Application of Ecotoxicological Tests in a Preliminary Evaluation of Soils Treated on Bioreactor

Abstract

Bioremediation processes are being applied nowadays for treatment of contaminated soils by petroleum products. However, only chemical analyses are used for efficiency verification, without taking into account a biological indicator. The aim of this work was the application of two ecotoxicological tests for the evaluation of a soil contaminated by crude oil, after treatment on a bioreactor, in different conditions. Sample A was treated with biostimulation (pH, nutrients and moisture control), while samples B and C, besides biostimulation was applied bulking material (sawdust; 10% w/w) also. The ecotoxicological tests chosen were luminescent bacteria Vibrio fischeri (ISO 11348-3:1998) and an avoidance behavior test with Eisenia fetida earthworms (still in a draft form). This test consists in the exposition of the organisms to contaminated soil and control soil samples, simultaneously, to evaluate the percentage of organisms that goes from the center of the recipient to the control sample sector. The results of avoidance behavior tests of samples A, B and C were, respectively, 52%, 29% and 50%. Those results indicate no toxicity, once the criteria for a sample be considered toxic is that more than 80% of the total exposed organisms are in the control soil at the end of the test. However, the test with Vibrio fischeri indicated toxicity for sample B (CE 50 13.8%), probably because of the recent contamination. Those results indicate that, although the importance of ecotoxicological tests inclusion for the complementation of bioremediation processes evaluation, at least two tests, using different organisms must be performed for a better consideration.

Soil ecotoxicology in Latin America: Current research and perspectives

“…Sublethal endpoints such as avoidance behavior and reproduction of earthworms have been recommended as sensitive indicators to evaluate contamination by hydrocarbons in soil . In addition to these endpoints, earthworm survival, avoidance behavior of isopods, microbial basal respiration, and root density can also provide data to evaluate the efficacy of different technologies used for the bioremediation of oil‐contaminated areas . The ecotoxicology of produced wastewater and drill cuttings was explored to determine whether these materials could be used for irrigation or soil amendment, respectively.…”

Phytotoxicity of Soil Contaminated with Petroleum Derivatives and Biodiesel

“…However, few microorganisms can degrade complex structure hydrocarbon as PAHs with various aromatic rings (Atlas, 1995). Assessing biodegradation efficiency through chemical analysis does not necessarily shows the real impact each substance has on living organisms (Sisinno et al, 2007). Moreover, some compounds when degraded generate intermediate products that can be more toxic than original substance (Nunes-Halldorson et al, 2004).…”

A Microbial Bioassay for Direct Contact Assessment of Soil Toxicity Based on Oxygen Consumption of Sulfur Oxidizing Bacteria

“…Bioassays depend on changes in the physiological responses of living organisms to toxic chemicals. Ecotoxicological tests (ET) more precisely identify the cumulative and synergistic effects of toxic contaminants even if they fail to clearly identify all toxic chemicals (Sisinno et al, 2007).…”