Hydrogeochemical assessment and evaluation of groundwater quality ...
J O U R N A L
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C O A S T A L
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JOURNAL OF COASTAL SCIENCES Journal homepage: www.jcsonline.co.nr
ISSN: 2348 – 6740
Volume 2 Issue No. 1 - 2015
Pages 1-5
Hydrogeochemical assessment and evaluation of groundwater quality from Ennore to Kasikovilkuppam, Thiruvallur District, Tamil Nadu, India * S.G.D. Sridhar, G. Kanagaraj, M. Mohamed Rafik, M. Balasubramanian Department of Applied Geology and Centre for Environmental Sciences, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai Centre forIndia Geotechnology, Manonmaniam Sundaranar University, Tirunelveli, Tamil Nadu 627 012, India 600 025,
ABSTRACT
Hydrogeochemical assessment and evaluation of groundwater quality from Ennore to Kasikovilkuppam, Thiruvallur district was carried out to assess the acquisition process and water quality for domestic, agricultural and industrial uses. From twenty seven locations, in the study area, 27 groundwater samples were collected during post monsoon (January 2014) and pre monsoon (June 2014) respectively from bore wells and open wells to assess groundwater quality. The samples were analyzed for pH, electrical conductivity, total dissolved solids (TDS), total hardness (TH), major anions (Cl-, NO3, HCO3, SO4) and cations (Ca2+, Mg2+, Na+, K+). The average values for TDS are being observed as 1476.78 mg/l and 2518.41 mg/l for post and pre-monsoon seasons, respectively. Based on Bureau of Indian Standard, it is observed that TDS exceeds the permissible limit during pre-monsoon season; the groundwater quality was found suitable for irrigation and not suitable for drinking purposes. It is inferred that during pre-monsoon season, TH and Ca exceed the permissible limits in most of the samples due to seawater intrusion, anthropogenic activity and impact of salt pan. *Corresponding author, E-mail address: [email protected] Phone: 044-22202724, © 2015 – Journal of Coastal Sciences. All rights reserved
1. Introduction ail.comof the mineral Groundwater chemistry is largely a function composition of the aquifer through which it flows. As groundwater moves along its path from recharge to discharge areas, a variety of hydrogeochemical processes alter its chemical composition. The quality required for groundwater supply depends on its purpose. The chemistry of groundwater often reflects the primary suit of minerals in an aquifer. The hydrogeochemical processes of the groundwater vary spatially and temporally, depending on the geology and chemical characteristics of the aquifer (Lakshmanan et al., 2003). The hydrogeochemistry helps in analyzing groundwater to know about its quality in terms of hardness, total dissolved salt contents. The composition of pure water in the form of H+ and OH- and carbonic acid has got an efficiency to dissolve the solids in the rock. Seawater intrusion is one of the most common problems in almost all coastal aquifers around the globe (Park et al., 2005; Batayneh, 2006; Sherif et al., 2006; Mondal et al., 2010). Sodium and chloride are other dominant ions of seawater, while calcium and bicarbonate are generally the major ions of freshwater (Hem, 1989).Precipitation can occur when the water becomes saturated with ions or molecules that contain the aquifer mineral. Intense competition among users such as agriculture, industry, and domestic sectors is driving the groundwater table lower. The present study aims to decipher the hydrogeochemical characteristics and quality along the coastal aquifers between Ennore to Kasikovilkuppam, Tamil Nadu, India.
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Received 1 November 2014 Accepted 06 March 2015 Available online 09 March 2015
Keywords Groundwater Geochemistry Box and Whisker plot USSL diagram Gibbs diagram Piper diagram
2. Study area and Geology The study area covers the northeast coast of Chennai region consisting of coastal groundwater at Ennore that comes under Thiruvallur district of Tamil Nadu. Ennore Creek is located in the northern part of Chennai City with an estimated population of 6.91 million, in the State of Tamil Nadu on the southeast coast of India. It covers an area of 60 sq. km that falls between 13°18'51.60"N and 13°10'1.5"N latitude and from 80°16'45.54"E to 80°18'33.9E" longitudes (Fig. 1). The study area is located on northeast coast of Chennai Metropolitan City. The main source of pollution input to Ennore Creek is through the discharge of waste water effluents, leachates, chemicals, paints, fertilizers and petroleum refining industries that are located in the northern part of the city limits. Ennore coast consists of alluvial tracts, beach dunes, tidal flats and creek in the eastern part. The geology of Chennai comprises mostly clay, shale and sandstone. The city is classified into three regions based on geology, namely, sandy areas, clayey areas and hard-rock areas. Sandy areas are found along the river banks and the coasts. The total area of the creek is 2.25 sq. km and is nearly 400 m wide. Araniar and Korataliyar are the two seasonal rivers that traverse Ennore creek. Ennore comprises of lagoon and salt marshes and back waters. Clay underlies most of the city, namely, Manali, Kolathur, Maduravoyal, K.K. Nagar. Sandy areas are found along the river ORIGINAL
