Optical properties of dissolved organic matter in Japanese rivers and contributions to photoformation of reactive oxygen species.
Sci Total Environ
; 826: 153671, 2022 Jun 20.
Article
em En
| MEDLINE
| ID: mdl-35217053
ABSTRACT
The optical properties of dissolved organic matter (DOM) from five rivers (Kokubu, Kurose, Ohta, Yamato, and Yodo) in Japan were investigated and contributions of DOM to photoformation of three reactive oxygen species (ROS) (hydroxyl radicals (OH), nitric oxide radicals (NO), and singlet oxygen (1O2)) were assessed. The lowest and highest mean dissolved organic carbon concentrations were for the Ohta River (0.95 (mg C) L-1) and Yamato River (2.85 (mg C) L-1), respectively, and the concentrations correlated with some optical parameters. Absorption ratios (e.g., the E2E3 and A280/A350 ratios) and the spectral slope S275-295 indicated that DOM from the Yodo and Kokubu rivers had the lowest and highest molecular weights, respectively. PARAFAC models and DOM excitation-emission matrices were used to assess the sources and fates of DOM in the rivers. The PARAFAC model indicated that the main types of fluorescent DOM in the rivers were terrestrial humic-like (TH-L) and tryptophan-like (TP-L) substances. The Kokubu River contained other compounds such as fluorescent whitening agents, autochthonous humic-like substances, and extracellular polymeric substances. Statistically significant relationships between the dissolved organic carbon and TH-L, TP-L, and extracellular polymeric substance concentrations suggested that TH-L, TP-L, and extracellular polymeric substances are important contributors to total DOM in the rivers. TH-L and TP-L substances strongly contribute to ROS photoformation, but TH-L substances play roles in both ROS generation and scavenging. Comprehensive models for estimating the photoformation rates of different ROS (in M s-1) were established by integrating the contributions of the relevant major and minor sources. Examples are ROH (10-12) = 21.0 [NO2-]_µM + 0.460 [TH-L]_QSU + 10.9, RNO (10-12) = 67.9 [NO2-]_µM + 35.2 [a300]_m-1 - 2.51 [TH-L]_QSU - 0.765 [TP-L]_QSU - 8.14, and R1O2 (10-9) = 3.81 [a300]_m-1 - 0.101 [TP-L]_QSU + 11.1.
Palavras-chave
Texto completo:
1
Bases de dados:
MEDLINE
Assunto principal:
Rios
/
Matéria Orgânica Dissolvida
Tipo de estudo:
Prognostic_studies
País/Região como assunto:
Asia
Idioma:
En
Revista:
Sci Total Environ
Ano de publicação:
2022
Tipo de documento:
Article
País de afiliação:
Japão