Formation Of Persistent Organic Pollutants Research Articles

Influence of aeration-induced air–water interfaces on pollutant degradation in water treatment: A theoretical and experimental study

Advanced oxidation processes (AOPs) based on hydroxyl radicals (OH)-dominant pathway are the most important technologies for the removal of bio-recalcitrant organic pollutants in industrial wastewater. Air–water interface formed by aeration is one of the factors that affect the removal efficiency of pollutants in AOPs. In this work, the mechanistic and kinetic insights into the roles of air–water interface on the hydroxylation of three chlorophenols (CPs) in UV/H2O2 process have been investigated via theoretical calculation and experimental methods. Results show that CPs is more prone to accumulate at the air–water interface as the number of chlorine substituents increases. Consequently, the hydration reaction of CPs occurring at the interfacial influence the electron transfer associated with OH, leading to the non-oxidative consumption of OH. This interfacial reaction diminishes degradation efficiency, resulting in the formation of persistent organic pollutants. Herein, in UV/H2O2 degradation of 2,4,6-TCPs, persistent free radical (PFRs), as well as 1,3,7,9-TCDD and 2,3,6-Trichloro-4-(2,4,6-trichlorophenoxy)phenol, were identified using EPR spectroscopy and LC-Q-TOF-MS mass spectrometry, respectively. Altogether, this work provides a comprehensive understanding of the roles of aeration on OH-initiated degradation behavior of chlorinated phenol pollutants.

IDENTIFICATION SOURCES OF EMISSION PERSISTENT ORGANIC POLLUTANTS IN UKRAINE AND WAYS TO REDUCE EMISSIONS FROM THE MOST PROBLEMATIC SOURCES

Persistent organic pollutants (POPs) belong to a group of toxicants, which, due to their extremely dangerous impact on human health, is regulated by a special international agreement — the Stockholm Convention on POPs. Each Party to the Convention must develop and consistently update the National Implementation Plan for the requirements of this Convention. Ukraine developed a National Implementation Plan in 2007. Today, the plan needs to be revised and supplemented, taking into account the changes that have occurred in the structure of sources and volumes of POP emissions. During the time that has passed since the development of the first edition of the National Plan, new approaches have appeared to prevent the emission of POPs. The article contains the results of an expert analysis of changes in the volume and structure of POP emission sources in the world and in Ukraine. Calculations of POPs emissions, made according to the UNEP methodology, showed that the largest sources of POPs emissions in Ukraine are: sintering production and electric arc smelting of steel in ferrous metallurgy; production of thermal and electrical energy from biomass in the energy industry; incineration of solid household and hazardous waste. For the most problematic sources of POP emissions, the most promising methods and practices for preventing the formation and removal of POPs from the products of technological process have been determined. Bibl. 25, Fig. 4, Tab. 3.

Plastic waste: assessment of the prosesses of its formation and management in the North-Western Black Sea Coast Regions

Plastic waste represents a specific component within the municipal solid waste structure because of the peculiarities of its formation, possibility of reuse and ecological consequences of environmental pollution. In particular, growing consumption of plastic is accompanied by a constant level of recycling (4-8%). This leads to accumulation of plastic waste in the environment. The article presents data on the content of plastic waste in the municipal solid waste of Ukrainian cities. According to the data the content of plastic waste within the municipal solid waste amounts to 10-12%. Plastic waste is mainly represented by polyethylene and polyethylene terephthalate (more than 60%). It was discovered that plastic recycling companies import almost a third of recycled materials from Europe, while almost 84% of plastic is still ends brought to landfills. The analysis of the situation with separate collection of the municipal solid waste in the North-Western Black Sea Coast Region (namely Odesa, Mykolaiv and Kherson Regions) indicates a low level of secondary raw materials extraction. It is also exacerbated by the fact that only 75% of the population receives services for centralized collection of the municipal solid waste. It is estimated that almost 160,000 tons of plastic waste were brought to the landfills of Odesa Region in 2019. This volume is equal to the workload of existing plastic processing enterprises of Ukraine. So, as exemplified by Odesa Region, the research aimed at assessing the resource potential of plastic waste by main categories and in terms of clustering of the region, in accordance with the Regional Waste Management Plan project. It also describes the environmental consequences of leaving waste plastic materials in the environment – contamination with microplastics and formation of persistent organic pollutants. Moreover, it indicates that the municipal plastic waste is a significant source for such substances formation during thermal and mechanical destruction processes taking place within a landfill's body or marine environment. The research analyzes the main reasons for a low level of plastic waste use in the region. One of them is a lack of conditions allowing the citizens to collect plastic waste separately from the rest of their waste.

