典型河口区低溶解氧现象及形成机理研究——以鳌江为例

Preliminary Study on Low DO Phenomenon and Formation Mechanism in Typical Estuary Area——Take Aojiang River as an Example

鳌江口是我国东海沿岸典型涌潮河口,近年来其水质有机指标得到了明显改善,但低溶解氧(低氧)现象仍然存在。研究分析了鳌江河口区DO历史变化趋势及潮周期内垂向分布特征,探讨低氧现象形成机理。结果表明,鳌江河口区低氧现象为物理及生化过程综合作用的结果,主要原因为底层异重流导致的水体分层限制了表层与底层水体的交换和复氧,生化耗氧过程(尤其是底泥耗氧)则进一步加剧了低氧程度。

Aojiang estuary is a typical estuary of tidal bore along the southeast coastal region of China.The organic indicators of Aojiang estuary has been significantly improved in recent years, but the low dissolved oxygen (DO) phenomenon still exists.The historical trend of DO and its vertical distribution during tidal period in Aojiang estuary were studied and the formation mechanism was discussed.The results showed that the low DO phenomenon in Aojiang estuary is the result of the combined effects of physical and biochemical processes.The stratification of water bodies were caused by the sediment heterogeneous flow at the bottom, and it restricted the exchange of hyperoxic water at the surface with hypoxic water at the bottom.Moreover, biochemical oxygen consumption process(especially the oxygen consumption of bottom sediment) further aggravated the low DO degree.