Preliminary Investigation of the Physico-Chemical Properties of a Geothermal Spring (Hot Spring) located at Jakrem, Meghalaya, India

· Articles
Authors

D.G. Marbaniang*, D.F. Diengdoh & C.L. Nongpiur
Department of Chemistry, Lady Keane College, Shillong-793001, Meghalaya, India
Corresponding author:D.G. Marbaniang; email:deswyn1@yahoo.com

Abstract

The Geothermal spring located at Jakrem village in East Khasi Hills District of Meghalaya, India was investigated for physico-chemical properties. These characteristic features play a significant role in classifying and assessing water quality. The objective of undertaking this study is to understand the physico-chemical properties of the spring water and the health risk it poses for human consumption. Sixteen parameters were chosen for investigation. The spring exhibit a temperature of 47°C. A pH of 12 was observed for the spring water making it alkaline in nature. The water was very soft with very low calcium and magnesium contents. The dominant cation was observed to be sodium with potassium being the sub dominant. The alkalinity was mainly due to dissolved carbonates and hydroxides. Fluoride concentration was found to be very high i.e., 7.2 ml-1.

Keywords Geothermal, Health, Hot Spring, Physico-chemical, Risk, Toxic.

Introduction

Springs are concentrated ground water flow issuing at the surface as current flowing water. In thermal spring, the water forced up from moderate or great depths by other forces than hydraulic pressure, they may geyser, volcanic and thermal springs.

Hot water issuing from the earth’s surface has been a subject of awe since the dawn of humankind. Ancient civilizations revered thermal springs because they were believed to have supernatural and healing powers. Archaeological evidence also shows that thermal springs were used as bathing facilities in the ancient cities thermal springs find numerous applications as in the field of geothermal energy production, industrial processing, agriculture, aquaculture, bottled water and the extraction of rare elements. Moreover, with the increasing popularity of spas and the growing importance attached to the ‘natural’ health industry, thermal springs are again becoming centers of balneology. (Olivier, Niekerk and Walt, 2008). In other part of the world thermal springs are also being used for industrial processing, agriculture, aquaculture, bottled water and the extraction of rare elements. A relatively recent development which is receiving considerable interest is the identification and use of thermophilic bacteria for possible industrial purposes. (Yibas et al., 2011)

The terrestrial and perennial hot spring located at Jakrem village in East Khasi Hills District of Meghalaya, India is the only hot spring that has been discovered in the entire state. There has been no recent volcanic activity in Meghalaya, and therefore all thermal springs are considered to be of meteoric origin and the heating of the water is due to deep circulation along mainly fault zones as is the case with hot springs in South Africa (Kent, 1969). The thermal springs are not confined to any specific type of geology. They are mainly located in the parts of the state receiving high rainfall and where deep crustal faulting occurs. The district in which Jakrem is located has the unique distinction of being the wettest place on earth with an average annual rainfall of about 12,270 mm.

Geological Set-up of the East Khasi Hills District

The Generalized geological succession of the area of East Khasi Hills District is given in Table 1

The district area falls mainly within the Shillong or Meghalaya Plateau which is constituted mainly of Precambrian rocks of gneissic composition in which granites, schists, amphibolits, calcsilicate rocks occur as inclusions of various dimensions. The gneisses form the Basement Complex for the overlying Shillong Group of rocks and is separated from the later by an unconformity indicated at places by the occurrence of a conglomerate bed. The presence of primary structures like current bedding, ripple marks etc. indicated that quartzites of the Shillong Group are of sedimentary derivative later metamorphosed to quartzites. These occur mostly as thick layers. The Khasi basic ultrabasic Intusives comprising basic intusive like epidiorite, metagabro, metadoleraite etc occur mostly as sills, dykes in the various sub-facies of Shillong Group. In the study area one such exposure noticed in the North-Western part of the district where it intruded the Basement Gneissic Complex.The rocks are generally dark green, medium to coarse graines and massive.In weathered outcrops, the basic rocks give a reddish brown colour. Grainite Plutons occur as isolated patches in the district and cover an area next to area covered by Basement Gneissic complex.The South Khasi Granites occur as intrusive body in the Basement Gneissic complex. Both Porphyritic and fine-grained pink granite form the South Khasi Granite. The Sylhet Traps are of the nature of plateau basalts exposed in a narrow E-W strip along the southern border of the area and their anticipated thickness is 550-680 m. The Sylhet traps comprise predominantly basalts, rhyolites and acid tuffs. The Cretaceous sediments exposed in the Meghalaya Plateau are classified as Khasi Group. The Mahadek Formation, the top unit of the Khasi Group, consisting of coarse arkosic sandstone, often gluconitic, are found exposed in the extreme southern part of the district. The Shella Formation of Jaintia Group consists of alteration of sandstone and limestone occurs in the south-central and south-western part of the district. The Quaternary fluvial sediments occur in the extreme northern part of the district bordering Assam. (GWIB, 2011)

