If you add the valences of each atom in the molecular formula for arsenious acid, H 3 AsO 3, you can see that the molecule, which is uncharged, has a total valence state of 0 (3x(+1) for the hydrogen atoms; 1x(+3) for the arsenic(III) atom; 3x(-2) for the oxygen atoms = 3+3-6 = 0).
Eighty percent of sewage in India is untreated and flows directly into the nation's rivers, polluting the main sources of drinking water, a study by an environment watchdog showed Tuesday.
Though water pollution may occur from a variety of sources, there are two terms used to describe how the water became polluted. When water is polluted from point sources, this is pollution from a discrete location. This discrete location could be a factory, a sewer pipe or a runoff from a single farm. The BP oil spill in 2010 is an example of point source pollution, because the massive amount of oil leaked from a single point of origin.