Iraqi Geological

Abstract


Introduction
The suitability of groundwater for various uses is mostly determined by its quality, which is determined by its chemistry; thus, studying groundwater chemistry is an essential part of groundwater management and conservation (Bonì et al., 2022;Liu et al., 2022).Published water chemistry research has shown that the chemical composition of groundwater varies greatly locally and temporally.Moreover, it has become clear that there are major factors that control this, the most important of which are the Water-rock interactions, geological conditions, climate and topography, vegetation cover, water residence time, and anthropogenic factors (Liu et al., 2021;Paternoster et al., 2021;Sahraei Parizi and Samani, 2013;Umar Kura et al., 2013;Wang et al., 2022;Zainol et al., 2021).The relative abundance of elements in water is determined by the abundance of the particular element in the earth's crust and the element's ability to mobile and enter the aquatic environment (Gaillardet et al., 2003).

s determined
y its chemistry; thus, studying groundwater chemistry is an essential part of groundwater management and conservation (Bonì et al., 2022;Liu et al., 2022).Published water chemistry research has shown that the chemical composition of groundwater varies greatly locally and temporally.Moreover, it has become clear that there are major factors that control this, the most important of which are the Water-rock interactions, geological conditions, climate and topography, vegetation cover, water residence time, and anthropogenic factors (Liu et al., 2021;Paternoster et al., 2021;Sahraei Parizi and Samani, 2013;Umar Kura et al., 2013;Wang et al., 2022;Zainol et al., 2021).The relative abundance of elements in water is determined by the abundance of the particular element in the earth's crust and the element's ability to mobile and enter the aquatic environment (Gaillardet et al., 2003).

As a result of the rocks-water interaction, the chemistry of groundwater closely reflects the mineral compos As a result of the rocks-water interaction, the chemistry of groundwater closely reflects the mineral composition of the rocks that flow through it (Elanqo and Kannan, 2007).Although evaporation, precipitation, and human impacts can all alter the chemical composition of groundwater, the interaction between rocks and water is the primary process influencing the chemistry of the major ions in water, as the solid phases are the main sources and sinks of dissolved ions in groundwater (Chenini et al., 2015;Elanqo and Kannan, 2007;Qian et al., 2016).A wide range of chemical reactions occurs between solid phases and groundwater as they move along their path from recharge to discharge area.Ion water content differs temporally and spatially, based on the chemistry of the source water, residence time, and geological formations (Apodaca et al., 2002).The groundwater content of major ions can be used to determine the intensity of interactions between rocks and water, as well as the most important hydrochemical processes that influence groundwater chemistry and the most important mineral sources of major ions, and thus conclude the type of rock components of the aquifer (Khattab et al., 2021).Furthermore, new studies reveal that water chemistry can be utilized to predict groundwater flow patterns (Dragon, 2021;Xia et al., 2022).
tion of the rocks that flow through it (Elanqo and Kannan, 2007).Although evaporation, precipitation, and human impacts can all alter the chemical composition of groundwater, the interaction between rocks and water is the primary process influencing the chemistry of the major ions in water, as the solid phases are the main sources and sinks of dissolved ions in groundwater (Chenini et al., 2015;Elanqo and Kannan, 2007;Qian et al., 2016).A wide range of chemical reactions occurs between solid phases and groundwater as they move along their path from recharge to discharge area.Ion water content differs temporally and spatially, based on the chemistry of the source water, residence time, and geological formations (Apodaca et al., 2002).The groundwater content of major ions can be used to determine the intensity of interactions between rocks and water, as well as the most important hydrochemical processes that influence groundwater chemistry and the most important mineral sources of major ions, and thus conclude the type of rock components of the aquifer (Khattab et al., 2021).Furthermore, new studies reveal that water chemistry can be utilized to predict groundwater flow patterns (Dragon, 2021;Xia et al., 2022).

Due to the availability of significant areas of agricultural land that lack the presence of surface water sources Due to the availability of significant areas of agricultural land that lack the presence of surface water sources, there has been a growing tendency to utilize groundwater in different areas of Nineveh Governorate to profit from this water in various fields, particularly irrigation.Especially since the rise of the issue of water security and future concerns in light of the construction of Turkish dams.However, this activity occurred at random and without any planning or control to conserve groundwater.This resulted in the emergence of some issues related to water quality and its significant variation, even among wells located in the same area (Al-Nuaimy, 2010).The current research area, which is located 50 km northwest of Mosul and is represented by agricultural fields in the Wana region, is an example of this.With the exception of Al-Nuaimy study (2010), which was conducted on a limited portion of the current study area and demonstrated that the Tigris River is the main source of recharge for groundwater in the region and that agricultural activities pollute the water of some wells, the study area lacks hydrochemical and hydrogeological studies.Based on this, the current study aims to investigate the hydrochemistry of groundwater in the Wana region, identify the most important factors controlling the groundwater content of major ions, and attempt to identify the water-producing layers as well as the key causes of the region's significant locational variation in groundwater chemistry.
there has been a growing tendency to utilize groundwater in different areas of Nineveh Governorate to profit from this water in various fields, particularly irrigation.Especially since the rise of the issue of water security and future concerns in light of the construction of Turkish dams.However, this activity occurred at random and without any planning or control to conserve groundwater.This resulted in the emergence of some issues related to water quality and its significant variation, even among wells located in the same area (Al-Nuaimy, 2010).The current research area, which is located 50 km northwest of Mosul and is represented by agricultural fields in the Wana region, is an example of this.With the exception of Al-Nuaimy study (2010), which was conducted on a limited portion of the current study area and demonstrated that the Tigris River is the main source of recharge for groundwater in the region and that agricultural activities pollute the water of some wells, the study area lacks hydrochemical and hydrogeological studies.Based on this, the current study aims to investigate the hydrochemistry of groundwater in the Wana region, identify the most important factors controlling the groundwater content of major ions, and attempt to identify the water-producing layers as well as the key causes of the region's significant locational variation in groundwater chemistry.


