【摘要】：土壤水分入滲是地球水循環(huán)中的一個(gè)重要環(huán)節(jié),它不僅直接影響土壤水的存儲(chǔ)和地表徑流的形成,也間接影響降水的資源化利用、土壤侵蝕和農(nóng)田面源污染的發(fā)生,因而引起農(nóng)業(yè)和環(huán)境科學(xué)研究者的廣泛關(guān)注。土壤水分入滲是一個(gè)極其復(fù)雜的過程,長期以來土壤學(xué)研究者已經(jīng)對(duì)其進(jìn)行了大量的定量研究,但對(duì)于土壤這個(gè)復(fù)雜系統(tǒng)而言,現(xiàn)有的土壤水分運(yùn)動(dòng)模型對(duì)于定量描述水分運(yùn)動(dòng)過程還有諸多問題,其中主要問題是經(jīng)典理論模型不恰當(dāng)?shù)匕淹寥澜Y(jié)構(gòu)處理為一種剛性結(jié)構(gòu),即假定在水分運(yùn)動(dòng)過程中土壤結(jié)構(gòu)不發(fā)生變化。然而眾所周知,水分進(jìn)入土壤后,土壤結(jié)構(gòu)孔隙都將發(fā)生一系列重要變化,從而極大地影響土壤水入滲和土壤水傳輸。早期研究已經(jīng)發(fā)現(xiàn),同一土壤,當(dāng)電解質(zhì)類型和濃度不同時(shí),土壤水入滲與傳輸表現(xiàn)出完全不同的特征,但其產(chǎn)生原因不清楚;而后來的研究證實(shí),同一土壤,當(dāng)電解質(zhì)類型和濃度不同時(shí),團(tuán)聚體穩(wěn)定性也表現(xiàn)不同。由此可以推斷,電解質(zhì)類型和濃度可能是通過影響土壤結(jié)構(gòu)的孔隙狀況來影響土壤水運(yùn)動(dòng)。近期研究發(fā)現(xiàn),當(dāng)水分進(jìn)入土壤后,土壤溶液中電解質(zhì)被稀釋,改變了顆粒表面附近雙電層結(jié)構(gòu),電場強(qiáng)度迅速增大,靜電排斥力增強(qiáng),土壤結(jié)構(gòu)遭到破壞。因此,用于描述土壤顆粒靜電學(xué)特性的雙電層理論和土壤顆粒相互作用的DLVO(Derjaguin-Landau-Verwey-Overbeek)理論或擴(kuò)展的DLVO理論似乎可以用來描述土壤水的運(yùn)動(dòng)。然而,已有研究發(fā)現(xiàn),當(dāng)水中分別含有KCl和Na Cl時(shí),同一土壤水的運(yùn)動(dòng)速度可以出現(xiàn)數(shù)倍的差,這一現(xiàn)象被稱為離子特異性效應(yīng)(Specific ion effects)或Hofmeister效應(yīng)。有關(guān)離子特異性效應(yīng)研究工作受到包括土壤學(xué)等各領(lǐng)域科學(xué)家的廣泛關(guān)注,新近研究表明電場-量子漲落耦合作用是離子特異性效應(yīng)產(chǎn)生的主要原因。因此,本研究從離子界面反應(yīng)對(duì)顆粒表面雙電層結(jié)構(gòu)和顆粒間相互作用影響出發(fā),首先理論推導(dǎo)得到單一和混合電解質(zhì)體系中帶電顆粒擴(kuò)散雙電層中滑動(dòng)層厚度的計(jì)算關(guān)系表達(dá)式,定量表征顆粒表面雙電層結(jié)構(gòu)變化對(duì)表面電位和靜電斥力的影響;其次利用測定得到土壤表面的Stern電位值對(duì)顆粒間相互作用力進(jìn)行定量計(jì)算,建立土壤水分入滲速率與顆粒間相互作用力定量關(guān)系,分析靜電斥力對(duì)土壤水分入滲的影響;第三,通過土壤水分入滲離子特異性效應(yīng)實(shí)驗(yàn),揭示電場-量子漲落耦合作用中離子Hofmeister能量對(duì)水分入滲的影響;第四,采用動(dòng)態(tài)光散射技術(shù)和工業(yè)CT掃描技術(shù)表征土壤顆粒凝聚/分散過程和孔隙狀況,為進(jìn)一步解釋離子界面反應(yīng)下顆粒間相互作用對(duì)土壤水分入滲的影響提供支撐。通過4個(gè)方面的研究工作,闡明離子界面反應(yīng)下顆粒間相互作用對(duì)界面性質(zhì)及對(duì)土壤水分入滲的影響機(jī)制。本工作取得的主要結(jié)果如下:(1)理論推導(dǎo)得到單一電解質(zhì)體系中膠體顆粒擴(kuò)散雙電層中滑動(dòng)層厚度的計(jì)算關(guān)系表達(dá)式,定量表征了離子界面反應(yīng)對(duì)膠體擴(kuò)散雙電層結(jié)構(gòu)和靜電斥力的影響。根據(jù)單一電解質(zhì)體系中的Gouy-Chapman方程中電位與距離之間關(guān)系的解析解,理論推導(dǎo)得到了單一電解質(zhì)體系中帶電膠體顆粒擴(kuò)散雙電層中滑動(dòng)層厚的計(jì)算關(guān)系式。并且通過實(shí)驗(yàn)測定,然后計(jì)算得到不同電解質(zhì)體系中蒙脫石和紫色土膠體顆粒擴(kuò)散雙電層中滑動(dòng)層厚值,在2:1型電解質(zhì)體系中滑動(dòng)層厚值遠(yuǎn)小于1:1型電解質(zhì)體系�；瑒�(dòng)面離均擴(kuò)散雙電層Stern層較遠(yuǎn),而與雙電層中Gouy層靠近,對(duì)膠體擴(kuò)散雙電層結(jié)構(gòu)有了新的認(rèn)識(shí)�；谶@種新的認(rèn)識(shí)才能對(duì)膠體顆粒表面電位、電場強(qiáng)度和靜電斥力進(jìn)行正確表征,實(shí)驗(yàn)測定了蒙脫石礦物和紫色土膠體顆粒的在單一的Stern電位和zeta電位值,發(fā)現(xiàn)在不同電解質(zhì)體系中前者是后者的3~6倍。采用zeta電位值代替Stern電位值將大大降低膠體顆粒表面電場強(qiáng)度值和顆粒間靜電斥力,紫色土膠體顆粒間電場強(qiáng)度值和靜電排斥力最大分別可降低1~2和4個(gè)數(shù)量級(jí)。因此,對(duì)于滑動(dòng)面在膠體擴(kuò)散雙電層中位置的新認(rèn)識(shí)可以正確表征土壤顆粒表面電位,進(jìn)而才可以正確反映靜電斥力如何影響顆粒間相互作用,最終才能正確揭示顆粒間相互作用對(duì)水分入滲的影響。(2)理論推導(dǎo)得到混合電解質(zhì)體系中膠體顆粒擴(kuò)散雙電層中滑動(dòng)層厚度的計(jì)算關(guān)系表達(dá)式,定量表征了離子界面反應(yīng)對(duì)膠體擴(kuò)散雙電層結(jié)構(gòu)和電學(xué)性質(zhì)的影響。