Degradation mechanisms of cyanobacteria neurotoxin β-N-methylamino-l-alanine (BMAA) during UV254/H2O2 process: Kinetics and pathways

In this work, the UV 254 /H 2 O 2 process was utilized to remove β-N-methylamino- l -alanine (BMAA), a kind of cyanobacteria neurotoxin, and the influence of reaction parameters and environmental factors on the degradation of BMAA has been systematically investigated. The results showed that BMAA could be effectively removed in the UV 254 /H 2 O 2 system compared to UV or H 2 O 2 alone and OH was confirmed as the main ROS to degrade BMAA. The degradation rate of BMAA increased first and then decreased with the increase of pH and the maximum k obs was 0.1545 min −1 obtained at pH 9. The removal of BMAA in the UV 254 /H 2 O 2 system was inhibited in actual water, while the degradation rate of BMAA in actual water could still exceed 90% by appropriately extending the reaction time. The decrease in the degradation efficiency of BMAA in actual water was primarily due to the ultraviolet light absorption and competition effects of NOM, and anions (Cl − and HCO 3 − ) would also inhibit the degradation of BMAA. Five by-products ([M − H] -  = 118, 103, 88, 87 and 59) were identified in this study and the degradation pathways of BMAA were proposed. The production of by-products was attributed to the fracture of the C–N bond and hydroxylation reaction. This study is worthwhile to deepen the understanding of the degradation mechanism of BMAA in the UV 254 /H 2 O 2 system.