Assessment of groundwater hydrogeological processes, isotopic composition, and associated health risks of the Banaz (Usak) Basin, Turkey

To this day, groundwater is used for development and domestic consumption around the world (Tolera et al. 2020). The geochemical evolution of groundwater in the hydrogeological system and water quality comes to the fore with the increase in the demand for groundwater in rural regions. Conducting water quality studies in a basin is important for the development and effective management of groundwater. The hydrogeochemical processes can be influenced by changing climatic conditions, anthropogenic activities and rock-water interactions such as growing population, industrialization, and intensive agricultural, and urbanization activities. Additionally, in rural regions with uncontrolled use of water sources, the groundwater system must be controlled regularly. Determining the hydrogeochemistry of an aquifer and groundwater quality is crucial to ensure cleaner and safer water for human consumption (Singh et al. 2023). Hydrogeochemistry of an area helps in understanding the geological processes which control the chemistry of water and plays an important role in determining the suitability of groundwater for various purposes (Singh et al. 2015). Determining the quality of water for drinking, industrial and agricultural purposes is achieved with the help of hydrogeochemical processes. This situation also helps to determine the changes in water quality that occur as a result of water–rock interaction (Kumar et al. 2006).

A lot of studies have investigated the-groundwater origins using stable isotopes (δ²H and δ¹⁸O) and radioactive isotopes (³H) (Hitchon & Friedman 1969; Siegenthaler 1979; Abdelkarim et al. 2023; Qu et al. 2023). As stable tracers, δ¹⁸O and δ²H have been used to conceptualize groundwater recharge models and investigate hydrological processes (Gat 1996; Clark & Fritz 1999). Comparing the isotopic composition obtained from groundwater and evaluating the recharge mechanism is done by comparing the isotopic composition of stable isotopes of water obtained from groundwater and precipitation (Blasch & Bryson 2007; Heilweil et al. 2009). The spatial and temporal isotope variability in rainfall is influenced by the stable isotope effects, which are a function of the climate (temperature, humidity, and amount of rainfall) and physical characteristics (elevation, distance from ocean, rainfall moisture sources, and temperature) (Clark & Fritz 1999). This affects the stable isotope composition of rainfall that eventually recharges the aquifers (Abiye 2023). Changes in the isotopic composition of water within the water cycle provide a recognizable signature, relating such water to the different phases of the cycle (Gat 1996).

This study aims to identify hydrochemical processes, isotopic characterization, recharge sources and zones of the groundwater for the Banaz (Usak) basin. Determining and interpreting the isotopic composition and hydrogeochemical data will help us understand the geochemical processes of groundwaters in the Banaz (Usak) basin. Also, the study area is a region geologically dominated by Neogene rocks and where agricultural activities are carried out excessively. For this reason, geogenic and anthropogenic factors that affect the quality of groundwater in the basin come to the fore. The subject of this study is to determine the pollution that may arise especially due to water–rock interaction and agricultural activities and to discuss the effects of existing pollution on human health.

In the study area, drinking water is generally taken from spring water and wells. For this reason, only natural spring waters and wells were preferred when sampling. A field study was carried out in the Banaz (Usak) area during May 2022 for data collection and observation. Samples were collected from 10 sampling locations, springs and wells. 60% of the samples taken are springs and 40% are wells. While taking samples from springs, care was taken to ensure that the spring was the exit point. The altitudes of the sampled springs vary between 902 and 1,164 m. The sampled wells are generally surrounded by agricultural lands. Samples were collected in cleaned polythene plastic bottles (100-ml capacity for trace elements, 500-ml capacity for major elements and 1,000-ml capacity for isotope characteristics) and were properly labelled, collection date, time and name of samples. Nitric acid (HNO₃) was added to samples for cation analysis. The locations of the water samples taken were determined using the Magellan Explorist 710 handheld Global Positioning System (GPS) and processes on the geological map of the study area.

Sampling and analysis were carried out using standard analytical methodology. The physico-chemical parameters (T, EC, pH, TDS, salinity and total hardness) were measured on-site with a HACH HQ40D brand measuring device. The samples were acidified with HNO₃ for cation analysis. Major ions like bicarbonate, sulphate, chloride, magnesium, potassium, calcium, sodium, and nitrite, nitrate, ammonium ions were carried out at the Süleyman Demirel University Faculty of Engineering Department of Geological Engineering Groundwater, Rock and Mineral Analysis Laboratory. Inductively coupled plasma-optic emission spectrometry (ICP-OES Perkin Elmer 2100 DV) was used to analyze the cations (Ca²⁺, Mg²⁺, Na⁺, and K⁺). The control of the chemical analyses is carefully inspected by ion balances. The ion balance, which is the per cent difference between cations and anions, for the analyses is generally within ±5%. Ammonium (⁠⁠) was analyzed using a spectrophotometer device (Spectroquant ^® Merck Nova 60). IC-Dionex ICS 3000 (Ion chromatography) was used to analyze anions chlorine (Cl⁻), sulfate (⁠⁠), nitrite (⁠⁠), and nitrate (⁠⁠). Bicarbonate (⁠⁠) and carbonate (⁠⁠) were analyzed using Merck-Aquamerck test kits with the titrimetric method.

Trace elements were analyzed in the Acme Analytical Laboratories-Canada Bureau Veritas Mineral Laboratories. The elements (Zn, B, U, Se, Sb, Al, Pb, As, Cu, Cd, Cr, Fe, Ba, Mn, Br, Ni, and Hg) were determined using the ICP-MS (inductively coupled plasma-mass spectroscopy). The SO200 method was used in the ICP-MS analysis. Method SO200 (analysis by ICP-MS) provides the low detection limits needed to define background and anomalous levels of cations in natural water. For this analysis, all water samples must have less than 0.1% total dissolved solids (TDS).

Results of all chemical analyses were plotted with AquChem software (Version 3.7) (Calmbach 1999). Results of hydrochemical analyses were classified and interpreted by Piper (1944, 1953), Durov (1948), Chadha (1999), Gibbs (1970) and scatter diagrams. Also, to determine the ion exchange, chloroalkaline indices (CAI I and CAI II) were calculated. Results of all chemical analyses were plotted with AquChem software (Version 3.7) (Calmbach 1999). In addition, using the chemical analysis results of groundwater in the study area, saturation index values (SI_Anhydrite, SI_Aragonite, SI_Barite, SI_Calcite, SI_Dolomite, SI_Gypsum, and SI_Magnesite) were calculated with the help of the computer program Solmineq 88 (Kharaka 1988). The suitability of the groundwaters for drinking was evaluated by the World Health Organization (WHO 2011), the United States Environmental Protection Agency (US EPA 1986, 1989, 2001, 2004, 2013, 2018, 2020) and the Turkish Standard Institution (TSI 266 2005) guideline values for drinking water.

Isotope analyses were performed at the Ankara Technical Research and Quality Control Department of Isotope Laboratory and Director in the SHW (State Hydraulic Work). IAEA (International Atomic Energy Agency)-Equilibration method was used to determine stable isotopes (oxygen 18 (δ¹⁸O) and deuterium (δ²H)). Tritium (δ³H) was determined by the IAEA-LSC (Liquid Siltation Counting) Technique. The results of stable isotopes were evaluated according to the GMWL (Global Meteoric Water Line). The analytical error was accepted as ±0.1 and ±1%, respectively. A tritium unit (TU) was used for tritium concentration. The tritium unit is 1 TU = 0.1183 Bq/L. Measurement uncertainty in experimental results is calculated at %95 (confidence interval; K = 2). The precision of measurements is ±1 TU. The GMWL (Global Meteoric Water Line) (Craig 1961), the EMMWL (East Mediterranean Meteoric Water Line) (Gat & Carmi, 1970) and the AMWL (Usak Meteoric Water Line) (Gokgoz et al. 2011) were used to compare the isotopic composition of waters.

