Rezaei Mohsen, Nikbakht Masume, Shakeri Ata
Department of Applied Geology, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran.
Environ Sci Pollut Res Int. 2017 Jun;24(18):15471-15487. doi: 10.1007/s11356-017-9108-0. Epub 2017 May 16.
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.
由于来自自然源和人为源的污染物，伊朗干旱和半干旱地区的地下水质量正在下降。在许多有害污染物中，硝酸根离子和氟离子更为常见。本研究旨在确定控制地下水化学性质的地球化学过程，特别关注伊朗南部拉尔平原含水层地下水中硝酸盐和氟的富集情况。从17个地点采集了地下水样本，并分析了主要成分（钠、钾、钙、镁、氯、硫酸根、碳酸氢根、氟和硝酸根）。采用综合图表、饱和指数计算以及包括聚类分析和因子分析在内的多变量分析技术来评估地下水质量。雨季时电导率范围为8793.87至13345.00μS/cm，旱季时为9621.59至12640.00μS/cm。氟含量在0.59至3.92mg/L之间。硝酸盐浓度在1.47至70.66mg/L之间。结果表明，碳酸盐和蒸发岩矿物的溶解-沉淀、蒸发（就农业回水而言）以及反向离子交换是决定地下水化学性质的主要过程。氟似乎有自然来源，萤石和方解石之间的平衡反应对于控制水中氟浓度水平非常重要。硝酸盐浓度的垂直变化和农业区域的分布表明，硝酸盐源自灌溉期间使用的含氮无机肥料。结果还表明，含水层中发生了反硝化作用，硝酸盐的减少不仅是稀释的作用，也是反硝化过程。
