| 1. |
- Meng, Pingping, et al.
(författare)
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Efficient removal of perfluorooctane sulfonate from aqueous film-forming foam solution by aeration-foam collection
- 2018
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 203, s. 263-270
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Tidskriftsartikel (refereegranskat)abstract
- Aqueous film-forming foams (AFFFs) used in fire-fighting are one of the main contamination sources of perfluorooctane sulfonate (PFOS) to the subterranean environment, requiring high costs for remediation. In this study, a method that combined aeration and foam collection was presented to remove PFOS from a commercially available AFFF solution. The method utilized the strong surfactant properties of PFOS that cause it to be highly enriched at air-water interfaces. With an aeration flow rate of 75 mL/min, PFOS removal percent reached 96% after 2 h, and the PFOS concentration in the collected foam was up to 6.5 mmol/L, beneficial for PFOS recovery and reuse. Increasing the aeration flow rate, ionic strength and concentration of co-existing surfactant, as well as decreasing the initial PFOS concentration, increased the removal percents of PFOS by increasing the foam volume, but reduced the enrichment of PFOS in the foams. With the assistance of a co-existing hydrocarbon surfactant, PFOS removal percent was above 99.9% after aeration-foam collection for 2 h and the enrichment factor exceeded 8400. Aeration-foam collection was less effective for short-chain perfluoroalkyl substances due to their relatively lower surface activity. Aeration-foam collection was found to be effective for the removal of high concentrations of PFOS from AFFF-contaminated wastewater, and the concentrated PFOS in the collected foam can be reused.
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| 2. |
- Meng, Pingping, et al.
(författare)
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Role of the air-water interface in removing perfluoroalkyl acids from drinking water by activated carbon treatment
- 2020
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 386
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Tidskriftsartikel (refereegranskat)abstract
- Contamination of drinking water by per- and polyfluoroalkyl substances (PFASs) is a worldwide problem. In this study, we for the first time revealed the role of the air-water interface in enhancing the removal of long-chain perfluoroalkyl carboxylic (PFCAs; CnF2n+1COOH, n >= 7) and perfluoroalkane sulfonic (PFSAs; CnF2n+1SO3H, n >= 6) acids, collectively termed as perfluoroalkyl acids (PFAAs), through combined aeration and adsorption on two kinds of activated carbon (AC). Aeration was shown to enhance the removal of long-chain PFAAs through adsorption at the air-water interface and subsequent adsorption of PFAA-enriched air bubbles to the AC. The removal of selected long-chain PFAAs was increased by 50-115 % with the assistance of aeration, depending on the perfluoroalkyl chain length. Aeration is more effective in enhancing long-chain PFAA removal as air-water interface adsorption increases with PFAA chain length due to higher surface activity. After removing adsorbed air bubbles by centrifugation, up to 80 % of the long-chain PFAAs were able to desorb from the sorbent, confirming the contribution of the air-water interface to the adsorption of PFAAs on AC. Aeration during AC treatment of water could enhance the removal of long-chain PFAAs, and improve the performance of AC during water treatment.
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| 3. |
- Wang, Bin, et al.
(författare)
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A primary estimate of global PCDD/F release based on the quantity and quality of national economic and social activities
- 2016
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Ingår i: Chemosphere. - Oxford, United Kingdom : Elsevier. - 0045-6535 .- 1879-1298. ; 151, s. 303-309
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Tidskriftsartikel (refereegranskat)abstract
- The correlations between polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) releases and factors relevant to human social-economic activities (HSEAs) were analyzed. The multiple linear regression model was successfully developed to estimate the total global PCDD/F release. The PCDD/F releases significantly correlated with population, area, GDP and GNI, suggesting that "quantity" of HSEAs have significantly contributed to the PCDD/F releases. On another aspect, advanced technologies are usually adopted in developed countries/regions, and hence reduce the PCDD/F release. The significant correlation between PCDD/F release and CO2 emission implies the potential of simultaneous reduction of CO2 emission and PCDD/F release. The total global PCDD/F release from 196 countries/regions was estimated to be 100.4 kg-TEQ yr(-1). The estimated annual PCDD/F release per unit area ranged from 0.007 to 28 mg-TEQ km(-2). Asia is estimated to have the highest PCDD/F release of 47.1 kg-TEQ yr(-1), almost half of the total world release. Oceania is estimated to have the smallest total release but the largest per-capita release. For the developed areas, such as Europe and North America, the PCDD/F release per unit GDP is lower, while for Africa, it is much higher.
