Dioxin Concentrations Research Articles

Association between chronic long-term exposure to airborne dioxins and breast cancer

Breast cancer is the most common type of cancer among women. Environmental pollutants, specifically those with endocrine disrupting properties like dioxins, may impact breast cancer development. Current epidemiological studies on the association between exposure to dioxins and the risk of breast cancer show inconsistent results. To address these uncertainties, our objective was to investigate the impact of airborne dioxin exposure on breast cancer risk within the E3N cohort, encompassing 5222 cases identified during the 1990–2011 follow-up and 5222 matched controls. Airborne dioxin exposure was assessed using a Geographic Information System-based metric considering residential proximity to dioxin emitting sources, their technical characteristics, exposure duration and wind direction. Additional analyses were performed using dioxin concentrations estimated by a chemistry transport model, CHIMERE. The results suggest a slightly increased risk between cumulative dioxin exposure at the residential address and overall breast cancer risk (adjusted odds ratio (OR) = 1.03, 95% confidence interval (CI): 0.99–1.07, for a one standard deviation (SD) increment among controls (14.47 log-μg-TEQ/m2). The associations remained consistent for sources within 3, 5, and 10 km, and when restricting exposure to dioxin emissions from household waste incinerators. Similar OR estimates (OR = 1.02, 95% CI: 0.97–1.07, for a one SD increment) were obtained using the CHIMERE model. The findings of this study suggest the possibility of an increased risk of breast cancer associated with long-term residential exposure to dioxins and emphasize the importance of efforts to mitigate air pollution exposure.

The Toxicity Leaching and the Cement Admixtures Properties with Incineration Fly Ash of Different Furnace Types.

Incineration of fly ash is a hazardous solid waste, and there are two types of furnaces used for production. The impact of furnace types on the properties and toxicity of incineration fly ash was studied. The resource utilization of incineration fly ash has been tested. The results showed that circulated fluidized bed (CFB) ash and grate (GF) ash were alkaline materials, dioxin content ranged between 98 and 359 ng-TEQ/kg, and heavy metals exceeded 7700 ppm. The leaching of Zn in CFB ash was 110.474 ppm, and that in the GF ash was 5.985 ppm. The chlorine content in GF ash was 27.07%, 2.7 times that of CFB ash. When the content was 5%, GF ash promoted cement grinding and improved the 3-day compressive strength of cement, which was 35.55% higher than the control sample. CFB ash generates hydrogen gas during the hydration process, causing volume cracking. When 20% GF ash was added, the hydration heat release peak appeared 10.5 h ahead of time. According to the Chinese standard GB 175-2023, the maximum dosages of CFB ash and GF ash in cement were 0.22 and 0.57%. There was no risk of excessive leaching of heavy metals. During cement production with CFB and GF ash, attention should be paid to the issues of chlorine and dioxins.

Carbonation pretreatment enhance the hydrothermal detoxification of municipal solid waste incineration fly ash

A combined carbonation-hydrothermal method is proposed here for the harmless treatment of water-washed municipal solid waste incineration fly ash (WMSWI-FA). This study investigates the effect of temperature on the hydrothermal detoxification of dioxins and assesses the effect of carbonation pretreatment on the detoxification of dioxins and the stabilization of heavy metals in WMSWI-FA. The results demonstrate that elevated temperatures benefit the detoxification of dioxins, with detoxification efficiencies improving from -31.16% to 81.54% as temperatures increase from 180°C to 260°C. After carbonation pretreatment, dioxin concentrations were decreased from 36.31 ng-TEQ/kg to 30.62 ng-TEQ/kg and detoxification efficiency increased from 81.54% to 82.41%. It is primarily attributed to pH changes caused by carbonation pretreatment, which significantly affect the dechlorination reaction of dioxins. Additionally, carbonation pretreatment effectively stabilizes heavy metals such as Pb, Zn, and As through precipitation and physical encapsulation. This study concludes that combining carbonation pretreatment with hydrothermal treatment offers a promising strategy for the safe and effective treatment of WMSWI-FA.