Study Area


Geographical Location

The Wana district is located about 50 km northwest of Mosul and has an area of abo

Geographical Location
The Wana district is located about 50 km northwest of Mosul and has an area of about 281 km 2 .It is located between longitudes 43.010674 -42.762157 and latitudes 36.512208 -36.576743.Mosul Dam Lake borders it to the north, and the Tigris River borders it to the south and west.Suggesting that the groundwater in this area is of good quality (Fig. 1).

is located between lo
gitudes 43.010674 -42.762157 and latitudes 36.512208 -36.576743.Mosul Dam Lake borders it to the north, and the Tigris River borders it to the south and west.Suggesting that the groundwater in this area is of good quality (Fig. 1).


Climate and Geology

The study region has a semi-arid climate with hot dry summers and cold winters, with an annual avera

Climate and Geology
The study region has a semi-arid climate with hot dry summers and cold winters, with an annual average of around 380 mm of rain in winter, with peak temperatures in July (44°C) and the lowest average monthly temperature in January (6 °C) (World Weather, 2021).

of around 380 mm of
rain in winter, with peak temperatures in July (44°C) and the lowest average monthly temperature in January (6 °C) (World Weather, 2021).

Geologically, the study area consists of sediments and sedimentary rocks of the middle Miocene and Quaternary periods.The Geologically, the study area consists of sediments and sedimentary rocks of the middle Miocene and Quaternary periods.The middle Miocene deposits are represented by the Fatha (Lower Fars) Formation, which is a succession of mudstone, marl, limestone, and gypsum.Quaternary deposits include slope sediments, residual soils, river terraces, and floodplain sediments (Fig. 2).
iddle Miocene deposits are represented by the Fatha (Lower Fars) Formation, which is a succession of mudstone, marl, limestone, and gypsum.Quaternary deposits include slope sediments, residual soils, river terraces, and floodplain sediments (Fig. 2).


Fig. 1. Location of selected wells in the study area


Materials and Methods


1. Sampling and Analysis

Thirty-six groundwat

1. Sampling and Analysis
Thirty-six groundwater samples were taken from 18 selected wells in the study area (Fig. 1): 18 samples in October 2020 (dry season) and 18 samples in April 2021 (wet season).A portable Multiparameter (Hanna Instruments HI 9829) was used to measure the electrical conductivity (EC), pH, and total dissolved solids (TDS).Water samples were taken after pumping water to approximate the stability of electrical conductivity measurements.For sample collection, 0.5-liter polyethylene bottles were used.A 0.45 µm membrane was used to filter the samples in the field.and then transported to the laboratory, where total hardness (TH.) and Cl -, HCO3 -, Ca 2+ and Mg 2+ was measured using titration methods, NO3 -, SO4 2-were analyzed using a spectrophotometer, and Na + , K + were analyzed using a flame photometer.All measurements were made at the central laboratory of the College of Agriculture and Forestry at the University of Mosul.The data's accuracy was confirmed by the Charge Balance Error, which was less than 10%, indicating the data's reliability for hydrochemical interpretations (Domenico and Schwartz, 1990;Hossain and Patra, 2020;Matthess, 1982).

18 selected wells in the
study area (Fig. 1): 18 samples in October 2020 (dry season) and 18 samples in April 2021 (wet season).A portable Multiparameter (Hanna Instruments HI 9829) was used to measure the electrical conductivity (EC), pH, and total dissolved solids (TDS).Water samples were taken after pumping water to approximate the stability of electrical conductivity measurements.For sample collection, 0.5-liter polyethylene bottles were used.A 0.45 µm membrane was used to filter the samples in the field.and then transported to the laboratory, where total hardness (TH.) and Cl -, HCO3 -, Ca 2+ and Mg 2+ was measured using titration methods, NO3 -, SO4 2-were analyzed using a spectrophotometer, and Na + , K + were analyzed using a flame photometer.All measurements were made at the central laboratory of the College of Agriculture and Forestry at the University of Mosul.The data's accuracy was confirmed by the Charge Balance Error, which was less than 10%, indicating the data's reliability for hydrochemical interpretations (Domenico and Schwartz, 1990;Hossain and Patra, 2020;Matthess, 1982).


Saturation and Chloro-Alkaline Indices

The Saturation Index (SI) is an indica

Saturation and Chloro-Alkaline Indices
The Saturation Index (SI) is an indicator widely used in hydrogeochemical research, and it is calculated using the following formula: SI = log10

r widely used in hydrogeochemical resea
ch, and it is calculated using the following formula: SI = log10

(1)


A B

Where: SI = Saturation Index; Kiap = ion activity product (1)

A B
Where: SI = Saturation Index; Kiap = ion activity product; Ksp = Solubility Product of the mineral at a given temperature.When SI = 0, the mineral is in equilibrium; when SI < 0, the mineral is unsaturated in the solute and continues to dissolve; and when SI > 0, the mineral is saturated in the solute, resulting in crystallization and precipitation (Li et al., 2010).The Chloro-Alkaline Index (CAI) was calculated using the following equations: ubil

y Pr
duct of the mineral at a given temperature.When SI = 0, the mineral is in equilibrium; when SI < 0, the mineral is unsaturated in the solute and continues to dissolve; and when SI > 0, the mineral is saturated in the solute, resulting in crystallization and precipitation (Li et al., 2010).The Chloro-Alkaline Index (CAI) was calculated using the following equations:

(2)

(3)

Positive CAI indices suggest that Na + and K + in water are exchanged (2) (3) Positive CAI indices suggest that Na + and K + in water are exchanged with Ca 2+ and Mg 2+ within the sediments and rocks of the water-bearing layers, indicating a direct ion exchange.Negative CAI indices values suggest that Ca 2+ and Mg 2+ in the water exchange with Na + and K + within the sediments and rocks of the water-bearing layers, implying a reverse ion exchange. ith a 2+ and Mg 2+ within the sediments and rocks of the water-bearing layers, indicating a direct ion exchange.Negative CAI indices values suggest that Ca 2+ and Mg 2+ in the water exchange with Na + and K + within the sediments and rocks of the water-bearing layers, implying a reverse ion exchange.


