Lin Hui, Bartlett Sarah L, Guo Laodong
School of Freshwater Sciences, University of Wisconsin-Milwaukee, 600 E. Greenfield Ave., Milwaukee, WI 53204, USA; Polar Research Institute of China, 1000 Xuelong Road, Pudong, Shanghai 201209, China.
NEW Water/Green Bay Metropolitan Sewerage District, 2231 N. Quincy Street, Green Bay, WI 54302, USA.
Sci Total Environ. 2023 Dec 1;902:165891. doi: 10.1016/j.scitotenv.2023.165891. Epub 2023 Aug 5.
Variations in molecular weight distributions of dissolved organic matter (DOM) and PARAFAC-derived fluorescent components were investigated along a transect in the seasonally hypereutrophic lower Fox River-Green Bay using the one-sample PARAFAC approach coupling flow field-flow fractionation for size-separation with fluorescence excitation-emission matrix (EEM) and PARAFAC analysis. Concentrations of dissolved organic carbon and nitrogen, chromophoric-DOM, specific UV absorbance at 254 nm, and humification index all decreased monotonically from river to open bay, showing a strong river-dominated DOM source and a dynamic change in DOM quality along the river-lake transect. The relative abundance of colloidal DOM (>1 kDa) derived from ultrafiltration exhibited minimal variation, averaging 71 ± 4 % of the bulk DOM, across the entire estuarine transect although the colloidal concentration decreased in general. Using the one-sample EEM-PARAFAC approach, the identified major fluorescent components were distinct between stations along the river-estuary-open bay continuum, with four components in river/upper-estuary but three components in open bay waters. Among the four common fluorescent components (C, C, C and C), the most abundant and refractory humic-like component, C, behaved conservatively and its relative abundance (%ΣF) remained fairly constant (50 ± 4 %) along the transect, while the semi-labile humic-like component, C, consistently decreased from river to estuary and eventually vanished in open Green Bay. In contrast, the two autochthonous protein-like components (C and C) increased from river to open bay along the trophic gradient. The new results presented here provide an improved understanding of the diverse and fluctuating characteristics in DOM composition, lability, and estuarine mixing behavior across the river-lake interface and demonstrate the efficacy of the one-sample PARAFAC approach.
利用单样本平行因子分析方法，结合用于尺寸分离的流场-流分馏技术、荧光激发-发射矩阵（EEM）和平行因子分析，沿着季节性富营养化的福克斯河下游-绿湾的断面，研究了溶解有机物（DOM）分子量分布和PARAFAC衍生荧光组分的变化。溶解有机碳和氮、发色DOM、254nm处的比紫外吸光度和腐殖化指数的浓度从河流到开阔海湾均单调下降，表明DOM来源以河流为主，且沿河湖断面DOM质量存在动态变化。尽管胶体浓度总体上有所下降，但通过超滤得到的胶体DOM（>1kDa）的相对丰度在整个河口断面变化极小，平均占总DOM的71±4%。使用单样本EEM-PARAFAC方法，在河流-河口-开阔海湾连续区域内，各站点间识别出的主要荧光组分各不相同，河流/河口上游有四个组分，而开阔海湾水域有三个组分。在四个常见的荧光组分（C1、C2、C3和C4）中，含量最丰富且最难降解的类腐殖质组分C1表现保守，其相对丰度（%ΣF）沿断面保持相当恒定（50±4%），而半不稳定的类腐殖质组分C2从河流到河口持续下降，最终在开阔的绿湾消失。相反，两种自生源类蛋白质组分（C3和C4）沿营养梯度从河流到开阔海湾增加。本文给出的新结果有助于更好地理解跨河湖界面DOM组成、稳定性和河口混合行为的多样且波动的特征，并证明了单样本PARAFAC方法的有效性。