根據(jù)混合電解質(zhì)體系中電位與距離之間關(guān)系的解析解,推導(dǎo)得到混合電解質(zhì)體系中蒙脫石膠體顆粒擴(kuò)散雙電層中滑動(dòng)層厚的計(jì)算關(guān)系式,實(shí)驗(yàn)得到蒙脫石礦物膠體擴(kuò)散雙電層中滑動(dòng)面同樣離雙電層Stern層較遠(yuǎn),而與雙電層中Gouy層靠近,并且2價(jià)陽離子對(duì)其厚度影響遠(yuǎn)大于1價(jià)陽離子。基于膠體擴(kuò)散雙電層結(jié)構(gòu)新的認(rèn)識(shí),對(duì)混合電解質(zhì)體系中膠體顆粒表面電位和電場強(qiáng)度進(jìn)行了表征,得到蒙脫石膠體顆粒的在混合電解質(zhì)體系中的Stern電位絕對(duì)值均遠(yuǎn)大于zeta電位絕對(duì)值,是其值的4~5倍。對(duì)于混合電解質(zhì)體系中膠體雙電層結(jié)構(gòu)的新認(rèn)識(shí),可以正確表征膠體顆粒表面電位值,為進(jìn)一步正確描述混合電解質(zhì)體系中土壤水分入滲過程奠定了理論基礎(chǔ)。(3)離子界面反應(yīng)下顆粒相互作用決定了土壤水分入滲速率。通過對(duì)顆粒間的靜電排斥壓、范德華引力以及表面水合斥力的定量計(jì)算,發(fā)現(xiàn)土壤靜電斥力決定了土壤團(tuán)聚體的狀態(tài)以及土壤水分入滲過程。通過對(duì)膠體擴(kuò)散雙電層新認(rèn)識(shí)正確表征了土壤顆粒表面電位,進(jìn)一步計(jì)算得到顆粒間靜電斥力。顆粒間靜電斥力導(dǎo)致土壤團(tuán)聚體爆裂,釋放的小顆粒不同程度地堵塞土壤孔隙(依賴于靜電斥力的強(qiáng)度),從而降低土壤水分入滲速率。相應(yīng)地,當(dāng)靜電排斥力較弱時(shí),顆粒間表現(xiàn)為凈的吸引力,土壤團(tuán)聚體不發(fā)生爆裂過程,土壤孔隙不被堵塞從而使得土壤水分入滲速率提高。理論計(jì)算表明,兩種離子體系中土壤顆粒間存在一個(gè)凈引力的臨界點(diǎn),MgCl_2體系下在0.005 mol L~(-1)時(shí)出現(xiàn)臨界點(diǎn),Na Cl體系下在0.1 mol L~(-1)時(shí)出現(xiàn)臨界點(diǎn)。此理論計(jì)算得到臨界點(diǎn)出現(xiàn)的濃度與土壤水分入滲實(shí)驗(yàn)觀察的臨界點(diǎn)濃度一致。在Mg~(2+)體系下,這種團(tuán)聚體的膨脹比較弱,而Na~+體系下團(tuán)聚體的膨脹顯著強(qiáng)于Mg~(2+)體系。因此,實(shí)驗(yàn)觀察的土壤水分入滲速率在團(tuán)聚體非爆裂階段仍然表現(xiàn)為Na~+Mg~(2+)。從而我們得出土壤團(tuán)聚體爆裂或者某種程度的團(tuán)聚體膨脹影響了土壤水分入滲。離子-顆粒相互作用決定著土壤電場的強(qiáng)弱,進(jìn)而影響著土壤水分入滲速率的快慢。(4)較系統(tǒng)分析了土壤水分入滲的離子特異性效應(yīng),并闡明了該效應(yīng)產(chǎn)生的機(jī)制——“電場-量子漲落”耦合作用。在Li~+,Na~+,K~+,Cs~+離子體系中土壤水分入滲存在強(qiáng)烈的離子特異性效應(yīng)。對(duì)于同一土壤樣品,Li~+,Na~+,K~+,Cs~+離子體系中不同濃度條件下的水分入滲最大速率分別為:1.8 cm h~(-1),4.3 cm h~(-1),5.2 cm h~(-1),13.0 cm h~(-1)。顆粒間的DLVO合力加上水合斥力共同決定了土壤水分入滲速率;DLVO合力與水合斥力均存在強(qiáng)烈的離子特異性效應(yīng),該效應(yīng)可通過離子的Hofmeister能量給予定量表征,在Li~+,Na~+,K~+及Cs~+體系下Hofmeister能量分別為:0.06Fφ(0),0.18Fφ(0),0.94Fφ(0)和1.86Fφ(0);只有當(dāng)考慮“電場-量子漲落”耦合作用的DLVO合力與水合斥力才能正確解釋土壤水分入滲中的離子特異性效應(yīng)。水合斥力來源于土壤顆粒的表面水合與雙電層中離子水合的共同作用。顆粒的水合斥力受到電解質(zhì)濃度的復(fù)雜影響,雙電層厚度與離子在雙電層中的分布均受到離子Hofmeister能量的強(qiáng)烈影響。(5)采用動(dòng)態(tài)光散射技術(shù)和工業(yè)CT掃描技術(shù)探究了離子界面反應(yīng)下顆粒相互作用對(duì)土壤顆粒凝聚/分散過程和孔隙狀況的影響。通過這兩種分析技術(shù)分別表征了不同價(jià)離子和相同價(jià)離子體系中土壤凝聚/分散過程和孔隙分布狀況。紫色土在Na~+和Mg~(2+)體系下的CCC值(臨界聚沉濃度)分別為91.6 mmol L~(-1)和4.83 mmol L~(-1),表現(xiàn)為Na~+Mg~(2+),在Li~+,Na~+,K~+和Cs~+體系下的CCC值分別為280.9,91.6,47.8和5.2 mmol L~(-1),表現(xiàn)為Li~+Na~+K~+Cs~+。在Mg~(2+)體系土體中1 mm土壤孔隙體積占所有孔隙比例達(dá)到50.4%,1 mm孔隙數(shù)量占1.43%;而在Na~+體系土體中1 mm土壤孔隙體積只占40.2%,1 mm孔隙數(shù)量僅占1.06%;并且,前者1 mm土壤孔隙體積是后者的1.42倍。Li~+,Na~+,K~+和Cs~+體系下的土體中1 mm土壤孔隙體積占所有孔隙比例分別為22.8%,40.2%,56.4%和59.9%,1 mm孔隙數(shù)量所占比例分別為0.32%,1.06%,1.57%,和1.88%。通過進(jìn)一步計(jì)算,可以得到Cs~+體系下土體中1 mm土壤孔隙體積分別為,Li~+,Na~+,K~+體系下的13.7,5.22,2.70倍。通過不同電解質(zhì)體系中的土壤顆粒凝聚/分散過程和孔隙狀況數(shù)據(jù)可以進(jìn)一步解釋離子界面反應(yīng)下顆粒相互作用對(duì)土壤水分入滲影響的內(nèi)在機(jī)制。綜合上述幾個(gè)方面的研究結(jié)果,本研究主要得到如下結(jié)論:1)建立了單一和混合電解質(zhì)體系下帶電膠體擴(kuò)散雙電層中滑動(dòng)面厚度的理論和方法,對(duì)膠體擴(kuò)散雙電層結(jié)構(gòu)有了新的認(rèn)識(shí),并以此確立了須采用Stern電位定量描述顆粒間相互作用才能正確反映其對(duì)土壤水分入滲的影響;2)土壤表面電位值決定著水分入滲速率大小,電解質(zhì)類型和濃度通過調(diào)節(jié)表面電場強(qiáng)度影響顆粒間相互作用決定著土壤顆粒的凝聚/分散過程,改變土壤小顆粒釋放過程,影響土壤孔隙狀況,最終改變土壤水分入滲過程;3)土壤水分入滲過程表現(xiàn)出強(qiáng)烈的離子特異性效應(yīng),通過電場-量子漲落耦合作用中離子Hofmeister能量影響DLVO合力與水合斥力,使土壤結(jié)構(gòu)穩(wěn)定性產(chǎn)生差異,影響土壤孔隙狀況,最終改變土壤水分入滲過程。綜上所述,基于本研究發(fā)現(xiàn)土壤水分入滲過程受土壤顆粒間相互作用控制,這為我們提供了一種可能的內(nèi)部調(diào)控途徑,即通過調(diào)節(jié)土壤顆粒間相互作用來控制土壤水分入滲的快慢。
