S(IV) Autoxidation in Atmospheric Liquid Water: The Role of Fe(II) and the Effect of Oxalate     

Irena Grgićc  Marjeta Pozničc  Mirko Bizjak 《Journal of Atmospheric Chemistry》1999,33(1):89-102

The reactivity of dissolved iron compounds towards different pollutants and photooxidants in atmospheric liquid water depends upon the oxidation state and speciation of iron. Our measurements of the oxidation state of dissolved iron eluted from aerosol particles (Dae: 0.4–1.6 c="/content/l227l81755515873/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">m) collected in the urban atmosphere of Ljubljana showed that a large fraction of the iron content is present as Fe(II). The concentration ratio [Fe(II)]/[Fe(III)] varied between 0.9 and 3.1. The kinetics of S(IV) autoxidation catalyzed by Fe(II) under the conditions representative for acidified atmospheric liquid water and the influence of oxalate on this reaction under dark conditions was investigated. The reaction rate is the same if Fe(II) or Fe(III) is used as a catalyst under the condition that Fe(II) can be oxidized in Fe(III), which is the catalytically active species. Oxalate has a strong inhibiting effect on the S(IV) autoxidation in the presence of Fe(II). The reaction is autocatalytic with an induction period, that increases with higher concentrations of oxalate. The inhibiting effect of oxalate differs according to whether iron is initially in the Fe(II) or Fe(III) state. However, in both cases the inhibition by oxalate is a result of the formation of complexes with the catalyst.  相似文献   

Some considerations on the 1971 Etna eruption and on the tectonophysics of the Mediterranean area     

Prof. Dr. Dr. h. c. Alfred Rittmann  Dr. Romolo Romano  Dr. Carmelo Sturiale 《International Journal of Earth Sciences》1973,62(2):418-430

On the basis of an uninterrupted observation of the events and of a careful geological survey, the authors give a short description of the Etna eruption on April–June 1971, which is illustrated by a detailed chronogram. The eruptive mechanism is fully discussed. Some remarks are added to show the importance of volcanological and magmatological data for the understanding of the tectonophysics in the Mediterranean area.  相似文献   

水泥粉体深层喷射搅拌桩复合地基处理及其效果     

程礼来  郜云峰  苗先文  段宗贵 《河南国土资源》1998,(1)

水泥粉体深层喷射搅拌桩与干振碎石桩〔１〕、干振灰土桩等一样,也是处理松软地基土的一种有效方法。但与干振碎石桩等其他挤密型复合地基处理方法不同,水泥粉体深层喷射搅拌桩属于摩擦桩型。由于天然地基土对桩体的侧摩擦力和端阻力的共同作用,使复合地基的承载力大幅度提高。然而人们普遍认为,水泥粉体深层喷射搅拌桩法复合地基处理不能解决场地土的液化问题。本文通过工程实例和瑞雷波检测结果,证实了该方法处理的复合地基,除了承载力有较大幅度的提高外,地基土的抗液化能力也可以得到相应的加强。  相似文献   

The impact of water resources development projects on water vapor pressure trends in a semi-arid region, Turkey     

Tahsin Tonkaz  Mahmut Çetin  Kâzım Tülücü 《Climatic change》2007,82(1-2):195-209

The aim of this study was to investigate long-term seasonal trends and decadal change patterns of monthly mean water vapor pressure (WVP) observation series at 16 meteorological stations scattered point-wisely over the Southeastern Anatolian Project (GAP) area in Turkey, where large-scale soil and water development projects have been put into practice since the 1970s. The record length of WVP observation series of each station varied between 31- and 41-years between 1962 and 2002. The monthly mean WVP observation series of each station was rearranged on seasonal basis. Sequential Mann–Kendall trend test, Sen’s slope estimator, and Spearman’s rank–order correlation tests were employed for detection of likely trends, and Kruskall–Wallis test was used to detect decadal variations in WVP series of each observation station. A possible area of representation for each meteorological station was determined by using the Thiessen polygons technique in a geographical information systems media. It was found that 15 seasonal WVP series have a positive trend covering 97% of the GAP area in the summer season; although one WVP series has a negative trend direction. However, in the spring season, 33% of the area had a positive trend, and a negative trend did not appear in any stations. WVP records in the winter season showed an increasing trend over 19% of the GAP area, whereas a decreasing trend prevailed in 9% of the area. The study results led us to conclude that the substantial increase of WVP observations in summer season could be attributed to both the shift from rain-fed agriculture to irrigated agriculture being made increasingly spacious year by year and building large water reservoirs in the GAP located in a semi-arid region. The results also indirectly suggested that the historical trends in the WVP parameters might be related to global climate change phenomenon.  相似文献   

