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Composition of a gas and ash mixture formed during the pyrolysis and combustion of coal-water slurries containing petrochemicals
2021
Dorokhov, V.V. | Kuznetsov, G.V. | Nyashina, G.S. | Strizhak, P.A.
This paper presents the results of experimental research into the component composition of gases and ash residue from the combustion of a set of high-potential coal-water slurries containing petrochemicals. We have established that the use of slurry fuels provides a decrease in the CO₂, CH₄, SO₂, and NOₓ concentrations as compared to those from coal combustion. The content of carbon monoxide and hydrogen in the gas environment from the combustion of slurries is higher due to the intense water evaporation. It is shown that adding biomass allows a further 5–33% reduction in the emissions of nitrogen and sulfur oxides as compared to the coal-water slurry and the composition with added waste turbine oil and a 23–68% decrease as compared to coal (per unit mass of the fuel burnt). The mechanisms and stages of CO₂, SO₂, and NOₓ formation are explained with a view to controlling gaseous anthropogenic emissions and ash buildup. The values of the relative environmental performance indicator are calculated for slurry fuels. It is shown to exceed the same indicator of bituminous coal by 28–56%.
Show more [+] Less [-]In-depth investigation of Sodium percarbonate as oxidant of PAHs from soil contaminated with diesel oil
2021
Cavalcanti, Jorge Vinicius Fernandes Lima | Fraga, Tiago José Marques | Loureiro Leite, Mirella de Andrade | dos Santos e Silva, Daniella Fartes | de Lima, Valmir Félix | Schuler, Alexandre Ricardo Pereira | do Nascimento, Clístenes Williams Araújo | da Motta Sobrinho, Maurício Alves
Sodium percarbonate (SPC, 2Na₂CO₃∙3H₂O₂), is a compound that can be used under multiple environmental applications. In this work, SPC was employed as oxidant in the treatment of soil contaminated with diesel oil. The soil samples were collected during the earthmoving stage of RNEST Oil Refinery (Petrobras), Brazil. Then, the samples were air-dried, mixed and characterized. Subsequently, raw soil was contaminated with diesel and treated by photo-Fenton reaction (H₂O₂/Fe²⁺/UV). SPC played a significant role in the generation of hydroxyl radicals under the catalytic effect of ferrous ions (Fe²⁺), hydrogen peroxide (H₂O₂) and radiation. These radicals provoked the photodegradation of polycyclic aromatic hydrocarbons (PAHs), in the soil remediation. A factorial design 3³ was carried out to assess the variables which most influenced the decrease in total organic carbon (TOC). The study was performed with the following variables: initial concentration of [H₂O₂] and [Fe²⁺], between 190.0 and 950.0 mmol L⁻¹ and 0.0–14.4 mmol L⁻¹, respectively. UV radiation was supplied from sunlight, blacklight lamps, and system without radiation. All experiments were performed with 5.0 g of contaminated soil in 50.0 mL of solution. The initial concentration of Fe²⁺ showed the statistically most significant effect. The oxidation efficiency evaluated in the best condition showed a decrease from 34,765 mg kg⁻¹ to 15,801 mg kg⁻¹ in TOC and from 85.750 mg kg⁻¹ to 20.770 mg kg⁻¹ in PAHs content. Moreover, the sums of low and high molecular weight polycyclic aromatic hydrocarbons (LMW-PAHs and HMW-PAHs) were 19.537 mg kg⁻¹ and 1.233 mg kg⁻¹, respectively. Both values are within the limits recommended by the United Sates Environmental Protection Agency (USEPA) and evidenced the satisfactory removal of PAHs from contaminated soil, being an alternative to classic oxidation protocols.
Show more [+] Less [-]Influence of illegal artisanal small-scale gold mining operations (galamsey) on oil and grease (O/G) concentrations in three hotspot assemblies of Western Region, Ghana
2020
Mantey, J. | Nyarko, K.B. | Owusu-Nimo, F. | Awua, K.A. | Bempah, C.K. | Amankwah, R.K. | Akatu, W.E. | Appiah-Effah, E.