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banks and coasts. The region has the oldest rocks in the country salinity, groundwater generally exhibits high concentrations not only dating back to nearly a billion years. in total dissolved solids (TDS) but also in major cations and anions (Richter and Kreitler, 1993).With respect to cations, calcium and magnesium were analyzed by volumetric method. Sodium and 3. Methodology potassium were analyzed by Flame photometer. With respect to From twenty seven locations, groundwater samples were collected anions, chloride and bicarbonate were done by volumetric method; during the post monsoon (January, 2014) and pre monsoon season nitrate and sulphate were estimated by turbidity method. Standard (June, 2014) from bore wells and open wells to assess groundwater procedures were followed for the analysis of chemical constituents quality in the study area. The water samples are numbered starting (APHA, 1998). The EC and pH were measured in the field. The from 1 to 27 from Vayalorkuppam to Kasikovilkuppam. The groundwater samples were analyzed in the geochemical laboratory following villages are lying in the study area: they are, to find out anions and cations. Pre cleaned polyethylene bottles Vayalorkuppam, Ramanathapuram, Senganimedu, Kokumedu, (Laxen and Harrison, 1998) were used for collecting water samples Vayalur, Neythavayalminjur, Ariyanvayal, Puthupedu, from open wells and bore wells. Groundwater samples were Reddypalayam, Mauthumpedu, Nandayampakkam, Attipatu, collected using the simple random sampling method. Rettipalayam, Koundampalayam, Kondakarai, Nappalayam, Edayanchavadi, Ulaganathapuram, Ennore river mouth, 4. Results and Discussion Sathyavanimuthu Nagar, Thalankullm, Periyakuppam, Chinnakupam, Kasikovilkuppam. The samples were analyzed to establish criteria Hydrochemistry of the study area shows that the maximum and such as physical and chemical characteristics of groundwater. The minimum concentration of major cations and anions of groundwater physical characteristics are color, turbidity, taste, and odour as shown in Table 1. Groundwater in the study area is generally have whereas, chemical characteristics comprise major cations and anions pH ranging from 6.2 to 7.9 during post-monsoon season, while in the like, Na, K, Ca, Mg, SO4, NO3, HCO3 including the measurement of pH pre-monsoon it ranges from 6.43 to 7.23. They are within the and EC. pH were measured using portable pH meter, EC were permissible limit in both the seasons based on BIS (2012). EC is one measured using electrode in the field, then TDS were estimated by of the measurement of strength and mineralization of natural water. calculation method. When seawater intrusion is a main cause of high In the study area, EC ranges from 802 to 5900µS/cm during post-
Fig. 1 Geomorphology of study area with location of groundwater samples
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monsoon, while in the pre-monsoon it ranges from 1030 to 16100 µS/cm. TDS range from 561 to 4130 mg/l during post-monsoon season, whereas, during pre-monsoon it ranges from 721 to 11270 mg/l. According to BIS (2012) TDS is above permissible limit in both the seasons. TDS increases after rains that dissolve minerals from overlying rocks (minerals) during infiltration. Parameter
pH ECµS/cm
Post monsoon
Pre monsoon
Min
Max
Min
Max
802
5900
1030
16100
6.82
7.90
6.43
7.23
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mg/l while it ranges between 40 and 1760 mg/l during pre-monsoon samples. Magnesium ion concentration in the post-monsoon season varies from 12 to 110 mg/l while it ranges between 13 and 384 mg/l during pre-monsoon samples. Potassium ion concentration in the post-monsoon season varies from 4 to 55 mg/l whereas; it ranges between 7 and 66 mg/l during pre-monsoon samples. Comparing the BIS (2012), Na, Ca, Mg and K concentrations were above permissible limit in most of the samples. The BIS standards for anions and cations are presented in Table 2. 4.2. Major Anions
The ascendancy of anions is as follows Cl> HCO 3> SO4> NO3 during post and pre-monsoon seasons. Chloride ion concentration in the TDS mg/l 561 4130 721 11270 post-monsoon season varies from 120 to 1275 mg/l while it ranges Ca mg/l 56 400 40 1760 between 180 and 4750 mg/l during pre-monsoon samples. Cl- is Mg mg/l 12 110 13 384 higher due to the impact of saline water and base–ion exchange reaction (Freeze and Cherry, 1979). Bicarbonate ion concentration in Na mg/l 74 1020 94 1124 the post-monsoon season varies from 92 to 688 mg/l while it ranges K mg/l 4 55 7 66 between 144 and 540 mg/l during pre-monsoon samples. Higher Cl mg/l 120 1275 180 4750 concentration of bicarbonate indicates the contribution of silicate HCO3 mg/l 92 688 144 540 and carbonate for chemical weathering. Sulphate ion concentration in the post-monsoon season varies