Catalytic Co-oxidation of Dichloromethane and non-chlorinated VOC over HxPO4-RuOx/CeO2, Pt/HZSM-5 and dry-mixed Ru-Pt Catalysts

Industrial flue gases contain chlorinated VOCs (CVOCs) and hydrocarbons, along with various contaminants. Although previous studies have primarily focused on the catalytic oxidation of individual VOCs, the activity of VOCs in mixtures often differs from that of individual compounds. The catalytic oxidation of dichloromethane in the presence of a second VOC (ethyl acetate, n-hexane, and toluene) was investigated using HxPO4-RuOx/CeO2, Pt/HZSM-5, and dry-mixed Pt-Ru catalysts. The dry-mixed catalyst combines the excellent dechlorination ability of HxPO4-RuOx/CeO2 with the oxidation capability of Pt/HZSM-5. A mixture of 1000 ppm toluene and 100 ppm dichloromethane is fully oxidized over the Ru-Pt catalyst at 300 °C, 30 °C lower than the T100 observed on the other two catalysts. DFT calculation reveals that the activation of toluene and dichloromethane occurs on Pt and Ru sites, respectively, dechlorinated by proton of phosphate. Furthermore, by-product dioxin content on Pt-Ru is significantly below 0.1 ng TEQ Nm−3 limit.

The burden of cancer attributable to dietary dioxins and dioxin-like compounds exposure in China, 2000–2020

Dioxin is a typical class of persistent organic pollutants (POPs) that could cause cancer. In China, the contribution of dietary dioxins to the cancer burden remains underexplored. This study evaluates the cancer risk and burden due to dietary dioxins and dioxin-like compounds among Chinese residents from 2000 to 2020. Based on adjustments in China’s dioxin policies, the study period was divided into three stages with split years of 2007 and 2014 to estimate the toxic equivalent (TEQ) of dioxins. Participants in dietary surveys conducted in 31 provinces were included. Dietary exposure to dioxins was estimated in a probability model and compared with the provisional tolerable monthly intake (PTMI). The risk was assessed using carcinogenic slope factors and expressed as the incremental lifetime cancer risk (ILCR). A two-stage model evaluated the burden of cancer attributable to dietary dioxins and dioxin-like compounds. Among all food categories, the highest concentration of dioxins and dioxin-like compounds was observed in aquatic foods at 0.15 pg TEQ/kg. Median dietary exposure to dioxins among Chinese residents decreased from 12.39 pg TEQ/kg/month to 8.72 pg TEQ/kg/month between 2000 and 2020. Consequently, the ILCR due to dietary dioxins declined from 6.44 × 10-5 to 4.53 × 10-5. The health risks were higher in younger groups and among residents of coastal areas (P < 0.001). The burden of cancer attributable to dietary intake of dioxins and dioxin-like compounds in the Chinese population in 2000–2007, 2008–2014, and 2015–2020 was 2.25 (2.09–2.42) per 100,000, 2.20 (2.06–2.35) per 100,000, and 1.68 (1.60–1.77) per 100,000, respectively. Furthermore, the disease burden was highest for prostate cancer in men and for breast cancer in women. The dioxin management policies has reduced the burden of cancer attributable to dietary exposure to dioxins and dioxin-like compounds in China. However, excess exposure in coastal areas and children remains a priority for attention.

Dioxin concentrations and congener distribution in biomass ash from small to large scale biomass combustion plants.

