雷州半岛硅藻土中的硅藻及其化学成分   总被引：4，自引：5，他引：4  

冯璜  张惠芬 《矿物学报》1995,15(1):29-35,T002

本文论述雷州半岛各硅藻土矿床中的硅藻形态和种属。九斗洋和田洋钻孔样品中硅藻种属随深度而变化，由直链藻到了冠盘藻，直到小环藻。总结了对不同种属硅藻的硅质硬过峭同部位的Ｘ射线能谱成分分析和研究结果。  相似文献   

地球化学模拟及其在水文地质中的应用   总被引：10，自引：1，他引：10  

文冬光  沈照理 《地质科技情报》1995,14(1):99-104

从正向地球化学模拟、反向地球化学模拟和水文地球化学模拟三方面系统概述了地球化学模拟的研究进展；结合笔者近年来的科研实践，对其在水文地质中的应用作了介绍，并着重讨论了地下水化学组分存在形式、矿物饱和指数的计算、水化学组分测量及地下水地球化学演化等方面的应用；最后，指出了这一领域中当前存在的问题和今后的研究方向。  相似文献   

南极陨石研究的启示Ⅴ:南极铁陨石的化学组成及其分类          下载免费PDF全文

王道德  陈永亨 《极地研究》1995,7(1):20-27

报道了５２个南极铁陨石的１３个元素的浓度，并根据其构造和Ｇａ，Ｇｅ，Ｎｉ，Ｉｒ及其它微量元素的含量进行了分类，５２个铁陨石由１６个ＩＡＢ，１２个ＩＡＢ，１个ＩＥ，３个ＩＩＡＢ，１个ＩＩＣＤ，１个ＩＶＡ及１８个未分群的化学群组成。ＩＡＢ，ＩＩＣＤ及ＩＥ为非岩浆成因的铁陨石群，它们是由球粒陨石质母体近表面区冲击产生单独的熔体池形成的，ＩＡＢ，ＩＩＡＢ及ＩＶＡ显示金属岩浆分离结晶作用的特征，为岩浆成因的铁陨石。岩浆群铁陨石元素－Ｎｉ的斜率一般比非岩浆群高。有意思的是在南极回收的５２个铁陨石中，相对于非南极铁陨石ＩＡＢ和未分群的铁陨石丰度较高（分别为２７．８％和４７．２％），而ＩＩＡＢ群的丰度较低（５．８％），它们含有以前未采到样品的母体形成区域、质量、冲击碰撞频率的信息。  相似文献   

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 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   

Mapping multiple tree species classes using a hierarchical procedure with optimized node variables and thresholds based on high spatial resolution satellite data     

Yaoliang Chen  Shuai Zhao  Zhuli Xie  Erxue Chen 《地理信息系统科学与遥感》2020,57(4):526-542

ABSTRACT

Tree species distribution mapping using remotely sensed data has long been an important research area. However, previous studies have rarely established a comprehensive and efficient classification procedure to obtain an accurate result. This study proposes a hierarchical classification procedure with optimized node variables and thresholds to classify tree species based on high spatial resolution satellite imagery. A classification tree structure consisting of parent and leaf nodes was designed based on user experience and visual interpretation. Spectral, textural, and topographic variables were extracted based on pre-segmented images. The random forest algorithm was used to select variables by ranking the impact of all variables. An iterating approach was used to optimize variables and thresholds in each loop by comprehensively considering the test accuracy and selected variables. The threshold range for each selected variable was determined by a statistical method considering the mean and standard deviation for two subnode types at each parent node. Classification of tree species was implemented using the optimized variables and thresholds. The results show that (1) the proposed procedure can accurately map the tree species distribution, with an overall accuracy of over 86% for both training and test stages; (2) critical variables for each class can be identified using this proposed procedure, and optimal variables of most tree plantation nodes are spectra related; (3) the overall forest classification accuracy using the proposed method is more accurate than that using the random forest (RF) and classification and regression tree (CART). The proposed approach provides results with 3.21% and 7.56% higher overall land cover classification accuracy and 4.68% and 10.28% higher overall forest classification accuracy than RF and CART, respectively.  相似文献   

Field observations on the production of rainbow trout(Oncorhynchus mykiss) under high concentrations of water-borne iron     

