基于同步辐射显微CT研究冻融循环对黑土团聚体结构特征的影响
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摘要
在我国东北地区,土壤不同程度的受到季节性冻融的影响。冻融作用会改变土壤微观结构,团聚体作为土壤结构的基本单元,其结构特征的改变反映了冻融作用对土壤微观结构的影响。同步辐射显微CT可以无损获取高分辨率、强对比度的内部结构图像,是研究土壤团聚体三维微结构的有效手段。采集了室内冻融循环试验下不同冻融循环次数的土壤团聚体样品,应用同步辐射显微CT扫描获取了3.25μm分辨率的团聚体内部结构图像,然后应用CT图像处理方法和Image J软件观察并定量分析了团聚体微结构特征。结果表明:随着冻融循环次数的增加,土壤孔隙度不断增大,瘦长型孔隙度占比与>100μm的非毛管孔隙度不断增大;当冻融循环次数达到7次以上,团聚体孔隙连通度随冻融循环次数的增加而变大。冻融循环对黑土团聚体孔隙度、孔隙形状、孔隙分级、连通性等结构特征影响显著。该研究为春季解冻期土壤侵蚀机理的研究及水土流失的防治提供理论依据。
In Northeast China, seasonal freezing and thawing have been shown to cause significant physical changes in soil. The change in soil microstructure might be attributed to the freeze-thaw action during early spring. The freeze-thaw action affects soil microstructure directly by affecting soil aggregate, which is the basic unit of soil structure. Synchrotron-based X-ray micro-computed tomography can nondestructively capture images of the interior structure with high resolution and strong contrast, and therefore, is an excellent tool to investigate the 3-D microstructure of soil aggregates. Samples of soil aggregates were collected from laboratory freeze-thaw tests with different number of freeze-thaw cycles, and the aggregates were scanned with micro-CT at a resolution of 3.25 μm. The microstructure of aggregates was visualized and quantified by the digital image analysis method using Image J software. The results showed that with the increase in number of freeze-thaw cycles, the soil porosity increased, and the proportion of extended pore and pores > 100 μm also increased. When the number of freeze-thaw cycles was >7, the aggregate porosities increased with the increase in number of freeze-thaw cycles. The results showed that the number of freeze-thaw cycles significantly influenced the structural characteristics of black soil aggregates. This study provides a theoretical basis for the study of freeze-thaw erosion and control of soil erosion during thawing in spring.
In Northeast China, seasonal freezing and thawing have been shown to cause significant physical changes in soil. The change in soil microstructure might be attributed to the freeze-thaw action during early spring. The freeze-thaw action affects soil microstructure directly by affecting soil aggregate, which is the basic unit of soil structure. Synchrotron-based X-ray micro-computed tomography can nondestructively capture images of the interior structure with high resolution and strong contrast, and therefore, is an excellent tool to investigate the 3-D microstructure of soil aggregates. Samples of soil aggregates were collected from laboratory freeze-thaw tests with different number of freeze-thaw cycles, and the aggregates were scanned with micro-CT at a resolution of 3.25 μm. The microstructure of aggregates was visualized and quantified by the digital image analysis method using Image J software. The results showed that with the increase in number of freeze-thaw cycles, the soil porosity increased, and the proportion of extended pore and pores > 100 μm also increased. When the number of freeze-thaw cycles was >7, the aggregate porosities increased with the increase in number of freeze-thaw cycles. The results showed that the number of freeze-thaw cycles significantly influenced the structural characteristics of black soil aggregates. This study provides a theoretical basis for the study of freeze-thaw erosion and control of soil erosion during thawing in spring.
引文
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[14] Waddel H.Volume,shape,and roundness of rock particles.The Journal of Geology,1932,40(5):443- 451.
[15] 周虎,彭新华,张中彬,王亮亮,肖体乔,彭冠云.基于同步辐射微CT研究不同利用年限水稻土团聚体微结构特征.农业工程学报,2012,27(12):343- 347.
[16] Ma R M,Cai C F,Li Z X,Wang J G,Xiao T Q,Peng G Y,Yang W.Evaluation of soil aggregate microstructure and stability under wetting and drying cycles in two Ultisols using synchrotron-based X-ray micro-computed tomography.Soil and Tillage Research,2015,149:1- 11.
[17] Dal Ferro N,Delmas P,Duwig C,Simonetti G,Morari F.Coupling X-ray microtomography and mercury intrusion porosimetry to quantify aggregate structures of a cambisol under different fertilisation treatments.Soil and Tillage Research,2012,119:13- 21.
[18] Garbout A,Munkholm L J,Hansen S B.Tillage effects on topsoil structural quality assessed using X-ray CT,soil cores and visual soil evaluation.Soil and Tillage Research,2013,128:104- 109.
[19] Lebron I,Suarez D,Schaap M.Soil pore size and geometry as a result of aggregate-size distribution and chemical composition.Soil Science,2002,167(3):165- 172.
[20] Konrad J M.Physical processes during freeze-thaw cycles in clayey silts.Cold Regions Science and Technology,1989,16(3):291- 303.
