中文摘要：

为了探讨珠江三角洲西江磨刀门水道枯季咸淡水混合特征与水体二氧化碳分压变化的关系,2006年12月18日沿磨刀门水道实测了36个样点表层水体的理化参数。采用相关分析和曲线拟合的方法,分析了表层水体二氧化碳分压的分布特征,结果表明,水体二氧化碳分压值介于147364 Pa,平均值为201 Pa,随航距呈现出复杂多变的减小趋势,其复杂突变发生在航距2438 km（即盐度36）内。分析认为,咸淡水混合及其潮汐冲刷作用影响了理化参数的时空变化,控制着河流碳的生物地球化学行为。

英文摘要：

To study the relationship between the salt freshwater mixing characteristics and the variations of the partial pressure of carbon dioxide,some physicochemical parameters were measured for the 36 field water samples collected from different positions along the Modao Gate waterway of the Xijiang River inner estuary in the Zhujiang River Delta zone in the drought season in 2006.The spatial variation characteristic of the partial pressure of carbon dioxide in the surface water was analyzed by means of correlation analysis and curve fit.The analytical results show that the variation of the partial pressure of carbon dioxide,with a range of 147 to 364 Pa,and an average 201 Pa,has a decreasing tendency with a striking variational labilization ranged between 24 and 38 km channel which corresponds to the salinity of 3～6 along the Modao Gate waterway.The biogeochemistry behaviors of the riverine carbon were controlled by the spatio-temporal variation of physicochemical parameters which were influenced by the estuarine tide-mixing action.