Biological wastewater treatment plants as sources of environmental pollution by persistent organic pollutants (on the example of Odesa industrial-and-urban agglomeration)

Formulation of the problem. Effective mechanism of wastewater treatment (WT) are important components of reducing anthropogenic load on the environment. One of the most widespread mechanisms of urban wastewater treatment is the biological treatment on a Biological Wastewater Treatment Plant (BWTP). However, increasing the nomenclature of pollutants concentrated in urban wastewater seriously affects the effectiveness of WT on BWTPs, which are not intended for such a wide spectrum of specific pollutants such as, in particular, Persistent Organic Pollutants (POPs). The control of their intake into the environment must be regulated according to the Stockholm convention. The goal of the research is the evaluation of the intake of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) into the environment from the wastewater of Odesa Industrial-and-Urban Agglomeration (IUA) and determining the volumes of their accumulation in the sea environment. Purpose. The assessment of the amount of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) entering the environment with the wastewater from Odesa IUA and determining the amount of their accumulation in the sea environment. Methods. In our research, all available official methods of calculation of the unintentional formation of POPs were reviewed, as a result – the main and most complete methods were selected: «UNEP (2013). Toolkit for Identification and Quantification of Releases of Dioxins, Furans and Other Unintentional POPs» and «EMEP/EEA air pollutant emission inventory guidebook. Technical guidance to prepare national emission inventories, 2019». For evaluation of PCDD/F accumulation in the sea environment an improved by authors methodology for calculation of PCDD/F accumulation with their cumulative effect and half life taken into account was used. Results. The work provides justification for the necessity of use of calculation methodologies for determing the intake of PCDD/F to the sea environment adjacent to Odesa IUA; annual massed of PCDD/F entering the sea environment as part of treated, insufficiently treated and untreated wastewater are calculated; massed of PCDD/F that accumulate in waste activated sludge (WAS) on BWTP are calculated; volumes and specifics of PCDD/F accumulation in the sea basin, where the wastewater of Odesa IUA is being discharged to are determined using the improved methodology that enables taking into account the cumulative effect and half life period of these substances; mass and concentration of PCDD/F, immobilized in WAS, are determined, the excess level of concentration of PCDD/F in WAS compared to the maximum permissible concentration is determined. The total accumulation of PCDD/F in the sea environment over 2007-2017 period is determined. Conclusions. It was established that the use of calculation methodologies for evaluating PCDD/F volumes in the water environment is the only and necessary condition for satisfying the requirements of the Stockholm convention due to the impossibility of performing a regular instrumental monitoring of PCDD/F intake into the water environment. The use of suggested by us improved methodology for calculation of PCDD/F accumulation with their cumulative effect and half-life period taken into account allows for calculation of PCDD/F masses that were formed throughout the year under consideration, taking into account the PCDD/F masses that were formed during previous years as well.

Evaluation of certain pollutants generation inside municipal solid waste landfills

Municipal solid waste disposal sites act as sources of secondary pollution of the environment with waste destruction products that undergo further chemical and biochemical transformations. The research deals with the issues of quantitative assessment of greenhouse gases and persistent organic pollutants formation within municipal solid waste landfills. It uses such methods as mathematical models of pollutants formation inside a municipal solid waste landfill body, namely methane and persistent organic pollutants formation. Bioorganic substance forming the major part of municipal solid waste generates methane, carbon dioxide and other compounds; presence of chlorine in various compounds included in the composition of waste causes unintentional formation of persistent organic pollutants, in particular PCDD/F. The article presents the results of measurements of methane formation (according to the National Gas Formation Model), carbon dioxide and non-methane volatile organic compounds formation (according to the LandGEM model) with relation to the conditions of the municipal solid waste landfill «Dalnytsky Kariery» that accepts waste from the Odesa industrial-and-urban agglomeration. It shows the municipal solid waste landfill as a significant source of greenhouse gases the amount of which increases rapidly under the conditions of long-term operation and constant delivery of waste. The discrepancy in the results of methane formation measurements indicates the need to adapt the LandGEM model that matches the Ukrainian conditions. It would allow determining a wide range of atmospheric polluting substances. The author's design determines the formation of persistent organic pollutants as exemplified by PCDD/F. The measurements showed that landfills act as a significant source of unintentional formation of PCDD/F, 99% of which accumulate inside a landfill itself. They also indicated that, under the conditions of a constant delivery of waste to a landfill, there is a rapid increase in the amount of PCDD/F formed, even with consideration of the half-life period. The landfill itself is considered as a main source of unintentional formation of PCDD/F within the whole Odesa agglomeration.

