258 resultados para La_(2-x)Sr_xCuO_4


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TO understand possible reproductive interaction between Crassostrea ariakensis (Fujita, 1913) and C. sikamea (Amemiya, 1928), which coexist ill estuaries of China and Japan, we conducted 2 X 2 factorial crosses between the two species. Asymmetry in fertilization success was observed where C. sikamea eggs can be fertilized be C. ariakensis the receprocal cross resulted in no fertilization. Fertilization Success ill C.sikamea female X C. ariakemvis male (SA) crosses was lower than that in the two intraspecific crosses and produced larvae that had similar growth the rate as their maternal species during the first nine days because of maternal effects. After that, genome incompatibility casted negative effects on the growth and survival of the hybrid larvae. Most hybrid larvae died during metamorphosis. but a small number of spat survived. Genetic analysis revealed that the survived SA spat contained DNA from both species and were the hybried. This study demonstrates that hybridization between C. ariakensis and C. sikamea is possible in one direction.

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Bacteria isolated from a highly toxic sample of gastropod Nassarius semiplicatus in Lianyungang, Jiangsu Province in July 2007, were studied to probe into the relationship between bacteria and toxicity of nassariid gastropod. The toxicity of the gastropod sample was 2 x 10(2) mouse unit (MU) Per gram Of tissue (wet weight). High concentration of tetrodotoxin (TTX) and its analogues (TTXs) were found in the digestive gland and muscle of the gastropod, using high performance liquid chromatography coupled with mass chromatography (LC-MS). Bacterial strains isolated from the digestive gland were cultured and screened for TTX with a competitive ELISA method. Tetrodotoxin was detected in a proportion of bacterial strains, but the toxin content was low. Partial 16S ribosomal DNA (rDNA) of the TTX-producing strains was then sequenced and compared with those published in the GenBank to tentatively identify the toxic strains. It was found that most of the toxic strains were closely affiliated with genus Vibrio, and the others were related to genus Shewanella, Marinomonas, Tenacibaculum and Aeromonas. These findings suggest that tetrodotoxin-producing bacteria might play an important role in tetrodotoxin accumulation/production in N. semiplicatus. (C) 2008 Elsevier Ltd. All rights reserved.

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In this paper, we determined the concentrations of antimony species (antimonite (Sb(III)), antimonate (Sb(V)) and dissolved inorganic antimony (DISb)) and arsenic, in Bohai Bay seawaters, as well as the relationships of the analytes with environmental factors such as seawater characteristics (e.g., suspended particulate material (SPM), salinity and total organic carbon (TOC)), heavy metals, nutrients and phytoplankton species, and evaluated the sources of arsenic and antimony. Dissolved arsenic and antimony concentrations in the surface waters were ranging spatially from 1.03 to 1.26 ng/ml and 0.386 to 1.075 ng/ml, with mean values of 1.18 and 0.562 ng/ml, respectively. Sb(V) as the prominent chemical species constituted about 89%. Regarding arsenic concentrations in the surface waters, there was a tendency for a small variation. However, antimony species concentrations were much variable than arsenic. The highest arsenic and antimony concentrations were found near the Haihe Estuary. These distribution patterns were controlled mainly by environmental factors, biological activities and sources. In this region, DISb and Sb(V) negatively correlated with salinity. Besides, arsenic and antimony correlated well with the nutrients, chlorophyll a and phytoplankton, implying that arsenic and antimony had been involved in biological cycling. In addition, according to our estimate, about 333.5 x 10(8) mg/year of arsenic and 454.2 x 10(8) mg/year of antimony reached Bohai Bay via rivers. (C) 2010 Elsevier Ltd. All rights reserved.

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The distributions of heterotrophic bacterial abundance and production were investigated in the East China Sea and the Yellow Sea during the autumn of 2000 and spring of 2001. Bacterial abundance varied in the range 3.2-15.7 (averaging 5.7) x 10(5) and 2.3-13.6 (averaging 6.2) x 10(5) cells cm(-3) in the spring and autumn, respectively. During autumn, bacterial production (BP) (0.27-7.77 mg C m(-3) day(-1)) was on average 3 fold that in spring (0.001-2.04 mg C m(-3) day(-1)). Bacterial average turnover rate (ratio of bacterial production:bacterial biomass, mu=0.21 day(-1)) in autumn was 3 times as high as in spring (0.07 day(-1)). The ratio of integrated bacterial biomass to integrated phytoplankton biomass in the euphotic zone ranged from 4 to 101% (averaging 35%) in spring and 24 to 556% (averaging 121%) in autumn. The results indicate that the distributions of heterotrophic bacteria were controlled generally by temperature in spring and additionally by substrate supply in autumn. (C) 2010 Elsevier Ltd. All rights reserved.

