Simulated photo-degradation of dissolved organic matter in lakes revealed by three-dimensional excitation-emission matrix with regional integration and parallel factor analysis
Yingchen Bai , Jin Zhang , Fanhao Song , Tingting Li , Kefu Xie , Huiying Yao , Baoshan Xing , Zhongyu Li
DOI:10.1016/j.jes.2019.11.019
Received July 10, 2019,Revised , Accepted November 27, 2019, Available online December 18, 2019
Volume 32,2020,Pages 310-320
Simulated photo-degradation of fluorescent dissolved organic matter (FDOM) in Lake Baihua (BH) and Lake Hongfeng (HF) was investigated with three-dimensional excitation-emission matrix (3DEEM) fluorescence combined with the fluorescence regional integration (FRI), parallel factor (PARAFAC) analysis, and multi-order kinetic models. In the FRI analysis, fulvic-like and humic-like materials were the main constituents for both BH-FDOM and HF-FDOM. Four individual components were identified by use of PARAFAC analysis as humic-like components (C1), fulvic-like components (C2), protein-like components (C3) and unidentified components (C4). The maximum 3DEEM fluorescence intensity of PARAFAC components C1–C3 decreased by about 60%, 70% and 90%, respectively after photo-degradation. The multi-order kinetic model was acceptable to represent the photo-degradation of FDOM with correlation coefficient (Radj2) (0.963–0.998). The photo-degradation rate constants (kn) showed differences of three orders of magnitude, from 1.09 × 10−6 to 4.02 × 10−4 min−1, and half-life of multi-order model ( ) ranged from 5.26 to 64.01 min. The decreased values of fluorescence index (FI) and biogenic index (BI), the fact that of percent fluorescence response parameter of Region I (PI,n) showed the greatest change ratio, followed by percent fluorescence response parameter of Region II (PII,n), while the largest decrease ratio was found for C3 components, and the lowest was observed for C3, indicated preferential degradation of protein-like materials/components derived from biological sources during photo-degradation. This research on the degradation of FDOM by 3DEEM/FRI-PARAFAC would be beneficial to understanding the photo-degradation of FDOM in natural environments and accurately predicting the environmental behaviors of contaminants in the presence of FDOM.
