In other words, arsenic cannot be detected by looking at water, or even by placing water under a microscope. Measuring arsenic is a complex process that requires specialised equipment under controlled conditions. These arsenic-bearing sediments became buried over thousands of years, forming part of the aquifers that are tapped today for water sources. In this process, arsenic is adsorbed into fine-grained iron or manganese oxyhydroxides which are present in sediments. As time passes, oxygen levels naturally decrease and under these conditions, the iron and manganese compounds dissolve and release the arsenic into the surrounding water.
Geologists cite several other processes by which arsenic can be released into ground water.
These compounds dissolve upon contact with oxygen, releasing iron, sulfide, and arsenic into the surrounding water. Since there is little or no sulfide in ground water in Bangladesh, this process is not regarded as a widespread occurrence in this country. The greater Sylhet area is also affected. Isolated cases of arsenic contamination have been found in the northern and coastal areas of the country. There is a need to know much more about the impact of arsenic poisoning.