Evaluation of groundwater quality in Dayyer city Bushehr using groundwater quality index (GQI)

Background and objective: In this study, groundwater resources of Dayyer city in Bushehr province were investigated for the amount of different parameters. The use of nitrate fertilizers in the city of Dayyer and the diversion of agricultural effluents containing these compounds to water sources has increased the concentration of nitrate. Calculation of ion ratios showed that weathering was delayed in the aquifers of the city and the infiltration of salt water led to an increase in the concentration of chloride and sodium. The increase in the concentration of other ions, such as calcium and magnesium, has a geological origin.Materials and methods: For this purpose, in three stages (October, November and December ۲۰۱۹), ۷ wells located in this city were sampled and the amount of various parameters including electrical conductivity, pH, hardness, total alkalinity, total soluble solids, nitrate concentration, sulfate, Nitrite, chloride, calcium, magnesium, sodium, potassium, fluoride, iron and bicarbonate were determined using standard methods.Results and conclusion: The results were analyzed using one-way analysis of variance and ArcGIS software was used to prepare zoning maps by kriging method. Nitrate and sulfate concentration parameters, electrical conductivity, total soluble solids, total hardness, chloride, calcium, magnesium, sodium, potassium, fluoride and bicarbonate concentrations are ۱۷.۹-۵۶.۴ and ۱۱۰۰-۳۸۰۰ mg/l, respectively, ۳۷۴۰-۷۴۶۰ micro siemens per centimeter, ۲۲۴۰-۴۴۸۰, ۲۸۲۸-۱۳۹۳.۸, ۶۳۵.۲۶-۲۰۳۴.۸۳, ۳۱۵.۱۲-۶۳۰.۲۴, ۱۴۵.۴۴-۳۴۹.۰۵۶, ۲۷۴.۱۹-۱۰۶۸.۱, ۱۳-۲۰, ۳.۱۲-۳.۸, and ۶۸.۳۲-۱۳۱.۷۶ mg/l were obtained. The results showed that except for the parameters of iron concentration (۰.۰۳-۰.۰۵ mg /l) and nitrite (۰.۰۰۹۹-۰.۰۳.۶۳ mg /l) and pH (۷.۱۳-۷.۳۴), The value of the other parameters is too much. Sulfate concentration has increased due to oxidation of pyrite-containing soils and the presence of evaporative minerals such as gypsum. According to the results obtained from the measurement of groundwater quality index, the value of this index is between ۵۱ to ۶۱, which means the average quality of water resources in this city.