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| 4. |
- Cao, Zhiguo, et al.
(författare)
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Economic status as a determinant of national PCDD/PCDF releases and implications for PCDD/PCDF reduction
- 2013
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 91:3, s. 328-335
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Tidskriftsartikel (refereegranskat)abstract
- The annual releases of polychlorinated dibenzo-para-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) from 68 countries/regions were investigated by correlating quantitative emissions with economic status of the nations. The national dioxin/furan inventories were developed using the PCDD/PCDF Standardized Toolldt, which presents the quantitative releases from ten major source groups to five release vectors. The correlation between intensity of PCDDIPCDF release and economic status was discussed and the influence of economic status on composition of five release vectors and ten source groups was studied. As PCDD/PCDF are mainly released from human activities to environmental matrices, release per person (RpP) and release per unit area (RpA) are defined to reflect release burden (Donor) and contamination burden (Receptor), respectively. Based on these two concepts, International PCDD/PCDF Reduction Burden is characterized by burden quotient (BQ) and a calculation model is established. The numbers of countries/regions with high, moderate and low International PCDD/PCDF Reduction Burden were 19,31 and 18, respectively. The information in this paper can be used for politicians to develop legislations to improve International PCDD/PCDF Reduction.
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| 5. |
- Cao, Zhi-Guo, et al.
(författare)
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Particle size : A missing factor in risk assessment of human exposure to toxic chemicals in settled indoor dust
- 2012
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Ingår i: Environment International. - : Elsevier. - 0160-4120 .- 1873-6750. ; 49, s. 24-30
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Tidskriftsartikel (refereegranskat)abstract
- For researches on toxic chemicals in settled indoor dust, selection of dust fraction is a critical influencing factor to the accuracy of human exposure risk assessment results. However, analysis of the selection of dust fraction in recent studies revealed that there is no consensus. This study classified and presented researches on distribution of toxic chemicals according to dust particle size and on relationship between dust particle size and human exposure possibility. According to the literature, beyond the fact that there were no consistent conclusions on particle size distribution of adherent fraction, dust with particle size less than 100 mu m should be paid more attention and that larger than 250 mu m is neither adherent nor proper for human exposure risk assessment. Calculation results based on literature data show that with different selections of dust fractions, analytical results of toxic chemicals would vary up to 10-fold, which means that selecting dust fractions arbitrarily will lead to large errors in risk assessment of human exposure to toxic chemicals in settled dust. Taking into account the influence of dust particle size on risk assessment of human exposure to toxic chemicals, a new methodology for risk assessment of human exposure to toxic chemicals in settled indoor dust is proposed and human exposure parameter systems to settled indoor dust are advised to be established at national and regional scales all over the world.
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| 6. |
- Gong, Wenwen, et al.
