Rock/Water Interaction Study in Deep Crystalline Rocks Using Isotopic and Uranium Series Radionuclide Techniques

AbstractConcentrations and isotope ratios of natural decay series radionuclides have been studied in three contrasting crystalline rock drillcore sections intersecting water-conducting fractures deep in the bedrock. Radioactive disequilibria resulting from rock-water interactions were observed in two of the cores. These indicated uranium migration along distances of 40 cm or more on a timescale of 106 years in conjunction with thorium immobility under the same conditions. Fracture surface minerals showed a high affinity for radionuclide retardation and a limit of about 3 cm is suggested for the migration of radionuclides from fracture fluids into the saturated rock. This limit may correspond to enhanced matrix porosities resulting from earlier hydrothermal activity along the same channels.

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Deep Groundwater Recharge Mechanism in the Sedimentary and Crystalline Terrains of Sri Lanka: A Study Based on Environmental Isotopic and Chemical Signatures of Spring Water

10.22541/au.160647860.04328899/v1 ◽

2020 ◽

Author(s):

Sakhila Priyadarshanee ◽

Zhonghe Pang ◽

Viraj Edirisinghe ◽

H.A. Dharmagunawardhane ◽

H.M.T.G.A. Pitawala ◽

...

Keyword(s):

Sri Lanka ◽

Geochemical Characteristics ◽

Thermal Springs ◽

Thermal Waters ◽

Deep Groundwater ◽

Flow Paths ◽

Water Interaction ◽

Deep Aquifers ◽

Regional Flow ◽

Rock Water Interaction

In many instances, dynamic, potential status and geochemical characteristics of groundwater discharging through natural springs are not well known. Present study has assessed the deep groundwater in the form of thermal and non-thermal spring in artesian condition in the selected zones in Sri Lanka, using isotope and geochemical characteristics. The results revealed that evaporation-fractional crystallization and cation-exchange in the sedimentary aquifers while rock-water interaction in crystalline deep aquifers, are the significant mechanism that control the groundwater chemistry. All the deep groundwater recharged from meteoric water at different elevations and further influenced by either evaporation or rock-water interaction during the subsurface flow. Artesian aquifers in the sedimentary terrain in the north-western coastal zones showed the recharging elevation as from 100 to 200 m amsl. They are not mixed with sea water and slightly impacted by the locally evaporated surface waters. Almost all these waters are comparatively old; indicating slow movement along the regional flow paths. Considering the recharge and discharge conditions of artesian non-thermal waters in the Southern lowlands of crystalline terrain can be classified as non-mixed, non-evaporated and young groundwater with higher elevation recharge. The artesian non-thermal waters in the East North Central lowlands, have shown the same characteristics but with evaporated conditions. All artesian thermal waters are tritium free, hence they are older and deep percolated. Intensive rock-water interaction and higher altitude origin were observed in some thermal springs. Some spring clusters in the weathered overburden have shown significant mixing with recent local rains. Non-mixed, non-evaporated and less rock-water interacted nature is a significant in two thermal springs that emerges through (chemically inert) quartzite bed rock. Both thermal and non-thermal water with artesian condition have clearly indicated that they are originated from a common recharge source but with different flow paths in different penetration depths and travel distances, resulting different chemical characteristics. Fresh water springs are mostly young and recharged from local rains followed with shallow percolation.

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Occurrence and Health-Risk Assessment of Trace Metals in Geothermal Springs within Soutpansberg, Limpopo Province, South Africa

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17124438 ◽

2020 ◽

Vol 17 (12) ◽

pp. 4438

Author(s):

Olatunde Samod Durowoju ◽

Georges-Ivo Ekosse Ekosse ◽

John Ogony Odiyo

Keyword(s):

South Africa ◽

Drinking Water ◽

Trace Metals ◽

Health Risk ◽

Trace Metal ◽

Limpopo Province ◽

World Health ◽

Geothermal Springs ◽

Water Interaction ◽

Rock Water Interaction

Geothermal springs are natural geological phenomena that occur throughout the world. South Africa is blessed with several springs of this nature. Limpopo province contains 31% of all geothermal springs in the country. The springs are classified according to the residing mountain: Soutpansberg, Waterberg and Drakensberg. This study focused on the geothermal springs within the Soutpansberg region; that is, Mphephu, Siloam, Sagole and Tshipise. The study was aimed at assessing the occurrence and potential health risk associated with drinking water from geothermal springs within Soutpansberg. Geothermal springs and boreholes were sampled for a period of 12 months (May 2017–May 2018) to accommodate two major seasons in the study areas. The physicochemical and trace metal compositions of the geothermal springs and boreholes (tepid and hot) were analyzed using ion chromatography (IC) (Dionex Model DX 500) and inductively coupled plasma-mass spectrometer (ICP-MS). Trace metal concentrations of the geothermal springs and boreholes were within permissible drinking water guidelines by the South African National Standards (SANS) and World Health Organisation (WHO), with exception of mercury (Hg), which is high in summer season. The bioaccumulation from regular consumption could, however, result in negative effects. Pearson’s correlation revealed that there is a direct relationship between temperature and pH, and some of the trace metals (V, Zn, Hg, Pb). This implies dissolution of minerals (rock-water interaction) under slightly high temperature. Multivariate statistics further elucidate the relationship and possible sources of the trace metals. Therefore, it can be inferred that the rock-water interaction is the main geochemical process governing the release of trace metals in groundwater. Hazard Index values for both children and adults were higher than 1, and this implies that the communities are at high risk of non-cancer health effects. Further, As, Cr and Cd were found to be the highest contributors to the potential cancer risk in the study areas, with children having a higher risk than adults. Therefore, there is a need for clinical/epidemiological study, and regular monitoring and control measures, to verify actual prevalence of cancer and protect human health, particularly the children, within the study areas.

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The chemical and isotopic record of rock-water interaction in the Sherman Granite, Wyoming and Colorado

Contributions to Mineralogy and Petrology ◽

10.1007/bf00398915 ◽

1982 ◽

Vol 78 (3) ◽

pp. 209-219 ◽

Cited By ~ 51

Author(s):

R. A. Zielinski ◽

Z. E. Peterman ◽

J. S. Stuckless ◽

J. N. Rosholt ◽

I. T. Nkomo

Keyword(s):

Water Interaction ◽

Rock Water Interaction

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