Title : The effect of bio augmentation and biochar-stimulation on metal (loid) s contaminated soil and plant growth
Abstract:
owadays, environmental contamination by metal (loid) s is a major problem worldwide and poses severe scientific challenges. Metal (loid) s are natural constituents of the environment, but indiscriminate use for human purposes has altered their geochemical cycles and biochemical balance. This results in excess release of metal (loid) s into natural resources like the soil (Tang et al., 2015). Therefore, the removal of metal (loid) s from contaminated soils is imperative in order to minimize their impact on the ecosystems. In the last decade, several efforts were carried out by scientific community to improve the green technologies effectiveness in soil management. The use of biological methods avoids physico-chemical strategy limitations: i) changes in native soil flora; ii) irreversible alterations in soil properties; iii) secondary pollution; iv) intensive labor; and v) high cost (Zubair et al., 2016). In fact, biological approach (bioremediation) may be an attractive alternative to physico-chemical methods: it is an environmentally friendly and economical strategy that uses organisms (microorganisms or plants) for polluted soils remediation and has high public acceptance (Kang et al., 2016). Success of bioremediation depends on the proper selection of metal(loid) tolerant organisms. Various studies have focused on bioremediation effectiveness by addition of nutrients (biostimulation) or introduction of microorganisms to contaminated sites (bioaugmentation). Biostimulation involves the modification of the environment to stimulate the growth and activities of native microorganisms involved in the remediation process and thus this increases the efficiency of bioremediation. This can be done by addition of various forms of limiting nutrients and electron acceptors (da Conceicao Gomes et al., 2016). Often in biostimulation systems, both organic fertilizers and organic amendments of different origins have been proposed for decontaminating metal(loid) polluted soils. An organic amendment that can be utilized as a fertilizer and a metal(loid) stabilizer is biochar. It is a carbonaceous material produced from oxygenlimited pyrolysis of biomass under low temperatures (Trigo et al., 2014). Bioaugmentation involves the introduction of microorganisms isolated from the contaminated site or carefully selected and genetically modified to support indigenous organisms to remediate contaminated sites (Hamdia et al., 2007). At times, nutrient addition or microbial augmentation alone is not sufficient for a successful remediation of metal(loid) polluted soils. Recent studies show that a combined technology of bioaugmentation assisted by biostimulation is a high-efficiency and promising approach for the bioremediation of metal (loid) contaminated soils (Mahbub et al., 2017; Rojjanateeranaj et al., 2017; Wang et al., 2017). In this context, the present study aims to evaluate the effect of the bioaugmentation and biostimulation strategies, alone and combined, in a metal (loid) contaminated site by using Arabidopsis thaliana model plant. The general purposes of the study presented here are: i) to isolate and characterize a metal(loid) resistant bacteria strain, ii) to analyze how metal(loid)s, biochar and the resistant microorganism could influence plant development and growth and iii) to understand the mechanisms involved in plant metal(loid)s tolerance.
