Characterization of soil heavy metals at an abandoned smelting site based on particle size fraction and its implications for remediation strategy

Soil particle size plays a crucial role in the distribution and occurrence of soil heavy metals (HMs). Comparative studies on the distribution of HMs across soil particle sizes of various areas affected by smelting are scarce. Three soil profiles, including smelting slag heap (SH), traffic area (TA), and adjacent farmland (FA), were sampled at an abandoned Pb smelting site, and the geochemical distribution and occurrence of HMs in different soil particle fractions (>150 µm, 45 −150 µm, and <45 µm) were comparatively investigated. Results showed different distribution of HMs across soil fractions between the smelting site and farmland. Average accumulation factors (F_A) of HMs increased from 0.78 to 1.14 as the particle size increased in the SH related to the stockpiling and mechanical mixing of coarse slags, while decreased from 1.49 to 0.60 in the FA related to metal-enriched fine particles released from smelting. The coarser fraction had a higher mass loading of HMs (>50%) in the smelting site soils, where the contribution of waste residues was significant. Therefore, physical separation techniques are recommended in the remediation of soil contamination. The study connected smelting impacts and occurrence of HMs across particle sizes which has implications for remediation strategy.