from 9 to 186 mg/l while it SO4 mg/l 9 186 19 159 ranges between 19 and 159 mg/l during pre-monsoon samples. NO3 mg/l 1 44 9 45 Nitrate ion concentration in the post-monsoon season varies from 1 Table 1. Maximum and minimum concentration of major cations and anions to 44 mg/l whereas; it ranges between 9 and 45 mg/l during preof groundwater samples during Pre and Post monsoon seasons monsoon samples. Based on the BIS (2012), Cl, HCO3 are above permissible limit in most of the samples, but SO4 and NO3 are within BIS 10500 : 2012 (Bureau of Indian Standards) permissible limit. It indicates that most of the samples are not suitable for drinking purpose as well as agriculture uses. S. Characteristics Requirement Permissible No. (Acceptable Limit 4.3. Box-and-Whisker Plot Limit) 1 pH value 6.5-8.5 No relaxation Box plots can be used to compare the groundwater quality data 2 Total dissolved solids 500 2 000 (generally for the same parameter) between wells. The plots are mg/l constructed using the median value and the interquartile range (25 3 Total alkalinity mg/l 200 600 and 75 cumulative frequencies as measured central tendency and (HCO3) variability).They is a quick and convenient way to visualize the 4 Sodium mg/l (Na) 200 spread of data. Complicated evaluations may dictate use of a series of box plots. The chemical composition of the groundwater samples is 5 Calcium mg/l (Ca) 75 200 shown in Figure 2 as box plot. The abundance of the major cations is 6 Magnesium mg/l (Mg) 30 100 in the order of Na>Ca>Mg in post monsoon and Mg>Ca>Na in pre 7 Potassium mg/l (K) 42 monsoon. The abundance of major anions is in the order of Cl > HCO3>SO4 during both seasons. 8 Chloride mg/l (Cl) 250 1000 9 10
Sulphate mg/l (SO4) Nitrate mg/l (NO3)
200 45
400 No relaxation
Table 2. Water quality according to BIS 10500: 2012 (Bureau of Indian Standards)
4.1. Major Cations
The ascendancy of cations is as follows Na > Ca > Mg > K during post and pre-monsoon seasons. Sodium ion concentration in the postmonsoon season varies from 74 to 1020 mg/l while it ranges between 94 and 1124 mg/l during pre-monsoon. Near the coast, the samples show higher concentrations of Na followed by Ca (Chidambaram et al., 2005). Sodium concentration plays an important role in evaluating the groundwater quality for irrigation because sodium causes an increase in the hardness of soil as well as a reduction in its permeability (Tijani, 1994). Calcium ion Fig. 2 Box and Whisker diagram for the groundwater samples (Post and Premonsoon) concentration in the post-monsoon season varies from 56 to 400 3
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4.4. USSL Diagram
4.6. Hydrochemical Facies (Piper Diagram)
This diagram is used for interpreting the analysis of irrigation water. Water can be grouped into 16 classes. It uses SAR (vertical axis) and conductance (horizontal axis). The USSL diagram for the study area is show in Figure 3. All concentration values are expressed in equivalents per million. Sodium absorption ratio is also used to determine the suitability of groundwater for irrigation as it gives a measure of alkali/sodium hazard to crops. If calcium and magnesium are dominant, the hazard is low. In the USSL diagram (USSL, 1954), S1, S2, S3, S4 types indicate sodium hazards and C1, C2, C3, C4 types indicate the salinity hazards. Based on this classification, the majority of the samples of the study area belongs to C3S1 (high salinity, low sodium) and C4S1 (very high salinity, low sodium) during post and pre monsoon seasons, respectively.
The concentrations of major ionic constituents of groundwater samples were plotted in the Piper diagram (Piper, 1994) to determine the water types. The classification for the cation and anion facies, in terms of major ion percentages and water types, is according to the domain in which they occur in the diagram segments as in Table 3. Sub division of the diamond
Characteristics of corresponding subdivisions of diamond shaped fields
1
Alkaline earth (Ca+Mg) Exceed alkalies (Na+K) Alkalies exceeds alkaline earths Weak acids (CO3+HCO3) Exceed Strong acids (SO4+Cl) Strong acids exceeds weak acids Magnesium bicarbonate type Calcium-chloride type Sodium-chloride type Sodium-Bicarbonate type Mixed type (No cationanion exceed50%)
2 3 4 5
Fig. 3 USSL diagram for the groundwater samples (Post and Pre-monsoon)
4.5. Gibbs Diagram
The chemical relationships of groundwater based on aquifer lithology have been studied following Gibbs, (1970). Three kinds of fields are recognized in the Gibb’s diagram, namely, precipitation dominant, evaporation-crystallization dominant and rock-water interaction dominant (Gi-Tak Chae et al., 2006). Gibbs plots for postmonsoon and pre monsoon is shown in Figure 4. According to the Gibbs diagram, for the study area, the evaporation and rock–water interaction dominate the water chemistry in both seasons of the groundwater for they fall under its influence for both the Gibb’s ratios I-Na+K/ (Na+K+Ca) representing the cations and II- Cl/ (Cl+HCO3) representing the anions. Most of the samples fall in evaporation field due to salt water intrusion.
