Heavy Oil Combustion Research Articles

Source apportionment of PM2.5 and PM10 pollutants near an urban roadside site using positive matrix factorization

This paper presents results from a comprehensive study of source apportionment of particulate matter (PM) of size PM2.5 and PM10 near a busy highway in Sharjah, United Arab Emirates. Source apportionment was carried out using US Environmental Protection Agency (EPA) Positive Matrix Factorization model. Furthermore, backward trajectory analysis and Potential Source Contribution Function were used to assess air mass transport pathways and identify potential source regions, respectively. The results revealed six major sources for PM2.5, including traffic, sea salt, fugitive dust, secondary aerosols, heavy oil combustion and mineral dust. For PM10, four major sources were identified, including secondary aerosols, traffic, sea salt and mineral dust. Traffic emissions were found to be significant contributors to both PM2.5 and PM10 pollution, along with natural sources like sea salt and mineral dust. Backward trajectory analysis indicated the influence of different wind regimes on air mass transport, with contributions from regions like Arabian Gulf, Arabian Sea, Oman and Iran. The Conditional Bivariate Probability Function analysis further explained the impact of local traffic emissions and other sources on PM pollution under varying wind conditions.

Effects of slag on mechanical and microstructural properties of iron-rich phosphoaluminate cement subjected to high temperature oil well environment

Iron-rich phosphoaluminate cement (shortened as PAC) exhibits excellent high temperature resistance characteristic, enabling it to withstand the ultrahigh temperatures required for the in situ combustion (ISC) of heavy oil. The addition of slag could influence its high temperature resistance by altering its hydration products. Hence the thickening time, physical properties, phase components and microstructure of PAC with slag that were subjected to different high temperature environment (315, 550 and 800 °C) were investigated deeply in this paper. The experimental analysis results revealed that PAC had better high temperature resistance than CAC with and without slag. The addition of slag improved effectively the high temperature resistance of PAC. The influencing mechanism of slag were as follows. C2ASH8 formed at 50 °C inhibited the conversion of C(A,P)H10 to C3AH6. C2AS3H, C3AS2H2 and C3(Fe,Al)S3 formed at 315 °C alleviated the rapid release of the compound water. The phase Ca5(PO4)3OH and C2AS was stable in the range of 550–800 °C. In addition, the capillary pore structure of PAC was optimized. Therefore, PAC with slag had the potential to be used for high temperature oil well cementing.

Comprehensive Understanding of the Heavy Oil Combustion Process: Reaction Behavior, Kinetic Triplet, and Mechanism Implication.

In this work, thermo-oxidative behavior, kinetic triplet, and free radical mechanism of ultraheavy oil during an in situ combustion (ISC) process were systematically surveyed via multiple thermal analysis techniques (TG/DTG/DSC/PDSC), model-free methods, and related mathematical simulation. First, specific mass loss, exothermic intensity, and corresponding temperature intervals were respectively determined in low-/high-temperature oxidation (LTO/HTO) regions. In addition, the comparison of atmospheric/pressurized differential scanning calorimetry (DSC/PDSC) experiments indicated that the pressurized conditions could obviously strengthen the oxidation progress with more heat emission. Then two model-free methods were contrastively employed for PDSC data to calculate LTO and HTO activation energy variations with the conversion rate. Moreover, the acceleratory rate model for LTO and the Sestak-Berggren model for HTO were accordingly picked as the most probable mechanism functions, which were later used to determine the simulated curves. Then, the simulations of α-T and dα/dT-T curves were respectively attained using Friedman equation in MATLAB software and contrasted with experimental data to validate the accuracy of the yielded kinetic triplet and forecast the combustion behavior. Further, the evolution pathways of the underlying oxidation mechanism was illustrated. This study updates the understanding of the nonisothermal combustion process, contributing to the subsequent numerical simulation and feasible investigation for in situ combustion implementation to enhance heavy oil recovery.

