Determination of soluble salts in interstitial water of fluvial sediments by IE-HPLC

Abstract

An ionic exchange high resolution liquid chromatography (IE-HPLC) method for determination of cations and anions in interstitial water of sediments, affluent and effluent of dams is proposed in this paper.

Cations: Na+, Ca2+, K+, and Mg2+ and anions: Cl-, CO32-, NO3- and SO42- were analyzing by IE-HPLC method. Optimized analytical conditions were validated in terms of accuracy, recovery and detection limit. The method of flame spray atomic absorption spectrophotometer (AAS) was used as an additional method for the determination of Ca and Mg. It must be indicated that cations may be analyzed by several analytical methods such as AAS, ICP, etc., but there are not enough methods to analyze anions; IE-HPLC methods are good alternative to determine these ions.

The aim of this study was to determine ions in interstitial water in the affluent and effluent of the Chilean dams Cogotí, Corrales, La Paloma, Rapel and Recoleta in order to determine if the water is suitable for irrigation or human consumption and estimate the effect of dams on water quality. The results indicate that the highest concentrations observed were for the cations: Ca2+ (mean 43.5 mgL-1), Na+ (mean 16.4 mgL-1), Mg2+ (mean 12.6 mgL-1), and K+ (mean 2.3 mgL-1). The highest concentration of anions was found for CO32- (mean 55.9 mgL-1); the concentrations of SO42-, Cl- and NO3- reached 59.3 mgL-1, 12.8 mgL-1 and 27.0 mgL-1, respectively. The results indicate that although the origin of soluble salts is lithogenic, the high concentrations of these salts found in some places indicate anthropogenic effect, either by direct or indirect discharges or by diffuse pollution. These high concentrations may be significant, considering that these waters are used mainly for irrigation, which would affect the quality of agricultural soils irrigated with this moderately saline water.