Concentrations, congener patterns, and correlations of unintentional persistent organic pollutants in cement kilns co-processing hazardous waste

Emissions from two typical cement kilns co-processing different kind of hazardous waste were analyzed for 143 congeners of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls, polychlorinated naphthalenes, polybrominated dibenzo-p-dioxins and dibenzofurans, and polybrominated diphenyl ethers. The congener distributions in different process stages were investigated. One of the plants co-processed waste chemical reagents from laboratories. The emission factor (TEQ basis) for the plant was 2.09 ng WHO2005 TEQ/t, with the kiln head and the kiln back end contributing 1.18, 0.91 ng WHO2005 TEQ/t, respectively. The other plant co-processed municipal waste incineration fly ash. The emission factor for the plant was 0.12 ng WHO2005 TEQ/t, with the kiln head and the kiln back end contributing 0.022, and 0.10 ng WHO2005 TEQ/t. These results indicate that co-processing of waste containing reagents from laboratories may lead to higher emission levels than co-processing of other types of waste. The congener patterns of persistent organic pollutants (POPs) in ash samples from the humidifier tower were similar to those in samples from the bag filter at the kiln back end. The correlation coefficients of five pollutants between the humidifier and bag filters samples were generally high, which indicated that conditions in those two stages similarly favored the formation of these POPs. Comparison of the concentrations for different process stages suggested that the main stage for formation of unintentional POPs was the humidifier tower. These results improve our understanding of emission characteristics and could be used for simultaneous control of multiple POPs.

Synergetic promoting/inhibiting mechanisms of copper/calcium compounds in the formation of persistent organic pollutants and environmentally persistent free radicals from anthracene

Copper compounds are considered the strongest promotors of unintentional persistent organic pollutants (POPs) formation, while calcium compounds are widely used to inhibit this process. Understanding the mechanisms underlying these processes is important for synergetic control of multiple POPs. Herein, the promoting ability of CuCl2 on the synergetic formation of POPs from anthracene and the underlying mechanisms were clarified. During thermochemical reaction with CuCl2, Cu2+ was first reduced to Cu+, and finally oxidized to CuO. Furthermore, CuCl2 promoted the formation of environmentally persistent free radicals (EPFRs) during thermochemical reaction. The formed EPFRs were identified as anthrone-type and anthraquinone-type radicals using electron paramagnetic resonance spectroscopy and gas chromatography/quadrupole time-of-flight mass spectrometry. Synergetic inhibition of POPs and EPFRs was achieved using CaO. The inhibiting mechanism of CaO was attributed to the absorption of chlorine originating from CuCl2 through the formation of CaClOH and the inhibition of free radical intermediates for POPs formation.

PHOTOCATALYTIC TREATMENT OF WATERS, POLLUTED WITH PHENOLS

The analysis of the environmental and human health threats imposed by phenols was conducted to show the need for further improvement of methods of their destruction. Being toxic in their initial composition and precursor to toxic metabolites in human body, phenols should be controlled in natural water and waste waters. They are listed as priority pollutants in most national regulation around the world and are the initial compounds for the formation of persistent organic pollutants in the environment, polluted with other active radicals. A variety of physical and chemical methods were offered for the destructive or non-destructive removal of phenols and their derivatives from water. The comparative study of possible methods, described in research papers, was conducted in terms of their efficiency and complexity to define benefits and drawbacks. The analysis showed the need for development of low energy consuming method, which needs minimal equipment and can be run under industrial condition for phenol contaminated wastewaters. Among the possible methods which meet the mentioned criteria photocatalytic destruction of phenols was showed to be perspective. A series of experiments was conducted using a range of water solution of phenol and different dosage of catalysts. The catalysts used in experiments were made of 6 modification of titanium oxide and bismuth ferrite. The initial and residual concentration of phenol was controlled by the means of high-performance liquid chromatography. The duration of the exposure and the type of light were other independent variables. The results of the whole sequence of experiments demonstrated higher efficiency of rutile under visible light and one hour of exposure. The tested photocatalytic system is simple and therefore technically and economically feasible.

