The Titanium In Purple Paernt Rocks And Soils

Titanium is the ninth richer element in the earth(Clarke value is 0.57%),and is also the seventh abundanter element which is one of elements that formed minerals in earth crust.The average abundance of titanium is 0.63% in the earth crust As the soil in the world as concerned, the total titanium is about 3.0⁶.0g(TiO₂)·kg^-1and the average of it is 4.6g(TiO₂)·kg^-1, and the content belongs to the midelement level. From the statistic of the present datum, the content of total titanium in soil is from 2.0 to 39.0g(TiO₂)·kg^-1 in our country. In purple parent rocks and soii,the content of titanium is 2.5²0g(TiO₂)·kg^-1,and the average content is 6.7g(TiO₂)·kg^-1, generally speaking,the content is from middle level to high level.As one of the most important elements that formed minerals , titanium exists in all types of rocks in diversified mineral form. The main proterozoic mineral and the submineral of titanium are: ilmentie, brookite, rutile, sphene, unformed leucoxene, anatase and so on.. Furthermore, titanium sometimes integrates with the proterozoic mineral of silicon, iron, and aluminium in igneous rocks, sedimentary rocks and metamorphic rocks,or exists in the crystal lattice of proterozoic and subordinate aluminium silicate clay mineral in the forms of isomorphic-alloneric, or sometimes immerges in varities of feldspar or exist in quartz in the forms of rutile inbreaking substance. It is commonly considered that the content of titanium in igneous rocks is higher than that in sedimentary rocks, thereinto, the content of titanium in basic igneous rocks is higher than that in acid rock and acid igneous rocks, and the content of titanium in river and lake sedimentation rocks or sipping marine sedimentation rocks is higher than that in marine sedfimentation.,Recently, it is considered that titanium belongs to wearkly active elements during surface genesis-transfer-sedimentary cycle of geochemistry ,and the transfer intensity of titanium is fairly weak. So the amount of titanium content is related closely to the titanium content level of soil parentmaterial; Also, titanium will be likely to enrich relatively in soil as soil weathering development degree deepening because of uneasy transfer of titanium; Therefore, titanium is often rich in deeply developed soils. There are many variety of minerals that contains titanium ,the amount of titanium independent minerals found in soils reaches above sixty kinds. But in all kinds of associated minerals that contain titanium in soil, titanium is formed to various aluminium-silicate clay minerals and combined , amorphous oxides, hydrates, hydroxides and so on according to different proportion. As the bond Si—O in silicate clay minerals, Ti—O bond is also comparatively steady, it is taken for that Ti—O intensity is only inferior to that of Al—O, it can reach 1411 1702kcarmol'. Hence , clay minerals which are made up from titanium instead of silicon or aluminium may have some stability.Except for mineral form and amorphism , organic chelated reaction of titanium probably exists in soil. If this reaction exactly exists , there should be complexations or associations of organic titanium and a quantity of titanic ionic compounds in soil . But the form .chemical property .solubility and the chemical process with soil colloid of complexing or ionic compounds are not clearly. These forms of titanium should be most easily extracted from soil by extraction solvent. In other words,they are the parts of titanium that most closely related to vegetation validity.From the view of biology.there is no reliable evidence to prove that titanium is the necessary element for the plant growing at present,but numbers of experiments show that titanium has an obviously promoted effect on some physiological functions of the plants.The content of titanium is obvious difference in kinds of plants,the lower is less than lg(Ti)-kg"', however the higher can reach 100 g(TiO2)-kg''. But it's unclear to the best practical requirement , the form of absorbable titanium from soik the mode of absorption and the conditions of soil of all kinds of plants at present.Compared with other elements, the quantify study of titanium is comparatively difficult. Up to now, there is not any intact method which can quantificately analyse its mineral forms, total content level, soluble titanium content simplely, truly and quickly. Therefore, in the study of the titanium in parents mineral, soil and plants, the research of kinds of extracting quantify method, filter courses of titanium determined the dependability, advance, practicability and the researchful degree. At present, the melted method or hydrofluoric acid decompose method are often used as pretreatment to determine total titanium in soil, and colorimetry is adopted for quantifying the titanium. Extraction of soluble titanium often uses the series of EDTA solution of different chroma, different pH, and the titanium in the extracted liquid adopts chemical colorimetry to complete quantifying too. The mineral forms of titanium in parents rock or soil is very difficult to classify and