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The impacts of Prorocentrum donghaiense Lu and Alexandrium catenella Balech, causative species of the large-scale HAB in the East China Sea, were studied under laboratory conditions. According to bloom densities, the effects of monoculture and mixture of the two species were examined on the egg-hatching success of Argopecten irradians Lamarck, and the population growth of Brachionus plicatilis Muller and Moina mongolica Daday. The results showed that monoculture of A. catenella had a significant inhibition on the egg hatching success of A. irradians, and the population growth of B. plicatilis and M. mongolica. The median effective densities ( EDSo) inhibiting the egg hatching success of A. irradians for 24 h and the population growth of B. plicatilis and M. mongolica for 96 h were 800, 630, and 2 400 cells/cm(3), respectively. Monoculture of P. donghaiense has no such inhibitory effect on the egg hatching success of A. irradians; P. donghaiense at lower suitable densities could sustain the population growth of B. plicatilis (1 x 10(4) similar to 3 x 10(4)cells/cm(3)) and M. mongolica (2 x 10(4) similar to 5 x 10(4) cells/cm(3)); P. doaghaiense at higher densities had significantly adverse effect on the population growth of B. plicatilis (4 x 10(4) similar to 10 x 10(4) cells/cm(3)) and M. mongolica (10 x 10(4) cells/cm(3)). When the two algae were mixed according to bloom densities, P. donghaiense at suitable densities to some extent could decrease the toxicity of A. catenella to B. plicatilis and M. mongolica. The results indicated that the large-scale HAB in the East China Sea could have adverse effect on zooplankton, and might further influence the marine ecosystem, especially when there was also Alexandrium bloom.

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Two different stocks (A and B) of the bay scallop Argopecten irradialls irradians (Lamarck, 1819) were used to test mass selection on growth. Stock A was a descending stock from the initial introduction from U.S.A. in 1982, which had been cultured in China for about 20 years. Stock B was the third generation from a recent introduction from U.S.A. in 1999. Truncation selection was conducted by selecting the largest 11% scallops in shell length from Stock A and the largest 12.7% scallops from Stock B as parents for the respective selected groups. Before the removal of parents for truncation selection, equal numbers of scallops were randomly chosen from Stock A and B to serve as parents for the control groups. Offspring from the four groups were reared under the same hatchery, nursery, and grow-out conditions. Values of response to selection and realized heritability at larvae, spat and grow-out stages for Stock B were all significantly (P < 0.001) higher than its counterpart for Stock A. For Stock A, no significant response to selection was observed (P > 0.05) at any stage, and the realized heritability for shell length was 0.015 +/- 0.024 for larvae, 0.040 +/- 0.027 for spat, and 0.080 +/- 0.009 for grow-out, respectively. For Stock B, however, significant (P < 0.05) response to selection was observed, and the realized heritability for shell length was 0.511 +/- 0.010 for larvae, 0.341 +/- 0.022 for spat, and 0.338 +/- 0.015 for grow-out. On average, responses to selection at the three stages for Stock B was 30 x, 7.1 x, and 3 x higher than its counterpart for Stock A, respectively. Accordingly, realized heritability at above stages for Stock B was 33 X, 7.5 x, and 3.2 X higher than its counterpart for Stock A, respectively. Differences in response to selection and realized heritability between the two stocks are presumably due to differences in genetic variability. As the 20th generation from the initial introduction consisted of only 26 scallops, Stock A is known to be highly inbred, while inbreeding in Stock B is negligible. (C) 2004 Elsevier B.V. All rights reserved.