The parameters used in the equations are shown in Table 1.

The HQ for children and adults during a lifetime can be calculated by dividing the ADD from each exposure route by a specific reference dose (RfD) (Equation (3)). Here, RfD is the reference dose (mg kg⁻¹ d⁻¹).

In an area where the assumed geological character has not changed, health problems that may arise due to the water consumed by people must also be taken into account. For this reason, it is important to know the geological, hydrogeological and hydrogeochemical elements of the region and to examine the problems that may arise depending on these elements. In this context, the geology, hydrogeology and hydrogeochemistry of the study area were examined in detail and the potential exposure to water pollution detected in the region was determined.

Metamorphic, sedimentary, ultramafic and volcanic rocks formed in the Paleozoic-Quaternary period are widely exposed in the study area which comprises Banaz (Usak) province. In the study area, Anamas-Akseki autochthonous is represented by the Akdag group and Homa-Akdag unit. The Akdag group is made up of Precambrian-aged Kestel formation metasedimentary and metavolcanic rocks. The Homa-Akdag unit is made up of the Late Triassic-Liassic Ilyasli formation consisting of conglomerate and siltstone–sandstone alternation. Paleozoic-aged Afyon metamorphics comprise metamorphic schist and marbles. The Ortadag formation comprises crystallized limestones deposited, dolomitic limestone and dolomite during the Middle Triassic-Jurassic and the formation is represented by the Ortadag Unit. In addition, Mesozoic marbles are distributed in the southeast and northwest of the study area and the marbles are aged Jurassic-Cretaceous. The Lycian nappes are represented by Marmaris ophiolitic nappe. Kizilcadag melange and olistostrome of Late Senonian which belongs to Marmaris Ophiolite Nappe comprises serpentinized harzburgite, dunite, diabase, basic volcanic rocks, neritic and pelagic limestones, clastic sediments, radiolarite-chert, and dolomite. A meta ophiolite complex consisting of meta gabbro, meta diorite, meta basalt, epidote-actinolite schist, chlorite-epidote schist, and chlorite schist covers the northern part of the study area.

The Neogene sedimentation is represented by terrestrial sedimentation, fluvial, alluvial and lacustrine deposition in the study area. The terrestrial sedimentation is represented by the Hacibekir group, Gebeciler, Erdemir, Ulubey formations and Cameli formation limestone members. The depositional process began with fluvial deposition dominating the Late Miocene lasted by lower alluvial and upper lacustrine deposits constituting Middle Miocene succession, and continues by reflecting the alluvial deposition during Late Miocene. Also, including alkaline potassic products of Afyon volcanism, Neogene volcanics, laterally pass to Neogene depositions which are represented by Adatepe andesite and Banaz volcanics. Quaternary-aged terrestrial deposits (alluvium, alluvial fan and slope debris) were located over all the units (Ocal et al. 2011; Ocal & Goktas 2011; Balci 2011a, 2001b; Figure 1; Table 2).

The lithological units were evaluated according to their hydrogeological characteristics. There are two important lithological units: the porous aquifer and the karstic aquifer. Loose sand, gravel, and clay consisting units form the porous aquifer, the main groundwater reservoir in the study area. The porous aquifer is the most significant and reliable regional groundwater system in the Banaz (Usak) basin. Porous aquifers are known to be the best in groundwater productivity because of their high permeability. In addition, according to the drilled wells, the thickness of the porous aquifer is 10–30 m in the valley beds with high elevations, while it reaches about 100 m in the plain. In the study area, porous aquifers are present in alluvial plain areas, while karstic aquifers are present in the high areas. Units consisting of limestone, travertine, dolomite, dolomitic limestone, micritic limestone and marble are defined as karstic aquifers. Hydrogeologically, the aquitard mediums have been considered low-permeability rocks. Marl, mudstone, claystone and siltstone levels of the rocks are impermeable, however, conglomerate and sandstone levels allow groundwater accumulation and movement. In the study area, unit aquitard medium I, consisting of alluvial fan deposits and volcano-sedimentary lacustrine deposits, unit aquitard medium II consisting of sandstone, conglomerate, claystone, mudstone, and marl, and unit consisting of siltstone, conglomerate, sandstone, claystone, limestone and lignite were distinguished as aquitard medium III. The unit consisting of andesite represents aquitard medium IV and the unit consisting of tuff, rhyolite, dacite and andesite represents aquitard medium V. The aquitard mediums are semi-permeable units. The aquifuge system regionally consisting of the impermeable units is distinguished as aquifuge medium I and II. The unit composed of carbonate, diabase, gabbro, radiolarite-chert, tuff, neritic limestones, cherty limestone, spilite and basalt in a serpentinite paste is aquifuge medium I. Metagabbro, meta diorite, meta basalt, epidote-actinolite schist, chlorite-epidoschist, chloriticite, phyllite and serpentine are classified as aquifuge medium II (Table 2).

There are 5 synthetic faults developed parallel to each other in the north and Kizilcaoren in the west of the Banaz district. The southeast blocks of these faults developed in the N45°E direction have fallen. The slopes of these faults vary between 800 and 900, their offsets vary between 50 and 120 m and their lengths in the outcrop range between 3.5 and 6 km. These faults develop around the Muratdagi mélange. There are local travertine deposits along the fault zone in this region and they were developed under the control of faults. There are traces of thermal discharge in the zone (Simsek et al. 2010). Limonite and manganese ore levels are found in this region. Groundwater outflows and travertine formations present a lineament along the NE-SW line. The southeastern most of these faults extends for approximately 13 km in the N550E direction. This fault starts from Banaz district in the north and extends to Kizilcasogut village in the south. It is possible to see the traces of the fault at the southern part of this village. The fault forms the alluvial boundary in the region and limits the Banaz depression area. The faults in the Hamam stream region are a group consisting of two main faults developing in approximately the NE-SW direction and limiting the depression forming the creek, and synthetic faults developing depending on them (Gokgoz et al. 2011; Figure 1).

In addition, there are Hamambogazi and Kizilcaoren geothermal fields in the study area. The thermal waters in Hamambogazi rise from the intersection of the NE-SW trending fault and this fault and the other NW-SE trending fault. There are geothermal wells, thermal, mineral water and cold water resources in the field. The thermal resources in the Kizilcaoren area are lined up along a NE-SW trending line and there are generally travertine deposits around the springs. The temperatures of the thermal water springs in the area vary between 14.8 and 23.4 °C (Gokgoz et al. 2011; Figure 1).

