Environment-specific fluorescence probe for investigating the detection mechanism of nitric oxide in lakes.

As a highly active trace gas in the atmosphere, nitric oxide (NO) significantly affects the air quality. Additionally, NO plays a key role in lake eutrophication. Therefore, establishing a method for the rapid monitoring of NO emissions from lakes is essential. Detecting NO in water bodies presents challenges, including disruption of in-situ conditions, low temporal resolution, susceptibility to interference from complex water matrices, and insufficient long-term stability. Currently, high temporal and spatial resolution, anti-interference, and convenient detection techniques for lake environments are lacking. This study proposes, for the first time, the evaluation of NO distribution in lakes using small-molecule fluorescent probe (LR-P) technology, which detects NO through fluorescence changes. A multivariate linear parameterization of fluorescence quantum yield and fluorescence intensity against NO concentration was developed (R2=0.729, p < 0.001). Additionally, the abundance of NO-producing microbes containing nitrifying genes (amoA AOA and amoA AOB) and denitrifying genes (nirS, nirK, and nosZ genes) was significantly correlated with fluorescence quantum yield, suggesting that LR-P could detect NO and related microbial abundances in natural lakes. This study presents a rapid and convenient method for analyzing NO distribution and the abundance of NO-related functional genes in lakes. The integration of fluorescence technology with molecular methods offers a novel approach for NO detection in natural water bodies, providing new insights into the nitrogen cycle in lakes.