Potential health risk assessment related to arsenic pollution and hydrogeochemistry of groundwaters in Akşehir and surroundings (Konya/Turkey)

Groundwater is an important water resource used for drinking, domestic and agricultural activities in Akşehir and surroundings. However, intensive agricultural and human activities in the region adversely affect groundwater quality. In this study, 31 water samples were collected from wells. According to the Piper diagram, groundwater in the study area was in the Ca–Mg–HCO3 and Ca–HCO3 water facies. As a result, it is not appropriate to use groundwater as drinking water in the study area in terms of trace elements and pollutant analysis results of water samples compared to limit values determined by WHO and ITHASY drinking water guidelines. The arsenic concentration in groundwater was studied in detail. The origin and concentration of arsenic in groundwater is associated with agricultural activities and pesticides in the region. Accordingly, a health risk assessment was carried out for the use of groundwater in the study area as drinking water. The results for all samples analyzed indicate that the groundwater concerned was not suitable for drinking purposes because of arsenic concentrations which exceeded maximum acceptable levels.


INTRODUCTION
Environmental pollution is one of the most important obstacles to the sustainable development of countries.
Water in our country, as in the whole world, is an extremely valuable, economic and strategic natural resource. In total, 95% of domestic wastewater and 70% of industrial wastewater are discharged to receiving environments without treatment in underdeveloped and developing countries. As a result, clean water sources become contaminated and access to safe drinking water becomes a major problem.
Groundwater is especially preferred as drinking water because it is less frequently polluted (Sȩner et al. ).
Therefore, about half of the world's drinking water is taken from groundwater aquifers (Li et al. ). However, groundwater quality and chemistry are controlled both by natural processes (weathering and soil erosion) and by anthropogenic inputs (agricultural activities, municipal and Stream, Adıyan Stream, Nadir Stream, Aksȩhir Stream and Saray Stream) in the study area discharge into Aksȩhir Lake.
The most important surface water in the region is Egȓigöz stream and it continues its flow by recharging from Sultandagları and discharges into Aksȩhir Lake. The discharge parameters of the lake are evaporation and usage of irrigation water. There are not many springs in the study area.
The main water source in the study area for domestic, industrial and agricultural use is groundwater. Agricultural activities are very common in the region and the total irrigation area is 115.8 km 2 .
Aksȩhir district, which includes the study area, has a usage area of 85.300 ha. There are agricultural lands in 40.31% of the total area of use, forest areas in 27.51% and meadow-pasture areas in 6.17%. There is one solid waste storage facility and ten industrial factories for bricks, sunflower oil, biscuits, tomato paste, flour, marble, electrical wire, tractor spare parts, burner and dairy products in the study area. Apart from these, intensive agricultural activities are carried out in the region (ADR ).  (Isparta, Turkey). Software was used to analyze chemical data. The charge-balance error for the samples was calculated to confirm accuracy of the chemical analysis, and it was less than 5%, which is within the limits of acceptability.
Basic descriptive statistical analysis used SPSS (Version 15.0, SPSS Inc., Chicago, IL). The spatial distribution of trace elements in groundwater and potential health risks in society were prepared using ArcGIS 10.5 software and spatial analyst extensions.

Exposure assessment
Arsenic can enter the human body in many different ways such as through the food chain, dermal contact and inhalation. However, the effect of intake by all other means can be neglected compared to oral intake. Therefore, exposure to As T is measured in two main ways: oral (ingestion) and dermal (absorption) (Ehsan et al. ). USEPA () recommends a lifelong average daily dose as an exposure measure to estimate a person's daily exposure. The following equation is representation of daily exposure for the ingestion route modified from Chrostowski () (Equation (1)):  (3)) given below.
According to the formula, the carcinogen risk is R cancer , chronic daily intake (mg/kg/day) is ADD and pollutant's slope factor (mg/kg/day) À1 is SF (Equation (3)). The slope factor (SF) of the contaminant for As T was specified by USEPA () as 1.5 mg/kg/day.

Hydrochemistry
Groundwater quality and chemical properties depend on the properties of the aquifer rocks and anthropogenic inputs. Therefore, hydrochemical properties and water quality information are needed to determine the suitability of the water for different purposes (Adimalla  agricultural activities in the study area. In addition, TDS values of groundwater range from 150.00 to 1,780.00 (mg/L).
The TDS limit value stated in the drinking water guidelines is 500 mg/L. Accordingly, samples S19, S21, S23, S24, S25, S26, S28, S29, S30 and S31 in the study area are not suitable for use as drinking water.
According to analysis results, the Ca ion concentration of the water samples in the study area ranges from 40.00 The main source of NO 3 is wastewater due to agricultural and industrial activities. NO 3 is one of the biggest contributors to groundwater pollution in the world.

Evaluation of arsenic pollution in groundwater
Arsenic is the 20th most abundant element found in the earth's crust, and its presence in the continental crust is at levels of 1-2 mg/kg (Taylor & McLennan ). type is As 5þ under oxidizing conditions and the dominant arsenic type is As 3þ under reducing conditions. The Eh-pH diagram for As species shows that H 3 AsO 4 2À arsenate species is dominant in groundwater samples (Figure 3).

Arsenic health risk assessment
The consumption of drinking water contaminated with arsenic plays an important role in increasing diseases related to arsenic exposure. Risk assessment is defined in two groups as carcinogenic risk and non-carcinogenic risk. Geographical differences, arsenic (As T ) concentrations within the drinking water, differences in water consumption and anthropometric features such as height and body weight are indicative of the variability of arsenic exposure. Therefore, exposure and carcinogenic effect are determined by taking into account the daily intake, concentration, water consumption rate, body weight and all variations in sex. In the study area, groundwater is used as drinking, irrigation and domestic water by local people through wells. Therefore, in this study, a health risk assessment (chronic and carcinogenic effects such as average daily dose (ADD), HQ noncancer and carcinogenic risk (Rc)) was made for arsenic exposure from Aksȩhir groundwaters through drinking water intake. In addition, health risk values were calculated separately for adults and children and are given in Table 2.
According to  drinking water guidelines, all groundwater in the study area exceeded limit values in terms of Fe T , As T and Pb T . According to Piper (), Ca-Mg-HCO 3 and Ca-HCO 3 were determined as the water facies in the study area. This shows that water-rock interaction is a powerful factor in the formation of the chemical composition of water samples. Bold entries indicate HQ value exceeds 1, indicating potential non-carcinogenic but harmful effects.
Clay units around the alluvium were found to be the main source of natural arsenic pollution in the area. However, the excessive application of pesticides and fertilizers appears to have greater contribution to arsenic pollution of underground water resources. A health risk assessment was carried out since groundwater is used for drinking purposes in the area. The results indicate that arsenic levels in groundwater constituted an unacceptable carcinogenic and non-carcinogenic health risk to both adults and children.
Consequently, groundwater in the study area, which includes Aksehir and surroundings, exceeds maximum acceptable limits for arsenic in drinking water.

DATA AVAILABILITY STATEMENT
Data cannot be made publicly available; readers should contact the corresponding author for details.