深圳湾污染物平均输运时间数值研究

Numerical study of pollutants transit time in Deep Bay

根据粒子输运时间的定义,提出基于拉格朗日粒子示踪方法计算点污染源输运时间的方法,以深圳湾为例,计算获得稳定平均输运时间所需投放的粒子数量,有助于认识污染物在湾内的输运特性,这对海湾污染治理有重要指导作用。枯水期的计算结果表明,以深圳河口为污染源,当投放的粒子数量达到7650时,污染物平均输运时间为33.41d,其标准差为0.125d,计算结果基本稳定。当污染物从河口进入深圳湾后,湾内剩余污染物随时间呈"指数型"递减,质量减少50%、63%、80%和90%时,分别需要28.67d、33.85d、47.83d和61.79d;来自深圳河的污染物有74%通过北侧的主槽离开深圳湾,北侧是污染物排出深圳湾的主要通道。

Transit time of point source pollutants is studied using a Lagrangian particle tracking method, and the number of tracking particles for calculation of stable transit time is determined through a case study of Deep Bay. Characteristics of pollutants transport are an important factor to pollution control and management in this bay. In dry season, the results show that for the pollutants from the Shenzhen River, if the number of tracking particles is up to 7650, the transit time tends to be stable with an average of 33.41d and a standard deviation of 0.125d. After pollutants enter the bay their mass detained in the bay decays exponentially, and it takes periods of 28.67d, 33.85d, 47.83d and 61.79d for mass portions of 50%, 63%, 80% and 90% to leave the bay respectively. About 74% of the pollutants mass leaves the bay through transport in the northern main channel.