Sewage Sludge as Inhibitor of the Formation of Persistent Organic Pollutants during Incineration

With the objective of suppressing dioxins and furans (PCDD/Fs) emission in municipal solid waste incineration plants (MSWI), different chemical inhibitors have been tested. Among these inhibitors, nitrogen and sulphur compounds can significantly suppress PCDD/Fs formation via de novo synthesis, which gives very interesting results with very little capital investment. In recent years, the possibility of using waste rich in nitrogen and/or sulphur as a source of inhibitor compounds has been considered, and thus has reduced the emissions of pollutants while the waste is treated. The effect of adding sludge from urban sewage treatment plants in three variants has been specially studied: directly mixing the waste, using the decomposition gas of the previously dried sludge, and using the decomposition gas of the sludge together with other inhibitors such as thiourea. Reduction of emissions in laboratory tests using model samples indicated the efficiency to be higher than 99%, using sewage sludge (SS) as an inhibitor whereas, in actual MSWI plants, the efficiency can be as high as 90%.

Formation mechanism of unintentionally produced persistent organic pollutants in industrial thermal processes

Persistent organic pollutants (POPs) can be unintentionally produced and emitted in industrial thermal processes. The investigation of their formation mechanism is the basis for the development of source reduction technologies. In this paper, we found some new breakthroughs in the theory of dioxin formation on the basis of literature. The research on the formation of free radical intermediates from precursors such as chlorophenols and chlorobenzenes in thermal processes can reveal the formation mechanism of dioxin at the molecular level, which enriches the theoretical system of POPs formation. It is also found that the type and content of carbon sources, chlorine sources and catalytic metals are the key factors influencing the generation and emission of typical unintentional POPs in industrial thermal processes such as incineration and metallurgy. This paper also highlights the key role of transition metal chlorides in the generation of POPs, which can serve as not only a catalyst for the reaction, but also an inorganic chlorine source to chlorinate organic compounds with macromolecular carbon structures, thus promoting the formation of POPs. This review can provide important theoretical basis for the source control of POPs.

Destruction behavior of short- and medium-chain chlorinated paraffins in solid waste at a pilot-scale incinerator

Incineration experiments with solid wastes containing approximately 3% (w/w) short-chain chlorinated paraffins (SCCPs) that have recently been listed as persistent organic pollutants (POPs) and medium-chain chlorinated paraffins (MCCPs) were conducted using a pilot-scale incinerator to investigate the efficiency of their destruction as well as the unintentional formation of POPs and their destruction behaviors during controlled incineration. A series of experiments demonstrated that SCCPs and MCCPs in solid wastes were progressively destroyed and removed during rotary kiln combustion and downstream flue gas treatments. Destruction efficiencies of SCCPs and MCCPs exceeding 99.9999% were confirmed. SCCPs in bottom and fly ash samples were present at levels below their quantification limits (0.021 and 0.31 mg/kg), and MCCPs in the bottom and fly ash samples were likewise present at concentrations below their quantification limits (0.034 and 0.50 mg/kg). Total concentrations of toxicity equivalency quantities (TEQs) for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (dl-PCBs) in emission gas samples collected at the bag filter exit and final exit were 0.083–0.30 and 8.7 × 10−7 to 1.3 × 10−4 ng-TEQ/m3N, respectively, and those in bottom and fly ash samples were 0.12–0.47 and 9.0 × 10−3 to 0.14 ng-TEQ/g, respectively. The results obtained in this study suggest that controlled incineration of solid wastes under the current regulations for incinerators in Japan and the countries with regulations and monitoring to minimize emissions of PCDDs/DFs and dl-PCBs is one of the best available technologies for the environmentally sound management of wastes containing SCCPs and MCCPs.

