Response of dissolved organic matter optical properties to net inflow runoff in a large fluvial plain lake and the connecting channels

Yongqiang Zhou; Xiaolong Yao; Yunlin Zhang; Yibo Zhang; Kun Shi; Xiangming Tang; Boqiang Qin; David C Podgorski; Justin D Brookes; Erik Jeppesen

doi:10.1016/j.scitotenv.2018.05.180

Response of dissolved organic matter optical properties to net inflow runoff in a large fluvial plain lake and the connecting channels

Sci Total Environ. 2018 Oct 15:639:876-887. doi: 10.1016/j.scitotenv.2018.05.180. Epub 2018 May 26.

Authors

Yongqiang Zhou¹, Xiaolong Yao², Yunlin Zhang³, Yibo Zhang², Kun Shi⁴, Xiangming Tang⁴, Boqiang Qin⁴, David C Podgorski⁵, Justin D Brookes⁶, Erik Jeppesen⁷

Affiliations

¹ 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; University of Chinese Academy of Sciences, Beijing 100049, China; Sino-Danish Centre for Education and Research, Beijing 100190, China.
² 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; University of Chinese Academy of Sciences, Beijing 100049, China.
³ 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.
⁴ 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.
⁵ Pontchartrain Institute for Environmental Sciences, Department of Chemistry, University of New Orleans, New Orleans, 70148, LA, USA.
⁶ Water Research Centre, Environment Institute, School of Biological Science, University of Adelaide, 5005 Adelaide, Australia.
⁷ 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.

PMID: 29929326
DOI: 10.1016/j.scitotenv.2018.05.180

Abstract

Fluvial plain lake watersheds are usually highly urbanized and have high concentrations of chromophoric dissolved organic matter (CDOM). CDOM derived from the connecting urban channels usually share strong terrestrial and anthropogenic signals and net inflow runoff (Q_net) to the lake serves as a proxy of residential household sewage input. We investigate how Q_net controls the optical characteristics of CDOM in fluvial plain Lake Taihu and the connecting channels. CDOM absorption coefficient a(350), dissolved organic carbon (DOC), the fluorescence intensity (F_max) of seven PARAFAC components C1-C7, and δ¹⁵N-TDN were higher in the northwestern relative to the other lake regions, and a(250)/a(365), spectral slope S_275-295, and δ¹³C-DOM relative low in the northwestern lake, all indicating strong terrestrial and anthropogenic effects. Conversely, the urban land cover (%Cities), gross domestic product (GDP), and population density were relatively low in the western sub-watersheds and high in the eastern sub-watersheds. This apparent paradox reflects variations in Q_net from different sub-watersheds. Thus, significant positive relationships were found between Q_net and a(350), DOC, chemical oxygen demand (COD), chlorophyll-a (Chl-a), F_max of C1-C3 and C6-C7, and %C2-%C3 in the five hydraulic sub-watersheds. We revealed significant positive relationships between mean a(350), DOC, COD, Chl-a, C1-C3 and C6, %C2-%C3, and the products of Q_net × %Cities, Q_net × GDP, and Q_net × population density. We further found dominant contribution of lignin to the total number of assigned formulas for the samples collected from the channels in the Huxi watershed and the central lake using high resolution mass spectroscopy. We conclude that Q_net is of key importance for the optical properties of CDOM molecules in the various regions of Lake Taihu and the connecting channels.

Keywords: Chromophoric dissolved organic matter (CDOM); Fluvial plain lake; Net inflow runoff (Q(net)); Parallel factor analysis (PARAFAC).