Fig. 1.

a Absorbance scans across the wavelength spectrum from 230 to 370 nm for one exemplary exudate sample (10.3 mg C L⁻¹) and one calibration standard (10.1 mg C L⁻¹). Red line indicates the selected wavelength (260 nm) for photometric DOC determination in exudation samples. b Absorbance scans across the wavelength spectrum from 250 to 280 nm. Grey area indicates most suitable wavelength spectrum (256–270 nm)