Thermolysis of Polymeric Composite Materials

The author has substantiated the use of the steam-thermolysis method for thermal utilization of waste polymeric composite materials to obtain valuable components in the form of recyclable fibers. On the basis of the performed investigations, it has been established that during the steam thermolysis of waste composite materials, the processes of formation of persistent organic pollutants are suppressed.

Thermochemical formation of multiple unintentional persistent organic pollutants on metallurgical fly ash and their correlations

Metallurgical processes are currently the predominant anthropogenic sources of multiple unintentional persistent organic pollutants (POPs), including polycyclic aromatic hydrocarbons (PAHs), chlorinated and brominated PAHs (Cl-PAHs and Br-PAHs), polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polybrominated diphenyl ether (PBDEs). Understanding the formation of multiple POPs is important for source control. These POPs could be formed through fly ash-mediated heterogeneous reactions. In this study, we comprehensively investigated the thermochemical (150–450 °C) formation of these POPs on fly ash samples collected from a secondary aluminum smelter, secondary lead smelter, and iron ore sintering plant. The maximum concentrations of PCNs and PCBs were 154.5 and 181.3 times those in the original fly ash, respectively. Formation variations of PAHs, Cl-PAHs and Br-PAHs, and PBDEs were different from that of PCBs and PCNs. The PAHs concentration, which was the highest among the POPs in the original fly ash, decreased sharply by 95% at 150 °C. The ∑19Cl-PAHs and ∑19Br-PAHs increased marginally at 250 °C before decreasing slightly at 350 °C. The PBDE concentrations decreased under 250 °C and increased at 350 °C. PCNs, PCBs, and PCDD/Fs showed good correlations, all of which had a negative relationship with the PAHs. There were no significant correlations between PAHs and Cl/Br-PAHs. Low brominated congeners could be formed by destruction of higher brominated congeners because of thermal instability of the PBDEs.

Main sources of unintentional production of persistent organic pollutants (the case of Odessa)

Persistent organic pollutants represent a serious global threat to human health and the environment. They have certain properties: resistance to decomposition, bioaccumulation, extreme toxicity, even at ultra-low concentrations, ability to transboundary transfer and deposition. Unfortunately, there is no separate normative and legislative base regulating production of persistent organic pollutants in Ukraine. All norms and rules regulating such pollutants formation are included in a large number of various legislative acts and this does not allow systematization and specification of the actions associated with treatment of POPs. The purpose of this work is to evaluate the main sources of unintentional formation of persistent organic pollutants (using Odessa as an example). As part of the study it was established that the main sources of unintentional formation of POPs in Odessa are: combustion of organic fuels by stationary and mobile sources; production of building materials; open landfills of solid household waste; smoking of meat and fish products; functioning of crematoria; tobacco smoking; functioning of the city sewage system. The analysis of the legislative base of Ukraine is carried out which resulted in making a conclusion that there is no separate normative and legislative base regulating production of persistent organic pollutants in Ukraine. For the first time the list of the main sources of unintentional formation of these pollutants was established for Odessa with estimation, using the most advanced European methods, of the mass of persistent organic pollutants formed from each type of above-stated production facilities, and estimation of the total mass of their generation over the territory of Odessa. Since different techniques give results in different units of measurement, a transition to one unit of measurement was performed. Based on the concept of maximum permissible concentration (MPC), the permissible number of molecules of POPs equivalent to 2,3,7,8- tetrachlorodibenzodioxin (TCDD) which can enter the body of one person through respiratory organs was calculated. A comparison with the number of molecules of 2,3,7,8-TCDD entering the atmosphere in a permissible quantity per 1 citizen of was carried out and corresponding conclusions based on calculations of unintentional formation of POPs in Odessa during one year were made. Also, based on the obtained results, priority sources of unintentional production of persistent organic pollutants were established which allows correct and timely implementation of appropriate measures to reduce formation of these polluting substances.