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为了深入了解眷小麦新创种质陇矮1号的矮秆性遗传规律,2000~200l午对“陇矮1号”的矮秆遗传特性进行了较为系统的研究。从“陇矮1号”分别与三个高秆亲本“老芒麦”、“和尚头”和“高原602”的杂种F-1代株高表现可知,其F3代株高介于高亲值与中亲值之间,且D为负值,说明“陇矮1号”的矮秆特性受隐性矮秆基因控制。“陇矮1号”与“老芒麦”、“和尚头”和“高原602”的F-2代株高分离表明,“陇矮1号”的矮秆特性受2对或2对以上隐性基因控制。此外,超亲分离表明“陇矮1号”的矮秆特性还受到一些微效基因的影响。对各组合回交世代BC-1和BC-2株高分离结果进行X’测验,BCl的矮秆株数与半矮秆株数之比为3:1,而BC。的半矮秆株数与高秆株数之比为1:3。因此,推断“陇矮I号”的矮秆特性受2对主效隐性矮秆基因控制。

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A sensitive and efficient method for simultaneous determination of glutamic acid (Glu), gamma-amino-butyric acid (GABA), dopamine (DA), 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) in rat endbrains was developed by high-performance liquid chromatography (HPLC) with fluorescence detection and on-line mass spectrometric identification following derivatization with 1,2-benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC). Different parameters which influenced derivatization and separation were optimized. The complete separation of five neurotransmitter (NT) derivatives was performed on a reversed-phase Hypersil BDS-C-18 column with a gradient elution. The rapid structure identification of five neurotransmitter derivatives was carried out by on-line mass spectrometry with electrospray ionization (ESI) source in positive ion mode, and the BCEOC-labeled derivatives were characterized by easy-to-interpret mass spectra. Stability of derivatives, repeatability, precision and accuracy were evaluated and the results were excellent for efficient HPLC analysis. The quantitative linear range of five neurotransmitters were 2.441-2 x 10(4) nM, and limits of detection were in the range of 0.398-1.258 nM (S/N = 3:1). The changes of their concentrations in endbrains of three rat groups were also studied using this HPLC fluorescence detection method. The results indicated that exhausting exercise could obviously influence the concentrations of neurotransmitters in rat endbrains. The established method exhibited excellent validity, high sensitivity and convenience, and provided a new technique for simultaneous analysis of monoamine and amino acid neurotransmitters in rat brain. (C) 2008 Elsevier B.V. All rights reserved.

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A highly selective and accurate method based on derivatization with dansyl chloride coupled with liquid chromatography-mass spectrometry has been developed for identification of natural pharmacologically active phenolic compounds in extracts of Lomatogonium rotatum plants (Tibetan herbal medicine) obtained by solid-phase extraction. The number of hydroxyl groups on the dansylated phenols was estimated by LC-MS-MS analysis in positive-ion mode. Dansyl derivatization of the compounds introduced basic secondary nitrogen into the phenolic core structures and this was readily ionized when acidic HPLC mobile phases were used. MS fragmentation of the derivatives generated intense protonated molecular ions of m/z [MH](+) (phenol aglycones were transformed into the corresponding free phenols by cleavage of an aglycone bond). Collision-induced dissociation of the protonated molecule generated characteristic product ions of m/z 234 and 171 corresponding to the protonated 5-(dimethylamino)naphthalene sulfoxide and 5 -(dimethylamino) naphthalene moieties, respectively. Selected reaction monitoring based on the m/z [MH](+) to 234 and 171 transitions was highly specific for these phenolic compounds. Characteristic ions with m/z values of [MH - 234](+), [MH 2 x 234](+), and [MH - 3 x 234](+) were of great importance for estimation of the presence of multihydroxyl groups on the phenolic backbone.