[21] 齐吉琳,张建明,朱元林.冻融作用对土结构性影响的土力学意义.岩石力学与工程学报,2004,22(S2):2690- 2694.
[22] 倪万魁,师华强.冻融循环作用对黄土微结构和强度的影响.冰川冻土,2014,36(4):922- 927.
[23] 骆紫藤,牛健植,孟晨,张英虎,杜晓睛,蔺星娜,贾京伟.华北土石山区森林土壤中石砾分布特征对土壤大孔隙及导水性质的影响.水土保持学报,2016,30(3):305- 308,316.
[2] Gong J D,Qi X S,Xie Z K,Wang Y J.Effect of seasonal freezing on soil moisture and its significance for agriculture.Journal of Glaciolgy and Geocryology,1997,19(4):328- 333.
[3] 卢金伟,李占斌.土壤团聚体研究进展.水土保持研究,2002,9(1):81- 85.
[4] 赵冬,许明祥,刘国彬,张蓉蓉,脱登峰.用显微CT研究不同植被恢复模式的土壤团聚体微结构特征.农业工程学报,2016,32(9):123- 129.
[5] Benoit G R.Effect of freeze-thaw cycles on aggregate stability and hydraulic conductivity of three soil aggregate sizes.Soil Science Society of America Journal,1973,37(1):3- 5.
[6] Six J,Bossuyt H,Degryze S,Denef K.A history of research on the link between (micro) aggregates,soil biota,and soil organic matter dynamics.Soil and Tillage Research,2004,79(1):7- 31.
[7] 王恩姮,赵雨森,陈祥伟.典型黑土耕作区土壤结构对季节性冻融的响应.应用生态学报,2010,21(7):1744- 1750.
[8] Li G Y,Fan H M.Effect of freeze-thaw on water stability of aggregates in a black soil of northeast China.Pedosphere,2014,24(2):285- 290.
[9] Dal Ferro N,Charrier P,Morari F.Dual-scale micro-CT assessment of soil structure in a long-term fertilization experiment.Geoderma,2013,204- 205(4/5):84- 93.
[10] San José Martínez F,Martín M A,Caniego F J,Tuller M,Guber A,Pachepsky Y,C.García-Gutiérr C.Multifractal analysis of discretized X-ray CT images for the characterization of soil macropore structures.Geoderma,2010,156(1/2):32- 42.
[11] Zhou H,Peng X,Peth S,Xiao T Q.Effects of vegetation restoration on soil aggregate microstructure quantified with synchrotron-based micro-computed tomography.Soil and Tillage Research,2012,124:17- 23.
[12] 范昊明,张瑞芳,周丽丽,武敏,刘艳华.气候变化对东北黑土冻融作用与冻融侵蚀发生的影响分析.干旱区资源与环境,2009,23(6):48- 53.
[13] Iassonov P,Gebrenegus T,Tuller M.Segmentation of X-ray computed tomography images of porous materials:A crucial step for characterization and quantitative analysis of pore structures.Water Resources Research,2009,45(9):W09415.
[14] Waddel H.Volume,shape,and roundness of rock particles.The Journal of Geology,1932,40(5):443- 451.
[15] 周虎,彭新华,张中彬,王亮亮,肖体乔,彭冠云.基于同步辐射微CT研究不同利用年限水稻土团聚体微结构特征.农业工程学报,2012,27(12):343- 347.
[16] Ma R M,Cai C F,Li Z X,Wang J G,Xiao T Q,Peng G Y,Yang W.Evaluation of soil aggregate microstructure and stability under wetting and drying cycles in two Ultisols using synchrotron-based X-ray micro-computed tomography.Soil and Tillage Research,2015,149:1- 11.
[17] Dal Ferro N,Delmas P,Duwig C,Simonetti G,Morari F.Coupling X-ray microtomography and mercury intrusion porosimetry to quantify aggregate structures of a cambisol under different fertilisation treatments.Soil and Tillage Research,2012,119:13- 21.
[18] Garbout A,Munkholm L J,Hansen S B.Tillage effects on topsoil structural quality assessed using X-ray CT,soil cores and visual soil evaluation.Soil and Tillage Research,2013,128:104- 109.
[19] Lebron I,Suarez D,Schaap M.Soil pore size and geometry as a result of aggregate-size distribution and chemical composition.Soil Science,2002,167(3):165- 172.
[20] Konrad J M.Physical processes during freeze-thaw cycles in clayey silts.Cold Regions Science and Technology,1989,16(3):291- 303.
[21] 齐吉琳,张建明,朱元林.冻融作用对土结构性影响的土力学意义.岩石力学与工程学报,2004,22(S2):2690- 2694.
[22] 倪万魁,师华强.冻融循环作用对黄土微结构和强度的影响.冰川冻土,2014,36(4):922- 927.
[23] 骆紫藤,牛健植,孟晨,张英虎,杜晓睛,蔺星娜,贾京伟.华北土石山区森林土壤中石砾分布特征对土壤大孔隙及导水性质的影响.水土保持学报,2016,30(3):305- 308,316.
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