Photochemical treatment strategies for okadaic acid degradation: Effects of salinity, oxidants, and UV sources

Moreno-Andrés, Javier; Lage, Sandra; Braga, Ana Catarina; Reis Costa, Pedro

http://hdl.handle.net/10400.1/27489

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Authors

Moreno-Andrés, Javier

Lage, Sandra

Braga, Ana Catarina

Reis Costa, Pedro

Abstract(s)

This study evaluates the degradation and detoxification of okadaic acid (OA), a marine biotoxin, through UVassisted photochemical processes using environmentally relevant OA concentrations. Experiments were conducted in distilled water (DW) and artificial seawater (ASW), applying two UV sources: UV-LED (lambda(max) = 275 nm) and low-pressure mercury lamp (LP-Hg; lambda = 254 nm), combined with hydrogen peroxide (HP), sodium peroxydisulfate (PDS), and potassium peroxymonosulfate (PMS). Photolysis alone was ineffective, and kinetic rate constants (k(obs); min(-1)) followed the trend UV/PMS > UV/PDS > UV/HP for both UV sources. While all treatments showed high OA removal (>79 %) in DW, degradation was significantly reduced for HP (72.8 %-89.9 %) and PDS (67.8 %-76.6 %) in ASW. In contrast, UV/PMS efficacy improved in saline media, achieving rapid and effective degradation of OA, and reaching 99 % detoxification (PP2A activity) within 15 min. The main transformation product, norokadanone (m/z 757.453), formed via decarboxylation, showed significantly reduced toxicity compared to OA. These results confirm the suitability of sulfate radical-based processes (particularly UV/ PMS) for OA mitigation in marine environments. In addition, this work highlights the critical role of water matrix composition in marine toxin treatment and supports the development of scalable, mercury-free strategies for effectively mitigating hazardous compounds in coastal environments.