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Using knowledge of geology, geochemistry, coal petrology, mineralogy, by means of a variety of advanced measuring methods such as inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled atomic emission spectrometry (ICP-AES), X-ray powder diffraction (XRD), scanning electron microscopy with energy-dispersive spectrometer(SEM-EDS), sequential chemical extract and density fractions, the characteristics of trace elements and minerals in Jurassic Beipiao coal mine under inland limnetic sedimentary environment and in late Permian Jianxin and Qiaotou coal mines under paralic swamp sedimentary environment were studied. Compared with the average concentration in the world bituminous coals, the Beipiao coal was characterized by relatively high contents of Sc, Ti, Cr, Co, Ni, Zn, Se, Sr, Zr, Y, Ba, REE and Th, and lower contents of V, Rb, Cd, Sn, Pb, Bi and U; while the Jianxin coal was relatively enriched in Li, Sc, Ga, Sr, Y, Nb, Sb, Th and U, with low concentration of Be, Co, Ni, Cu, Ge, Zr, Mo, Cd, Cs, Ba, Pb and Bi; and the Qiaotou coal was enriched in Li, Sc, Sr, Nb, Ta, Zr, REE, Hf, Th and U, with low concentration of Be, V, Co, Ni, Cu, Ge, Mo, Cd, Cs, Ba, Tl, Pb and Bi. The concentrations of Ca, Mg and K in Beipiao coal are higher than those in Jianxin coal and Qiaotou coal, while Fe, S and Ti in Beipiao coal are lower than those in Jianxin coal and Qiaotou coal. The proximate analysis of coal samples was carried out, which indicated that Beipiao coal was medium- to high- ash (5.92-60.68%) with low sulphur coal, and Jianxin coal and Qiaotou coal was medium to high ash (8.85-46.33%) with high sulphur. The reflectivity was measured, which explained that Beipiao coal belonged to high volatile bituminous coal, Jianxin coal was low volatile bituminous coal and Qiaotou coal was low volatile anthracite. Quantitative maceral analyses were studied. The characteristics of rare earth elements (REE) were investigated, which showed that the total contents of REE were higher than that of the world's average content. With the increase of coal's metamorphic grade, the total contents of REE decreased from 98.5 X 10"6 of Beipiao coal to 94.2 X 10"6 of Jianxin coal, and to 75.9 X 10"6 of Qiaotou coal, and 5Eu reduced which indicated that the element Eu depleted. The characteristics of REE was controlled by the metamorphic grade of coal. And REE were mainly absorbed in clay minerals in Beipiao coal samples, while in Jianxin and Qiaotou coal mines, REE were primarily related to clay mineral and pyrite. The variation of trace elements in vertical direction of coal seams was studied, and the results showed that different trace elements differed greatly. The correlation between trace elements and ash were determined. Four major trace elements (aluminium-silicates, sulphide, carbonate and phosphate) accounted for the occurrence and distribution of most elements studied were determined. Coal samples were separated by density fraction, which showed that Cr, Cu, Mo and Pb were closely related to inorganic matters mainly distributed in P >2.6 and dropped remarkably in the density fractions P <2.3 . The occurrences of Co, Cr, Ni, As, Se, Mo, U were studied directly and quantitatively using sequential chemical extract with six steps, which showed that Co. Ni, Mo and U were mainly in the form of mineral, and As, Se chiefly in the form of organic state, while Cr mostly in the form of organic state and mineral. Major mineral phases presented in the Beipiao coal were Kaolinite, illite, quartz, calcite, and small amount of siderite, barite. While major mineral phases in Jianxin and Qiaotou coal were pyrite, kaolinite, and small amount of marcasite, rutile, sphalerite. This is the first time that the chromite in the coal was discovered in China, which indicates that Cr occurrence appeared in the form of chromite. The ratio of Sr/Ba, Sr/Ca and V/Ni in Beipiao coal mine under inland limnetic is smaller than that of in Jianxin and Qiaotou coal mines under paralic swamp. The ratio of K/Na and Th/U of Beipiao coal mine is higher than that of Jianxin and Qiaotou coal mine, which proved that Beipiao coal was not affected by sea water and Jianxin and Qiaotou coal were affected by sea water. Trace elements such as Cr, Ni, Mo in minerals were analyzed by SEM-EDS. The factors controlling the enrichment of trace elements can be divided into syngenetic stage factors and epigenetic stage factors.

