Targeting safe aquifers in regions with high arsenic groundwater and its worldwide implications
THE PROBLEMGeogenic, naturally occurring arsenic is found in the groundwater in Bangladesh and Argentine. Arsenik is a special kind of pollution in the sense that it can be mobilised into the groundwater even if the amount in soils and sediments are not elevated. In Bangladesh it is unfavourable redox-conditions in the form of anaerobic sediments where ferric hydroxides are dissolved and arsenic adsorbed onto these compounds are mobilised to the groundwater. In Argentine it is a high pH which causes the arsenic to be mobilised into the groundwater. Often groundwaters with low concentrations of arsenic occur adjacent to groundwater with hazardous groundwater. Local well-drillers are practically experienced and the aim in this project is to give them simple tools with which they can identify aquifers with safe concentrations of arsenic.HOW CAN THE PROJECT CONTRIBUTE TO A SOLUTION TO THE PROBLEM?
The geochemical conditions leading to mobilisation of arsenic are often manifested in relatively simply observable parameters. In Bangladesh it has been observed that the colour of the sediments, varying from black to orange, mirror the redox-conditions. By correlating the colour with the arsenic concentration in the groundwater it will be possible to provide the well-drillers with a colour-scale enabling them to decide when they have reached an aquifer with acceptable arsenic concentrations. In Argentine it is necessary to use a combination of parameters to achieve the same result.
WHO WILL BENEFIT FROM THE RESULTS?
A large number of wells and borewells are constructed daily and these efforts have to be directed to give a safe water what regards arsenic. The methodology outlined above can in a simple way give the well-drillers a possibility to by existing technology and simple observations give the population a safe water. The water supply both in Bangladesh and in Argentine is based on household wells and the households cannot afford filters, neither do they have time to use and maintain them. Household wells with handpumps give a bacteriologically safe water and is a form of water supply that the population have learnt to appreciate and maintain.
