珠江三角洲地下咸水形成的水化学证据

Hydrochemical evidences of saline groundwater genesis in the Pearl River delta area

珠江三角洲地下咸水分布广泛。迄今仅在珠江三角洲局部地段进行了地下咸水有关的研究,因而对区域性地下咸水成因的认识缺乏。利用近10年来有关水工环地质调查项目获得的67个水文地质钻孔的水化学分析资料,进行了珠江三角洲平原地下咸水水化学的总体特征、水文地球化学参数及特征指标关系研究,探讨了区域性地下咸水成因与影响因素。研究结果表明,地下咸水水化学特征总体上与海水较为一致;地下咸水起源于古海水,主要形成于中全新世海侵期,与退积作用关系密切;地下咸水形成过程中,水循环交替慢,水动力条件不良;地下咸水中的盐分主要来源于古海水及海相沉积物,沉积压实、矿物溶解与离子交换等作用可能造成盐分的富集。

Saline groundwater widely occurs in the Pearl River delta area. Researches related to saline groundwater have been carried out in limited locations up to now and the genesis of the regional saline groundwater is lack of understanding. The overall hydrochemical characteristics,hydrogeochemical parameter properties and characteristic index relationship of the saline groundwater are examined,and the regional saline groundwater formation and influencing factors are discussed in this paper,using hydrochemical data obtained from 67 hydogeological boreholes drilled in the implementation of relative hydrogelogical,engineering geolocial and environmental-geilogical projects in the past 10 years. The results indicate that hydrochemical characteristics of the saline groundwater is comparatively unanimous to seawater and the saline groundwater originated from paleo-seawater. The saline groundwater mainly formed in the middle Holocene transgression period and is closely related to retrogradation. The water cycle was slow and hydrodynamic conditions were undesirable during the formation of the saline groundwater. The sources of salinity in the saline groundwater are paleo-seawater and marine sediments,and sedimentary compaction,mineral dissolution and ion exchange may contribute the enrichment of salinity.