Endpoints and bioassays to assess bioremediation efficiency of contaminated soils

Abstract

The bioremediation process used to promote environmental decontamination, utilizes living organisms, mainly microorganisms or their enzymes, to clean up contaminated sites. It is considered an effective, low cost and low impact technology. In most cases, bioremediation mineralizes contaminants or reduces their toxicity. However, there are studies that show the formation of even more toxic metabolites than the original compound during such processes. Environmentally, soil is the destination of several pollutants derived from industrial discharge, accidents, spills and waste disposal. Due to its capacity to retain some types of substances, the dispersion process is more difficult to occur and many residues can persist in the soil. Bioassays are used to determine harmful biological effects of chemicals or mixtures in environmental samples and can be carried out with cells, tissues, organs or with the entire organism. Such tests can be performed with different species (e.g., bacteria, fungi, algae, plants and animals) to assess many endpoints (death, DNA damage, morphological and physiological effects and others), both in laboratorial and field conditions. Currently, the use of bioassays has been recommended to evaluate the bioremediation efficiency since they can predict a toxic response caused by possible metabolites originated in the process. Thereby, the aim of this review is to approach the main endpoints and bioassays that are used to estimate thebioremediation effectiveness of contaminated soils. Furthermore, this work intends to emphasize the biological tests that are commonly used to monitor the bioremediation of contaminated soils, as well as assays that have appropriate responses, attempting to relate them to a particular type of contaminant or soil characteristic.