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Background
The use of natural spa fountains as a swimmer has been a human interest for a long time, and many people utilize spa fountains for therapeutic, healing, and recreational activities every year or in some cases. Nowadays, one of the most important uses of water in any region area esthetic and recreational; accordingly, swimming is one of the recreational activities with a constructive effect on human physical and mental health(1). From a hygienic point of view, hot spring water, such as drinking water, should be physically, chemically, and ideally suited to the required standards to maintain the health and well-being of those who use them (2).
The physical and chemical factors in this study include temperature, pH, electrical conductivity (EC), alkalinity, and total hardness. High water temperatures have a great effect on providing the opportunity for algae and germs to grow and affect the removal of swimmers' skin lesions (3). High water temperatures can cause swimmers to fall asleep, which can lead to the loss of consciousness, heat, or mortality. In addition, it can cause discomfort and hyperthermia for users (4, 5). High or low pH values can have many effects. If the pH value is low, it can corrode water pipes, eliminate chlorine, stain, and irritate swimmers' eyes and skin (6).
The EC of water reflects the ions present in the water because the ions conduct the electric current. Negative ions move to the positive pole, and positive ions move to the negative pole. Since this ability is a function related to the presence of ions in a solution, the measurement of EC is a good indicator for all solutes in water. The EC of pure water is very low, and as the concentration of ions increases, its electrical conductivity increases (7).
The alkalinity of water is considered one of the general properties of water. The acidity and alkalinity of water both depend on the amount of water-soluble carbon dioxide. Water hardness is a quality that results from the excessive soluble salts of calcium and magnesium, and to some extent manganese, aluminum, and zinc, making water consumption difficult in general and in the industry in particular. When rainwater passes through soft rocks, some minerals dissolve in water, resulting in the hardness of water.
In a 2012 study carried out by Naresh et al. on the physiochemical properties of hot springs in the Indian Ocean region, the results were compared with the World Health Organization parameters, and the water was good and edible (8). In a study conducted by Ghilamicael on the Physical and Chemical Characteristics of Five Hot Springs in Eritrea, it was shown that the water from the five Eritrean hot springs is
not fit for human consumption (9). In a
study performed by Shito et al., titled Physicochemical and Biological Analysis of Water Used for Drinking and Swimming in Nigeria in 2007, the results showed that the findings of the physicochemical tests were in accordance with the standards (10).
In a study conducted in 2012 on the physical and chemical properties and risk of community health in Ethiopian hot springs, it was demonstrated that water does not have a favorable physicochemical quality and may cause disease (11). In addition, the physical and chemical quality analysis of water samples taken from Meshkin Shahr spa pools by Movassagh et al. showed that none of them met the standards (12). In a study carried out by Hosseinzadeh et al. in 2014 on the investigation of the physicochemical and microbial indices of public swimming pools in Boroujerd, Iran, it was observed that in all the studied pools, the health indices were in good levels. However, in some cases, physicochemical parameters were within the standard range. do not exist and require constant monitoring (13).
 
Aims of the study
The purpose of this study was to evaluate the physicochemical quality of natural active hot springs in South Khorasan, Iran, for the health and drinking and compare them with the standards in summer and autumn. South Khorasan has a number of hot springs whose physicochemical characteristics are not documented. The present study was carried out for 6 months in two stages in 2018. Field data and water samples were collected from eight hot springs, namely Ferdows, Lot, Dig-e Rostam, Tabas, Darmian, Sarbisheh, Qaen, and Abtorsh.
 
 

Materials & Methods

 
This experimental study was performed on
 

Table 1) Geographical coordinates of South Khorasan natural spa springs

Latitude	Longitude	Hot spring	Number
34.138788	85.213871	Ferdows	1
32.46909	58.319401	Lot	2
32.277444	57.515057	Dig-e Rostam	3
33.662718	57.1639	Tabas	4
32.89848	60.26137	Darmian	5
32.565161	59.985648	Sarbisheh	6
32.891218	59.699404	Qaen	7
32.772983	59.80489	Abtorsh	8

 