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海绵钛是钛工业的基础原材料。近年来国内海绵钛产业发展迅速,到2007年其产量已达到两万多吨。海绵钛生产产生大量的废渣、废气、废液等污染物质,对环境造成严重污染,是制约海绵钛产业发展的瓶颈。虽然国家早就将海绵钛生产的环境污染治理问题列为国家重大攻关课题,但长期以来却未从根本上得到很好的解决。本论文以海绵钛生产中铜丝除钒工艺产生的废物为对象,对其中的物质组成及其来源进行了分析,探索对该废物处置与综合回收技术。 除钒杂质是四氯化钛精制作业中极为重要的环节,铜丝除钒是国内采用的主要工艺技术,其产生的废物中含有铜、钒等有用资源。本文首先对海绵钛生产中四氯化钛精制环节铜丝除钒工艺产生的废物的物质组成进行研究,在确定其主要成分是含铜、钒的化合物基础上,设计了综合回收铜、钒等有用资源的技术方案——采用氢氧化钠进行碱处理形成铜钛沉淀物和含钒碱溶液;铜钛沉淀物用硫酸浸出得到硫酸铜溶液和钛沉淀物;硫酸铜溶液进一步电解得到电解铜;含钒碱溶液采用盐酸处理沉淀钒,再经焙烧得到五氧化二钒。在研究过程中主要采用环境矿物学的研究方法,利用化学分析、X射线衍射分析、扫描电镜观察等手段,查明该废物及回收过程产物的特点。 本文通过实验研究,得到以下主要结论: 1.海绵钛生产中铜丝除钒工艺产生的废物主要是水洗池废液,约占90%以上;水洗池废液中铜、钒的浓度很高,分别是5.4g/L、3.6g/L。水洗池沉淀物中的铜、钒主要是以(Cu0.95V2O5)CuO,Ni2V2O7的结晶态形式存在。 2.在废物的化学分析结果和X射线衍射分析结果的基础上,设计了对废物综合回收电解铜、五氧化二钒等资源的技术方案。该回收技术路线下电解铜的初步回收率可达97%,钒的一次回收率约为78%。 3.对回收过程中的各阶段产物进行了化学分析、物相分析和微观形貌观察,研究结果表明铜、钒、钛等资源得到了较好有分离和回收。

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本文以研究硅酸盐细菌解钾作用为目的,介绍了微生物矿物学研究与应用概况、微生物与矿物的相互作用、土壤中钾的利用、土壤钾的主要状态及其相互转化,作者用矿物学与微生物学相结合的方法,分析了几种典型土壤的含钾矿物类型、试验用矿物材料的矿物学特征,细菌-矿物复合体的形成与特性,以及硅酸盐细菌GY92菌株的生物学特性,借助X-射线衍射、电子显微镜观察及化学分析手段,探讨了硅酸盐细菌GY92菌株对钾长石、伊利石的解钾作用机理等问题。全文主要内容包括:1.讨论微生物与矿物之间的关系;简述微生物矿物学的研究内容及发展概况,介绍有关微生物矿物学的部分应用成果;2.利用X-射线衍射手段分析几种典型土壤的含钾矿物类型及含量,并对所选矿物试样的矿物学特征进行了分析;3.采用微生物学试验方法研究硅酸盐细菌GY92菌株的生物学特性以及细菌-矿物复合体的形成及特性,通过这项研究为细菌对矿物的解钾作用分析选定和设计了恰当的实验手段及分析方法;4.采用高分辨电子显微镜(配备能谱仪)观察GY92菌株对钾长石,伊利石试样表面的溶蚀作用,并用X-射线衍射分析以及化学分析手段检测GY92菌株对具不同晶体结构矿物的作用效果;5.作者在附件1中采用GY92菌剂进行了初步的田间对比实验,在附件2中研究了GY92菌株产生的结瘤因子类似物。本项研究所取得的主要成果和认识如下:1.选择土壤中常见的矿物钾长石和伊利石作为实验对象,采用矿物学与微生物学相结合的手段来研究硅酸盐细菌的解钾作用机理问题,这种思路和所选用的研究方法在目前尚未见报道,作者在该项研究中的思路和所选用的研究方法对一些涉及有关细菌与矿物相互作用等问题(如细菌冶金等)的解决具有借鉴意义;2.提出细菌-矿物复合体的概念,并证明该复合体对无机离子及有机酸具有较强的吸附作用,从而为解释硅酸盐细菌对矿物的破坏作用奠定了基础;3.作者在该项研究中设计了一种分析方法,即硅酸盐细菌解钾后,如何处理培养液以便正确测定其中钾离子的浓度;4.采用高分辨电子显微镜(配备能谱仪)首次观察到细菌对矿物试样表面的溶蚀作用,用X-射线衍射分析以及化学分析手段检测GY92菌株对具不同晶体结构矿物的作用效果,并提出硅酸盐细菌对具不同晶体结构的矿物表现出作用强弱或快慢的明显差异上;5.提出硅酸盐细菌对含钾硅酸盐矿物解钾作用的综合效应的看法,从而从微生物矿物学的角度解释了硅酸盐细菌的解钾作用问题;6.作者以初步的田间对比证实GY92菌剂对农作物生长的有益作用(见附件1),并得出GY92菌株可产生结瘤因子类似物的证据(见附件2)。显然,本文的结论为硅酸盐细菌菌剂在农业生产上的利用以及硅酸盐细菌与其他有益微生物混和制成复合生物肥料的使用提供了理论依据。

