1 Introduction

The Earth's surface is strongly affected by chemical weathering, which also helps to control the climate on land [1]. The mineralogy, structure, and fracture density of a rock are elements that regulate how water and rocks interact [2]. Important factors include climate, biosphere, hydrodynamics, relief, and time [3]. Climate is not the only factor to consider; bedrock composition and topography have important roles in regulating the lithosphere's material transport to the aquasphere [4]. Due to the relatively slow flow rate and low clay content in most aquifers, the information on adsorption–desorption and ion exchange in natural water–rock systems may be dominated by the dissolution–precipitation of various minerals [5]. Besides dissolution–precipitation processes, relatively quick adsorption–desorption, or ion exchange between a solute and mineral can also affect the solute concentration in a water–rock system that comprises clay [6, 7]. The main reactant causing silicate weathering and carbonate dissolution is carbonic acid, which is synthesized by air reactions and the oxidation of organic materials in soils [8, 9]. As suggested by the relative chemical weathering stability in Goldich's dissolution series, evaporites weather more quickly than carbonates and silicate rocks, and ultimately, chemical resistance rocks include banded iron formations [8, 9].

The primary problem in assessing and safeguarding any water supply is water shortages in arid regions, such as eastern Egypt [10]. Numerous efforts are necessary to avoid any anticipated disasters and confrontations that could occur because of the scarce water resources in these areas [11, 12]. Because the lack of water resources could have an impact on various activities (including economics and human beings), [11, 12] In light of this, it is crucial and imperative to consider the mechanisms through which rock interactions alter groundwater and its chemistry. In the eastern part of Egypt [10], where the Red Sea Governorate receives its water either through pipes from the Nile River or by saltwater desalination [13]. A scarcity of water is the primary issue preventing the implementation of sustainable development plans [13].

The Gibbs diagram, the chloroalkaline indices, and the bivariate relationship between ions in cluster analysis are examples of statistical indicators that can assess the rock-water reaction. Numerous studies have examined interactions, including [5, 10, 14,15,16,17,18]. Assessment of interactions, some organic and inorganic contaminants, and salinization in groundwater in the northwestern Gulf of Suez, Egypt, were the main objectives of this study. While this region relies primarily on groundwater for its water supply, it is also close to the western coastal plain west of the Gulf of Suez.

2 Materials and methods

2.1 Geology of the research area

The research area in the northwestern part of the Gulf of Suez spanned between longitudes 32° 17′–32° 18′ E and latitudes 29° 37′–29° 38′ N (Fig. 1). It presents near the downstream of Wadi Ghoweiba, south of Gebel Akheider, and north of Kashm El Galala plateau on the coastal plain (Fig. 1). It included the stratigraphic succession composed of rock units ranging from Carboniferous to Quaternary (Fig. 2; [19]). Groundwater wells drilled by the Egyptian Geological Survey in 1999 have provided descriptions of the subsurface stratigraphy in the study region (Fig. 2). According to the Water Well Explanation, wadi deposits, sand, and gravel with a 4 m thickness build up the Quaternary deposits (Fig. 2; [20]). These Quaternary sediments cover the 45-m-thick Upper Miocene rocks, which are composed of calcareous sandstone and argillaceous sandstone deposits (Fig. 2; [20]). At the bottom of Wells, there is a thin layer of clay, sandstone deposits, and limestone that are all indicative of the Middle Miocene (Fig. 2; [20]). Where fresh water was accessible in the aquifers, which were formed of sandstone that was 40 m thick and whose depth varied from 15 to 40 m (Fig. 2; [20]). The environmental conditions in the area under investigation are characterized by high aridity, with temperatures reaching their maximum in the summer and ranging between 45 and 50 °C [20]. The annual rainfall is less than 150 mm/year, which indicates that the area is prone to drought and water scarcity [20]. Additionally, the rate of potential evaporation varies between 2.1 mm/day in the winter and 9.2 mm/day in the summer, which means that the area experiences high rates of water loss through evaporation [20].

Fig. 1
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Location map of the study area

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Fig. 2
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Geologic map and subsurface cross section of the study area

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2.2 . Sampling and analysis

From wells in the northwest Gulf of Suez of the research area, 12 groundwater samples were collected in July 2021 (Fig. 1). After being filtered and acidified with nitric acid (pH < 2; [21]), the collected samples were stored in tightly sealed, pre-rinsed polypropylene bottles. Electric conductivity (EC), total dissolved solids (TDS), and pH were all recorded in situ using the pH meter. The main ions contained in the water samples under investigation were examined at laboratories of the National Water Research Center (NWRC), where the ionic balance error (e%) for the measured ions was less than 5%.

