Elution of Polycyclic Aromatic Hydrocarbons in Soil Columns Using Low-Molecular-Weight Organic Acids
- Huoliang Konga,
- Rui Sunb,
- Yanzheng Gao *b and
- Bingqing Sunb
- a Institute of Organic Contaminant Control and Soil Remediation, College of Resource and Environmental Sciences, Nanjing Agricultural Univ., Nanjing 210095, China and Jiangsu Key Lab. of Atmospheric Environment Monitoring and Pollution Control, Nanjing Univ. of Information Science and Technology, Nanjing 210044, China
b Institute of Organic Contaminant Control and Soil Remediation, College of Resource and Environmental Sciences, Nanjing Agricultural Univ., Nanjing 210095, China
The impacts of low-molecular-weight organic acids (LMWOAs) on the release, distribution, and availability of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils were investigated using soil column experiments. Citric and malic acids, as representative LMWOAs, significantly promoted the release and enhanced the availability of phenanthrene and pyrene in three soil columns. Both the mobilized amounts and availabilities of test PAHs increased with increasing concentrations of citric or malic acid. When the concentration of citric acid was 80 mmol L−1, the mobilized amounts of phenanthrene and pyrene in a yellow-brown soil column increased by approximately three times compared with the control. The simultaneous decreases in phenanthrene and pyrene not extractable by n-butanol relative to their initial amounts were 63.17 and 73.38%, respectively, which indicated that a large amount of initially nonextractable PAHs in soils were transformed into n-butanol-extractable PAHs. After elution, the PAH residual concentrations in the soil layers followed the order bottom layer > middle layer > top layer. Similar results were observed for experiments using malic acid. Results obtained showed that LMWOAs could dissolve a portion of soil organic matter into solution and disrupt the organic–metal ion–mineral linkages in soils, resulting in PAH release and dissolution of metal ions; however, the mechanism of elution of the PAHs in the soil column by LMWOAs was not in accord with the mechanism by which metal ions were dissolved. The findings of this work may be instructive for remediation strategies in contaminated soils.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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