Assessment of groundwater quality in Jajrood basin, Tehran, Iran: A coupled physicochemical and hydrogeochemical study

The physicochemical composition of groundwater are affected by the quantity and quality of surrounding aquifers which are in turn recharging from adjacent river waters. In the present study, 20 surface and 16 groundwater samples were collected in pre- and post-monsoon seasons from Jajrood river basin, Tehran, Iran. The samples were analyzed for totally 18 physicochemical water quality characteristics to assess the river and groundwater qualities. Hydrogeochemical analyses of groundwater samples were also performed to determine the water quality index (WQI) for drinking use and to evaluate factors governing the water quality characteristic in the study area. Accordingly, Piper diagram as well as Gibbs and Chadha’s plots were applied to assess seasonal variations in hydrochemical facies and to evolve the hydrochemical processes in the basin. Sub – surface soil samples were also examined with respect to the structure, elemental composition and multi- elemental trace analysis. Results showed the abundance of major ions in the order of Ca+2 > Na+ > Mg+2 > K+, and HCO3- > SO42- > Cl- > NO3- > F-. In general, all drinking groundwater samples met WHO permissible limits except for chemical oxygen demand (COD) and HCO3-. Moreover, the water is categorized as Ca-Mg-HCO3 type. Sub surface soil analyses demonstrated quartz and calcium carbonate as the main phases of soil structure suggesting the enrichment of groundwater with temporary hardness. Overall, the groundwater quality was suitable for drinking uses and agricultural activities.