Feasibility of Using Biomarkers for Assessing Heavy-Metal Contamination in Soil: A Meta-Analysis

Soil contamination by heavy metals represents a critical environmental challenge, demanding reliable assessment methods. While biotoxicity assays are widely employed, the selection of sensitive biomarkers for heavy-metal contamination remains poorly defined. This study systematically assessed the sensitivity of biological indicators by analyzing 17 peer-reviewed studies (2003–2024) from various databases. The results revealed significant changes in the physiological and biochemical indicators of soil organisms exposed to heavy metals. Specifically, compared to control groups, the experimental groups showed 180%, 150%, and 145% catalase (CAT), peroxidase (POD), and malondialdehyde (MDA) concentrations, respectively. Meta-regression analysis indicated that biomarker responses are shaped by metal type, concentration, exposure duration, soil organism species, and soil variables. Cadmium exposure significantly increased CAT activity (+2.26), SOD activity (+3.46), POD activity (+3.44), and MDA content (+2.80). While CAT activity exhibited significant publication bias, POD and MDA remain promising biomarkers, with applicability varying across species and environmental conditions. This study presents a decision framework for biomarker selection based on metal speciation and soil properties, aiming to standardize ecological risk assessments and strengthen regulatory monitoring of heavy-metal impacts on soil health.