Abstract
To evaluate the effect of in situ chemical remediation on copper (Cu) immobilisation and migration, in situ chemically remediated soils from a smelter-impacted field were partitioned into four aggregate size fractions and their Cu adsorption characteristics were investigated. The results indicate that the highest Cu concentration occurred in the <0.053 mm size fraction, while the highest Cu mass loading was obtained in the 0.25–2 mm size fraction (39.9–42.5%). However, in situ remediation increased the Cu mass loading levels in the >0.25 mm aggregates. A pseudo-second-order model was used to fit the adsorption process obtained in kinetic experiments, while the data from isothermal experiments were described using the Freundlich model. The fastest adsorption rate was observed in the <0.053 mm fraction, and the adsorption capacity of the soil aggregates improved after combined in situ remediation. The amount of Cu2+ adsorbed increased with increasing pH. The <0.053 mm fraction exhibited lower desorption compared with the other fractions at low pH values. In addition, all particle size aggregates treated with apatite and Elsholtzia splendens had the lowest desorption rates at different pH values.
Highlights
Due to rapid industrial and agricultural development, heavy metals can enter the soil in large quantities through agricultural activity, atmospheric sedimentation, and wastewater irrigation, among others
Plant growth might be achieved by increasing the amount of litter and fine roots, and by changing the structures of soil aggregates, which further leads to increases in Soil organic carbon (SOC) content (Pez-Bellido et al, 2010; Li et al, 2017)
2 mm, and 0.053–0.25 mm size fractions (Figure 1A) The Cu concentrations in both the >2 mm and 0.25–2 mm size fractions followed the order of soda residue > apatite > lime > control, while the Cu concentrations in both the 0.053–0.25 mm and soda residue > lime > control
Summary
Due to rapid industrial and agricultural development, heavy metals can enter the soil in large quantities through agricultural activity, atmospheric sedimentation, and wastewater irrigation, among others. Heavy metals that accumulate in the soil reduce the soil quality, its microbial activity, and crop yields, and threaten ecosystem security and human health (Zhang et al, 2015). Researchers have conducted a variety of studies to develop practices that solve the problem of soil heavy metal pollution, including bioremediation and integrated remediation. The combined use of plant-based and chemical additives for in situ remediation is one of the most inexpensive and effective methods for remediating soils contaminated by heavy metals (Xu et al, 2020; Li et al, 2021). Chemical remediation mainly involves the addition of low toxicity or Remediation Effects on Aggregate Adsorption–Desorption pH
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