title: UV-induced photochemical heterogeneity of dissolved and attached organic matter associated with cyanobacterial blooms in a eutrophic freshwater lake.
abstract: Cyanobacterial blooms represent a significant ecological and human health problem worldwide. In aquatic environments, cyanobacterial blooms are actually surrounded by dissolved organic matter (DOM) and attached organic matter (AOM) that bind with algal cells. In this study, DOM and AOM fractionated from blooming cyanobacteria in a eutrophic freshwater lake (Lake Taihu, China) were irradiated with a polychromatic UV lamp, and the photochemical heterogeneity was investigated using fluorescence excitation-emission matrix (EEM)-parallel factor (PARAFAC) analysis and synchronous fluorescence (SF)-two dimensional correlation spectroscopy (2DCOS). It was shown that a 6-day UV irradiation caused more pronounced mineralization for DOM than AOM (59.7% vs. 41.9%). The EEM-PARAFAC analysis identified one tyrosine-, one humic-, and two tryptophan-like components in both DOM and AOM, and high component photodegradation rates were observed for DOM versus AOM (k > 0.554 vs. <0.519). Moreover, SF-2DCOS found that the photodegradation of organic matters followed the sequence of tyrosine-like > humic-like > tryptophan-like substances. Humic-like substances promoted the indirect photochemical reactions, and were responsible for the higher photochemical rate for DOM. The lower photodegradation of AOM benefited the integrality of cells in cyanobacterial blooms against the negative impact of UV irradiation. Therefore, the photochemical behavior of organic matter was related to the adaptation of enhanced-duration cyanobacterial blooms in aquatic environments.
authors.affiliation: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, 73 East Beijing Road, Nanjing 210008, China; State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
authors.forename: Huacheng
authors.initials: H
authors.lastname: Xu
authors.forename: Helong
authors.initials: H
authors.lastname: Jiang
mesh_terms: D002681:China; D000458:Cyanobacteria / Q000737:chemistry*; D005068:Eutrophication / Q000528:radiation effects*; D005163:Factor Analysis, Statistical; D006801:Humans; D007700:Kinetics; D060106:Lakes / Q000737:chemistry* / Q000382:microbiology*; D009930:Organic Chemicals / Q000032:analysis*; D010100:Oxygen / Q000032:analysis; D055668:Photochemical Processes / Q000528:radiation effects*; D010782:Photolysis / Q000528:radiation effects; D012995:Solubility; D013050:Spectrometry, Fluorescence; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D009930:Organic Chemicals; D010100:Oxygen
keywords: Attached organic matter (AOM); Cyanobacterial blooms; Dissolved organic matter (DOM); Photodegradation