Leaching (chemistry) in the context of "Rare-earth element"

Sodium is a chemical element; it has symbol Na (from Neo-Latin natrium) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable isotope is Na. The free metal does not occur in nature and must be prepared from compounds. Sodium is the sixth most abundant element in the Earth's crust and exists in numerous minerals such as feldspars, sodalite, and halite (NaCl). Many salts of sodium are highly water-soluble: sodium ions have been leached by the action of water from the Earth's minerals over eons, and thus sodium and chlorine are the most common dissolved elements by weight in the oceans.

Sodium was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Among many other useful sodium compounds, sodium hydroxide (lye) is used in soap manufacture, and sodium chloride (edible salt) is a de-icing agent and a nutrient for animals including humans.

The Flint water crisis was a public health crisis from 2014 to 2019 which involved the drinking water for the city of Flint, Michigan, being contaminated with lead and possibly Legionella bacteria.

In April 2014, during a financial crisis, state-appointed emergency manager Darnell Earley changed Flint's water source from the Detroit Water and Sewerage Department (sourced from Lake Huron and the Detroit River) to the Flint River. Residents complained about the taste, smell, and appearance of the water. Officials failed to apply corrosion inhibitors to the water, which resulted in lead from aging pipes leaching into the water supply, exposing around 100,000 residents to elevated lead levels. A pair of scientific studies confirmed that lead contamination was present in the water supply. The city switched back to the Detroit water system on October 16, 2015. It later signed a 30-year contract with the new Great Lakes Water Authority (GLWA) on November 22, 2017.