Seasonal variation, source identification, and health risk assessment of atmospheric polycyclic aromatic hydrocarbons (PAHs) in Ulsan, South Korea

Gaseous and particulate 21 PAHs were monitored at a residential site in Ulsan, South Korea, over three seasons (December 2013–August 2014). The mean concentrations of Σ21 PAHs were highest in winter (16.2 ± 8.2 ng/m3), followed by spring (8.37 ± 4.53 ng/m3) and summer (6.23 ± 2.53 ng/m3). The mean gaseous concentration of Σ21 PAHs (7.39 ± 4.39 ng/m3) was 2.7 times higher than that of particulate PAHs (2.70 ± 3.38 ng/m3). To identify the sources of PAHs (both types of sources and their areas), diagnostic ratios, principal component analysis, and concentration-weighted trajectory (CWT) were used. The results showed that pyrogenic sources (e.g., coal combustion) were the primary emission sources of PAHs in winter and spring. In summer, the influence of both coal and heavy oil combustion was dominant, suggesting that PAHs could be transported from industrial areas of Ulsan (e.g., petrochemical and nonferrous industrial complexes) by seasonal winds. Regarding emission source areas, the CWT analysis revealed that in winter and spring, PAHs in Ulsan could be attributed to emissions from regional areas, e.g., China and North Korea. The PAH concentrations were also used to assess the health risks associated with the inhalation of these compounds for adults aged 18–70. The results showed that the cancer risks from Σ19 PAHs and Σ13 PAHs did not exceed the guideline set by the US EPA (10−6), indicating no cancer risks for this target group. However, it is worth noting that certain PAHs, which are not listed as priority PAHs by the US EPA, make significant contributions to the benzo[a]pyrene equivalent and the associated cancer risks. Therefore, it is necessary to investigate not only the priority PAHs but also other PAH species to fully evaluate their effect on human health.

Assessment of carbon dioxide emission factors from power generation in Burkina Faso

Power generation is the second largest source of greenhouse gases (GHGs), particularly carbon dioxide (CO2), in Burkina Faso's energy sector. When preparing the National Communications on Climate Change, Burkina Faso uses the default emission factors of the Intergovernmental Panel on Climate Change (IPCC) to estimate emissions from power generation. This study presents an assessment of CO2 emission factors from power generation for 2018 in Burkina Faso and an assessment of the contribution of renewable energy to the reduction of CO2 emissions. The national electricity company of Burkina Faso was chosen as the scope for this study. The estimation of emission factors for combustion is based on an analysis of fuels which are characterised in terms of molecular composition, density and water content. For CO2, the emission factor is 76 903 kg/TJ for the combustion of Heavy Fuel Oil (HFO) and 73 525 kg/TJ for that of Distillate Diesel Oil (DDO). Using these emission factors, the CO2 emissions attributable to power generation in 2018 were estimated at almost 580 Gg. The CO2 emission factor for thermal power generation was estimated at 0.663 kg/kWh and that of the electricity generation mix at 0.569 kg/kWh. Finally, the use of 14.25% renewable energy in electricity generation avoided 16.7% of CO2 emissions in 2018. The emission factor of electricity production decreases with the increase in the share of renewable energy in the energy mix.