quantify, some people have used "x diffraction" or "infrared spectrometry" and so on ,but only to cursorily identify and quantify part of both highly content and crystal latticed titanium mineral on the basis of kind of collective methods. So, the research to find a method which can be simple .practical and being able to analyse and determine the various forms of titanium in soil accurately has significant sense tounderstand the titanium deeply.Titanium content level of purple parent rocks and soils is relatively high, for the view of soil genesis classification, the district of Chinese purple parent materials distribution is in red earths and yellow earths biology climate region, purple soil can reserve parent material characteristics mostly for a long time except that development degree of parent materials is greatly deep. Based on the studied results ,it is thought that there are two reasons that purple soils can reserve their lithology soil characters: for one hand , it is because of strong physical weathering process of purple parent materials; for another hand ,it is due to strong resisting chemical weathering capacity of purple parent materials. However, the cause of formation of strong physical wearthering is contributed to: (l)Compose of particles are complicate, and cementation materials are liable to the dissolved erosion of water % heat-, atmosphere and acid-alkali materials, which causes rocks collapse;(2)Inorganic clay minerals type is more complex than other rocks, and the swell and contractibility of different clay minerals are not same, so the swell and contractibility is diverse after heated and wetted, it increases collapse of rocks. (3)Geology construction and lithology structure are intricate, the complex combination of different lithology terrene promotes the formation of complicate terrain and physiognomy in purple rock district, in reverse ,it also accelerates gravity erdsion effect and physical weathering process. But the opinions that the cause of formation of purple parent material and the resisting chemical weathering property of purple soil especially the color characteristics that purple soil inherits continuously from parent material for a long time is still varying, and there is no exact conclusions.As a kind of lithology agrotype ,the remarkable character of purple soil is that it follows the mineral characteristics of parent rock. The characteristics of titanic mineral will certainly be carried into soil with parent rock weathering into soil and follows soil development process.But currently ,the study of purple rock and soil is merely limited on the level of total Ti content. At present, many respects are still unknown ,such as titanic mineral form and content in parent rocks and purple soil, genetic characters, the affection on parent rock and physics- chemistry property, and the significance of taxology and fertility science , especially the contribution to the particularity of purple rock and soil and so on .Therefore .studying the level of Ti content and mineral form in purple rock and soil is significant to northerly find out the mineral speciality Of purple parent rock, to master soil genesis and orderliness of weathering and development of purple soil, and to classify and zone purple soil with accuracy.On the basis of comparison on pretreatmenL extraction, mensuration of total titanium , subcompounds which contain titanium , soluble titanium between parent rocks and soil,at first this paper designs and chooses the method of NaOH melting—diantipyryl methane colorimetry to determine total titanium and the method "(NH4)2SO4—H2SO4 for extracting and diantipyryl methane colorimetry" to determine amorphous TiO2; "O.SmolI/'CNH4)2SO4—O.Smoll/-1H2SO4 extraction.diantipyryl methane colorimetry" to determine soluble titanium ; "0.25% diantipyryl methane—0.25%Vc—lmoM/'HCl direct extraction—colorimetry"to determine chelate titanium. We collect all six main kinds of purple parent rocks samples of different lithology ,as well as different devl eopment degree soil samples, profile samples that were developed from these parent rocks in Chongqing and Sichuan province,and then we determined total titanium , subtitanium compound % soluble titanium-, chelate titanium of those samples by those four methodsand compared the results of determination detailedly by relative comparison methods.Meanwhile ,on the condition of protection with N2, absorption and fixation the experiments in purple soil were done by using Ti3+ and Ti2+ solvent. The results as follows:(1) To determine total content of titanium in purple parents rocks and soils, using "Na2(X)3 melted method" , "NaOH melted method" and "HF-HC1O4(HNO3) assimilation method" for pretreatment can achieve perfect effects respectively; However, the best one to quantify titanium is diantipyryl methane colorimetry, determine sensitivity can reach 0.05 mg-L"1 (Ti), recovery rate is 100.9%. Variation coefficient is between 2.34% and 6.12%. This qualifying method is better than other methods no matter what in sensitivity, exactivity, recurrence and operational simplicity.