Dissolved　organic　matter　(DOM)　is　very　important　in　determining　the　speciation,　behaviors,　and　risk　of　metal　pollutants　in　aquatic　ecosystems.　Photochemical　and　microbial　degradation　are　key　processes　in　the　cycling　of　DOM,　yet　their　effects　on　the　DOM-Pb(II)　interaction　remain　largely　unknown.　This　was　studied　by　examining　the　complexation　of　river　DOM　with　Pb(II)　after　degradation,　using　fluorescence　quenching　titration　and　excitation-emission　matrices-parallel　factor　analysis　(EEMs-PARAFAC).　Three　humic-like　and　two　protein-like　components　were　identified,　with　strong　removals　of　humic-like　components　and　decreasing　average　molecular　weight　and　humification　degree　of　DOM　by　photo-　and　photo-microbial　degradation.　The　changes　in　humic-like　abundance　and　structure　resulted　in　notable　weakening　of　their　interaction　with　Pb(II).　The　tryptophan-like　C2　was　also　mainly　removed　by　photo-degradation,　while　the　tyrosine-like　C3　could　be　either　removed　or　accumulated.　The　Pb(II)-binding　of　protein-like　components　was　generally　weaker　but　was　enhanced　in　some　degradation　groups,　which　might　be　related　to　the　lowering　competition　from　humic-like　components.　The　binding　parameters　correlated　significantly　with　the　DOM　indices,　which　were　dominated　by　photo-degradation　for　humic-like　components　but　by　seasonal　variations　for　the　tyrosine-like　component.　These　results　have　implications　for　understanding　the　key　mechanisms　underlying　the　variability　of　the　DOM-metal　interaction　in　aquatic　environments.　©　2023　Elsevier　Ltd