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Zero-valent iron nanoparticles and organic amendment assisted rhizoremediation of mixed contaminated soil using Brassica napus

Authors: June Hidalgo, Mikel Anza, Lur Epelde, José M. Becerril, Carlos Garbisu

Journal: Environmental Technology & Innovation

Soil is one of our most important natural resources. Regrettably, the expansion of human activities has resulted in the degradation of the soil resource due to contamination with a myriad of organic and inorganic compounds. The remediation of mixed contaminated soils, i.e. soils contaminated with both organic compounds and metals, is challenging as it requires actions to simultaneously decrease metal-induced risks and organic contaminant concentrations. Here, we evaluated the effect of the addition of zero-valent iron nanoparticles (nanoremediation) and organic amendments (biostimulation) on the rhizoremediation, using Brassica napus plants, of soil simultaneously contaminated with zinc (2,500 mg kg-1) and lindane (100 mg kg-1). We used a factorial design with three factors (amendment, nZVI, plant) to evaluate the impact of the applied remediation actions on lindane and extractable Zn concentrations, as well as on soil health recovery as manifested by the values of different soil microbial indicators. The studied microbial indicators were not negatively affected by nZVI application. The application of nZVI was the most effective factor regarding the targeted reduction in lindane concentration (51% average reduction in nZVI treated soils). The highest reduction in extractable Zn was achieved in the presence of B. napus, nZVI and organic amendments (99 and 95% reduction in horse manure-amended and sewage sludge-amended soils, respectively). The combination of the three factors led to the highest values of soil microbial indicators (although a significant triple interaction was not observed for all parameters), especially when combined with horse manure amendment: in this case, prokaryotic richness increased by 64%, respiration by 376%, eukaryotic abundance by 333%, and prokaryotic abundance by 437%, compared to untreated soils. The combination of remediation approaches (rhizoremediation with B. napus, nanoremediation with nZVI, biostimulation with organic amendments) can help overcome the limitations of each individual strategy.

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Authors: J Hidalgo, M Anza, L Epelde, JM Becerril, C Garbisu
Title: Zero-valent iron nanoparticles and organic amendment assisted rhizoremediation of mixed contaminated soil using Brassica napus
Journal: Environmental Technology & Innovation
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Authors: L Epelde, M Mendizabal, L Gutiérrez, A Artetxe, C Garbisu, E Feliu
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Bioinocula and CROPping systems: an integrated biotechnological approach for improving crop yield, biodiversity and REsilience of Mediterranean agro-ecosystems (ReCrop; 2021-2024)

The Mediterranean economy is highly dependent on agriculture.
However, agricultural sustainability and productivity in this region are under serious threat due to climate change and depletion of water resources. This is worsened by poor management practices, such as the overuse of chemical fertilizers and pesticides, overgrazing, and monoculture farming. ReCROP aims to redesign Mediterranean agrosystems with improved resilience capacity and higher productivity, focusing on the development of sustainable agricultural production systems through the combined use of biotechnological tools and environmentally friendly agronomic practices. This will allow farming systems to face climate change trough the improvement of below and aboveground biodiversity, fertility, and water conservation. RECROP uses the novel approach of plant-microorganism management that relies on the increase of soils functions and health by using bioinocula, amendments, cropping systems, and climate-ready crops, to increase crop yields while providing ecological services, e.g., increasing carbon sequestration, organic matter, nutrient cycling and water conservation.

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Agriculture is currently confronting an increasing human population and limitations of soil use due to, among other reasons, pollution levels above food safety threshold values. Some agricultural practices increase the heavy metal content (HM) of agricultural soil, representing an important threat for the European agricultural development. The use of microorganisms as plant growth promoters has been increasingly studied for a number of years, but it has only recently been proposed to improve plant metal tolerance. Regrettably, plant-microorganism-pollutant interactions are still poorly understood and the molecular underlying mechanisms are mostly unknown. The abovementioned challenges for agricultural production require the study of these mechanisms to better promote a more efficient and sustainable agriculture. This project will venture into new unchartered territory by focusing on the molecular interactions between a probiotic actinobacterium (Micromonospora cremea) and its host, Pisum sativum (garden pea), in the presence of HMs. We will evaluate the capacity of M. cremea CR30 to improve plant tolerance to HM polluted soils, in addition to unraveling the molecular dialogue during the first and late steps of their interaction. Early step interactions are crucial in plant promotion and protection against external stresses, like pollution by HM. Here, we propose the use of new -omic technologies to study these molecular interactions between plants and microorganisms under metal stress, providing a new pathway for an improved soil management. This project addresses a crucial objective in food security, the development of sustainable agricultural practices to control potentially adverse HM effects on plant health.

Remediation of Organically Contaminated Soil Through the Combination of Assisted Phytoremediation and Bioaugmentation

Authors: Mikel Anza, Oihane Salazar, Lur Epelde, José María Becerril, Itziar Alkorta and Carlos Garbisu

Journal: Applied Sciences

Vol: 9, 4757; doi:10.3390/app9224757

Date: 2019

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Here, we aimed to bioremediate organically contaminated soil with Brassica napus and a bacterial consortium. The bioaugmentation consortium consisted of four endophyte strains that showed plant growth-promoting traits (three Pseudomonas and one Microbacterium) plus three strains with the capacity to degrade organic compounds (Burkholderia xenovorans LB400, Paenibacillus sp. and Lysinibacillus sp.). The organically contaminated soil was supplemented with rhamnolipid biosurfactant and sodium dodecyl benzenesulfonate to increase the degradability of the sorbed contaminants. Soils were treated with organic amendments (composted horse manure vs. dried cow slurry) to promote plant growth and stimulate soil microbial activity. Apart from quantification of the expected decrease in contaminant concentrations (total petroleum hydrocarbons, polycyclic aromatic hydrocarbons), the e ectiveness of our approach was assessed in terms of the recovery of soil health, as reflected by the values of di erent microbial indicators of soil health. Although the
applied treatments did not achieve a significant decrease in contaminant concentrations, a significant improvement of soil health was observed in our amended soils (especially in soils amended with dried cow slurry), pointing out a not-so-uncommon situation in which remediation e orts fail from the point of view of the reduction in contaminant concentrations while succeeding to recover soil health.