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ABSTRACT
Introducing cow manure compost as an amendment in landfill-leachate-contaminated soils is proved to be an effective technique for the immobilization of Cd in this study. Landfill-leachate-contaminated soil was collected from an unlined landfill in China and amended with a different blending quantity of cow manure compost (0, 12, 24, 36, and 48 g per 200 g soil), which was made by mixing cow manure and chaff at a ratio of 1/1 and maturing for 6 months. pH values of five different blending quantity mixtures increased by 0.2–0.4, and the organic matter levels increased by 2.5–7%, during a remediation period of 5 weeks. Four fractions of Cd named exchangeable Cd, reducible Cd, oxidizable Cd, and residual Cd in soil were respectively analyzed by a sequential extraction procedure. Introducing the cow manure compost application resulted in more than 40% lower exchangeable Cd but a higher concentration of oxidizable Cd in soils, and mass balance results showed nearly no Cd absorption by applied material, indicating that transformation of exchangeable Cd into oxidization forms was the main mechanism of Cd immobilization when cow manure compost was used as an amendment. The Pearson correlation showed that increasing of pH values significantly improved the efficiency of Cd immobilization, with a correlation coefficiency of 0.940 (p < 0.05). This is the first attempt at heavy metal immobilization in landfill-leachate-contaminated soil by cow manure compost, and findings of this work can be integrated to guide the application.
Implications: Addition of cow manure compost (CMC) was effective in reducing exchangeable Cd in landfill-leachate-contaminated soils (LLCS). The immobilization effect of Cd was mainly assigned to the redistribution of labile soil Cd. Organic matter (OM) and pH value increased with CMC application. The pH values were more sensitive to Cd immobilization efficiency. It was proved that CMC can be safely and effectively used for the restoration of LLCS.
Funding
The research reported here was supported by the Natural Science Foundation of China (number 51278212) and the Eleventh Five-Year National Technology Supporting Plan Program of China (number 2006BAC06B04).
Additional information
Funding
Notes on contributors
Zhuwei Liao
Zhuwei Liao and Jia Wang are Ph.D. candidates.
Jia Wang
Zhuwei Liao and Jia Wang are Ph.D. candidates.
Rui Wan
Rui Wan and Shuang Xi are engineers engaged in soil remediation.
Shuang Xi
Rui Wan and Shuang Xi are engineers engaged in soil remediation.
Zhuqi Chen
Zhuqi Chen is an associate professor.
Zhulei Chen
Zhulei Chen is a professor.
Yingjian Yu
Yingjian Yu is a Ph.D. candidate.
Sijie Long
Sijie Long is a master’s candidate.
Huabin Wang
Huabin Wang is a Ph.D. candidate.