6 7 8 9
% of samples in this category for PostMonsoon 44.4
% of samples in this category for PreMonsoon 88.8
00.0
03.7
55.5
11.1
100.0
96.3
3.7 55.5 00.0
44.4 07.4 00.0
0.0
40.7
Table 3. Classification of water according to their types
0.0
48.1
To define a composition class, Back and Co-workers suggested subdivisions of the tri-linear diagram. The cations and anion fields are combined to show a single point in a diamond-shaped field, from which inference is drawn on the basis of hydrogeochemical facies concept. It clearly explains the variations or domination of cation and anion concentrations during pre and post-monsoon as shown in Figure 5.
Fig. 4 Gibbs diagram for the groundwater samples (Post and Pre-monsoon)
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Fig. 5 Piper diagram for the groundwater samples (Post and Pre-monsoon) ORIGINAL
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Alkaline earths exceeds alkalies (44.4%) and (88.8%) and the type strong acids exceeds weak acids (100.0%) and (96.30%) during Postmonsoon and Pre-monsoon, respectively. Rapid urbanization and industrialization make an impact on groundwater quality of the study area. The reason is groundwater passing through igneous rocks dissolves only small quantities of mineral matters because of the relative insolubility of the rock composition. While the high concentration of sulfates may be attributed to the contamination by the untreated industrial and domestic waste effluents (Baruah et al., 2008).
5. Conclusion
Based on the BIS (2012), the cations Na, Ca, Mg and K concentrations were above permissible limit and anions Cl, HCO 3 are above permissible limit in most of the samples, but SO4 and NO3 are within permissible limit which indicates that most of the samples are not suitable for drinking purpose as well as agriculture uses. Box and Whisker plot shows the abundance of the major cations in the order of Na > Ca > Mg in post monsoon and Mg > Ca > Na in pre monsoon. The abundance of major anions is in the order of Cl > HCO 3 > SO4 during both seasons. USSL diagram represents the majority of the samples belongs to C3S1 (high salinity, low sodium) and C4S1 (very high salinity, low sodium) during post and pre monsoon seasons respectively, and the samples are not suitable for drinking purpose due to salt water intrusion. Gibbs plot illustrates that during both the seasons, evaporation increases the salinity and the higher concentration of Na and Cl ions increases the TDS. According to Piper diagram, alkaline earths exceeds alkalies (44.4%) and (88.8%) and the strong acids exceeds weak acids (100.0%) and (96.3%) during Post-monsoon and Pre-monsoon, respectively due to rapid urbanization and industrialization.
Acknowledgement
First author thank the UGC for the financial support extended to this research in the form of UGC-SAP-DRS II. The authors are grateful to University of Madras and thankful to Prof. K.K. Sharma, Head, Department of Applied Geology for the support and infrastructure provided for this study. With gratitude the authors are grateful to Tamil Nadu Water Supply and Drainage Board (TWAD Board) for providing the facility of analyzing the groundwater samples in their laboratory.
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Gibbs, R. J., 1970. Mechanisms controlling world water chemistry, Science, Vol.170, pp 795– 840. Gi-TakChae., Seong-TaekYun., Kangjoo Kim., Bernhard Mayer., 2006. Hydrogeochemistry of sodium-bicarbonate type bedrock groundwater in the Pocheon spa area, South Korea: water–rock interaction and hydrologic mixing. Journal of Hydrology, 321, 326–343. Hem, J. D., 1989. Study and interpretation of the chemical characteristics of natural water.U.S.G.S. Water-supply paper Vol. 2254. Washington DC: US Government Printing Office. Laksmanan, E., Kannan, R., Senthil Kumar, M., 2003. Major ion chemistry and identification of hydrogeochemical process of groundwater in a part of Kancheepuram district, Tamilnadu, India, J. Environ. Geosci, 10(4), 157166. Laxen, D. P. H., Harrison, R. M., 1998. Cleaning methods for polythene containers prior to the determination of trace metals in freshwater samples. Anal. Chem. 53, 345-350. Mondal, N. C., Singh, V. P., Singh, V. S., Saxena, V. K., 2010. Determining the interaction between groundwater and saline water through groundwater major ions chemistry. Journal of Hydrology, 388(1–2), 100–111. Park, S. C., Yun, S. T., Chae, G. T., Yoo, I. S., Shin, K. S., Heo, C. H., 2005. Regional hydrochemical study on salinization of coastal aquifers, western coastal area of South Korea. Journal of Hydrology, 313, 182–194. Piper, A. M., 1994. A geographic procedure in the geochemical interpretation of water analysis, Transactions—American Geophysical Union. 25, 914– 928. Richter, B. C.,Kreitler, C.W.,1993. Geochemical techniques for identifying sources of ground-water salinization, CRC Press, pp 258. Sherif, M., Mahmoudi, E. A., Garamoon, H., Kacimov, A., Akram, S., Ebraheem, A., 2006. Geoeletrical and hydrogeochemical studies for delineating seawater intrusion in the outlet of Wadi Ham, UAE. Environmental Geology, 49, 536 551. Tijani M.N., 1994. Hydrochemical assessment of groundwater in Moro area, Kwara State, Nigeria. Environ Geol, 24, 194–202. Todd, D.K., 1980. Groundwater hydrogeology, 2nd edn. Wiley, New York. pp 552. USSL, 1954. Diagnosis and improvement of saline and alkali soils, US Department of Agricultural soils. US Department of Agricultural Hand Book 60, Washington DC.