This study determined the contamination levels of oil and grease (O/G) across nine (9) galamsey operations under different environmental media (background soil, surface drainage, slurry/sludge and galamsey wastes) in three galamsey hotspot assemblies (Tarkwa Nsuaem, Amenfi East and Prestea Huni Valley) within the Western region of Ghana. Triplicate samples each of the four environmental media for the nine galamsey types (Washing Board, Washing Plant, Anwona, Dig and Wash, Dredging, Underground Abandoned Shaft, Underground Sample Pit, Chamfi and Mill House) were collected and analysed using n-hexane extractable materials in acidic medium by extraction and gravimetry to determine O/G concentrations. From the comparison of mean ranked concentration of O/G, using Kruskal-Wallis Test, the observed differences in the ranking was significant across all four media. The O/G concentrations for Anwona, Chamfi, Mill House, Washing Board and Washing Plant galamsey recorded exceedances when compared to the Ghana EPA Effluent Guideline Value of 100 mg/L for water and The New Dutch Lists’ Target and Intervention Value of 50 mg/kg and 500 mg/kg for solid/semi-solid materials. Consistently and for all environmental media types, the levels of O/G across the galamsey types were in the descending order of: Washing Board, Chamfi, Anwona, Mill House, Washing Plant, Underground Sample Pit, River Dredging, Dig and Wash, Underground Abandoned Shaft and Control Sample (non-galamseyed areas). In general, the surface drainage medium was predominantly found to be the most impacted upon medium from hydrocarbons by seven of the nine galamsey operations (Washing Board, Anwona, Chamfi, Mill House, Dredging, Dig and Wash and Underground Sample Pit). This was followed by slurry/sludge, background soil and waste media in that order. Expectedly, there were no exceedances for the Reference or Control Samples (non-galamseyed areas).
Show more [+] Less [-]Potential sources, influencing factors, and health risks of polycyclic aromatic hydrocarbons (PAHs) in the surface soil of urban parks in Beijing, China
2020
Qu, Yajing | Gong, Yiwei | Ma, Jin | Wei, Haiying | Liu, Jiyuan | Liu, Lingling | Wu, Haiwen | Yang, Shuhui | Chen, Yixiang
Urban parks are an important part of the urban ecological environment. The environmental quality of parks is related to human health. To evaluate sources of polycyclic aromatic hydrocarbons (PAHs) in soils of urban parks and their possible health risks, soil samples from 122 parks in Beijing, China, were collected and analyzed. The total content of 16 PAHs between 0.066 and 6.867 mg/kg. Four-ring PAHs were predominant, followed by 5-ring PAHs, while the fraction of 2-ring PAHs was the lowest. The dominant PAHs sources were found to be coal combustion and oil fuels such as gasoline and diesel. A conditional inference tree (CIT) was used to identify the key influencing factors for PAHs. Traffic emissions was the most important factor, followed by coal consumption, as well as the history and location of the park. Incremental lifetime cancer risk (ILCR) for urban park soil in Beijing were low under normal conditions. The soil PAHs exposure pathway risk for both children and adults decreased in the following order: ingestion > dermal contact > inhalation. The risk from soil in parks to children’s health is slightly higher than that of adults, although the health risk due to exposure to PAHs was not extraordinary. Ecosystem risk was negligible.
Show more [+] Less [-]Occurrence and weathering of petroleum hydrocarbons deposited on the shoreline of the North Saskatchewan River from the 2016 Husky oil spill
2020
Yang, Zeyu | Shah, Keval | Laforest, Sonia | Hollebone, Bruce P. | Situ, Jane | Crevier, Charlotte | Lambert, Patrick | Brown, Carl E. | Yang, Chun
Following the 16TAN Husky oil spill along the North Saskatchewan River (NSR), the occurrence and natural attenuation of the petroleum hydrocarbons were assessed by analyzing the littoral zone sediments/oil debris collected from July 2016 to October 2017. Husky oil-free, mixed sediment-Husky oil, and Husky oil debris samples were identified for all the collected samples. Shoreline sediments were contaminated by mixed biogenic, pyrogenic and petrogenic inputs prior to the spill. Oil stranded on the shoreline of NSR was moved or buried due to the very dynamic conditions of the shoreline, or cleaned through a series of cleanup activities after the spill. Most normal alkanes were naturally weathered, whereas most of the branched alkanes and all of the saturated petroleum biomarkers remained. Some lighter molecular weight (e.g., 2 to 3-ring) polycyclic aromatic hydrocarbons (PAHs) were lost rapidly after the spill, whereas sulfur containing components, e.g., dibenzothiophenes and benzonaphthothiiophenes, and those having a heavier molecular weight did not change markedly even 15 months post-spill. Similarly, some light hydrocarbons (e.g., <C₁₀) were lost over the first kilometers from the point of entry (POE), while heavier hydrocarbons did not show any major differences away from the POE. Very large inter-site and inter-survey discrepancies were found for samples. Evaporation into the air and dissolution into water, combined with biodegradation, were together or independently the main contributors to the loss of the light molecular hydrocarbons.