An Analysis of the Situation of Persistent Organic Pollutants in Ukraine (by the Example of Odessa)

Persistent organic pollutants (POPs) are chemicals of global concern due to their ability to bio-magnify and bio-accumulate in ecosystems, persistence in the environment, potential for long-range transport, as well as their significant negative effects on human health and the environment. Ukraine is a part of Stockholm Convention on Persistent Organic Pollutants witch control the environmental pollution by these substances on international level. That is why Ukraine must take measures to regulate production of persistent organic pollutants accordingly to requirements of the Convention. Purpose. The full analyses of the current state of the POPs problem in Ukraine, by the example of Odessa in the following areas: analysis of the legislative framework and monitoring system of POPs; estimation of the use of equipment containing PCBs; identification of sources of unintentional formation of POPs, calculation of POPs production volumes using the most modern European methods; identification of priority sources of POPs release into the environment; general conclusions on the situation with POPs in Ukraine. Results. Conclusions regarding the legislative framework and monitoring system of the POPs in Ukraine were made, for the first time the volumes of unintentional formation of POPs in Odessa were calculated, the main sources of unintentional formation of these substances were established and ranked, the full analyses and general conclusions on the situation with POPs in Ukraine were made. Conclusions. In Ukraine, there is no separate legislative framework and monitoring system for POPs, which does not meet the requirements of the Stockholm Convention. The basic sources of unintentional formation of POPs are established in the work, such as: burning of organic fuel, construction, waste dumps, sewerage, smoking cigarettes, crematoria and smokehouses. The main source of PCDD/F into the environment is the dump of solid household waste in landfills, and the main source of PCB and HCB is the incineration of organic fuels by stationary sources. The existing methods do not give an opportunity to fully assess the negative impact of POPs on the environment.

PCBs and PCDD/Fs in soil from informal e-waste recycling sites and open dumpsites in India: Levels, congener profiles and health risk assessment

Growth of informal electronic waste (e-waste) recycling sector is an emerging problem for India. The presence of halogenated compounds in e-wastes may result in the formation of persistent organic pollutants like polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) during recycling processes. We therefore investigated PCBs and PCDD/Fs in surface soils explicitly from the informal e-waste recycling sites and nearby open dumpsites of major metropolitan cities from four corners of India, viz., New Delhi (North), Kolkata (East), Mumbai (West) and Chennai (South). In the informal e-waste recycling sites, the range of Σ26PCBs (0.4–488ng/g) and ƩPCDD/Fs (1.0–10.6ng/g) were higher than Ʃ26PCBs (0.3–21ng/g) and ƩPCDD/Fs (0.15–7.3ng/g) from open dumpsites. In the e-waste sites, ƩPCDDs were found with increasing trend from ƩTetraCDD to OctaCDD, whereas ƩPCDFs showed a reverse trend. The dominance of PCDF congeners and maximum toxicity equivalents (TEQ) for both PCDDs (17pg TEQ/g) and PCDFs (82pg TEQ/g) at Mandoli in New Delhi has been related to intensive precious metal recovery process using acid bath. Among dumpsites, highest TEQ for PCDD/Fs was observed at Kodangaiyur dumpsite of Chennai (CNDS-02, 45pg TEQ/g). Positive Matrix Factorization (PMF) model identified distinct congener pattern based on the functional activities, such as e-waste dismantling, shredding, precious metal recovery and open burning in dumpsites. E-waste metal recovery factor was loaded with 86–91% of PCB-77, -105, -114, -118 and 30% of PCB-126, possibly associated with the burning of wires during the copper extraction process. Almost 70% of the Ʃ26PCB concentrations was comprised of the dioxin-like PCB congeners with a maximum concentration of 437ng/g at New Moore market in Chennai, followed by Wire Lane (102ng/g), in Mumbai. We speculate that PCB-126 might have resulted from combustion of plastic materials in e-waste stream and dumped waste.

Effects of Selective Catalytic Reduction on the Emissions of Persistent Organic Pollutants from a Heavy-Duty Diesel Engine

