复合指纹法解析典型黑土小流域侵蚀泥沙来源

Analysis of erosion sediment sources in typical Mollisols watershed by composite fingerprinting technique

以海伦市光荣村小流域为研究对象,分析流域内6个潜在泥沙来源地和沉积区的25个地球化学特征,利用Kruskal-Wallis H检验和逐步判别分析确定最佳的指纹因子组合,通过多元混合模型计算各泥沙源地的相对贡献率.结果表明:共有11种因子(Mg、Ti、Cr、Fe、Cu、As、Mo、Tl、P、C、K)被确认为最佳指纹因子组合,判别率达到75%,拟合优度均大于0.80.各泥沙源地对沉积区0~20cm土层泥沙贡献率依次为:朝北坡向靠近林地的耕地(53.11%)>朝北坡向靠近道路的耕地(25.00%)>开垦时间早的耕地(11.91%)>靠近流域出口的耕地(6.57%)>林地(3.41%)>朝南坡向耕地(0%).沉积区0~30cm不同土层泥沙主要来源于流域朝北坡向耕地,而在林地北侧耕地的泥沙贡献率最小.流域内不同的土地利用方式对泥沙贡献率的影响比地形因子更大,然而在同样的土地利用方式下主要受地形因子的影响.早期人类垦殖、修路等活动对沉积区深层泥沙贡献率影响较大,而后期耕地活动对沉积区表层泥沙贡献率影响较大.基于地球化学特征因子的复合指纹识别技术能够有效判别典型黑土小流域泥沙来源.

It is an important foundation for the scientific prevention and control of soil erosion to clarify the characteristics of erosion sediment sources in the Mollisols watersheds.Using the Guangrong Village sub-basin in Hailun City as the research object,25geochemical characteristics of six potential sediment source sites and sedimentation areas in the basin were analyzed,and the best combination of fingerprint factors was determined using Kruskal-Wallis H-test and stepwise discriminant analysis,and the relative contribution of each sediment source site was calculated by a multivariate mixture model.The results showed that 11factors(Mg,Ti,Cr,Fe,Cu,As,Mo,Tl,P,C,K)were identified as the best fingerprint factor combinations with a discrimination rate of 75%and a goodness of fit of>0.80.The contribution of each sediment source site to the sedimentation of the 0~20cm soil layer was in the following order:arable land with a north-facing slope near woodland(53.11%)>arable land with a north-facing slope near road(25.00%)>cultivated land with early reclamation(11.91%)>cultivated land near the watershed outlet(6.57%)>forested land(3.41%)>cultivated land with a south-facing slope(0%).Sediment in the different soil layers of 0~30cm in the sedimentation zone mainly originated from the north-facing sloping cultivated land in the watershed,while the smallest contribution of sediment was found in the cultivated land on the north side of the woodland.Different land use practices within the watershed have a greater influence on the sediment contribution than the topographic factors,however,it is mainly influenced by the topographic factor under the same land use practices.Early human activities such as reclamation and road building had a greater influence on the deep sediment contribution to the sedimentation area,while later cultivation activities had a greater influence on the surface sediment contribution to the sedimentation area.The composite fingerprinting technique based on geochemical feature factors can effectively discern the sediment sources in typical black soil sub-basins.