Abstract: Purpose
Understanding how copper (Cu) and chloride ions (Cl−) affect metal mobility is increasingly important in the context of climate change and soil degradation and provides deeper insights into soil management and remediation strategies. This study aimed to: (1) understand how the type of soil and its physicochemical properties affect the distribution of Cu in the modified Community Bureau of Reference (BCR) fractions in soils contaminated with copper(II) chloride; (2) to identify the key factors influencing Cu mobility and stability in various types of soils in the presence of high concentrations of
and Cu.; and (3) to develop empirical models for predicting BCR fractions of Cu (FI, FII, FIII+IV) for engineering purposes.
Methods
The BCR sequential extraction method was used to evaluate the mobility of Cu, Zn, Ni, and Pb in 18 soil samples under varying Cu and Cl− ion concentrations, as well as various physicochemical properties. Metal concentrations were determined using the ICP − OES method. Statistical methods were used to investigate how metal type and concentration, chloride (Cl−) concentration, pHKCl, soil-specific surface area (SSSA), organic matter (OM), sand (SA), silt (SIL), clay (CLY) fractions, and particle size (d10, d50) influence the distribution of metal ions within the BCR fractions, and to identify which of these factors are most important in predicting the mobile fraction of Cu.
Results
The mobility of metal ions follows Cu > Pb > Zn > Ni. The BCR chemical fractions are as follows: Cu (FI ≥ FII ≥ FIII > FIV); Zn and Ni (FIV > FIII ≥ FII > FI); Pb (FIII > FIV > FII > FI). As Cu and Cl− concentrations increase, mobile (FI) and potentially mobile (FII) Cu fractions rise, with Cu having a greater effect. FI Cu fractions increase with a decreasing SSSA. ANCOVA confirmed a statistically significant relationship between soil type and Cu in BCR chemical fractions.
Conclusion
There are statistically significant differences in the behavior of mobile and stable BCR metal fractions depending on metal concentrations, soil type (silt loam, silty clay, clay), and soil physicochemical properties, which is crucial for understanding environmental risks in a saline environment. Soils with Cu concentrations above 800 mg/kg dm (dry matter) pose a significant environmental risk, as FI + FII can reach up to 80%. The content of mobile and stable Cu fractions can be predicted using an empirical formula based on total Cu and SSSA.
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