降雨驱动下红壤团聚体的溅蚀特征及周转过程

Splash Erosion Characteristics and Turnover Process of Red Soil Aggregates Driven by Rainfall

[目的]研究降雨驱动作用下土壤团聚体受雨滴打击发生破碎和形成的过程,丰富土壤侵蚀研究机理。[方法]基于稀土元素示踪法,对各粒径土壤团聚体同时进行标记。在90 mm/h降雨溅蚀条件下,通过各粒径土壤团聚体(2~5 mm,0.25~2 mm,0.053~0.25 mm,<0.053 mm)在不同降雨特征参数(降雨历时、雨滴大小)下的质量变化和稀土元素含量变化,定量分析了团聚体间的周转路径和溅蚀颗粒特征。[结果]降雨驱动作用下,溅蚀量和溅蚀率会随着降雨动能的增加而变大,溅蚀颗粒主要分布于0.25~2 mm粒径范围内;除>2 mm的颗粒为大团聚体直接飞溅产生,<0.25 mm粒级溅蚀颗粒均主要源于大粒级团聚体破碎形成,最高可达到73.83%,其次为该粒级直接被击飞形成,同时会有小粒级颗粒吸附黏结形成;在残余团聚体的动态周转过程中,主要是相邻级别的团聚体间形成和破碎过程占比较高,其中大团聚体破碎产生小团聚体和粉黏粒团聚形成小团聚体分别对原粒级团聚体的破碎和形成方向的贡献率较高,分别达到24.06%~42.15%和36.83%~70.76%,且随着降雨时间的变化,大团聚体首先破碎成小团聚体,再逐级破碎成更小粒级的团聚体,未参与动态周转的团聚体比例会逐渐下降。[结论]降雨溅蚀不断驱动土壤团聚体的周转过程,并对溅蚀特征产生较大影响,未来应引入土壤营养物质迁移研究,完善土壤侵蚀过程定量模型。

[Objective]The aim of this study is to explore the process of breakdown and formation of soil aggregates driven by rainfall,and then to enrich the research of mechanisms of soil erosion.[Methods]Based on the rare earth element tracing method,a variety of rare earth elements were used to label soil aggregates with various particle sizes.Splash erosion tests were conducted under the stimulated rainfall intensity of 90 mm/h with the different rainfall characteristic parameters controlled(rainfall duration,raindrop size)to obtain the changes of distribution of mass and rare earth element content of soil aggregates(2~5 mm,0.25~2 mm,0.053~0.25 mm,<0.053 mm),the turnover paths between aggregates could be quantitatively analyzed.[Results]The splash amounts and rates increase with the increase of rainfall kinetic energy,most of which range in 0.25~2 mm.Except for the>2 mm particles which directly originate from large aggregates,the splash particles whose diameter are<0.25 mm are mainly formed by the crushing of large-size aggregates,and the highest can reach 73.83%;the second is the aggregates of the current particle size knocked off by the raindrop,with little aggregates of small-sized particles adsorbed and bound together.In the dynamic turnover process of residual aggregates,the formation and breakdown processes between adjacent-level aggregates are mainly responsible,among which the breakdown of large aggregates that produces small aggregates and the formation of the small aggregates that originate from silt and clay have higher contribution rates to the breakdown or forming direction of the current size aggregates,reaching 24.06%~42.15%and 36.83%~70.76%,respectively,and with the change of rainfall durations,the large aggregates are first broken into smaller aggregates,then microaggregates and silt and clay step by step,and the proportion of aggregates that do not participate in dynamic turnover gradually decrease.[Conclusion]Splash erosion continuously drives the turnover process of soil aggregates and has a great impact on splash erosion characteristics.In the future,the research on soil nutrient migration should be introduced to improve the quantitative model of soil erosion process.