Biochar-induced changes in soil properties affected immobilization/mobilization of metals/metalloids in contaminated soils

Mahtab Ahmad, Sang Soo Lee, Sung Eun Lee, Mohammad I. Al-Wabel, Daniel C.W. Tsang, Yong Sik Ok

Research output: Contribution to journalArticle

67 Citations (Scopus)

Abstract

Purpose: Remediation of metal contaminated soil with biochar is attracting extensive interest in recent years. Understanding the significance of variable biochar properties and soil types helps elucidating the meticulous roles of biochar in immobilizing/mobilizing metals/metalloids in contaminated soils. Materials and methods: Six biochars were produced from widely available agricultural wastes (i.e., soybean stover, peanut shells and pine needles) at two pyrolysis temperatures of 300 and 700 °C, respectively. The Pb-, Cu-, and Sb-contaminated shooting range soils and Pb-, Zn-, and As-contaminated agricultural soils were amended with the produced biochars. The mobility of metals/metalloids was assessed by the standard batch leaching test, principal component analysis and speciation modeling. Results and discussion: The changes in soil properties were correlated to feedstock types and pyrolysis temperatures of biochars based on the principal component analysis. Biochars produced at 300 °C were more efficient in decreasing Pb and Cu mobility (>93 %) in alkaline shooting range soil via surface complexation with carboxyl groups and Fe-/Al-minerals of biochars as well as metal-phosphates precipitation. By contrast, biochars produced at 700 °C outperformed their counterparts in decreasing Pb and Zn mobility (100 %) in acidic agricultural soil by metal-hydroxides precipitation due to biochar-induced pH increase. However, Sb and As mobility in both soils was unfavorably increased by biochar amendment, possibly due to the enhanced electrostatic repulsion and competition with phosphate. Conclusions: It is noteworthy that the application of biochars is not equally effective in immobilizing metals or mobilizing metalloids in different soils. We should apply biochar to multi-metal contaminated soil with great caution and tailor biochar production for achieving desired outcome and avoiding adverse impact on soil ecosystem.

Original languageEnglish
Pages (from-to)717-730
Number of pages14
JournalJournal of Soils and Sediments
Volume17
Issue number3
DOIs
Publication statusPublished - 2017 Mar 1
Externally publishedYes

Fingerprint

immobilization
mobilization
soil property
metal
agricultural soil
pyrolysis
principal component analysis
phosphate
soil ecosystem
soil
metalloid
contaminated soil
complexation
hydroxide
soybean
soil type
soil surface
remediation
temperature
leaching

Keywords

  • Bioavailability
  • Black carbon
  • Charcoal
  • Plant biomass
  • Soil contamination
  • Soil remediation

ASJC Scopus subject areas

  • Earth-Surface Processes
  • Stratigraphy

Cite this

Biochar-induced changes in soil properties affected immobilization/mobilization of metals/metalloids in contaminated soils. / Ahmad, Mahtab; Lee, Sang Soo; Lee, Sung Eun; Al-Wabel, Mohammad I.; Tsang, Daniel C.W.; Ok, Yong Sik.

In: Journal of Soils and Sediments, Vol. 17, No. 3, 01.03.2017, p. 717-730.

Research output: Contribution to journalArticle

Ahmad, Mahtab ; Lee, Sang Soo ; Lee, Sung Eun ; Al-Wabel, Mohammad I. ; Tsang, Daniel C.W. ; Ok, Yong Sik. / Biochar-induced changes in soil properties affected immobilization/mobilization of metals/metalloids in contaminated soils. In: Journal of Soils and Sediments. 2017 ; Vol. 17, No. 3. pp. 717-730.
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T1 - Biochar-induced changes in soil properties affected immobilization/mobilization of metals/metalloids in contaminated soils

AU - Ahmad, Mahtab

AU - Lee, Sang Soo

AU - Lee, Sung Eun

AU - Al-Wabel, Mohammad I.

AU - Tsang, Daniel C.W.

AU - Ok, Yong Sik

PY - 2017/3/1

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N2 - Purpose: Remediation of metal contaminated soil with biochar is attracting extensive interest in recent years. Understanding the significance of variable biochar properties and soil types helps elucidating the meticulous roles of biochar in immobilizing/mobilizing metals/metalloids in contaminated soils. Materials and methods: Six biochars were produced from widely available agricultural wastes (i.e., soybean stover, peanut shells and pine needles) at two pyrolysis temperatures of 300 and 700 °C, respectively. The Pb-, Cu-, and Sb-contaminated shooting range soils and Pb-, Zn-, and As-contaminated agricultural soils were amended with the produced biochars. The mobility of metals/metalloids was assessed by the standard batch leaching test, principal component analysis and speciation modeling. Results and discussion: The changes in soil properties were correlated to feedstock types and pyrolysis temperatures of biochars based on the principal component analysis. Biochars produced at 300 °C were more efficient in decreasing Pb and Cu mobility (>93 %) in alkaline shooting range soil via surface complexation with carboxyl groups and Fe-/Al-minerals of biochars as well as metal-phosphates precipitation. By contrast, biochars produced at 700 °C outperformed their counterparts in decreasing Pb and Zn mobility (100 %) in acidic agricultural soil by metal-hydroxides precipitation due to biochar-induced pH increase. However, Sb and As mobility in both soils was unfavorably increased by biochar amendment, possibly due to the enhanced electrostatic repulsion and competition with phosphate. Conclusions: It is noteworthy that the application of biochars is not equally effective in immobilizing metals or mobilizing metalloids in different soils. We should apply biochar to multi-metal contaminated soil with great caution and tailor biochar production for achieving desired outcome and avoiding adverse impact on soil ecosystem.

AB - Purpose: Remediation of metal contaminated soil with biochar is attracting extensive interest in recent years. Understanding the significance of variable biochar properties and soil types helps elucidating the meticulous roles of biochar in immobilizing/mobilizing metals/metalloids in contaminated soils. Materials and methods: Six biochars were produced from widely available agricultural wastes (i.e., soybean stover, peanut shells and pine needles) at two pyrolysis temperatures of 300 and 700 °C, respectively. The Pb-, Cu-, and Sb-contaminated shooting range soils and Pb-, Zn-, and As-contaminated agricultural soils were amended with the produced biochars. The mobility of metals/metalloids was assessed by the standard batch leaching test, principal component analysis and speciation modeling. Results and discussion: The changes in soil properties were correlated to feedstock types and pyrolysis temperatures of biochars based on the principal component analysis. Biochars produced at 300 °C were more efficient in decreasing Pb and Cu mobility (>93 %) in alkaline shooting range soil via surface complexation with carboxyl groups and Fe-/Al-minerals of biochars as well as metal-phosphates precipitation. By contrast, biochars produced at 700 °C outperformed their counterparts in decreasing Pb and Zn mobility (100 %) in acidic agricultural soil by metal-hydroxides precipitation due to biochar-induced pH increase. However, Sb and As mobility in both soils was unfavorably increased by biochar amendment, possibly due to the enhanced electrostatic repulsion and competition with phosphate. Conclusions: It is noteworthy that the application of biochars is not equally effective in immobilizing metals or mobilizing metalloids in different soils. We should apply biochar to multi-metal contaminated soil with great caution and tailor biochar production for achieving desired outcome and avoiding adverse impact on soil ecosystem.

KW - Bioavailability

KW - Black carbon

KW - Charcoal

KW - Plant biomass

KW - Soil contamination

KW - Soil remediation

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