title: New insights into the source of decadal increase in chemical oxygen demand associated with dissolved organic carbon in Dianchi Lake.
abstract: Dissolved organic carbon (DOC) can be used an alternative index of water quality instead of chemical oxygen demand (COD) to reflect the organic pollution in water. The monitoring data of water quality in a long-term (1990-2013) from Dianchi Lake confirmed the increase trend of COD concentration in the lake since 2007. The similarities and differences in the DOC components between the lake and its sources and the contribution from allochthonous and autochthonous DOC to the total DOC in this lake were determined to elucidate the reason of COD increase based on C/N atomic ratios, stable isotope abundance of carbon and nitrogen, UV-visible spectroscopy, three-dimensional excitation-emission matrix (3DEEM) fluorescence spectroscopy. The terrigenous organic matter showed humic-like fluorescence, and the autochthonous organic matter showed tryptophan-like components. Agricultural runoff (9.5%), leaf litter (7.5%) and urban runoff (13.2%) were the main sources of DOC in the lake. Sewage tail was a major source of organic materials, 3DEEM for the indicates that sewage tail DOC composition did not change markedly over the biodegradation period, indicating that sewage tail contains a high load of DOC that is resistant to further biodegradation and subsequently accumulates in the lake. The change of land use in the catchment and the increase of sewage tail load into the lake are the key factors for the increase in COD concentration in Dianchi Lake. Thus, the lake should be protected by controlling the pollution from the urban nonpoint sources and refractory composition in point sources.
authors.affiliation: School of Environmental and Chemical Engineering, North China Electric Power University, Beijing, 102206, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, State Environmental Protection Key Laboratory for Lake Pollution Control, Research Center of Lake Eco-environment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, State Environmental Protection Key Laboratory for Lake Pollution Control, Research Center of Lake Eco-environment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
authors.forename: Yanping
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, State Environmental Protection Key Laboratory for Lake Pollution Control, Research Center of Lake Eco-environment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; Yunnan Key Laboratory of Pollution Process and Management of Plateau Lake Watershed, Kunming, Yunnan Province, 650034, China.. Electronic address: wangsr@craes.org.cn.
authors.forename: Shengrui
authors.initials: S
authors.lastname: Wang
mesh_terms: D057919:Biological Oxygen Demand Analysis; D002244:Carbon / Q000032:analysis*; D002681:China; D060106:Lakes / Q000737:chemistry*; D012722:Sewage; D013050:Spectrometry, Fluorescence; D014874:Water Pollutants, Chemical / Q000032:analysis*; D060753:Water Quality
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical; D002244:Carbon
keywords: Chemical demand oxygen; Dianchi Lake; Dissolved organic matter; Fluorescence spectroscopy; Land use