Enhancing Sorption and Biodegradation: The Influence of Inoculated Biochar on the Transport of Organophosphorus Pesticides in Sandy Soil

This study investigates how soil enriched with carbon-rich materials, such as biochar, influences the sorption and biodegradation capabilities of organophosphorus pesticides (Fenthion, Fenitrothion, Parathion Methyl) under nonequilibrium conditions. Additionally, experiments were conducted to enhance the biodegradation potential of biochar from Miscanthus×giganteus by introducing bacteria capable of degrading organophosphorus pesticides (OPPs).

Transport experiments were carried out in stainless-steel columns (4 cm diameter, 20 cm length) filled with soil amended with biochar previously inoculated with a biofilm of vegetative cells from the Bacillus megaterium BD5 strain. To assess the impact of inoculated biochar on pesticide transport, 0.5% of this adsorbent was added to the total soil mass in the column. Thiourea was included as a tracer at a concentration of approximately 4 mg/L. Pesticide solutions were pumped through the column, and eluates from the outlet were collected at various time intervals, and analyzed for pesticide concentrations using GC/MS Agilent 7890 A/5975C.

Data analysis involved the use of a mathematical transport model by solving the advection-dispersion equation (ADE), yielding transport parameters (retardation, R_d, and biodegradation, λ) and breakthrough curves. The retardation coefficient for investigated compounds ranged from R_d=40-100, with increasing order of Parathion-methyl < Fenthion < Fenitrothion. Biodegradation (λ) of the compounds ranged from λ=0.2-3.3, increasing in the same order. No clear correlation was observed between the octanol-water partition coefficient (K_ow), retardation, and biodegradation, indicating that hydrophobicity alone did not solely determine sorption and transport characteristics under specific experimental conditions.

In summary, introducing inoculated biochar likely contributes to the simultaneous adsorption of organic compounds onto the added adsorbents within the porous material and biosorption onto the inoculated biochar. Generally, adding inoculated carbon-based materials to contaminated sediments shows potential as a remediation technique, inhibiting pollutant leaching to groundwater and facilitating immobilization.

 

Keywords: transport, biochar, organophosphorus pesticides, biodegradation

Acknowledgment

Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Executive Agency (REA). Neither the European Union nor the granting authority can be held responsible for them. Grant agreement No. 101059546