Soil salinization affected by hydrogeochemical processes of shallow groundwater in Cangzhou City, a coastal region in North China

Abstract

Abstract This study sought to further the current understanding on the relationship between soil salinization and groundwater hydrochemical processes. To this effect, 33 soil samples and 64 shallow groundwater samples were collected in Cangzhou City, a coastal region of the North China Plain. Soil salinization showed clear patterns of zonation from inland to coastal areas. The no-salinization or mild-salinization with Cl-SO4 or SO4-Cl types were discovered in the west of Cang County farther from the sea; this was restricted by brackish groundwater with HCO3·SO4-Ca·Na type and the deep water table. With increasing proximity to the coastline, groundwater salinity increased soil salt content and salinization, the effects of which were mainly determined by specific Cl/Br ratios and the seawater mixing index in groundwater. The positive δ18O and δ2H content in groundwater was related to the strong evaporation of groundwater with a shallow water table, indicating that the high soil salinity directly affected relict seawater evaporation. The observed severe-salinization soil and high NO3− concentrations indicate that agricultural activities were non-negligible salt sources in areas close to the sea. The results have relevance in improving saline-alkali soil and utilization of soil resources in the coastal areas in the North China Plain.