Figure 1) Analyzed samples in this study collected from eight hot springs in South Khorasan, Iran
 

eight natural active hot springs in South Khorasan in 2018. This study was approved by the Ethics Committee of Birjand University of Medical Sciences in Birjand, Iran, with the ethics code of 2018.126.IR.BUMS.REC. South Khorasan is one of the eastern provinces of Iran with numerous mineral springs that have multiple healing properties. The Active hot springs with their geographical coordinates, are listed and shown in Table 1 and Figure 1, respectively.
Given that most tourists visit the hot springs in summer and autumn, the analysis of the physicochemical quality of natural spa springs was conducted in one stage in summer and another in autumn. At each stage, four samples were obtained from the water intake at midday according to sampling conditions. In addition, temperature and pH parameters were measured using a pH meter (WTW, Germany) and an EC gauge portable (Knick model, Germany). To measure the total hardness and alkalinity of the specimens with the titration method, the specimens were transferred to Birjand University of Medical Sciences Laboratory under the standard conditions, and the measurements of each sample were repeated three times according to a standard method (14, 15). The total hardness and alkalinity of water were calculated by titration in the laboratory. Then, the results were analyzed using Excel software (version 2010).
 
Alkalinity Testing
Alkalinity is significant in many uses and treatments of natural waters and wastewaters. As the alkalinity of lots of surface water is composed of carbonates, bicarbonate, and hydroxide, it is also assumed to be an indicator of these constituents. Alkalinity in the excess
of alkaline earth metal concentrations is significant in the determination of the suitability of water for irrigation. Regarding the titration of the sample size and normality of titrant, 0.02N or 0.1N sulfuric (H₂SO₄) was used for the standard alkali of that method. Then, formula 1 was used to calculate alkalinity (15).
 
Formula 1: Alkalinity (mg/L CaCo₃) =
 
A: used mL standard acid
N: normality of standard acid
Ml: milligram sample
 
Total Hardness Testing
For the determination of total hardness,
the titration method with ethylenediamine tetraacetic acid (EDTA) solution was used as in formula 2.
 
Formula 2: Total hardness (mg/L CaCo₃)=
 
A: used mL EDTA
N: normality of EDTA
 
 

Results

 
The average results of physicochemical properties of water from the natural hot springs of South Khorasan, including temperature (°C), pH, EC (μs/cm), total hardness, and alkalinity (mg/LCaCO₃), are presented in Table 2. In all hot springs, water flows from one side to the other and does not rotate.
According to the results of this study regarding the temperature of natural hot springs in South Khorasan, Dig-e Rostam and Sarbisheh hot springs had the maximum and minimum temperatures measured as 54.3 and 17.1°C, respectively. In addition, the highest and lowest pH values of spa springs in South Khorasan were obtained for springs in Darmian and Lot. Based on the EC results of South Khorasan spa springs, Ferdows and Darmian spa springs had the highest and lowest EC values, respectively.
 
 

Discussion

 
In Iran and developing countries in recent years, the pollution of water resources has increased with increasing population growth and industrial activities. On the other hand, the need for better water quality has increased. Therefore, for the protection and sustainability of human and community health, the water available to the consumer should comply with national and international standards. There is no specific physicochemical standard for natural spa springs; consequently, the physical and chemical quality of these springs was compared to that reported for the swimming pools.
In the present study, according to Table 2 (1), Dig-e Rostam and Abtorsh hot springs had the maximum and minimum temperatures measured as 54.3 and 17.1°C, respectively. As the standard temperature for swimming pools is 29°C (16), the temperature of the hot springs in South Khorasan was not within the standard temperature range. Moreover, most hot springs had lower temperatures than the standard temperature, and the rest of the springs had temperatures higher than the standard range. It should be noted that the extremely high temperature at Dig-e Rostam springs has created problems for some users due to local evidence.  
In Canada, the optimum standard temperature for hot springs is proposed within the range of 38-36°C (17). In assessing the temperature of the swimming pools in Hamadan, Iran, only 40% of the samples were out of the standard range, and the rest were
 

Table 2) Mean values of water sample of South Khorasan hot springs in terms of temperature (°C), pH, electrical conductivity(μs/cm), total alkalinity (mg/LCaCO₃), and hardness(mg/LCaCO₃)