Biomass plays a pivotal role in global energy production, with a significant share allocated for industrial heat and power generation. The combustion of biomass generates biomass ash, which is widely utilized as a fertiliser. However, concerns arise regarding the presence of dioxins in biomass ash, which may limit its continued use. Dioxins are toxic compounds listed under the Stockholm Convention due to their persistence and detrimental effects on human health and the environment. This study investigates the dioxin content in biomass ashes produced in various combustion plants with a capacity of 1-50MWth in Estonia, where biomass is widely used for heating and power production. The research encompassed samples from nine biomass combustion plants with varying technical parameters considering both bottom and fly ash. Dioxin concentrations were determined for 7 polychlorinated dibenzo-p-dioxins (PCDDs), 10 polychlorinated dibenzofurans (PCDFs), and 12 dioxin-like PCBs (PCBs). The results indicate that dioxin TEQ content in all samples was well below the European Union's (EU) POP Regulation limit of 5µg TEQ/kg, with most values being at least tenfold lower. However, some samples failed to meet the EU Fertilising Products Regulation's threshold of 20ng TEQ/kg. Notably, fly ash exhibited higher dioxin concentrations than bottom ash. While PCBs were in significant concentrations, PCDDs dominated the overall dioxin TEQ content. This study provides essential insights into the dioxin content in biomass ash and its correlation with current EU regulatory limits. It also highlights the complex distribution of dioxin congeners, particularly PCBs, within biomass ash, emphasizing the continued research's importance.

Prediction of particulate matter during the combustion of wood pellets with the addition of face mask waste

The amount of plastic waste has increased enormously due to the using of protective equipment in order to slow down the viral transmission of COVID-19. The usage of protective face masks brought a huge environmental burden. Moreover, a lot of disposed masks enter the ocean or end on landfills, where they threaten the ecosystem. It is still necessary to deal with environmental-friendly disposal or to reuse and recycle of these masks. This article is focused on the disposal of FFP2 face masks by their co-combustion with wood. Due to the possibility of produced emissions, disintegrated masks were blended with spruce and beech sawdust and compared with pure wood. These materials were compressed into pellets with the aim of higher density. The emissions such as carbon monoxide, nitrogen oxides, sulphur oxides and particulate matter were measured during pellet combustion. The heat output of the automatic pellet boiler was also determined. The filters with captured particulate matter were sent to the investigation of dioxin and furan concentration. Except for this, the regression model has been created for the prediction the concentration of particulate matter. The results confirmed that the co-combustion of wood with FFP2 masks could be one of the environmental-friendly ways of face mask disposal when they are used as an additive in a small percentage. The fuel composition and operational conditions are also very important parameters during the combustion process. However, the concentration of gas emissions and particulate matter, as well as heat output, did not change significantly, when the content of FFP2 masks of 5 % or 10 % was used.

AI-based tree modeling for multi-point dioxin concentrations in municipal solid waste incineration

Numerous investigations have shown that the municipal solid waste incineration (MSWI) has become one of the major sources of dioxin (DXN) emissions. Currently, the primary issue that needs to be addressed for DXN emission reduction control is the online measurement of DXN. Data-driven AI algorithms enable real-time DXN concentration measurement, facilitating its control. However, researchers mainly focus on building models for DXN emissions at the stack. This approach does not allow for the construction of models that online measurement of DXN generation and absorption throughout the whole process. To achieve optimal pollution control, models that encompass the whole process are necessary, not just models focused on the stack. Therefore, this article focuses on modeling the whole process of DXN concentrations, including generation, adsorption, and emission. It uses machine learning techniques based on advanced tree-based data-driven deep and broad learning algorithms. The determination of data characteristics at different phases is grounded in the understanding of the DXN mechanism, offering a novel framework for DXN modeling. State-of-the-art tree-based models, including adaptive deep forest regression algorithm based on cross layer full connection, tree broad learning system, fuzzy forest regression, and aid modeling technologies, are applied to handle diverse data characteristics. These characteristics encompass high-dimensional small samples, low-dimensional ultra-small size samples, and medium-dimensional small samples across different phases related to DXN. The most interesting is the robust validation where the proposed a whole process tree-based model for DXN is validated using nearly one year of authentic data on DXN generation, adsorption, and emission phases in an MSWI plant of Beijing. The proposed modeling framework can be used to explore the mechanism characterization and support the pollution reduction optimal control.

