Persistent pesticides pose significant environmental and health risks due to their resistance to conventional water treatment

methods. This study explores the cooperative oxidation and reduction of two typical pesticides, namely atrazine 

(ATZ) and lindane (LND), under vacuum ultraviolet (VUV) irradiation, with a particular focus on the dual role of dissolved

oxygen (DO) in modulating degradation mechanisms and kinetics. In oxygen-deprived conditions, VUV irradiation 

achieved 92.9% ATZ removal with minimal TOC reduction (<5%), whereas the introduction of 10 mg L–1 DO enhanced 

ATZ mineralization to 67.1% by sustaining hydroxyl radical (HO•

) concentrations. Conversely, DO presence reduced LND 

degradation efficiency from 86.5% to 46.6% by scavenging solvated electrons (eaq–

), yet improved TOC removal from 

4.8% to 26.7% through enhanced oxidative transformation of intermediates. ATZ undergoes hydroxyl radical-mediated 

oxidation, while LND degradation is driven by solvated electrons-initiated reduction. A competition kinetics model was 

employed to determine the second-order rate constants of reactive species, revealing that HO•

 plays a dominant role in 

ATZ degradation (kATZ,HO• =2.5×109

 M–1S–1) and eaq–

 is primarily responsible for LND decomposition (kLND,eaq−

=1.0×1010 M–1S–1). Numerous degradation byproducts were identified by GC-MS, revealing three pathways for ATZ 

and multiple reductive routes for LND. These findings highlight the intricate interplay between oxidative and reductive 

mechanisms mediated by DO, emphasizing the necessity of controlling oxygen levels for efficient pollutant degradation 

and comprehensive mineralization.