Photodegradation of Detergent Phosphorus in Aquatic Environment

Eutrophication potential of anthropogenic phosphorus depends on its bioavailability. Here, we present the proof that the main component of washing powders, sodium triphosphate (also known as sodium tripolyphosphate—STPP), can be photodegraded to orthophosphate. The process was studied under simulated sunlight in coastal and river water samples, distilled water, and solution of humic substances. Irradiation of samples enriched with STPP (130 μM P) resulted in release of up to 1 μM of orthophosphate. The measurable effects were observed solely in presence of inorganic matrix. It may suggest that degradation of STPP is driven mainly by the direct energy transfer from photo-excited colored dissolved organic matter: both sodium triphosphate and humic substances are negatively charged at natural water pH and presence of cations abates electrostatic repulsion between them. In this case, absorption of the sample remains the main factor affecting efficiency of the degradation.