Hardness	Alkalinity	Electrical conductivity	pH	Temperature	Hot spring
1204±46	202±35	10.34±0.8	6.65±0.0	34±0.8	Ferdows
860±32	282±42	8.87±0.8	6.47±0.0	42±1.2	Lot
660±28	216±22	4.66±0.6	6.95±0.4	54.3±1.7	Dig-e Rostam
268±18	144±17	1.77±0.2	6.87±0.0	33.7±0.9	Tabas
192±12	165±20	1.23±0.2	7.79±0.2	32.5±0.6	Darmian
432±24	2199±55	6.92±0.5	6.87±0.0	33.5±0.4	Sarbisheh
140±10	166±12	1.43±0.1	7.87±0.2	35.8±0.7	Qaen
688±28	807±28	1.8±0.2	6.89±0.1	17.1±1.1	Abtorsh
200-300≥	150≥	No guideline	7.2-8	26-28	Swimming pool standard

 

within the standard range (18). In addition, in a study conducted in Jordan, most swimming pools were in poor condition, such as hot springs in South Khorasan, with higher temperatures than the standard conditions (19).
High pH values reduce chlorine efficiency so that at pH above 8, only 20% of chlorine is hypochlorous acid, which is an effective disinfectant.  High or low pH values can have many effects. A low pH value can cause the corrosion of water supply pipes and filtration systems, loss of chlorine, staining, and irritation of swimmers' skin in pools, and if pH value is high, it may cause particles to sediment on the floors and walls of swimming pools, water pipes, and sand filtration systems (20). In the present study, the pH values in Qaen and Lot hot springs were the highest, reported as 7.87 and 6.47, respectively, according to the pH standard of the swimming pools, documented as 7.2 to 8 (6).
Only the pH values ​​of Darmian and Qaen hot springs were within the standard range. In comparing the pH values ​​of South Khorasan hot springs with those of Ayob North (13), Kerman (16), Gorgan (21), Isfahan (22), and Shahrekord (23)hot springs, most of them were within the standard pH range. However, the pH value of hot springs in Nir, Iran, (17) similar to those in South Khorasan, was not within the standard range. According to Table 2, the highest and lowest EC values ​​of Ferdows spa were 10.34 and 1.23 μs/cm, respectively.
In terms of alkalinity, according to Table 2, the maximum and minimum alkalinity reported for Sarbisheh and Tabas hot water springs were 2199 and 144 (mg/L CaCO₃), respectively. The alkalinity of all hot water springs was within the standard range of 150 ≥ (12), except for Tabas hot spring. The effluent of most hot springs is used for agricultural and other purposes; nevertheless, the high alkalinity in the hot springs of Sarbisheh has caused water to run into the environment after leaving the pool, and no use can be made. Therefore, there were no bushes, plants, and vegetations around.
 On the other hand, local evidence and users suggest that healing wounds and joints, as well as rheumatic pain, were among the benefits of using the spa. As stated in the scientific literature, the high levels of alkali can cause problems, such as water turbidity, hard pH adjustment, and elevated pH. According to Table 2, in most cases, the level of alkalinity is higher than the standard level. In addition, in some cases, the total hardness is excessive, which can cause problems, such as sedimentation and cloudy state, in the pool water (16, 24).
With the consideration of the hardness, water can be divided into four categories, namely soft (less than 75 mg/L CaCO₃), medium (75-150 mg/L CaCO₃), hard (150-100mg/LCaCO₃), and very hard (higher than 300mg/L CaCO₃) (25). The incidence of kidney disease, hypertension, esophageal cancer, stomach, sudden deaths,
 

Table 3) Comparison of compliance percentage of each parameter measured according to the standards in South Khorasan spa springs with those of some springs and swimming pools

Khorramabad	Boroujerd	Urmia	Meshkin Shahr	South Khorasan	Standard rate	Parameter
%18	%54.16	%76.2	%0	%0	26-28	Temperature (°C)
%83	%100	%83.85	%0	%28	7.2-8	pH
%23	%12.5	%69.1	%0	%12.5	150≥	Alkalinity (mg/L CaCO3)
%3.3	%37.5	%72.91	%0	37.5%	200-300≥	Total hardness (mg/L CaCO3)