Temporal and spatial variations of chemical oxygen demand in Lake Taihu,China, from 2005 to 2009 |
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Authors: | Yan Yin Yunlin Zhang Xiaohan Liu Guangwei Zhu Boqianq Qin Zhiqiang Shi Longqing Feng |
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Institution: | (1) Taihu Lake Laboratory Ecosystem Research Station, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China;(2) Graduate University of Chinese Academy of Sciences, Beijing, 100049, China; |
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Abstract: | We undertook a study in Lake Taihu, China, from 2005 to 2009 including a total of 639 samples to determine: (i) the seasonal
dynamics and spatial distribution of the chemical oxygen demand (COD) and (ii) the relationships between the COD concentration
and the biochemical oxygen demand (BOD), phytoplankton pigment, total dissolved nitrogen (TDN), and total dissolved phosphorus
(TDP) concentrations, as well as the chromophoric dissolved organic matter (CDOM) absorption coefficient. There were significant
spatial differences in the COD concentration, which gradually decreased from Zhushan Bay in the northwest, to the north, the
lake center, and the southeast of the lake. The COD concentration was significantly higher at near-shore sites than that at
open water sites. The mean COD concentrations were significantly higher in the spring and summer than in the winter and autumn.
The lowest annual mean COD concentration appeared in 2009, which could be attributed to improvements in water quality management
and high rainfall. The COD concentrations in all four seasons were strongly correlated with phytoplankton pigment, suggesting
that extracellular release of COD from phytoplankton was an important COD source. The correlation coefficients between the
COD and phytoplankton pigment concentrations were higher in the spring, summer, and autumn than in the winter, showing a more
important contribution of phytoplankton degradation to COD in the algal bloom season than in the non-algal bloom season. These
new data on the temporal and spatial characteristics of the COD in Lake Taihu will be crucial for developing future strategies
for water quality management. |
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