In order to determine the effect of geogenic and anthropogenic elements on the groundwater in the basin, sample points were chosen from natural springs and wells. In particular, the distribution of lithological units in the basin was taken into consideration in the location selection of sample points. The results of the hydrochemical composition of groundwater are presented in Table 3. The temperature values of the groundwater samples ranged from 10 to 17.60 °C. The pH ranged from 7.41 to 8.40, indicating an alkaline type of groundwater. The pH values of all the samples are within the safe limit (6.5–8.5) as prescribed by WHO (2011). The EC (electrical conductivity) value ranges from 233 to 845 μS/cm. High EC recorded in the study area was determined in the sample (B4: 845 μS/cm) taken from the well in the Corum region. The increase in the amount of EC may be mainly attributed to pollutants from anthropogenic activities (human activities and agricultural activities). The EC values are higher due to the intense agricultural activity in the location where this sample was taken. Like EC, the TDS value (414 mg/l) of the sample is higher than other samples. The TDS (Total dissolved solid) in the groundwaters varies from 112 to 414 mg/l. The groundwater samples are of ‘freshwater type’ with TDS less than 1,000 mg/l according to the TDS classification (Fetter 1990). The TDS values of groundwater samples are in accordance with the permissible limits (600–100 mg/l) of WHO (2011). The salinity values ranged from ‰ 0.11 to 0.40. The hardness values vary from 6.15 to 43.39°F. The alkalinity has the property of water to react with the solute it contains and neutralize acid. Alkalinity in groundwater is due to the dissolved carbon dioxide species, bicarbonate and carbonate, and depends on pH values (Khan & Jhariya 2018). In the study area the total alkalinity (as ) values vary from 135 to 464.9 mg/l (Table 3).

Table 3

Results of analysis of springs in the study area (2023)

Sample ID .	.	B1 .	B2 .	B3 .	B4 .	B5 .	B6 .	B7 .	B8 .	B9 .	B10 .	Drinking Water Standarts .
Sampling Location .	.	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	TSI 266 (2005) .	WHO (2011) .
Sample Name		Camsu	Yesilyurt	Bahadir	Corum	Banaz	Kizilhisar	Erice	Ahat	Yazitepe	Yenice	(2005)	(2011)
Sampling Type		Spring	Spring	Spring	Well	Well	Spring	Spring	Well	Well	Spring
Sampling Date		10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022
Physical parameters
Location (UTM)	X(E)	350,728,864	350,736,477	350,742,417	350,750,895	350,738,953	350,728,966	350,730,506	350,742,309	350,750,690	350,749,695
	Y(N)	4,309,227	4,297,411	4,302,019	4,298,455	4,293,015	4,286,767	4,272,086	4,282,518	4,280,828	4,289,405
Altitude	Z (m)	1164	1119	1029	1080	962	941	902	1005	1093	1081
Depth of well	m				102	104			100	40
Temperature (T)	°C	10	13.90	15	16.70	16.30	14.60	17.60	15.90	13.50	12.10
Electrical conductivity (EC)	μS/cm	264	493	233	845	610	584	804	768	574	803	650–2500
pH		8.08	8.40	8.18	8.20	7.98	7.87	7.48	7.62	7.41	7.48	6.5–9.5	6.5–8.5
Total dissolved solids (TDS)	mg/l	125	238	112	414	302	283	395	375	279	393		600–1000
Salinity	‰	0.13	0.23	0.11	0.40	0.30	0.28	0.39	0.37	0.28	0.38
Hardness	°F	17.53	30.63	13.49	6.15	35.02	32.92	42.72	40.26	32.75	43.39
Alkalinity (as)	mg/l	115	320	135	464.9	325	340	439.9	330	320	388.9
Chemical parameters
Na+	mg/l	0.92	0.54	0.08	178.60	4.07	4.98	20.89	16.84	4.47	10.30	200	200
K+	mg/l	0.20	0.13	0.05	3.20	0.54	0.60	0.69	0.93	1.47	2.45		3000
Mg2+	mg/l	14.77	70.35	21.80	8.33	53.34	46.06	67.00	42.11	25.43	49.58
Ca2+	mg/l	45.85	6.73	18.09	10.92	52.33	55.92	60.66	91.82	89.25	92.08
Cl−	mg/l	0.99	2.13	0.90	4.79	7.52	8.21	32.58	12.79	9.91	16.35	250	250
	mg/l	71.98	8.28	4.48	16.46	37.98	14.62	9.69	111.87	14.54	67.18	250	500
	mg/l	140.30	341.60	164.70	555.10	396.50	414.80	536.80	402.60	390.40	475.80
	mg/l	–	24	–	6	–	–	–	–	–	–
Water type		CaMgHCO3SO4	MgHCO3	MgCaHCO3	NaHCO3	MgCaHCO3	MgCaHCO3	MgCaHCO3	CaMgHCO3SO4	CaMgHCO3	CaMgHCO3
Hydrochemical ratio
Ca2+/Mg2+	meq/l	1.88	0.06	0.50	0.80	0.60	0.74	0.55	1.32	2.13	1.13
CAI I	meq/l	−0.62	0.55	0.81	−57.09	0.10	0.00	−0.01	−1.10	0.17	−0.11
CAI II	meq/l	0.00	0.01	0.01	−0.81	0.00	0.00	0.00	−0.04	0.01	−0.01
Nitrogen compounds (* exceeding the limit value)
	mg/l	<0.01	<0.01	<0.01	0.37	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	0.5	3
	mg/l	<0.06	<0.06	<0.06	3.11*	<0.06	<0.06	<0.06	<0.06	<0.06	<0.06	0.5
	mg/l	0.89	0.90	1.25	4.44	16.38	5.51	12.28	17.26	19.17	20.98	50	50
Trace elements (* exceeding the limit value)
Al	μg/l	5	<1	3	12	<1	2	7	<1	<1	<1		200
As	μg/l	2.20	18.60*	1	28.20*	3.30	0.90	3.10	3.10	1.40	<0.50	10	10
B	μg/l	<5	8	<5	195	31	15	26	20	16	18	1000	2400
Ba	μg/l	4.87	2.87	2.82	272.54	73.06	163.04	501.32	50.20	235.24	127.89	700
Br	μg/l	8	15	6	23	23	38	149	48	27	36
Cd	μg/l	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	5	3
Cr	μg/l	1.90	21.70	7.90	<0.50	49.80	0.70	7.10	3.10	2.40	4.20	50	50
Cu	μg/l	0.50	0.10	2.40	0.20	0.70	0.20	0.40	1.10	0.30	0.50	2000	2000
Fe	μg/l	<10	<10	<10	87	<10	<10	<10	<10	<10	<10	200
Hg	μg/l	<0.10	<0.10	<0.10	<0.10	<0.10	<0.10	<0.10	<0.10	<0.10	<0.10		6
Mn	μg/l	0.56	<0.05	0.51	5.38	0.25	0.10	0.69	0.50	0.07	0.07	50	400
Ni	μg/l	<0.20	0.40	2.20	0.30	2.60	<0.20	3.60	<0.20	<0.20	0.70	20	70
Pb	μg/l	0.40	<0.20	0.20	<0.20	<0.20	<0.20	<0.20	<0.20	<0.20	<0.20	25	10
Sb	μg/l	2.07	0.26	0.14	0.14	0.07	<0.05	0.09	0.06	0.08	0.12	5	20
Se	μg/l	<0.50	<0.50	<0.50	<0.50	<0.50	0.90	2.10	0.60	<0.50	0.80	10	40
U	μg/l	0.45	0.05	0.30	0.10	0.80	2.34	7.75	3.51	1.90	4.60		30
Zn	μg/l	47.20	0.50	5.30	0.80	25.50	<0.50	<0.50	4.60	<0.50	0.60
Saturation index (SI) (* saturated value)
SIAnhydrite		−2.257	−4.106	−3.773	−4.276	−2.568	−2.947	−3.137	−1.902	−2.742	−2.152
SIAragonite		0.051*	−0.060	−0.060	−0.127	0.505*	0.432*	0.209*	0.363*	0.141*	0.243*
SIBarite		−0.718	−2.071	−2.205	−0.573	−0.096	−0.109	0.061*	0.169*	0.080*	0.428*
SICalcite		0.204*	0.090*	0.090*	0.020*	0.653*	0.581*	0.356*	0.511*	0.292*	0.395*
SIDolomite		1.141*	2.453*	1.513*	3.218*	2.577*	2.332*	2.029*	1.941*	1.285*	1.759*
SIGypsum		−1.738	−3.721	−3.397	−3.916	−2.204	−2.568	−2.784	−1.534	−2.354	−1.751
SIMagnesite		−0.714	0.753*	−0.176	1.613*	0.337*	0.147*	0.095*	−0.162	−0.621	−0.263
Isotopic charateristics (in 2023)
Oxygen − 18 (δ 18O)	δ(‰)	−10.57	−9.15	−10.86	−11.58	−8.81	−8.99	−9.13	−8.93	−8.95	−9.04
Uncertainty (δ 18O)		0.07	0.07	0.07	0.07	0.11	0.10	0.12	0.08	0.07	0.08
Deuterium (δ 2H)	δ(‰)	−66.85	−58.66	−68.78	−76.99	−57.92	−58.15	−58.62	−60.65	−61.23	−58.66
Uncertainty (δ 2H)		0.29	0.28	0.28	0.28	0.41	0.35	0.45	0.29	0.18	0.28
Tritium (3H)	TU	4.68	2.48	3.26	0.00	0.00	1.82	1.02	1.12	1.09	3.39	11.83
Uncertainty (3H)		0.79	0.70	0.74	0.64	0.66	0.70	0.72	0.68	0.59	0.73
D-excess (d)	‰	17.71	14.54	18.10	15.65	12.56	13.77	14.42	10.79	10.37	13.66
Isotopic charateristics (in 2008);Gokgoz et al., (2011)
Sample ID		C1	C2	C3	C4	C5	C6	C7	C8	C9	C10
Sampling Location		Banaz	Banaz	Banaz	Banaz	Banaz	Banaz	Banaz	Banaz	Banaz	Banaz
Sample Name		Cokran	Yesilyurt	Hallaclar	Kaplangi	Alaba	Hatipler	Muratli	Kusdemir	Oksuz	Hasankoy
Sampling Date		Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008
Oxygen-18 (δ 18O)	δ(‰)	−10.38	−8.85	−9.95	−8.44	−7.84	−8.02	−8.55	−8.79	−7.43	−9.1
Deuterium (δ 2H)	δ(‰)	−66	−61.1	−63.3	−57.8	−55	−55.5	−57.7	−57.6	−53.9	−61.2
Tritium (3H)	TU	6.79	5.02	6.30	5.61	5.43	0.00	5.61	5.45	0.00	0.00	11.83
D-excess (d)	‰	17.04	9.7	16.3	9.72	7.72	8.66	10.7	12.72	11.6	5.54
Electrical Conductivity (EC)	μS/cm	498	969	980	1232	1051	815	662	744	1049	995	650–2500