Nonlinear Analysis of the Frequency-magnitude Relationship in the Western Circum-Pacific Region     

Changyuan?Qinc.qin@uea.ac.uk" title="qin@lemnos.geo.auth.gr  c.qin@uea.ac.uk" itemprop="email" data-track="click" data-track-action="Email author" data-track-label="">Email author 《Pure and Applied Geophysics》2005,162(1):91-107

— It has long been realized that the linear Gutenberg-Richter model arduously describes the frequency-magnitude relationship for the magnitude span ranging from small to large earthquakes because of the breakdown of the self-similarity rule due to the changing scaling of the magnitude. Three different segments should be observed from small (usually M < 3.0), through moderate (M < M_c, where M_c is the frequency-magnitude turning point caused by the seismogenic thickness), to large earthquakes (M c="/content/j6ng5fr29u8c04dv/xxlarge8805.gif" alt="ge" align="MIDDLE" BORDER="0"> M_c). We will only concentrate on the moderate and large earthquakes due to their importance. The breakdown of the self-similarity rule from moderate to large earthquakes occurs where the earthquake is big enough to cut through the entire seismogenic layer. A nonlinear c="/content/j6ng5fr29u8c04dv/xxlarge8216.gif" alt="lsquo" align="BASELINE" BORDER="0">hyperbolicc="/content/j6ng5fr29u8c04dv/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0"> model, which fits two linear relations smoothly, c="/content/j6ng5fr29u8c04dv/MediaObjects/s00024-004-2581-7flb1.gif" alt="MediaObjects/s00024-004-2581-7flb1.gif" align="middle"> is studied in the present paper, where N is the cumulative number of earthquakes with magnitudes larger than or equal to M; a₁ to a₅ are constants to be calculated. The G-R linear relation is actually a special case of the present nonlinear model, i.e., a₃ or a₅ equal to zero. The nonlinear form, with the support of a reasonable physical mechanism, can generally give a better fitting with comparatively minor errors for complete data sets, especially for the areas where large earthquakes are numerous. In order to demonstrate its superiority to the linear G-R relation, thirteen seismogenic zones are examined around the western part of the Circum-Pacific region and western part of China and it is found that the fitting errors from this nonlinear model are, as expected, generally much smaller than those for G-R. Furthermore, the parameter a₄ is believed to relate with the saturated magnitude M_c,which to some extent reflects the mean thickness of the seismogenic layer.Acknowledgement. The author thanks Dr Paul W. Burton for his useful discussions. He appreciates two anonymous reviewersc="/content/j6ng5fr29u8c04dv/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0"> comments and suggestions which enhanced the quality of the paper. This research was partially supported by the project EPAN-M.4.3/2013555 of bilateral cooperation between Greece and China funded by the General Secretariat of Research & Technology of Greece and by the project of UK-China Science and Technology Fund funded by the British Council. Some figures were made with GMT software (WESSEL and SMITH, 1995).  相似文献   

Removal of cyanide from aqueous solutions by plain and metal-impregnated granular activated carbons     

H. Deveci  E.Y. YazıcıI. Alp  T. Uslu 《International Journal of Mineral Processing》2006

In this study, the removal of free cyanide from aqueous solutions by activated carbon was investigated. Effects of metal impregnation (Cu and Ag), aeration, and concentrations of adsorbent and cyanide on the rate and extent of the removal of cyanide were studied. The results have shown that the capacity of activated carbon for the removal of cyanide can be significantly improved (up to 6.3-fold) via impregnation of activated carbon with metals such as copper and silver. Silver-impregnated activated carbon was found to be the most effective at the reduction of cyanide level in solution. This appeared to be coupled with its comparatively high metal content after impregnation process where silver (5.07%) could be more readily loaded on activated carbon than copper (0.43%). Kinetics and equilibrium data for cyanide removal by plain and metal-impregnated activated carbons were determined to be consistent with the pseudo second-order kinetics and the Langmuir adsorption isotherms, respectively. Aeration (0.27 l/min) was found to exert a profound effect on the process leading to a 5.5–49.1% enhancement in the performances of plain and metal-impregnated activated carbons. This enhancement could be attributed to the increase in the availability of active sites on activated carbon for adsorption and the catalytic oxidising activity of activated carbon in the presence of oxygen. Practical limiting capacity of plain, copper- and silver-impregnated activated carbons for the removal of cyanide were experimentally determined to be 19.7, 22.4 and 29.6 mg/g, respectively.  相似文献   