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在地球的环境界面上,发生着重要的物理、化学和生物学反应,进行着频繁的物质交换和输送,研究和认识环境界面的地球化学过程对揭示环境演化,评价环境质量,认识成矿机理具有重要意义[万国江,1988]化学风化是元素表生地球化学循环的重要环节,是地表碉石(浮土)-水界面间的物质交换过程,其中大气成份和植物微生物代谢产物作为活化剂。化学风化的研究历史大致分为三个阶段:定性描述阶段、化学风化速度定量测定阶段、化学风化的环境生态效应研究阶段。化学风化的动力学理论经过了扩散作用理论、表面反应理论、表面络合反应理论三个发展阶段。化学同化动力学理论及其生态效应方面的研究存在的主工问题是:矿物溶解速度是由表面反应控制的,土壤具有特殊的表面性质,但目前还没有土壤化学同化动力学的实验数据。溶解铝主要来自土壤活性铝,但土壤铝的溶解机理还不清楚;仅根据化学平衡计算就认为Al~(3+)浓度是由矿物溶解平衡控制的,这很不可靠;因为土壤孔隙水的酸度控制矿物的溶解平衡,而土壤中Al~(3+)的水解制约着土壤孔隙水的酸度。孤立地研究养分的释放和流失是不完深善的,需要建立养分循环的动力学模型。黄壤是贵州分布最广的一种土壤。贵州存在着环境酸化、土壤缺钾和“石山”化等一系列生态环境问题。黔中是一个较强的酸雨区,区内降水pH值位于3.5-4.2之间;黄壤酸度高,缓冲能力弱。黄壤中活性铝浓度高,但国内没有进行黄壤中铝的淋溶和毒性的研究。黄壤是中国最贫钾的土壤之一,但缺钾的原因和发展趋势还不清楚。本文的目的是完善土壤化学风化动力学理论、阐明环境中铝的转化机理、建立钾素循环的动力学模型。同时,预测环境酸化趋势、评价土壤钾素供给状况和铝的毒性,讨论关于贵州环境酸化、土壤缺钾和“石山”化等环境生态问题的对策。作者在红枫湖汇水区采集土壤、土壤孔隙水和河水样品。土壤孔隙水用经改进的离心法提取;用化学浸提法测定土壤中铝的形态;完成了河水、土壤孔隙水的水化学全分析、土壤化学性质的测定、土壤的化学全分析和X射线衍射分析,湖水水化学全分析数据由导师提供。作者完成了土壤淋溶实验的研究,测定了淋溶前土壤样品的化学质和化学组成,测定了淋溶液的pH、Ca~(2+)、Mg~(2+)、K~+、Na~+溶解硅和单体铝。通过土壤、土壤孔隙水、湖水的化学年组成,研究土壤的化学风化动力学;通过土壤、土壤孔隙水中铝的形态分布,研究环境中铝的迁移转化机理;根据河水中钾的含量,研究土壤钾素的地球化学循环;通过土壤淋溶实验研究土壤化学风化、土壤铝淋溶、钾素循环的动力学过程。综合现场取样和淋溶实验两方面的研究成果,获得以下几点认识:1、红枫湖汇水区黄壤的化学风化处于高岭石化阶段,酸沉降增大化学风化速度,土壤化学风化符合硅酸盐矿物溶解的表面反应理论。2、实验证实了Johnson (1981)提出的土壤缓冲机制,同时发现弱酸性和中性土壤在淋溶过程中吸附H~+。3、黄壤中铝的移动性与土壤酸度和有机质含量有关,溶解铝在土壤A-B、B-C界面发生沉淀。4、实验证实铝的溶解由三水铝石溶解反应控制,同时发现溶解铝浓度由H~+供给量和盐基离子释放量控制。5、建立钾素循环的动力学模型:EXCH. K=Fw-Fd-Fa利用河水中K~+浓度计算土壤钾素的化学侵蚀速率,可以预测土壤缺钾的趋势。6、实验发现土壤钾素的化学侵蚀过程由离子交换反应控制,钾素侵蚀速率与径流强度、土壤酸度和酸沉降有关。7、酸沉降加剧黄壤酸化和缺钾的趋势,加重黄壤中铝的毒性,需要控制酸沉降通量,使雨水pH值大于4.5。

