RESUMO
One of the problems in urban areas is nitrate contamination of ground waters. High nitrate concentration can cause methemoglobinemia, appearing as a risk factor is provided by ground waters. More than 80% of drinking water of Gorgan, Iran. So this investigation was done to determine of nitrate level in ground waters in Gorgan. This study has been carried out for investigation of nitrate rate in drinking water supply networks and not drinking water ground water wells of Gorgan city. This discriptive study was done on 43 ground waters and surface water samples which collected in spring and winter, in Gorgan during 2005. K+, Cl-, NO21-, NO31- of samples were analyzed by spectrophotometery method. The chemical analysis of ground waters of drinking water resources of Gorgan city showed significant variation of nitrate between 3.52 to 69.52 mg/l. The rates of nitrate in certain ground waters wells in vicinity of landfills were between 84.48 to 145.2 mg/l which is more than drinking water standards. Nitrate concentration in agricultural lands such as Shast-kula and Garmabdasht aquifers is lower than Ziarate aquifer in vicinity of urban area. Nitrate contamination in aquifers in vicinity of urban area and unsanitary disposal of solid waste substance may result from house sewage effluents and infiltration of landfillleachs to ground water wells