Dataset of geophysical electrical resistivity and subsurface profiling for natural resources exploration in a hard rock terrain of Tamil Nadu, India.

Geophysical resistivity technique; vertical electrical sounding (VES)/earth resistivity test (ERT) was carefully done at 35 locations in a hard rock terrain of Tamil Nadu, India to evaluate natural resources such as groundwater, economic mineral deposits, etc., Data acquisition was done by CRM-500 Aquameter along with GPS, topographic map, Brunton compass, measuring tape, field notebook, hammer, iron rods (electrodes), and batteries. Furthermore, the major four subsurface layers' thickness, resistivity, and pseudo-section profiles were identified from the resistivity dataset using IPI2WIN. The resistivity curve type is also evaluated from the consecutive subsurface layers' resistivities. These can be helpful in groundwater potential zone identification studies. The entire dataset from this research can be useful in groundwater exploration, management, economic mineral exploration, waste disposal sites, reservoir, and dam site selections, and identifying the structural controls such as fractures, joints, buried anticlines, etc., The data also can be coupled with other regional geological and geophysical datasets for many natural resource exploration and exploitation studies.

Fate and transport of strontium in groundwater from a layered sedimentary aquifer system.

In this article, strontium distribution in sedimentary coastal aquifers of Eastern India was studied and its association with groundwater particles has been ascertained using hydrochemical and morphological tools. Groundwater contains Sr2+ in the range of 0.08-4.0 mg/L with higher concentrations in Cretaceous formation. The particle number in groundwater varies from 4.5 × 105 to 3.3 × 106 per liter and follows the power law distribution with respect to the particle diameter. The calculated ß values (2.54 and 4.03) signify the abundance of smaller particles over larger ones. The particle concentration of size range 0.45-8 µm is found to be 0.64-2.6 mg/L. Elemental data of groundwater particles clearly suggest their origin from the host rock minerals. Zeta potential data indicates diverse nature of colloids suggesting prevalence of both positive and negative charged species in the groundwater. The hydrochemical interpretation along with speciation studies infers that high Sr2+ in groundwater is a result of incongruent dissolution of carbonate minerals and the dissolved Sr2+ partitions into both dissociated and un-dissociated forms. Based on the Sr2+/Ca2+ ratio and mineral saturation indices, it can be inferred that the Sr2+ is preferentially associated with colloids over large particles and the migration takes place through sorption of Sr2+ onto clay-bound (extrinsic) colloids in groundwater. This study describes the mechanism of strontium release into groundwater and provides insights into the role of groundwater particles in controlling the strontium migration to deep aquifers.

Arsenic distribution in sediments of multi-tier sedimentary formation of coastal Pondicherry, India - Implications on groundwater quality.

In this work, sediments collected from a 150-m deep litho-section of a coastal region and encompassing Quaternary, Tertiary and Cretaceous sedimentary formations were studied for arsenic distribution and other trace and redox sensitive elements. Arsenic concentration in the sediments is found to vary from <0.5 to 30 mg·kg-1 and showed an increasing trend with the depth. The highest As content is observed at a depth of 129-131 m bgl belonging to Cretaceous formation. Though XRD studies do not indicate any arsenic mineral in sediments, positive correlations between As-Fe and S, as well as ESEM-EDS and TXRF studies confirm the presence of As sorbed to FeS mineral. The organic matter and As correlations suggest microbial mediated reduction process, which may pose future risk to water quality of this prolific coastal fresh water aquifer system. The elemental profiles infer that Cretaceous and Tertiary formations demonstrate inner shelf and marginal marine condition respectively.