Properties of water equal to that of the hydrogen ion (), which gives a pH of 7 at 25 °C. Action of water on rock over long periods of time typically leads to weathering and water erosion, physical processes that convert solid rocks and minerals into soil and sediment, but under some conditions chemical reactions with water occur as well, resulting in metasomatism or mineral hydration, a type of chemical alteration of a rock which produces clay minerals. It also occurs when Portland cement hardens. Water ice can form clathrate compounds, known as clathrate hydrates, with a variety of small molecules that can
Drinking water quality in the United States for 53 organic compounds, including benzene, dioxin (2,3,7,8-TCDD), PCBs, styrene, toluene, vinyl chloride and several pesticides. EPA has issued standards for alpha particles, beta particles and photon emitters, radium and uranium. EPA maintains the "Contaminant Candidate List" (CCL), a list of substances which are being considered for possible regulation in the drinking water program. In an effort to assess the importance of certain substances as contaminants, the National Primary Drinking Water Regulations have required some public water systems to monitor for some of those substances. Perfluorooctanoic acid (PFOA) is a synthetic perfluorinated carboxylic acid and fluorosurfactant. It has been used