Fluorescence peak integration ratio IC:ITas a new potential indicator tracing the compositional changes in chromophoric dissolved organic matter.
The present study demonstrates that the ratio of fluorescence integration of peak C to peak T (IC:IT) can be used as an indicator tracing the compositional dynamics of chromophoric dissolved organic matter (CDOM). CDOM absorption and fluorescence spectroscopy and stable isotope δ13C were determined on a seasonal basis in seventeen Chinese inland waters as well as in a series of mixing and photodegradation experiments in the lab. A strong positive linear correlation was recorded between IC:ITand the ratio of terrestrial humic-like C1 to tryptophan-like C4 (C1:C4) derived by parallel factor analysis. The r2for the linear fitting between IC:ITand C1:C4 (r2=0.80) was notably higher than between C1:C4 and other indices tested, including the ratio of CDOM absorption at 250nm to 365nm, i.e. a(250):a(365) (r2=0.09), spectral slope (S275-295) (r2=0.26), spectral slope ratio (SR) (r2=0.31), the humification index (HIX) (r2=0.47), the recent autochthonous biological contribution index (BIX) (r2=0.27), and a fluorescence index (FI370) (r2=0.07). IC:ITexhibited larger variability than the remaining six indices and a closer correlation with stable isotope δ13C than that observed for a(250):a(365), S275-295, SR, FI370, and BIX during field campaigns. Confirming our field observations, significant correlations were recorded between IC:ITand the remaining six indices, and IC:ITalso demonstrated notably larger variability than the six other indices during our wastewater addition experiment. Compared with HIX, eutrophic water addition and photobleaching substantially decreased IC:ITbut had no pronounced effect on a(250):a(365), S275-297, SR, FI370, and BIX, further suggesting that IC:ITis the most efficient indicator of the CDOM compositional dynamics.
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.
Yongqiang
Y
Zhou
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.
Kun
K
Shi
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.
Yunlin
Y
Zhang
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.
Erik
E
Jeppesen
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.
Xiaohan
X
Liu
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; Yunnan Key Laboratory of Pollution Process and Management of Plateau Lake-Watershed, Yunnan Institute of Environmental Science, Kunming 650034, China.
Qichao
Q
Zhou
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.
Huawu
H
Wu
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.
Xiangming
X
Tang
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.
Guangwei
G
Zhu
Chromophoric dissolved organic matter (CDOM); Fluorescence peak integration; Parallel factor (PARAFAC) analysis; Photobleaching