Effects of soil aggregates on settling velocity of sediment
WU Sinan1, FU Suhua1,2
1. Faculty of Geographical Science, Beijing Normal University, 100875, Beijing, China; 2. State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, 712100, Yangling, Shaanxi, China
Abstract：[Background] Sediment eroded by water consists largely of soil aggregates. The settling velocity of such aggregates and soil primary particles is of fundamental importance to the processes of sediment transport and deposition in water. However, most currently available process-based soil erosion models are using soil texture or mineral particle distribution, and little consideration is given to aggregates, therefore which cannot fully reflect the transport behavior of sediment.[Methods] Five typical soils including loess soil, cinnamon soil, purple soil, black soil and red soil were used to compare the settling velocity of sediment. The settling velocity of sediment for the undispersed particles (soil particles and aggregates) and dispersed particles(soil particles) were measured using a modified bottom withdrawal tube method. By comparing the results of dispersion and indispersion, the impact of soil aggregates on settling velocity of sediment was analyzed. The data analysis process of this study was completed by Excel 2016. The significance difference test and correlation analysis were carried out by SPSS 23. Origin 2016 was used to complete the fitting of the model and the drawing of the graphs.[Results] Aggregates had a significant effect on settling velocity of sediment. For the tested soils, the aggregates resulted in the increase in settling velocity. Aggregates had more obvious effect on the settling velocity of small particles than that of the large particles. Among the different soil types, the effect of aggregates on the increasing rate in settling velocity of purple soil, black soil, red soil, loess soil and cinnamon soil decreased in turn, and the main reason was that the characteristics of soil particles (including soil primary particles and aggregates)were different. Among the soil characteristic parameters, the mean weight diameter of aggregates and aggregation degree had more important effect on sediment settling velocity. The increasing rate in settling velocity was significantly correlated to the mean weight diameter of aggregates and aggregation degree.[Conclusions] The results indicate that there is a great difference between the settling velocity of sediment containing aggregates and only soil particles. The mean weight diameter of aggregates or aggregation degree may be a proper parameter for reflecting the effects of aggregates on settling velocity of sediment. It is of great significance for considering the influence of aggregates in the process of sediment settling to understand the law of sediment movement, study the mechanism of erosion process and even develop the process-based soil erosion models.
庞玲, 张科利, 朱明, 等. 泥沙沉降速度实验研究方法回顾与评述[J]. 人民黄河, 2006, 28(5):50. PANG Ling, ZHANG Keli, ZHU Ming, et al. Review of experimental research method on settling velocity of sediment[J]. Yellow River, 2006, 28(5):50.
[2]
STOKES G G. On the effect of the internal friction of fluids on the motion of pendulums[M]. Cambridge:Pitt Press, 1851:86.
[3]
钱宁, 万兆惠. 泥沙运动力学[M]. 北京:科学出版社, 1983:129. QIAN Ning, WAN Zhaohui, Sediment movement mechanics[M]. Beijing:Science Press, 1983:129.
[4]
CHENG Niansheng. Simplified settling velocity formula for sediment particle[J]. Journal of Hydraulic Engineering, 1997, 123(2):149.
[5]
李铭志, 何炎平, 诸葛玮, 等. 泥沙颗粒沉降速度计算方法比较分析[J]. 水运工程, 2014(6):6. LI Mingzhi, HE Yanping, ZHUGE Wei, et al. Comparative analysis of settling velocity for sand.[J]. Port & Waterway Engineering, 2014(6):6.
[6]
AKSOY H, KAVVAS M L. A review of hillslope and watershed scale erosion and sediment transport models[J]. Catena, 2005, 64(2/3):247.
[7]
WALLING D E. Erosion and sediment yield researchsome recent perspectives[J]. Journal of Hydrology, 1988, 100(1/3):113.
[8]
BEUSELINCK L, STEEGEN A, GOVERS G, et al. Characteristics of sediment deposits formed by intense rainfall events in small catchments in the Belgian Loam Belt[J]. Geomorphology, 2000, 32(1/2):69.
[9]
郝燕芳, 刘宝元, 杨扬, 等. 中国5种典型土壤的侵蚀泥沙粒径分布特征[J]. 水土保持学报, 2018, 32(2):150. HAO Yanfang, LIU Baoyuan, YANG Yang, et al. Size distribution characteristics of sediments eroded from five typical soil in China[J]. Journal of Soil and Water Conservation, 2018, 32(2):150.
[10]
HU Y, KUHN N J. Aggregates reduce transport distance of soil organic carbon:are our balances correct?[J]. Biogeosciences Discussions, 2014, 11(6):6209.
[11]
胡亚鲜, KUHN N J. 利用土壤颗粒的沉降粒级研究泥沙的迁移与分布规律[J]. 土壤学报, 2017, 54(5):1115. HU Yaxian, KUHN N J. Using settling velocity to investigate the patterns of sediment transport and deposition[J]. Acta Pedologica Sinica, 2017, 54(5):1115.
[12]
LOVELL C J, ROSE C W. The effects of sediment concentration and tube-diameter on particle settling velocity measured beyond Stokes' range; experiment and theory[J]. Journal of Sedimentary Research, 1991, 61(4):583.
[13]
LOCH R J, SLATER B K, DEVOIL C. Soil erodibility (Km) values for some Australian soils[J]. Australian Journal of Soil Research, 1998, 36(6):1045.
[14]
SVEN O. The size distribution of particles in soils and the experimental methods of methods of obtaining them[J]. Soil Science, 1925, 19(1):1.
[15]
LOVELL C J, ROSE C W. Measurement of soil aggregate settling velocities. 1. A modified bottom withdrawal tube method[J]. Australian Journal of Soil Research, 1988:26(1):55.
[16]
闫峰陵, 史志华, 蔡崇法, 等. 红壤表土团聚体稳定性对坡面侵蚀的影响[J]. 土壤学报, 2007, 44(4):577. YAN Fengling, SHI Zhihua, CAI Chongfa, et al. Effects of topsoil aggregate stability on soil erosion at hillslope on ultisoils[J]. Acta Pedologica Sinica, 2007, 44(4):577.
[17]
陈正发, 史东梅, 谢均强, 等. 紫色土旱坡耕地土壤团聚体稳定性特征对侵蚀过程的影响[J]. 中国农业科学, 2011, 44(13):2721. CHEN Zhengfa, SHI Dongmei, XIE Junqiang, et al. Aggregate stability of purple soil and its impacts on soil erosion of slope dry land[J]. Scientia Agricultura Sinica, 2011, 44(13):2721.
2019, Vol. 17 
