Multifractal analysis for estimating heavy metal thresholds in Shantou, Guangdong

Environmental assessments typically rely on standard threshold values; however, some heavy metal elements lack national standard values, posing challenges to pollution assessment. Current studies often use background values as substitutes for missing standard values or bypass unstandardized elements in the evaluation, both of which present scientific shortcomings: background values fail to reflect risk levels, whereas bypassing elements may overlook potential hazards. To address these issues, this study focused on the soil in the Shantou area and employed multifractal analysis to estimate the pollution levels of 15 elements, including As, Cd, Cu, Zn, Cr, Pb, Ag, Be, Bi, Co, Mn, Sb, Sc, Ti, and V, and establish their baseline values and risk assessment thresholds. The results demonstrated that multifractal analysis effectively revealed the spatial heterogeneity of heavy metals, particularly for elements with non-normal distributions, offering significant advantages in terms of assessment accuracy and scientific rigor compared with traditional methods. This study not only fills the gap for elements lacking risk screening values but also provides new technical support and a theoretical basis for regional soil pollution management and remediation.