An investigation on the impacts of chemical fertilizer on aquifer of Hashtgerd plateau

Hashtgerd field (area: 650 Km2) is located in Tehran province which include mountainous region in south of central Arborz, alluvium area in west of Karaj field and east of Qazvin field. Hashtgerd field’s climate is cold and dry.
The samples were collected from 18 wells in winter (1387) and spring (1388) and analyzed for the amount of nitrate, phosphate and potassium in samples.
Extra uses of nitrate fertilizer cause the rise of nitrate through out the valley. The most amount of nitrate was observed in north east of Hashtgerd valley (19 mg/L) that was upper than standard amount (10 mg/L). Considering the movement direction of underground water in Hashtgerd field (from the north east to south west) the main resource of nitrate increase is the use of chemical fertilizer in agricultural activities.
Although the most amount of phosphorus was in south west of Hashtgerd field (1.5 mg/L), it was less than standard amount (2 mg/L). Despite the low movement of phosphate in soil, it penetrated in to underground water. The main reason was the movement direction of underground water, up level of underground water and lack of unsaturated layer. Phosphorus of fertilizer enters the underground water and cause pollution.
The amount of potassium in most of the wells was about 0.39- 1.96 (mg/L) that was lower than standard amount (2 mg/L). The most amount of potassium was in east north of the field to aquifer is predictable, because of the washing effect.