Structure and Stability of Iron Fluoride at High Pressure–Temperature and Implication for a New Reservoir of Fluorine in the Deep Earth

Fluorine (F) is the most abundant halogen in the bulk silicate Earth. F plays an important role in geochemical and biological systems, but its abundance and distribution in the terrestrial mantle are still unclear. Recent studies suggested that F reservoirs in the deep mantle are potentially hosted in terrestrial oxide minerals, especially in aluminous bridgmanite. However, the knowledge about the formation and stability field of fluoride in the Earth’s interior is rare. In this study, we combine in situ laser-heated diamond anvil cell, synchrotron X-ray diffraction, and first-principles structure search to show that a new tetragonal structure of FeF3 is stable at pressures of 78–130 GPa and temperatures up to ~1900 K. Simulation predicted the tetragonal phase takes a much denser structure due to the rotation of FeF6 octahedral units. The equations of states of tetragonal FeF3 are determined by experiment and verified by simulation. Our results indicate that FeF3 can be a potential key phase for storing F in the Earth’s lower mantle and may explain some mantle-derived magma with high F concentration.

Grade Card Method of Ground Water Health Evaluation of Mustoor Sub-Watershed Chikballapur Taluk Karnataka

Ground water occurs commonly and is widely distributed and is the most reliable resource the quality of ground water needs to be monitored and preserved. In this study, as a part of the research work an attempt is made to assess the health of ground water in Mustoor sub-watershed. 11 Samples are selected from the influencing major villages and villages with surface waterbody in the sub watershed. A water grade card is an aid to educate and remind about the conditions of naturally available water resource around the users with the help of Water Quality Index method in comparison with Indian Standards IS 10500. Multi-metric indicators and indices aid to build a water grade card, in this study 11 samples of ground water are tested for eight selected Physico-chemical parameters (pH, turbidity, iron, fluoride, chloride, nitrate, total dissolved solids and total hardness) in March and October months, 2018 as Pre and Post Monsoon months. GWQI method helps in assigning the grades. It is intended for diverse users: like any individuals and institutions to policymakers and planners. The indicators collectively provide the overall health that is scored and is graded to report the condition or quality of the groundwater in the sub watershed in a better understanding way to the common people with the help of grades.