Bioaccessibility of Metal(loid)s From Anthropogenic Contamination in Dry Riverbed Sediments in the Cartagena–La Unión Mining District (Murcia, SE Spain): Implications for Human Health Risk Assessment

ABSTRACT

This study assessed the contamination levels, bioaccessibility, and potential health risks of As, Cd, Cu, Pb, and Zn in sediments from three dry riverbeds (El Beal‐EB, Las Matildes‐LM, and Ponce‐PN) impacted by historical mining activities in the Cartagena‐La Unión Mining District. Sediment samples (20 samples from EB, 13 samples from LM, and 19 samples from PN) were collected and analyzed for total and bioaccessible metal(loid) concentrations, and physicochemical properties. Spatial distribution for the contamination factor (Cf), pollution load index (PLI), and correlation analyses were employed to evaluate sediment pollution status. Bioaccessibility was determined using the Solubility Bioaccessibility Research Consortium (SBRC) method. Human health risks were assessed using hazard quotients (HQ) and carcinogenic risk (CR) for children, considering total (scenario 1) and bioaccessible (scenario 2) concentrations. The PLI indicated severe contamination, with maximum values of 66, 78, and 80 for EB, LM, and PN, respectively. Bioaccessible fractions varied widely across all metals and sites, ranging from 0.04% for As to 98.4% for Cd in Las Matildes; in El Beal, Pb bioaccessibility varied between 22.0% and 92.1%, while in Ponce, Pb bioaccessibility ranged from 5.6% to 96.3%. In addition, PN exhibited that pH and inorganic carbon collectively govern metal(loid) bioaccessibility, with strongly acidic conditions enhancing the solubility of Cd, Pb, and Zn. The correlations between total and bioaccessible metal(loid) concentrations were strong and significant in EB‐PN, but no correlation in LM was found, emphasizing the importance of site‐specific geochemical factors in assessing human health risks. Health risk assessments revealed that total Pb concentration posed the highest non‐carcinogenic risk (non‐carcinogenic risk was considered significant when HQ > 1), with HQ reaching a mean value of 2.43 in LM and 1.09 in EB. However, when non‐carcinogenic risk was evaluated via bioaccessible fraction, mean HQ values decreased by 58% for Pb, remained above the safety threshold (HQ > 1) in specific samples. Additionally, total As concentrations contributed to carcinogenic risk, with values exceeding the threshold (CR > 10 ⁻⁵ ) across the riverbeds. However, when bioaccessible concentrations were considered, carcinogenic risk was substantially reduced (CR < 10 ⁻⁵ ), indicating no significant carcinogenic risk. This study highlights the importance of considering bioaccessibility in risk assessment studies of mining‐impacted areas.