Factor Selection Study to Determine the Sediment Source of a Small Watershed in the Loess Plateau Based on the Multi-element Tracer Technique

摘要

Tracer techniques, such as the multi-element tracer technique, have been studied in recent decades to determine their effectiveness in estimating the sediment sources in the Loess plateau. The first step in studying sediment sources using the multi-element tracer technique is to screen for indicating factors; however, few studies have presented a reference of the trace elements that can be used in the study of sediment sources in the Loess plateau. Furthermore, because the loess deposition resulted from the long-term operation of wind power and loess is generally homologous, significant differences usually do not occur among the concentrations of the loess’ chemical elements. To determine obvious differences in the chemical element concentrations, additional factors must be selected. For our study site, we selected a typical small closed watershed in the Peng-yang region of the Ningxia Province in China, and 20 cm surface soil samples were collected at each of the following five geographical locations: (i) ridge, (ii) hill slope, (iii) shoulder line of the valley, (iv) channel slope and (v) area in front of the dam. A neutron activation analysis was then performed, and 31 major soil constituents were detected in the standards and soil samples. The results showed that marked differences occurred among the concentrations of Eu, Fe, Al, Co, Cs, Hf, Sc, Th, Cr, Rb and Mn. And combining a previous study, we suggest that the soil nutrient index, soil magnetic susceptibility and soil concentrations of Al, Eu, Cs, Hf, Sc, Co, Th, Cr, Rb,137Cs, 7Be, 210Pb and 226Ra can be used as indicating factors in the study of sediment sources in the Loess plateau.