Show more [+] Less [-]Sorption of dispersed petroleum hydrocarbons by activated charcoals: Effects of oil dispersants
2020
Ji, Haodong | Xie, Wenbo | Liu, Wen | Liu, Xiaona | Zhao, Dongye
Marine oil spill often causes contamination of drinking water sources in coastal areas. As the use of oil dispersants has become one of the main practices in remediation of oil spill, the effect of oil dispersants on the treatment effectiveness remains unexplored. Specifically, little is known on the removal of dispersed oil from contaminated water using conventional adsorbents. This study investigated sorption behavior of three prototype activated charcoals (ACs) of different particle sizes (4–12, 12–20 and 100 mesh) for removal of dispersed oil hydrocarbons, and effects of two model oil dispersants (Corexit EC9500A and Corexit EC9527A). The oil content was measured as n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and total petroleum hydrocarbons (TPHs). Characterization results showed that the smallest AC (PAC100) offered the highest BET surface area of 889 m2/g and pore volume of 0.95 cm3/g (pHPZC = 6.1). Sorption kinetic data revealed that all three ACs can efficiently adsorb Corexit EC9500A and oil dispersed by the two dispersants (DWAO-I and DWAO-II), and the adsorption capacity followed the trend: PAC100 > GAC12 × 20 > GAC4 × 12. Sorption isotherms confirmed PAC100 showed the highest adsorption capacity for dispersed oil in DWAO-I with a Freundlich KF value of 10.90 mg/g∙(L/mg)1/n (n = 1.38). Furthermore, the presence of Corexit EC9500A showed two contrasting effects on the oil sorption, i.e., adsolubilization and solubilization depending on the dispersant concentration. Increasing solution pH from 6.0 to 9.0 and salinity from 2 to 8 wt% showed only modest effect on the sorption. The results are useful for effective treatment of dispersed oil in contaminated water and for understanding roles of oil dispersants.
Show more [+] Less [-]Polycyclic aromatic compounds (PACs) in the Canadian environment: Exposure and effects on wildlife
2020
Wallace, S.J. | de Solla, S.R. | Head, J.A. | Hodson, P.V. | Parrott, J.L. | Thomas, P.J. | Berthiaume, A. | Langlois, V.S.
Polycyclic aromatic compounds (PACs) are ubiquitous in the environment. Wildlife (including fish) are chronically exposed to PACs through air, water, sediment, soil, and/or dietary routes. Exposures are highest near industrial or urban sites, such as aluminum smelters and oil sands mines, or near natural sources such as forest fires. This review assesses the exposure and toxicity of PACs to wildlife, with a focus on the Canadian environment. Most published field studies measured PAC concentrations in tissues of invertebrates, fish, and birds, with fewer studies of amphibians and mammals. In general, PAC concentrations measured in Canadian wildlife tissues were under the benzo[a]pyrene (BaP) guideline for human consumption. Health effects of PAC exposure include embryotoxicity, deformities, cardiotoxicity, DNA damage, changes to DNA methylation, oxidative stress, endocrine disruption, and impaired reproduction. Much of the toxicity of PACs can be attributed to their bioavailability, and the extent to which certain PACs are transformed into more toxic metabolites by cytochrome P450 enzymes. As most mechanistic studies are limited to individual polycyclic aromatic hydrocarbons (PAHs), particularly BaP, research on other PACs and PAC-containing complex mixtures is required to understand the environmental significance of PAC exposure and toxicity. Additional work on responses to PACs in amphibians, reptiles, and semi-aquatic mammals, and development of molecular markers for early detection of biological responses to PACs would provide a stronger biological and ecological justification for regulating PAC emissions to protect Canadian wildlife.
Show more [+] Less [-]Use of chemical concentration changes in coastal sediments to compute oil exposure dates
2020
Xia, Junfei | Zhang, Wei | Ferguson, Alesia C. | Mena, Kristina D. | Özgökmen, Tamay M. | Solo-Gabriele, Helena M.
Oil spills can result in changes in chemical contaminant concentrations along coastlines. When concentrations are measured along the Gulf of Mexico over time, this information can be used to evaluate oil spill shoreline exposure dates. The objective of this research was to identify more accurate oil exposure dates based on oil spill chemical concentrations changes (CCC) within sediments in coastal zones after oil spills. The results could be used to help improve oil transport models and to improve estimates of oil landings within the nearshore. The CCC method was based on separating the target coastal zone into segments and then documenting the timing of large increases in concentration for specific oil spill chemicals (OSCs) within each segment. The dataset from the Deepwater Horizon (DWH) oil spill was used to illustrate the application of the method. Some differences in exposure dates were observed between the CCC method and between oil spill trajectories. Differences may have been caused by mixing at the freshwater and sea water interface, nearshore circulation features, and the possible influence of submerged oil that is unaccounted for by oil spill trajectories. Overall, this research highlights the benefit of using an integrated approach to confirm the timing of shoreline exposure.