[Abstract]:Soil water infiltration is an important part of the earth's water cycle. It not only directly affects the storage of soil water and the formation of surface runoff, but also indirectly affects the resource utilization of precipitation, soil erosion and the occurrence of non-point source pollution in farmland. Therefore, it has attracted wide attention of agricultural and environmental scientists. For a long time, soil researchers have done a lot of quantitative research on the complex process. However, there are still many problems in describing the process of soil water movement quantitatively with the existing soil water movement model. The main problem is that the classical theoretical model does not properly treat the soil structure as a kind of soil structure. Rigid structure, i.e. the assumption that soil structure does not change during water movement. However, it is well known that when water enters the soil, a series of important changes will occur in soil structure pores, which greatly affect soil water infiltration and soil water transport. Soil water infiltration and transport exhibit completely different characteristics, but the causes are not clear. Later studies have confirmed that the stability of aggregates varies with the type and concentration of electrolytes in the same soil. Recent studies have found that when water enters the soil, electrolytes in the soil solution are diluted, which changes the structure of the double layer near the surface of the particles. The electric field strength increases rapidly, the electrostatic repulsion force increases, and the soil structure is destroyed. VO (Derjaguin-Landau-Verwey-Overbeek) theory or extended DLVO theory seem to be able to describe the movement of soil water. However, it has been found that when the water contains KCl and Na Cl respectively, the velocity of the same soil water can be several times different. This phenomenon is called ion-specific effects or Hofmeist. Recent studies have shown that the coupling of electric field and quantum fluctuation is the main reason for the ion-specific effect. Therefore, this study focuses on the effects of ion-interface reactions on the structure of electric double layer on the surface of particles and the interaction between particles. Firstly, the formula of calculating the thickness of sliding layer in charged particle diffused double layer in single and mixed electrolyte system was deduced theoretically, which quantitatively characterizes the influence of the structure change of double layer on the surface