Intra-storm variations in the contributions of geological formations to suspended sediment; A comparison between Bayesian and FingerPro sediment fingerprinting methods

One effective method for identifying sediment sources is quantifying erosion-sensitive geological formations within a watershed. This can be achieved through sediment fingerprinting techniques. In this study, intra-event variations in the contributions of geological formations to suspended sediment samples in the Kasilian watershed, Iran, were analyzed using weathering indices and geochemical tracers. To achieve this, 23 suspended sediment samples were collected at the watershed outlet during rainfall events, along with 28 surface soil samples from different geological units identified as potential sediment sources. Geochemical elements in these samples were measured, and statistical analyses were performed using the FingerPro package in R software. The optimal tracers selected included the elements Terbium (Tb), Dysprosium (Dy), Yttrium (Y), Cerium (Ce), and the weathering index SOC. The results indicated that, using a multivariate mixing model in FingerPro, the geological units TRJS, Pic, and Q contributed 73%, 18%, and 9% to sampled sediment, respectively. Using a Bayesian model, the relative contributions were 76% for TRJS, 14% for Pic, and 10% for Q. Additionally, the specific sediment contribution (relative contribution per hectare) was determined to be 0.015%, 0.015%, and 0.095% for the TRJS, Pic, and Q units, respectively.