Statistical Analysis

The physicochemical data of the study samples were an

Statistical Analysis
The physicochemical data of the study samples were analyzed using the statistical program SPSS version 20.Technics including Principal Component Analysis (PCA) and Cluster Analysis (CA) was used to find potential factors or sources influencing groundwater hydrochemistry.PCA is a statistical method commonly used in dealing with raw data to extract fewer variables that are more obvious and useful in explaining the main factors affecting water's hydrochemistry (Nazzal et al., 2015;Ravikumar and Somashekar, 2017).To better understand PCA results, it is preferable to use other traditional methods such as scatter plots (Karimi et al., 2019).

yzed using the statis
ical program SPSS version 20.Technics including Principal Component Analysis (PCA) and Cluster Analysis (CA) was used to find potential factors or sources influencing groundwater hydrochemistry.PCA is a statistical method commonly used in dealing with raw data to extract fewer variables that are more obvious and useful in explaining the main factors affecting water's hydrochemistry (Nazzal et al., 2015;Ravikumar and Somashekar, 2017).To better understand PCA results, it is preferable to use other traditional methods such as scatter plots (Karimi et al., 2019).

Cluster analysis (Ward's method) was used to demonstrate the similarity between Cluster analysis (Ward's method) was used to demonstrate the similarity between water samples and the ability to group them into convergent clusters expressing the same aquifer.This statistical technique helps in dividing samples based on the data of a number of variables into specific groups (Danielsson et al., 1999) and presenting the results in a simplified manner through the convergence of samples and groups of samples based on the similarity in the factors affecting the hydrochemistry of groundwater.
water samples and the ability to group them into convergent clusters expressing the same aquifer.This statistical technique helps in dividing samples based on the data of a number of variables into specific groups (Danielsson et al., 1999) and presenting the results in a simplified manner through the convergence of samples and groups of samples based on the similarity in the factors affecting the hydrochemistry of groundwater.


Results and Discussion


General Hydrochemical Characteristics

The coordinates

General Hydrochemical Characteristics
The coordinates, elevation, and depths of the current study wells are shown in Table 1.Table 2 presents the physical and chemical properties, as well as some statistical results, of groundwater samples collected from the wells under research.During the dry season, the concentration of dissolved solids ranged between 1593-402 mg/L with an average of 995 mg/L, while during the wet season, it ranged between 1773-309 mg/L with an average of 950 mg/L.(Table 2).It is noticed that the local variation in TDS values is high, which may be due to aquifer material variation, whereas the seasonal fluctuation was limited, which may suggest the dominance of the aquifer's rock materials over the other factors and also implies a shortage of rainfall in the region.The pH values were nearly neutral, averaging 6.9 and 7.3 during the dry and wet seasons, respectively.The order of cations in all samples during the two seasons was Ca 2+ > Mg 2+ > Na + > K + .The order of the anions in samples with low total dissolved solids (TDS<1800 (mg/L)) was as follows: HCO3 -> SO4 2− > Cl − > NO3 -> PO4 2-, while in samples with high total dissolved solids, the order was SO4 2-> HCO3 -> Cl -> NO3 -> PO4 2-.This could imply the presence of more than one aquifer in the area.

the current study wells are shown in T
ble 1.Table 2 presents the physical and chemical properties, as well as some statistical results, of groundwater samples collected from the wells under research.During the dry season, the concentration of dissolved solids ranged between 1593-402 mg/L with an average of 995 mg/L, while during the wet season, it ranged between 1773-309 mg/L with an average of 950 mg/L.(Table 2).It is noticed that the local variation in TDS values is high, which may be due to aquifer material variation, whereas the seasonal fluctuation was limited, which may suggest the dominance of the aquifer's rock materials over the other factors and also implies a shortage of rainfall in the region.The pH values were nearly neutral, averaging 6.9 and 7.3 during the dry and wet seasons, respectively.The order of cations in all samples during the two seasons was Ca 2+ > Mg 2+ > Na + > K + .The order of the anions in samples with low total dissolved solids (TDS<1800 (mg/L)) was as follows: HCO3 -> SO4 2− > Cl − > NO3 -> PO4 2-, while in samples with high total dissolved solids, the order was SO4 2-> HCO3 -> Cl -> NO3 -> PO4 2-.This could imply the presence of more than one aquifer in the area.


Hydrochemical Classification

The Piper classification, which is one of the most widely

Hydrochemical Classification
The Piper classification, which is one of the most widely used hydrochemical classifications, was used to classify the water in the research area hydrochemically.A Piper diagram is drawn using the AqQA computer program.the results of the dry season revealed that the water type in wells 1 and 15 were of the type Ca-HCO3, while well 2 was of the type Ca-Cl, and wells 4 and 5 were of the type Mg-SO4, and well 14 was of the type Mg-HCO3.The rest of the wells were of the type Ca-SO4, constituted the highest percentage, and amounted of 66.6 % (Fig. 3A).During wet season, the water type for wells 1, 14, and 15 was Ca-HCO3, the water type for well 4 was Mg-SO4, and the rest of the wells were Ca-SO 4 , which comprised the major portion of the total wells at 77.7 % (Fig. 3B).

ed hydrochemical classificati
ns, was used to classify the water in the research area hydrochemically.A Piper diagram is drawn using the AqQA computer program.the results of the dry season revealed that the water type in wells 1 and 15 were of the type Ca-HCO3, while well 2 was of the type Ca-Cl, and wells 4 and 5 were of the type Mg-SO4, and well 14 was of the type Mg-HCO3.The rest of the wells were of the type Ca-SO4, constituted the highest percentage, and amounted of 66.6 % (Fig. 3A).During wet season, the water type for wells 1, 14, and 15 was Ca-HCO3, the water type for well 4 was Mg-SO4, and the rest of the wells were Ca-SO 4 , which comprised the major portion of the total wells at 77.7 % (Fig. 3B).