2.3 Methodology

The concentrations of the groundwater samples show the various kinds of water on Piper's diagram [22, 23]. According to the Canadian Council's Water Quality Index (CCWQI) is used to establish the water's suitability for human consumption [24]. Phreeqc Interactive version No. 3.4 was implemented to compute the saturation index (SI) values for the dissolved minerals [17]. The positive value explicates the super-saturation, and the negative value construes the under-saturation [25]. The concentration is measured in epm, and the chloro-alkaline indices (CAI) are calculated using the following equations: Eqs. (1) and (2).

$${\text{CAI}}_{1} = [{\text{Cl}} - \left( {{\text{Na}} + {\text{K}}} \right)]/{\text{Cl}}$$
(1)
$${\text{CAI}}_{2} = [{\text{Cl}} - \left( {{\text{Na}} + {\text{K}}} \right)]/\left( {{\text{SO}}_{4} + {\text{HCO}}_{3} + {\text{CO}}_{3} } \right)$$
(2)

Positive numbers highlight the host rock's alkaline ions (Ca + Mg) and the groundwater's alkali (Na + K) exchange ions [26]. The negative numbers, however, reflect the reverse exchange ion that leads to excessive alkalinity in water [26]. Negative numbers also signify the recharge from rainfall that seeps into wells [17, 27].

The Gibbs diagram's (GD) attributes are hydrogeochemical processes, which control the water's chemistry [17, 28]. These processes, such as chemical weathering, dissolution, and precipitation, depict how rocks and water interact [17, 28, 29]. The ratios of GA and GC are estimated using the following Eqs. (3) and (4), where the units of measurement are epm.

$${\text{G}}_{{\text{C}}} = {\text{Na}}/({\text{Na}} + {\text{Ca}})$$
(3)
$${\text{G}}_{{\text{A}}} = {\text{Cl}}/({\text{Cl}}^{ - } + {\text{HCO}}_{3} )$$
(4)

The corrosion susceptibility of groundwater is determined by the corrosivity ratio (CR) [30, 31]. Equation (5) used to compute CR has a concentration measured in ppm [29, 30].

$${\text{CR}} = \left( {{\text{Cl}} + {\text{SO}}_{4} } \right)/2\left( {{\text{HCO}}_{3}^{ - } + {\text{CO}}_{3} } \right)$$
(5)

Revelle index (RI) appraises the salinization process [32]. Salinization has an impact on groundwater with RI values of over 0.5 [33]. RI is computed from the subsequent Eq. (6), whereas the contents of ions are recorded in epm [32].

$${\text{RI}} = {\text{Cl}}/\left( {{\text{HCO}}_{3} + {\text{CO}}_{3} } \right)$$
(6)

3 Result and discussion

3.1 Major ions chemistry and trace element

In water samples, the pH ranged from 7.03 to 7.93, indicating neutral to slightly alkaline water (Table 1; [34]). Water samples with EC values between 5310 and 10,300 µS/cm were determined to be excessively mineralized (Table 1; [35]). This is referring to those waters that are unsafe to utilize for irrigation because their values are higher than the acceptable limit, which is 2250 µS/cm (Table 1; [36]). TDS levels above 3000 ppm, however, indicated that all water samples were highly saline (Table 1; [37]), a result of coastal groundwater interaction, dissolution, and saline water intrusion [17, 38]. In water samples with TH values of more than 300 ppm, the water was very hard (Table 1; [39]). According to their concentrations, the constituents of water samples can be sorted into the following order: Cl > Na > SO4 > HCO3 > Ca > NO3 > Mg > K (Table 1).

Table 1 Physico-chemical variables and indices in the investigated water samples
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In water, biologically active substances exist as urea, COD, and N-compounds [40,41,42]. Due to the oxidation of bacteria and organic waste, these chemicals are thought to be a major source of water contamination [40,41,42]. These pollutants may result from urban human activities, including the use of fertilizers and sewage water that has leaked into the ground [43]. One of the N-compounds, NO2, mixes with water during the disintegration of organic waste and was measured in the samples under study in concentrations of 1–6 ppm (Table 1). Also, another ion released by the disintegration of N-compounds is NH3 [34], which fluctuated between 8 and 110 ppm in the examined samples (Table 1). COD vacillated between 25 and 161 ppm, and it was becoming increasingly unfavorable for agricultural and drinking purposes [44]. Over 10 ppm of urea in high doses of water can damage the kidneys, interfere with cholinergic and bioenergetic functions, and raise neuronal activity and visceral structure [45, 46].

