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The effect of stormwater runoff on dissolved organic matter (DOM) in rivers is one of the central topics in water environment research. Jiujiang is one of the rst cities established in the Green Development Demonstration Zone of the Yangtze River Economic Belt (Jiangxi Province, China). Three-dimensional excitation-emission matrix uorescence with parallel factor analysis (3DEEM-PARAFAC) and ultravioletvisible (UV-Vis) spectroscopy were used to explore the effects of runoff on organic matter in Shili River (Jiujiang, Jiangxi Province, China). The results show that the runoff led to an increase of some critical pollutants and DOM concentrations, especially in the middle reaches of the river. The concentration and relative molecular weight of DOM in water increased as a result of runoff. Three humic-like (C1-C3) and two protein-like (C4 and C5) components of DOM were identi ed using the PARAFAC model. The sources of the three humic-like components were consistent, unlike those of the protein-like component C4. The runoff contained lower amounts of humic compounds which caused the relative content and proportion of humic substances little change and protein-like species increasing. The DOM mainly derived from autochthonous sources, and runoff had limited effect on its characteristics. The PARAFAC components could adequately represent different indicators and sources of DOM in urban rivers, providing an important reference for urban river management.

This study investigated the spatio-temporal distribution of dissolved organic matter (DOM) composition and its sources before and after degradation in the Shili River watershed in Jiujiang (China). Spatio-temporal variation of riverine DOM water samples before and after five days of degradation in a simulated channel was characterized by spectral feature analysis using three-dimensional excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis. Across all water samples (#1,#2 and #3) before and after degradation, a total of four fluorescent components in DOM were identified: C1, C2, C3, and C4. The aromaticity index (SUVA254) was negatively correlated with the C2 and C3 components and biological index (BIX) and freshness index (β:α), but it had little correlation with the humification index (HIX). The greater the aromaticity of DOM in water, the lower the proportion of recently produced DOM and its biological activity. The C3 component had a strong positive correlation with BIX, β:α, and C2. The results suggested that C2 and C3 were derived from the same substances. According to the fluorescence parameters, DOM was dominated by autochthonous contributions. The fluorescence intensity of DOM increased gradually along the direction of water flow. The increase of water temperature in spring and autumn enhanced the endogenous level of DOM. The levels and fluctuations of BIX and β:α in different seasons and different sampling points were basically consistent. DOC concentration does not fully represent the localized nature of the DOM. The analysis of some fluorescence parameters and light absorption parameters showed that the DOM source was more internal than terrestrial. This study reveals the composition, source and temporal and spatial characteristics of DOM in the Shili River Basin, which has theoretical guiding significance for water environment management.

Microcystis aeruginosa is a globally important cyanobacterial species that poses a threat to human health and development. The use of bacteria to control algal blooms has become an important research topic in recent years. In the present work, the algicidal strain G1 was isolated from sediments of a reservoir in Xi'an, China, identified by 16S ribosomal DNA (rDNA), and its algicidal effects were investigated. The rDNA sequence of G1 (GenBank accession number MW205793) is 99.86% similar to that of Chitinimonas sp., and the strain indirectly solubilised algae. Algae removal by G1 was optimal during the decay phase (algae solubilisation rate = 65.85%). Temperature (5–120 °C) did not significantly affect algae removal, pH 5–9 was tolerated, and pH 7 achieved the highest algae lysis rate (63.56%). Ultrasonic treatment of G1 destroyed the algae-solubilising effect. An injection ratio of 15% achieved the highest algae lysis rate (67.64%) under 12 h:12 h light:dark conditions, and full darkness achieved the highest algae lysis rate (68.21%). Thus, G1 can effectively inhibit the reproduction of M. aeruginosa, making it a promising biological agent for controlling algal growth.

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