CS(AR)-26/97-98 : Ground water quality monitoring and evaluation in and around Greater Guwahati (Assam) Part-III: Trace elements

Abstract

Toxicity of a metal depends on its concentration, which adversely affects any biological activity. Almost all the metals are toxic at higher concentration; few of them are toxic in low quantity but few others are toxic even in trace e.g. As, Pb, Hg, Cd etc. The presence of such metals in groundwater is a subject of serious concern. Groundwater which contains higher amount of metals and large or trace quantity of toxic metals, affects public health to a great extent when it is used for drinking and domestic purposes. The impact of trace elements in drinking water is generally cumulative, by which the prolonged use of such waters is dangerous for health. Hence the measurement of trace elements concentration and analysis of their periodicity of fluctuation and trend is necessary.

The present work deals with the detection of trace elements viz. Pb, Cu, Co, Cd, Zn, Fe, Mn and Ni in ground water of Guwahati and its adjacent areas. In the present study, ground water samples were collected from 29 dug wells using grid network pattern and quality was compared with the standards laid by WHO, Bureau of Indian Standards (BIS) and Indian Council of Medical Research (ICMR) with respect to trace elements content in the ground water. Study revealed that the concentrations of Fe, Zn, Cd and Mn crossed the maximum permissible limits of WHO in most of the sites and are in alarming condition. Lead (Pb) was found absent from all the sampling sites, while concentration of Cu, Co and Ni are well within the maximum permissible limit of WHO. The maximum concentration of Cu, Co, Cd, Zn, Fe, Mn and Ni were recorded as 0.018, 0.101, 0.015, 24.175, 4.805, 7.325 and 0.330 respectively. By taking the advantage of equal grid network pattern of sampling for different sites, thematic maps have also been prepared. ORP and pH were also measured to see the stability field of iron in pH-ORP diagram.