CNRS, IRD, MIO, Université de Toulon, Aix Marseille Univ, CS 60584, 83041, Toulon Cedex 9, France.
Department of Environmental and Earth Sciences, Faculty of Science, The Islamic University-Gaza, P.O Box 108, 00970, Gaza, Gaza Strip, Palestine.
Environ Sci Pollut Res Int. 2020 Jun;27(18):23141-23158. doi: 10.1007/s11356-020-08842-w. Epub 2020 Apr 24.
Anthropogenic effluent dissolved organic matter (DOM) plays an important role in coastal zone pollution. The objectives of the present study were to characterize the fluorescence signal of anthropogenic effluent DOM from wastewater treatment plant and to evaluate the effect of solar irradiation on the fluorescence signal in the coastal zone. Solar irradiation experiments were conducted to evaluate the effect photochemical degradation using excitation-emission matrix (EEM) method combined with parallel factor analysis (PARAFAC). Results showed high fluorescence of DOM before irradiation and the intensity tends to decrease after 4th and 15th day of irradiation. Rapid photochemical degradation of humic-like fluorophores and appearance of a post-irradiance dominant anthropogenic effluent DOM fluorophores were also observed after irradiation. Our experiments showed a sharp reduction in fluorescence intensity which occurred after 4th day of solar irradiation and the fluorescence signal did not disappeared after 15th day indicating the formation of a specific signal due to solar irradiation. PARAFAC model divided the bulk EEM spectra into three individual fluorescent components with C1 "terrestrial humic-like" and C2 "humic-like of longer wavelength" and C3 is a noisy component with two emission maxima. Multilinear regression of PARAFAC components contribution with mixing composition was most suitable according to the equation Ci = A + A.f + A.f, where C is the normalized contribution of PARAFAC component number i in a given irradiation day; A, A, A are the multilinear regression coefficients and contain implicitly the effect of f; and WW, SW, and RW are treated wastewater, sea water, and river water respectively. The values of A, A, and A fitted second-order kinetics with irradiation process with kinetic constant of 9.68, - 987.35, and - 977.67 respectively for C1 equation and the same trend for C2 and no values for C3 due to its noisy character indicating the rapid degradation with increase of f and f and the predominance of the residual fluorescence coming from f which is the content fraction of anthropogenic effluent DOM because A was 100 times less sensitive to photobleaching. A suitable model for predicting the fluorescence EEMs as a function of mixing composition was developed.
人为污水 DOM 对沿海地区污染起着重要作用。本研究旨在分析污水处理厂 DOM 的荧光信号特征，以及评估太阳辐射对沿海地区 DOM 荧光信号的影响。采用激发-发射矩阵（EEM）法结合平行因子分析（PARAFAC）对太阳辐射实验进行了评估。结果表明，辐照前 DOM 具有较高的荧光强度，辐照 4 天和 15 天后强度趋于降低。辐照后还观察到类腐殖质荧光团的快速光化学降解和后辐照主导的人为污水 DOM 荧光团的出现。我们的实验表明，在太阳辐照 4 天后，荧光强度急剧下降，在 15 天后，荧光信号并未消失，表明由于太阳辐射形成了特定的信号。PARAFAC 模型将 EEM 光谱分为三个单独的荧光成分，C1 为“陆源腐殖质样”，C2 为“更长波长的腐殖质样”，C3 为含有两个发射峰的噪声成分。根据方程 Ci = A + A.f + A.f，PARAFAC 成分贡献与混合成分的多线性回归最适合，其中 C为给定辐照日 PARAFAC 成分数的归一化贡献；A、A 和 A 是多线性回归系数，隐含着 f 的影响；WW、SW 和 RW 分别为处理废水、海水和河水。根据辐照过程拟合二阶动力学，C1 方程的 A、A 和 A 的拟合值分别为 9.68、-987.35 和-977.67，C2 也呈现出相同的趋势，而 C3 由于噪声特征，其值为零，表明随着 f 和 f 的增加，快速降解，f 产生的残余荧光占主导地位，这是人为污水 DOM 的含量分数，因为 A 对光漂白的敏感性要低 100 倍。建立了一个合适的模型，可以预测作为混合成分函数的荧光 EEM。