The chemical weathering process that disintegrates the silicate minerals in rock and sediment releases SiO2, which is the main source of dissolved silica in natural waterways [47, 48]. In water samples, it was measured between 21 and 29.5 ppm (Table 1). One of the planet's most plentiful resources is iron [34, 49]. Rainwater seeps into the earth and dissolves iron in the underlying geologic formations and soil, which allows it to penetrate aquifers and become a source of iron (Fe) in the groundwater [34, 49]. It graded between 0.03 and 0.12 ppm in the water samples (Table 1). Al builds up around 8% of the Earth's crust and is the most common metallic element [42]. Its salts are commonly utilized as coagulants in water treatment to lessen levels of organic matter, color, turbidity, and microbes [42]. Extensive exposure to water polluted with aluminum has adverse effects on the immune system, nervous system, kidneys, bones, and kidneys [42]. In water samples, it ranged from 0.01 to 0.91 ppm (Table 1). Ba compounds are found in igneous and sedimentary rocks, mining deposits, and industrial applications, besides human activities [42]. Acute exposure to Ba-polluted water might cause hypertension, hypotension, weak muscles, and paralysis [42]. In the examined water, it varied between 0.14 and 0.15 ppm (Table 1). B is typically prevalent in groundwater because of leaching from rocks and soils that contain borates and borosilicate's, as well as recharge from sewage [42]. The stomach, intestines, liver, kidney, brain, and other organs can all be harmed by repeated exposure to water that is contaminated with B, which can ultimately cause death [42]. Its content varied from 0.01 to 0.12 ppm in water samples (Table 1). Sr may be present in water from the environment due to human activity or related phenomena such as weathering of the rock and soil [50]. It is a carcinogenic chemical that builds up in the body because of acute exposures, can harm the bones, and causes cancer and cardiovascular toxicity [50]. It was estimated between 15 and 25 ppm (Table 1), which was higher than the maximum allowable concentration (MAC is 7 ppm) [50].

In addition, all principal ions in the water samples exceeded the Maximum Allowable Concentrations (MAC) for drinking water according to WHO (Table 1; [42]), excluding NO2, Urea, Fe, Ba, and B (Table 1). Due to silicate weathering, mineral dissolving, seawater incursion, and human activity, these high concentrations are explained [17, 38]. As a result, the water under study is unfit to drink. According to Piper's diagram, the types of waters that were analyzed were SO4. Ca–Cl (90% of samples), and SO4. Na–Cl (10% of samples; Fig. 3); [22, 23]. Furthermore, WQI and USSL charts verified that water samples are unfit for use in irrigation and drinking (Fig. 4).

Fig. 3
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Piper's diagram interprets different water types of the studied samples (after Bai et al. [23])

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Fig. 4
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WQI and USSL charts for water samples classification

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3.2 Saturation index (SI)

SI values depict the level of water saturation with different dissolved minerals because groundwater interacts with host rocks [17, 25]. Carbonate minerals (aragonite, calcite, and dolomite), silicate minerals (albite, alunite, anorthite, montmorillonite, kaolinite, illite, quartz, and talc), evaporite minerals (anhydrite, barite, gypsum, halite, and sylvite), and iron oxides (hematite) are among the dissolved minerals in the water under research (Fig. 5). Apart from sylvite minerals, all water samples are super-saturated with carbonate, silicate, hematite, and evaporite minerals, which have positive SI values (Table 1 and Fig. 5). This is referring to the tendency of all minerals that have been over-saturated with water to precipitate [17, 25]. As water becomes more heavily saturated with dissolved minerals, TDS rises. This can be confirmed by statistically significant positive relationships between major elements and TDS, except for Mg and NO3 ions (r = −0.8 and −0.6, respectively; Table 2). Aside from the dendrogram graph, which demonstrates that TDS was associated with all excessively saturated minerals in water samples and major ions apart from Mg and NO3 in cluster 1 (Fig. 6).

Fig. 5
figure 5

SI values of the dissolved minerals in the studied water samples

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Table 2 Correlation matrix between the variables of water samples
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Fig. 6
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Dendrogram and factor analysis for the studied water samples

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3.3 Chloro-alkaline indices (CAI)

The CAI illustrated the ion exchange between the cations in the groundwater and the cations linked to the solid components of the host rocks [16, 17, 26, 51, 52]. According to the CAI indices, which yielded positive value readings, the groundwater contained ion exchange between alkalis (Na and K) and Ca and Mg, which were connected to clay minerals or organic substances (Table 1 and Fig. 7; [16, 17, 26, 51, 52]). A reverse ion exchange that led to a rise in the Na content of the groundwater samples is what caused the negative values, which indicated a partial rainy recharge (Fig. 7; [17, 27, 53]). Elevated levels of HCO3, Na, and Cl ions in groundwater are primarily due to sewage water recharge and seawater incursion [17, 38]. This is verified by the strong positive relationships between Na and HCO3, Cl, and SO4 (Table 2), where the corresponding values are r = 0.7, 0.9, and 0.5. (Table 2), Also, they are linked in cluster 1 of the dendrogram graph (Fig. 6).