Saturation Indices for Minerals

The saturation index for the most common minerals in the rese

Saturation Indices for Minerals
The saturation index for the most common minerals in the research region, including calcite, gypsum, anhydrite, and dolomites, was calculated.The saturation index of calcite ranged from unsaturated to saturated (Table 3), but it was close to the equilibrium line for all samples.Except for two samples whose saturation index was slightly above saturation, the saturation index of dolomite was under saturated.Gypsum's saturation index ranges from under saturated to equilibrium.The saturation index of halite was significantly undersaturated in all samples.It is noted that the saturation index of gypsum increases as TDS increases, suggesting that gypsum dissolution is one of the most important mechanisms causing an increase in salinity of groundwater within the study area.It is also noted that there is no clear relationship between TDS and SI for calcite, dolomite, and halite (Fig. 4).This suggests either a lack of sufficient sources of these minerals or a short period of contact between water and these components, as well as the influence of the equilibrium state and mineral saturation in reducing further dissolution of the minerals; all of which are reflected in the relationship between the saturation index and TDS.

ch region, including calcite, gy
sum, anhydrite, and dolomites, was calculated.The saturation index of calcite ranged from unsaturated to saturated (Table 3), but it was close to the equilibrium line for all samples.Except for two samples whose saturation index was slightly above saturation, the saturation index of dolomite was under saturated.Gypsum's saturation index ranges from under saturated to equilibrium.The saturation index of halite was significantly undersaturated in all samples.It is noted that the saturation index of gypsum increases as TDS increases, suggesting that gypsum dissolution is one of the most important mechanisms causing an increase in salinity of groundwater within the study area.It is also noted that there is no clear relationship between TDS and SI for calcite, dolomite, and halite (Fig. 4).This suggests either a lack of sufficient sources of these minerals or a short period of contact between water and these components, as well as the influence of the equilibrium state and mineral saturation in reducing further dissolution of the minerals; all of which are reflected in the relationship between the saturation index and TDS.


Ion Exchange

To better understand the interaction between water and rocks, Schoeller  4).As all of th

Ion Exchange
To better understand the interaction between water and rocks, Schoeller  4).As all of the results were positive and there was no negative value, this implies that sodium and potassium ions in the water exchange with calcium and magnesium ions in rocks and sediments.As a result, direct ion exchange is one of the geochemical processes influencing groundwater hydrochemistry in the studied area.

results were
ositive and there was no negative value, this implies that sodium and potassium ions in the water exchange with calcium and magnesium ions in rocks and sediments.As a result, direct ion exchange is one of the geochemical processes influencing groundwater hydrochemistry in the studied area.


Factors Controlling Major Elements Chemistry

The chemistry of groundwater varies widely from place to place, and this variation is caused by a variety of reasons and factors, which can be summarized as natural factors and other anthropogenic factors.Natural factors have a bigger impa

Factors Controlling Major Elements Chemistry
The chemistry of groundwater varies widely from place to place, and this variation is caused by a variety of reasons and factors, which can be summarized as natural factors and other anthropogenic factors.Natural factors have a bigger impact on water's hydrochemistry than anthropogenic factors, which have a limited and secondary effect (Abdalla and Al-Abri, 2014;Dhannoun andMahmood, 2014, 2019;Subba Rao et al., 2020)

on water's hydrochemistry than anthropogenic factors, which have a limited and secondary
effect (Abdalla and Al-Abri, 2014;Dhannoun andMahmood, 2014, 2019;Subba Rao et al., 2020)


Gibbs Diagram

Two main types of natural factors can be identified, namely factors related to the geology of the aquifer, and factors related to the climate of the area.In fact, we cannot isolate the influence of one factor from

Gibbs Diagram
Two main types of natural factors can be identified, namely factors related to the geology of the aquifer, and factors related to the climate of the area.In fact, we cannot isolate the influence of one factor from the other, since factors related to the geology of the region share with those related to the climate of the region in influencing the hydrochemistry of the groundwater.However, it is possible to show the influence of which of these two factors is dominant on the hydrochemistry of groundwater.A Gibbs diagram is commonly used to highlight which natural factors control water's hydrochemistry (Gibbs, 1970).The Gibbs diagram results for the current study's samples revealed that the groundwater in the study area during the dry and wet seasons falls within the field of rock/soil-water interaction control.The majority of the samples are closer to the field of evaporation than to the field of precipitation control (Fig. 5), indicating a lack of rainfall and an increase in evaporation processes within the study area.

he other, since factors related to the geolog
of the region share with those related to the climate of the region in influencing the hydrochemistry of the groundwater.However, it is possible to show the influence of which of these two factors is dominant on the hydrochemistry of groundwater.A Gibbs diagram is commonly used to highlight which natural factors control water's hydrochemistry (Gibbs, 1970).The Gibbs diagram results for the current study's samples revea

d that the gro
ndwater in the study area during the dry and wet seasons falls within the field of rock/soil-water interaction control.The majority of the samples are closer to the field of evaporation than to the field of precipitation control (Fig. 5), indicating a lack of rainfall and an increase in evaporation processes within the study area.