References
APHA, 1998. Standard methods for the examination of water and wastewater, American Public Health Association, Washington. Baruah, M., Bhattacharyya, K. G., and Patgiri, A. D., 2008. Water quality of shallow groundwater of core city area of Guwahati, In Proceedings of sixteenth national symposium on environment, Haryana, India. pp 101– 106. Batayneh, A. T., 2006. Use of electrical resistivity methods for detecting subsurface fresh and saline water and delineating their interfacial configuration: A case study of the eastern Dead Sea coastal aquifers, Jordan, Jl. Hydrogeology, 14, 1277–1283. BIS, 2012. Specifications for drinking water, New Delhi: Bureau of Indian Standards (BIS). Chidambaram, S., Ramanathan, AL., Ananadhan, P., Srinivasamoorthy, K., Vasudevan, S., Prasanna, M. V. 2005. A study of the coastal groundwaters from Puduchattiram to Coleroon Tamilnadu, India, International Journal of Ecology and Environmental Sciences, 31(3), 299–306. Freeze, A. R., Cherry, J. A., 1979. Groundwater. Prentice-Hall, Inc, Englewood cliffs New Jersey, pp 604.
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JOURNAL OF COASTAL SCIENCES Journal homepage: www.jcsonline.co.nr
ISSN: 2348 – 6740
Volume 2 Issue No. 1 - 2015
Pages 1-5
Hydrogeochemical assessment and evaluation of groundwater quality from Ennore to Kasikovilkuppam, Thiruvallur District, Tamil Nadu, India * S.G.D. Sridhar, G. Kanagaraj, M. Mohamed Rafik, M. Balasubramanian Department of Applied Geology and Centre for Environmental Sciences, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai Centre forIndia Geotechnology, Manonmaniam Sundaranar University, Tirunelveli, Tamil Nadu 627 012, India 600 025,
ABSTRACT
Hydrogeochemical assessment and evaluation of groundwater quality from Ennore to Kasikovilkuppam, Thiruvallur district was carried out to assess the acquisition process and water quality for domestic, agricultural and industrial uses. From twenty seven locations, in the study area, 27 groundwater samples were collected during post monsoon (January 2014) and pre monsoon (June 2014) respectively from bore wells and open wells to assess groundwater quality. The samples were analyzed for pH, electrical conductivity, total dissolved solids (TDS), total hardness (TH), major anions (Cl-, NO3, HCO3, SO4) and cations (Ca2+, Mg2+, Na+, K+). The average values for TDS are being observed as 1476.78 mg/l and 2518.41 mg/l for post and pre-monsoon seasons, respectively. Based on Bureau of Indian Standard, it is observed that TDS exceeds the permissible limit during pre-monsoon season; the groundwater quality was found suitable for irrigation and not suitable for drinking purposes. It is inferred that during pre-monsoon season, TH and Ca exceed the permissible limits in most of the samples due to seawater intrusion, anthropogenic activity and impact of salt pan. *Corresponding author, E-mail address: [email protected] Phone: 044-22202724, © 2015 – Journal of Coastal Sciences. All rights reserved
1. Introduction ail.comof the mineral Groundwater chemistry is largely a function composition of the aquifer through which it flows. As groundwater moves along its path from recharge to discharge areas, a variety of hydrogeochemical processes alter its chemical composition. The quality required for groundwater supply depends on its purpose. The chemistry of groundwater often reflects the primary suit of minerals in an aquifer. The hydrogeochemical processes of the groundwater vary spatially and temporally, depending on the geology and chemical characteristics of the aquifer (Lakshmanan et al., 2003). The hydrogeochemistry helps in analyzing groundwater to know about its quality in terms of hardness, total dissolved salt contents. The composition of pure water in the form of H+ and OH- and carbonic acid has got an efficiency to dissolve the solids in the rock. Seawater intrusion is one of the most common problems in almost all coastal aquifers around the globe (Park et al., 2005; Batayneh, 2006; Sherif et al., 2006; Mondal et al., 2010). Sodium and chloride are other dominant ions of seawater, while calcium and bicarbonate are generally the major ions of freshwater (Hem, 1989).Precipitation can occur when the water becomes saturated with ions or molecules that contain the aquifer mineral. Intense competition among users such as agriculture, industry, and domestic sectors is driving the groundwater table lower. The present study aims to decipher the hydrogeochemical characteristics and quality along the coastal aquifers between Ennore to Kasikovilkuppam, Tamil Nadu, India.
