Dissolved organic nitrogen (DON) accounts for a large proportion of the total aquatic nitrogen. Compared with dissolved inorganic nitrogen (DIN), the reactivity of DON has received limited attention. Photo-ammonification contributes significantly to the transformation of DON to DIN. However, information on the mechanism of this process is limited. This study investigated the photo-ammonification process of different natural surface water samples. The effects of seasons and rainfall on this process were explored, and the contributing factors were identified. Results showed that the seasonal effect on photo-ammonification differed for different water samples, whereas rainfall increased the rates of photo-ammonification for most of the lakes. The concentrations of reactive species, including triplet states of chromophoric dissolved organic matter (³CDOM*) and singlet oxygen (¹O₂), were found to be significantly correlated with water optical-parameters. Multivariable linear regression analysis (R² = 0.617) revealed that the photo-ammonification of DON was mainly facilitated by ³CDOM* whereas ¹O₂ competed with ³CDOM* and showed an inhibiting effect. The components of dissolved organic matter (DOM) were identified by fluorescence excitation emission matrices coupled with parallel factor analysis and were found to be greatly influenced by the location. Allochthonous humic-like components were found to promote the production of reactive species while tryptophan-like component was found to be a reactive species consumer. This study revealed that the composition of DOM and the reactive species governed the rates of photo-ammonification.

溶解有机氮（DON）占水生氮总量的很大一部分。与溶解的无机氮（DIN）相比，DON的反应性受到了有限的关注。光氨化极大地促进了DON向DIN的转化。但是，有关此过程机制的信息有限。这项研究调查了不同天然地表水样品的光氨化过程。探讨了季节和降雨对该过程的影响，并确定了影响因素。结果表明，不同水样对光氨化的季节影响不同，而降雨增加了大多数湖泊的光氨化速率。反应性物质的浓度，包括发色溶解有机物的三重态（^发现3 CDOM *和单线态氧（¹ O ₂）与水光学参数显着相关。多变量线性回归分析（R ² = 0.617）显示，DON的光氨化主要由³ CDOM *促进，而¹ O ₂与³ ODOM竞争。CDOM *并显示出抑制作用。通过荧光激发发射矩阵与并行因子分析相结合，确定了溶解有机物（DOM）的组成，并发现其受位置的影响很大。发现异源腐殖质样组分促进反应性物质的产生，而色氨酸样组分是反应性物质的消费者。这项研究表明，DOM的组成和反应性物种决定着光氨化的速率。