Sample ID .	.	B1 .	B2 .	B3 .	B4 .	B5 .	B6 .	B7 .	B8 .	B9 .	B10 .	Drinking Water Standarts .
Sampling Location .	.	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	Banaz .	TSI 266 (2005) .	WHO (2011) .
Sample Name		Camsu	Yesilyurt	Bahadir	Corum	Banaz	Kizilhisar	Erice	Ahat	Yazitepe	Yenice	(2005)	(2011)
Sampling Type		Spring	Spring	Spring	Well	Well	Spring	Spring	Well	Well	Spring
Sampling Date		10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022	10.05.2022
Physical parameters
Location (UTM)	X(E)	350,728,864	350,736,477	350,742,417	350,750,895	350,738,953	350,728,966	350,730,506	350,742,309	350,750,690	350,749,695
	Y(N)	4,309,227	4,297,411	4,302,019	4,298,455	4,293,015	4,286,767	4,272,086	4,282,518	4,280,828	4,289,405
Altitude	Z (m)	1164	1119	1029	1080	962	941	902	1005	1093	1081
Depth of well	m				102	104			100	40
Temperature (T)	°C	10	13.90	15	16.70	16.30	14.60	17.60	15.90	13.50	12.10
Electrical conductivity (EC)	μS/cm	264	493	233	845	610	584	804	768	574	803	650–2500
pH		8.08	8.40	8.18	8.20	7.98	7.87	7.48	7.62	7.41	7.48	6.5–9.5	6.5–8.5
Total dissolved solids (TDS)	mg/l	125	238	112	414	302	283	395	375	279	393		600–1000
Salinity	‰	0.13	0.23	0.11	0.40	0.30	0.28	0.39	0.37	0.28	0.38
Hardness	°F	17.53	30.63	13.49	6.15	35.02	32.92	42.72	40.26	32.75	43.39
Alkalinity (as)	mg/l	115	320	135	464.9	325	340	439.9	330	320	388.9
Chemical parameters
Na+	mg/l	0.92	0.54	0.08	178.60	4.07	4.98	20.89	16.84	4.47	10.30	200	200
K+	mg/l	0.20	0.13	0.05	3.20	0.54	0.60	0.69	0.93	1.47	2.45		3000
Mg2+	mg/l	14.77	70.35	21.80	8.33	53.34	46.06	67.00	42.11	25.43	49.58
Ca2+	mg/l	45.85	6.73	18.09	10.92	52.33	55.92	60.66	91.82	89.25	92.08
Cl−	mg/l	0.99	2.13	0.90	4.79	7.52	8.21	32.58	12.79	9.91	16.35	250	250
	mg/l	71.98	8.28	4.48	16.46	37.98	14.62	9.69	111.87	14.54	67.18	250	500
	mg/l	140.30	341.60	164.70	555.10	396.50	414.80	536.80	402.60	390.40	475.80
	mg/l	–	24	–	6	–	–	–	–	–	–
Water type		CaMgHCO3SO4	MgHCO3	MgCaHCO3	NaHCO3	MgCaHCO3	MgCaHCO3	MgCaHCO3	CaMgHCO3SO4	CaMgHCO3	CaMgHCO3
Hydrochemical ratio
Ca2+/Mg2+	meq/l	1.88	0.06	0.50	0.80	0.60	0.74	0.55	1.32	2.13	1.13
CAI I	meq/l	−0.62	0.55	0.81	−57.09	0.10	0.00	−0.01	−1.10	0.17	−0.11
CAI II	meq/l	0.00	0.01	0.01	−0.81	0.00	0.00	0.00	−0.04	0.01	−0.01
Nitrogen compounds (* exceeding the limit value)
	mg/l	<0.01	<0.01	<0.01	0.37	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	0.5	3
	mg/l	<0.06	<0.06	<0.06	3.11*	<0.06	<0.06	<0.06	<0.06	<0.06	<0.06	0.5
	mg/l	0.89	0.90	1.25	4.44	16.38	5.51	12.28	17.26	19.17	20.98	50	50
Trace elements (* exceeding the limit value)
Al	μg/l	5	<1	3	12	<1	2	7	<1	<1	<1		200
As	μg/l	2.20	18.60*	1	28.20*	3.30	0.90	3.10	3.10	1.40	<0.50	10	10
B	μg/l	<5	8	<5	195	31	15	26	20	16	18	1000	2400
Ba	μg/l	4.87	2.87	2.82	272.54	73.06	163.04	501.32	50.20	235.24	127.89	700
Br	μg/l	8	15	6	23	23	38	149	48	27	36
Cd	μg/l	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	5	3
Cr	μg/l	1.90	21.70	7.90	<0.50	49.80	0.70	7.10	3.10	2.40	4.20	50	50
Cu	μg/l	0.50	0.10	2.40	0.20	0.70	0.20	0.40	1.10	0.30	0.50	2000	2000
Fe	μg/l	<10	<10	<10	87	<10	<10	<10	<10	<10	<10	200
Hg	μg/l	<0.10	<0.10	<0.10	<0.10	<0.10	<0.10	<0.10	<0.10	<0.10	<0.10		6
Mn	μg/l	0.56	<0.05	0.51	5.38	0.25	0.10	0.69	0.50	0.07	0.07	50	400
Ni	μg/l	<0.20	0.40	2.20	0.30	2.60	<0.20	3.60	<0.20	<0.20	0.70	20	70
Pb	μg/l	0.40	<0.20	0.20	<0.20	<0.20	<0.20	<0.20	<0.20	<0.20	<0.20	25	10
Sb	μg/l	2.07	0.26	0.14	0.14	0.07	<0.05	0.09	0.06	0.08	0.12	5	20
Se	μg/l	<0.50	<0.50	<0.50	<0.50	<0.50	0.90	2.10	0.60	<0.50	0.80	10	40
U	μg/l	0.45	0.05	0.30	0.10	0.80	2.34	7.75	3.51	1.90	4.60		30
Zn	μg/l	47.20	0.50	5.30	0.80	25.50	<0.50	<0.50	4.60	<0.50	0.60
Saturation index (SI) (* saturated value)
SIAnhydrite		−2.257	−4.106	−3.773	−4.276	−2.568	−2.947	−3.137	−1.902	−2.742	−2.152
SIAragonite		0.051*	−0.060	−0.060	−0.127	0.505*	0.432*	0.209*	0.363*	0.141*	0.243*
SIBarite		−0.718	−2.071	−2.205	−0.573	−0.096	−0.109	0.061*	0.169*	0.080*	0.428*
SICalcite		0.204*	0.090*	0.090*	0.020*	0.653*	0.581*	0.356*	0.511*	0.292*	0.395*
SIDolomite		1.141*	2.453*	1.513*	3.218*	2.577*	2.332*	2.029*	1.941*	1.285*	1.759*
SIGypsum		−1.738	−3.721	−3.397	−3.916	−2.204	−2.568	−2.784	−1.534	−2.354	−1.751
SIMagnesite		−0.714	0.753*	−0.176	1.613*	0.337*	0.147*	0.095*	−0.162	−0.621	−0.263
Isotopic charateristics (in 2023)
Oxygen − 18 (δ 18O)	δ(‰)	−10.57	−9.15	−10.86	−11.58	−8.81	−8.99	−9.13	−8.93	−8.95	−9.04
Uncertainty (δ 18O)		0.07	0.07	0.07	0.07	0.11	0.10	0.12	0.08	0.07	0.08
Deuterium (δ 2H)	δ(‰)	−66.85	−58.66	−68.78	−76.99	−57.92	−58.15	−58.62	−60.65	−61.23	−58.66
Uncertainty (δ 2H)		0.29	0.28	0.28	0.28	0.41	0.35	0.45	0.29	0.18	0.28
Tritium (3H)	TU	4.68	2.48	3.26	0.00	0.00	1.82	1.02	1.12	1.09	3.39	11.83
Uncertainty (3H)		0.79	0.70	0.74	0.64	0.66	0.70	0.72	0.68	0.59	0.73
D-excess (d)	‰	17.71	14.54	18.10	15.65	12.56	13.77	14.42	10.79	10.37	13.66
Isotopic charateristics (in 2008);Gokgoz et al., (2011)
Sample ID		C1	C2	C3	C4	C5	C6	C7	C8	C9	C10
Sampling Location		Banaz	Banaz	Banaz	Banaz	Banaz	Banaz	Banaz	Banaz	Banaz	Banaz
Sample Name		Cokran	Yesilyurt	Hallaclar	Kaplangi	Alaba	Hatipler	Muratli	Kusdemir	Oksuz	Hasankoy
Sampling Date		Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008	Oct.- 2008
Oxygen-18 (δ 18O)	δ(‰)	−10.38	−8.85	−9.95	−8.44	−7.84	−8.02	−8.55	−8.79	−7.43	−9.1
Deuterium (δ 2H)	δ(‰)	−66	−61.1	−63.3	−57.8	−55	−55.5	−57.7	−57.6	−53.9	−61.2
Tritium (3H)	TU	6.79	5.02	6.30	5.61	5.43	0.00	5.61	5.45	0.00	0.00	11.83
D-excess (d)	‰	17.04	9.7	16.3	9.72	7.72	8.66	10.7	12.72	11.6	5.54
Electrical Conductivity (EC)	μS/cm	498	969	980	1232	1051	815	662	744	1049	995	650–2500