Show more [+] Less [-]Spatial and vertical distribution, composition profiles, sources, and ecological risk assessment of polycyclic aromatic hydrocarbon residues in the sediments of an urban tributary: A case study of the Songgang River, Shenzhen, China
2020
Wang, Feng | Dong, Wenyi | Zhao, Zilong | Wang, Hongjie | Chen, Guanhan | Zhao, Yue | Huang, Jie | Zhou, Ting | Zhang, Shunli | Xu, Yunan | Wang, Feifei
In this study, the Songgang River (SR) was selected as a typical tributary that is heavily polluted by rapid urbanization and industrialization. The polycyclic aromatic hydrocarbon (PAH) distribution at five representative sampling sites from different urban functional areas was studied. The chemical and physical properties and spatial and vertical distribution of PAHs in sediments were investigated. PAH source identification and the ecological risks of the sediments were evaluated. The results suggested that the industrial zone and dense residential and commercial areas were the most contaminated areas of the SR, as the chemical and physical properties of total organic carbon content in sediments was the highest at the dense residential and commercial areas (0.1–4.5%); however, the acid volatile sulfide, total nitrogen, and total phosphorus contents were the highest in the industrial zone, with ranges of 700.0–1618.4 mg/kg dw, 22.4–3543.9 mg/kg dw, and 82.3–4550.7 mg/kg dw, respectively. The spatial distribution of residual PAHs in the sediment cores showed a wide variation among different urban functional areas, and the vertical characterization (0–300 cm) depicted a significant decreasing trend with depth and with an abrupt increase at 180 cm. The concentration of ∑16 PAHs ranged from 208.7 to 7709.8 ng/g dw, with the highest concentrations obtained in the industrial zone. The low molecular weight-PAHs (153–6720 ng/g dw) were predominant in the sediments. Furthermore, there were combined sources (biomass burning: 40.3%; fossil fuel combustion: 25.5%; mixed source: 21.5%; oil pollution: 12.7%) and a long term accumulation effect, with anthropogenic activities and industrial pollution as the major contributing sources. The concentrations of Nap, Acy, Ace, Flu, and Ant exceeded the lower limit of the sediment quality criteria, and higher toxic equivalent concentration values of the total carcinogenic PAHs were observed nearby the midstream of the SR, which may cause adverse biological effects and implies a need for regular monitoring.
Show more [+] Less [-]Long-term effects of an early-life exposure of fathead minnows to sediments containing bitumen. Part I: Survival, deformities, and growth
2019
Vignet, C. | Frank, R.A. | Yang, Zhunhe | Wang, Z. | Shires, K. | Bree, M. | Sullivan, C. | Norwood, W.P. | Hewitt, L.M. | McMaster, M.E. | Parrott, J.L.
The aim of this study was to investigate the long-term effects of a short exposure to natural sediments within the Athabasca oil sand formation to critical stages of embryo-larval development in fathead minnows (Pimephales promelas). Three different sediments were used: Ref sediment from the upper Steepbank River tested at 3 g/L (containing 12.2 ng/g ∑PAHs), and two bitumen-rich sediments tested at 1 and 3 g/L; one from the Ells River (Ells downstream, 6480 ng/g ∑PAHs) and one from the Steepbank River (Stp downstream, 4660 ng/g ∑PAHs). Eggs and larvae were exposed to sediments for 21 days, then transferred to clean water for a 5-month grow-out and recovery period. Larval fish had significantly decreased survival after exposure to 3 g/L sediment from Stp downstream, and decreased growth (length and weight at 16 days post hatch) in Ells and Stp downstream sediments at both 1 and 3 g/L. Decreased tail length was a sensitive endpoint in larval fish exposed to Ells and Stp downstream sediments for 21 days compared to Ref sediment. After the grow-out in clean water, all growth effects from the bitumen-containing sediments recovered, but adult fish from Stp downstream 3 g/L sediment had significant increases in jaw deformities. The study shows the potential for fish to recover from the decreased growth effects caused by sediments containing oil sands-related compounds, but that some effects of the early-life sediment exposure occur later on in adult fish.
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