Tissue distribution and exposure risk assessment of dioxins, dioxin-like polychlorinated biphenyls and perfluoroalkyl substances in red swamp crayfish

Significant attention has been paid to the adverse effects of dioxins, dioxin-like polychlorobiphenyls (DL-PCBs) and per-and polyfluoroalkyl substances (PFAS) in environment and food on ecosystem and human health. However, limited information exists regarding the occurrence, tissue distribution and exposure risk of these pollutants in crayfish. This study investigated tissue-specific distribution characteristics, influence factors and exposure risk of dioxins, DL-PCBs and PFAS in crayfish. Dioxins, DL-PCBs, and PFAS were detected in crayfish samples, with concentrations ranging from 0.361 to 1.91 pg TEQ g−1 for sum dioxins and DL-PCBs, and 1.54–21.2 ng g−1 for sum PFAS. The highest concentrations of dioxins, DL-PCBs TEQ and total PFAS were found in crayfish viscera and accounting for over 69% of the relative body burden (RBBs) of these pollutants. The specific-tissue distribution of these pollutants linked to tissue fat and protein content and log Kow and molecular weights of homologues. The consumption of crayfish edible tissue posed no health risks from exposure to dioxins and DL-PCBs as well as sum 4 PFAS in adults. However, consumption of crayfish viscera significantly increased exposure risk. This study can provide valuable insights into the tissue-specific distribution and human exposure risks associated with dioxins, DL-PCBs and PFAS in crayfish.

Aquaculture sludge as feed for black soldier fly: Transfer of chemical and biological contaminants and nutrients

Aquaculture sludge (uneaten feed and faeces) is nutrient rich and has potential as feed for insects. The aim of this study was to investigate the transfer of chemical and biological contaminants, as well as nutrients, from aquaculture sludge to black soldier fly larvae. The larvae were reared on a sludge mixture made of different sludges collected from Norwegian freshwater salmonid facilities. The sludge was spiked with four common salmon pathogens: Infectious Pancreatic Necrosis Virus, Infectious Salmon Anemia virus, Yersinia ruckeri or Mycobacterium salmoniphilum. During the 15 days of growth on sludge, the black soldier fly larvae accumulated valuable nutrients including protein, fat, eicosapentaenoic acid, iron, manganese, zinc and selenium. The larvae also accumulated undesirable substances including cadmium, mercury, dioxins and polychlorinated biphenyls. The concentrations of dioxins exceeded the EU maximum level set for animal feed. None of the salmon pathogens that were spiked to the sludge were detected in the black soldier fly larvae. This study reports low risk of transfer of salmon pathogens from sludge to insect larvae, and showed that the transfer of heavy metals, minerals and metalloids are in accordance with earlier studies. The large variations in levels of heavy metals between batches of sludge can cause levels in BSF exceeding the EU maximum levels, and thus indicate a need for monitoring of the proposed value chain. The transfer of dioxins from sludge to insects, reported for the first time in this paper, would be of special interest for future research, with special focus on risk mitigation.

