Effect of Rhamnolipid Jbr-425 on the Development of Brassica Juncea in Soils of Urban Gardens of Sevilla (Spain).

Abstract

The current need to recover soils contaminated with potentially toxic metals to lessen their impact on the environment and on the food chain, leads different methods are being developed for their extraction. There is an additional concern when contamination occurs in urban farm soil. Phytoextraction can be enhanced by applying biodegradable biosurfactants, promoting the bioavailability of contaminants and their subsequent uptake by the plant. This technique is called assisted or induced phytoextraction. This work aims to evaluate the extraction of heavy metals from contaminated soils from an urban orchard in the town of Sevilla using Brassica juncea plants, as well as to estimate the improvement that the application of a biodegradable biosurfactant (Ramnolipid JBR-425) implies. For this, a greenhouse trial was carried out with two soils from an urban park and an agricultural one in which Brassica juncea was grown. A solution of Ramnolipid JBR-425 with a concentration of 1000 mg kg-1 was added to half of the pots to evaluate its effect on the development of the plants (number of leaves, plant height). The data collected showed a negative effect produced both by soil contamination and by the presence of rhamnolipid. The soil used in the experiment, as well as the plants, were collected for further analysis. Plant samples were divided into aerial part, root and fruit, to determine the amounts of heavy metals in the soil and extracted in the aerial part. The determination of heavy metals in soil was carried out by ICP-OES after AEDT extraction. Likewise, parameters such as electrical conductivity and pH were also measured. For the extraction of the metals extracted by the plants, acid digestion of the plant samples was performed and then they were measured using ICP-OES. The plants treated with rhamnolipid showed less development both in plant height and in the number of leaves; likewise, the biomass production capacity was reduced. These factors may be due to the toxic effect of rhamnolipid, as well as the effect of Potentially Toxic Elements. Although the plants with rhamnolipid application had higher concentrations of heavy metals in their tissues, since there was a notable decrease in biomass, they did not extract as much as the plants without treatment