Chemical Characteristics of Carbonaceous Aerosols During Dust Storms over Xi'an in China   总被引：1，自引：0，他引：1  

LI Xuxiang  CAO Junji  Judith CHOW  HAN Yongming  Shuncheng LEE  John WATSON 《大气科学进展》2008,25(5):847-855

Characterization of carbonaceous aerosols including CC （carbonate carbon）, OC （organic carbon）, and EC （elemental carbon） were investigated at Xi＇an, China, near Asian dust source regions in spring 2002. OC varied between 8.2 and 63.7μgm^- 3, while EC ranged between 2.4 and 17.2 μ m^-3 during the observation period. OC variations followed a similar pattern to EC and the correlation coefficient between OC and EC is 0.89 （n=31）. The average percentage of total carbon （TC, sum of CC, OC, and EC） in PM2.5 during dust storm （DS） events was 13.6%, which is lower than that during non-dust storm （NDS） periods （22.7%）. CC, OC, and EC accounted for 12.9%, 70.7%, and 16.4% of TC during DS events, respectively. The average ratio of OC/EC was 5.0 in DS events and 3.3 in NDS periods. The OC-EC correlation （R^2=0.76, n=6） was good in DS events, while it was stronger （R^2=0.90, n=25） in NDS periods. The percentage of watersoluble OC （WSOC） in TC accounted for 15.7%, and varied between 13.3% and 22.3% during DS events. The distribution of eight carbon fractions indicated that local emissions such as motor vehicle exhaust were the dominant contributors to carbonaceous particles. During DS events, soil dust dominated the chemical composition, contributing 69% to the PM2.5 mass, followed by organic matter （12.8%）, sulfate （4%）, EC （2.2%）, and chloride （1.6%）. Consequently, CC was mainly entrained by Asian dust. However, even in the atmosphere near Asian dust source regions, OC and EC in atmospheric dust were controlled by local emission rather titan the transport of Asian dust.  相似文献   

内蒙古中南部出露地壳元素丰度值的估算     

孟月玥  陈岳龙  林宇 《地质通报》2010,29(6):880-890

运用区域大规模采样方法,对内蒙古中南部地区所采样品进行元素丰度值加权计算,这是建立区域地壳模型的基础工作之一,同时也为化探异常的检出提供较为准确的背景值。研究区涉及内蒙古地轴和内蒙古中部造山系2个构造单元。采用加权求平均值的方法,得到内蒙古中南部出露地壳10种常量元素氧化物和40种微量元素的丰度值。经地表热流值、地震平均波速和元素比值方法检验后证明所得结果合理。计算所得内蒙古中南部出露地壳平均成分为花岗闪长质,与目前一般认为的结论相同。将结果与其他地区进行比较分析后可知,内蒙古中南部出露的地壳与全球上地壳的组成基本一致。由微量元素、稀土元素的图解和内蒙古中南部出露地壳的元素丰度与中国东部出露地壳元素丰度的对比可以看出,整体上,内蒙古中南部具有较强的壳内分异作用和地壳增生作用(地幔物质加入)。  相似文献   

上海市近岸海域表层沉积物类型与元素丰度相关关系特征   总被引：1，自引：1，他引：0  

何中发 《上海国土资源》2010,(1):1-5

通过上海市近岸海域多目标区域地球化学调查,共采集947件表层沉积物样品,分析测试了52种化学元素以及pH值和有机碳等指标。总结了该区域表层沉积物及深层沉积物类型和分布特征,沉积物类型主要为细砂、粉砂质砂、砂质粉砂、粉砂、粘土质粉砂,其中粘土质粉砂分布最为广泛。元素含量与砂含量呈正相关的元素主要为SiO2、Sr、Na2O等。其它指标大都与粘土含量呈正相关关系。  相似文献   

Deciphering signals of late Holocene fluvial and aeolian supply from a shelf sediment depocentre off Senegal (north‐west Africa)     