Table 1: General Geological Succession

Geological

Group

Formation

Rock Type

Quaternary Undifferentiated fluvial sediments (occuring as valley fill deposits)
                                                                                                Unconformity
Mio Pliocene     Chengapara Coarse Sandstone, silstone, clay and marl
                                                                                                Unconformity
Palaeo – EoceneCretaceous Jaintia GroupKhasi Group Shella (600 m)Mahadek (150 m) Alteration of sandstone and limestoneArkosic sandstone (Often Gluconitic &Ureniferous)
                                                                                                Unconformity
Cretaceous Syllet Trap (600 m) Basalt, Rhyolite, acid tuff.
                                                                                                Unconformity
Neo- Proterozoic – Lower Palaeozoic Granite Plutons Porphyritic coarse granite, pegmatite, aplite/quartz vein etc.
Proterozoic (undiff)Palaeo- Mesoproterozoic Khasi Basic- Ultrabasic intrusivesShillong Group Upper DivisionLower Division Epidiorite, dolerite. Amphibolite and pyroxenite dykes and sillsMainly Quartzites intercalated with phyllites.Mainly sehist with Cale Silicate rocks, carbonaceous phyllite and thin quartzite layers
                                                                                           Unconformity (Shared conglomerate)
Archaean(?)- Proterozoic (Undiff) Gneissic Complex (Basement Complex) Mainly quartzfeldspathic gnesis with enclaves of granites, amphibolites, schists etc.

Hydrogeology

The district of East Khasi Hills is covered mainly by crystalline rocks with Tertiary sedimentary rocks. The secondary porosity in consolidated formation e.g. fractures; joints, etc developed due to major, minor tectonic movements, prolonged physicochemical weathering, form the conduits as well as reservoirs of ground water. The weathered mantle varies from 10 to 30 m bgl. Ground water occurs under water table condition in the top weathered quartzite and in semi-confined condition in the fractured and jointed rocks. At hydrogeologically feasible locations, well drilled down to the depth of about 80-150 m below ground level may yield a moderate discharge of 5-15 m3hr-1 in Archaean and Pre-Cambrian Group of rocks. Depth to water level is found to occur between 2 and 15 m bgl. The valley areas are found to be favourable for the construction of dug wells and bore wells in other steep areas. It should be borne in mind that the zones are not uniform in characteristics as the aquifer material, fracture density and distribution and hydrogeological characteristics vary widely over short distances. Consequently, their water yielding capabilities vary considerably. (GWIB, 2011)

Being a hot euthermal hot spring, analysis of water sample from this hot spring holds lot of potential. The Jakrem hot spring is located about 0.5 km on the right bank of the Umngi River (Figure 1).

Jakrem village (Longitude: 91.50695, Latitude: 25.39089) is about 60 kms from Shillong, the capital of Meghalaya. The location is being used as a tourist destination whereby, tourist both foreign and local would bathe themselves in the spring water as it is believed that the water has medicinal properties. In some instances, villagers and visitors alike would use the spring water even for drinking and cooking purposes.

Thermal springs are thus natural resources that, if developed optimally, could make a considerable contribution to the local and regional economy. However, care should be exercised when making decisions regarding the appropriate use of the springs. A number of studies have found that geothermal waters may contain toxic elements such as fluoride, arsenic and mercury, radioactive elements and pathogenic organisms such as the meningitis causing Naeglerias fowleri and Legionella pneumonia. [Olivier, Niekerk and Walt, 2008].

The physical and chemical parameters of groundwater play a significant role in classifying and assessing water quality. The hydro chemical study reveals quality of water that is suitable for irrigation, agriculture, drinking and industrial purposes.

The objective of undertaking this study is to understand the physico-chemical properties of the hot spring and to get a clearer picture of health risk aspect of the thermal spring water.

Experimental

Materials and Methods

Buffer tablets, analytical reagents, acids (E. Merck) were of ultrapure grade. All aqueous solutions and dilutions were prepared with double distilled water. All glassware was cleaned by soaking in dilute nitric acid and was rinsed with double distilled water.

The Jakrem hot spring has an orifice or eye therefore making sample collection very easy. The hot spring water was collected during the month of November, 2013 in pretreated polythene bottles and analyzed for the following parameters: Temperature, pH, conductivity, total dissolved solids, turbidity, chloride, fluoride, alkalinity, total hardness, nitrate, manganese, iron, calcium, magnesium, sodium and potassium were analyzed as per standard analytical procedures [APHA, 1992]. The method for analyzing the different parameters is depicted in Table I.

