Survey on Arsenic and Iron Contamination in Groundwater in Blocks of North Bank Plain Zone of Assam

Abstract

Arsenic contamination in groundwater and its impact on human health has been reported as one of the world's biggest natural groundwater calamities to the mankind. In Assam, Arsenic concentration in groundwater above the permissible level has been reported from 20 districts, of which, maximum level of Arsenic concentration was found in Jorhat, Lakhimpur, Nalbari and Nagaon districts. In the present study Arsenic and Iron contamination of groundwater in Narayanpur Block and Sakhomato Block of North Bank Plain Zone of Assam was determined. Eighty seven numbers of ground water samples from Narayanpur Block and forty seven numbers from Sakhomato Block were collected from tubewells (15 feet to 75 feet deep) at different locations of the Blocks. The Arsenic content of analyzed samples from Narayanpur Block varied from 0 (zero) ppb to 102 ppb, of which, 48 (55.17%) samples were found below the WHO guideline value for drinking (less than 10 ppb); while 39 (44.83%) samples contained Arsenic above the guideline value (more than 10 ppb, WHO, 2011). In case of Sakhomato Block, all the 47 samples contain Arsenic below the critical limit of 10 ppb and hence found safe for drinking. Iron concentration of the samples having Arsenic concentration above the critical limit of 10 ppb from Narayanpur Block was analyzed with a view to ameliorating Arsenic toxicity through removal of Iron. The Iron concentration of the samples ranged from 10 ppm to 58.4 ppm. However, no significant correlation between Iron and Arsenic concentration was observed (r2=0.0403).