The effect of chloride ions and organic matter on the photodegradation of acetamiprid in saline waters

The photodegradation kinetics of the neonicotinoid insecticide acetamiprid (ACT) was investigated under different conditions of pH, salinity and dissolved organic matter (DOM). Photodegradation of ACT in saline and freshwaters followed pseudo-first-order kinetics. Varying pH from 5 to 9 did not significantly affect the photodegradation rate constants (k(p)) of ACT. Addition of chloride ions increased significantly the value of k(p). In the presence of AHA, 10 mg L-1, k(p) was reduced to approximately 34% of that in sodium chloride solutions 35 g L-1 The observed inhibition may be a consequence of the antioxidant properties of DOM and/or the shading of DOM in the solution. In coastal waters, k(p) showed a tendency to increase with increasing, of salinity and to decrease in the presence of DOM. This is an important outcome since coastal lagoons are important and dynamic systems that are likely to be highly influenced by global climate changes.