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171.
Formation of oxidation by-products of the iodinated X-ray contrast medium iomeprol during ozonation 总被引:1,自引:0,他引:1
The present work describes the investigation of the formation of oxidation by-products of the iodinated X-ray contrast medium (ICM) iomeprol during ozonation in water treatment. Bench-scale investigations revealed that ICM can be partly oxidized during ozonation processes, whereas the ionic diatrizoic acid showed the lowest reactivity. Iomeprol, as a representative of ICM, was not fully mineralized during ozonation. Thus, unknown oxidation by-products were formed. Aqueous solutions of iomeprol were treated by ozonation in order to assess the formation of oxidation by-products. The by-products were characterized by different liquid chromatography methods including detection of single-stage mass spectra, product ion mass spectra, and induced in-source fragmentation for analysis of iodine containing oxidation by-products. Aldehyde and carbonyl containing compounds were proposed to be among the stable by-products. A derivatization step confirms that the aldehyde and carbonyl moieties are major functional groups in oxidation by-products of iomeprol. Furthermore, oxidation by-products of iomeprol were detected at the outlet of an ozone reactor at a full-scale waterworks. However, the toxicological relevance of the by-products is a major future research tasks. 相似文献
172.
Determination of PCBs, PCDDs and PCDFs in insulating oil samples from stored Chinese electrical capacitors by HRGC/HRMS 总被引:2,自引:0,他引:2
Homologue and congener profiles of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in commercial PCBs formulations are key information for the source identification of PCBs contamination as well as for the risk assessment caused by potential exposure. The isotope dilution technology in combination with high resolution gas chromatography-high resolution mass spectrometry (HRGC/HRMS) has made the accurate determination of such profiles possible. So far, various commercial PCB formulations except Chinese products have been successfully determined. Two PCBs containing insulating oil samples from stored Chinese electrical capacitors have been determined with the same methodology for comparability. The total concentration PCBs in two oil samples were 790 000 μg g−1 and 720 000 μg g−1, respectively. TriCBs, TetraCBs, and DiCBs were found to be most abundant. Concentration of dioxins contamination in two samples is 650-670 ngTEQ g−1, of which 69-71 ngTEQ g−1 from PCDD/Fs with the predominant congeners of 1,2,7,8-TeCDF; 2,3,7,8-TeCDF; 2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDF. The contributions of DL-PCBs in total TEQ in both samples were more than 85%. The dioxin-like toxicity in insulating oils contained in electrical capacitors could be considered receive attention as an important dioxins source if such wastes are not managed in an environmentally sound manner. 相似文献
173.
In the present work we describe the photocatalytic degradation of methylbutandioic acid (MBA), focusing particularly on adsorption of the MBA on TiO2 surface. We observe a very fast surface carboxylate formation, a decrease of the surface carboxylates during the reaction and an apparent zero order kinetic for the degradation of MBA. We conclude that the main way of MBA degradation is its reaction in the solution, and not on the surface of TiO2. The influence of the surface carboxylates on the efficiency of the catalyser is under study. 相似文献
174.
Roland Weber Stefan Gonser Jutta Köhler Wolfgang Körner Christine Herold Roland Haag Margit Krapp Ludwig Peichl 《Environmental science and pollution research international》2018,25(17):16344-16354
In the 1980s, it was demonstrated that semi-volatile organic compounds (SVOCs) like polychlorinated biphenyls (PCBs) accumulate in plant leaves. Plants are at the base of the food chain, and therefore a starting point for transfer of PCBs to animals and related human exposure. For two decades, the Environment Agency of the German federal state of Bavaria (LfU) has been operating long-term monitoring stations to measure the impact of organic air pollutants. Standardized ryegrass, curly kale, and spruce needles are used as bioindicators for the atmospheric entries of PCBs into vegetation. From the end of 1990s to 2009, there was a marked decline in the concentrations of indicator PCBs (i-PCBs) and a minor decline in PCB-TEQ levels. After 2009, the concentrations leveled off. In rural areas, the median concentrations of Σ6 i-PCB in ryegrass and curly kale were about 3 and 4 μg/kg dm in 2000, and have been about 0.5 and 1 μg/kg dm since 2009, respectively. Concentrations in spruce needles fell from 0.9 to 0.4 μg/kg dm. Median PCB-TEQ concentrations in the bioindicator plants ranged from 0.05 to 0.23 ng/kg dm between 2002 and 2009 and from 0.15 to 0.05 ng/kg dm after 2009. Indicator PCB and PCB-TEQ concentrations were several times higher at the urban station in Munich than at the rural areas, reflecting the emissions from in-use PCB stocks in the building sector. The likely reason of the slower decrease of PCB-TEQ compared to i-PCBs is the formation of PCB-126 by dechlorination of industrial PCBs in open applications. 相似文献
175.
In this paper the thermal behaviour of Miscanthus × Giganteus (M×G) is studied by thermogravimetric analysis. In order to
characterise the thermal behaviour of its cellulose, hemicellulose and lignin, the raw M×G material was treated sequentially
by water, H2SO4 and KOH. The global kinetic parameters for each component were determined by subsequent modelling of the TG data with the
Ozawa-Flynn-Wall method and multivariate non-linear regression. It is found that the global pyrolysis of M×G can be satisfactorily
described using a six steps-kinetic scheme. The analytical method proposed here can be probably extended without too many
efforts to other biomass products.
An erratum to this article can be found at 相似文献
176.
Contributing to the debate on the causes of Himalayan environmental degradation, the status and management of four watersheds
in the Upper Pokhara Valley were studied using information available from land use analysis, household surveys conducted in
1989 and 1992, deliberations held with villagers, and field observations. Accordingly, areas under forests and grazing lands
were found being depleted at relatively high rates between 1957 and 1978 due mainly to the government policy of increasing
national revenue by expansion of agricultural lands, nationalization of forests, steadily growing population, and dwindling
household economy. Despite the steady growth of population, this process had remarkably slackened since 1978, owing primarily
to remaining forests being located in very, steep slopes and implementation of the community forestry program. Forests with
relatively sparase tree density, however, and grazing lands in the vicinity of settlements have been undergoing degradation
due to fuelwood and fodder collection and livestock grazing. In many instances, this is aggravated by weak resource management
institutions. Being particularly aware of the economic implication of land degradation, farmers have adopted assorted land
management practices. Still a substantial proportion ofbari lands in the hill slopes is vulnerable to accelerating degradation, as the arable cropping system is being practiced there
as well. The perpetuation of the local subsistence economy is certain to lead, to a further deterioration of the socioeconomic
and environmental conditions of watersheds. To facilitate environmental conservation and ecorestructuring for sustainable
development, a broad watershed management strategy is outlined with focus on alleviating pressure on natural resources. 相似文献
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