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Calcium, magnesium, sodium and potassium concentrations of groundwaters ranged from 6.73 to 92.08 mg/l, 8.33 to 67.00 mg/l, 0.08 to 178.60 and 0.05 to 3.20 mg/l, respectively (Table 3). The desirable values of K⁺, Na⁺, and are 200, 3,000, and 500 mg/l as per WHO (2011) standard, respectively. Also, chlorine, sulfate, bicarbonate and carbonate concentration values varied from 0.90 to 32.58 mg/l, 4.48 to 111.87 mg/l, 140.30 to 555.10 and 6 to 24 mg/l, respectively (Table 3). The desirable value of Cl⁻ is 250 mg/l as per the WHO (2011) standard. The cations and anions of groundwater samples in the basin are within the desirable limits of the standard. The order of cation abundance is Ca²⁺ > Mg²⁺ > Na⁺ > K⁺ and the order of anion abundance is > > Cl⁻ > ⁠.

The Durov plot (1948) defines water type and the hydrochemical processes. The plot is used to graphically illustrate cations and anions concentrations, related to pH and TDS values. The Durov plot shows the spatial distribution of different hydrochemical facies within the study area and supports the water type. According to ion balance diagrams, the majority of the samples are dominated by bicarbonate and calcium ions. However, sample B4 presents the highest amount for the sodium concentration (Figure 2(b)). This high Na⁺ concentration was due to high salinity, water treatment chemicals, sewage effluents and mineral deposits (WHO 2011).