Source apportionment of PM2.5 oxidative potential in an East Mediterranean site

This study aimed to evaluate the oxidative potential (OP) of PM2.5 collected for almost a year in an urban area of the East Mediterranean. Two acellular assays, based on ascorbic acid (AA) and dithiothreitol (DTT) depletion, were used to measure the OP. The results showed that the mean volume normalized OP-AAv value was 0.64 ± 0.29 nmol·min−1·m−3 and the mean OP-DTTv was 0.49 ± 0.26 nmol·min−1·m−3. Several approaches were adopted in this work to study the relationship between the species in PM2.5 (carbonaceous matter, water-soluble ions, major and trace elements, and organic compounds) or their sources and OP values. Spearman correlations revealed strong correlations of OP-AAv with carbonaceous subfractions as well as organic compounds while OP-DTTv seemed to be more correlated with elements emitted from different anthropogenic activities. Furthermore, a multiple linear regression method was used to estimate the contribution of PM2.5 sources, determined by a source-receptor model (Positive Matrix Factorization), to the OP values. The results showed that the sources that highly contribute to the PM2.5 mass (crustal dust and ammonium sulfate) were not the major sources contributing to the values of OP. Instead, 69 % of OP-AAv and 62 % of OP-DTTv values were explained by three local anthropogenic sources: Heavy Fuel Oil (HFO) combustion from a power plant, biomass burning, and road traffic emissions. As for the seasonal variations, higher OP-AAv values were observed during winter compared to summer, while OP-DTTv did not show any significant differences between the two seasons. The contribution of biomass burning during winter was 33 and 34 times higher compared to summer for OP-AAv and OP-DTTv, respectively. On the other hand, higher contributions were observed for HFO combustion during summer.

Preparation of Surface-Active Hyperbranched-Polymer-Encapsulated Nanometal as a Highly Efficient Cracking Catalyst for In Situ Combustion of Heavy Oil.

In situ combustion of heavy oil is currently the most suitable thermal method that meets energy consumption and carbon dioxide emission requirements for heavy oil recovery. The combustion catalyst needs to perform multiple roles for application; it should be capable of catalyzing heavy oil combustion at high temperatures, as well as be able to migrate in the geological formation for injection. In this work, a hyperbranched polymer composite nanometal fluid was used as the injection vector for a heavy oil in situ combustion catalyst, which enabled the catalyst to rapidly migrate to the surface of the oil phase in porous media and promoted heavy oil cracking deposition at high temperatures. Platinum (Pt) nanoparticles encapsulated with cetyl-hyperbranched poly(amide-amine) (CPAMAM), with high interfacial activity, were synthesized by a facile phase-transfer method; the resulting material is called Pt@CPAMAM. Pt@CPAMAM has good dispersion, and as an aqueous solution, it can reduce the interfacial tension between heavy oil and water. As a catalyst, it can improve the conversion rate during the pyrolysis of heavy oil in a nitrogen atmosphere. The catalyst structure designed in this study is closer to that exhibited in practical geological formation applications, making it a potential method for preparing catalysts for use in heavy oil in situ combustion to resolve the problem of catalyst migration in the geological formation.

Valorization of fly ash by nickel ferrite and vanadium oxide recovery through pyro-hydrometallurgical processes: Technical and environmental assessment

The fly ash (FA) from the combustion of heavy oil in power stations is characterized by fine particles containing toxic metals. The sample utilized in this study was gathered from the dust precipitators of seven heavy-oil-consuming Iranian power plants. Substantial quantities of heavy metals, particularly vanadium, iron, and nickel, have been detected in the sample, indicating both its potential utility and hazard to the soil and groundwater. The harmful consequences of FA disposal on the environment have led to the adoption of recycling as a treatment approach in this study. The valorization of FA was investigated by producing nickel ferrite (NiFe2O4) and vanadium pentoxide (V2O5) through a novel approach using a combination of pyro-hydrometallurgical processes, which resulted in proposing a recycling closed-loop flowsheet. Roasting was first practiced to form NiFe2O4 by reacting the nickel and iron content of the FA. The NiFe2O4 showed a low dissolution against inorganic acids (H2SO4, HCl, and HNO3). The vanadium content of the FA showed a remarkable recovery in H2SO4 (91%) and HCl (95.6%), while the dissolution of Ni was limited to 16.85% and 17.5%, respectively. The produced NiFe2O4 acted well in response to the magnetic field, and its purity was further increased to 95–96% through a two-stage process consisting of grinding and magnetic separation. The nano-sized spherical NiFe2O4 with saturation magnetization of 34.66 and 30.82 emu. g−1 was obtained from H2SO4 and HCl residues, respectively. The dissolved vanadium was recovered as V2O5 via oxidation-precipitation in sulfate media and oxidation-ammonium precipitation in chloride solution. The purity of V2O5 in sulfate and chloride media was 93% and 98.5%, respectively. Finally, a life cycle assessment (LCA) study was performed on the suggested methods to track the ecological effects of extracting V and Ni from oil combustion FA. According to the performed LCA, H2SO4 was determined as the proper leaching reagent considering the environmental and technical aspects.

