[Fluorescence Characteristics and Influencing Factors of Dissolved Organic Matter (DOM) in Water and Sediment of Urban Watershed: A Case Study of Xiaojia River in Ningbo City].

Rapid urbanization has a significant impact on dissolved organic matter (DOM) in water and sediment; thus, it is important to explore the distribution characteristics and influencing factors of DOM in watersheds. Xiaojia River is a typical urban area in Beilun District of Ningbo City, Yangtze River Delta. The spectral characteristics of DOM in the water and sediment in this river were studied to examine their sources and characteristics. The DOM was analyzed by three-dimensional fluorescence spectroscopy (EEM) coupled with the parallel factor analysis (PARAFAC) model. The following results were noted. ① Four fluorescence DOM components were derived by EEM-PARAFAC:C1 represents terrestrial humus with a high molecular weight; C2 represents terrestrial humus with a low molecular weight, which was produced by biodegradation; C3 represents protein-like substances that were sensitive in a microenvironment; and C4 is terrestrial humus. ② Both new-born endogenous and terrestrial sources have large impacts on DOM components. The humification degree was very weak with a low concentration of humus. The DOM in the sediments was derived mainly from terrestrial or soil sources with small endogenous contribution with high humification. The concentration of humus in the sediments was significantly higher than that in water. ③ Redundancy analysis (RDA) showed that farmland and urban land use were the dominant environmental factors and had relatively high correlation with the water indicators. Construction land, farmland, and wetland land use positively correlated with the sediment components. Among them, urban land use had the greatest influence on the concentration parameter Fn(355) of humus-like substance C4 and the humus-like substance in sediments.

[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.

[Characteristics of Dissolved Organic Matter (DOM) and Relationship with Dissolved Heavy Metals in a Peri-urban and an Urban River].

Dissolved organic matter (DOM) is ubiquitous in the aquatic environment, playing an important role in the fate of heavy metals in aquatic systems. In this study, we characterized the DOM and heavy metals and their distribution in a peri-urban river and an urban river in Ningbo city. In addition, the relationship between DOM and dissolved heavy metals was also determined. Results showed that higher DOC, CDOM, and FDOM concentrations were found in the river with the higher urbanization level. Four fluorescence peaks were identified in the excitation-emission matrix (EEM) of DOM, including fulvic acid-like fluorescence peaks A and C and protein-like fluorescence peaks B and T. The higher fluorescence intensities of peak B and T were found in the urban river, and similar trends were also found for the degree of humification and aromaticity of DOM. Similarly, concentrations of heavy metals, such as As, Cu, and Mn, were significantly higher in the urban river. Moreover, DOM had significant positive correlations with Cu, Cr, Mn, As, Zn, and Pb in the urban river, while DOM only exhibited significant positive correlations with Mn, Pb, and Cu in the peri-urban river. In conclusion, urbanization level influenced the characteristics and concentrations of CDOM in rivers which were closely related to the distribution of heavy metals.

Draft Genome Sequence of Desulfitobacterium hafniense Strain DH, a Sulfate-Reducing Bacterium Isolated from Paddy Soils.

Desulfitobacterium hafniense strain DH is a sulfate-reducing species. Here, we report the draft genome sequence of strain DH, with a size of 5,368,588 bp, average G+C content of 47.48%, and 5,296 predicted protein-coding sequences.