Biogeochemical Assessment of Some Heavy Metal Contamination in Soil and Indicator Plant (Helichrysum arenarium) in Bitlis Region, Eastern Türkiye

This study presents a detailed biogeochemical assessment of heavy metal contamination in surface soils and the leaves of the native herb Helichrysum arenarium across Bitlis Province, Eastern Türkiye. Thirty-eight paired soil and leaf samples were collected from 19 georeferenced locations spanning urban, agricultural, and relatively undisturbed settings. Soils were air-dried, sieved (<2 mm), and analyzed for pH, electrical conductivity, and total concentrations of Fe, Zn, Mn, Cu, Pb, Co, Ni, Cr, and Cd by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Corresponding leaf tissues underwent acid digestion and ICP-MS analysis to quantify foliar metal burdens. Leaf–soil bioconcentration factors (BCF = [metal]leaf/[metal]soil) were calculated to evaluate the bioindicator potential of H. arenarium . Soil concentrations of Fe (12 000–58 000 mg kg⁻¹), Zn (65–280 mg kg⁻¹), and Mn (450–1 200 mg kg⁻¹) frequently exceeded regional background levels, particularly in roadside and irrigated agricultural plots. ICP-MS analyses revealed mean concentrations of Fe and Zn of 1 780 ± 315 mg kg⁻¹ and 60.4 ± 14.8 mg kg⁻¹, respectively, with BCF values for these elements (BCF-Fe = 0.15–0.22; BCF-Zn = 0.20–0.27) indicating moderate accumulation that closely mirrored soil contamination gradients. ICP-MS analyses revealed mean concentrations of Fe and Zn of 1 780 ± 315 mg kg⁻¹ and 60.4 ± 14.8 mg kg⁻¹, respectively, with BCF values for these elements (BCF-Fe = 0.15–0.22; BCF-Zn = 0.20–0.27) indicating moderate accumulation that closely mirrored soil contamination gradients. Copper concentrations averaged 9.8 ± 4.1 mg kg⁻¹, with BCF values exceeding 10 at several sites, indicating strong but inconsistent accumulation patterns that were not consistently correlated with soil Cu concentrations. In contrast, BCFs for Pb, Cd, and Co remained low (< 0.05), reflecting limited uptake of these more strongly adsorbed metals. Analysis of variance (ANOVA, p < 0.05) confirmed significant spatial variability in both soil contamination and foliar accumulation, which correlated with proximity to major transport routes and intensively managed fields. Although H. arenarium does not meet hyperaccumulator criteria, its reproducible foliar responses to soil Fe and Zn levels underscore its suitability as a bioindicator species in semi-arid volcanic terrains. It is recommended that H. arenarium leaf analyses be incorporated into routine environmental-monitoring protocols—alongside periodic soil testing—to efficiently map localized heavy metal hotspots. Future investigations should examine seasonal dynamics of metal bioavailability and extend sampling to additional plant organs, thereby enhancing ecological risk assessments for agricultural production and grazing ecosystems in the Bitlis region.