The (Ca²⁺ + Mg²⁺) vs. (⁠ + ⁠) scatter diagram of the study area observed that the groundwater samples are generally collected around and below the equiline 1:1 line except for a few samples (B2 and B4 samples) (Figure 6(a)). This represents the dominant process in the supply of calcium ions to groundwater, namely silicate weathering. The weathering is the main source for the dissolutions of calcite, dolomite and gypsum are the dominant reactions in a system. Ion exchange tends to shift the points to the right due to an excess of + (Cerling et al. 1989; Fisher & Mulican 1997). The B2 sample point lies above the equiline 1:1 line and the sample shows carbonate weathering and the magnesium and bicarbonate concentration values of this sample are higher than the other samples (Table 3). Ca²⁺/Mg²⁺ ratios of most of the groundwater samples (40%) having a ratio greater than 1 indicate the dissolution of calcite and dolomite. However, in sample B9, the Ca/Mg ratio is above 2 (Ca²⁺/Mg²⁺ = 2.13 meq/l), indicating that silicate mineral weathering was effective for this sample (Table 3). If the Ca/Mg ratio is higher than 2, it indicates the dissolution of silicate minerals that contribute Ca and Mg to the groundwater (Katz et al. 1998).

In Figure 6(b), the samples show a negative linear trend of the (Ca²⁺ + Mg²⁺)-(⁠ + ⁠) versus (Na⁺-Cl⁻) scatter diagram and they spread below the linear trend. If ion exchange is the main process in the system, the plot should form a slope of −1.0 (Fisher & Mulican 1997). The line slope is indicated −0.953 and it shows a strong correlation (R² = 0.9896) in Figure 6(b). The (Ca²⁺ + Mg²⁺)-(⁠ + ⁠) provides the sum of the cations Ca and Mg from sources other than their respective carbonates and sulfates, whereas Na⁺-Cl⁻ provides the total concentration of the cations K and Na from sources other than their respective chlorides in the system (Fisher & Mulican 1997).

Sodium and bicarbonate concentrations in groundwater vary from 0.08 to178.60 mg/l and 140.3 to 555.1 mg/l, respectively (Table 3). The Na vs. scatter diagram shows most of the sample points above the 1:1 equiline (Figure 6(c)). The increase in ion concentration compared to Na⁺ ion concentration in the groundwater indicates the dominancy of the silicate weathering process; it is well supported by a high concentration of (Fisher & Mulican 1997; Elango et al. 2003). In the plot for (Ca²⁺ + Mg²⁺) versus ⁠, the sample points are clustered around equiline 1:1, indicating the predominance of alkali earth over bicarbonate due to silicate weathering. Minor representations in bicarbonate are also due to the reaction of the feldspar minerals with carbonic acid in the presence of water, releasing (Elango et al. 2003) (Figure 6(d)).

The groundwater samples were located close to and above the Na⁺ + K⁺ = 0.5TC⁺ line in the (Na⁺ + K⁺) vs. TC⁺ diagram. This distribution observed in the samples shows that mainly Na⁺ and K⁺ ions contribute to groundwater, with the contribution of silicate weathering in hydrogeochemical processes (Stallard & Edmond 1983; Sarin et al. 1989). Na⁺ ion value (178.60 mg/l) of the B4 is higher than other samples (Table 3; Figure 6(e)). Similarly, the plot for (Ca²⁺ + Mg²⁺) versus TC⁺ indicates all samples seem that it is almost in line with Ca²⁺ + Mg²⁺ = TC⁺ and Ca²⁺ + Mg²⁺ = 0.5TC⁺ and it exhibits a linear distribution in the positive direction (Figure 6(f)). It is thought that this increase in Mg⁺² and Ca⁺² ions may be due to the weathering of silicate minerals.

This directly indicates a base (cation-anion) exchange reaction and the values of the indices can be negative or positive. If an exchange occurs between Mg²⁺/Ca²⁺ and Na⁺/K⁺ ions in groundwater, chloro-alkaline indices take a positive value; if a reverse ion exchange occurs, the indices take a negative value (Schoeller 1965). That is, the displacement of K⁺ and Na⁺ ions in water with Mg²⁺ and Ca²⁺ ions in the rock is explained by positive ion exchange. Conversely, if the index is negative, it means that the Ca⁺² and Mg⁺² ions in the water and the Na⁺ and K⁺ ions in the rock are replaced. In groundwaters, CAI I values range from −57.09 to 0, while CAI II values range from −0.81 to 0.00 (Table 3). The calculated CAI values for 50% of the groundwater of the region were negative suggesting reverse ion exchange. It is clearly visible that there is reverse ion-exchange dominant in samples B1, B4, B7, B8, and B10. This ion exchange may be due to cation exchange and residual time in the aquifer. The calculated negative CAI I and II values indicate the Na⁺ and K⁺ ions of the rocks are replaced by the Mg²⁺ and Ca²⁺ ions of the waters. In samples with positive values, there is ion exchange. On the other hand, 50% of the samples showed positive CAI values suggesting that they had ion exchange. Samples with ion exchange are B2, B3, B5, B6 and B9.

The water is not saturated with the relevant mineral (mineral is dissolving).

Saturation index values (SI_Anhydrite, SI_Aragonite, SI_Barite, SI_Calcite, SI_Dolomite, SI_Gypsum and SI_Magnesite) determined according to the discharge temperatures of groundwater in the study area and the pH value measured in the field are given in Table 3. The saturation state of minerals is in the following order: SI_Dolomite > SI_Calcite > SI_Aragonite > SI_Magnesite > SI_Barite. The SI_Dolomite and SI_Calcite values are 1.141–3.218 and 0.020–0.653, respectively. The results of the calculation saturation index show that all of the water samples were saturated with respect to carbonate minerals (dolomite and calcite). Additionally, 70% of the samples are saturated with aragonite mineral. But, water samples are undersaturated with respect to sulfate minerals (anhydrite and gypsum). However, samples B7, B8, B9 and B10 were saturated with barite minerals. In addition, 50% of the samples are saturated with magnesite minerals.

Isotope techniques are used to determine the origin of groundwaters (metamorphic, magmatic, meteoric, etc.), age, feeding areas, residence and renewal times in aquifers, and mixing ratios of water from different aquifers and/or different springs (Cifter & Sayin 2002). The isotopic (oxygen 18-δ¹⁸O, deuterium-δ²H and tritium-²H) analyses were made to identify residence time and the zones of recharge of spring and well waters in the study area. Stable isotope analyses (¹⁸O and ²H) are a useful tool to determine the level of recharge in the system and the origin of the groundwater. A stable isotope study has not been done before in the study area. The data obtained as a result of isotopic analyses in this study were used to better understand the origin, recharge level and area and the mixing ratios of different waters of water bodies. Spatial distribution in the study area was taken into account in the selection of sample points in order to determine the origin of groundwater by isotopic analysis. Isotope analyses were performed at all points in the study area. Additionally, the results obtained were compared with the isotope analysis results conducted by Gokgoz et al. (2011) in 2008.

In addition, radioactive tritium isotope analysis data were used to investigate the behavior of the hydrogeological system in the study area. The radioactive tritium isotope is an important tool in determining the groundwater flow rate and transit time and the surface water–groundwater relationship. Also, tritium is a radioactive isotope that decays depending on the residence time of groundwater in the reservoir. Modern groundwaters are then younger than about 1945 years relative to the mid-1990s. Tritium-free groundwaters are considered submodern or older. Deep and slow circulating groundwaters can have low tritium values (<1 TU). The ion content of these waters, which remain in circulation for a long time, increases due to the rock-water interaction. Groundwaters with high tritium values can reflect shallow and fast circulation, and these groundwaters can result in short residence times (Clark & Fritz 1999; Gunay 2006; Jeelani et al. 2015).