Compositional numerical analysis of multiphase flow of crude oil in porous media under non-isothermal conditions

Abstract The present work details the development of a compositional model to replicate the heavy hydrocarbon flow in porous reservoir systems under non-isothermal conditions. The mathematical model considers mass and energy conservation equations describing the reactive of natural variables distributed in a multiphase hydrocarbon system. Such natural variable based compositional models better suit fully implicit numerical schemes with inexpensive Jacobian matrix computations. Further, the model accommodates a switch of primary variables for the disappearance and reappearance of a phase. The resulting nonlinear conservation equations are numerically discretized using a block-centered finite-difference scheme and solved with a quasi-Newton based implicit iterative solver. The present model is validated with the thermal profiles presented in the literature for the multiphase flow during the combustion of heavy crude oil in petroleum reservoir system with performance coefficient (R 2), mean absolute error (MBE), and maximum absolute percentage error (MAPE) of about 0.954, 0.37, and 0.01 respectively. The developed compositional model projected 26 and 72 % of light and heavy oil recoveries respectively in about 160 days with a maximum or peak temperature of about 798 K. Further, the thermal and production profiles projected by the sensitivity analysis on various operating parameters are presented. It is noteworthy that the present works aid in providing an economical numerical based tool in evaluating the flow and transport during underground or in-situ combustion process for efficient energy exploration.

Fine aerosol sources at an urban background site in the Eastern Mediterranean (Nicosia; Cyprus): Insights from offline versus online source apportionment comparison for carbonaceous aerosols

A total of 348 daily PM2.5 samples were collected at an urban background site of Nicosia, capital of Cyprus, for one-year period (October 2018–October 2019) to assess the origin and sources of fine PM at the Eastern Mediterranean, a poorly characterized area of the world.The samples were analysed for water soluble ionic species, elemental and organic carbon, carbohydrates and trace metals, the combination of which were utilized to identify pollution sources by applying Positive Matrix Factorization (PMF). Six PM2.5 sources, namely long-range transport (LRT; 38 %), traffic (20 %), biomass burning (16 %), dust (10 %), sea salt (9 %) and heavy oil combustion (7 %), were identified.Despite sampling in an urban agglomeration, the chemical fingerprint of the aerosol is largely dictated by air mass origin rather than local sources. Springtime is characterized by the most elevated particulate levels due to the southerly air masses carrying particles from the Sahara Desert. Northerlies are observed throughout the year but are predominant during summer allowing the LRT source to peak (54 % during summer). Only during winter, due to extensive use of biomass combustion for domestic heating (36.6 % during winter), local sources dominate.A co-located online PMF source apportionment of submicron carbonaceous aerosols (Organic Aerosols, OA; Black Carbon) was performed by the means of an Aerosol Chemical Speciation Monitor (for OA) and an Aethalometer (for BC) for a four-month period. The comparison between the two methodologies allowed to better assess the robustness and limitations of the two methodologies. More specifically, LRT OA and biomass burning BC apportioned by the offline PMF showed a strong consistency with the online apportioned more oxidized oxygenated OA and BCwb, respectively; cross validating these sources. On the other hand, our traffic factor may contain additional hydrocarbon-like OA and BC from fossil fuel sources other than just vehicular emissions. Finally, the offline biomass burning OA source is likely to contain both primary and secondary OA.