Domestic fish for more versatile and safer consumption EU‐fish IV

Abstract Fish is an important part of nutrition and well‐being. The challenge of Finnish wild fish is contaminants which accumulate in some species in higher concentrations, partially limit the usability of the fish in the food/feed market and weaken the assessment of the state of the marine environment. The aim of this study was to obtain data on the amounts of nutrients and contaminants in domestic fish species that are commercially important or should be increased in use according to national plans. The aim was also to produce information for updating the national fish use recommendations. The concentrations of contaminants in Finnish fish were mostly below the maximum levels set by the EU. The trend of dioxin and PCB compound concentrations in the Baltic Sea has been declining since the 1980s, and the concentrations in Baltic herring appear to have settled around or below the maximum levels in all sea areas and size classes. The PFAS concentrations in the studied fish samples were within the maximum limits, except for Baltic herring in the Archipelago Sea and the Bothnian Sea. Additionally, the PFAS concentrations in Baltic herring rose quite sharply between 2009 and 2023. During the current study, PFAS concentrations in Baltic herring from the same sea area and size classes increased significantly from autumn 2022 to spring 2023. The seasonal trend was suspected to be related to the fish's diet, but factors affecting PFAS concentrations in fish, such as the impact of seasons and fitness (function of weight and size of the fish), need further investigation, and PFAS concentrations in Baltic herring should be monitored. PBDE concentrations in Finnish fish were found to be very low, although they exceeded the environmental quality standard. Mercury concentrations in fish, except for two samples, were lower than the maximum levels set by Commission Regulation (EU) 2023/915. The proportion of methylmercury in total mercury was 56–94% in different fish species. Inorganic arsenic concentrations in all fish samples were below the detection limit of 0.01 mg/kg. The highest concentrations of omega‐3 fatty acids were measured in Baltic herring and vendace. Fish caught from marine areas had higher vitamin D concentrations than those from inland waters, and there was significant variation in concentrations within fish species. With current food consumption and concentration data, the health benefits of fish consumption outweigh the health risks associated with contaminants in fish for all age groups. The greatest health benefits are seen in those over 45 years old, where fish consumption reduces the burden of diseases such as cardiovascular diseases and breast cancer, as well as overall mortality. On a national scale, the current use of domestic and imported fish is estimated to reduce the disease burden annually by nearly 70,000 disability‐adjusted life years (DALYs). As a conclusion, the health benefits of fish consumption outweigh the harms of contaminants in all age groups. Increasing the consumption of fish in accordance with nutritional recommendations would benefit the health of the population. For children and expectant or breastfeeding mothers, a diverse fish consumption is useful. The safe use recommendations of the Finnish Food Authority help this risk group to direct their fish consumption to fishing areas and fish species with the lowest amounts of contaminants.

Effects of dioxin exposure on reproductive and thyroid hormone levels and male sexual function in airbase military workers in Vietnam.

Dioxins are endocrine disruptors that may disturb male sexual and reproductive function. Studies on human populations are limited, and their results are controversial. This study evaluated the impact of dioxin exposure on reproductive and thyroid hormone levels and sexual function in men. A total of 140 men working in four military airbases (three bases were formerly contaminated with dioxin by the herbicide spraying campaign in the Vietnam War) were recruited to measure the serum dioxin levels. Four reproductive hormones (testosterone, follicle-stimulating hormone, luteinizing hormone (LH), and prolactin) and three thyroid hormones (free triiodothyronine (FT3), free thyroxin (FT4), and thyroid stimulating hormone) were measured. Male sexual function endpoints including sexual drive, erection, ejaculation, problems, and overall satisfaction were assessed by the Brief Male Sexual Function Inventory. The percentage of subjects with low testosterone and LH levels was 19.6% and 16.7%, respectively. Dioxins, especially 2,3,7,8-tetrachlorodibenzo-P-dioxin and toxic equivalent concentrations of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans, were inversely associated with testosterone and prolactin levels, but positively associated with FT3 and FT4, and showed adverse relationships with sexual function, such as sexual drive, problems, and overall satisfaction. Our results suggested that exposure to dioxin disrupts the homeostasis of reproductive and thyroid hormones leading to adverse effects on male sexual function.

Process system simulation of coupled pyrolysis disposal of domestic waste in coal-fired boiler and pilot study on dioxin emission