Weathering process

After it was revealed that rocks are the dominant factor influencing the groundwater hydrochemistry in the study area, the following question arises: What are the compositions of these rocks and minerals influencing the chemical elements in the groundwater under study, and is it possible to know these components simply by the water content of major ions?Answering this question is based on the fact that the mineral components of rocks consist of certain proportions of chemical elements, and that the weathering process of these minerals will eventually release proportionate amounts of chemical elements into the water.Accordingly, certain correlations and the proportion of certai

Weathering process
After it was revealed that rocks are the dominant factor influencing the groundwater hydrochemistry in the study area, the following question arises: What are the compositions of these rocks and minerals influencing the chemical elements in the groundwater under study, and is it possible to know these components simply by the water content of major ions?Answering this question is based on the fact that the mineral components of rocks consist of certain proportions of chemical elements, and that the weathering process of these minerals will eventually release proportionate amounts of chemical elements into the water.Accordingly, certain correlations and the proportion of certain chemical ions in water can be used to infer the types of rock components that dominate groundwater hydrochemistry (Davraz and Batur, 2021;X. Li et al., 2018;Liang et al., 2018).Nonetheless, many processes are engaged in the evolution of groundwater hydrochemistry, and much work is expected to explain the groundwater system's ionic properties.

chemical ions in wa
er can be used to infer the types of rock components that dominate groundwater hydrochemistry (Davraz and Batur, 2021;X. Li et al., 2018;Liang et al., 2018).Nonetheless, many processes are engaged in the evolution of groundwater hydrochemistry, and much work is expected to explain the groundwater system's ionic properties.

In general, the ratios of different chemical variables can be used to understand groundwater chemistry evolution (Li et al., 2015).Certain correlations and the ratios of some key ions in water were employed in this study to shed light on the potential weathering processes that control groundwater chemistry.Calcium is the predominant cation in the groundwater of the current study, and if the rocks are sedimentary rocks, as in the study area, this mostly suggests the weathering of carbonate rocks (limestone and dolomite) and/ Or evaporites (gypsum and anhydrite).This is also enhanced by the relationship between (Ca 2+ +Mg 2+ ) and (HCO3 -+SO4 2-) (Fig. 4A), where the majority of the samples are scatter In general, the ratios of different chemical variables can be used to understand groundwater chemistry evolution (Li et al., 2015).Certain correlations and the ratios of some key ions in water were employed in this study to shed light on the potential weathering processes that control groundwater chemistry.Calcium is the predominant cation in the groundwater of the current study, and if the rocks are sedimentary rocks, as in the study area, this mostly suggests the weathering of carbonate rocks (limestone and dolomite) and/ Or evaporites (gypsum and anhydrite).This is also enhanced by the relationship between (Ca 2+ +Mg 2+ ) and (HCO3 -+SO4 2-) (Fig. 4A), where the majority of the samples are scattered along the 1:1 line, indicating weathering of carbonate and gypsum rocks (Zhang et al., 2020).The strong direct relationship between (Ca 2+ ) and (SO4 2-) (Fig. 6B) suggests that gypsum mineral dissolution is the dominant process on the Ca 2+ and SO4 2-ion content of groundwater, which are the predominant cation and anion, respectively.This suggests that the process of gypsum mineral dissolution (CaSO4.2H2O) is the one that has the most influence on the chemistry of groundwater in the region.This is completely consistent with the geology of the region, where the Fatha Formation, which includes gypsum rocks exposed in large parts of the research area, is the dominant formation.The deviation of some samples from the 1:1 line in Fig. (6 (B)) may be attributed to the presence of other minerals: When the samples are above the 1:1 line, it could be due to the participation of dolomite (CaMg (CO3)2) and calcite (CaCO3) in the supply of calcium ions.When samples fall below the 1:1 line, it could be due to the presence of salts such as magnesium sulfate in the sulfate ion supply.Furthermore, this could be due to calcite deposition, especially since the majority of the samples with higher SO4 2- concentrations compared to Ca 2+ are from the winter season, when the saturation index of calcite is relatively higher.This is in addition to the potential effect of the ion exchange process on the concentration of calcium ions (Zhang et al., 2020).The moderate direct proportional relationship between (Mg 2+ ) and (HCO3 -) ions indicates the involvement of carbonate minerals represented by dolomite and calcite, of which there are layers of limited thickness within the Fatha formation, as sources of calcium, magnesium, and bicarbonate ions in the groundwater of the study area.The study samples (Fig. 6(C)) are located above the 2:1 line, which represents the ratio of magnesium and bicarbonate ions resulting from the weathering of dolomite mineral (Walraevens et al., 2018;Zhang et al., 2020).It is possible that this is due to the dedolomitization process, as the dissolution of anhydrite and gypsum raises Ca concentrations, causing the common ion effect to force calcite precipitation and decrease pH and HCO3.As a result, removing the carbonate ion promotes dolomite dissolution and increases Mg concentration (Karimi et al., 2017).Furthermore, the ion exchange process may contribute to an increase in the content of the magnesium ion versus the bicarbonate ion, according to the following equation: d along the 1:1 line, indicating weathering of carbonate and gypsum rocks (Zhang et al., 2020).The strong direct relationship between (Ca 2+ ) and (SO4 2-) (Fig. 6B) suggests that gypsum mineral dissolution is the dominant process on the Ca 2+ and SO4 2-ion content of groundwater, which are the predominant cation and anion, respectively.This suggests that the process of gypsum mineral dissolution (CaSO4.2H2O) is the one that has the most influence on the chemistry of groundwater in the region.This is completely consistent with the geology of the region, where the Fatha Formation, which includes gypsum rocks exposed in large parts of the research area, is the dominant formation.The deviation of some samples from the 1:1 line in Fig. (6 (B)) may be attributed to the presence of other minerals: When the samples are above the 1:1 line, it could be due to the participation of dolomite (CaMg (CO3)2) and calcite (CaCO3) in the supply of calcium ions.When samples fall below the 1:1 line, it could be due to the presence of salts such as magnesium sulfate in the sulfate ion supply.Furthermore, this could be due to calcite deposition, especially since the majority of the samples with higher SO4 2- concentrations compared to Ca 2+ are from the winter season, when the saturation index of calcite is relatively higher.This is in addition to the potential effect of the ion exchange process on the concentration of calcium ions (Zhang et al., 2020).The moderate direct proportional relationship between (Mg 2+ ) and (HCO3 -) ions indicates the involvement of carbonate minerals represented by dolomite and calcite, of which there are layers of limited thickness within the Fatha formation, as sources of calcium, magnesium, and bicarbonate ions in the groundwater of the study area.The study samples (Fig. 6(C)) are located above the 2:1 line, which represents the ratio of magnesium and bicarbonate ions resulting from the weathering of dolomite mineral (Walraevens et al., 2018;Zhang et al., 2020).It is possible that this is due to the dedolomitization process, as the dissolution of anhydrite and gypsum raises Ca concentrations, causing the common ion effect to force calcite precipitation and decrease pH and HCO3.As a result, removing the carbonate ion promotes dolomite dissolution and increases Mg concentration (Karimi et al., 2017).Furthermore, the ion exchange process may contribute to an increase in the content of the magnesium ion versus the bicarbonate ion, according to the following equation:
2Na + +MgX2=Mg 2+ +2NaX
The bilateral relationship between the sodium and chloride ions (Fig. 6(D)) suggests the possibility of Halite mineral (NaCl) participation as a source of these two ions, as it is noted that there is a direct relationship between the two ions, and it is likely that it is a result of Halite dissolution.Thus, the concentration of the two ions increases directly with the increase in Halite dissolution.Halite may be formed as a result of water evaporation processes in the upper layers of the soil, and it may also be present in limited quantities within the evaporite deposits of Fatha formation.Defining the mineral halite as the only source of sodium and chloride ions in water should result in a 1:1 ratio of the two i The bilateral relationship between the sodium and chloride ions (Fig. 6(D)) suggests the possibility of Halite mineral (NaCl) participation as a source of these two ions, as it is noted that there is a direct relationship between the two ions, and it is likely that it is a result of Halite dissolution.Thus, the concentration of the two ions increases directly with the increase in Halite dissolution.Halite may be formed as a result of water evaporation processes in the upper layers of the soil, and it may also be present in limited quantities within the evaporite deposits of Fatha formation.Defining the mineral halite as the only source of sodium and chloride ions in water should result in a 1:1 ratio of the two ions.The current study's samples, however, fall below the 1:1 line (Fig. 6D), indicating an increase in chloride ions relative to sodium ions.Increasing chlorine ion concentration may indicate groundwater contamination due to the infiltration of domestic sewage or livestock water into the groundwater (Li et al., 2015).Furthermore, this could be attributable to chloride's high ability to move through the soil, while cation exchange could remove the dissolved sodium.The positive CAI-I and CAI-II indices in Table 3 support the occurrence of direct ion exchange processes (Barkat et al., 2021), which is consistent with an increase in magnesium ions and a decrease in sodium ions.This process can cause the ionic ratios of the research samples to rise to the top of the 1:2 line, and down the 1:1 line in Figures (6 (C) and (D)).
ns.The current study's samples, however, fall below the 1:1 line (Fig. 6D), indicating an increase in chloride ions relative to sodium ions.Increasing chlorine ion concentration may indicate groundwater contamination due to the infiltration of domestic sewage or livestock water into the groundwater (Li et al., 2015).Furthermore, this could be attributable to chloride's high ability to move through the soil, while cation exchange could remove the dissolved sodium.The positive CAI-I and CAI-II indices in Table 3 support the occurrence of direct ion exchange processes (Barkat et al., 2021), which is consistent with an increase in magnesium ions and a decrease in sodium ions.This process can cause the ionic ratios of the research samples to rise to the top of the 1:2 line, and down the 1:1 line in Figures (6 (C) and (D)).