1
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Received 1 November 2014 Accepted 06 March 2015 Available online 09 March 2015
Keywords Groundwater Geochemistry Box and Whisker plot USSL diagram Gibbs diagram Piper diagram
2. Study area and Geology The study area covers the northeast coast of Chennai region consisting of coastal groundwater at Ennore that comes under Thiruvallur district of Tamil Nadu. Ennore Creek is located in the northern part of Chennai City with an estimated population of 6.91 million, in the State of Tamil Nadu on the southeast coast of India. It covers an area of 60 sq. km that falls between 13°18'51.60"N and 13°10'1.5"N latitude and from 80°16'45.54"E to 80°18'33.9E" longitudes (Fig. 1). The study area is located on northeast coast of Chennai Metropolitan City. The main source of pollution input to Ennore Creek is through the discharge of waste water effluents, leachates, chemicals, paints, fertilizers and petroleum refining industries that are located in the northern part of the city limits. Ennore coast consists of alluvial tracts, beach dunes, tidal flats and creek in the eastern part. The geology of Chennai comprises mostly clay, shale and sandstone. The city is classified into three regions based on geology, namely, sandy areas, clayey areas and hard-rock areas. Sandy areas are found along the river banks and the coasts. The total area of the creek is 2.25 sq. km and is nearly 400 m wide. Araniar and Korataliyar are the two seasonal rivers that traverse Ennore creek. Ennore comprises of lagoon and salt marshes and back waters. Clay underlies most of the city, namely, Manali, Kolathur, Maduravoyal, K.K. Nagar. Sandy areas are found along the river ORIGINAL
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banks and coasts. The region has the oldest rocks in the country salinity, groundwater generally exhibits high concentrations not only dating back to nearly a billion years. in total dissolved solids (TDS) but also in major cations and anions (Richter and Kreitler, 1993).With respect to cations, calcium and magnesium were analyzed by volumetric method. Sodium and 3. Methodology potassium were analyzed by Flame photometer. With respect to From twenty seven locations, groundwater samples were collected anions, chloride and bicarbonate were done by volumetric method; during the post monsoon (January, 2014) and pre monsoon season nitrate and sulphate were estimated by turbidity method. Standard (June, 2014) from bore wells and open wells to assess groundwater procedures were followed for the analysis of chemical constituents quality in the study area. The water samples are numbered starting (APHA, 1998). The EC and pH were measured in the field. The from 1 to 27 from Vayalorkuppam to Kasikovilkuppam. The groundwater samples were analyzed in the geochemical laboratory following villages are lying in the study area: they are, to find out anions and cations. Pre cleaned polyethylene bottles Vayalorkuppam, Ramanathapuram, Senganimedu, Kokumedu, (Laxen and Harrison, 1998) were used for collecting water samples Vayalur, Neythavayalminjur, Ariyanvayal, Puthupedu, from open wells and bore wells. Groundwater samples were Reddypalayam, Mauthumpedu, Nandayampakkam, Attipatu, collected using the simple random sampling method. Rettipalayam, Koundampalayam, Kondakarai, Nappalayam, Edayanchavadi, Ulaganathapuram, Ennore river mouth, 4. Results and Discussion Sathyavanimuthu Nagar, Thalankullm, Periyakuppam, Chinnakupam, Kasikovilkuppam. The samples were analyzed to establish criteria Hydrochemistry of the study area shows that the maximum and such as physical and chemical characteristics of groundwater. The minimum concentration of major cations and anions of groundwater physical characteristics are color, turbidity, taste, and odour as shown in Table 1. Groundwater in the study area is generally have whereas, chemical characteristics comprise major cations and anions pH ranging from 6.2 to 7.9 during post-monsoon season, while in the like, Na, K, Ca, Mg, SO4, NO3, HCO3 including the measurement of pH pre-monsoon it ranges from 6.43 to 7.23. They are within the and EC. pH were measured using portable pH meter, EC were permissible limit in both the seasons based on BIS (2012). EC is one measured using electrode in the field, then TDS were estimated by of the measurement of strength and mineralization of natural water. calculation method. When seawater intrusion is a main cause of high In the study area, EC ranges from 802 to 5900µS/cm during post-
Fig. 1 Geomorphology of study area with location of groundwater samples
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monsoon, while in the pre-monsoon it ranges from 1030 to 16100 µS/cm. TDS range from 561 to 4130 mg/l during post-monsoon season, whereas, during pre-monsoon it ranges from 721 to 11270 mg/l. According to BIS (2012) TDS is above permissible limit in both the seasons. TDS increases after rains that dissolve minerals from overlying rocks (minerals) during infiltration. Parameter
pH ECµS/cm
Post monsoon
Pre monsoon
