Effects of DDE occurrence on the Solanum lycopersicum rhizosphere under different organic carbon sources

Contamination by Persistent Organic Pollutants such as DDTs (p´p´-DDT and its metabolites p´p´-DDE and p´p´-DDD) is an important threat to soil ecosystem quality. Plant-based clean up technologies are as sustainable solutions to contaminated soil remediation. They rely on the physiological abilities of selected plants to decrease pollutants from soil through different processes occurring in the rhizosphere involving symbiotic and non-symbiotic interactions with natural microorganisms. Solanum lycopersicum is known to be able to accumulate DDTs in roots, owing to exudate production, which makes this contaminant bioavailable in soil. In this context, a greenhouse experiment was performed using pots filled with DDE-contaminated soil and watered with different kinds of dissolved organic carbon (DOC). Control soils (without plant and/or DDE) were also performed. Finally, we obtained 12 different conditions. Soil and plant samples were collected 40 days after the DDE exposure. The effects of the different treatments on the natural microbial community of the rhizosphere were evaluated in terms of microbial abundance, viability, structure, dehydrogenase activity and possible DDE degradation. Moreover, roots and shoots of the tomato plants were also sampled and analysed for the determination of the pesticide bioconcentration. The main results from the different experimental conditions will be discussed.