Statistical Analysis


Principal Component Analysis (PCA)

SPSS version 20 was used for PCA, and components with eigenvalues greater than one were considered (Fig. 7(a)).The PCA results revealed the presence of three principal components that influence the concentrations of the major ions.Together, these principal components account for more than 73% of the variance (Table 5).

PC1 constitutes 43.853% of the variance, and it is the dominant component and is represented by the positive loading of the variables TDS, Ca 2+ , Mg 2+ , SO4 2-, Cl -, Na + , K + , and HCO3 -(Table 5).Observing the variables loaded on PC1, it is obvious that this PC represents the weathering of gypsum and carbonate minerals, as well as the possib

Principal Component Analysis (PCA)
SPSS version 20 was used for PCA, and components with eigenvalues greater than one were considered (Fig. 7(a)).The PCA results revealed the presence of three principal components that influence the concentrations of the major ions.Together, these principal components account for more than 73% of the variance (Table 5).
PC1 constitutes 43.853% of the variance, and it is the dominant component and is represented by the positive loading of the variables TDS, Ca 2+ , Mg 2+ , SO4 2-, Cl -, Na + , K + , and HCO3 -(Table 5).Observing the variables loaded on PC1, it is obvious that this PC represents the weathering of gypsum and carbonate minerals, as well as the possibility of secondary participation of halite and Sylvite minerals.This is consistent with what was reached in the discussion of the graphic representation of chemical ions (Fig. 6).It is also noted that the pH has a moderate negative loading on the PC1, indicating that the pH has an opposite effect on carbonate weathering (Qian et al., 2016).PC2 constitutes 16.717% of the variance and is represented by the positive loading of the nitrate and phosphate ions and the negative loading of the pH (Fig. 7(b)).Since this PC has no effect on the major ions except nitrate and phosphate, it is likely that this PC is an anthropogenic factor caused by agricultural activities, especially since nitrate and phosphate are basic components of some agricultural fertilizers and are also major components of animal waste (Esmael and Seeyan, 2023).The negative loading of the pH on this PC may refer to surface water, which is likely to have a pH value that is lower than groundwater due to its contact with the CO2-containing atmosphere as well as the presence of organic materials in the surface layers of the soil.This reinforces the hypothesis that this factor is the result of human activities.As for PC3, it is a secondary one in effect, as it constitutes only 12.625% of the variance.