Table I: Analytical methods and equipment used in this study

Sl.No

Parameter

Method

Instruments/Equipment

1

Temperature

Manual method

Using Mercury Thermometer (0-100oC)

2

pH

Electrometric

pH Meter

3

Turbidity

Nephelometry

Nephelo Turbidity Meter

4

Conductivity

Electrometric

Conductivity Meter

5

TDS

Electrometric

Conductivity/TDS Meter

6

Alkalinity

Titration by H2SO4

-

7

Hardness

Titration by EDTA

-

8

Chloride

Titration by AgNO3

-

9

Nitrate

Phenol Di Sulphonic Acid Method

VIS Spectrophotometer

10

Fluoride

SPADNS

Fluoride Comparator

11

Sodium

Flame emission

Flame Photometer

12

Potassium

Flame emission

Flame Photometer

13

Calcium

Titration by EDTA

-

14

Magnesium

Titration by EDTA

-

15

Iron

1,10, Phenanthroline Method

VIS Spectrophometry

16

Manganese

Sodium Bismuthate Oxidation Method

[Marbaniang, 2012]

VIS Spectrophometry

Results and discussion

The concentration of the different parameters in the hot spring water is depicted in Table 2. Thermal springs are usually mineralized to a greater or lesser extent, depending on the characteristics of the geological formations associated with the circulating groundwater. The sampled hot spring water is colourless, odorless and very clear in appearance. The temperature of the spring was measure in the site itself with a mercury thermometer. The temperature of the thermal spring was found to be 47ºC. The pH of the spring water was observed to be around 12 rendering the water basic and depositional in nature. The pH of the spring water has also exceeded the prescribed limit of 6.5-8.5 for drinking water (WHO, 2004)

Turbidity was within the maximum recommended limits for domestic and drinking waters, which is 5 NTU. The conductivity was observed to be around 250 µScm-1 indicating moderated concentration of dissolved solids (225 mgl-1) and is well within the WHO prescribed limit of 1000 µScm-1. The alkalinity value of the water was observed to be mostly due to dissolved hydroxides (32 mg-1) and carbonates (64 mgl-1). Because of high pH and alkalinity values the water is not pure and hence cannot be use for drinking as well as for irrigation. The soft nature of the spring water can be seen from the non-detectable values of hardness, calcium and magnesium indicating the absence of carbonates in the immediate vicinity in contact with the ground water which is in accordance with the values observed for alkalinity.

The dominant cation is sodium (83.12 mgl-1) with potassium (0.4 mgl-1) being subdominant, followed by iron (<0.3 mgl-1). The spring was characterized by low chloride concentration (11.0 mgl-1). Nitrate, which is of great interest because of its nutrient value was low i.e., less than 10 mgl-1.

The analysis of fluoride levels yields a very interesting result. In different regions of the state of Meghalaya, India, surface waters as well as ground waters have been analyzed for fluoride concentration but its concentration was always found to be below the detection limit. However, in this study, the level of fluoride concentration detected was very high and it was observed to be around 7.2 mgl-1 which has exceeded the safety limit (1mgl-1) as prescribed by BIS and WHO for drinking water. This indicates the unique nature of rocks and fluoride carrying minerals. The high fluoride concentration observed is however as expected for calcium poor aquifers and where cation exchange of sodium for calcium occurs. [Abu Zeid and Khaled, 1998].

Table 2 Physico – chemical characteristics of the Jakrem hot spring water

Sl. No

Parameters

Concentration

1

Temperature

47oC

2

pH

12

3

Conductivity

250?Scm-1

4

Turbidity

1.2NTU

5

Alkalinity (Phenolphthalein)

64 mgl-1

6

Alkalinity (Methyl Orange)

