and fuel-bed is solved in one scheme using the Eulerian-Lagrangian method. The gas phase is considered as a continuous medium and calculated by the Eulerian model, while the solid particles are considered as a discrete phase and tracked via the Lagrangian method. The reliability of the model is well verified through various field measurements and observations. Results shows that the key parameters are non-uniformly distributed along the grate width, i.e., the aerodynamic and combustion environment is poor at the vicinity of water-cooled walls compared with that at the furnace center. This results in a significant lag in volatile gases release and char oxidation near the water-cooled wall on both sides, which finally causes obvious differences in the distribution of temperature and species. For instance, the peak of CO concentration at the center is 12.6 % at 3.3m from the feed entrance, while that near the water-cooled wall is 8.6 % around 3.5m. The char burnout ratio in the bottom ash can be accurately calculated by this model, with a negligible relative error between the simulation of 81.97 % and the measurement of 82.50 %. It also provides a novel method for the calculation of fly ash particles by using size-grouped and non-spherical particles. Small-size particles in the vicinity of the feed inlet, as well as a part of the particles burning at the end of the grate are entrained into the freeboard by the primary air supplied beneath the grate and the high-momentum secondary air on the bed top. This model can provide valuable theoretical guidance for optimizing the refined distribution of fuel and air in grate-fired power plants and mitigating irregular deposition (corrosion) on heat exchangers and water-cooled walls caused by fly ash.

Effects of Castor and Corn Biodiesel on Engine Performance and Emissions under Low-Load Conditions

Growing concerns over resource depletion and air pollution driven by the rising dependence on fossil fuels necessitate the exploration of alternative energy sources. This study investigates the performance and emission characteristics of a diesel engine fueled by biodiesel blends (B10 and B20) derived from castor and corn feedstocks under low-load conditions (idle and minimal accessory loads). We compare the impact of these biofuels on engine power, fuel consumption, and exhaust emissions relative to conventional diesel, particularly in scenarios mimicking real-world traffic congestion and vehicle stops. The findings suggest that biodiesel offers environmental benefits by reducing harmful pollutants like carbon monoxide (CO) and particulate matter (PM) during engine idling and low-load operation. However, replacing diesel with biodiesel requires further research to address potential drawbacks like increased NOx emissions and lower thermal efficiency. While a higher fuel consumption with biodiesel may occur due to its lower calorific value, the overall benefit of reduced contaminant emissions makes it a promising alternative fuel.

Biological mechanisms affecting the release of greenhouse gases from microbial fuel cell-constructed wetland by simultaneously altering structure and electron shuttles

The utilization of microbial fuel cells (MFCs) for regulating greenhouse gas (GHG) emissions in constructed wetlands (CW) has attracted significant attention. The impact of structural modifications, the introduction of iron-carbon materials on pollutant removal and GHG release from MFC-CW has not been systematically studied. In this study, four types of MFC-CWs were constructed, including MFC-CW with separated aerobic and anaerobic zones (SC), MFC-CW with unseparated aerobic and anaerobic zones (IC), SC added with iron-carbon (SFC), and IC added with iron-carbon (IFC). The aim was to investigate the effects of structural changes and electron shuttle additions on the GHG release. The results revealed that IFC simultaneously enhanced pollutant removal and GHG emissions reduction, compared to IC. However, no significant enhancements were observed in SC and SFC. The cumulative emissions of nitrous oxide (N2O) and methane (CH4) in SC were reduced by 51.83% and 89.33% respectively, compared to IC. The modifications made to the structure of MFC-CWs influenced the relationship between functional bacteria (Chlorobium, Azospira, and Denitratisoma) and electrochemically active bacteria (EAB), resulting in increased values of nirS/nosZ and pmoA/mcrA. Comparing the SFC and IFC, despite an improvement in denitrogenation efficiency, the effect of structural alteration on N2O reduction was slight. The electrons in the iron-mediated process were not effectively used for N2O reduction. This study confirmed the crucial involvement of electron shuttles and the structure of MFC-CWs in controlling contaminant removal and GHG emissions.

Wildfire Ashes from the Wildland-Urban Interface Alter Vibrio vulnificus Growth and Gene Expression.

Climate change-induced stressors are contributing to the emergence of infectious diseases, including those caused by marine bacterial pathogens such as Vibrio spp. These stressors alter Vibrio temporal and geographical distribution, resulting in increased spread, exposure, and infection rates, thus facilitating greater Vibrio-human interactions. Concurrently, wildfires are increasing in size, severity, frequency, and spread in the built environment due to climate change, resulting in the emission of contaminants of emerging concern. This study aimed to understand the potential effects of urban interface wildfire ashes on Vibrio vulnificus (V. vulnificus) growth and gene expression using transcriptomic approaches. V. vulnificus was exposed to structural and vegetation ashes and analyzed to identify differentially expressed genes using the HTSeq-DESeq2 strategy. Exposure to wildfire ash altered V. vulnificus growth and gene expression, depending on the trace metal composition of the ash. The high Fe content of the vegetation ash enhanced bacterial growth, while the high Cu, As, and Cr content of the structural ash suppressed growth. Additionally, the overall pattern of upregulated genes and pathways suggests increased virulence potential due to the selection of metal- and antibiotic-resistant strains. Therefore, mixed fire ashes transported and deposited into coastal zones may lead to the selection of environmental reservoirs of Vibrio strains with enhanced antibiotic resistance profiles, increasing public health risk.

