Introduction: Incheh Wetland, located in northeastern Iran, is adjacent to iodine extraction plants and has received effluent from these industrial facilities since 2008. The 2018 multielement dataset, comprising magnesium (Mg), cobalt (Co), cerium (Ce), manganese (Mn), strontium (Sr), sulfur (S), and barium (Ba), had not previously been comprehensively analyzed. This study aimed to characterize the spatial distribution of these elements, distinguish geogenic background contributions from potential anthropogenic inputs, and compare the findings with independent results reported for 2023–2024.
Materials and Methods: This study reanalyzed raw data from samples collected in November 2018. The dataset comprised 21 sediment samples from seven wetland stations and eight water samples collected within the wetland and from the iodine plant's discharge channel. Elemental analyses involved inductively coupled plasma mass spectrometry (ICP-MS) and elemental analysis. Statistical analyses included Spearman's rank correlation, the Kruskal–Wallis test, and principal component analysis (PCA) to evaluate element associations, spatial variability, and potential geochemical controls.
Results: Mean water concentrations of Mg and Mn were 2212.9 mg/L and 365.3 μg/L, respectively, while mean Ba concentration at stations within the wetland was 2384.1 ± 316.6 μg/L. Sr concentrations in all water samples and Ba at discharge-channel station K8 exceeded the analytical reporting limit (>100,000 μg/L), preventing precise quantification. Comparison with an independent study conducted in 2023–2024 showed Mn concentrations of 2.25–3.89 mg/L, compared with 0.365 mg/L in 2018, representing an approximately 6- to 10-fold difference. This contrast may indicate a change in water quality, although differences in sampling design and analytical methods limit definitive temporal interpretation.
Mean sediment concentrations were 1339 mg/kg for Ba, 4080 mg/kg for Sr, 0.646% for S, 14.3 mg/kg for Co, 245.8 mg/kg for Mn, 1.585% for Mg, and 11.40 mg/kg for Ce. Sediments were predominantly silt loam, with a mean total organic matter (TOM) content of 10.48%. Co, Mn, Mg, and Ce were positively correlated with Al (Spearman's ρ = 0.75–0.90) and clay content. These elements loaded on the first principal component (PC1), explaining 52.39% of the total variance, suggesting associations with geogenic background and fine-grained sediment characteristics.
In contrast, Ba showed no significant correlation with Al and reached 4796.8 mg/kg at station K5 near the discharge channel, approximately 7.3 times the reported crustal concentration. This localized maximum may indicate an additional source. Sulfur displayed a contrasting spatial pattern, with a maximum of 1.803% at K2 and a minimum of 0.120% at K5. Sr was negatively correlated with Al (ρ = −0.681) and loaded on PC3, explaining 11.83% of the variance, suggesting potentially different geochemical controls.
Discussion: Co, Mn, Mg, and Ce generally exhibited patterns consistent with association with Al and fine-grained sediments, whereas Ba and S showed distinct spatial distributions and Sr behaved differently. The elevated sediment Ba concentration near the discharge channel, combined with the pronounced Ba anomaly in channel water, provides the strongest independent geochemical indication in the 2018 dataset of a possible influence from iodine-industry activities. Nevertheless, these findings do not establish definitive source attribution. Direct effluent sampling, transect-based and seasonal monitoring, sulfur speciation, and isotopic analyses are required to distinguish industrial inputs from natural geochemical processes. The study establishes a historical multielement baseline to guide future monitoring and environmental management of Incheh Wetland.