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  本文關(guān)鍵詞：水體垂向擾動條件下溶質(zhì)在沉積介質(zhì)中的遷移研究　出處：《清華大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 垂向擾動 紊動壓強 對流遷移 自由擴散 非均勻結(jié)構(gòu)

【摘要】：上覆水體的擾動對海洋、河流、湖泊等水體沉積物中物質(zhì)的再懸浮和釋放已逐漸受到全球?qū)W者的關(guān)注。這種在水動力條件下導(dǎo)致的物質(zhì)的遷移和再懸浮過程,尤其是污染物質(zhì)的釋放過程嚴(yán)重的影響著水體的環(huán)境和生態(tài)平衡。為了研究在上覆水體擾動條件下物質(zhì)在沉積介質(zhì)中的遷移,本實驗建立了簡單的沉積物再懸浮發(fā)生裝置,并分別利用不同粒徑大小的沙粒作為均質(zhì)沉積物,同時利用500μg·cm-3的溶解性羅丹明B作為示蹤劑,觀測研究在垂向紊流擾動條件下溶質(zhì)在不同沉積介質(zhì)中的遷移情況。實驗表明,在均勻沉積介質(zhì)中,水流的垂向擾動主要影響溶質(zhì)的垂向遷移,而溶質(zhì)的水平對流遷移十分微弱。在200 r·min-1的擾動強度下,在平均粒徑為71μm介質(zhì)中,溶質(zhì)幾乎不發(fā)生對流遷移現(xiàn)象,以自由擴散遷移為主,且擴散的強度與埋深沒有直接關(guān)系;而該擾動強度對平均粒徑為154μm,311μm,503μm和646μm均勻沉積介質(zhì)的擾動影響深度分別達(dá)到了7cm,10cm,12cm和13cm;在各均勻介質(zhì)中最大遷移速率分別達(dá)到了0.8 mm·h-1、1.8 mm·h-1、2.9 mm·h-1和4.9 mm·h-1,且隨著埋深的加深,物質(zhì)前遷移減弱。而在非均勻介質(zhì)中,上覆水體的擾動將在非均勻介質(zhì)中產(chǎn)生的橫向孔隙水紊動壓強增大,從而導(dǎo)致溶質(zhì)隨著水流發(fā)生跨介質(zhì)的橫向?qū)α鬟w移,且一定范圍內(nèi)隨著擾動的增強和顆粒粒徑的增大,溶質(zhì)的這種橫向?qū)α鬟w移也相應(yīng)增強。當(dāng)擾動強度達(dá)到300 r·min-1以上時,沉積層表層顆粒已發(fā)生了大量再懸浮-再沉淀現(xiàn)象,破壞了表層沉積層結(jié)構(gòu)。研究還發(fā)現(xiàn)非均勻結(jié)構(gòu)將會增大溶質(zhì)在介質(zhì)中的垂向遷移以及同一擾動強度對介質(zhì)的影響深度,如200r·min-1的擾動強度對646μm均勻沉積介質(zhì)影響深度為13cm,而對其各類非均勻結(jié)構(gòu)的影響深度達(dá)到了15cm~16cm;并且對于同一種沉積介質(zhì),不同的非均勻組合對溶質(zhì)遷移的影響也不同。同時,研究還表明,不同的沉積介質(zhì)間存在著一個最利于溶質(zhì)遷移的結(jié)構(gòu)組合,在本實驗組中,646μm介質(zhì)與311μm介質(zhì)構(gòu)成的非均勻結(jié)構(gòu)在200r·min-1的擾動強度下最利于物質(zhì)的遷移。另外,實驗發(fā)現(xiàn)在非均質(zhì)邊界處,溶質(zhì)在71μm介質(zhì)中的擴散遷移大大增強,其最大擴散直徑增量幾乎是其它各點的1.5倍~2倍,說明擾動條件下非均勻結(jié)構(gòu)對溶質(zhì)的擴散遷移也有明顯的增強效果。由于自然條件下水動力條件十分復(fù)雜,不同的擾動環(huán)境對物質(zhì)的遷移影響也存在著較大的差異,因此該論文得出的結(jié)論適用于水體的垂向擾動。
[Abstract]:The disturbance of overlying water has gradually attracted the attention of global scholars for the resuspension and release of material in marine, river, lake and other water sediments. The migration and resuspension of substances, especially the release of pollutants, seriously affect the environment and ecological balance of water under hydrodynamic conditions. In order to study the disturbance transfer conditions in sedimentary material medium in overlying water, this experiment established a simple sediment resuspension generator, and then different particle size of sand as homogeneous sediments, while using 500 g cm-3 dissolved Luo Danming B as tracer, observation and study of disturbance migration conditions the solute in different deposition medium to turbulent flow in the vertical. The experimental results show that the vertical migration of the solute is mainly influenced by the vertical disturbance of the flow in the homogeneous sedimentary medium, while the horizontal convection migration of the solute is very weak. In the perturbation strength 200 r min-1, the average particle size of 71 m in the medium, there is almost no solute convection phenomenon, migration dominated by free diffusion, and the diffusion of the strength and depth of no direct relationship; and the disturbance intensity on the average particle size of 154 m, 311 m, influence the depth of disturbance 503 m and 646 m respectively, the uniform deposition of medium 7cm, 10cm, 12cm and 13cm; in the homogeneous medium maximum migration rate reached 0.8 mm - H-1, mm - 1.8 H-1, 2.9 mm H-1 and 4.9 mm H-1, and with the depth of the material before deepened. Migration weakened. While in non homogeneous medium, transverse pore water turbulence disturbance of overlying water will result in inhomogeneous medium dynamic pressure increases, which leads to the solute water flow with transverse convection cross media migration, and within a certain range with the increasing of the size of the particle and enhance the disturbance, the migration of the solute is transverse convection the corresponding enhancement. When the intensity of the disturbance reaches more than 300 R. Min-1, a large number of re - suspension and re precipitation phenomena have occurred in the surface layer of the sedimentary layer, which destroys the structure of the surface layer. The study also found that non uniform structure will increase the solute in the medium vertical migration and the influence of disturbance intensity on the same medium depth, such as disturbance intensity of 200R - 646 m min-1 on the uniform deposition medium influence depth is 13cm, and the influence of various kinds of non uniform structure depth reached 15cm~16cm; and for the same the sedimentary medium, different non uniform combination effects on solute migration are different. Meanwhile, the study also shows that there is a structural combination that is most conducive to solute transport among different sedimentary media. In this experimental group, the non-uniform structure composed of 646 mu m medium and 311 m medium is most conducive to the migration of matter under the intensity of 200R min-1. In addition, it is found that the diffusion and transport of solute in the medium of 71 M can be greatly enhanced at the heterogeneous boundary. The maximum diffusion diameter increment is almost 1.5 times ~2 times of the other points, indicating that the heterogeneous structure has obvious enhancement effect on the solute diffusion and migration under the condition of disturbance. Because of the complexity of hydrodynamic conditions under natural conditions, the influence of different disturbance environments on material migration is also quite different. Therefore, the conclusions drawn in this paper are applicable to vertical disturbance of water bodies.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：X52

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本文編號：1346256