Use of soil organic biomarkers for tracing the origin of eroded sediment: case study in Petzenkirchen (Austria)

Compound-specific stable isotopes (CSSI) technique based on the measurement of δ¹³C signatures of organic biomarker compounds such as fatty acids (FAs) has been used since the end of the 2000s to reinforce the knowledge about sediment production and budget in various ecosystems.
The watershed of Petzenkirchen, located 100 km west from Vienna (Austria), was selected to establish the origin of the sediment produced at its outlet using δ¹³C-FAs analysis. The climatic conditions of the area are temperate with continental influences with a mean temperature of 9.5˚ C and yearly precipitation of 823 mm. The dominant soil types are Cambisols and Planosols. Based on existing land-use records, most of the agricultural fields are dominated by a rotation of winter wheat followed by maize cultivation.
Considering the specific geomorphology, the flow of the runoff, the significant interaction of roads, the distance and connection of the potential sources to the outlet, the contributing area of the site has been set to around 50 ha and 7 sources most likely to contribute to the sediment at the outlet were investigated. Using the mixing polygons approach, the δ¹³C of saturated long chain FAs (i.e. C24:0 and C26:0) allowed the best discrimination for establishing the contribution of sources to the sediment collected at the exit of the watershed (i.e. the mixture). The relative contribution to the soil mixture of the different source soils identified has been determined using the Stable Isotope Mixing Models in R (SIMMR) and the specific organic carbon content of each source. The simulated results derived with SIMMR highlights that more than half of the sediment reaching the outlet of the watershed originates from stream bank. 
This Austrian study confirms that the information gained with δ¹³C-FAs analysis could provide unique support for allowing effective agroecosystems management.