A preliminary study of chromophoric, dissolved organic matter (CDOM) in Lake Taihu, a shallow subtropical lake in China

The optical properties and spatial distribution of chromophoric dissolved organic matter (CDOM) in Meiliang Bay of Lake Taihu were evaluated and compared to the results in literature. Concentrations of dissolved organic carbon (DOC) ranged from 8.75 to 20.19 mg L-1 with an average of (13.10 +/- 3.51) mg L-1. CDOM absorption coefficients a(lambda) at 280 nm, 355 nm, and 440 nm were in the range 11.28...33.46 m(-1) (average (20.95 +/- 5.52) m(-1)), 2.42...7.90 m(-1) (average (4.92 +/- 1.29) m(-1)), and 0.65...2.44 m(-1) (average (1.46 +/- 0.44) m(-1)), respectively. In general, CDOM absorption coefficient and DOC concentration were found to decrease away from the river inflow to Meiliang Bay towards the lake center. The values of the DOC-specific absorption coefficients a*(lambda), given as absorption coefficient related to mass concentration of organic carbon (C) ranged from 0.28 to 0.47 L mg(-1) m(-1) at 355 nm. The determination coefficients between CDOM absorption and DOC concentration decreased with the increase of wavelength from 280 to 550 nm. The linear regression relationship between CDOM absorption at 280 nm and DOC concentration was following: a(280 nm) = 1.507 L mg(-1) m(-1) (.) DOC + 1.215 m(-1). The spectral slope S values were dependent on the wavelength range used in the regression. The estimated S values decreased with increasing wavelength range used. A significant negative linear relationship was found between CDOM absorption coefficients, DOC-specific absorption coefficients and estimated S values especially in longer wavelength range. The linear regression relationship between DOC-specific absorption coefficients at 440 nm and estimated S values during the wavelength range from 280 to 500 nm was following: a*(440 nm) = (-0.021 mu m (.) S + 0.424) L mg(-1) m(-1).