Reaction processes effecting the analysis of chloroform by direct aqueous injection gas chromatography

Several important reaction processes which influence the analysis of chloroform by direct aqueous injection (DAI) gas chromatography have been identified through an investigation of the chlorination reactions of humic acid and a series of simple polyhydroxyaromatic and diketone model compounds in dilute solution. The reaction of chlorine with each substrate system was studied over the pH range 2–12. Gas chromatographic analysis by the DAI and organic solvent liquid-liquid extraction (LLE) procedures gave different measurements for the yield of CHCl₃ depending on the pH of the reaction solution and the chemical structure of the substrate. Under acidic and neutral conditions, a variety of trichloromethyl-substituted intermediates were identified at high concentrations in addition to chloroform by GC/MS. Chloral hydrate, trichloroacetic acid, pentachloroacetone and hexachloroacetone undergo hydrolysis and/or decarboxylation to form CHCl₃ at the high injection port temperatures employed in aqueous injection GC analysis. The results obtained in the current study indicate that the decomposition of these and structurally-related species accounts for differences previously observed upon application of the DAI and either the LLE or purge-and-trap techniques for the determination of CHCl₃ in chlorinated natural waters.     

Radon and 'King Solomon's Miners': Faynan Orefield, Jordanian Desert

Concentrations of 222Rn were measured in ancient copper mines which exploited the Faynan Orefield in the South-Western Jordanian Desert. The concentrations of radon gas detected indicate that the ancient metal workers would have been exposed to a significant health risk and indicate that any future attempt to exploit the copper ores must deal with the hazard identified. Seasonal variations in radon concentrations are noted and these are linked to the ventilation of the mines. These modern data are used to explore the differential exposure to radon and the health of ancient mining communities.     

The impact of preoxidation of SAS on biosorption efficiency on activated carbon

We have studied the process of a prolonged dynamic filtration on activated carbon in two biosorption systems — without preoxidation treatment of the initial matter and after ozonization. It has been shown that given the uniform load on activated carbon terms of the organic matter the efficiency of the biosorption process after preozonization is 2.3 times as small compared with that that without pretreatment, which correlates with the change of adsorption free energy.     

Engineering geology today

Summary The author discusses the development and present state of the engineering geology. He warns the engineering geologists against a merely mechanical approach and emphasizes that an engineer needs to understand geology as well. Further an analysis of the relation between geology and civil engineering and between engineering geology and soil and rock mechanics is presented. Finally the paper deals with the tasks of engineering geology at designing and construction of structures as well as with the problems of education in engineering geology.

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La Géologie De l’Ingénieur Aujourd’Hui

Résumé L’auteur examine la question du développement et de la situation acutelle de la géologie de l’ingénieur. II préviend d’un accès simplement méchanical en accentuant, qu’il est vraiement nécéssaire pour un ingénieur de comprendre aussi la géologie. Puis, l’auteur analyse la rélation entre la géologie et la construction ainsi qu’entre la géologie de l’ingénieur et la mécanique du sol. Enfin, le travail traits les taches de la géologie de l’ingénieur dans la sphère des projets et de la réalisation des constructions ainsi que les problèmes de l’éducation.

     

Influences of iron, manganese, and dissolved organic carbon on the hypolimnetic cycling of amended mercury

The biogeochemical cycling of iron, manganese, sulfide, and dissolved organic carbon were investigated to provide information on the transport and removal processes that control the bioavailability of isotopic mercury amended to a lake. Lake profiles showed a similar trend of hypolimnetic enrichment of Fe, Mn, DOC, sulfide, and the lake spike ((202)Hg, purity 90.8%) and ambient of pools of total mercury (HgT) and methylmercury (MeHg). Hypolimnetic enrichment of Fe and Mn indicated that reductive mobilization occurred primarily at the sediment-water interface and that Fe and Mn oxides were abundant within the sediments prior to the onset of anoxia. A strong relationship (r(2)=0.986, n=15, p<0.001) between filterable Fe and Mn indicated that reduction of Fe and Mn hydrous oxides in the sediments is a common in-lake source of Fe(II) and Mn(II) to the hypolimnion and that a consistent Mn:Fe mass ratio of 0.05 exists in the lake. A strong linear relationship of both the filterable [Fe] (r(2)=0.966, n=15, p<0.001) and [Mn] (r(2)=0.964, n=15, p<0.001) to [DOC] indicated a close linkage of the cycles of Fe and Mn to DOC. Persistence of iron oxides in anoxic environments suggested that DOC was being co-precipitated with Fe oxide and released into solution by the reductive dissolution of the oxide. The relationship between ambient and lake spike HgT (r(2)=0.920, n=27, p<0.001) and MeHg (r(2)=0.967, n=23, p<0.001) indicated that similar biogeochemical processes control the temporal and spatial distribution in the water column. The larger fraction of MeHg in the lake spike compared to the ambient pool in the hypolimnion suggests that lake spike may be more available for methylation. A linear relationship of DOC to both filterable ambient HgT (r(2)=0.406, n=27, p<0.001) and lake spike HgT (r(2)=0.314, n=15, p=0.002) suggest a role of organic matter in Hg transport and cycling. However, a weak relationship between the ambient and lake spike pools of MeHg to DOC indicated that other processes have a major role in controlling the abundance and distribution of MeHg. Our results suggest that Fe and Mn play important roles in the transport and cycling of ambient and spike HgT and MeHg in the hypolimnion, in part through processes linked to the formation and dissolution of organic matter-containing Fe and Mn hydrous oxides particles.     

Analysis of Methods for Parallel Operation of Frequency Converters

Consideration is given to methods for the parallel operation of frequency converters by applying the active load division. The simulation model of the converter is presented. It consists of three parallel independent modules. A new principle of constructing individual modules of a frequency converter and the principle of their communication interface exhibiting resistance to destabilizing effects and allowing safe operation under nominal conditions even with a 5- to 10% range in time and amplitude values of pilot signals are developed.     

Feature analysis of women's wedding dresses in new,style weddings in the Wu culture region in modern times北大核心CSCD

To further clarify the features of wedding dresses in new, style weddings in cities and towns of the Wu culture region, the author sorted out and made a statistical analysis of modern journals and periodicals as well as conducted a comparison in combination with diaries of celebrities and novels in modern times to collect 368 wedding photos in total in the Wu culture region. The analysis results indicate that wedding dresses in the Wu culture region were mainly of modified styles from 1859 to 1949, the development of wedding dresses went through the stages of unitary styles, mixed styles and diversified styles, in each of which there were also representative regular ways of matching. In general, wedding dresses were in simple, elegant and delicate styles, and the silhouettes kept up with popular western styles, showing a high level of acceptance of foreign cultures. The colors of wedding dresses tended to combinations of light colors, while traditional colors were gradually reduced. Besides, patterns of flowers and plants with thin stems and leaves were mainly used to decorate wedding dresses, showing the distribution features of scattering and covering. © 2018 China Silk Association. All rights reserved.