Groundwater quality in an irrigated, agricultural area of northern Malayer, western Iran

Abstract

The monitoring of water quality is an important tool for sustainable development and provides important information for water management. Forty-eight groundwater samples were collected from northern Malayer, western Iran, to assess their nutrient status. Seventy-five percent of the water samples showed nitrate (${\text{NO}}^{ - }_{{\text{3}}}$) concentrations above the human-affected value (13 mg l^–1 ${\text{NO}}^{ - }_{{\text{3}}}$), while more than 12.5% exceeded the maximum acceptable level (50 mg l^–1 ${\text{NO}}^{ - }_{{\text{3}}}$) according to World Health Organization (WHO) regulations. The samples were classified into four groups based on chloride (Cl⁻) and ${\text{NO}}^{ - }_{{\text{3}}}$ concentrations. Several factors indicated that the ${\text{NO}}^{ - }_{{\text{3}}}$ and some Cl⁻ were derived from agricultural sources. The correlation between ${\text{NO}}^{ - }_{{\text{3}}}$ and Cl⁻ was consistent with a manure source, due to the practice of adding salt to animal feed, and suggests that denitrification is not appreciable at most locations. The aquifer plays a role in the decrease of contamination risk from phosphorous (P) through the high calcium (Ca²⁺) ion concentrations that cause P to precipitate. The relatively low levels of potassium (K⁺) in groundwaters may be a consequence of its tendency to be fixed by clay minerals. Pollution of groundwaters appeared to be affected by the application of fertilizers, irrigation practice, the solubility of mineral phases, and the discharge of domestic sewage. Application of high ${\text{NO}}^{ - }_{{\text{3}}}$ groundwater irrigation can minimize the requirement for inorganic fertilizers and reduce the cost of cultivation.