Groundwater quality and contamination index mapping in Changchun City, China

Groundwater in Changchun City, Jilin Province of China tends to be influenced by human activities. Chemical types of groundwater were detected in both shallow and deep groundwater were: HCO3- Ca2+ and HCO3- - Ca2+ · Mg2+ or HCO3- - Mg2+ - Ca2+; SO42- - Ca2+ and SO42+; - Ca2+ · Mg2+; Cl- - Ca2+; and CO32- - Na+. The deteriorations of groundwater quality due to the increase of TDS, NO3- + NO2- (as Nitrogen) and TH contents have been observed from 1991 to 1998. Scatter analyses showed strong positive correlations between Ca2+, Cl- and NO3- ions and weak negative correlations between the depth of water table and Ca2+, SO42-, Cl- and NO3-ions. A mapping of contaminant index based on Chinese standard of groundwater showed that a large proportion of the groundwater in 1998 was deteriorated by human process. Despite their low values of sodium adsorption ratio (SAR), the most of the sampled wells were not suitable for drinking and agriculture purposes due to higher contents of NO3-, NO2- and Mn2+ ions.