Determination of the Geogenic Metal Background in Surface Water: Benchmarking Methodology for the Rivers of Saxony-Anhalt, Germany

Geogenic concentrations are defined as those concentrations that represent the natural background without any anthropogenic influence. The paper describes a statistical method for determining geogenic metal concentrations in rivers based on the concept of “aggregated riverine landscapes” (ARLs), which applies to all rivers in the Federal State of Saxony-Anhalt (Germany). The methodology includes the pre-selection of existing data by eliminating all sampling locations from the database which have anthropogenic influence, the GIS-based allocation of the sampling locations with respect to the respective ARL being the evaluation units, and the assessment of the geogenic background by statistical calculation of the 90th percentile. After validation of the methodology, the existing database was complemented by additional measurements for regions with data gaps. About 85,000 records of water samples, 1400 records of sediment samples, and 920 records of suspended particulate samples were used for the determination of the geogenic metal concentrations in the rivers of Saxony-Anhalt. The investigation included the parameters Al, Ag, As, B, Ba, Be, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, Ti, U, V, and Zn. The investigation results offer the determination of regions with increased background levels for certain metals or metalloids in Saxony-Anhalt.