ipation of halite and Sylvite miner
ls.This is consistent with what was reached in the discussion of the graphic representation of chemical ions (Fig. 6).It is also noted that the pH has a moderate negative loading on the PC1, indicating that the pH has an opposite effect on carbonate weathering (Qian et al., 2016).PC2 constitutes 16.717% of the variance and is represented by the positive loading of the nitrate and phosphate ions and the negative loading of the pH (Fig. 7(b)).Since this PC has no effect on the major ions except nitrate and phosphate, it is li ely that this PC is an anthropogenic factor caused by agricultural activities, especially since nitrate and phosphate are basic components of some agricultural fertilizers and are also major components of animal waste (Esmael and Seeyan, 2023).The negative loading of the pH on this PC may refer to surface water, which is likely to have a pH value that is lower than groundwater due to its contact with the CO2-containing atmosphere as well as the presence of organic materials in the surface layers of the soil.This reinforces the hypothesis that this factor is the result of human activities.As for PC3, it is a secondary one in effect, as it constitutes only 12.625% of the variance.

It is noted that PC3 is not unique in influencing any of the variables in this analysis, but it is somewhat involved with PC1 in influencing the ions Na + , K + , and HCO3 -.This factor may indicate the weathering of feldspar minerals, including K-feldspar and Albite, which are present within the sediments of the Tigris River (Mahmood, 2021).According to the following mineral weathering and ion release equations:


Cluster Analysis

Hierarchical Cluster Analysis is a statistical technique for categorizing data for a variety of variables.It aids in the organization of data into groups and simplifies the presentation of results based on sample convergence (Chen et al., 2007;Danielsson et al., 1999).SPSS version 20 was used for the hiera It is noted that PC3 is not unique in influencing any of the variables in this analysis, but it is somewhat involved with PC1 in influencing the ions Na + , K + , and HCO3 -.This factor may indicate the weathering of feldspar minerals, including K-feldspar and Albite, which are present within the sediments of the Tigris River (Mahmood, 2021).According to the following mineral weathering and ion release equations:

Cluster Analysis
Hierarchical Cluster Analysis is a statistical technique for categorizing data for a variety of variables.It aids in the organization of data into groups and simplifies the presentation of results based on sample convergence (Chen et al., 2007;Danielsson et al., 1999).SPSS version 20 was used for the hierarchical cluster analysis.In this analysis, the chemical element data (Ca 2+ , Mg 2+ , K + , Na + , SO4 2-, HCO3 -, Cl -, NO3 -, PO4 3-, TDS) for the dry and wet seasons were entered.
chical cluster analysis.In this analysis, the chemical element data (Ca 2+ , Mg 2+ , K + , Na + , SO4 2-, HCO3 -, Cl -, NO3 -, PO4 3-, TDS) for the dry and wet seasons were entered.

The analysis results indicated that the wells in the current study area could be categorized into three groups based on the hydrochemical properties of their water.Each of the three groups contains a number of wells with similar hydroch The analysis results indicated that the wells in the current study area could be categorized into three groups based on the hydrochemical properties of their water.Each of the three groups contains a number of wells with similar hydrochemical properties.Returning to the geology of the region, the wells in the region fall within two main types of rock components.The first type is represented by Quaternary deposits, which are mainly river terrace sediments and consist of gravel, sand, silt, and clay, with the sandy gravel layer often containing water (Al-Nuaimy, 2010).Under these deposits is another type of sediment, the Fatha formation, which is commonly exposed in the areas surrounding the river sediments and represents the other type of rock components carrying water in the region.After identifying the rock components of the region's water reservoirs, it is clear that the wells in the first cluster (Fig. 8) belong to the aquifer of Quaternary deposits, which is characterized by relatively low concentrations of the main ions, and this is because the water reservoir is composed mainly of sand and gravel.The third cluster represents water within the Fatha formation, which is characterized by high concentrations of most of the major ions, particularly the sulfate ion, due to the impact of gypsum rocks, which is one of the main causes for the increase of the sulfate ion in groundwater in this region.Concerning the second group of wells, in which the main ion concentrations were intermediate between the first and third groups.It appears that the waters of these wells represent a transitional area between the two reservoirs or because of the wells in this cluster penetrating both of the aforementioned aquifers, resulting in the mixing of the waters of the two reservoirs in these wells.Especially since the process of drilling wells is done at random, and the depth of drilling is not subject to any criterion other than water quantity, regardless of the quality of the water.
mical properties.Returning to the geology of the region, the wells in the region fall within two main types of rock components.The first type is represented by Quaternary deposits, which are ma nly river terrace sediments and consist o

gravel, sand, sil
, and clay, with the sandy gravel layer often containing water (Al-Nuaimy, 2010).Under these deposits is another type of sediment, the Fatha formation, which is commonly exposed in the areas surrounding the river sediments and represents the other type of rock components carrying water in the region.After identifying the rock components of the region's water reservoirs, it is clear that the wells in the first cluster (Fig. 8) belong to the aquifer of Quaternary deposits, which is characte ized by relatively low concentrations of the main ions, and this is because the water reservoir is composed mainly of sand and gravel.The third cluster represents water within the Fatha formation, which is characterized by high concentrations of most of the major ions, particularly the sulfate ion, due to the impact of gypsum rocks, which is one of the main causes for the increase of the sulfate ion in groundwater in this region.Concerning the second group of wells, in which the main ion concentrations were intermediate between the first and third groups.It appears that the waters of these wells represent a transitional area between the two reservoirs or because of the wells in this cluster penetrating both of the aforementioned aquifers, resulting in the mixing of the waters of the two reservoirs in these wells.Especially since the process of drilling wells is done at random, and the depth of drilling is not subject to any criterion other than water quantity, regardless of the quality of the water.


