[Fluorescent Dissolved Organic Matter and Its Correlation with Water Quality in a Urban River: A Case Study of the Lujiang River in Beilun, Ningbo].

Excitation-emission matrix fluorescence spectroscopy combined with fluorescence regional integration (FRI) analysis were adopted to analyze the water samples collected from the Lujiang River, which flows through the rapidly urbanizing areas of Beilun, Ningbo, in order to illuminate the composition and characteristics of the spatial distribution of fluorescent dissolved organic matter (FDOM), and further to explain its correlation with water quality in the urban river. The results showed that FDOM was composed of tyrosine-like, tryptophan-like, soluble microbial by-product-like, fulvic-like, and humic-like materials, and FDOM was dominated by protein-like components, accounting for 83.8% of the total fluorescence intensity, while humic-like components accounted for much less. The concentrations of the water quality parameters, such as total nitrogen, total phosphorus, and metals, were linearly correlated with the total fluorescence intensity of all components, indicating that FDOM was significantly related to the removal and transformation of nitrogen and phosphorus. The distribution of FDOM in different areas has the following characteristics:FDOM was low and not distinctly influenced by human activities in the upstream, while in the downstream, FDOM was high and showed the characteristics typical of that in urbanized rivers. Therefore, anthropogenic activities can greatly influence river water quality and the concentration and composition of FDOM.