of particles on the surface potential and electrostatic repulsion force. The relationship between soil water infiltration rate and intergranular interaction force was established by quantitative calculation, and the effect of electrostatic repulsion on soil water infiltration was analyzed. Dynamic light scattering (DLS) and industrial computed tomography (ICT) scans were used to characterize the coagulation/dispersion process and pore size distribution of soil particles, which provided support for further explaining the effect of particle-particle interaction on soil water infiltration under ion-interface reaction. The main results obtained in this work are as follows: (1) The formula for calculating the slip layer thickness in the colloidal diffused double layer in a single electrolyte system is derived theoretically, and the effect of ionic interface reaction on the structure and electrostatic repulsion of the colloidal diffused double layer is quantitatively characterized. Analytical solution of the relationship between potential and distance in Gouy-Chapman equation in the system is deduced theoretically. The formula for calculating the slip layer thickness of charged colloidal particles in a single electrolyte system is deduced theoretically. The slip layer thickness in the 2:1 electrolyte system is much less than that in the 1:1 electrolyte system. The slip surface is far from the Stern layer and near the Gouy layer in the double electrolyte layer. A new understanding of the structure of the colloidal diffusion double electrolyte layer can be obtained based on this new understanding. The Stern potential and zeta potential of montmorillonite minerals and purple soil colloidal particles were measured experimentally. It was found that the former was 3-6 times higher than the latter in different electrolyte systems. Therefore, the new understanding of the location of the sliding surface in the colloid diffusion double layer can correctly characterize the surface potential of soil particles, and then can correctly reflect how the electrostatic repulsion affects the interaction between particles, and finally can correctly reveal. (2) Formulas for calculating the thickness of the sliding layer in the colloidal particle diffusion double layer in the mixed electrolyte system were deduced theoretically, which quantitatively characterize the effect of ionic interface reaction on the structure and electrical properties of the colloidal diffusion double layer. The analytical solution of the relationship is derived and the formula for calculating the slip layer thickness in the diffused double layer of montmorillonite colloidal particles in the mixed electrolyte system is derived. The experimental results show that the slip surface in the diffused double layer of Montmorillonite Mineral colloidal particles is also farther away from the double