Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, PR China.
School of Biomedical and Pharmaceutical Sciences, Guangdong University of Technology, Guangzhou, 510006, PR China.
Water Res. 2022 Jan 1;208:117875. doi: 10.1016/j.watres.2021.117875. Epub 2021 Nov 17.
Photochemical properties of dissolved organic matter (DOM) vary widely in natural and engineered water systems due to the different dominant compositions. However, seasonal patterns of DOM photochemical properties in urban rivers remain unclear. In this study, two seasons (wet and dry) of water samples were collected from eleven sites throughout the Pearl River (China) to investigate the spatiotemporal variability of DOM optical and photochemical properties. The optical properties of DOM in the Pearl River were characterized by UV-vis and fluorescence spectroscopies, which showed the substantial decrease in absorption coefficient and fluorescence intensity and increase in absorbence ratio (E/E) and specific absorption coefficient (SUVA) from the wet to dry season. The photochemical properties in terms of the apparent quantum yields of DOM*, O and ·OH from DOM (Φ*, Φ and Φ) under illumination also displayed a significant decrease from the wet to the dry season. Spearman's rank correlation analysis revealed the strongest relationships between Φ*, Φ and Φ and the relative abundance of microbial humic-like component (C2%) derived from parallel factor analysis (PARAFAC). Partial least squares regression (PLSR) modelling exhibited an excellent prediction strength for steady-state concentrations of O ([O]) and ·OH ([·OH]) with adjusted R values of 0.85 and 0.91, respectively, by using DOC concentration ([DOC]), optical properties, nitrate and nitrite concentrations as the response variables. In addition, the model identified that the F of humic-like component C4 (F) was the most effective predictor amongst the used response variables. This study provides an approach to describe and predict the seasonal patterns of DOM photochemical properties in urbanized rivers, offering a good understanding of the formation mechanism of reactive species from river DOM.
由于不同的主要成分，溶解有机物（DOM）在自然和工程水系统中的光化学性质差异很大。然而，城市河流中 DOM 光化学性质的季节性模式仍不清楚。在这项研究中，从珠江（中国）的 11 个地点采集了两个季节（湿季和干季）的水样，以调查 DOM 光学和光化学性质的时空变异性。珠江 DOM 的光学性质通过紫外可见分光光度法和荧光光谱法进行了表征，结果表明，从湿季到干季，吸收系数和荧光强度显著降低，吸收比（E/E）和特定吸收系数（SUVA）增加。光化学性质方面，DOM*、O 和·OH 的表观量子产率（Φ*、Φ和Φ）在光照下也从湿季到干季显著降低。Spearman 等级相关分析表明，Φ*、Φ和Φ与平行因子分析（PARAFAC）得出的微生物腐殖质样成分（C2%）的相对丰度之间存在最强的关系。偏最小二乘回归（PLSR）模型通过使用 DOC 浓度（[DOC]）、光学性质、硝酸盐和亚硝酸盐浓度作为响应变量，对 O（[O]）和·OH（[·OH]）的稳态浓度具有出色的预测强度，调整后的 R 值分别为 0.85 和 0.91。此外，该模型确定腐殖质样成分 C4 的 F 值（F）是所有使用的响应变量中最有效的预测因子。本研究提供了一种描述和预测城市化河流中 DOM 光化学性质季节性模式的方法，有助于更好地理解河流水体 DOM 中反应性物种的形成机制。