Pathways and Environmental Impacts of Methane Migration: Case Studies in the Marcellus Shale, USA

Gas migration incidents, particularly stream contamination cases, have been rarely investigated and gone through the peer review process, with the exception of three sites in northeast Pennsylvania (Dimock and two Sugar Runs in Lycoming and Bradford counties, respectively) where air emission surveys, dissolved methane measurements, and structural (hydro)geologic interpretations have been used to demonstrate potential environmental impacts due to shale gas operations. In addition to reviewing previously published work from these three sites, we report and analyze unpublished new data trying to determine if a direct relationship between methane migration, stream contamination, and air emissions exists at those sites. Our analysis indicates that subsurface methane migration, stream methane contamination, and air emissions might not be all present or detectable at a faulty/leaky shale gas well. Which of these signs of contamination, if any, exist is largely controlled by the local (hydro)geologic conditions. In each case, the most likely migration pathway was from gas charged zones up well annular spaces to confined permeable formations, then laterally to a direct discharge or by vertically controlled joints to streams, water wells, and the atmosphere. The confining units act as barriers to the buoyant movement of stray gases, allowing subsurface travel of gas for 1–4 km from a leaky gas well. The knowledge we learn from these three sites can guide the future investigations of methane contamination cases in other regions.

Analysis and Assessment of Contamination Degree and Emission Sources of Polycyclic Aromatic Hydrocarbons (PAHs and Me-PAHs) in Surface Sediments from Central Coast of Vietnam

Polycyclic aromatic hydrocarbons (PAHs) and their derivatives are a diverse group of organic pollutants, which are relatively persistent and toxic. Simultaneous determination of unsubstituted PAHs and methylated PAHs (Me-PAHs) is necessary to provide comprehensive insights into contamination levels and sources of these pollutants. In this study, we collected surface sediment samples in Vietnamese central coast to analyze 7 PAHs and 12 Me-PAHs. The sediment samples were extracted by using a focused ultrasonic processor with acetone/hexane (1:1) mixture and toluene. The extract was purified by column chromatography technique with activated silica gel and dichloromethane/hexane (1:3) as elution solvent. PAHs and Me-PAHs were determined by a gas chromatography/mass spectrometry (GC/MS) system operated in electron impact ionization (EI) and selected ion monitoring mode (SIM). Concentrations of total 7 PAHs and 12 Me-PAHs ranged from 30 to 246 (average 92) nanograms per gram sediment (ng/g). These levels were comparable to or lower than those measured in Vietnamese river sediments and marine sediments from some other countries in the world. The accumulation profiles of PAHs and Me-PAHs indicated that their emissions are likely associated with mixed pyrogenic and petrogenic sources. Our results have provided preliminary information about the pollution degree and accumulation characteristics of these substances in Vietnamese marine environments. Additional comprehensive studies should be performed to characterize contamination characterisrics, emission sources, and ecological risks of PAHs and their derivatives in this country.

Assessment of the efficiency of improved cooking stoves and their impact in reducing forest degradation and contaminant emissions in Eastern Rwanda

Biomass is a major source of cooking energy in Rwanda. This high dependence on biomass strongly contributes to forest degradation, biodiversity loss, and atmospheric pollution. Shifting from the traditional three-stone stove (TSS) to improved cooking stoves (ICS) is being promoted to reduce wood consumption and air pollutant emissions. This study assessed the emission reduction of adopted ICS and their impact on forest conservation through a combined laboratory and kitchen performance test (KPT).Out of 940 households surveyed in Eastern Province (EP) of Rwanda, 317 used ICS. Among these users, 180 were selected and revisited for an in-depth interview about the adoption process. The four most popular ICSs were selected for evaluating thermal efficiency and emissions of contaminating gases using laboratory test protocol ISO 19867-1. In addition, the avoided wood consumption of improved cooking stoves compared to the TSS was assessed using a KPT in 100 households.The survey findings indicate that 33.7 % of households use only ICS, 23.1 % only TSS, and 56.4 % ICS and TSS combined. The laboratory results show that the Save80 stove had the highest thermal efficiency (45.8 %) followed by Igisubizo (32.8 %), EcoZoom (32.6 %), and Songa (29.6 %). The emission results showed a significant difference in CO2 (carbon dioxide) emissions (p = 0.001) between the ICS models. However, the emissions of PM2.5 (fine particulate matter) and CO (carbon monoxide) of ICS were high compared to the WHO (World Health Organization) guidelines.The KPT results show that using ICS would result in an estimated annual saving of 149,313 tons of firewood corresponding to 0.7 m3 of wood, leading to an annual equivalent reduction of 0.02 ha of forest per household and 7167 ha of forest in the EP. The KPT results show that using ICS reduced CO2 emissions by 0.372 tons per household per year and by 111,088 tons of CO2 in the EP. ICSs have been shown to enhance fuelwood efficiency, leading to reduced forest degradation.