Effects of Soil Amendments Applied on Cd and Pb Immobilization and Environmental Risks under Simulated Acid Rain
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Nanjing Xiaozhuang University, Nanjing 211171, Peoples’ Republic of China
Di Zhang   

Nanjing Xiaozhuang University, China
Submission date: 2021-12-01
Final revision date: 2022-04-04
Acceptance date: 2022-05-03
Online publication date: 2022-07-26
Publication date: 2022-09-28
Pol. J. Environ. Stud. 2022;31(5):4953–4963
A column leaching experiment was conducted to study the long-term remediation stability of hydroxyapatite, sepiolite, and biochar on soil Cd and Pb under simulated acid rain. The results indicated that simulated acid rain reduced soil pH and facilitated the conversion of residual fractions of Cd and Pb to acid-soluble fractions, thus increasing solubility, mobility, and availability of soil Cd and Pb. Lower leachate Cd and Pb contents were found in hydroxyapatite-treated soil than were found in sepiolite and biochar-treated soils. Meanwhile, Cd and Pb concentrations in hydroxyapatite met grade IV (Cd≤0.01 mg L-1, Pb≤0.1 mg L-1) at the end of leaching (48 weeks), according to the Environmental quality standards for groundwater in China (GB14848-93). The application of hydroxyapatite, sepiolite, and biochar effectively immobilized Cd and Pb in both the water and simulated acid rain treatments. The immobilization efficiencies of Cd treated by hydroxyapatite, sepiolite, and biochar were 37.97~43.55%, 21.52~25.81%, and 26.58~33.87%, respectively, after the long-term leaching experiment. For Pb, these values were 36.35~48.65%, 24.90~29.26%, and 20.91~22.41%, respectively. Hydroxyapatite has better immobilization efficiency and maintains stronger and more durable stability than sepiolite and biochar. Therefore, hydroxyapatite is recommended to use in the remediation of Cd and Pb-contaminated agricultural soils under the condition of soil acidification.