Fig. 6. Range of correction factors for variations in excitation light reflection at the surface of soil cores from the 0- to 0.1-m, 0.2- to 0.3-m, and the 0.5- to 0.6-m layer of the Unterehrendingen soil for the excitation light wavelengths of brilliant sulfaflavine (BF) and sulforhodamine B (SB). Horizontal bars mark the interval that is defined in Eq. [10] and that contains 90% of the correction factors.