Material-Based Assessment of Iron and Manganese Distribution in River Water by Atomic Absorption Spectrophotometry

Abstract

River water is a widely used source of surface water whose quality requires regular monitoring, particularly for iron (Fe) and manganese (Mn) concentrations, which originate from natural weathering and anthropogenic activities. This study aimed to determine Fe and Mn concentrations in upstream and downstream river water samples using Atomic Absorption Spectrophotometry (AAS) in accordance with SNI 6989.84:2019, to evaluate the reliability of the results through laboratory quality control parameters, and to compare the measured concentrations with the national river water quality standard under Government Regulation No. 22 of 2021. Upstream and downstream samples, together with a laboratory control sample (LCS), a procedural blank, spiked samples, and a certified reference material (CRM), were digested with nitric acid (HNO₃) and analyzed using flame AAS. The Fe and Mn calibration curves showed coefficients of determination (R²) of 0.9978 and 0.9971, respectively, both exceeding the SNI 6989.84:2019 acceptance criterion of R² ≥ 0.995, and quality control samples met laboratory acceptance criteria. Fe concentrations ranged from 0.1557–0.1594 mg/L upstream and 0.4588–0.4638 mg/L downstream, while Mn was not detected upstream and ranged from 0.5882–0.5915 mg/L downstream. Upstream water met the Class I standard for both parameters, whereas downstream concentrations of both Fe and Mn exceeded the standard. Fe and Mn concentrations increased markedly from upstream to downstream, most plausibly reflecting anthropogenic activities downstream, indicating that downstream water quality requires closer environmental management attention.