Research Journal of Chemical Sciences ______________________________________________ ISSN 2231-606X Vol. 4(4), 99-106, April (2014) Res. J. Chem. Sci. International Science Congress Association 99 Hydrochemistry of Groundwater in and around Chennai, India - A Case StudyAnnapoorani A., Murugesan A., Ramu A. and Renganathan N.G.4 Department of Chemistry, Vel Tech Multi Tech Dr RR, Dr SR Engineering College, Avadi, Chennai-600 062, TN, INDIA Department of Chemistry, Sriram Engineering College, Perumalpattu, Veppampattu RS, Chennai-602 024, TN, INDIA School of Chemistry, Madurai Kamaraj University, Madurai – 625 021, TN, INDIA Department of Chemistry, Vel Tech Dr RR, Dr SR Technical University, Avadi, Chennai – 600 062, TN, INDIAAvailable online at: www.isca.in, www.isca.me Received 2nd February 2014, revised 10th March 2014, accepted 15th March 2014Abstract Groundwater quality in and around Chennai is to be known prior to its utility for the survival. With this objective, 240 samples from 60 places were collected in and around Chennai. The analysis and classification is stipulated by international standards. Hydro-chemical and statistical analysis were carried out to assess the groundwater quality. The physico-chemical parameters, sodium / chloride ratio, chloride / bicarbonate ratio, calcium / magnesium ratio are used to identify the intrusion of salt water in the coastal aquifers. Calcium / Sodium ratio is used to identify the hard rock interaction or sedimentary rock interaction. From the study, it is concluded that, groundwater in Chennai is a threat under the saltwater intrusion. The anthropogenic activity is a key factor for seawater intrusion and contamination. Keywords: Physico-chemical analysis, water quality, groundwater classification and seawater intrusion Introduction In India apart from thousands of villages many urban centers are located on the coastal tracks. In these centers apart from dwelling apartments industrial establishments have also come up. Due to this overexploitation of groundwater resources has happened. This paves the way for the intrusion of sea water into the groundwater in these areas. For industry, drinking and agriculture purposes the ground water plays a very important role. It has been reported1-2 that the wells become either dry or intrusion of salt water is due to low rainfall and high evapotranspiration and there is no replenishments with fresh rain water. The water becomes more saline during post monsoon because of increase in water table which leads to dissolve of the salts. In the wells near to the coastal areas sea water intrusion takes place due to over exploitation of groundwater. Potability of groundwater has been well documented3-7. Physicochemical characteristics due the seasonal variation and influence of heavy metal in the groundwater has been studies8-12. One of the most common methods for assessing sea water intrusion into the wells or water sources near coastal areas is a periodic analysis of groundwater chemistry13-18. The aim of the present communication is to assess and report the quality of water in Chennai. Study area: The study area Chennai city covers half of the Kanchipuram and Thiruvallur District. The entire region is covered by sand up to a depth of about 18m. The latitude and longitude of the study area is 12.992 to 13.134 and 80.240 to 80.298. It is shown in table-1 and figure-1. The entire region is covered by sand up to a depth of about-10m with respect to sea level. In some locations the inner horizon of sand is mixed with clay and made up of clayey sand. The sand and clayey sand region is followed by the weathered rock up to depth of about – 20 m with respect to sea level. Material and MethodsTo access the quality of water in Chennai, study has been undertaken on 2011. 240 water samples from 60 places in and around Chennai were collected from bore wells. The samples were collected in polythene bottles for the analysis of the ions. The EC, pH and TDS were measured immediately at sampling site using portable meters. All the analysis is carried out using AR chemicals and distilled water. Collected samples were brought to the laboratory on the same day and analyzed for determining the various chemical parameters such as sodium, potassium, magnesium, calcium, sulphate, chloride, fluoride, dissolved oxygen, biological oxygen demand, total hardness, carbonate, bicarbonate and hydroxide using standard procedures prescribed in APHA. TDS, Na, Ca2+, Mg2+, CO2-, HCO, Cland SO2- levels were