Influence of three species of arbuscular mycorrhizal fungi on the ...

Mycorrhiza (2005) 16: 43–50 DOI 10.1007/s00572-005-0012-y

ORIGINA L PA PER

Andrea Volante . Guido Lingua . Patrizia Cesaro . Andrea Cresta . Manuela Puppo . Luigi Ariati . Graziella Berta

Influence of three species of arbuscular mycorrhizal fungi on the persistence of aromatic hydrocarbons in contaminated substrates Received: 28 February 2005 / Accepted: 5 July 2005 / Published online: 3 September 2005 # Springer-Verlag 2005

Abstract Aromatic hydrocarbons are pollutants which have mutagenic and carcinogenic properties as well as relatively high hydrosolubility. Their presence in soils makes techniques such as bioremediation an important topic for research. In this work, the effect of arbuscular mycorrhiza (AM) on the persistence of benzene, toluene, ethylbenzene and xylene (BTEX) in artificially contaminated substrates was evaluated. Leek plants were grown with three AM fungal species using a specially designed mesocosm system, in which internal air and substrate samples were analyzed by gas chromatography for BTEX content. Strong reductions in the BTEX concentration in substrates were generally observed in the presence of mycorrhizal plants. Residual BTEX content ranged between nearly total disappearance (99.5), toluene (>99), ethylbenzene (>99) or xylene (>98.5) (Fluka, Buchs, Switzerland). Five grams of each sample was transferred into sealed tubes, and after heating at 60°C for 30 min, a 100-μl sample of the “head space” was collected and injected into a GC Variant 3400 gas chromatograph with a flame ionization detector (FID) and HS850 autosampler (CE Instruments). An SPB5 chromatographic column (Supelco, 30 m length, 0.53 ID, 3 μm film) was used (EPA 5021 method). The analysis was performed as follows: 37°C, 4 min; 37–95°C, 4°C min−1; 95°C, 0.1 min; 95–145°C, 8°C min−1; 145°C, 8 min; and 145–200°C, 25°C min−1. Benzene, ethylbenzene, toluene

and xylene (Fluka) were used as standards. The residual concentrations of the four hydrocarbons were evaluated (n=3) at time 0 and after 2, 5, 8, 24, 72 and 144 h. To verify if the hydrocarbons adsorbed on the active carbon and mixed to the substrate were bioavailable, the vermiculite-based substrate was supplemented with a suspension of BTEX-degrading bacteria (BLF5500, Biofuture Ltd., Dublin, Ireland) under sterile conditions. One millilitre of bacterial suspension (106 UFC ml−1) was supplemented to 50 ml of substrates. Samples without bacteria were used as negative controls. Head space gas chromatography was performed as described above to measure the residual BTEX concentration (n=3) after 0, 1, 5 and 11 days, incubation at room temperature. Differences in comparison to the respective control were evaluated by oneway ANOVA (p