title: Inflow rate-driven changes in the composition and dynamics of chromophoric dissolved organic matter in a large drinking water lake.
abstract: Drinking water lakes are threatened globally and therefore in need of protection. To date, few studies have been carried out to investigate how the composition and dynamics of chromophoric dissolved organic matter (CDOM) in drinking water lakes are influenced by inflow rate. Such CDOM can lead to unpleasant taste and odor of the water and produce undesirable disinfection byproducts during drinking water treatment. We studied the drinking water Lake Qiandao, China, and found that the concentrations of suspended particulate matter (SPM) in the lake increased significantly with inflow rate (p < 0.001). Similarly, close relationships between inflow rate and the CDOM absorption coefficient at 350 nm a(350) and with terrestrial humic-like fluorescence C3 and a negative relationship between inflow rate and the first principal component (PC1) scores, which, in turn, were negatively related to the concentrations and relative molecular size of CDOM (p < 0.001), i.e. the concentration and molecular size of CDOM entering the lake increased proportionately with inflow rate. Furthermore, stable isotopes (δD and δ(18)O) were depleted in the upstream river mouth relative to downstream remaining lake regions, substantiating that riverine CDOM entering the lake was probably driven by inflow rate. This was further underpinned by remarkably higher mean chlorophyll-a and in situ measured terrestrial CDOM fluorescence (365/480 nm) and apparent oxygen utilization (AOU), and notably lower mean PC1 and CDOM spectral slope (S275-295) recorded in the upstream river mouth than in the downstream main lake area. Strong negative correlations between inflow rate and a(250):a(365), S275-295, and the spectral slope ratio (SR) implied that CDOM input to the lake in rainy period was dominated by larger organic molecules with a more humic-like character. Rainy period, especially rainstorm events, therefore poses a risk to drinking water safety and requires higher removal efficiency of CDOM during drinking water treatment processes.
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; Sino-Danish Centre for Education and Research, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China. Electronic address: ylzhang@niglas.ac.cn.
authors.forename: Yunlin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Sino-Danish Centre for Education and Research, Beijing 100190, China; Department of Bioscience and Arctic Research Centre, Aarhus University, Vejlsøvej 25, DK-8600 Silkeborg, Denmark.
authors.forename: Erik
authors.initials: E
authors.lastname: Jeppesen
authors.affiliation: Chalmers University of Technology, Water Environment Technology, Gothenburg 41296, Sweden.
authors.forename: Kathleen R
authors.initials: KR
authors.lastname: Murphy
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Shi
authors.affiliation: Institute of Environmental Protection Science, Hangzhou 310014, China.
authors.forename: Mingliang
authors.initials: M
authors.lastname: Liu
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; Sino-Danish Centre for Education and Research, Beijing 100190, China.
authors.forename: Xiaohan
authors.initials: X
authors.lastname: Liu
authors.affiliation: Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
authors.forename: Guangwei
authors.initials: G
authors.lastname: Zhu
mesh_terms: D060766:Drinking Water; D004784:Environmental Monitoring; D060106:Lakes; D045483:Rivers; D013050:Spectrometry, Fluorescence
chemical_list: D060766:Drinking Water
keywords: Chromophoric dissolved organic matter (CDOM); Drinking water; Inflow rate; Lake Qiandao; Parallel factor analysis (PARAFAC)