Min
Max
Min
Max
802
5900
1030
16100
6.82
7.90
6.43
7.23
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mg/l while it ranges between 40 and 1760 mg/l during pre-monsoon samples. Magnesium ion concentration in the post-monsoon season varies from 12 to 110 mg/l while it ranges between 13 and 384 mg/l during pre-monsoon samples. Potassium ion concentration in the post-monsoon season varies from 4 to 55 mg/l whereas; it ranges between 7 and 66 mg/l during pre-monsoon samples. Comparing the BIS (2012), Na, Ca, Mg and K concentrations were above permissible limit in most of the samples. The BIS standards for anions and cations are presented in Table 2. 4.2. Major Anions
The ascendancy of anions is as follows Cl> HCO 3> SO4> NO3 during post and pre-monsoon seasons. Chloride ion concentration in the TDS mg/l 561 4130 721 11270 post-monsoon season varies from 120 to 1275 mg/l while it ranges Ca mg/l 56 400 40 1760 between 180 and 4750 mg/l during pre-monsoon samples. Cl- is Mg mg/l 12 110 13 384 higher due to the impact of saline water and base–ion exchange reaction (Freeze and Cherry, 1979). Bicarbonate ion concentration in Na mg/l 74 1020 94 1124 the post-monsoon season varies from 92 to 688 mg/l while it ranges K mg/l 4 55 7 66 between 144 and 540 mg/l during pre-monsoon samples. Higher Cl mg/l 120 1275 180 4750 concentration of bicarbonate indicates the contribution of silicate HCO3 mg/l 92 688 144 540 and carbonate for chemical weathering. Sulphate ion concentration in the post-monsoon season varies from 9 to 186 mg/l while it SO4 mg/l 9 186 19 159 ranges between 19 and 159 mg/l during pre-monsoon samples. NO3 mg/l 1 44 9 45 Nitrate ion concentration in the post-monsoon season varies from 1 Table 1. Maximum and minimum concentration of major cations and anions to 44 mg/l whereas; it ranges between 9 and 45 mg/l during preof groundwater samples during Pre and Post monsoon seasons monsoon samples. Based on the BIS (2012), Cl, HCO3 are above permissible limit in most of the samples, but SO4 and NO3 are within BIS 10500 : 2012 (Bureau of Indian Standards) permissible limit. It indicates that most of the samples are not suitable for drinking purpose as well as agriculture uses. S. Characteristics Requirement Permissible No. (Acceptable Limit 4.3. Box-and-Whisker Plot Limit) 1 pH value 6.5-8.5 No relaxation Box plots can be used to compare the groundwater quality data 2 Total dissolved solids 500 2 000 (generally for the same parameter) between wells. The plots are mg/l constructed using the median value and the interquartile range (25 3 Total alkalinity mg/l 200 600 and 75 cumulative frequencies as measured central tendency and (HCO3) variability).They is a quick and convenient way to visualize the 4 Sodium mg/l (Na) 200 spread of data. Complicated evaluations may dictate use of a series of box plots. The chemical composition of the groundwater samples is 5 Calcium mg/l (Ca) 75 200 shown in Figure 2 as box plot. The abundance of the major cations is 6 Magnesium mg/l (Mg) 30 100 in the order of Na>Ca>Mg in post monsoon and Mg>Ca>Na in pre 7 Potassium mg/l (K) 42 monsoon. The abundance of major anions is in the order of Cl > HCO3>SO4 during both seasons. 8 Chloride mg/l (Cl) 250 1000 9 10
Sulphate mg/l (SO4) Nitrate mg/l (NO3)
200 45
400 No relaxation
Table 2. Water quality according to BIS 10500: 2012 (Bureau of Indian Standards)
4.1. Major Cations
The ascendancy of cations is as follows Na > Ca > Mg > K during post and pre-monsoon seasons. Sodium ion concentration in the postmonsoon season varies from 74 to 1020 mg/l while it ranges between 94 and 1124 mg/l during pre-monsoon. Near the coast, the samples show higher concentrations of Na followed by Ca (Chidambaram et al., 2005). Sodium concentration plays an important role in evaluating the groundwater quality for irrigation because sodium causes an increase in the hardness of soil as well as a reduction in its permeability (Tijani, 1994). Calcium ion Fig. 2 Box and Whisker diagram for the groundwater samples (Post and Premonsoon) concentration in the post-monsoon season varies from 56 to 400 3
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4.4. USSL Diagram
4.6. Hydrochemical Facies (Piper Diagram)
This diagram is used for interpreting the analysis of irrigation water. Water can be grouped into 16 classes. It uses SAR (vertical axis) and conductance (horizontal axis). The USSL diagram for the study area is show in Figure 3. All concentration values are expressed in equivalents per million. Sodium absorption ratio is also used to determine the suitability of groundwater for irrigation as it gives a measure of alkali/sodium hazard to crops. If calcium and magnesium are dominant, the hazard is low. In the USSL diagram (USSL, 1954), S1, S2, S3, S4 types indicate sodium hazards and C1, C2, C3, C4 types indicate the salinity hazards. Based on this classification, the majority of the samples of the study area belongs to C3S1 (high salinity, low sodium) and C4S1 (very high salinity, low sodium) during post and pre monsoon seasons, respectively.