layer Stern layer, but closer to the Gouy layer in the double layer, and the effect of 2 valent cations on its thickness is great. Based on the new understanding of colloidal diffusion double layer structure, the surface potential and electric field intensity of colloidal particles in the mixed electrolyte system were characterized. It was found that the absolute value of Stern potential of montmorillonite colloidal particles in the mixed electrolyte system was much higher than that of zeta potential, which was 4-5 times of that of the mixed electrolyte system. A new understanding of the structure of the colloidal double layer in the system can correctly characterize the surface potential of colloidal particles and lay a theoretical foundation for further describing the process of soil water infiltration in the mixed electrolyte system. (3) Particle interaction in the ionic interface reaction determines the rate of soil water infiltration. Quantitative calculation of Dehua gravity and surface hydration repulsion showed that soil electrostatic repulsion determined the state of soil aggregates and the infiltration process of soil water. When the electrostatic repulsion force is weak, the net attraction between the particles appears, the soil aggregates do not burst, and the soil pores are not blocked so that the soil water infiltrates into the soil. The theoretical calculation shows that there is a critical point of net gravity between the two ionic systems. The critical point appears at 0.005 mol L~(-1) in MgCl_2 system and at 0.1 mol L~(-1) in Na Cl system. In the Mg~ (2+) system, the swelling of the aggregates is relatively weak, and the swelling of the aggregates in the Na~+ system is significantly stronger than that in the Mg~ (2+) system. Therefore, the experimental observation of soil water infiltration rate in the non-bursting stage of the aggregates still shows Na~+Mg~ (2+). Thus we can conclude that the soil aggregates burst or some degree of aggregate expansion. Ion-particle interaction determines the strength of soil electric field, and then affects the speed of soil water infiltration. (4) The ion-specific effect of soil water infiltration is systematically analyzed, and the mechanism of this effect is clarified - "electric field-quantum fluctuation" coupling effect. For the same soil sample, the maximum infiltration rates of Li~+, Na~+, K~+, and Cs~+ under different concentrations are 1.8 cm h~(-1), 4.3 cm h~(-1), 5.2 cm h~(-1) and 13.0 cm h~(-1), respectively. Soil water infiltration rate; DLVO resultant force and hydraulic repulsion force have strong ion-specific effects, which can be quantitatively characterized by the Hofmeister energy of ions. In Li~+, Na~+, K~+ and Cs~+ systems, the Hofmeister energy is 0.06 F phi (0), 0.18 F phi (0), 0.94 F phi (0) and 1.86 F phi (0), respectively; only when the coupling of "electric