A palaeo-hydrogeological model for arsenic contamination in southern and south-east Asia.
An argument is presented in which areas of natural arsenic contamination of modern groundwaters throughout Asia have a common origin. Arsenic originally accumulated in oceanic ferro-manganoan sediments of the eastern Palaeo-Tethys. This was further concentrated through oceanic crustal extinction in what later became the south-east Chinese accreted mineralised terrain. Proto-Himalayan uplift of this area created the palaeo-drainage systems of the Ganges - Brahmaputra, Irrawaddy, Mekong, and Red Rivers, with consequent headwater erosion of arsenic-rich sediments. Their downstream deposition as immature and easily redistributed Neogene sandstones, silts, and iron-rich clays has created secondary and tertiary reservoirs of adsorbed and authigenic arsenic, from which the current arsenic-rich groundwaters have evolved. Considering river basins within the above palaeo-hydrogeological framework provides a basis for assessing the risk of arsenic in groundwater basins of south and south-eastern Asia.
Stanger
Gordon
G
UNDP, Box 551, Sanaá, Yemen. hydrodocgeo@yahoo.co.uk
D001151:Arsenic; D001208:Asia; D055593:Geological Phenomena; D005844:Geology; D008962:Models, Theoretical; D014874:Water Pollutants, Chemical; D014881:Water Supply
D014874:Water Pollutants, Chemical; D001151:Arsenic