title: Rhizosphere gradients of polycyclic aromatic hydrocarbon (PAH) dissipation in two industrial soils and the impact of arbuscular mycorrhiza.
abstract: Phytoremediation of organic pollutants depends on plant-microbe interactions in the rhizosphere, but the extent and intensity of such rhizosphere effects are likely to decrease with increasing distance from the root surface. We conducted a time-course pot experiment to measure dissipation of polycyclic aromatic hydrocarbons (PAHs) in the rhizosphere of clover and ryegrass grown together on two industrially polluted soils (containing 0.4 and 2 g kg(-1) of 12 PAHs). The impact of the fungal root symbiosis arbuscular mycorrhiza (AM) on PAH degradation was also assessed, as these fungi have previously improved plant establishment on PAH-polluted soils and enhanced PAH degradation in spiked soil. The two soils behaved differently with respect to the time-course of PAH dissipation. The less polluted and more highly organic soil showed low initial PAH dissipation rates, with small positive effects of plants after 13 weeks. At the final harvest (26 weeks), the amounts of PAHs extracted from nonplanted pots were higher than the initial concentrations. In parallel planted pots, PAH concentrations decreased as a function of proximity to roots. The most polluted soil showed higher initial PAH dissipation (25% during 13 weeks), but at the final harvest PAH concentrations had increased to values between the initial concentration and those at 13 weeks. An effect of root proximity was observed for the last harvest only. The presence of mycorrhiza generally enhanced plant growth and favored growth of clover at the expense of ryegrass. Mycorrhiza enhanced PAH dissipation when plant effects were observed.
authors.affiliation: Laboratoire des Interactions Microorganismes-Minéraux-Matière Organique, dans les Sols (LIMOS) - CNRS, FRE 2440, H. Poincaré University, P.O. Box 239, F-54506 Vandoeuvre-les-Nancy, France. Erik.Joner@skogforsk.no
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Joner
authors.forename: Corinne
authors.initials: C
authors.lastname: Leyval
mesh_terms: D001673:Biodegradation, Environmental; D005658:Fungi; D007220:Industrial Waste; D008129:Lolium / Q000737:chemistry / Q000254:growth & development; D029902:Medicago / Q000737:chemistry / Q000254:growth & development; D018517:Plant Roots / Q000382:microbiology; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis* / Q000493:pharmacokinetics; D012989:Soil Pollutants / Q000032:analysis* / Q000493:pharmacokinetics
chemical_list: D007220:Industrial Waste; D011084:Polycyclic Aromatic Hydrocarbons; D012989:Soil Pollutants