The role of natural organic matter (NOM) in contaminants removal by photolysis and photocatalysis has aroused increasing interest. However, evaluation of the influence of NOM characteristics on the transformation products (TPs) formation and transformation pathways of contaminants has rarely been performed. This study investigated the decomposition kinetics, mineralization, TPs formation and transformation pathways of antibiotic ciprofloxacin (CIP) during photolysis and photocatalysis in the presence of three commercial NOM isolates (Sigma-Aldrich humic acid (SAHA), Suwannee River humic acid (SRHA) and Suwannee River NOM (SRNOM)) by using UVA light emitting diode (UVA/LED) as an alternative light source. NOM isolates insignificantly affected CIP photolysis but strongly inhibited CIP photocatalysis due to competitive radical quenching. The inhibitory effect followed the order of SAHA (49.6%) > SRHA (29.9%) > SRNOM (21.2%), consistent with their •OH quenching abilities, SUVA₂₅₄ values and orders of aromaticity. Mineralization rates as revealed by F⁻ release were negatively affected by NOM during CIP photocatalysis. TPs arising from hydroxylation and defluorination were generally suppressed by NOM isolates in UVA/LED and UVA/LED/TiO₂ systems. In contrast, dealkylation and oxidation of piperazine ring were promoted by NOM. The enhancement in the apparent formation kinetics (k_app) of TP245, TP291, TP334a, TP334b and TP362 followed the order of SRNOM > SRHA > SAHA. k_app values were positively correlated with O/C ratio, carboxyl content, E2/E3 and fluorescence index (FI) of NOM and negatively related with SUVA₂₅₄ values. The observed correlations indicate that NOM properties are important in determining the fate and transformation of organic contaminants during photolysis and photocatalysis.

天然有机物（NOM）在通过光解和光催化去除污染物中的作用引起了越来越多的关注。但是，很少进行NOM特性对污染物的转化产物（TPs）形成和转化途径的影响的评估。这项研究调查了抗生素环丙沙星（CIP）在三种商业NOM分离物（Sigma-Aldrich腐殖酸（SAHA），Suwannee River腐殖酸（SRHA）和Suwannee River NOM（SRNOM））通过使用UVA发光二极管（UVA / LED）作为替代光源。NOM分离出的CIP光解影响不大，但由于竞争性自由基淬灭而强烈抑制CIP光催化。_254个值和顺序的芳香性。如发现被F矿化率^-发行呈负NOM进行CIP光催化过程的影响。在UVA / LED和UVA / LED / TiO ₂系统中，NOM分离物通常抑制了由羟基化和脱氟产生的TP 。相反，NOM促进哌嗪环的脱烷基和氧化。TP245，TP291，​​TP334a，TP334b和TP362的表观形成动力学（k _app）增强遵循SRNOM> SRHA> SAHA的顺序。k _app值与OM的O / C比，羧基含量，E2 / E3和荧光指数（FI）呈正相关，与SUVA ₂₅₄呈负相关价值观。观察到的相关性表明，NOM性质对于确定光解和光催化过程中有机污染物的命运和转化非常重要。