ORIGINAL RESEARCH
Enhanced Immobilization of Polycyclic Aromatic
Hydrocarbons in Contaminated Soil Using Forest
Wood-Derived Biochar and Activated Carbon
under Saturated Conditions, and the Importance
of Biochar Particle Size
Ali Daryabeigi Zand1, Peter Grathwohl2
1Faculty of Environment, University of Tehran,
23, Ghods St., 141556135 Tehran, Iran
2Center for Applied Geosciences (ZAG), University of Tübingen,
Hölderlinstr. 12, 72076 Tübingen, Germany
23, Ghods St., 141556135 Tehran, Iran
2Center for Applied Geosciences (ZAG), University of Tübingen,
Hölderlinstr. 12, 72076 Tübingen, Germany
Submission date: 2015-09-17
Final revision date: 2015-10-11
Acceptance date: 2015-10-12
Publication date: 2016-01-25
Pol. J. Environ. Stud. 2016;25(1):427–441
KEYWORDS
TOPICS
ABSTRACT
Leaching behavior of organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) can be
altered in the presence of organic amendments through enhanced sorption of PAHs to the amended soil. The
aim of the present study was to investigate the influence of biochar in two forms (i.e., crushed and pulverized),
and granular activated carbon on immobilization and leaching behavior of selected PAHs from contaminated
soil into water using the column leaching test. The influence of biochar particle size on leaching behavior of
PAHs in biochar-amended soil was also evaluated for the first time in this study. Results showed relatively
high initial concentrations of naphthalene, fluorene, and pyrene for unamended column (B1). Strong sorption
of all PAHs to soil was observed in this study. At the end of the experiment less than one percent of the solid
phase content of the sum of PAHs was released into water in columns B3 and B4. Change in pH due to the
application of organic amendments did not affect PAH leaching results. The addition of pulverized biochar
and granular activated carbon to soil remarkably reduced mobilization and leaching of the studied PAHs in
most cases; however, higher molecular weight PAHs (i.e., pyrene, benzo(b)fluoranthene, and indeno(1,2,3-
cd)) were mobilized in the presence of crushed biochar in soil. The controlling role of biochar particle size on
mobilization and release of PAHs in soil was observed. The application of pulverized biochar and activated
carbon increased colloid content of the column effluents while reducing their dissolved organic carbon (DOC)
content, suggesting a more significant role of colloid-facilitated transport than DOC-associated transport of
PAHs in their leaching from carbon-amended soils, particularly for higher molecular weight PAHs. Based
on the obtained results, pulverized biochar and granular activated carbon demonstrated promising and comparable
performance in immobilizing PAHs in soil and reducing their leaching from soil into water through
enhanced sorption of PAH compounds, which is markedly favorable in terms of soil remediation.
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