(författare)
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Emission factors of unintentional HCB and PeCBz and their correlation with PCDD/PCDF
- 2017
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Ingår i: Environmental Pollution. - : Elsevier. - 0269-7491 .- 1873-6424. ; 230, s. 516-522
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Tidskriftsartikel (refereegranskat)abstract
- Hexachlorobenzene (HCB) and pentachlorobenzene (PeCBz) have been listed as unintentional POPs in the annex of the Stockholm Convention and thus, attracted attention by government and researchers. Since the intentional production and use has ceased in most countries, the unintentional releases to the environment have increased. This study gathered 206 and 78 emission factors (EFs) of unintentional HCB and PeCBz from scientific publications and governmental reports, respectively. Most of the EFs referred to the release vector "air" (EFAir) and to a less extent to "product" (EFProduct). EFs were proposed for different source categories/classes used in the Toolkit according to the technologies that released the HCB or PeCBz. Overall, lowest and highest EFAir for HCB were found in the metallurgical industry range from 1 μg/t in well controlled plants (coke, iron and steel) up to 40,000 μg/t (secondary zinc). EFs for PeCBz were in similar order of magnitude. Due to lack of data, EFs to water, land or residue cannot be proposed. Using linear regression and statistical analysis such as Pearson correlation, we found strongest correlation of EFAir between HCB and PeCBz (R(2) = 0.79, P < 0.01) and weaker, but still significant, correlations for EFAir between PCDD/PCDFTEQ and HCB (R(2) = 0.56; P < 0.01) or PeCBz (R(2) = 0.31 P < 0.01) for various thermal processes.
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| 7. |
- Gong, Wenwen, et al.
(författare)
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Reassessment and update of emission factors for unintentional dioxin-like polychlorinated biphenyls
- 2017
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 605, s. 498-506
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Tidskriftsartikel (refereegranskat)abstract
- One of the major goals of the Stockholm Convention on Persistent Organic Pollutants is to continuously reduce the releases of unintentional persistent organic pollutants (POPs) such as polychlorinated dibenzo-paradioxins and dibenzofurans (PCDD/PCDF) or polychlorinated biphenyls (PCB) from anthropogenic sources. Until now, most efforts have focused on the releases of PCDD/PCDF and to a lesser extent on unintentionally generated PCB, and therefore, release inventories reported as toxic equivalents (TEQ) do not include the twelve dioxin-like PCB (dl-PCB). In order to facilitate the development of national release inventories for the total TEQ - consisting of PCDD, PCDF and PCB - this study collected and summarized published emission factors (EFs) of unintentional dl-PCB or calculated them from measured data for the sources listed in the UNEP Toolkit. In total, 286 EFs for dl-PCB were found (or could be calculated) whereby 233 described release to air, 23 EFs addressed to residue, 25 EFs to product; and only 5 EFs addressed releases to land. Taking into account performance criteria such as the facility type and scale or abatement technologies, the EFs were grouped and assigned to the source categories and/or classes used in the UNEP Toolkit. With these newly added data and EFs of dl-PCB, the already existing EFs in the Toolkit can be improved and amended. In addition, a statistically significant correlation between the EFAir of dl-PCB proposed in this study and EFAir of PCDD/PCDF recommended in the Toolkit was observed.
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| 8. |
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| 9. |
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| 10. |
- Liu, Xiaotu, et al.
(författare)
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Potential sources of unintentionally produced PCB, HCB, and PeCBz in China : A preliminary overview
- 2018
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Ingår i: Frontiers of Environmental Science and Engineering. - : Higher Education Press. - 2095-2201 .- 2095-221X. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- Under the Stockholm Convention on Persistent Organic Pollutants (POPs), China is required not only to reduce polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) but also unintentionally produced polychlorinated biphenyls (PCB), hexachlorobenzene (HCB) and pentachlorobenzene (PeCBz). A baseline of the sources in China that generate these unintentional POPs is needed for both research and regulation purposes. In this paper, we have compiled production data of potential sources in China and assessed them in five-year intervals from 2000 to 2015. Most of these activities experienced changes from rapid growth to slow growth. Measured data for PCB, HCB and PeCBz in samples collected from potential sources in China were reviewed. Most information was associated to thermal processes with high potential of emission, including waste incineration and ferrous and non-ferrous metal production. In addition, high levels of PCB, HCB and PeCBz were found as impurities in a few chlorinated products or as by-products in solvent production, which suggested organochlorine industry might be important sources. Finally, based on the studies reviewed, recommendations for future actions in research and policy as well as a few regulatory issues in China are discussed.
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