also measured. Groundwater quality assessment has been made based on the above physico-chemical parameters and metal concentration in the water samples collected from Chennai city. The Langelier saturation index has been calculated and it is between -3 and +3 and this suggests that the water was corrosive in the areas under study. Calculations of ionic deviations have been done to understand the hydro chemical processes. Sea water mixing index has been made to evaluate the relative degree of sea water mixing. Mg2+/Ca2+ ratio with TDS and Na/Cl ratio with TDS had been made and based on this relation saline intrusion has been assessed and discussed. Results are presented and discussed in this paper. Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(4), 99-106, April (2014) Res. J. Chem. Sci. International Science Congress Association 100 Table-1 Location Site with Latitude and LongitudeS.No Sample Code Latitude Longitude Sample Places 1 C1 12.989 80.195 Adampakkam 2 C2 13.001 80.256 Adayar 3 C3 13.087 80.215 AnnaNagar 4 C4 12.682 79.985 Chengalpattu 5 C5 13.292 80.171 Chennaivekkam 6 C6 13.231 80.179 Cholavaram 7 C7 12.951 80.135 Chrompet 8 C8 13.023 80.201 Ekkattuthangal 9 C9 13.204 80.321 Ennore 10 C10 13.078 80.274 George Town 11 C11 13.201 80.321 IndiraGandhi Kuppam 12 C12 12.916 80.254 Injambakkam 13 C13 13.035 80.137 Iyappanthangal 14 C14 13.318 80.337 Kattupalli 15 C15 13.35 80.283 Kattur 16 C16 12.793 80.212 Kelambakkam 17 C17 13.043 80.199 KK Nagar 18 C18 12.846 80.057 Kuduvancheri 19 C19 12.994 80.091 Kundrathur 20 C20 12.922 80.132 Kuppuswamy Nagar 21 C21 12.978 80.178 Madipakkam 22 C22 13.16 80.267 Manali 23 C23 13.032 80.111 Mangadu 24 C24 13.093 80.258 Mannady 25 C25 12.941 80.244 Mettukuppam 26 C26 13.29 80.224 Mettupalayam 27 C27 13.27 80.279 Minjur 28 C28 13.025 80.237 Nandanam 29 C29 12.846 80.226 Navallur 30 C30 12.948 80.254 Neelankarai 31 C31 12.753 80.105 Nellikuppam 32 C32 13.067 80.223 Nungambakam 33 C33 12.64 80.171 Paiyanoor 34 C34 12.966 80.123 Palavaram 35 C35 13.118 80.232 Parambur 36 C36 12.906 80.095 Perungalathur 37 C37 12.809 80.151 Pongari 38 C38 13.335 80.191 Pooneri 39 C39 12.617 80.174 Poonjeri 40 C40 13.049 80.075 Poonthamalee 41 C41 13.043 80.157 Porur 42 C42 13.337 80.145 Puduvoyal 43 C43 13.183 80.284 Sadayakuppam 44 C44 13.139 80.268 Salaivayul 45 C45 12.895 80.223 Sholinganallur 46 C46 12.755 80.001 Singa Perumal Kovil 47 C47 13.003 80.199 St.Thomas Mount 48 C48 13.024 80.237 T.Nagar 49 C49 12.993 80.248 Tharamani 50 C50 12.724 80.187 Thiruporur 51 C51 13.157 80.303 Thiruvattriyur 52 C52 12.87 80.243 Uthandi 53 C53 12.892 80.085 Vandaloor 54 C54 12.98 80.224 Velacherry 55 C55 13.058 80.137 Velppanchavadi 56 C56 13.085 80.260 Vepery 57 C57 13.219 80.249 Vichoor 58 C58 13.231 80.245 Villivoyol 59 C59 13.072 80.197 Virugambakkam 60 C60 13.139 80.285 Washermint Figure-1 Study Area Map of Chennai City, Tamil Nadu, South India Results and Discussion Based on classification15 the table-2 shows that the salinity character was dominant in 57% of water samples in the study area undertaken. Total dissolved solids also showed a wide variation from 500 to 13390 ppm. Higher values of EC and TDS are recorded in George Town and Taramani. This is closer to Covam River or Adyar River or Buckingham Canal or Bay of Bengal. Based on classification19, 17% of groundwater samples are fresh water and this is based on the Total Dissolved Solids which is generally less than 1000 ppm. Chemical analysis of samples indicates that most dominating ions are sodium, chloride, calcium, magnesium, bicarbonate, Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(4), 99-106, April (2014) Res. J. Chem. Sci. International Science Congress Association 101 sulfate, potassium, nitrate, phosphate and fluoride and they are in the order as indicated here. The sodium is the dominating cation varied from 46 to 4624. The potassium content of natural waters is usually less than that of sodium, calcium, magnesium. The cation such Ca, Mg, K are varied from 20 to 730, 36.8 to 1456 and 0.3 to 1893 ppm respectively. The concentration of carbonate ions are in traces, and the bicarbonates concentrations are considerable in all water samples analyzed. Among the anions, chloride is the most dominating anion varied from 90 to 4500ppm. The high chloride content of the groundwater is mostly due to sea water intrusion. Another important major anion is sulphate. Sulphate is found in the water samples and this may be from the geological sources. The other anion such