Application of statistical techniques to identify the hydrogeochemical processes in coastal aquifers of Pondicherry region- Tamil Nadu

© 2014, Capital Publishing Company.Groundwater pollution can be illustrated as degrading of water quality for any usage. The Eleven hydrochemical parameters of groundwater samples from different formation were used in this study to understand groundwater chemistry in this complex multilayer aquifer system. The statistical analysis of the results shows that dominant process of weathering of feldspar, pyroxene and ion exchange. The water flows along the formation dissolving these ions along its flow path through the process of leaching of the secondary salts inherited in the formation obtained by the mixing of several geochemical processes. The anthropogenic impacts in the groundwater are noted in the younger formation than that of Cretaceous and Lower Cuddalore

A Study on the Behaviour of Total Carbon and Dissolved Organic Carbon in Groundwaters of Pondicherry Region, India

Organic carbon concentrations can vary considerably, both spatially and temporally, so a large number of analyses are frequently required to produce a representative estimate of concentrations. Natural organic carbon is mainly derived from decomposing vegetation and other organic matter in the soil zone. In this scenario, a baseline attempt was made to study the behaviour of organic carbon content in groundwater by collecting samples from the layered aquifer sequence of Pondicherry. The samples were collected from Recent Alluvium (30), Upper Cuddalore(13), Lower Cuddalore (13), Other Tertiary formation (7), Mixed aquifer (5) and Cretaceous formations (24). The analysis of these samples show that higher concentration of Dissolved Organic Carbon (DOC) was noted in the Alluvial formation and the average concentration was higher in Upper Cuddalore Formation. The samples of these formations were compared with pH, Ionic strength, and log pCO2 and bicarbonate concentration. The alluvial aquifer shows that pH governed dissolution along the coastal tracts and in Upper Cuddalore formation it’s based on interaction between aquifer matrix and groundwater

Significance of pCO2 values in determining carbonate chemistry in groundwater of Pondicherry region, India

The partial pressure of Carbon-Di-oxide plays a significant role in the water chemistry. It reflects thegeochemical process and relates to the saturation index (SI) of the Carbonate minerals. A total number of 98 samples were collected from layered sequential aquifers like Alluvium, Upper Cuddalore sandstone, Lower Cuddalore Sandstone and Cretaceous formations, during Pre-Monsoonand Post-Monsoon seasons. Chemical parameters of groundwater such as pH, EC, TDS, Na+, K+, Ca2+, Mg2+, Cl–, HCO–3 , SO2–4 , PO3–4 and H4SiO4 were determined. The study shows that an increase in the log pCO2 values during water-rock interaction which influences the processof mineral dissolution. Saturation index of the carbonate minerals like Calcite, Aragonite, Dolomite and Magnesite were derived and compared with the log pCO2 values. In both the seasons the decreasing log pCO2 increases the saturation index of most of the carbonate minerals studied. The saturation index of almost all carbonate minerals during both the seasons showed negative correlationirrespective of the formation. Log pCO2 also develops a negative correlation with pH in groundwater of the study area

A Study on the Impact of Landuse Pattern in the Groundwater Quality in and Around Madurai Region, South India-Using GIS Techniques

The study was aimed to identify and delineate the groundwater potable zone in and around Madurai region. The study area is composed of Charnockites and Khondalites of Archaean age. The information of Lithology, geomorphology and land use/land cover was generated using the Resourcesat (IRS P6 LISS IV) and Survey of India (SoI) toposheets of scale 1: 50,000 and integrated them with GIS to identify the groundwater potable zones of the study area. On the basis of hydrogeomorphology, groundwater potential zones was identified and delineated. From the overlay analyses of landuse and EC, it is inferred that poor category groundwater is found in the scrub forest, current fallow, canal and scrub with land areas

Study on the saturation index of the carbonates in the groundwater using WATEQ4F, in layered coastal aquifers of Pondicherry

A study was conducted to bring out the relationship and behavior of different Saturation Index (SI) of carbonate minerals in layered coastal aquifers. Carbonates present in groundwater aids in different nature of the water like hardness, partial pressure of carbon-di-oxide (pCO2), pH and saturation index of different carbonate minerals at various temperatures. The SI of the carbonates helps us to define the thermodynamic stability of water and to find out the geochemical behavior of water. 98 groundwater samples were collected from specific aquifers (alluvium, upper Cuddalore, lower Cuddalore and Cretaceous) during Pre-Monsoon (May 2007) and Post-Monsoon (January 2008) seasons. The physicochemical parameters such as pH, EC, Ca, Mg, Na, K, Cl, HCO3, SO4 and PO4 were analyzed. Geochemical model, WATEQ4F was used to calculate the SI of different minerals. The SI was studied in relation to mHCO3 concentration, pCO2 and correlation between SI of different minerals

