Fluoride contamination in water is a major problem across the globe, with health hazards such as dental and skeletal fluorosis. Most earlier studies are confined to local or regional scales. As the problem has serious socioeconomic implications, there is a need for a global perspective. Thus, here we review worldwide research for nearly a century on fluoride contamination in water. We investigated the distribution of fluoride contamination in water, its sources, mobilization and association. The major findings are: (1) Anomalous fluoride concentration in groundwater is mainly confined to arid and semiarid regions of Asia and North Africa. (2) The geogenic sources of fluoride in water are mainly fluorine-bearing minerals in rocks and sediments, whereas anthropogenic sources of fluoride in water are mainly pesticides and industrial waste.(3) Fluoride mobilization from geogenic sources is mainly controlled by alkalinity and temperature. (4) Fluoride occurrence in water is associated with ions such as sodium, arsenic chloride and bicarbonate. There are few associations of fluoride in water with calcium and magnesium.

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The Yamuna flood plains spread across the northern part of Indian subcontinent is home to millions of people. The ever-growing population in these plains make it difficult to sustain the demand of freshwater resources. However, the productive aquifers of flood plains could provide solution for these issues. In this context, it is necessary to understand the aquifer characteristics. Thus, the paper attempts to characterize the aquifer in Palla area of the flood plain using integrated approach. Besides, grain size analysis and site-litholog study, the nature of aquifer material was also ascertained from bulk mineralogy of the sediments using X-Ray Diffraction. The aquifer parameters were estimated with help of long duration pumping test data. Moreover, the effect of pumping on salinity variation and hydrochemical facies evolution was also examined. The sand dominant, unconfined aquifer was estimated to have horizontal hydraulic conductivity in the range of 25 m/day and vertical hydraulic conductivity of 6-7 m /day. While the specific yield of the aquifer was estimated in the range of 0.07-0.08 .It is observed that under conducive active flood plain environment, the given sand mineralogy at the site does not allow salinity increase in groundwater even after more than a decade of groundwater pumping. In fact, over years, hydrochemical facies have evolved towards Bicarbonate type. These things put together make the active flood plain aquifer a sustainable groundwater resource.

The Khammam Schist Belt (KSB), southeastern India, represents a part of the collision zone that is sandwiched between the Eastern Dharwar Craton to the west and the Eastern Ghats Mobile Belt (EGMB) to the east. Quartzofeldspathic gneisses of the EGMB and garnet-kyanite metapelites of the KSB have been investigated to characterize P-T-t evolution of the Khammam region. Pseudosection modeling reveals that the melt-bearing quartzofeldspathic gneiss experienced peak and post-peak metamorphism at P-T conditions of 7.9-8.1 kbar/790-810 °C and ~ 7.0 kbar/740-750 °C, respectively. In contrast, metapelite witnessed peak metamorphism at 7.4-7.8 kbar/600-640 °C, followed by post-peak retrogression at 6.1-6.6 kbar/590-625 °C. U-Th-(total) Pb monazite ages from the gneiss constrain the peak and retrograde metamorphic episodes at 1.63-1.53 Ga and 1.48-1.38 Ga, while those in the metapelites were determined at 1.25-1.20 Ga and 1.18-1.10 Ga, respectively. These P-T-t estimates indicate that the KSB, Vinjamuru, and Ongole domains evolved distinctly during Late Paleoproterozoic-Late Mesoproterozoic. The younger ages (0.90-0.81 Ga) were ascribed to the formation of the Eastern Indian Tectonic Zone, implying its extension beyond the western margin of the EGMB. Besides, the distinct Neoarchean ages (2.79-2.45 Ga) are related to the Archean protolith of the quartzofeldspathic gneisses, which were likely derived from the Archean crust of the Napier-Rayner Complex. This tectonothermal restoration is new and characterizes the Khammam region as the hot and composite collision zone with protracted geological history.