as bicarbonate, sulphate, nitrate, phosphate and fluoride varies from 75 to 625, 12.6 to 1948.57, 0 to 500, 0 to 2 and 1ppm respectively. From the careful observation of these data it is clear that the sodium and chloride ions showed a wide range of distributions and higher standard deviation. This suggests a possible intrusion of nearby saline water which has comparatively high concentration of sodium and chloride. Water Quality Index is less than 20% in 83% the water samples in Chennai city. Water Quality in the following places C4, C7, C8, C12, C14, C18, C20, C21, C30, C36, C46, C47, C53, C59 is analyzed, calcium content is more compared to the sodium content as well as Ca/Na ratio is greater than 1 indicating that nature of the place was hard rock interaction, but it has high TDS content which may be due to the anthropogenic activity. In overall Chennai 50% of the sampling station exists the permissible limit and they are converted into brackish in nature. 35% of the sampling station are started to convert from fresh to brackish and the remaining 15% of the samples are fresh in nature (C3, C4, C7, C8, C14, C31, C38, C42, and C47). From this study it is seen that groundwater quality is worst in the C2, C5, C9, C10, C11, C15, C16, C17, C22, C24, C25, C26, C28, C29, C32, C33, C35, C39, C41, C43, C44, C45, C49, C51, C52, C56 and C60. Maximum values are found in all the parameters in these areas. The groundwater quality is excellent C3, C4, C7, C8, C14, C31, C38, C42 and C47 in these areas and water can be used for the house hold purposes. In the remaining areas water quality is not worst or best but it is in the intermediate level and the water in these areas can be used for the house hold purposes. Kurtosis was applied on data matrix to measure peakedness of the probability distribution. Distribution with positive kurtosis has a higher probability of variables than the normal distribution around the mean and also indicates a higher probability of distributed variables with extreme values. A distribution with negative kurtosis indicates a lower probability of normally distributed variables of values near the mean as well as extreme values20 From the statistical table, high positive values for TDS, sodium, potassium, chloride indicating distribution is peaked. Minimum coefficient of variation indicates that there is not much variation in pH in all the samples. Minimum Standard deviation and Standard error for pH and maximum for sodium and total dissolved solids. High level of sodium and chloride in coastal groundwater indicates the significant effect of sea water mixing, but there is a considerable amount of bicarbonate and calcium which indicates the hard rock interaction. The plot of bicarbonate/chloride versus TDS shows regression slope is negative in the high TDS range, while the slope is positive in the low TDS concentration range. The ground water with high TDS concentration is enriched with chloride and the groundwater with low TDS concentration is not or less affected by saline water. Variation of Calcium/Sodium ratios with TDS showed a similar trend and subsequently similar interpretation in both the seasons. The high TDS recorded in the following groundwater samples such as the C2, C5, C9, C10, C11, C15, C16, C17, C22, C24, C25, C26, C28, C29, C32, C33, C35, C39, C41, C43, C44, C45, C49, C51, C52, C56 and C60 indicating the intrusion of salt water, the low TDS recorded in 35% of the sampling station. It is shown in figure-2. Figure-3 indicates that there is a minimum value of Calcium and Magnesium with bicarbonate except 25% of the sampling station where there is a hard rock interaction as indicated above. From the figure-4 it is clear that 50% of the sampling station ratio of sodium and chloride are high and equal indicating that there is intrusion of salt water and 25% of the sampling station indicates the content of calcium is higher than sodium due to hard rock interaction. Table-2 Statistical Data of Groundwater sample in ChennaiParameters Mg Ca HCO 3 - Cl - TDS Sodium Maximum 1456.0 730.0 725.0 4500.0 13390.0 4624.0 Minimum 39.6 20.0 100.0 90.0 350.0 46.0 Average 223.9 157.8 396.7 595.4 1565.0 865.54 Median 160.5 125.0 375.0 312.0 1100.0 459.4 Kurt 12.87 9.49 -0.55 11.15 23.7 4.55 Mode 200.0 82.5 375.0 918.0 590.0 46.0 Std. Dev. 266.9 120.5 155.37 818.1 1988.0 1010.0 Std. Error 34.5 15.6 20.1 105.6 256.6 130.4 Coefficient of Variation 11.9 7.6 3.9 13.7 12.7 11.7 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(4), 99-106, April (2014) Res. J. Chem. Sci. International Science Congress Association 102 *All parameters are expressed in ppm and EC is in µs/cm Figure-2 Ionic Ratio versus TDS Figure-3 Ions Versus Bicarbonate Ion Figure-4 Ions versus Chloride Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(4), 99-106, April (2014) Res. J. Chem. Sci. International Science Congress Association 103 Sodium/Chloride ratio indicates if the ratio is less than 0.86 it indicates that the water is freshwater (15%), if the ratio between the 0.86 to 1 it indicates that the water starts converting into brackish in nature, if the ratio is greater than 1 it indicates that there is intrusion of anthropogenic activity. The ratio of Calcium/Magnesium ratio is less than 1 in 50% of the places and it indicates that there is an intrusion of salt water and the remaining place the water is fresh or moderate in nature. If the ratio of calcium/sodium ratio is greater than 1 in 25% of the place it indicates that soil is rocky in nature. These are shown in figure-5. The Statistical data for this ratio is shown in table 3. Corrosivity Ratio is greater than 1 indicates that it will undergo corrosion, if it is less than 1, there will be no corrosion21. In our study area expect 15% of the samples others will undergo corrosion; it is due to intrusion of salt water or anthropogenic activity. From the figure-6 it is clear that among the anions the chloride was dominating anion and it is so in more than 50% of the samples but sulfate was present only 20%. Calcium is dominating only 25% where there is a hard rock interaction, the magnesium is dominating only 10%, and other remaining places are dominated by sodium and potassium. pH is within the range of 6 to 7.2. In 50% of the places water is having TDS around 1500 to 4000ppm. Figure-7 Trilinear is a diagram which indicates that sodium and chloride are having equal percentage but dissolved solid is around 60 to 80%. From the statistical data shown in table 4, it is clear that iron was present in 85% of the groundwater samples in Chennai city; the metal zinc is present in the water sample with maximum value of 0.62 ppm and lead with 0.07 ppm. Copper and Nickel present with the maximum value of 1.24 and 10.56 ppm. Table-3 Statistical Data for the Ionic RatioParameters Cl/HCO Ca/Mg Na/Cl Ca/Na CR Maximum 17.60 2.30 10.50 2.80 29.70 Minimum 0.25 0.08 0.16 0.03 0.36 Average 1.94 0.94 2.03 0.46 3.48 Median 0.77 1.00 1.24 0.27 1.21 Kurt 13.73 0.66 5.87 6.67 11.09 Mode 0.31 1.23 0.88 0.32 0.55 Std. Dev. 3.02 0.42 2.31 0.61 5.36 Std. Error 0.39 0.05 0.30 0.08 0.69 Coefficient of Variation 15.54 4.51 11.34 13.15 15.40 Table-4 Statistical Data for the Heavy MetalsParameters Iron Nickel Cu Zinc Pb Maximum 15.81 10.56 1.24 0.62 0.07 Average 7.03 0.52 0.17 0.19 0.01 Median 4.91 0.00 0.00 0.00 0.00 Kurt -1.64 59.97 2.61 -1.48 0.62 Mode 14.73 0.00 0.00 0.00 0.00 Std.dev. 6.1 3.94 0.28 0.24 0.02 Std. Error 0.79 0.51 0.04 0.03 0.00 Coefficient of Variation 8.67 76.07 16.48 12.98 19.46 Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(4), 99-106, April (2014) Res. J. Chem. Sci. International Science Congress Association 104 Figure-5 Ionic Ratio Versus Sample Code Figure-6 Durov Diagram of the sampling station Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(4), 99-106, April (2014) Res. J. Chem. Sci. International Science Congress Association 105 Figure-7 Trilinear Diagram of the sampling station Conclusion Calcium / Sodium ratio is greater than 1 as well as the calcium and bicarbonate is the dominating ions in the following sampling places C4, C7, C8, C12, C14, C18, C20, C21, C30, C36, C46, C47, C53, C59 reveals that groundwater is formed by hard rock interaction and it has high TDS content which may be due to the anthropogenic activity. In overall Chennai 50% of the sampling station exists the permissible limit and becomes into brackish nature. 35% of the sampling stations are under fresh to brackish and the remaining 15% of the samples are fresh in nature (C3, C4, C7, C8, C14, C31, C38, C42, and C47). From this study it is seen that groundwater quality were very poor in C2, C5, C9, C10, C11, C15, C16, C17, C22, C24, C25, C26, C28, C29, C32, C33, C35, C39, C41, C43, C44, C45, C49, C51, C52, C56 and C60. The groundwater quality is tolerance in C3, C4, C7, C8, C14, C31, C38, C42 and C47 and it can be used for the domestic purposes. In the other areas water quality is not poor and it is in the threshold limits. 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