The Influence of Age and Management on Soil Physicochemical Properties and Heavy Metal Accumulation in Post-Tin Mining Lands on Bangka Island

Bangka Island is one of the largest tin producers in Indonesia and the world, covering an area of 156,531.3 hectares. Tin mining activities have significantly degraded post-mining land, altering soil properties and increasing heavy metal retention. This study aimed to evaluate the impact of post-tin mining land age and management on soil physical and chemical properties and total heavy metal concentration. Soil samples were collected using a stratified sampling method from three representative sites with similar climatic conditions: newly mined land (0 years), reclaimed land (7 years), and minimally managed land (20 years). Physical parameters were measured directly in the field, except for bulk density, air-dried soil moisture, and texture fraction, which were analysed in the laboratory alongside chemical parameters. The findings indicate that as post-tin mining land ages, soil physical properties such as bulk density, soil hardness, air-dried soil moisture, and texture fractions change, while infiltration decreases, indicating compaction. Meanwhile, post-tin mining management in the form of reclamation significantly improves soil chemical quality, including pH, organic carbon, organic matter, and phosphorus availability. Heavy metal accumulation is more strongly influenced by land age than management practices; however, appropriate management can reduce heavy metal availability and enhance overall soil quality. Partial least squares structural equation modeling (PLS-SEM) analysis confirms that soil physicochemical properties mediate the relationship between land age, management, and heavy metal accumulation in post-tin mining sites.