The disposal of domestic waste has become a critical and costly problem. Incineration for power generation is currently the primary domestic waste treatment method. Due to its small capacity and low parameters, domestic waste incineration is generally uneconomical and associated with significant risks to public health and environmental safety. The coal-fired power plants are generally characterized with huge capacity and high parameters, consequently resulting in much higher power generation efficiency with lower cost emission control. This indicates that co-disposal of domestic waste using existing coal-fired units may significantly reduce its treatment costs associated with the improvement of utilization efficiency and environmental risks. Base on this, a highly-flexible coupling of pyrolysis-pretreated solid waste in pulverized coal furnace is proposed in this paper, and field tests and numerical simulations have been carried out separately according to the process route. The results show that after coupling with pulverized coal boiler, domestic waste pyrolysis pretreatment unit can operate self-sustainably without external energy supply and the process route is feasible. Furthermore, the coupled co-combustion of domestic waste pyrolysis products and pulverized coal was simulated by fluent software. Compared with pure pulverized coal combustion, mixing domestic waste pyrolysis products can promote pulverized coal combustion in the furnace and help the pulverized coal boiler to burn stably at low load. The emission concentrations of NOx at the outlet of the furnace are 530 ppm, 545 ppm and 478 ppm respectively when pulverized coal is burned purely and mixed with 100 t/d and 200 t/d domestic waste. the NOx emissions could be reduced to a certain extent by mixing domestic waste. On the basis of previous research, the field test of coupling disposal of domestic waste by pulverized coal boiler was carried out, and the dioxin concentration in flue gas and fly ash was tested emphatically. The results show that when the amount of waste is less than 4 %, the concentration of dioxin in flue gas is 0.0107 ng TEQ/m3, which meets the latest emission standard of air pollutants in Shanghai coal-fired sludge power plant of 0.02 ng TEQ/m3. Low proportion of domestic waste will not increase the production and emission of dioxins. These studies show that it is feasible and promising to treat municipal solid waste with low coupling ratio by using existing coal-fired units.

A study of the stabilization and solidification of heavy metals in co-vitrification of medical waste incineration ash and coal fly ash

Medical waste incineration ash (MWIA) has significant concentrations of heavy metals, dioxins, and chlorine that, if handled incorrectly, might cause permanent damage to the environment and humans. The low content of calcium (Ca), silicon (Si), and aluminum (Al) is a brand-new challenge for the melting technique of MWIA. This work added coal fly ash (CFA) to explore the effect of melting on the detoxication treatment of MWIA. It was found that the produced vitrification product has a high vitreous content (98.61%) and a low potential ecological risk, with an initial ash solidification rate of 67.38%. By quantitatively assessing the morphological distribution features of heavy metals in ashes before melting and molten products, the stabilization and solidification rules of heavy metals during the melting process were investigated. This work ascertained the feasibility of co-vitrification of MWIA and CFA. In addition, the high-temperature melting and vitrification accelerated the detoxification of MWIA and the solidification of heavy metals.

Exposure to environmental pollutants selects for xenobiotic-degrading functions in the human gut microbiome

Environmental pollutants from different chemical families may reach the gut microbiome, where they can be metabolized and transformed. However, how our gut symbionts respond to the exposure to environmental pollution is still underexplored. In this observational, cohort study, we aim to investigate the influence of environmental pollution on the gut microbiome composition and potential activity by shotgun metagenomics. We select as a case study a population living in a highly polluted area in Campania region (Southern Italy), proposed as an ideal field for exposomic studies and we compare the fecal microbiome of 359 subjects living in areas with high, medium and low environmental pollution. We highlight changes in gut microbiome composition and functionality that were driven by pollution exposure. Subjects from highly polluted areas show higher blood concentrations of dioxin and heavy metals, as well as an increase in microbial genes related to degradation and/or resistance to these molecules. Here we demonstrate the dramatic effect that environmental xenobiotics have on gut microbial communities, shaping their composition and boosting the selection of strains with degrading capacity. The gut microbiome can be considered as a pivotal player in the environment-health interaction that may contribute to detoxifying toxic compounds and should be taken into account when developing risk assessment models. The study was registered at ClinicalTrials.gov with the identifier NCT05976126.

A snapshot of bacterial endophytes isolated from the roots of Vetiver grass (Chrysopogon zizanioides) grown at Bien Hoa airbase, Dong Nai province

