Sediment source apportionment using geochemical composite signatures in a large and polluted river system with a semiarid-coastal interface, Brazil

The Ipojuca River is the third most polluted fluvial system in Brazil. Sediment-associated metal fluxes threaten the environmental health in the estuary of this system. However, the sources supplying these particle-bound contaminants have not been determined yet. Sediment source fingerprinting provides a powerful technique to obtain such information. Accordingly, the aim of this study was to quantify the source contributions to suspended and bed sediments in this polluted river system with a semiarid-coastal interface using geochemical tracers. A total of 20 geochemical tracers measured on 207 source samples were used as potential fingerprint properties to discriminate and quantify the contributions of potential sources classified according to three distinct typologies (distribution of land uses, soil classes, and the environmental contrasts between the upper and lower catchment). All analyzed elements passed the range test for conservative behaviour. Using the MixSIAR model, the lower catchment, Oxisols, and sugarcane croplands were identified as the dominant sediment sources. These new data provide a basis to target the management of excessive sediment loads and sediment-associated contaminants moving towards estuarine and coastal environments. The multiple sources framework discussed herein can also help to improve the appeal of sediment source fingerprinting among environmental policymakers given the capacity for informing targeted management.