Environ Monit Assess (2010) 170:345–351 DOI 10.1007/s10661-009-1237-6 Seasonal variations of lead, arsenic, cadmium and aluminium contamination of groundwater in Dhemaji district, Assam, India Mridul Buragohain · Bhabajit Bhuyan · Hari Prasad Sarma Received: 26 May 2009 / Accepted: 29 October 2009 / Published online: 12 November 2009 © Springer Science + Business Media B.V. 2009 Abstract Seasonal variations in the concentra- tions of groundwater with respect to arsenic, lead, cadmium and aluminium has been studied in Dhemaji district of Assam, India. The water sam- ples were collected from 20 different sites in both dry and wet seasons. The metals were analysed by using atomic absorption spectrometer, Perkin Elmer AAnalyst 200 model. The concentrations of aluminium, lead and cadmium in groundwa- ter were found to be significantly elevated. High concentrations of all the metals were recorded in the dry season than in the wet season. Univariate statistics along with skewness, kurtosis and con- fidence limit have been calculated for both the seasons to test the distribution normality for each metal. Statistical analyses of the data reveal non- uniform distribution of the metals in the area. The M. Buragohain Department of Chemistry, Lakhimpur Girls’ College, Lakhimpur, Assam, 787 031, India e-mail: mbg_2007@rediffmail.com B. Bhuyan (B ) Department of Chemistry, North Lakhimpur College, Lakhimpur, Assam, 787 031, India e-mail: bhabajitb@rediffmail.com H. P. Sarma Department of Environmental Science, Gauhati University, Guwahati, Assam, 781 014, India e-mail: hp_sarma@sify.com metal contamination of groundwater in the district follows the trend Al > Pb > Cd > As in both the seasons. Keywords Seasonal variations · Lead · Aluminium · Cadmium · Arsenic Introduction Groundwater has been used for drinking pur- poses for a long time. Because of its purity, a large section of rural population in India depends heavily on groundwater for their domestic and agriculture purposes. It has been observed that metal contamination of groundwater more often than not goes unnoticed and remains hidden from the public view. Several metals are present in groundwater that play important roles in the body provided their level remains within the specified range recommended by the World Health Organ- isation (WHO 2004). Metals in water supply may occur naturally or may be the result of conta- mination. Trace amounts of metals are common in water, and these are normally not harmful to human health. The main threats to human health from heavy metals are associated with exposure to lead, cadmium, mercury and arsenic. These metals have been extensively studied and their effects on human health regularly reviewed by interna- tional bodies such as the WHO (Järup 2003). The