Vetiver grass (Chrysopogon zizanioides) with a strong root system has been widely used for environmental pollution treatment. Recently, this grass has been cultivated at Bien Hoa airbase to mitigate dioxin concentration in the contaminated soil. Bacterial endophytes have been recognized to play key roles in plant growth promotion and responses of plant hosts to environmental factors. However, a beneficial association between endophytic bacteria and Vetiver grass root system grown in dioxin-contaminated soil has not been elucidated. In the present study, we isolated sixteen endophytic bacterial strains from the roots of Vetiver grass. The results of DNA sequencing of the 16S rRNA gene revealed that these culturable bacterial endophytes belong to 9 species of different genera. Four strains, including Klebsiella variicola B1, Enterobacter cloacae B4, Enterobacter kobei B6, and Enterobacter cloacae B11, produce high amounts of indol acetic acid (IAA). Strains K. variicola B1 and E. cloacae B4 also produce phytase and phosphatase to dissolve phytate and phosphate, respectively. These strains were selected to evaluate their abilities in promoting the growth of tomato plants as a model. After 28 days of inoculation with the tested strains through the roots, tomato plants grew 19% to 22% faster than the control plants. Conclusively, this study shows for the first time the successful isolation of endophytic bacteria from the roots of Vetiver grass cultivated in dioxin-contaminated soil, and some culturable bacterial strains exhibit as promising candidates for plant growth promotion.

Preparation and Properties of Expansive Backfill Material Based on Municipal Solid Waste Incineration Fly Ash and Coal Gangue

To realize the large-scale utilization of municipal solid waste incineration (MSWI) fly ash in the field of building materials and to reduce the cost of coal mine backfill mining, the effects of the mixing ratio of cementitious materials, the particle size distribution of aggregates, and the amount and mass concentration of cementitious materials on the properties of backfill materials were experimentally investigated, and the microstructure of the hydration products was analyzed. The results showed that as the mass ratio of MSWI fly ash to bottom ash increased, the rate of expansion of the cementitious system continued to increase, and the compressive strength of the cementitious system continued to decrease. The Al (aluminum) and AlN (aluminum nitride) in the fly ash reacted with water to generate gas, causing the expansion of the cementitious materials; NaOH increased the alkalinity of the solution, which promoted the formation of more bubbles, thereby improving the expansion performance of the cementitious material. When the content of NaOH was 0.9%, the sample rate of expansion could reach 15.9%. The addition of CaCl2 promoted the early hydration reaction of the cementitious material, forming a dense microstructure, thus improving the early strength and rate of expansion of the cementitious material. The compressive strength of the backfill body increased as the fractal dimension of the aggregate particles increased, and the particle grading scheme of group S1 was optimal. The 1-day, 3-day, and 28-day strengths of the backfill body of group S1 reached 0.72 MPa, 1.43 MPa, and 3.26 MPa, respectively. It is recommended to choose a backfill paste concentration ranging between 78.5% and 80% and a reasonable amount of cementitious material between 20% and 25%. After the MSWI fly ash was prepared as a backfill material, the leaching of potentially harmful elements in the fly ash was greatly reduced, and the concentration of dioxin was reduced to 13 ng TEQ/kg. This was attributed to the dilution of the cement, the physical encapsulation of gel products, and the isomorphous replacement of Ca2+ in calcium aluminate chloride hydrate.

Assessing the bioaccumulation and translocation potential of vetiver grass for dioxins phytoremediation in Bien Hoa airbase, Viet Nam

Dioxins (PCDD/Fs) are well-known toxic organic pollutants that accumulate in the environment and the food chain, imposing a risk to human health and the ecosystem. Due to the use of dioxin-contaminated herbicides during the US-Vietnam War, there are several hotspots in Vietnam with very high levels of dioxins. Phytoremediation has been increasingly developed in recent decades because of its low cost and environmental-friendly aspect. Vetiver grass is a plant that can remediate both organic and inorganic agents. In this study, the uptake and translocation of dioxins in Vetiver grass (Chrysopogon zizanioides) from the dioxin-contaminated soil was investigated in a field experiment on the Bien Hoa airbase, Vietnam. An experimental area was divided into six plots, of which three were planted with Vetiver grass and three served as control plots, with the initial dioxin concentrations as following: FC2&gt;FC3&gt;FC1&gt;FT2&gt;FT3&gt;FT1. Vetiver grass had grown well on the dioxin-contaminated soils, yielding high biomass and the level of dioxins in the roots of vetiver grass was positively correlated (r2 = 0.67; p&lt;0.01) with its growth rate. During the first year of cultivation, Vetiver grass had the greatest capacity to efficiently accumulate dioxin. Accumulation occurs in the roots, with BAF&gt;1 throughout the entire experiment period for FT3, and in the first year for FT1 and FT2. The dioxin translocation from the roots to the shoots was significantly lower than the BAF and less than one (TF&lt;1), with the first and second sampling times having the highest values compared to the others. Dioxin concentrations do not provide a reliable indicator of its bioavailability but numerous other factors, such as physicochemical properties of the soil and microbes. Our study aims to contribute significant insights to capability of Vetiver grass to accumulate and translocate dioxins, hence the arsenal of dioxin remediation. Furthermore, we envisage translating our findings into practical applications in other areas, considering optimized planting techniques, growth conditions, and long-term sustainability.