W. Steffens  Th. Mattheis  M. Riedel 《Aquatic Sciences - Research Across Boundaries》1993,55(3):173-178

Effluents from brown coal mines are frequently rich in iron, the water being red-brown in colour and turbid. For several years a fish farm in the Lusatia (Brandenburg, Germany) has used such mine effluents for rearing rainbow trout. The total iron content of this water varies between 5 and 10 mg/l with pH ranging from 6.7 to 7.4. Water turbidity is high with a transparency of 10 to 40 cm at the most due to the substantial ferric hydroxide concentrations. Until 1989 trout have been reared in net cages within concrete settling basins destined for settling the ferric hydroxide mud. The cages were stocked with fingerlings in autumn, reaching portion size in the spring of the following year. Specific growth rate was 0.98% per day, comparable to that of trout in another farm unpolluted by iron but stocked at higher densities. The results show that fingerling rainbow trout may live in water containing more than 5 mg/l total iron but in the absence of Fe²⁺. These concentrations of water-borne iron seem to have only a limited detrimental effect on fish growth and feed conversion and do not prevent trout culture in principle.  相似文献   

缅甸铂族金属砂矿中的矿物种类   总被引：1，自引：0，他引：1  

赵怀志  陈立新 《矿物学报》1994,14(3):285-291,T001

采用电子探针分析（ＥＰＭＡ），对缅甸铂族金属砂矿中的矿物种类进行了研究。物质组成研究查明：主要组合矿物是Ｐｔ、Ｉｒ、Ｏｓ、Ｒｕ的自然元素和金属互化物。主要矿物是自然铂矿、铁铂合金、钌铱锇矿、等轴锇铱矿和铱锇矿。次要及稀有矿物是铂族金属的硫化物、砷化物、包括（Ｒｈ、Ｐｄ、Ｐｔ）２Ａｓ和（Ｒｈ、Ｐｄ、Ｐｔ、Ｎｉ）２Ａｓ两种陌生矿物、锑化物，以及含铂族元素的Ｆｅ、Ｎｉ、Ｃｕ硫化物。  相似文献   

安徽庐江龙桥铁矿含矿地层的古地磁学研究          下载免费PDF全文

阎桂林  魏燕平 《地球科学》1994,19(5):695-700

通过对安徽庐江龙桥铁矿ＺＫ１００４孔（深６１７ｍ）１３２个古地磁标本的研究，认为该矿区赋矿地层的时代应属晚侏罗世（１３６－１４７Ｍａ）；其上覆火山岩地层应旭属下白垩统；将龙门院组、砖桥组划归下白垩统较为合理。  相似文献   

长江武汉江段水体中稀土元素的含量和形态   总被引：8，自引：0，他引：8  

王立军  李岫霞 《地理学报》1994,49(4):353-362

本文采用中子活化分析技术同步研究了稀土元素在长江武汉江段水－悬浮物－沉积物中的地理含量分布及其赋存形态。结果表明，稀土元素在河水中溶解态含量极微，而悬浮态含量较高变幅较大。沉积物与悬浮物中稀土元素含量相近，其含量高低与粒级大小呈负相关，与矿物组成密切相关；稀土元素分布模式均为轻稀土富集、Ｅｕ亏损型。各元素赋存形态均以结晶态为主，各形态所占比例的排序为结晶态≥有机硫化物态＞铁锰氧化物态＞碳酸盐态≥可交换态。各稀土元素相对比较，５种形态的分配比例有一定差异，中稀土Ｅｕ、Ｓｍ、Ｔｂ较轻，重稀土的结晶态所占比例低，而其它形态则相反。  相似文献   

Zur Systematik der Kohlenstoff-Schwefel-Eisen-Verhältnisse in Auftriebssedimenten     

K. -C. Emeis  J. W. Morse 《International Journal of Earth Sciences》1993,82(4):604-618

Abundances of organic carbon, sulfur, and reactive iron in sediments of three upwelling environments (Peru, Oman and Benguela) suggest that organic carbon/reduced sulfur ratios (C/S-ratios) in this category of marine sediments deviate considerably from previously established empirical ratios in normal marine sediments. To clarify the discrepancies, we investigated those components of the diagenetic system that limit the formation of pyrite: sulfate concentrations and reduction rates in pore waters, availability of reactive iron, and the quantity and quality of organic matter. All three limitations are evident in our sample pools. The results suggest that C/S-ratios in recent and fossil marine sediments rich in organic matter may be unsuitable as paleoenvironmental indicators.

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