桑干河流域淤地坝沉积泥沙特征及其来源解析

目的]为查明桑干河流域的泥沙主要策源地和侵蚀产沙变化。方法]选取阳原县高墙乡典型淤地坝沉积泥沙为研究对象，利用复合指纹识别技术，测定沉积泥沙及其源地的土壤粒径、SOC、TN、¹³⁷Cs、低频质量磁化率等9种指纹因子，研究了不同淤积阶段的泥沙策源地及坝控小流域侵蚀产沙演变规律。结果](1)沉积泥沙中¹³⁷Cs平均含量较低，与沟壁土壤无显著差异(p>0.05),但极显著小于林草地和耕地的¹³⁷Cs含量(p<0.01),这指示淤地坝沉积泥沙主要来源于沟壁；(2)由于沟壁中大部分¹³⁷Cs含量低于检出限，¹³⁷Cs较好地指示泥沙主要来源沟谷地中的沟壁，但难以用于小流域多种策源地的判别，经Kruskal-Wallis H非参数检验和多元逐步判别分析筛选，确定TN+X_lfb+SOC构成最佳指纹因子组合，有效地判别小流域2006—2017年泥沙源地的平均贡献率为沟壁(82.68%±8.20%)>耕地(15.36%±8.46%)>林草地(1....

Sediment Characteristics and Sources Tracing of Warping Dam in Sanggan River Basin

Objective] This study intends to explore the main source of sediment and the evolution of erosion and sediment yield in Sanggan River Basin. Methods] A typical warping dam in Gaoqiang Township, Yangyuan County was selected as the research object. The composite fingerprint identification technology was used to determine nine fingerprint factors, including soil particle size, SOC, TN, radionuclide (¹³⁷Cs) and low-frequency magnetic susceptibility, of sediment and its source areas. The evolution patterns of erosion and sediment production in different sedimentation stages of sediment source areas and dam controlled small watersheds were studied. Results] (1) The average content of ¹³⁷Cs in sediment was relatively low, and it was not significantly different from that of gully wall soil, but it was extremely significantly lower than that of forest-grasslands and croplands soil (p<0.01), which indicated that the sediment was mainly from gully wall. (2) As the majority of ¹³⁷Cs content of gully wall was below the detection limit, ¹³⁷Cs was a good indicator for identifying gully wall as the main sediment source but it was difficult to be used for distinguishing multiple sediment sources in the small basin. Through Kruskal-Wallis H nonparametric test and multiple stepwise discriminant analysis screening, the optimal combination of fingerprint factors was TN+X_lfb+SOC, which effectively distinguished the average contribution rate of sediment source areas in small watersheds from 2006 to 2017. The contribution rate followed the order of gully wall (82.68%±8.20%) > croplands (15.36%±8.46%) > forest-grasslands (1.96%±0.33%). (3) In the evolution of erosion and sediment yield, gully wall was the main sediment contribution area for a long time, forest-grasslands had weak response to erosive rainfall, and the sediment contribution rate of croplands increased significantly when extreme rainstorm occurred. Conclusion] Overall, the ¹³⁷Cs tracing technique was suitable for identifying the main sediment source in the small basin, and the composite fingerprint technique was better at identifying multiple sediment sources. The collapse of gully walls caused by gully erosion was the main cause of severe soil erosion in the Sanggan River Basin.