The concentrations of major ionic constituents of groundwater samples were plotted in the Piper diagram (Piper, 1994) to determine the water types. The classification for the cation and anion facies, in terms of major ion percentages and water types, is according to the domain in which they occur in the diagram segments as in Table 3. Sub division of the diamond
Characteristics of corresponding subdivisions of diamond shaped fields
1
Alkaline earth (Ca+Mg) Exceed alkalies (Na+K) Alkalies exceeds alkaline earths Weak acids (CO3+HCO3) Exceed Strong acids (SO4+Cl) Strong acids exceeds weak acids Magnesium bicarbonate type Calcium-chloride type Sodium-chloride type Sodium-Bicarbonate type Mixed type (No cationanion exceed50%)
2 3 4 5
Fig. 3 USSL diagram for the groundwater samples (Post and Pre-monsoon)
4.5. Gibbs Diagram
The chemical relationships of groundwater based on aquifer lithology have been studied following Gibbs, (1970). Three kinds of fields are recognized in the Gibb’s diagram, namely, precipitation dominant, evaporation-crystallization dominant and rock-water interaction dominant (Gi-Tak Chae et al., 2006). Gibbs plots for postmonsoon and pre monsoon is shown in Figure 4. According to the Gibbs diagram, for the study area, the evaporation and rock–water interaction dominate the water chemistry in both seasons of the groundwater for they fall under its influence for both the Gibb’s ratios I-Na+K/ (Na+K+Ca) representing the cations and II- Cl/ (Cl+HCO3) representing the anions. Most of the samples fall in evaporation field due to salt water intrusion.
6 7 8 9
% of samples in this category for PostMonsoon 44.4
% of samples in this category for PreMonsoon 88.8
00.0
03.7
55.5
11.1
100.0
96.3
3.7 55.5 00.0
44.4 07.4 00.0
0.0
40.7
Table 3. Classification of water according to their types
0.0
48.1
To define a composition class, Back and Co-workers suggested subdivisions of the tri-linear diagram. The cations and anion fields are combined to show a single point in a diamond-shaped field, from which inference is drawn on the basis of hydrogeochemical facies concept. It clearly explains the variations or domination of cation and anion concentrations during pre and post-monsoon as shown in Figure 5.
Fig. 4 Gibbs diagram for the groundwater samples (Post and Pre-monsoon)
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Fig. 5 Piper diagram for the groundwater samples (Post and Pre-monsoon) ORIGINAL
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Alkaline earths exceeds alkalies (44.4%) and (88.8%) and the type strong acids exceeds weak acids (100.0%) and (96.30%) during Postmonsoon and Pre-monsoon, respectively. Rapid urbanization and industrialization make an impact on groundwater quality of the study area. The reason is groundwater passing through igneous rocks dissolves only small quantities of mineral matters because of the relative insolubility of the rock composition. While the high concentration of sulfates may be attributed to the contamination by the untreated industrial and domestic waste effluents (Baruah et al., 2008).
5. Conclusion
Based on the BIS (2012), the cations Na, Ca, Mg and K concentrations were above permissible limit and anions Cl, HCO 3 are above permissible limit in most of the samples, but SO4 and NO3 are within permissible limit which indicates that most of the samples are not suitable for drinking purpose as well as agriculture uses. Box and Whisker plot shows the abundance of the major cations in the order of Na > Ca > Mg in post monsoon and Mg > Ca > Na in pre monsoon. The abundance of major anions is in the order of Cl > HCO 3 > SO4 during both seasons. USSL diagram represents the majority of the samples belongs to C3S1 (high salinity, low sodium) and C4S1 (very high salinity, low sodium) during post and pre monsoon seasons respectively, and the samples are not suitable for drinking purpose due to salt water intrusion. Gibbs plot illustrates that during both the seasons, evaporation increases the salinity and the higher concentration of Na and Cl ions increases the TDS. According to Piper diagram, alkaline earths exceeds alkalies (44.4%) and (88.8%) and the strong acids exceeds weak acids (100.0%) and (96.3%) during Post-monsoon and Pre-monsoon, respectively due to rapid urbanization and industrialization.
Acknowledgement
First author thank the UGC for the financial support extended to this research in the form of UGC-SAP-DRS II. The authors are grateful to University of Madras and thankful to Prof. K.K. Sharma, Head, Department of Applied Geology for the support and infrastructure provided for this study. With gratitude the authors are grateful to Tamil Nadu Water Supply and Drainage Board (TWAD Board) for providing the facility of analyzing the groundwater samples in their laboratory.
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