Experimental study on the reliability of thermal analysis techniques in the in-situ combustion of heavy oil

ABSTRACT In situ combustion (ISC) is an effective method to enhance heavy oil (HO) recovery. Thermal analysis (TA) techniques are considered ideal tools for study the HO oxidation. However, the reliability of TA data has been affected by the strong adhesion of high viscosity HO to the substrate and crucible. Consequently, there has been a deviation in the DTA peak temperature for both low and high-temperature oxidation of HO and HO/clay mixtures at 7°C, 19°C, and 8°C, 11°C respectively. Additionally, negative values of reaction activation energy (E α ) were observed, reaching up to −1395.94 ± 836.2 kJ mol−1. This study aimed to identify factors that impact TA data reliability and oxidation kinetics. By implementing solutions such as ultrasonic stirring and needle tip loading, this study was able to improve the accuracy and reproducibility of TA data and E α value. The results of this investigation provide valuable insight for future ISC.

Towards a better understanding of fine PM sources: Online and offline datasets combination in a single PMF

Source apportionment (SA) techniques allocate the measured ambient pollutants with their potential source origin; thus, they are a powerful tool for designing air pollution mitigation strategies. Positive Matrix Factorization (PMF) is one of the most widely used SA approaches, and its multi-time resolution (MTR) methodology, which enables mixing different instrument data in their original time resolution, was the focus of this study. One year of co-located measurements in Barcelona, Spain, of non-refractory submicronic particulate matter (NR-PM1), black carbon (BC) and metals were obtained by a Q-ACSM (Aerodyne Research Inc.), an aethalometer (Aerosol d.o.o.) and fine offline quartz-fibre filters, respectively. These data were combined in a MTR PMF analysis preserving the high time resolution (30 min for the NR-PM1 and BC, and 24 h every 4th day for the offline samples). The MTR-PMF outcomes were assessed varying the time resolution of the high-resolution data subset and exploring the error weightings of both subsets. The time resolution assessment revealed that averaging the high-resolution data was disadvantageous in terms of model residuals and environmental interpretability. The MTR-PMF resolved eight PM1 sources: ammonium sulphate + heavy oil combustion (25%), ammonium nitrate + ammonium chloride (17%), aged secondary organic aerosol (SOA) (16%), traffic (14%), biomass burning (9%), fresh SOA (8%), cooking-like organic aerosol (5%), and industry (4%). The MTR-PMF technique identified two more sources relative to the 24 h base case data subset using the same species and four more with respect to the pseudo-conventional approach mimicking offline PMF, indicating that the combination of both high and low TR data is significantly beneficial for SA. Besides the higher number of sources, the MTR-PMF technique has enabled some sources disentanglement compared to the pseudo-conventional and base case PMF as well as the characterisation of their intra-day patterns.

Recent Advances in the Study of In Situ Combustion for Enhanced Oil Recovery

Global estimates for our remaining capacity to exploit developed oil fields indicate that the currently recoverable oil (light oil) will last for approximately 50 years. This necessitates the development of viscous and superviscous oil fields, which will further compensate for the loss of easily produced oil. In situ combustion is the most promising production method, which allows for increased oil recovery from a reservoir. This being the case, this study provides an overview of global trends regarding the research and implementation of the method under consideration, in order to promote understanding of its applicability and effectiveness. The background to the development of the method is discussed in detail, illustrating the growing interest of researchers in its study. Cases of both successful as well as inefficient implementations of this method in real oil fields are considered. The main focus of the article is to investigate the influence of the parent rock and catalysts on the combustion process, as this is a new and actively developing area in the study of enhanced oil recovery using in situ combustion. Geological surveys, in addition to experimental and numerical studies, are considered to be the main methods that are used to investigate processes during in situ combustion. The analysis that we carried out led us to understand that the processes which occur during the combustion of heavy oil are practically unpredictable and, therefore, poorly understood. The specificity of the oil composition under consideration depends on the field, which can lead to a change in the required temperature regimes for its production. This indicates that there exists multiple specific applications for the method under consideration, each requiring additional full studies into both the fractional composition of oil and its reservoirs. The article also considers various technologies for implementing the in situ combustion method, such as ND-ISC, THAITM, COSH, CAGD, and SAGD. However, the literature review has shown that none of the technologies presented is widely used, due to the lack of an evidence base for their successful application in the field. Moreover, it should be noted that this method has no limits associated with the oil occurrence depth. This technology can be implemented in thin reservoirs, as well as in flooded, clayey, sandy, and carbonate reservoirs. The review we have presented can be considered as a guide for further research into the development of global solutions for using the proposed method.

