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
Regulation of pesticides in the European Union be used as a pesticide in the EU. The concentrations of pesticides alongside other chemical substances that pose a significant risk to the environment or to human health in surface waters in the European Union are limited to Environmental Quality Standards. These are defined in the Directive on Environmental Quality Standards in the Field of Water Policy. This Directive covers a total of 45 priority substances as defined by the Water Framework Directive and 8 additional pollutants. Environmental Quality Standards set limits to the average annual concentration as well as the maximum allowable concentrations for short-term exposure and differentiates inland