Hommage au professeur Jaag     

Dr. h. c. R. Colas 《Aquatic Sciences - Research Across Boundaries》1960,22(1):21-22

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Investigation of water quality on Gökçekaya dam lake using multivariate statistical analysis,in Eskişehir,Turkey   总被引：1，自引：0，他引：1  

B. S. Akin  T. Atıcı  H. Katircioglu  F. Keskin 《Environmental Earth Sciences》2011,63(6):1251-1261

Gökçekaya Dam is one of the dams located on the Sakarya River (Eski?ehir) in Turkey and is approximately 38 years old. No study regarding to the water quality of the dam lake has been hitherto made. This study aimed at determining the seasonal variations with physical, chemical, and biological parameters of the water quality of the dam lake. Depth-wise water samples were taken from five selected stations, in seasonal periods during 2005–2008, and anlayzed. The quality of water was classified in accordance with the results and taking into consideration many parameters. At the same time, number and type diversities of dissolved heavy metals and algae population were analyzed. Using principal component analysis (PCA) and classification analysis (CA) methods, differences between these parameters and samples from stations have been determined . The analysis showed that Gökçekaya dam lake, formerly an oligotrophic lake, has become a mesotrophic lake. And according to the results thereof the Lake has mezotrophic characteristics due to the sudden changes (including household waste water inflow and opening the Sar?yar dam lake shutters) in certain periods and in some stations. Hierarchical clustering analysis, revealed no significant difference between the measured parameters. And according to the Water Pollution Control Regulations in Turkey (WPCR) Gökçekaya dam lake is in the first class quality in terms of anions, cations, heavy metals, temperature, and pH values. However, the is of first class quality presence of nitrite reduces the water quality in the lake and causes this lake to be classified in the fourth class quality.  相似文献   

Erratum to: Radio AGN in the local universe: unification,triggering and evolution     

Clive?TadhunterEmail author 《Astronomy and Astrophysics Review》2016,24(1):12

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Theoretical study of the local charge compensation and spectroscopic properties of B-type carbonate defects in apatite     

Haohao Yi  Etienne Balan  Christel Gervais  Loïc Ségalen  Marc Blanchard  Michele Lazzeri 《Physics and Chemistry of Minerals》2014,41(5):347-359

The structure and spectroscopic properties of selected models of B-type carbonate defects in apatite locally compensated by fluoride or hydroxyl ions are investigated using first-principles quantum mechanical calculations. Theoretical infrared absorption spectra and ¹³C, and ¹⁹F nuclear magnetic resonance chemical shifts are determined. Among the investigated models, only the clumped (CO₃ ^2?, F^?) defect, with the carbonate group close to the sloping face of the tetrahedral site and the F^? ion at the remaining apex, corresponds to previous experimental observations performed on carbonate-fluorapatite samples. Although the substitution of hydroxyl by fluoride ions is commonly observed in minerals, the clumped (CO₃ ^2?, OH^?) defects are unlikely to occur in apatite, considering both their theoretical spectroscopic properties and relative stability. Anionic F^? for OH^? exchange between channel and B sites displays a preference of ~20 kJ/mol for the local charge compensation by fluoride ions at the B-site, pointing to a significantly different behavior of F^? and OH^? ions in the charge compensation mechanism. This difference is ascribed to the poor H-bond acceptor character of available oxygen atoms surrounding the apex of the tetrahedral site. The explicit calculation of the infrared absorption spectra of the defect models is also used to interpret the significant difference observed in the linewidth of the ν₂ and ν₃ CO₃ infrared powder absorption bands of carbonated apatite samples. It is shown that for a concentration of 4.4 wt% of CO₂, long-range electrostatic effects already significantly contribute to the broadening of the ν₃ CO₃ bands in apatite.  相似文献