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

Abstract

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.

Vertical and spatial evaluation of the groundwater chemistry in the Central Nile Delta Quaternary aquifer to assess the effects of human activities and seawater intrusion

“…Soil water samples showed Na/Cl values higher than unity, where sodium addition in the soil zone was one of the main hydrochemical processes through mineral weathering and ion exchange processes (Bouderbala and Gharbi, 2017;Zhang et al, 2020). The Ca/Mg ratio for seawater = 0.25; therefore, it can be used for tracing contamination by seawater (Salem and El-Horiny, 2014;Barzegar et al, 2016;Hussien and Faiyad, 2016). The Ca/Mg ratio of the groundwater samples ranged from 0.07 to 4.25, with a mean value of 1.75, indicating the enrichment of Ca, which is an indicator of seawater intrusion (Panno et al, 2006).…”

“…Most samples of shallow (84%), intermediate (67%), and deep groundwater (89.5%) had a Ca/Mg ratio higher than unity (Table 5 and Figure 18B), reflecting the dissolution of calcium-rich minerals and leaching of gypsum in the aquifer matrix (Ibrahim et al, 2021). In addition, the rest of the samples in the three zones had a Ca/Mg ratio lower than unity (Table 5), which might indicate the ion exchange and/or precipitation of carbonates (Salem and El-Horiny, 2014;Ibrahim et al, 2021). Correlation coefficients (r) of calcium-magnesium relationships were 0.37, 0.69, and 0.65 for the shallow, intermediate, and deep groundwater, respectively (Table 4), suggesting different origins of both Ca and Mg. High values of this ratio may indicate the dissolution of gypsum, anhydrite, and calcite; surface water mixing; and/or CO 2 -CaCO 3 interaction.…”

“…The plotted samples (Figure 18D) are distributed on the scatter plot of SO 4 versus Ca with no definite trend, where r = 0.33 for the shallow, 0.37 for the intermediate, and 0.32 for the deep groundwater (Table 4). As soil water was matched with the groundwater, the low SO 4 /Ca ratio indicates that the addition of calcium occurred by the dissolution of Carich minerals more than gypsum (Kumar et al, 2009;Salem and El-horiny, 2014;Salem et al, 2015).…”

“…Besides, about 78% and 53% of the intermediate groundwater samples and 87% and 97% of the deep groundwater samples have the Ca/HCO 3 and Mg/HCO 3 ratios less than unity, respectively (Table 5). Such trends and ratios suggest that the freshwater origin, dissolution of dolomite and calcite, rock weathering, and ion exchange of Ca and Mg with Na are the possible sources responsible for the dissolved carbonates and such low values of the ratios Ca/HCO 3 and Mg/HCO 3 recorded (Kumar et al, 2009;Salem and El-horiny, 2014;Salem et al, 2015).…”

Hydrogeochemical and geophysical investigations to delineate underground water aquifer in arid regions: A case study, Gara oasis, Egypt

“…Hierarchical clustering is the most widely used in environmental sciences, according to Davis (1986) and Salem et al (2015), and is regularly used in the organization of hydrogeochemical data. Using hierarchical cluster analysis, CA is used to categories estimated groundwater properties into groups or clusters depending on their similarity or differences that exist in data set variations (Abdel-Gawad et al, 2020;Salem and Osman, 2017;Salem and El-Horiny, 2014). When two items belong to the same group, their point of connection is maximum; otherwise, it is minimum.…”