| Resumo: |
Success in bioremediation techniques depends on factors such as site characteristics, environmental factors, contaminant nature (temperature, pH, nutrients), presence of suitable biodegradable genes, nature of the contamination, among others. Earthworms can aid in these characteristics, through their biological, chemical, and physical properties, promoting the soil aeration, improving their nutritional characteristics, contributing also to the contaminants release adhered to the soil particles, besides helping in the dispersion of degrading microorganisms. Although there are reports of the use of earthworms in degradation of organic compounds, such as petroleum derivatives, no reports of the efficiency of this technique as an aid in the degradation of biodiesel were found. The study objective was to analyze the ability of earthworms to aid the remediation of a soil contaminated by biodiesel. To do so, toxicology (lethality and avoidance) tests were done, aiming at analyzing the two earthworm’s species (Eisenia andrei, Eudrilus eugeniae) ability to survive in the contaminated environment. With the toxicology data, remediation tests were done with the specie who presented better surviving abylities in the contaminated environment, with cattle dung as biostimulation (5g per kg of soil per week), aiming to analyze the biodiesel degradation over time. In toxicology, earthworms were resistant to biodiesel contaminations up to the proportion of 2% (Eisenia andrei) and 3% (Eudrilus eugeniae) but tended to avoid contaminated soils at concentrations above 1%. Eudrilus eugeniae proved to be the most suitable, since its lethality is lower in higher biodiesel concentrations. In the remediation analysis, earthworms (Eudrilus eugeniae) and cattle dung proved to be efficient in remediation. The earthowrms improved the biodiesel degradation in clayey soil, obtaining in these conditions 100% degradation at the end of 90 days for the samples "biostimulation and earthworms", "biostimulation, microorganisms and earthworms" and 94% degradation in the sample “microorganism and earthworms”. |
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