深圳大沙河河水与海水关系的水文化学识别

Hydrochemistry recognization of the relationship between seawater and Dasha river water of Shenzhen

为了解深圳沿岸河口处海水与河水的混合关系,在大沙河下游靠近河口段密集取17件河水样,依据其水化学数据,分析了主要离子Ca、Mg、Na、K、SO4、HCO3与Cl的关系,Br与Cl的关系以及piper三线图解,在研究区河段从上游至入海口,对河水样品有如下认识:(1)上游4个样品(Cl<100mg/L)接受降水和地下水的补给;(2)4个样品(150mg/L<Cl<1500mg/L)受人类活动的污染影响;(3)橡胶坝上游3个样品(1500mg/L<Cl<4000mg/L)处于海水与污染水的过渡带;(4)橡胶坝下游6个样品(Cl浓度5000～10000mg/L左右)是海水与淡水的混合。

In order to study the mixing relationship between seawater and surface water on the coast of Shenzhen, 17 river water samples were collected near the estuary in the downstream of the Dasha river which disembogue into the sea. According to the hydrochemistry data, the relationships of major ions （ Ca^2＋ ,Mg^2＋ , Na^＋ ,K^＋ ,SO4^2- ,HCO3^- ） vs. Cl^- , Br^- vs. Cl^- and the piper diagram were analyzed. The river water data in comparison with seawater dilution lines in the scatter diagrams are divided into four groups： （ 1 ） 6 samples with salinities around 5 000 - 10 000 mg/L Cl^- , explained by the mixing of seawater with fresh water in downstream of rubber-dam; （2） 4 samples with salinities lower than 100 mg/L Cl^-, recharged by precipitation and groundwater in the upstream; （3） 4 samples with salinities around 150 - 1500mg/L Cl^- , resulted from anthropogenic contamination along the river; （4） 3 samples with salinities around 1 500 - 4 000mg/L Cl^- , characterized by the transition zone between polluted river water and seawater.