In this section, the toxicity levels of heavy metals on human health were determined, taking into account intake through drinking water and dermal adsorption. Calculations were made using the US EPA method to determine the cancer risks of heavy metals detected in water samples collected in the study area. According to the results, the concentrations of arsenic in samples B2 and B4, boron in sample B4, chromium in sample B5 and uranium in sample B7 have high values. Nitrate contents are above 10 mg/l in 5 samples (B5, B7, B8, B9 and B10) and reflect the anthropogenic effect. In this study, a health risk assessment was made for As, NO₃, Cr, B and U parameters that may pose a health risk, considering the pollution parameters in the samples taken from the study area.

The average daily dose is the chronic daily intake of water. The average daily dose (ADD) values of As, NO₃, Cr, U and B elements were calculated as oral and dermal in the adults and children (Table 5). For adults, ADD_oral values vary between 1.27 E-01 and 8.57 E-06, and ADD_dermal values vary between 1.05 E-02 and 3.21 E-07, while for children, ADD_oral values vary between 2.34 E-01 and 7.14 E-06, and ADD_dermal values vary between 1.11 E-03 and 7.59 E-07. ADD data, non-carcinogenic risk (HQ and HI) and carcinogenic risk (CR) values are also calculated. Using the obtained ADD data, hazard quotient (HQ), hazard index (HI) and cancer risk (CR) values that can occur through oral and dermal ingestion were calculated, taking adult and child individuals (Tables 6 and 7). HQ > 1 value indicates the negative effects of toxic chemicals and heavy metals in water on human health (USEPA 2001, 2004). The closer the values are to 1, the greater the risk of not causing cancer. Cancer risk (CR) is defined as the risk of developing any type of cancer due to exposure to carcinogenic elements in surface and ground water, based on the average lifespan of a person. The prescribed limit of CR by US EPA is 1.0 E-06 (1 chance in 1.000,000 lifetime exposure) to 1.0 E-04 (1 chance in 10.000-lifetime exposure), and unacceptable if the CR value exceeds 1.0 E-04 (US EPA, 1989; Lim et al. 2008; Li & Zhang 2010; Davraz et al. 2016; Aghlmand et al. 2021; Davraz & Batur 2021).

As given in Table 5, the values of ADD_oral for adults in mg kg⁻¹ day⁻¹ vary between 5.31 E-04 and 9.43 E-05 for As, 1.27 E-01 and 3.57 E-02 for NO₃, 1.42 E-03 and 8.86 E-05 for Cr, 1.00 E-0 and 8.57 E-06 for U, 1.5.57 E-03 and 8.86 E-04 for B. The hazard quotients (HQ) and hazard indices (HI) that may occur through oral intake in adults were determined for As, NO₃, Cr, U and B elements (Table 6). The HQ_oral values calculated are less than 1 (HQ <1). This shows that these elements will not have a negative impact on water resources when used as drinking water. In the hazard coefficient calculation for the element As, it is seen that the HQ values of samples B2 (1.77 E + 00) and B4 (2.69 E + 00) are greater than 1 (HQ >1). In this case, it can be said that this water may pose a risk when used as drinking water. Total HI values vary between 1.96 E-01 and 2.80 E + 00. Total HI values for As, B, NO₃, Cr, U and B elements are greater than 1 in samples B2 (2.00 E-07), B4 (2.80 E-07) and B5 (1.09 E-07). This shows that the water in the samples may have negative health effects when used as drinking water. It is seen that the cancer risk values calculated for As, Cr and U elements when used as drinking water vary between 1.03 E-04 and 5.71 E-07 (Table 6). Except for the cancer risk value determined for the samples B2 and B4, the As, Cr and U cancer risk values of other samples do not exceed the acceptable value of 1.0 E-04 (Table 5). However, the CR_As values in samples B2 (2.97 E-07), B4 (1.21 E-07) and CR_U value in sample B2 (5.71E-07) were higher than the tolerable values. The research from the United States Environmental Protection Agency (USEPA) has shown that people who drink high arsenic water for a long time have a significant increase in the risk of visceral cancers such as those of the liver, kidney, lung, bladder, and skin (USEPA, 2018). Uranium (U) is a naturally occurring radioactive element that is commonly present in groundwater. Also, the concentration of U in groundwater also depends upon regional geology and structure. Generally, siliceous igneous rocks contain higher U which increases further with an increase in the silica content as seen in pegmatites as compared to basalts (Langmuir 1997). Studies show that the contribution of ingested U through food stuff accounts for 15%, whereas drinking water contributes 85% of ingested U (Tanner 1978). Hence, the health risk due to the consumption of uranium-containing groundwater poses a greater risk compared to other causes (Adithya et al. 2019). This shows that the use of these waters as drinking water throughout life may pose a cancer risk. For this reason, waters in the Yesilyurt (B2) and Corum (B4) regions should not be drunk due to the risk of cancer.

ADD_dermal values for adults were calculated for As, Cr and NO₃ elements. The values range from 1.19 E-05 to 8.98 E-07 for As, 1.05 E-02 to 8.01 E-04 for Cr and 1.01E-05 to 8.98 E-07 for NO₃ (Table 5). For adults, the HQ_dermal and total HI values calculated for the As, Cr and NO₃ elements, depending on the oral use of water resources and dermal exposure are less than 1 (HQ <1) (Table 6). Also, the carcinogenic risk assessment for adults was made. The values of CR values for different metals (As, Cr and U) used for carcinogenic risk assessment are listed in Table 5. It is seen that the CR values calculated dermally for As, Cr and U elements are below the tolerable values (1.0 E-06 and 1.0 E-04).

Table 4 summarizes the calculated ADD_oral values for the consumption of drinking water by children. The results suggest that in the study area, the ADD_oral values ranged from 2.66 E-04 to 7.14 E-06, 1.75 E to 01–7.87 E-02, 1.13 E-04 to 7.14 E-06, 1.11 E to 04–7.14 E-07 and 2.79 E to 03–7.00 E-05 mg kg⁻¹ day⁻¹ for As, NO₃, Cr, U and B, respectively (Table 5). It is seen that HQ_oral and HI values for As, B, Cr, NO₃ and U parameters are less than 1 for children when used as drinking water (Table 7), except for the B4 sample (1.40 E + 00). It is seen that the CR values for use as drinking water calculated for As, Cr and U elements in individual children vary between 3.99 E-04 and 6.04 E-07, 1.55 E-04–5.00 E-06 and 1.09 E-05–5.71 E-07, respectively. It is seen that the CR_U values of the B2 (2.86 E-07) and B4 (5.71 E-07) samples are above the acceptable values. Also, the CR_As values in samples B2 (3.99 E-07) and B4 (6.04 E-07) were higher than the tolerable values. There is a possibility of a cancer risk in children with long-term use of the water taken from these samples. For this reason, water from risky B2 and B4 samples should not be consumed.

ADD_dermal values for the child are calculated for As, NO₃, Cr, U and B elements and are presented in Table 5. The HQ_dermal and total HI values were calculated for As, NO₃ and Cr elements (Table 7). HQ_dermal and total HI values are less than 1 (HQ <1). CR values were calculated for Cr and As elements, which are elements that can be exposed to children through the dermal route. CR_Cr values are between 1.80 E-04 and 8.68 E-06 and do not exceed the limit values. However, in the cancer risk calculations for the element arsenic, which can be exposed to the dermal route in children, it was observed that 50% of the samples were above tolerable limits. In particular, samples B1 (7.28 E-07), B3 (3.31 E-07), B6 (2.98 E-07), B9 (4.63 E-07) and B10 (1.65 E-07) are risky. The non-carcinogenic effects of arsenic on the human body are mainly manifested in skin damage or circulatory problems (USEPA, 2018). These samples can be considered dangerous in terms of CR_As (Table 7).