96 mgl-1

7

Total Hardness

Below Detection Limit

8

Chloride

11 mgl-1

9

Calcium

Below Detection Limit

10

Magnesium

Below Detection Limit

11

Iron

<0.3

12

Total Dissolved Solids

225 mgl-1

13

Nitrate

2.12 mgl-1

14

Manganese

Below Detection Limit

15

Sodium

83.12 mgl-1

16

Potassium

0.4 mg-1

17

Fluoride

7.2 mgl-1

Fluoride may be an essential element for animals and humans. For humans, however, the essentiality has not been demonstrated unequivocally, and no data indicating the minimum nutritional requirement are available. Fluoride has beneficial effect on teeth at low concentrations of 1mgl-1 by preventing and reducing the risk of tooth decay. Concentrations lower than 0.5mgl-1 of fluoride however have shown to intensify the risk of tooth decay. Fluoride can also be quite detrimental at higher concentrations exceeding 1.5-2.0 mgl-1 of water. High concentrations of fluoride pose a risk of dental fluorises as well as skeletal fluorisis and osteoporosis. Skeletal fluorosis is a significant cause of morbidity in certain regions of the world. This of course depends on the level and period of exposure of fluoride by any given individual (WHO, 1996). To produce signs of acute fluoride intoxication, minimum oral doses of at least 1 mg of fluoride per kg of body weight were required (Janssen et al., 1988). Many epidemiological studies of possible adverse effects of the long-term ingestion of fluoride via drinking-water have been carried out. These studies clearly establish that fluoride primarily produces effects on skeletal tissues (bones and teeth). Low concentrations provide protection against dental caries, especially in children. The pre- and post-eruptive protective effects of fluoride (involving the incorporation of fluoride into the matrix of the tooth during its formation, the development of shallower tooth grooves, which are consequently less prone to decay, and surface contact with enamel) increase with concentration up to about 2 mg of fluoride per litre of drinking-water; the minimum concentration of fluoride in drinking-water required to produce it is approximately 0.5 mgl-1.(WHO, 1996). The concentration of chlorine was also examined and it was found to be 0.2 mgl-1 which is well within the safety limit for human consumption.

Conclusions

The data from the present study shows that, some of the parameters measured (i.e., pH =12; F>2.0) are not within the acceptable range for drinking or domestic water. The water was found to be very soft with respect to calcium and magnesium hardness. The alkaline nature of the water can be attributed to dissolved carbonate compounds in general and Na2CO3 in particular. The water can be classified as temporary hard carbonated water. The dominant cation was observed to be sodium with potassium as the sub dominant cation. At drinking water concentration between 0.9 – 1.2 mgl-1, fluoride may give rise to mild dental fluorosis. Value of 1.5 – 2.0 mgl-1 of fluoride in drinking water gives rise to higher chances of dental fluorosis, while values exceeding 2.0 mgl-1 may have very high chances of dental and skeletal fluorosis. Total fluoride intakes above 6.0 mg day-1 have been shown to increase the effect on the skeleton, while fluoride intakes above 14.0 mg day-1 pose serious threats of severe skeletal effects. (WHO, 1994). With respect to pH and the high concentration of fluoride, the spring can be deemed as toxic and consumption of the waters from the spring should be avoided.

Acknowledgement

The authors wish to extend their sincere gratitude to the Principal, Lady Keane College for her encouragement, and for Sponsorship, to the Head of the Chemistry Department for allowing the work to be carried out in the Departmental Laboratory and to the staff of the department for their active participation in this research work.

References

Abu-Zeid, K. M. 1998. Recent trends and developments: Reuse of waste water in agriculture, Environmental Management and Health Journal, 9(2&3), MCB Uniersity Press.

APHA, 1992. Standard methods for the examination of water and wastewater (18thedn.). American Public Health Association, Washington DC.

Ground Water Information Booklet (GWIB), East Khasi Hills District Meghalaya, 2011.

Janssen, P.J.C.M., Janus, J.A, Knaap, A.G.A.C. 1988. Integrated criteria document fluorides — effects. Bilthoven, National Institute of Public Health and Environmental Protection (Appendix to Report No.75847005).

Kent, L.E. 1969. The thermal waters in the Republic of South Africa. In: Proc. Of Symposium II on mineral and thermal waters of the world, B-overseas countries, Vol. 19, Report of the 23rdsession of the International Geological Conference, 1968, Academia, Prague, pp. 143-164.

Marbaniang, D.G. 2012 Spectrophotometric determination of Manganese in ground water in Shillong City using Bismuthate oxidation method. International Journal of Environmental Protection 2(5): 22-26.

Olivier, J., van Nieker, H.J. and van der Walt, I.J. 2008. Physical and chemical characteristics of thermal springs in the Waterberg area in Limpopo Province, South Africa, Water SA 34(2): 163-174.

WHO, 1994. Fluoride and Oral Health. Report of a WHO expert Committee on Oral Health Status and Fluoride Use. Geneva, World Health Organization (WHO Technical Report Series 84

WHO, 1996. Fluoride in Drinking-water, Background document for development of WHO. Guidelines for Drinking-water Quality WHO/SDE/WSH/03.04/96,

WHO, 2004. Guidelines for drinking water quality. World Health Organization. Geneva. Switzerland.

Yibas, B., Olivier, J., Tekere, M., Motlakeng, T. and Jonker, C.Z. Preliminary Health Risk Analysis of Thermal Springs in Limpopo Province, South Africa Based on Water Chemistry Proceedings, Kenya Geothermal Conference 2011 Kenyatta International Conference Centre, Nairobi, November 21-22, 2011.

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