Absorption characteristics of particulates and CDOM in spring in the Lake Xingkai

Abstract

Field surveys were carried out in the Lake Xingkai( including both the Great Lake Xingkai and the Small Lake Xingkai)in May 2013,and water samples were collected for examination of the absorption features. In the laboratory,tripton and chromophoric dissolved organic matter( CDOM) absorption of 20 water samples were measured through quantitative filter technique. Absorption coefficients were used to analyse the absorption characteristics,source,spatial distribution and relative contribution of optical active constituents over the range of PAR( 400-700 nm). The results showed that the absorption spectra of tripton are similar to nonalgal particles,indicating less phytoplankton presence in the water column. The total particulate absorption is dominated by the nonalgal particles,of which the contribution rate is up to 50% of the total absorption,and Sgis higher than that in water bodies being investigated elsewhere. Positive correlation of the particles was observed within ap( 440),ad( 440) and total suspended matter,inorganic suspended matter and organic suspended matter,respectively,while weak correlation was recorded in terms of chlorophyll-a( Chl. a) compared with results reported in literatures. In the current study,low correlations of the particles were observed within ag( 440),Chl. a and dissolve dissolved organic carbon( DOC). This is probably due to the fact that more colorless DOCs are present in the Lake Xingkai. Absorption coefficient and water quality parameters showed insignificant difference between the Great Lake Xingkai and the Small Lake Xingkai,though the latter is greatly impacted by farmland irrigation discharge,fisheries and tourism sewage.