[Spatial distribution of COD and the correlations with other parameters in the northern region of Lake Taihu].

Spatial variation of chemical oxygen demand (COD) concentration was documented and significant correlations between COD concentration and chromophoric dissolved organic matter (CDOM) absorption, fluorescence, DOC concentration were found based on a cruise sampling in the northern region of Lake Taihu in summer including 42 samplings. The possible source of COD was also discussed using every two cruise samplings in summer and winter, respectively. The COD concentration ranged from 3.77 to 7.96 mg x L(-1) with a mean value of (5.90 +/- 1.54) mg x L(-1). The mean COD concentrations in Meiliang Bay and the central lake basin were (6.93 +/- 0.89) mg x L(-1) and (4.21 +/- 0.49) mg x L(-1) respectively. A significant spatial difference was found between Meiliang Bay and the central lake basin in COD concentration, CDOM absorption coefficient, fluorescence, DOC and phytoplankton pigment concentrations, decreasing from the river mouth to inner bay, outer bay and the central lake basin. Significant correlations between COD concentration and CDOM absorption, fluorescence, DOC concentration, suggested that COD concentration could be estimated and organic pollution could be assessed using CDOM absorption retrieved from remote sensing images. Significant and positive correlation was found between COD concentration and chlorophyll a concentration in summer. However, the correlation was weak or no correlation was found in winter. Furthermore, a significant higher COD concentration was found in summer than in winter (p < 0.001). Our results indicated that degradation of phytoplankton blooms was the main source of COD in summer, except for river terrestrial input.

[Measurement of the CO2 flux on the water-air interface of Taihu Lake].

Based on the measurement of the CO2 flux on the water-air interface of Taihu Lake by closed chamber technique from January 2003 to June 2005, variation characteristics of the CO2 flux on the water-air interface in Taihu Lake are analyzed. Diurnal variation of the CO2 flux on the water-air interface is obvious. The CO2 flux is -0.79 mg/(m2 x h) in spring, -4.89 mg/(m2 x h) in summer, -4.06 mg/(m2 x h) in autumn and -2.56 mg/(m2 x h) in winter. Taihu Lake is the sink of carbon monoxide. The CO2 flux gets larger in severer polluted area of the lake. Seasonal variation is not apparent in the algae type lake, but obvious in grass type lake. It is high in summer and autumn, and low in spring and winter. Correlative factors of CO2 flux on the water-air interface of Taihu Lake possibly include weather, solar radiation, wind velocity, temperature, pH, TA, Chla, TC, TN and TP.