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Vermicompost in Contaminated Soil E-mail
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Sunday, 12 August 2007
Vermicompost in Contaminated Soil


Knight, S., Edwards, C.A., Lanno, R.P., Arancon, N.Q., Voight, A., Dick, R.,

The Ohio State University, Columbus, OH, U.S.A.

The bioremediation of soil contaminated with polycyclic aromatic hydrocarbons (PAHs) often involves the amendment of the soil with a source of organic matter, with the aim of enhancing the existing soil microbial community and increasing the rates of hydrocarbon degradation. Vermicomposts and their extracts (‘teas’) are a rich source of a wide range of microorganisms, which seem to provide a suitable soil amendment for enhancing rates of polycyclic aromatic hydrocarbon (PAH) biodegradation, as was demonstrated by a recent field study in Illinois. Our bench-top experiments examine the effectiveness of a cattle manure vermicompost, and liquid extracts of vermicompost (teas) amendments in enhancing the rates of degradation of pyrene (PYR) and phenanthrene (PHE) in a natural soil.

The experimental design comprised four soil treatments, with each treatment amended with a mixture of PYR (250 mg/kg) and PHE (500 mg/kg). Three control treatments (Webster clay loam (WCL) soil (pH – 5.5, organic matter – 2.4 g C/kg, cation exchange capacity – 21 cmol./kg, clay – 36%), vermicompost, and WCL amended with 240 ml of 50% (v/v) vermicompost tea) were also included.  The treatments treated with PAHs included: WCL + vermicompost (5% w/w), WCL + vermicompost (50%, w/w), WCL + vermicompost tea (240 ml, 5% solution (v/v), added to soil field capacity), and WCL + vermicompost tea (240 ml, 50% solution (v/v), added to soil field capacity). Three replicates of each soil treatment were incubated at 20ºC and sampled for chemical and microbial analysis 0, 4, 8, 16, 32, and 64 days after treatment. The dissipation of PYR and PHE was assessed by measuring total PAH levels using a hexane extraction of soils, and the potentially bioavailable fraction of PAHs using solid-phase microextraction fibres (SPMEs) (30 um C18 coating) and gas chromatography. The microbial community structure and activity was monitored by measuring substrate-induced respiration (SIR), total microbial biomass, and phospholipid fatty acid (PLFA) composition. Dissipation curves for the PAHs and associated microbial parameters will be presented and discussed. These provide evidence of the potential of vermicomposts and vermicompost teas in the bioremediation of polluted soils.


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