| 1. |
- Meng, Mei, et al.
(författare)
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Accumulation of total mercury and methylmercury in rice plants collected from different mining areas in China
- 2014
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Ingår i: Environmental Pollution. - : Pergamon Press. - 0269-7491 .- 1873-6424. ; 184, s. 179-186
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Tidskriftsartikel (refereegranskat)abstract
- A total of 155 rice plants were collected from ten mining areas in three provinces of China (Hunan, Guizhou and Guangdong), where most of mercury (Hg) mining takes place in China. During the harvest season, whole rice plants were sampled and divided into root, stalk & leaf, husk and seed (brown rice), together with soil from root zone. Although the degree of Hg contamination varied significantly among different mining areas, rice seed showed the highest ability for methylmercury (MeHg) accumulation. Both concentrations of total mercury (THg) and MeHg in rice plants were significantly correlated with Hg levels in soil, indicating soil is still an important source for both inorganic mercury (IHg) and MeHg in rice plants. The obvious discrepancy between the distribution patterns of THg and MeHg reflected different pathways of IHg and MeHg accumulation. Water soluble Hg may play more important role in MeHg accumulation in rice plants.
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| 2. |
- 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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| 3. |
- Yu, Jun-Chao, et al.
(författare)
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Levels and distribution of short chain chlorinated paraffins in seafood from Dalian, China
- 2014
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Ingår i: Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.]. - Beijing : Ke xue zhu ban she. - 0250-3301. ; 35:5, s. 1955-1961
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Tidskriftsartikel (refereegranskat)abstract
- Seafood samples were collected from Dalian, China to study the accumulation and distribution characteristics of short chain chlorinated paraffins (SCCPs) by GC/ECNI-LRMS. Sum of SCCPs (dry weight) were in the range of 77-8 250 ng.g-1, with the lowest value in Scapharca subcrenata and highest concentration in Neptunea cumingi. The concentrations of sum of SCCPs (dry weight) in fish, shrimp/crab and shellfish were in the ranges of 100-3 510, 394-5 440, and 77-8 250 ng.g-1 , respectively. Overall, the C10 and C11 homologues were the most predominant carbon groups of SCCPs in seafood from this area,and a relatively higher proportion of C12-13 was observed in seafood with higher concentrations of sum of SCCPs . With regard to chlorine content, Cl1,, CI8 and CI6 were the major groups. Significant correlations were found among concentrations of different SCCP homologues (except C1, vs. Cl10 ) , which indicated that they might share the same sources and/or have similar accumulation, migration and transformation processes.
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| 4. |
- Yun, Zhaojun, et al.
(författare)
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Evaluation of different extraction procedures for determination of organic Mercury species in petroleum by high performance liquid chromatography coupled with cold vapor atomic fluorescence spectrometry
- 2013
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 106, s. 60-65
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Tidskriftsartikel (refereegranskat)abstract
- An extraction procedure for extracting organic mercury species including methylmercury (MeHg) and ethylmercury (EtHg) from petroleum samples was developed. Three extraction methods (shaking, ultrasonic and microwave assisted extraction) using different extraction solvents (TMAH, KOH/CH3OH, HCl and acidic CuSO4/KBr) were investigated by comparing the extraction efficiency of the organic mercury species. Microwave assisted extraction at 60 W for 5 min using TMAH (tetramethylammonium hydroxide, 25%, m/v) provided the most satisfactory extraction efficiency for MeHg and EtHg in petroleum at 86.7% ± 3.4% and 70.6% ± 5.9%, respectively. Speciation analysis of mercury was done by on-line coupling of high performance liquid chromatography with cold vapor generation atomic fluorescence spectrometry (HPLC-CV-AFS). The proposed method was successfully applied to analyze several crude oil and light oil samples. The concentrations of MeHg ranged from under detection limit to 0.515 ng g(-1), whereas EtHg was not detected in the samples. This method can be a very useful tool in evaluating the risk of mercury emissions from petroleum.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- Chen, Baowei, et al.
(författare)
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Methylation of inorganic mercury by methylcobalamin in aquatic systems
- 2007
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Ingår i: Applied organometallic chemistry. - : John Wiley & Sons. - 0268-2605 .- 1099-0739. ; 21:6, s. 462-467
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Tidskriftsartikel (refereegranskat)abstract
- The methylation of inorganic Hg(II) by methylcobalamin in aquatic systems was studied using high-performance liquid chromatography coupled with UV-digestion cold vapor atomic fluorescence spectrometry (HPLC-UV-CV AFS). Monomethylmercury (MMC) could be positively identified as the reaction product in the aqueous solution. The salinity and pH of the aquatic system have great effects on the formation of MMC, because they could change the species of the reactants in the solution. From an electrophile reaction point of view, salinity and pH alter the electron density of the methyl donor and the electrophilicity of metal ion in the reaction system. This methylation of inorganic Hg(II) is shown to be possible even in highly saline solutions, which indicates its importance in aquatic environments. Kinetic experiments showed that the methylation reaction was fast and first-order for Hg(II). The first-order reaction rate was determined to be 0.00612 and 0.000287 min-1 for pH 5.0 and 1.5, respectively. It is suggested that this methylation could occur in the absence of enzymes, in which Hg(II) acts as an electrophile to attack methylcobalamin with a subsequent transfer of carbanion methyl group to the higher oxidized state of Hg(II).
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| 8. |
- Chen, Baowei, et al.
(författare)
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Simulate methylation reaction of arsenic(III) with methyl iodide in an aquatic system
- 2006
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Ingår i: Applied organometallic chemistry. - : John Wiley & Sons. - 0268-2605 .- 1099-0739. ; 20:11, s. 747-753
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Tidskriftsartikel (refereegranskat)abstract
- The methylation reaction of inorganic arsenic occurring in aquatic systems was studied by HPLC-HGAFS as a method to separate and detect soluble methylarsenic species. Transformation from inorganic arsenic to methylarsenic was essential for major changes in toxicity to organisms. Monomethylarsenic [AsOCH(3)(OH)(2)] was the only product in the methylation reaction of inorganic arsenic(III) with methyl iodide (MeI). This process can be described as an oxidative carbonium-ion transfer, with MeI acting as a methyl donor. From a thermodynamic point of view, the activity of the carbonium ion and pH were the two major influencing factors. The pH dependence of redox potential of As(III) was the reason for the effect of pH on methylation of arsenic. The influences of salinity and concentration of the methyl donor may be explained by their effects on the activity of carbonium. Moreover, kinetics experiments demonstrated that the methylation reaction was first-order for both As(III) and methyl iodide. First-order reaction rates were also calculated at different pH, salinity and MeI, and were found to be in the range 0.0026-0.0123 h(-1). The methylation rate varied largely under different reaction conditions.
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| 9. |
- 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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| 10. |
- 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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