Emission and distribution characteristics of PCDD/Fs during the co-processing of various solid wastes in coal-fired boilers in China

The advancement of co-processing solid wastes in coal-fired boilers is significant for waste recycling and contributes to the sustainable development of the coal-fired power industry. However, concerns over the emission of dioxins during co-processing have prompted a comprehensive investigation into the dioxin emission properties. In this study, the PCDD/F emission concentrations of seven coal-fired boilers, including three pulverized coal boilers and four circulating fluidized bed boilers were examined. The results indicate that co-processing solid wastes in coal-fired boilers did not lead to an increase in the mass concentration of dioxins in either the flue gas or solid samples, and the international toxic equivalents (I-TEQ) of dioxins in the flue gas complied with prevailing emission standards (0.1 ng I-TEQ/Nm3) in China, proving that coal-fired boilers co-processing would not raise the emission risk of dioxins. The types of waste during co-processing had minimal effect on the I-TEQ of dioxins. A significant proportion of PCDD/Fs was observed in the ash samples, while only 13.0–25.7% and 0.7–6.8% of dioxins were distributed in the boiler slag and the flue gas, respectively. The emission factor of dioxins under the blank conditions ranged from 0.009 to 0.327 ng I-TEQ/kg-coal, while it ranged from 0.015 to 0.129 ng I-TEQ/kg-(coal+waste) under the co-processing conditions. The reduction of emission factor under co-processing condition could be attributed to the significant decrease of dioxins I-TEQ.

A Comprehensive Evaluation of Dioxins and Furans Occurrence in River Sediments from a Secondary Steel Recycling Craft Village in Northern Vietnam.

This first study investigated the presence of dioxins and furans in river sediments around a craft village in Vietnam, focusing on Secondary Steel Recycling. Sediment samples were collected from various locations along the riverbed near the Da Hoi Secondary Steel Recycling village in Bac Ninh province. The analysis was conducted using a HRGC/HRMS-DFS device, detecting a total of 17 dioxin/furan isomers in all samples, with an average total concentration of 288.86 ng/kg d.w. The concentrations of dioxin/furan congeners showed minimal variation among sediment samples, ranging from 253.9 to 344.2 ng/kg d.w. The predominant compounds in the dioxin group were OCDD, while in the furan group, they were 1,2,3,4,6,7,8-HpCDF and OCDF. The chlorine content in the molecule appeared to be closely related to the concentration of dioxins and their percentage distribution. However, the levels of furan isomers did not vary significantly. The distribution of these compounds was not dependent on the flow direction, as they were mainly found in solid waste and are not water-soluble. Although the hepta and octa congeners had high concentrations, when converted to TEQ values, the tetra and penta groups (for dioxins) and the penta and hexa groups (for furans) contributed more to toxicity. Furthermore, the source of dioxins in sediments at Da Hoi does not only originate from steel recycling production activities but also from other combustion sites. The average total toxicity was 10.92 ng TEQ/kg d.w, ranging from 4.99 to 17.88 ng TEQ/kg d.w, which did not exceed the threshold specified in QCVN 43:2017/BTNMT, the National Technical Regulation on Sediment Quality. Nonetheless, these levels are still concerning. The presence of these toxic substances not only impacts aquatic organisms in the sampled water environment but also poses potential health risks to residents living nearby.