Using the sediment fingerprinting method to identify the sediment sources in small catchments with similar geological conditions

Traditional fingerprinting methods discriminate sediment sources based on differences in the source geological conditions or land use types. However, whether this method is effective if both the geological conditions and land use types are similar and the circumstances under which the method can be used remain unclear. To further understand the scope of applying the fingerprint identification method, this study selected the Wangjiagou catchment, which consists of subcatchments A and B, as the target. In this catchment, corn (Zea mays L.) was the species with the highest proportion in the dry land. Furthermore, the geological conditions in the catchment are consistent and, the soil is Eutric Regosol developed from the purple rock strata of the Jurassic system. A total of 85 source samples were collected in subcatchments A and B, and 11 sediment samples were collected at the outlets of the each of the subcatchments in the rainy season (from June to October). This research analyzed 48 geochemical elements as the potential fingerprint factors. In this case, the optimum composite fingerprint consisted of five individual properties (Zn, Ce, La, Li and Eu) in subcatchment, whereas four geochemical properties (Mn, La, Ni and Lu) passed the stepwise discriminant function analysis in subcatchment B. These properties exhibited discriminative powers of 100% in the respective subcatchments. The research results indicated the following: first, the multivariate mixing model can provide the contribution rates of each sediment source; second, the goodness of fit (GOF) of this model was greater than 95% in both subcatchments; and third, the sediment uncertainty of each source was within 5% in both subcatchment A and B. These findings indicate that the fingerprinting method can be used in areas with small differences in land use and geological conditions. The results show that great focus needs to paid to soil erosion on slope land in subcatchment A and mulberry fields in subcatchment B. In this area, high-impact human activities (i.e., extensive channel excavation and highly intense machine cultivation) have negated certain soil and water conservation measures. Therefore, in order to reduce soil erosion and ensure that the existing soil and water conservation measures are effective, farmers should implement rational channel management and no tillage or minimal tillage practices. Furthermore, to improve the fertilizer utilization rate of agro-ecosystems, deep fertilizer application and straw return technology should be promoted.