Geochemistry and sources of fluoride and nitrate contamination of groundwater in Lar area, south Iran

Abstract

Groundwater quality in bone-dry and semiarid areas of Iran is decreasing because of contaminants from natural origins and anthropogenic sources. Among many harmful contaminants, nitrate and fluoride ions are more common. This study was carried out with the aim of determining geochemical processes controlling chemistry of groundwater with special reference to nitrate and fluoride enrichment in groundwater in Lar plain aquifer, south of Iran. Groundwater samples were collected from 17 sites and analyzed for main constituents (Na, K, Ca, Mg, Cl, SO, HCO, F, and NO). Composite diagram, saturation indices calculation, and multivariate analysis techniques including cluster and factor analyses were employed in evaluating groundwater quality. The EC ranges from 8793.87 to 13,345.00 μS/cm in wet season and from 9621.59 to 12,640.00 μS/cm in dry season. Fluoride amounts range between 0.59 and 3.92 mg/L. Nitrate concentrations range between 1.47 and 70.66 mg/L. Results indicate that dissolution-precipitation of carbonate and evaporate minerals, evaporation (in terms of agricultural water return), and opposite ion interchange are the main processes that determine groundwater chemistry. It seems that fluoride has a natural origin and the equilibrium reaction between fluorite and calcite is very significant to control fluoride concentration level in water. Vertical variation of nitrate concentration and distribution of agricultural areas have indicated that nitrate originated from nitrogenous inorganic fertilizers used during irrigation periods. The results also indicate that denitrification takes place in the aquifer and that nitrate decline is not only a function of dilution but also a process of denitrification.

Migration behaviour of fluoride in contaminated soils near ammophos production plant: laboratory studies

“…Wanf et al (2002) ranked the fluoride leaching ability of different soils as follows: drab soil > sierozem > black soil > purplish soil > red soil > dark brown earth. According to the findings of Rezaei et al (2017), ion exchange between fluorite and calcite is important in controlling fluoride concentration in water.…”

“…The concentration of water-soluble fluoride in the soils and wash waters was established using a fluorose- (Samofalova and Rogiznaya, 2013). The dynamics of fluoride content in the eluates were statistically processed by regression analysis (Bure, 2007).…”

“…Fluoride is considered a toxic element for plants and animals if found in soils in high concentrations (Rezaei et al, 2017).The main anthropogenic sources of soil pollution by fluoride are plants for the production of aluminum and steel, phosphate fertilizers, and cement and brick factories. Agronomic practices such as irrigation and application of fertilizer also lead to high fluoride content in soil (Brindha et al, 2011), which results in fluoride entering aquifers through natural leaching processes.…”

“…Savasankar et al (2016) reported that at elevated alkalinity, the presence of OH sites in biotite, mica, clay, and similar other minerals is most likely to be replaced with F, and their further dissolution might result in remarkable fluoride concentrations in water sources. Kabata-Pendias and Mukherjee (2007) found that in calcium-rich soils, fluoride reacts with calcium and forms the poorly soluble compound CaF 2 (fluorite); therefore, the calcium geochemical barrier is important for intra-and inter-soil migration of fluoride (Rezaei et al, 2017). Another group of authors reported that alkaline soils have a weak ability to retain fluoride (Kudzin and Pashova, 1970).…”

Data on nitrate and nitrate of Taham dam in Zanjan (Iran)

“…The following equation (Eq. (1) ) was finally used to calculate the non-carcinogenic effects [3] , [4] , [5] : where HI, CDI, and RfD are Hazard Index, Chronic Daily Intake (mg/kg/day), and Reference dose (mg/kg/day), respectively. Also, Eq.…”