Emissions of polychlorinated diphenyl ethers from a municipal solid waste incinerator during the start-up operation

Polychlorinated Diphenyl Ethers in the Environment: A Review and Future Perspectives

Polychlorinated diphenyl ethers (PCDEs) are a class of synthetic halogenated aromatic compounds, which have gradually attracted widespread attention due to potential environmental risks to humans and ecosystems. This paper presents a literature review of research on PCDEs using PubMed, Web of Science and Google Scholar as search engines/databases with no constraints on publishing year or number. A total of 98 publications on the sources, environmental levels, environmental behavior and fate, synthesis and analysis and toxicology of PCDEs were retrieved. Existing studies have shown that PCDEs widely exist in the environment with the ability of long-range transport, bioaccumulation and biomagnification, which are almost comparable to polychlorinated biphenyls. They can elicit adverse effects including hepatic oxidative stress, immunosuppression, endocrine disorders, growth retardation, malformations, reduced fertility and increased mortality in organisms, among which some seem to be related to the activation of the aryl hydrocarbon receptor. PCDEs can be metabolized into other organic pollutants, such as hydroxylated and methoxylated PCDEs and even polychlorinated dibenzo-p-dioxins and furans through biotransformation, photolysis and pyrolysis reactions in the environment. Compared with reviews on PCDEs published previously, some new information and findings are summarized in this review, such as new sources, current environmental exposure levels, main metabolism pathways in aquatic organisms, acute toxicity data for more species and relationships between structural parameters and toxicity and bioaccumulation potentials of PCDE congeners. Finally, current research deficiencies and future research perspectives are proposed to facilitate the assessment of health and ecological risks of PCDEs.

Feasible and effective control strategies on extreme emissions of chlorinated persistent organic pollutants during the start-up processes of municipal solid waste incinerators

A typical two-day start-up of municipal solid waste incinerators (MSWIs) can yield polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) and polychlorinated biphenyl (PCB) emission quantities around 10 times higher than those from an entire year of normal operations, as measured in this study. Thus, we tested specific control strategies for inhibiting the formation of chlorinated persistent organic pollutants (Cl-POPs), namely, extensively cleaning the ash accumulated beneath the furnace bed of the combustion chamber and deposited on the walls of the superheater and economizer and shortening the residence time of the flue gas in the optimal temperature window for Cl-POP formation. Also, we advanced the injection times of the activated carbon and lime slurry to lower Cl-POP emissions during start-up. Our findings show that these strategies were highly effective and reduced the Cl-POP emissions by > 98%, most of which (96.4-98.2%) was attributable to inhibiting formation. In summary, the proposed control strategies require no modifications to existing air pollution control devices, have little influence on operational cost, and are effective and feasible for the majority of MSWIs.

Complex Mixtures of Brominated/Chlorinated Diphenyl Ethers and Dibenzofurans in Soils from the Agbogbloshie e-Waste Site (Ghana): Occurrence, Formation, and Exposure Implications

The distribution and toxic equivalents (TEQs) of brominated and chlorinated dibenzo- p-dioxins/dibenzofurans (PBDD/Fs and PCDD/Fs) in soils from Agbogbloshie e-waste site (Ghana) were investigated. The composition of brominated/chlorinated dibenzofurans (PXDFs) and diphenyl ethers (PBDEs, PCDEs, and PXDEs) was examined using two-dimensional gas chromatography-time-of-flight mass spectrometry to elucidate possible formation pathways of dioxins from e-waste recycling. The highest concentrations of PCDD/Fs and PBDD/Fs were found, respectively, in the open burning (1.3-380 ng/g dry weight) and dismantling areas (11-1000 ng/g dry weight) and were comparable to the highest reported for informal e-waste sites. PXDFs and PXDEs were detected at up to the range of hundreds of nanograms per gram. The homologue profiles suggest that PXDFs were formed mainly from PBDFs through successive Br-to-Cl exchange. However, monobromo-PCDFs were also derived from de-novo-generated PCDFs in open burning areas. PBDFs contributed similar or higher TEQs (7.9-5400 pg/g dry weight) compared with PCDD/Fs (6.8-5200 pg/g dry weight), whereas PXDFs were also substantial TEQ contributors in open burning areas. The high TEQs of PBDFs in the dismantling area (120-5200 pg/g dry weight) indicate the need to consider brominated dioxins besides chlorinated dioxins in future studies on health implications for e-waste workers and local residents.

HaloSeeker 1.0: A User-Friendly Software to Highlight Halogenated Chemicals in Nontargeted High-Resolution Mass Spectrometry Data Sets

In the present work, we address the issue of nontargeted screening of organohalogenated chemicals in complex matrixes. A global strategy aiming to seek halogenated signatures in full-scan high-resolution mass spectrometry (HRMS) fingerprints was developed. The resulting all-in-one user-friendly application, HaloSeeker 1.0, was developed to promote the accessibility of associated in-house bioinformatics tools to a large audience. The ergonomic web user interface avoids any interactions with the coding component while allowing interactions with the data, including peak detection (features), deconvolution, and comprehensive accompanying manual review for chemical formula assignment. HaloSeeker 1.0 was successfully applied to a marine sediment HRMS data set acquired on a liquid chromatography-heated electrospray ionization [LC-HESI(-)] Orbitrap instrument ( R = 140 000 at m/z 200). Among the 4532 detected features, 827 were paired and filtered in 165 polyhalogenated clusters. HaloSeeker was also compared to three similar tools and showed the best performances. HaloSeeker's ability to filter and investigate halogenated signals was demonstrated and illustrated by a potential homologue series with C₁₂H _xBr _yCl _zO₂ as a putative general formula.

Emission characteristics of toxic pollutants from an updraft fixed bed gasifier for disposing rural domestic solid waste

Gasification has gained advantage as an effective way to dispose domestic solid waste in mountainous rural of China. However, its toxic emissions such as PCDD/Fs and heavy metals, as well as their potential environmental risks, were not well studied in engineering application. In this study, an updraft fixed bed gasifier was investigated by field sampling analysis. Results showed that low toxic emissions (dust, SO₂, NOx, HCl, CO, H₂S, NH₃, PCDD/Fs and heavy metals) in the flue gas were achieved when the rural solid waste was used as feedstock. The mass distribution of heavy metals showed that 94.00% of Pb, 80.45% of Cu, 78.00% of Cd, 77.31% of Cr, and 76.25% of As were remained in residual, whereas 86.58% of Hg was found in flue gas. The content of PCDD/Fs in the flue gas was 0.103 ngI-TEQ·Nm^-3, and the total emission factor of PCDD/Fs from the gasifier was 50.04 μgI-TEQ·t-waste^-1, among which only 0.04 μgI-TEQ·t-waste^-1 was found in the flue gas. The total output of PCDD/Fs was1.89 times as high as input, indicting the updraft fixed bed gasifier increased emission of PCDD/Fs during the treatment domestic solid waste. In addition, the distribution characteristics of PCDD/Fs congeners reflected that PCDD/Fs was mainly generated in the gasification process rather than the stage of flue gas cleaning, suggesting the importance to effectively control the generation of PCDD/Fs within the gasifier chamber in order to obtain a low PCDD/Fs emission level.