Investigating the Effect of Medicago sativa L. and Trifolium pratense L. Root Exudates on PAHs Bioremediation in an Aged-Contaminated Soil

Abstract

Polycyclic aromatic hydrocarbons (PAH) are persistent organic compounds of major concern that accumulate in the environment, especially soils, and require remediation. Researches to develop bioremediation and phytoremediation (alternative eco-friendly technologies) are being conducted. First, a bioaccessibility measurement protocol was adapted to a brownfield soil using Tenax® beads in order to compare PAHs bioaccessibility in soil samples. PAHs desorption kinetics were established, described by a site distribution model, and a common extraction time was calculated (48 h). Second, the role of two Fabaceae (Medicago sativa L. or Trifolium pratense L.) root exudates in enhancing PAHs bioaccessibility and biodegradation in the studied soil was evaluated during microcosms experiments (28 °C). The CO 2 emissions were significantly higher in presence of T. pratense exudates; the dehydrogenase activities showed improvements of the soil microbial activity in presence of two types of root exudates compared to untreated soil samples; the PAHs residual contents decreased more in untreated samples than in the presence of T. pratense exudates; and M. sativa exudates lowered PAHs bioaccessibility but not residual contents.

Targeting the right parameters in PAH remediation studies

“…Recently, studies have started to assess the bioavailability of PAHs in soils/sediments after undergoing remediation. Posada-Baquero et al (2019 recently applied the ISO/TS 16751 norm to determine the environmental availability of PAHs in aged-contaminated soils before and after remediation treatments, and our team measured PAH bioaccessibility throughout a bioremediation trial (Davin et al, 2019) and a rhizoremediation trial (Davin et al, 2020) before the norm came out.…”

Temporal Evolution of PAHs Bioaccessibility in an Aged-Contaminated Soil during the Growth of Two Fabaceae

“…The PAHs' bioaccessibility measurement protocol was developed based on a modelling technique previously described and used on a different aged-contaminated soil [15] but it will be reminded hereafter. The objective was to determine the time of contact between the soil solution and the Tenax ® beads (which serve as surrogate for the soil microbiota) that would extract the bioaccessible fraction of PAHs in the aged-contaminated soil.…”

“…Therefore, a 24 h extraction time was used to determine the PAHs' bioaccessible contents in the rhizoremediation experiment. As a comparison, when the PAH desorption kinetics were modelled on a different PAH aged-contaminated soils [15] the common extraction time was 48 h. 3.2. PAHs Rhizoremediation…”

“…For example, saponins are a diverse group of molecules composed of non-sugar aglycones coupled to sugar chain units, which gives them surface-active properties [14]. In a previous study [15], we hypothesized that exudates from two Fabaceae (Medicago sativa L. or Trifolium pratense L.) could, as part of the rhizospheric effect, enhance the PAHs' bioaccessibility in an aged-contaminated soil, and thus enhance the PAHs' biodegradation. The results showed that a single-dose addition of root exudates to an aged-contaminated soil in a microcosm incubation experiment (4 weeks), did not enhance the PAHs' bioaccessibility nor dissipation.…”

Conceitos E Aplicações Entre Plantas E Microrganismos Na Remediação De Hidrocarbonetos

“…Os HPAs são compostos orgânicos de grande preocupação que persistem no meio ambiente e se acumulam especialmente nos solos (DAVIN et al, 2019). Diante disso, percebe-se a necessidade de desenvolver estratégia de biorremediação para remoção de compostos orgânicos resultantes das ações antrópicas tem atraído bastante atenção nos últimos anos.…”