Measurement report: Rapid changes of chemical characteristics and health risks for highly time resolved trace elements in PM2.5 in a typical industrial city in response to stringent clean air actions

Abstract. Atmospheric trace metals entail significant damages in human health and ecosystem safety, and thus a series of clean air actions have been implemented to decrease the ambient element concentrations. Unfortunately, the impact of these emission control measures on element concentrations in fine particles remains poorly understood. In our study, the random forest (RF) model was applied to distinguish the effects of emission and meteorology to trace elements in PM2.5 in a typical industrial city named Tangshan based on a 3-year (2017–2020) hourly field observation. The result suggested that the clean air actions have facilitated the dramatic decreases of the deweathered concentrations of Ga, Co, Pb, Zn, and As by 72 %, 67 %, 62 %, 59 %, and 54 %, respectively. It is attributable to the strict implementation of “coal to gas” strategies and optimisation of industrial structure and layout. However, the deweathered levels of Ca (8.3 %), Cr (18.5 %), and Fe (23 %) only displayed minor decreases, indicating that the emission control measures for ferrous metal smelting and vehicle emission were not very effective. The positive matrix factorisation (PMF) results suggested that the contribution ratios of biomass burning, non-ferrous metal smelting, coal combustion, ferrous metal smelting, heavy oil combustion, and traffic-related dust changed from 33 %, 11 %, 15 %, 13 %, 3 %, and 25 % to 33 %, 8 %, 8 %, 13 %, 4 %, and 33 %, respectively. To date, no significant non-carcinogenic and carcinogenic risks were observed for all of the elements, while both of As and Pb still showed relatively high health damages. It was proposed to further cut down the combustion-related emissions (e.g. As and Pb) because it showed the highest marginal health benefits. Besides this, the control of traffic-related emissions might be a key abatement strategy to facilitate the reduction of elements in fine particles.

PM2.5-bound PAHs near a typical industrial park: Determining health risks associated with specific industrial sources

Source-specific potential health risk was proposed as an effective index for determining priority control sources of PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) near an industrial park. However, industry-specific emission profiles were limited. In this study, 60 emission source samples from 13 industries and 139 p.m.2.5 samples near an industrial park were collected from 2020 to 2021. The PAH profiles of 12 industrial emission sources were constructed to address the difficulty of source apportionment refined to industrial categories. A diagnostic ratio method and a positive matrix factorization method (PMF) were used to qualitatively and quantitatively determine the emission sources of 16 p.m.2.5-bound PAHs. The incremental lifetime carcinogenic risk (ILCR) of PAH inhalation exposure for the local population was attributed to sources by a PMF-ILCR model. The results show that the local PAH pollution seriously exceeded (86.3% sampling days) the standard (GB3095-2012). The concentration of PAHs was 33.6 ± 32.6 ng/m3 and showed a seasonal trend of “heating season > autumn > spring”. There were five main sources of PM2.5-bound PAHs near the industrial park: heavy oil combustion (29.8%), coal and natural gas combustion (28.0%), vehicle emissions (19.9%), steel industry emissions (19.4%) and tar volatilization (2.9%). There is potential carcinogenic risk to both children (3.1 × 10−6) and adults (1.2 × 10−5). The mass contribution of each source to ambient PAHs is not equivalent to its contribution to potential health risk. The risks of PM2.5-bound PAHs almost all correspond to vehicle emissions (46.3%), heavy oil combustion (25.9%) and steel industrial sources (24.9%).

