Published in Proceedings of National seminar on Hydrology with focal theme on “Water Quality” held at National Institute of Hydrology, Roorkee during Nov 22-23, 2004.
Arsenic Contamination in Groundwater of North Eastern India A.K. Singh Associate Professor and Adviser (Soil & Water Testing Lab & Microbiology Lab) North Eastern Regional Institute of Water and Land Management Tezpur-784027, Assam (India)
[email protected]/@rediffmail.com/@sancharnet.in Abstract Groundwater arsenic contamination and sufferings of people have been reported in 20 countries in different parts of the world. The magnitude is considered highest in five Asian countries and the severity is in order of Bangladesh>India>Mangolia>China>Taiwan. In all these countries, more and more groundwater withdrawal is taking place because of increase in agricultural irrigation. In India after West Bengal and the bordering districts of Bangladesh, arsenic in groundwater was detected in part of Assam, Arunachal Pradesh, Manipur, Nagaland and Tripura. Maximum arsenic content was observed in Jorhat (Titabor, Dhakgorah, Selenghat and Moriani Block), Dhemaji (Sissiborgoan and Dhemaji Block), Golaghat district (Podumani Block) and Lakhimpur (Boginodi, Lakhimpur Block) in Assam; West Tripura (Triania Block), Dhalai (Salema Block) and North Tripura (Dharmanagar Block) districts in Tripura, Thuobal (Kakching Block) in Manipur and Dibang valley (Midland) in Arunachal Pradesh. The groundwater of these blocks of five states is affected with arsenic contamination. A long-term environmental planning is essential to blunt the danger from such pollution. Introduction In the North Eastern region of India, natural springs and dug wells are the only cost effective and viable means of fulfilling the needs of freshwater for present population. In hilly areas, most of the drinking water is used to be harnessed from rivers, ponds and natural springs. Many springs are reportedly becoming seasonal. In valleys, most of the domestic water is harnessed from groundwater through shallow tubewells and dug wells. Availability of drinking water in summers is severely marred and the overall quality is questionable. Information on groundwater quality of North Eastern India is scanty. Available literature shows that groundwater of Assam valleys are highly ferruginous (Aowal 1981). The incidence of high fluoride in groundwater of Karbi Anglong and Nagoan district of Assam and its manifestation in the form of fluorosis were already (Akoijan 1997, Sengupta, 1999, Sushella 2001) reported. These alarming pictures of the water quality in the region and continuous consumption of this water has the potential of posing serious health hazard to the local population. The observation warrants an extensive and exhaustive study to identify the
contamination sites both from the standpoint of protecting public health and preserving the natural resources. Recognizing the enormity and severity of the problem, groundwater quality survey was conducted for the entire north eastern region to identify the suitability or otherwise of groundwater quality for drinking purposes. Under this project, random samples of water were collected from various states in the region. It was observed from the analysis of the samples that arsenic, iron and fluoride contamination in predominant in few of the states of NE Region. No study was conducted earlier to explore the presence of arsenic in groundwater of North Eastern India. This paper reports the present status of the arsenic in groundwater of NE Region. Material and Methods The ground water samples were drawn from both bore wells and open wells (up to 120ft) during post-monsoon period of year 2003 from 1500 location in Assam, 296 locations in Arunachal Pradesh, 182 locations in Meghalaya, 132 locations in Nagaland, 128 locations in Sikkim, 117 locations in Tripura, 114 locations in Mizoram, and 60 locations in Manipur covering entire north eastern region. Tube wells were operated at least 10 minutes before collection to flash out the stagnant water inside the tube and to get fresh ground water. The water samples were collected in plastic container (PVC 1L) and sealed. Preservative (1:1 HNO3 solution to pH
