YANG Fang1,2,4, MAO Zhiqiang1,2, SUN Lu1,2, LI Yang1,2,4, WU Yang1,2, WANG Bing3, LIAO Luyun1,2, ZHANG Heng1,2
(1. Sichuan Institution of Geological Engineering Investigation Group Co., Ltd, Chengdu 610072, China;
2. Sichuan Tianshengyuan Environmental Services Co., Ltd, Chengdu 610072, China;
3. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China.
4. Applied Nuclear Technology in Geosciences Key Laboratory of Sichuan Province (College of Earth Science, Chengdu University of Technology), Chengdu 610059, China;)
Abstract: The leaching and batch experiments were conducted to study the effect of hydroxyapatite addition on the bioaccessibility and speciation of Cd and Zn in polluted soil in Chengdu Plain. Additive ratios of hydroxyapatite were set as 0% (CK), 1% (P1), 3% (P3), 5% (P5). The study found that: (1) Hydroxyapatite could decrease the leaching of Cd and Zn significantly. Compared with the CK that with a leaching loss of 110 μg and 9.3 mg for Cd and Zn, respectively, hydroxyapatite addition at P1, P3 and P5 reduced the Cd leaching by 82.7%, 92.7%, 90.7%, and the Zn leaching by 94.8%, 97.1%, 94.6%, respectively; (2) After 45 days incubation, hydroxyapatite addition significantly increased the soil pH by 0.30, 0.53 and 0.95 of pH units with treatment of P1, P3 and P5, respectively; (3) Compared with the CK, hydroxyapatite addition at P1, P3 and P5 reduced the available Cd (0.025 M HCl) by 59.0%, 94.7% and 98.7%, and the available Zn by 18.6%, 49.6% and 87.6%, respectively; (4) Hydroxyapatite significantly decreased the contents of exchangeable and carbonate forms of Cd and Zn, and increased the contents of Fe-Mn oxides bound, organic and residual forms of Cd and Zn after 45 days incubation, hence promotes the transformation of Cd and Zn from the active forms to the inactive ones. These findings indicate that hydroxyapatite can effectively decrease the heavy metals risk and has a good application prospect of remediation of Cd and Zn contaminated soil in typical farmland of Chengdu plain.
Key words: hydroxyapatite; Cd; Zn; Chengdu plain; soil remediation
EARTH AND ENVIRONMENT Vol.48, No.5, Tot No.337, 2020, Page 567-573
