Absorption characteristics and source analysis of the CDOM in Dongping Lake
YAO Xin1,2, LÜ Wei-wei2, LIU Yan-long2, ZHANG Bao-hua2, GAO Guang1
1. Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China;
2. School of Environment and Planning, University of Liaocheng, Liaocheng 252000, China
To investigate the chromophoric dissolved organic matter (CDOM) absorption characteristics, sources and spatial-temporal patterns in Dongping Lake, 35surface water samples were collected in August and December of 2013 and March of 2014, respectively. The water quality parameters, spatial distribution of the CDOM absorption coefficient at 440nm, carbon-specific CDOM absorption coefficient[a*(440)], the value of relative molecular size M, as well as the relationships between the CDOM and water quality parameters were studied. The[a(440)] exhibited that the seasonal pattern was dry season > wet season > level period. The spatial distributions were similar to that of[a*(440)]. The value of relative molecular size M exhibited that the seasonal pattern followed:dry season > level period > wet season. Significant correlation was found between the CDOM absorption coefficient and Chla in wet period. The correlation between CDOM absorption coefficient and DOC in both wet season and level period is also significant. In wet season, the CDOM was affected by both exogenous and endogenous inputs and endogenous input dominanted the CDOM pool, which mainly came from phytoplankton degradation products. The exogenous characteristics in the area of Laohu Town were obvious. In level period, the CDOM was affected by both exogenous and endogenous inputs, however, the degradation of phytoplankton was not the main source of the CDOM. The CDOM in the Northern lake was dominanted by exogenous input. In dry season, the CDOM was mainly affected by endogenous input, and the degradation of phytoplankton was not the main source of the CDOM. It was speculated that its autogenetic characteristics may be related to the increase of suspended matter caused by dredging activities. The Southeast lake showed strong exogenous characteristics which was influenced by Dawen River. Inferring the concentration of DOC by the CDOM concentration was somehow feasible in the wet season and level period in Dongping Lake.
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