field-quantum fluctuation" is considered. Hydration repulsion comes from the interaction between surface hydration of soil particles and ionic hydration in the electric double layer. Hydration repulsion of particles is affected by the complex concentration of electrolyte, and the distribution of the thickness and ions in the electric double layer. (5) Dynamic light scattering (DLS) and industrial computed tomography (ICT) were used to investigate the effects of particle interaction on the coagulation/dispersion process and pore size distribution of soil particles under the ion-interface reaction. The CCC values of purple soils in Na~+ and Mg~ (2+) systems (critical concentration of aggregation) are 91.6 mmol L~(-1) and 4.83 mmol L~(-1), respectively. The CCC values of purple soils in Li~+, Na~+, K~+ and Cs~+ systems are 280.9, 91.6, 47.8 and 5.2 mmol ~(-1), respectively. 1 mm soil pore volume accounted for 50.4% of all pore volume, 1 mm soil pore volume accounted for 1.43%; while 1 mm soil pore volume accounted for only 40.2% in Na~+ system, 1 mm soil pore volume accounted for only 1.06%; and the former 1 mm soil pore volume was 1.42 times of the latter 1.42 times. The void fractions were 22.8%, 40.2%, 56.4% and 59.9% respectively, and the void fractions of 1 mm were 0.32%, 1.06%, 1.57% and 1.88% respectively. The dispersion process and pore size data can further explain the intrinsic mechanism of the effect of particle interaction on soil water infiltration under the ionic interface reaction. Based on the above results, the main conclusions are as follows: 1) The thickness of sliding surface in charged colloidal diffusive double layer with single and mixed electrolyte system is established. The theory and method have a new understanding of the structure of colloid diffusion double layer, and it is established that the interaction between particles must be quantitatively described by Stern potential in order to correctly reflect its effect on soil water infiltration; 2) The value of soil surface potential determines the infiltration rate, and the type and concentration of electrolyte can be regulated by adjusting the surface electric field intensity. Degree affects the aggregation/dispersion process of soil particles, changes the release process of soil particles, affects soil porosity, and ultimately changes the infiltration process of soil water; 3) Soil water infiltration process shows strong ion-specific effect, and ionic Hofmeister energy through the coupling of electric field and quantum fluctuation. Influencing DLVO resultant force and hydraulic repulsive force, making the stability of soil structure different, affecting soil porosity, and ultimately changing soil water infiltration
【學(xué)位授予單位】：西南大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：S152.72
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本文編號(hào)：2204399