A study on the interpretation of spontaneous potential and resistivity logs in layered aquifer sequence of Pondicherry Region, South India

Geophysical logs provide a strong mechanism for interpretation and determination of the depositional environments, facies and also help in interpretations of hydrogeologic units. Spontaneous potential (SP) and resistivity logs can be used as an indicator of textural parameters. Pondicherry region has a complicated geology and with formation of different ages. The boreholes (BH) of this region are examined for litholog, SP and resistivity from four different BH locations, viz, Ariyankuppam, Chinnaverampattinam, Thavalakuppam and Nallavadu. These locations were studied and interpreted by using the shapes of the curves to identify the depositional environments, and this was later compared with the vertical litholog profile. Comparing the variation of these logs, the lateral variation of sedimentary facies was also attempted. The average resistivity values of Ariyankuppam, Chinnaverampattinam, Thavalakuppam and Nallavadu are 42.4, 30.4, 50.4 and 28.3 Ωm, respectively. Majority of the resistivity values corresponds from fine- to medium-grained sand, clayey pebbles, fine to very coarse sand and clayey sand with lignite. Frequency of resistivity values in each BH were identified for determining the dominant representative grain size. The study has pointed out the lithological variation of the system laterally and vertically using geophysical well logs

An attempt to understand the behavior of dissolved organic carbon in coastal aquifers of Pondicherry region, South India

Groundwaters of the coastal region are significant and serve as a fragile ecosystem in the sedimentary terrain. The Pondicherry region is characterized by different geological formations of distinct geological epochs Cretaceous, Tertiary and Quaternary. Ninety-three samples were collected from specific aquifers with respect to spatial distribution [Alluvium (31), Upper Cuddalore (13), Lower Cuddalore (13), Other Tertiary (7), Cretaceous (24) and Mixed—multiple completion aquifer (5)]. The collected samples were analyzed for major ions Ca2+, Mg2+, Na+, K+, HCO3−, Cl−, PO42−, SO42−, F and DOC. Stables isotopes of δ18O, δD and δ 13C were also analyzed along with heavy metals like Al, Ba, Fe, Sr, Cd and Zn. The δ18O ranges between −6.85 and −2.15 ‰, and δD ranges between −43.94 and −19.41 ‰. The distribution of these environmental isotopes in groundwater of this layered aquifer sequence was also attempted. A comparison of the isotopic data with the rainfall, Local Meteoric Water Line with a equation of δD = 7.398 * δ18O + 5.067, Indian Meteoric Water Line and Global Meteoric Water Line was performed. The δ13C values for groundwater ranges from −5.3 to −18.1 ‰. The result indicates that the groundwater in the study area is mainly meteoric in origin, and few samples show evidence of evaporation. The dissolved organic carbon (DOC) is a very important component in biogeochemical cycling of elements characterized by high susceptibility to leaching. The range of the DOC in the study area is 0–16 mg/L. Factor analysis was applied to classify the groundwater samples and to identify geochemical processes controlling groundwater geochemistry. The Alluvium aquifers show a complex hydrogeochemistry than the older aquifers. The major factor influencing the hydrogeochemistry of the region is rock–water interaction and anthropogenic processes. Hence, metal mobility of the groundwater shows the correlation of metal bonding and DOC. The relation between the DOC and heavy metal concentration in the aquifers was also identified

Dissolved Organic Carbon in Multilayered Aquifers of Pondicherry Region (India): Spatial and Temporal Variability and Relationships to Major Ion Chemistry

Carbon, which is an essential element found in rocks and minerals, is used by biologically diverse life forms as a source of energy. Natural organic carbon is mainly derived from decomposing vegetation and other organic matter in the soil zone. Dissolved organic carbon (DOC) is an important component in biogeochemical cycling of elements characterized by high susceptibility to leaching. The significance of DOC was studied in layered coastal aquifers of the Pondicherry region during four different seasons. Pondicherry region has varied geological setup ranging from Cretaceous to Recent formations. A total of 324 groundwater samples were collected from various aquifers, namely Alluvium, Tertiary, Cretaceous, and Mixed formations, during different seasons of pre-monsoon, southwest monsoon, northeast monsoon, and post-monsoon. The samples were analyzed for major ions and DOC. The range of DOC in the study area is 0–10 mg/l. Very high DOC concentrations were measured in most of the samples from Alluvium and Upper Cuddalore Formation and in few samples from the Lower Cuddalore Formation. The relationships of DOC with other ions in this study indicate that the hydrochemistry of groundwater was controlled by both aerobic and anaerobic environments in the different formations of the study area