Fig. 7
figure 7

Chloro-alkaline indices for the water samples

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3.4 Gibbs diagram (GD) and end-member diagram (EMD)

According to GD, precipitation, along with rock weathering dominance and evaporation, is a major factor that can control the chemistry of groundwater [28, 29]. GD depicted that evaporation is the predominant process represented in the water samples (Fig. 8). EMD revealed that silicate weathering is more prevalent than evaporite dissolving (Fig. 9). The abundance of Cl, Na, and SO4 in groundwater due to silicate weathering and evaporate dissolving proves this [3, 17, 54, 55]. This is reinforced by the dendrogram graph's cluster 1 and the considerable positive correlations between Cl and all the main ions apart from Mg (r = −0.8; Table 2 and Fig. 6).

Fig. 8
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Gibbs diagram for the water samples

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Fig. 9
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End-member diagram for the water samples

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3.5 Corrosivity ratio (CR)

Incrustation is the term for calcium carbonate or silicate precipitating on metals, whereas corrosion is a chemical process that dissolves metals [30]. The sensitivity of groundwater to corrosion is defined as CR [30, 31]. It varied from 2.08 to 3.86 in all water samples, exceeding the acceptable limit, which is less than 1 (Table 1; [31]). Because of this, it is hazardous to transport water over long distances in steel pipes for various uses. It caused a scale of deposits on the inner surface of the pipe, which moved into the water and attracted heavy metals like Sr, which formed reactive sinks [56]. These sinks developed because of variations in physical and hydraulic conditions, unstable water chemistry, and/or the mobilization of heavy metals, which are considered water pollutants [56].

3.6 Salinization

Seawater invasion generates salinization in most coastal wells [38]. Salinization influenced the studied water, as evidenced by the Revelle index (RI) values, which varied between 4.25 and 9.39 and were greater than 0.5 [33]. HFED illustrated that three wells No. 6, 8, and 9 were subjected to salinization due to seawater incursion (Fig. 8). This is alluding to the fact that the recharges of the researched water were primarily made up of sewage water, followed by rainwater and seawater in aquifers, which became salty (Fig. 10).

Fig. 10
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HFED for the examined water

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3.7 Land use–land cover (LU–LC) changes

The land change would affect groundwater quality geographically and seasonally [57]. Exceeding water pumping of wells is required for the agricultural reclaimed projects, which lowers the water table level by 42 m [58]. LU–LC can change the amount, quality, and depletion of water, as it proved in the UAE [59, 60]. Egypt's population, which only occupies a small patch of arable land (3.4% of its total size), is increasing faster than the country's ability to produce enough food to satisfy its demands. Unfortunately, according to information gathered from a 2022 satellite map using the arc map tool, the study area is classified as an industrial area and does not contain any agricultural land other than trees (Fig. 11).

Fig. 11
figure 11

LU–LC for the investigated area in 2022

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4 Conclusion

The salinity of the water samples was highly saline, with a pH range of neutral to slightly alkaline, excessive mineralization, and severe hardness. Water samples were deemed offensive for irrigation because their EC levels were higher than the safe limit (2250 S/cm). Apart from NO2, urea, Fe, Ba, and B, all detected constituents in water samples exceeded the MAC set by the WHO for drinking water. Water interaction with the bedrock was a result of silicate weathering and evaporation dissolution. Due to the weathering of silicate minerals and the dissolution of evaporite minerals, Cl, Na, and SO4 have a dominant presence in water.

Piper's graph revealed that 90% of the water is Ca–Cl and 10% is SO4. Na–Cl. silicate, carbonate, and evaporite minerals, excluding halite and sylvite, were oversaturated in the examined water, according to SI values. Ion exchange between alkaline earths (calcium and magnesium) connected to solids and alkalis (sodium and potassium) in waters, as well as reverse exchange, was emphasized by CAI indices. The reverse exchange caused a Na surplus in the water and indicated a partial recharging of the rainwater. GD clarified the silicate weathering and evaporite dissolution processes that predominated the interaction between the host rocks and the groundwater. According to EMD, the main causes of the excess Cl, Na, and SO4 observed in water samples are the processes of silicate weathering and evaporite dissolving, seawater incursion, and wastewater recharges. The dendrogram's outcomes provided evidence that silicate weathering and evaporite dissolution are the main factors controlling the composition and salinity of groundwater. Because groundwater is immensely vulnerable to corrosion, CR implied that groundwater circulation through metallic pipelines is perilous over longer distances. Three wells were adversely affected by seawater incursions, which salinized their waters. The research area's water is of poor quality for drinking and agricultural purposes and could even be harmful. A result of excessive doses of Sr metal availability in the water, which reflected a more hazardous condition due to its salinity, excessive NH3, and high vulnerability to corrosion.