ABSTRACTThe emissions of persistent organic pollutants (POPs) from diesel engines is becoming more important due to their proximity to human beings compared to stationary sources whose emission have been well controlled over the years. The selective catalytic reduction (SCR) have been adopted in the heavy-duty diesel engine (HDDE) to reduce the nitrogen oxide (NOx). SCR has also been reported to reduce the polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polychlorinated biphenyls (PCBs). However, the memory effect and reformation of persistent organic pollutants (POPs) during SCR operation are not well understood. This study investigated the effect of Copper-zeolite SCR (CuZ SCR) on PCDD/F, PCB, polybrominated dibenzo-p-dioxin and dibenzofuran (PBDD/F), and polybrominated biphenyl (PBB) emissions from a HDDE at 50% and 75% engine load. Notably, PCDD/F and PCB toxicity emissions increased by 78.4% and 201%, respectively. The dominant PCDD/F congeners were OCDD, OCDF, 1,2,3,4,6,7,8-HpCDD, and 1,2,3,4,6,7,8-HpCDF and PCB-105, PCB-118 and PCB-77 for PCBs. More PCDFs were formed compared to PCDDs and lower chlorinated congeners increased more than the higher chlorinated ones. There was also an increase of PBDD/F concentrations from undetectable levels (ND) to 0.247 pg TEQ Nm–3 (4.00 pg TEQ L–1) after the SCR. However, only 1,2,3,4,6,7,8-HpBDF and OBDF contributed to the concentrations. PBBs was the only compound measured that reduced after the SCR. The only congener detected before and after the SCR was PBB 15. Consequently, the CuZ SCR could be a source of POPs under mid and high engine loads in this study. Further detail research is required to focus on the formation of POPs on the catalyst surfaces and structures.

Formation of persistent organic pollutants from 2,4,5-trichlorothiophenol combustion: a density functional theory investigation.

Polychlorinated dibenzothiophene (PCDT) and polychlorinated thianthrene (PCTA) are sulfur analogues of dioxins, such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F). In this work, we present a detailed mechanistic and kinetic analysis of PCDT and PCTA formation from the combustion of 2,4,5-trichlorothiophenol. It is shown that the formation of these persistent organic pollutants is more favourable, both kinetically and thermodynamically, than their analogous dioxin counterparts. This is rationalised in terms of the different influences of the S-H and O-H moieties in the 2,4,5-trichlorothiophenol and 2,4,5-trichlorophenol precursors. Kinetic parameters also indicate that the yield of PCDT should exceed that of PCDD. Finally, we demonstrate here that the degree and pattern of chlorination on the 2,4,5-trichlorothiophenol precursor leads to subtle thermodynamic and kinetic changes to the PCDT/PCTA formation mechanisms. Graphical abstract Formation mechanisms of persistant organic pollutants, PCDT and PCTA, from 2,4,5-trichlorothiophenol combustion, has been investigated using density functional theory.

Nanoparticular surface-bound PCBs, PCDDs, and PCDFs-a novel class of potentially higher toxic POPs.

In a previous study, Env Sci Poll Res:1-7, 2015 showed that polychlorinated biphenyls (PCBs), polychlorinated dibenzo dioxins (PCDDs), and polychlorinated dibenzo furanes (PCDFs) are found in commercially available (nano) particular titanium dioxide as a result of the fabrication. Here, we give a brief perspective and reason the toxicity of these new classes of persistent organic pollutants (POPs) by reviewing also their nanoparticular properties, such as surface-to-volume ratio, photocatalytic activity, polarity shifts, and stealth effect. These insights point towards a new class of POPs and toxicologic effects, which are related to the size but not a result of nanotechnology itself. We pave the way to the understanding of until now unresolved very complex phenomena, such as the indoor exposure, formation, and transformation of POP and sick-building syndrome. This is a fundamental message for nanotoxicology and kinetics and should be taken into account when determining the toxicity of nanomaterials and POPs separately and as a combination.

Insights into the emission reductions of multiple unintentional persistent organic pollutants from industrial activities

Industrial activities result in unintentional production of multiple types of persistent organic pollutants (POPs) at various concentrations. Because of the potential adverse effect of these POPs on the environment, biota and human health, methods for controlling emission of POPs are required. Development and application of techniques for controlling emissions of POPs can be a technical and economic burden for the industry involved. Therefore, from the point of view of cost-benefit analysis, reducing emissions of multiple pollutants at the same time is optimal for sustainable industrial development. Although techniques have been developed for reducing the emissions of individual POPs, such as dioxins, further work is required on multi-POP control emissions from industrial activities. This paper discusses three important aspects that need to be taken to achieve multi-POP control. These aspects include the establishment of a comprehensive system for evaluating the risk from emissions of multiple POPs, determination of indicators for total emissions of multiple POPs, and the preparation and application of functional materials to inhibit formation of multiple POPs. These discussion might be helpful for the future research on the multi-POP control in industry.