Jean Nizou  Till J.J. Hanebuth  Christoph Vogt 《第四纪科学杂志》2011,26(4):411-421

High‐resolution climatic records of the late Holocene along the north‐west African continental margin are scarce. Here we combine sediment grain size, elemental distribution and mineral assemblage data to trace dust and riverine sources at a shallow‐marine sediment depocentre in the vicinity of the Senegal River mouth. The aim is to understand how these terrigenous components reflect climate variability during the late Holocene. Major element contents were measured and mineral identification was performed on three sub‐fractions of our sediment core: (i) fluvial material < 2 µm, (ii) aeolian material of 18–63 µm and (iii) a sub‐fraction of dual‐origin material of 2–18 µm. Results show that more than 80% of the total Al and Fe terrigenous bulk content is present in the fluviogenic fraction. In contrast, Ti, K and Si cannot be considered as proxies for one specific source off Senegal. The Al/Ca ratio, recording the continental river runoff, reveals two dry periods from 3010 to 2750 cal a BP and from 1900 to 1000 cal a BP, and two main humid periods from 2750 to 1900 cal a BP and from 1000 to 700 cal a BP. The match between (i) intervals of low river runoff inferred by low Al/Ca values, (ii) reduced river discharge inferred by integrated palynological data from offshore Senegal and (iii) periods of enhanced dune reactivation in Mali confirms this interpretation. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Application of Laser Ablation ICP-MS to U-Th-Pb Dating of Monazite   总被引：2，自引：1，他引：2  

Jan Kosler  Mike N. Tubrett  Paul J. Sylvester 《Geostandards and Geoanalytical Research》2001,25(2-3):375-386

Recent advances in laser ablation ICP-MS techniques allow accurate U-Th-Pb age dating of monazites that are as young as several tens of million years to a precision better than 2%. Accuracy of the age determinations has been improved by true real-time mass bias correction via nebulisation of a solution containing enriched ²³³U and natural Tl isotopes. The Tl-U tracer solution eliminates possible effects of variable sample matrices on the precision and accuracy of measured isotopic ratios. Mass bias corrections based on measured ²⁰⁵Tl/²³³U ratios in the tracer solution allow direct measurement of ²³⁵U in monazite. Combined with high-sensitivity laser ablation ICP-MS measurements, direct measurement of ²³⁵U particularly improves the precision of U-Pb dating of young monazites. Correction for laser-induced Pb/U and Pb/Th elemental fractionation is based on a mathematical treatment of time resolved count-rate data that is independent of laser ablation characteristics, does not require external standardisation and allows variable laser pit size or raster patterns for each measurement. The new procedures make the LA ICP-MS technique more flexible for in situ U-Th-Pb analysis.  相似文献   

Geochemical Characteristics of the Sandstone—type Uranium Deposits in Northern Sichuan Province     

王旺章  张筑凤 《中国地球化学学报》1995,14(2):152-159

Described in detail in this paper are the geochemical characteristics of the sandstone-type uranium deposits in northern Sichuan Province .Favorable and unfavor-able conditions for the enrichment of uranium are explored on the basis of the elemental abundances and ratios of U,Th and K determined by gamma-ray spectroscopy. Gamma-ray spectroscopic(U, Th and K) and XRF analyses(As, Ba) are helpful to distinguish U-bearing light-colored sandstones from U-barren light-colored ones and red sandstones (red claystone) from light-colored sandstones. Therefore, the favorable target area for prospecting the sandstone-type uranium deposits can be difined in northern Sichuan Province.  相似文献   

Element-Enrichment Factors in Lichens from Terceira, Santa Maria and Madeira Islands (Azores and Madeira Archipelagoes)     

B. J. Vieira  M. C. Freitas  A. F. Rodrigues  A. M. G. Pacheco  P. M. Soares  N. Correia 《Journal of Atmospheric Chemistry》2004,49(1-3):231-249

In this study, more than 20 minor and trace elements have been determined by INAA (instrumental neutron activation analysis), in different species of lichens in three Portuguese islands of the Central North Atlantic (Santa Maria, Terceira, and Madeira Islands). The foliose species Parmotrema bangii, Parmotrema robustum, Parmotrema crinitum, Flavoparmelia caperata, Platismatia glauca, and the fruiticose species Ramalina canariensis, Ramalina farinacea, Ramalina implectens, Ramalina pusilla, Cladonia furcata, Cladonia coniocraea, Usnea dasaea, Usnea esperantiana, were the collected species. Samples of superficial soils were also collected and the fraction below 64 m was analysed. The enrichment factors relative to this fraction using Al as the normalising element were calculated. Fruiticose and foliose lichens displayed different EF values concerning bromine and potassium. The first was more enriched in the foliose species while the latter was more enriched in the fruiticose species and was assigned to the physiological response. Enrichment was found for Mg, Cs, As, Hg, Na, Zn, and Cl, in all the species. Lichen-based concentration patterns were shown for Na, Al, Cl, Br, Sb, Ce, and Hg and compared to similar patterns in Portugal mainland. In general, the patterns compared well except for Cl, Na, and Br. Background levels of the epiphytic lichens collected in the islands were obtained.  相似文献   

