Influence of pH on the fluorescence of dissolved organic matter

During two surveys (June, 1980 and March, 1981) the influence of the pH on the fluorescence (mFl) was studied in the Ems-Dollart estuary. In the natural pH range (7–9) the fluorescence (mFl) increased by 16.4%. To express the fluorescence (mFl) at a fixed pH, a formula was derived (see eq. 1). From the results it is concluded that an increase in fluorescence (mFl) does not necessarily include an increase in the concentration of fluorescent matter. For areas where pH changes are possible, it is premature to infer from the increase in fluorescence that the fluorescent matter is produced in situ.