ABSTRACT

Zeng, W., 2018. Analysis on change characteristics of soluble silica in shallow groundwater of coastal area caused by seawater intrusion. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 282–286. Coconut Creek (Florida), ISSN 0749-0208.

Seawater intrusion is a kind of geological hazard that has strong potential, of highly harmful and is hard to be eliminated in a short period of time. It has seriously threatened the survival and development of human beings, especially those living in the coastal areas. The change of seawater intrusion in Dalian is taken as an example, continuous sampling and chemical experiments are performed on shallow groundwater in three different areas around Dalian City, and the change trend of characteristic of soluble SiO2. The results show that the groundwater in this area is mostly of Na-Cl type and alkaline, and is a transitional type of weathered leaching and evaporation. The soluble SiO2 content in groundwater is 57.56–75.41 mg / L, and the content of SiO2 fluctuates slightly depending on the surrounding environmental conditions. The fluctuation is caused by mineral dissolution, seawater intrusion and water-rock interactions on its path. The content of soluble SiO2 in the water of a single test point at the same time fluctuates as well, and the change in different periods of time is also more obvious. The soluble SiO2 dominates in the form of monomolecular orthosilicic acid, and all kinds of silicates present dissolved, saturated and equilibrium states, and the states transform into each other. The single factor analysis is used to evaluate the content of soluble SiO2 and metal ions in groundwater. The groundwater affected by seawater intrusion in Dalian is analyzed, and the comprehensive evaluation of recent shallow groundwater quality in Dalian is carried out. The total dissolved solids, total hardness, chlorides, sulfates and other indicators are selected as the evaluation criteria, and the comprehensive evaluation and analysis of the characteristics of soluble SiO2 and quality of groundwater in Dalian are performed using fuzzy set which is based on entropy weight and analysis and evaluation method. According to the overall research results, the proportion of saturated mineral species in groundwater in Dalian is relatively high. Therefore, groundwater in the coastal area, as an open system of transition between land and sea, can promote the dissolution of different minerals and the saturated decomposition of water bodies.

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