Abstract
We examined the accumulation of polycyclic aromatic hydrocarbons (PAHs), alkyl PAHs, and toxic metals in soils by the roots of Echinacea purpurea (L.) Moench, in a 20-week greenhouse study and a 2-year field study. In the greenhouse study, inoculation by arbuscular mycorrhizal fungus (AMF), Rhizoglomus intraradices (N.C. Schenck & G.S. Sm.). increased the first order accumulation rates (k1) for PAHs by 10-fold, though had no effect on the bioaccumulation rates of toxic metals. In the greenhouse study, PAHs concentrations in soil increased over time with AMF inoculation, suggesting AMF promote ‘solvent depletion’ in soils by enhancing absorption of minerals and carbon by roots, concentrating the more hydrophobic PAHs in the residual soil. Under field conditions, contaminant concentrations in soils remained unchanged over the 2-year duration of the study. Despite this, all contaminants in E. purpurea roots increased significantly, as a result of a long term extraction of contaminants by plants from soil and a reduction in soil volume as a result of plant growth. First order accumulation rates by roots were inversely correlated to log Kow for the PAHs and alkyl PAHs, indicating that accumulation is inversely related to the compound’s hydrophobicity. This study is the first to our knowledge to assess the accumulation of alkyl PAHs by roots, with implications for soil bioremediation by plants because alkyl PAHs are a major source of petrogenic contamination in soils.
Highlights
Contamination of soil by organic and inorganic pollutants is a growing problem due to industrialization, intensive agriculture, and the widespread use of xenobiotics [1,2,3]
We examined the accumulation of polycyclic aromatic hydrocarbons (PAHs), alkyl PAHs, and toxic metals in soils by the roots of Echinacea purpurea (L.) Moench, in a 20-week greenhouse study and a 2-year field study
A 20-week greenhouse experiment was conducted using a factorial block design (1 plant sp. x 2 M x 2 harvests) with E. purpurea, inoculated with or without Rhizoglomus intraradices, DAOM 181602, Premier Tech, Rivière-du-Loup, QC, and grown in homogenized soil samples collected from ten test pits (1m deep) from Victoria Island, Ottawa, ON (45 ̊ 25’ 15” N, 75 ̊ 42’ 50” W)
Summary
Contamination of soil by organic and inorganic pollutants is a growing problem due to industrialization, intensive agriculture, and the widespread use of xenobiotics [1,2,3]. Exposure to these contaminants poses a significant risk to human and ecological health [4,5] and the need for remediating soils is urgent. Alkyl PAHs usually have one to four saturated carbon atoms and can produce many different structural isomers and homologs for each hydrocarbon family. Their hydrophobic nature leads to increased accumulation and enrichment in soils, which is cause for remediation of contaminated sites
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