An Examination of the Oxidation of Elemental Mercury in the Presence of Halide Surfaces     

Guey-Rong Sheu  Robert P. Mason 《Journal of Atmospheric Chemistry》2004,48(2):107-130

Recent field investigations in polar regions, and over the ocean, have suggested that elemental mercury (Hg⁰) can be photochemically oxidized in the presence of reactive halogen species that are formed in the presence of salt particles, typically through a reactive catalytic cycle involving ozone destruction. Furthermore, these studies have suggested that the Hg⁰ oxidation reaction involves the reaction with reactive bromine species such as Br, BrO, and Br₂. To investigate these reactions in more detail, we performed experiments using a quartz reactive chamber so that the oxidation of Hg⁰, and the formation of ionic Hg products, could be examined in detail under different reaction scenarios, but at realistic levels of Hg. To examine if the reactions were enhanced by the presence of deliquescent salt surfaces, as has been postulated to be the case for the formation of reactive halogens, one surface of the cell was coated with either NaCl or NaBr for some experiments. In addition to laboratory experiments with a Xenon lamp, outdoor experiments under natural light were also conducted. The results of these studies showed that oxidation of Hg⁰ did not occur in the dark, except in the presence of a deliquescent NaBr salt surface. The rate of oxidation was slow in the absence of salt surfaces, and in the absence of low wavelength light (<324 nm). In the presence of NaCl surfaces, oxidation rates were at least two orders of magnitude faster, but the rate was further increased in the presence of NaBr, by a further factor of 25. With outdoor light, while the rates of oxidation were lower, the results were similar overall. The results are discussed in terms of the reactions occurring and the mechanisms of Hg⁰ oxidation. Finally, the implications of these reactions to the overall global Hg cycle are discussed.  相似文献   

芽孢杆菌HBS4还原亚硒酸钠为单质硒的实验研究     

李瑞萍鲁安怀  郝瑞霞马黠静吕明  鲁志强 《岩石矿物学杂志》2005,24(6):598-602

利用从油藏中分离的芽孢杆菌HBS4在兼性厌氧情况下作用于剧毒物质亚硒酸钠,36 h后1～11mM的样品中均出现了大量红色颗粒沉淀物.生物显微镜观察发现,在很多细菌内部出现一颗到多颗红色的圆形颗粒,排列方式有单链、双链、弧线和无规则排列,并且在细胞周围释放有游离态的红色颗粒.XPS测试红色沉淀物发现四价硒全部还原为零价硒.实验还发现添加葡萄糖对单质硒的产量有很大的促进作用.  相似文献   

High exposure of Chinese mercury mine workers to elemental mercury vapor and their increased hair methylmercury levels： A preliminary report     

Mineshi Sakamoto Xinbin FENG Ping LI Guangle QIU Hongmei JIANG Minoru Yoshida Toyoto Iwata Xiaojie LIU Katsuyuki Murata 《中国地球化学学报》2006,25(B08):42-43

Objectives： To assess the exposure to elemental mercury （Hg0） vapor and methylmercury （MeHg） among mercury mine workers in an area of Guizhou Province, China. Methods： Urine total mercury （THg） and hair THg and MeHg were measured in 26 mercury miners and smelters （i.e., exposed group）, and 52 control subjects （unexposed group）. Results： The mine workers showed high geometric mean THg concentrations in urine （258 ng/mL, 226 μg/g creatinine） and hair （20.0 μg/g）. The urine Hg level of smelters, in particular, was extremely high （338 μg/g creatinine in urine）. The highest urine THg reached 4580 μg/g creatinine. THg concentrations in urine and hair showed a significant correlation in the exposed group （r=0.62）, indicating the adhesion of HgO vapor to hair. However, no such significant correlation was found in the control group.  相似文献