Pulsed electric field induced redistribution of fluorescent compounds from water-extractable soil organic matter

Modifications of bacterial activities are observed when continuous electric current is applied in soil for soil remediation purposes (electrokinetic). In this study we found a significant increase of 330% of the total heterotrophic culturable bacteria 2 d after soil samples had been submitted to pulsed electric field (PEF) treatment (E ∼ 4 KV/cm, τ ∼ 5 ms, 3 pulses) resulting from pulsed electric current injections. We hypothesized that this result was caused by qualitative and/or quantitative modifications of the dissolved organic matter and tested this using a γ-sterilized model soil. The incidence of electrical parameters (electric field intensity and pulse duration) on the water-extractable organic matter was analysed using two types of experimental set-ups for current injection. These experimental set-ups exhibited different volume, physical state (liquid, solid) of the soil samples and different electrical conditions. Total organic carbon content and fluorescence signature (excitation-emission matrix, EEM) were monitored for all samples. A 67% decrease in the ratio between higher and lower molecular weight fluorescent compounds was observed, indicating a new distribution of the fluorescent compounds into the dissolved organic matter following PEF treatment.