天津七里海湿地水体的同位素和水化学特征

Isotopics and Hydrochemical Characteristics of Water in Qilihai Wetlands,Tianjin

为了研究天津七里海湿地水体及其周边水体的水化学和同位素特征,2015年8月10~12日和12月5~7日采集了湿地内的沼泽水、潮白新河水、永定新河水和周边地下水水样,分析水样的稳定氢、氧同位素和水化学组成。结果表明,无论是在8月采样日还是在12月采样日,沼泽水的电导率都比附近的河水高;河水和沼泽水的水化学类型为Na-Cl,地下水的水化学类型为Na-HCO_3。天津七里海湿地的沼泽水和河水的水化学组成主要受控于蒸发结晶作用和人类活动,而地下水中的离子含量与岩石风化有关。8月采样日和12月采样日,沼泽水和河水的同位素组成富集,存在明显的变化;地下水的同位素组成贫化,年内变化小。潮白新河附近的沼泽水同位素组成与河水接近。沼泽水在8月采样日受到强烈的蒸发作用,其过量氘值小于12月采样日。潮白新河上的水闸对河水的同位素和水化学有直接影响,进而影响湿地水质。此外,在高含盐量的土壤环境下,七里海湿地的沼泽水中Na^+和Cl^-含量增加,可能导致水体盐分积累。

The research on hydrochemical and stable isotopic characteristics of water in Qilihai wetlands is essential for the sustainable protection on the wetland. We sampled the river water in the Chaobaixin, Yongdingxin River, groundwater, and water in the marshes during 10-12, August, and during 5-7, December in 2015, respectively. The electrical conductivity, p H and water temperature were measured in the field. The compositions of stable isotopes of hydrogen and oxygen and major ions in water were determined. The results showed that the electrical conductivity of water in the marshes was larger than that of river water both on sampling days in August and in December. The river water and water in the marshes samples were Na-Cl type, and groundwater was Na-HCO3 type. The hydrochemical compositions of river water and water in the marshes were mainly controlled by evaporation crystallization and human activities. The major ions in groundwater were dominated by rock weathering. The water in the marshes and river water were isotopic enriched, and the isotopic composition of water in the marshes and river water varied between sampling days in August and December. The groundwater was isotopic depleted, and there was little variation of isotopes in groundwater from sampling days in August to sampling days in December. The stable isotopic composition of water in the marshes was similar to the river water near the wetland. As the evaporation of wetland on sampling days in August was stronger than that on sampling days in Decenber, the value of deuterium excess value on sampling days in August was less than that on sampling days in December. Moreover, the gates in the Chaobaixin River had directly impact on the isotopic and hydrochemical composition of river water. Further, the water in the marshes in the wetland may be affected by the gates. Since the salt content in soil was high, the concentrations of sodium and chloride would increase in water in the marshes. This may cause the saline issue of water in the marshes.