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碳硅钙石—Ca_7[Si_6O_(18)] [CO_3]·2H_2O是钙的碳酸盐硅酸盐矿物的第三个成员(Pluth and Smith, 1973)。前人曾做过某些碳硅钙石的一般矿物学研究(McConnell, 1955; Murdoch, 1955和曹正民等,1987)。Pluth和Smith (1973)利用X射线四园衍射仪进行结构测定,但未能确定其空间群,给出的结果是I2/m或Im。与此相关,他们未能确定该矿物结构中CO_3的有序或无序;对Ca的配位亦不明了。另外,前人对Ca的碳酸盐硅酸盐矿物未作系统比较。1972年在安徽省濉溪县邹楼铁矿床的钻钆岩芯中也发现了碳硅钙石。作者对该地碳硅钙石样品进行了矿物学、晶体结构和晶体化学研究。作者对采自安徽的碳硅钙品进行了一系列矿物学研究后发现,本文碳硅钙石的一般矿物学特征和前人研究结果基本相同。这说明:(1)本文样品确为碳硅钙石;(2)不同产地和产状的碳硅钙石的矿物学特征相同,由此进一步反映该矿物具有极苛刻的生成条件。作者发现前人对碳硅钙石X射线粉晶衍射线条的指标化有不少错误或不足,并予以纠正。通过晶体结构测定与修正,作用确认碳硅钙石的空间群应为Cm。结构中CO_3有序。它属于等腰三角形几何构型;并呈“受压”迹象。该结构中SiO_4四面体连成稳定的Si_6O_(18)六元环。碳硅钙石结构中水以结晶小的形式存在。该结构中存在氢键。该结构中共有四种Ca的配位多面体;Cal的配位数为8,Ca2, Ca3和Ca4配位数为6。Ca-0多面体相互以复杂的共棱方式连接成层。层间夹有CO_3, Si_6O_(18)和H_2O。Ca-0多面体畸变程度不同。碳硅钙石的晶体化学式应表示为Ca~([8])Ca~([6])_6[Si~([4])_6O_(18)] [C~([3])O_3]·2H_2O。作者发现,可以用配位中心原子(或离子)的键价和讨论配位多面体的结构畸变;并证明对于中心原子(或离子)、配位原子(或离子)、配位数及R(平均键长)均相同的几个配位多面体,畸变程度越强,中心原子(或离子)的键价和越大。此外,作者认识到,离子键和共价键的判别在键价和上也有所体现。根据晶体结构信息,作者对碳硅钙石的某些矿物学特征进行了满意的解释,从而使两者得到相互印证。通过认真全面的比较,作者发现碳硅钙石及其类似古物——Ca的碳酸盐硅酸盐矿物是复杂多样的。除去具有相同或相近的元素组成和地质产状外,它们几乎不再有共同点。碳硅钙石均产自火成岩和沉积岩的接触带。它的结晶温压范围是非常狭窄的。这也正是碳硅钙石等矿物在自然界比较罕见的重要原因。本文碳硅钙石结晶于较晚期的低温热液阶段;并且直接结晶于溶液环境。

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Effects of various kinds of additives as well as aging of the catalyst on the polymerization of styrene catalyzed by TiCl4/MgCl2-AlEt3 system have been studied. Experiments show that in toluene the isotacticity of polystyrene can be up to 83% for aged catalyst, whereas when the catalyst is not aged. non-stereospecific polymer is the main product. When PCl3 is used as an additive, the catalyst system gives high activity and isotacticity. The use of a mixture of AlEt3/H2O (1: 1 mole ratio) as a cocatalyst is also efficient. The catalyst [TiCl4-PCl3/MgCl2-AlEt3/H2O] displays high activity and product isotacticity (94%) with an average molecular weight up to 2 X 10(-6). When Co(acac)(3) is added to to [TiCl4/MgCl2-AlEt3] catalyst after it was aged, the isotacticity can be up to 97%. (C) 2001 Elsevier Science Ltd. All rights reserved.