三峡水库正常蓄水后长江口海域营养盐分布与结构变化

Changes of Distributions and Compositions of Nutrients in the Changjiang Estuary After Normal Operation of the Three Gorges Reservoir

根据2010-2011年对长江口及其邻近海域的调查资料,研究了三峡水库正常蓄水后长江口及其邻近海域营养盐的分布变化特征,并与三峡大坝合拢蓄水前的2002年同期数据进行了比较。结果表明,与三峡大坝合拢蓄水前相比,三峡水库正常蓄水后长江口海域溶解无机氮、无机磷含量显著增大,且无机磷含量增幅更大(60%),但活性硅酸盐含量显著降低(20%),并由此导致长江口海域N/P比值明显降低和Si/N比值的大幅度降低。此外,三峡水库秋季蓄水活动造成的入海径流量的减少,导致该季节长江冲淡水扩展范围和营养盐浓度及影响范围显著减小。

Based on the field observations in the Changjiang Estuary and its adjacent sea areas in 2010-- 2011, changes of distributions and compositions of nutrients in the Changjiang Estuary were studied after normal operation of the Three Gorges Reservoir. By comparison with the field data in 2002 before closure of the Three Gorges Dam, it was found that the concentrations of dissolved inorganic nitrogen and phos- phate increased by 27% and 60%, respectively, while dissolved silicate decreased by 20% in the Changjiang Estuary and its adjacent sea areas after the normal operation of the Three Gorges Reservoir. The changes in nutrient concentrations resulted in a significant decrease of N/P ratio as well as substantial decrease of Si/N ratio in the Changjiang Estuary. Besides, the reduction of freshwater discharge from the Changjiang in autumn, which was resulted by filling of the Three Gorges Reservoir, led to a significant re- duction in the range of extension of the Changjiang Diluted Water and concentrations of nutrients as well as their affecting areas in the Changjiang Estuary and its adjacent sea areas.