Conclusions

The rock components represented by gypsum rocks primarily and carbonate rocks secondarily control groundwater hydrochemistry in the study area, with the presence of a secondary effect of direct ion exchange processes on calcium, magnesium, and sodium concentrations.This is in addition to the limited impact of anthropogenic factors represented by agricultural activities, which is manifested in the effect on the nitrate content.In general, the region has two aquifers: the first is represented by Quaternary deposits and consists mainly of river sediments, and its water content of major ions is lower than that of the second aquifer, which is represented by the Fatha Formation and has relatively high concentrations of major ions, particularly the sulfate ion.Aside from the two types mentioned above, some wells pump mixed water from the two aquifers as a result of drilling operations that reached both aquifers.

Based on the foregoing, it is highly recommended to limit th

Conclusions
The rock components represented by gypsum rocks primarily and carbonate rocks secondarily control groundwater hydrochemistry in the study area, with the presence of a secondary effect of direct ion exchange processes on calcium, magnesium, and sodium concentrations.This is in addition to the limited impact of anthropogenic factors represented by agricultural activities, which is manifested in the effect on the nitrate content.In general, the region has two aquifers: the first is represented by Quaternary deposits and consists mainly of river sediments, and its water content of major ions is lower than that of the second aquifer, which is represented by the Fatha Formation and has relatively high concentrations of major ions, particularly the sulfate ion.Aside from the two types mentioned above, some wells pump mixed water from the two aquifers as a result of drilling operations that reached both aquifers.
Based on the foregoing, it is highly recommended to limit the random drilling of wells to maintain groundwater quality.The drilling must be in accordance with controls and conditions set by the competent authorities so that the depth of drilling is determined according to the available water reservoirs to prevent the mixing of good quality water (the Quaternary aquifer) with Poor quality water (the Fatha aquifer).In order to prevent water from the Quaternary aquifer and the Fatha aquifer from mixing, it is also advised to conduct a geophysical survey to identify the depths of the aquifers in the area before drilling more wells.Farmers must be instructed to use fertilizers in a scientific manner and according to the needs of plants, especially in light of the presence of evidence of groundwater pollution through the excessive use of fertilizers, which may reach the groundwater.

random drill
ng of wells to maintain groundwater quality.The drilling must be in accordance with controls and conditions set by the competent authorities so that the depth of drilling is determined according to the available water reservoirs to prevent the mixing of good quality water (the Quaternary aquifer) with Poor quality water (the Fatha aquifer).In order to prevent water from the Quaternary aquifer and the Fatha aquifer from mixing, it is also advised to conduct a geophysical survey to identify the depths of the aquifers in the area before drilling more wells.Farmers must be instructed to use fertilizers in a scientific manner and according to the needs of plants, especially in light of the presence of evidence of groundwater pollution through the excessive use of fertilizers, which may reach the groundwater.

Fig. 2 .
2
Fig. 2. (A).Geological map of the research area.(B): Lithologic sections of the Fatha Formation

Fig. 2 .
Fig. 2. (A).Geological map of the research area.(B): Lithologic sections of the Fatha Formation from Butma West, located on the current study area's northwestern border(Al-Juboury and McCann, 2008).
from Butma West, located on the current study area's northwestern border(Al-Juboury and McCann, 2008).




(1965) proposed equations for calculating chloro-alkaline indices (CAI).Negative CAI values indicate reverse ion exchange, whereas positive CAI values indicate direct ion exchange.The chloro-alkaline indices were computed for the well-water samples under consideration.During the dry season, CAI-I values ranged from 0.088 to 0.703, whereas CAI-II values ranged from 0.019 to 0.326.In the wet season, CAI-I levels ranged from 0.046 to 0.798, whereas CAI-II values ranged from 0.009 to 0.389 (Table


Fig. 4 .
4
Fig. 4. The relationship between TDS and the SI for Dolomite, Calcite, Gypsum and Halite


Fig. 5 .
5
Fig. 5. Gibbs plots displaying the mechanisms governing groundwater chemistry in current samples.




2KAlSi3O8 + 9H2O + 2H2CO3 = Al2Si2O5(OH)4 + 2K + + 2HCO3 − + 4H4SiO4 [K (1965) proposed equations for calculating chloro-alkaline indices (CAI).Negative CAI values indicate reverse ion exchange, whereas positive CAI values indicate direct ion exchange.The chloro-alkaline indices were computed for the well-water samples under consideration.During the dry season, CAI-I values ranged from 0.088 to 0.703, whereas CAI-II values ranged from 0.019 to 0.326.In the wet season, CAI-I levels ranged from 0.046 to 0.798, whereas CAI-II values ranged from 0.009 to 0.389 (Table

Fig. 4 .
Fig. 4. The relationship between TDS and the SI for Dolomite, Calcite, Gypsum and Halite

Fig. 5 .
Fig. 5. Gibbs plots displaying the mechanisms governing groundwater chemistry in current samples.

Fig. 7 .
Fig. 7. (a) Scree plot of the singular values; (b) Graphical representation of the variables loaded on the three principal components

Fig. 8 .
Fig. 8. Dendrogram of the hierarchical cluster analysis using the Ward method

Table 1 .
Coordinates, Elevation and depths of the current study wells

Table 2 .
The physicochemical data of the study samples

0.12754.83
Fig. 3. Piper diagram presenting the chemical composition of groundwater samples in the studied area.

Table 3 .
Mineral saturation index (gypsum, calcite, dolomite, and halite) in the groundwater of the current study wells during the dry and wet seasons

Table 4 .
Chloro-alkaline indices (CAI-I and CAI-II) for the current study wells in both dry and wet seasons.

Table 5 .
Variables loading on the components, eigenvalues, and variances for the current study data