[Hydrochemical Characteristics and Analysis of the Qilihai Wetland, Tianjin]

Hydrochemistry is an important parameter for wetland water environmental assessment. To study the hydrochemistry and main ion sources in the Qilihai wetland in Tianjin, river water, groundwater, and water in the marsh were collected and analyzed. The results show that:① The river and marsh waters are SO₄·Cl-Na in type and groundwater water is HCO₃-Na and HCO₃-Na·Ca in type. The water in the marshes is mainly recharged by river water and the exchange of shallow groundwater with river water is notable; ② Precipitation has little effect on the chemical composition of the water. Na⁺ and K⁺ were derived from the dissolution of salt rock and evaporative concentration. Ca²⁺, Mg²⁺, and HCO₃^- in the river and marsh water are mainly derived from the dissolution of evaporite salt rock. Ca²⁺, Mg²⁺, and HCO₃^- in the groundwater are mainly derived from carbonate mineral dissolution; ③ The hydrochemical composition of the river water and groundwater is notably affected by ion exchange, but this was not observed in the marsh water. Furthermore, SO₄^2- and NO₃^- are affected by human activity. During the dry season, the river and marsh water are affected by evaporite salt rock dissolution, evaporation, and human effects, while in wet season, river water is mainly affected by carbonate dissolution and human activities. These observations demonstrate how that hydrochemical composition of this wetland is controlled by a combination of natural factors and human activities.