Drinking water in the Banaz (Usak) basin is provided by natural spring water and wells. There are approximately 700 wells drilled by official and private individuals in the basin. Well depths range from 40 to 270 m. Wells in the basin are generally located on alluvial and Upper Miocene-aged conglomerate, sandstone, mudstone and claystone units. There are approximately 250 shallow wells in the basin. In addition to drinking water from wells in the basin, it is also used for using and irrigation purposes. Furthermore, the study area is rich in natural springs. The springs of Camsu, Yesilyurt, Bahadir, Kizilhisar, Erice, Yenice, Karacahisar, Kizilcasogut and Ayvacik settlements are very productive. In order to determine the hydrogeochemical quality of the waters in the region, water samples were taken from wells and natural spring waters in these settlements. The quality of groundwater in the basin is affected by natural geochemical processes like rock water interaction, evaporation, dissolution, ion exchange and anthropogenic-induced activities like industrial and agricultural. In fact, drinking water taken from wells and natural springs throughout the basin is suitable for drinking water standards, as a result of the analysis. In particular, it is observed that groundwater is chemically enriched in Ca²⁺, Mg²⁺ and ions due to the interaction of metamorphic and sedimentary rocks spreading in the basin. In isotopic terms, the waters in the basin are waters of meteoric origin that are under the influence of annual precipitation. In addition, drinking water in the basin is exposed to point pollutants in some regions. In particular, in terms of heavy metal pollution, drinking water in some regions of the basin has been affected by elements such as arsenic. Drinking water in regions where agricultural activities are intense has also been affected by nitrogen derivatives.

The most important of the water resources of the basin is the Cokran spring, which comes out of a cave inside the karst Paleozoic marbles at an elevation of 1,346 m on the foot of the Murat Mountain. The karstic spring is discharged at the intersection of the Karacahisar Fault and the Calustu Fault. The electrical conductivity value of the spring is 264 μS/cm. This water is mixed with the Cokran Acisu spring, which discharges from the schists in the same cave and has a relatively low flow rate. The Cokran spring has a flow rate of 80 l/s. This spring water supplies the drinking water of Usak with 30 l/s and the Banaz settlement area with 50 l/s. In the basin, the Cokran spring water is combined with the waters of 6 wells belonging to the municipality and transmitted to drinking water networks.

The drinking waters of the basin comply with the TSI 266 (2005) and WHO (2011) drinking water standards in terms of physical and chemical properties. In addition, groundwaters in the basin were evaluated in terms of nitrogen derivatives and heavy metal pollution. Nitrate and nitrite values vary from 0.89 to 20.98 mg/l and <0.01 to 0.37 mg/l, respectively. These values are below the limits of the standards. values vary from <0.06 to 3.11 mg/l. The highest concentrations were observed at the sample (B4) value showed above the TSI 266 (2005) standard permissible limit of 0.5 mg/l. The sampling location, Corum is confined to the agricultural area; application of fertilizer and domestic wastes might have caused higher concentrations. Also, TDS is a parameter related to EC and these parameters are used to understand the amount of pollution present in the groundwater. B4 sample EC and TDS values 845 μS/cm, 414 mg/l, respectively. These values are higher than other samples. This may be the reason for the increasing trend of As. The arsenic content of the sample is 28.20 μg/l. Also, the arsenic content in the B2 sample is 18.60 μg/l. The values exceed the WHO (2011) and TSI 266 (2005) standards permissible limit of 10 μg/l. The main source of the increase in arsenic content in the B4 and B2 water samples taken from spring and the well drilled in the Neogene sediments and volcanics may be due to the water–rock interaction in the volcanics. Especially in sample B4, while the interaction time with the rocks in its location increases due to the effect of deep and slow circulation, the ion content in it also increases. The increase in the arsenic content in question was also revealed in cancer risk calculations made in terms of health risk assessment. The high arsenic groundwater is dangerous for drinking, because arsenic is a known carcinogen and can lead to a wide range of health problems in humans (Smedley & Kinniburgh 2002). Therefore, these waters should not be used for drinking purposes.

Determining the quality of groundwater used as drinking water in a region highlights sustainable water management efforts in that region. Therefore, in order to ensure good water management in a basin, it is possible to determine the quality of the groundwater in that basin, control its pollution and eliminate possible exposures. The effects of anthropogenic (agricultural, industrial, human, etc.) and geogenic elements on the groundwater in the basin were determined by geological, hydrogeological and hydrogeochemical studies. Also, isotopic and health risk assessment studies were carried out in the Banaz (Usak) basin with the objective of identifying the geochemical processes and their relation to groundwater quality. The chemical composition of groundwater in the basin is influenced by rock-water interaction ion exchange and anthropogenic pollution. The dominant anion is and cations are Mg²⁺ and Ca²⁺ in groundwater samples in the basin. It can be explained that silicate minerals decompose by controlling calcium, magnesium and sodium ions. Water–rock interaction processes have a significant impact on groundwater in the basin. Generally, the groundwater samples are found to be good for drinking in terms of physical parameters. However, in terms of ammonium and arsenic content, Corum and Yesilyurt areas are not suitable for drinking water due to pollution which may be caused by excessive usage of chemical fertilizers along with geogenic and anthropogenic sources. Moreover, the study of tritium and stable isotopes in groundwaters in the Banaz basin has revealed characteristic features and origin of waters. A good correlation between δ¹⁸O and δ²H is observed for waters in the basin in both years. It is concluded that the springs are recharged by meteoric water according to the stable isotopes. Tritium content in the plain waters of Banaz basin is found to be above detection limits (i.e. 1TU) indicating a recent recharge. The deuterium excess values in groundwaters are generally high at the basin due to the same origin in 2008 and 2023. The present isotope results of groundwaters are important for comparison isotope variability in the other adjacent basins. Generally, the water samples were saturated with respect to carbonate minerals (calcite, dolomite and aragonite) and unsaturated with respect to sulfate minerals (gypsum and anhydrite). The carcinogenic risks were calculated based on the measured heavy metals (As, Cr, and U) in the study area. The carcinogenic risk calculation results for children and adults through oral (As, Cr and U) and dermal (As and Cr) contact were determined. It was determined that elements As and U carry a cancer risk with oral intake of the water of the samples B2 and B4 sample in children and adults. For this reason, it is dangerous for adults and children to take the water of B2 (Yesilyurt) and B4 (Corum) samples orally. In addition, it has been determined that dermal exposure to water of samples B1, B3, B6, B9 and B10 can be dangerous in children. CR values have indicated that children have a higher risk of cancer than adults. The health risk assessment results of this research present that there was a cancer risk from the contaminants to residents through the oral ingestion and dermal contact routes in the drinking water in some locations of the region. For this reason, pollution elements affecting groundwater in these regions need to be controlled or eliminated.

The author is thankful to the staff in the Banaz Municipality Mayor's office for his valuable help and support.

The author contributed to the study through data collection, conception, design, research and preparation of the manuscript.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.