(2) On the condition of boiling by heated.purple material rocks or soil total amorphous TiO2 can be extracted and determined by using (NH4 ) 2S04+H2S04(strong) for extracting and diantipyryl methane colorimetry. The variation coefficient of determination result that extracts by boiling for fifteen minutes is 2.63-6.2 l%.The amorphous TiO2 content of every tested geological age purple parent rocks determined by using this method is 0.378¹.69 g-kg"1, but the amorphous T1O2 content can reach 2.97 g-kg"1 in different terrane and section of some non-purple parent rocks such as yellow sandstone weathering materials of Ziliujin Lianggaoshan Duan.(3)The total titanium content of tested purple parent material is 3²0 mg-kg"1 (TiC^) , but there are obvious differences among different geological ages purple parent rocks on otal titanium content, the order is Trias Tif>Jurassic J2S>Jurassic Ji₂z>Jurassic J3p>Jurassic J3s>Cretaceous K2J. Moreover, for the same geological age , total titanium contents of shale and mudstone are higher than that of siltstone and sandstone.(4) The content of total titanium of tested purple soil is between 4.17 and lS^g-kg"1 (T1Q2) -The variation trend of total titanium level in the soil developed from different geological age parent material coioncides with the total titanium variation order of parent material .In general condition,the devl eopment degree of soil has no influence onthe content of total titanium in soil. Untill when soil texture is light and deep devleopment,the titanium in soil may cause the titanium content lower in soil surface layer because of transport.(5)According to the relationship between the total content of titanium and amorphous TiO2 in parents rocks(or soils), this paper defines the ratio of the total content of titanium(TiO2) and amorphous TiC>2 in parents rocks or soils as "titanium value", namely : titanium value = total TiO2/amorphous TiO2-The important senses of "titanium value" rest with that it can replace the custom method which use "Si02/(Al203+Fe2O3)" to weigh and describe original weathering degree of purple parents rocks and develop deepness of purple soils. Compared with "SiP2/(Al2O3+Fe2O3)", the advantages of titanium value is :firstly, titanium value can be directly determined in rocks and soil samples , and exacting of colloid is not needed. Above all, it solved the problem that SiO2/(Al2O3+Fe2(>3) can not be directly determined, at the same time, the simplicity and accurateness are the determination of SiO2/(Al2O3+Fe2O3) not to be compared with.Secondly, titanium value possess greater numerical value difference and span, which is convenient to make a much more detailed classification description of purple parents rocks or soil weathering degree. According to the titanium value we determined, compared with the result of colloid SiO2/(Al2O3+Fe2Q3) in the same soil sample, their correlation coefficient is R=0.8615**, reaches highly obvious level. And the soil colloid SiC>2/(Al2O3+Fe2O3) and titanium value were determined at the same time, their correlation coefficient didn't vary greatly, R=0.8757**. (6) Titanium value range of every geological age purple parent rock is 4—12, the order is Trias Tif(11.8-11.9) >JurassicJ2s (8.43-12.5) > Jurassic Jt₂z (8.43-12.5) > Jurassic J3p (4.89-11.8) > Jurassic J3 s(6.48⁸.02)> Cretaceous Kic(4.54⁹.94). According to the relation between titanium value and weathering degree , the order of average original weathering degree of every geological age purple parent rock is Cretaceous Kic> Jurassic J3 s> Jurassic J3 p > Jurassic Ji₂ z > Jurassic J2s> Trias Tif.(7)The relativity between darkness and lightness of purple in parent rocks and the content of Ti exists for sure,according to (China Standard Soil Colour Chart> .total Ti content of parent rock is reverse correlation to "color hue" (RP value) of purple (the smaller the value is ,the more obvious the purple is) and "brightness", but positive correlation to "chroma". Because total Ti content of parent rock is related to lithology, the relativity between Ti and purple is more remarkable in sandstone than that in others.(8) The range of the titanium value in the tested purple soil is 2.5¹2.5.Based on the definition of titanium value, the size of it is negative related to the develop degree of the purple soil, that is to say, while "the titanium value" is high the soil develop degree is simple; whereas, it's deep. According to the range of the titanium value tested from known purple soil, the titanium value can be divided into I -VII grades, correspondingly .there are 7 develop degree levels in purple soil.(9) The existences in purple soil of titanium can be divided into a few forms thereinafter: (1)proterozoic titanium mineral, which mainly include proterozoic composite titanium salt, for example, rutile species, anatase, ilmenite species, contained titanium layer shape aluminium silicate, feldspar species contained titanium; (2) submental contained titanium .main include sub-layer shape aluminium silicate mineral contained titanium, amorphous leucoxene minaral, titanite minaral; (3) hydration titanium oxid and its primary jello,simple titanium salt, as titanium-iron salt,...