In Situ Combustion of Heavy Oil within a Vuggy Carbonate Reservoir: Part I—Feasibility Study

Worldwide, the known recoverable heavy oil and bitumen reserves make up more than 64% of the total reserves, of which more than 60% are trapped in carbonates. Air injection has immense potential for hydrocarbon recovery from various reservoirs. While most of the successful air-based techniques are performed within carbonate reservoirs containing light oil, theoretically, in situ combustion (ISC) has also shown great potential for recovering heavy oil and bitumen. Carbonates are complex in terms of geology and are often associated with fractures and vugs that affect the fluid flow, pressure propagation and progression of the ISC reactions. This paper describes the first experiment in which the triple-porosity concept was applied to simulate heterogeneity through artificially induced vugs, core matrix and fractures. This approach was used to study the feasibility of the ISC recovery technique for heavy oil (14° API) within a dolomite reservoir using a combustion tube (CT) in an experiment performed at 1740 psig. The combustion front advanced through 78% of the core length prior to the termination of air injection, producing 80% of the initial oil. To differentiate between the various sources of the CO2 gas (a product of carbonate decomposition vs. the combustion reaction) the atomic ratios of (CO2 + CO)/CO = 6 and (CO2 + CO)/N2 = 0.21 were applied. Additionally, partial upgrading of the produced heavy oil was observed.

Distribution, Source Apportionment and Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Surface Sediments at the Basin Scale: A Case Study in Taihu Basin, China.

As a systematic research at basin scale, this study investigated the spatial distribution, source apportionment and ecological risks of eighteen polycyclic aromatic hydrocarbons (PAHs) in surface sediments at different functional regions (rivers, lakes and reservoirs) from Taihu basin. Results showed that the mean values of 18 PAHs (defined as ∑18PAHs) in river sediments (1277 ng/g) was much higher than those observed in lake sediments (243 ng/g) and reservoir sediments (134 ng/g). The accumulation of PAHs in river sediments was largely impacted by the local social-economic development and energy consumption. The positive matrix factorization (PMF) and isomer ratios analysis of PAHs suggest that relative contributions to PAHs in sediments were 15% for gasoline and heavy oil combustion, 9% for oil spills, 30% for coal combustion, 23% for traffic source, and 23% for diagenetic source. Ecological risk assessment based upon risk quotient (RQ) method indicated that sediments at Taihu basin have suffered moderate risk of PAHs.

Catalytic capacity evolution of montmorillonite in in-situ combustion of heavy oil

Clay minerals such as montmorillonite are significant in petroleum storage and recovery. Montmorillonite (Mt) is a natural solid acid catalyst containing Brønsted and Lewis acid sites and can catalyze heavy oil oxidation (HOO) during in-situ combustion (ISC). However, its catalytic activity largely depends on the heating process of heavy oil. In the study, the catalytic capacity evolution of Mt in ISC of heavy oil was explored with the isoconversional method and thermal analysis. In low-temperature oxidation (LTO) and high-temperature oxidation (HTO) stages, the addition of Mt largely reduced the peak temperatures (Tpeak) of DTA and DTG and the Tpeak of H2O (LTO and HTO stages) and CO2 (HTO stage) in HOO. Notably, Mt did not always show the positive catalytic effect. In LTO stage, the thermal transformation process had a small effect on DTA Tpeak, Tpeak of H2O and CO2, and the reaction activation energy (Eα) of HOO. In HTO stage, the catalytic effect of Mt on HOO was related to its thermal transformation process, especially interlayer water (IW) dehydration and dehydroxylation. In HTO stage, the IW dehydration process of Mt showed the strongest catalytic effect on HOO, significantly reduced DTA Tpeak and Eα, and resulted in the lowest Tpeak of H2O and CO2. The dehydroxylation process of Mt also showed a certain effect, whereas the overlapping process between the dehydration (IW) reaction and partial dehydroxylation reaction of Mt had no positive catalytic effect on HOO. DTA, TG-FTIR, and non-isothermal kinetic analysis further confirmed that the catalytic capacity of Mt in HTO stage was improved by IW dehydration process of Mt and weakened by the dehydroxylation process of Mt.

