Hydrogeochemical evaluation of calcareous eolianite aquifer with saline soil in a semiarid area

The aim of this study is to evaluate the groundwater geochemistry in Burg Elarab area as an example of a calcareous eolianite aquifer that is covered with saline soil in a semiarid climatic condition. To conduct this study, 37 groundwater samples were taped from the production wells in addition to two surface water samples from Mallahet Mariut Lake and Bahig Canal. To elucidate the origin of dissolved ions and the geochemical processes influencing this groundwater, combinations of geomorphological, pedological, hydrogeological, hydrochemical, and statistical approaches were considered. Results suggest that the groundwater flows from both sides of the plain to the central area. Soil type and salinity and the intruded brackish lake water are the main factors controlling the groundwater chemistry. Chemically, the groundwater samples were classified into three groups. Group 1 samples have higher salinity range and characterize the area close to Mallahet Mariut and are influenced by cation exchange processes. Group 2 samples have an intermediate salinity range, occupy most of the plain area, and receive water from direct infiltrations and mixing between different recharge sources. Group 3 samples have low salinity range and limited areal extent and characterize the groundwater flowing from the Mariut Tableland. Reverse ion exchange is the predominant process in the latter group. Calcite precipitation is a general phenomenon characterizing all the groundwater types in the study area.