Characterization of PM2.5 in Coastal Urban Area, Northwest Morocco: Seasonal Variations, Elemental Composition and Source Apportionment

Sale, located along the Atlantic Ocean, is the third-largest city in Morocco. The Bouregreg river separates Sale from Rabat (Morocco’s capital city). This City is characterized by a high demographic density. Their main air pollution sources are traffic, ocean, potteries, fishing, domestic heating, and artisanal activities. Ambient PM2.5 particles were collected in an urban area of Sale City (Morocco) from July 2018 to July 2019. The sampling was carried out using a Dichotomous sampler and the Total X-Ray Fluorescence technique (TXRF) was used to evaluate the elemental composition of the collected filters. In this paper, chemical characterization, and source apportionment of PM2.5 were investigated. The results showed that the PM2.5 mass concentrations vary, during the sampling period, from 3.08 µg/m3 to 49.48 µg/m3 with an average of 17.30 µg/m3. The highest values were observed in winter while the lowest in summer. The influence of atmospheric transport scenarios on the levels of PM was carried out using air mass back-trajectories, using the HYSPLIT™ model. This study allowed identifying four main clusters arriving at our receptor site in Sale City: Iberian Coast (24%), Near Atlantic Ocean (33%), Local (28%), and Oceanic (15%). For seasonal variations of metal concentrations, K, Ca, V, Mn, Fe, Ni, Cu, Zn, As, Sr, Ba, and Pb exhibited their highest concentrations during winter while Ti and Cr, their highest concentrations were observed during Autumn. The Enrichment Factor (EF) analysis showed that Ti, Sr, Mn, K, Ca, and Ba are mainly originated from airborne dust with EF < 10, V, Cu, Cr have both natural and anthropogenic sources with 10 < EF < 100, while Ni, Zn, and Pb were mainly from anthropogenic source with EF > 100. Five factors were selected in Positive Matrix Factorization (PMF) model’s analysis: crustal contribution, road dust, brake wear, heavy oil combustion, and exhaust vehicle emissions. Their contributions to PM2.5 were 5%, 53.6%, 20.1%, 14.3% and 7%, respectively. Road dust and vehicle exhaust sources showed the highest contribution in winter; while soil dust, brake wear, and oil combustion sources contributed the most in summer. The present study could be considered as the first source apportionment study on PM2.5 fractions carried out in Sale City, Morocco.

PM2.5 elemental composition in indoor residential environments and co-exposure effects on respiratory health in an industrial area

This study aimed to identify and characterise indoor sources of particulate matter (PM) in domestic environments. 74 inhabited apartments located in the urban area of Gela (Sicily, Italy), close to a refinery, and in three villages of the hinterland were evaluated, in real-world conditions, for the elemental composition of PM2.5. The samples were collected simultaneously inside and outside each apartment for 48 h. In addition, two of the apartments were simultaneously studied for four weeks.The elemental composition of PM2.5 was determined by applying a chemical fractionation procedure followed by inductively-coupled plasma spectrometry analysis, with both optical emission and mass detection. The extractable, more bio-accessible fraction (ext), and the mineralised residual fraction (res) of each element were determined, thus increasing the selectivity of elements as source tracers.Indoor air in the considered apartments was affected by both outdoor pollution and specific indoor emission sources. The behaviour of each source was studied in detail, identifying a reliable tracer: Tires for soil, Asext for industrial sources, Vext for heavy oil combustion, Ce for cigarette smoking and Mo for the use of vacuum dust cleaners. Asext and Vext showed an excellent infiltration capacity, while the concentration of Tires was affected by a low infiltration capacity and by the contribution of particles re-suspension caused by the residents' movements. In the case of Ce and Mo, indoor concentrations were much higher than outdoor with a high variability among the apartments, due to the inhabitants’ habits concerning cigarette smoke and use of electric appliances. To test the overall effect of the concomitant exposure to the identified sources on Wh12 M and on DDA, a WQS analysis was conducted. Cigarette smoking and heavily oil combustion driven the Wh12 M odds increase, while the DDA odds increase was mainly driven by heavily oil combustion and the use of vacuum dust cleaners.