Transport of selected organophosphorus pesticides through alluvial sediment with the addition of microbially inoculated chars

The aim of this study was to investigate the transport behavior of two selected organophosphorus pesticides (chlorpyrifos-CP and chlorpyrifos-methyl-CPM) through Danube alluvial sediment in the absence and in the presence of microbially inoculated chars originated from sugar beet shreds (biochar produced at 400°C and three hydrochars produced at 180, 200, and 220°C). Bacillus megaterium strain was used for microbial inoculation of investigated carbon-based adsorbents. Column experiments were used to simulate sorption in non-equilibrium conditions. Obtained results were modeled using the advective-dispersive equation (ADE). For column experiments only with alluvial sediment retardation coefficient (R_d) was in the range (R_d=15.5-16) and higher biodegradation was observed for CPM (λ=4.15) than for CP (λ=1.80). The retardation coefficient (R_d) for investigated compounds in column experiments with the addition of inoculated carbon-based materials ranged from (R_d=20-275). The addition of inoculated carbon based materials in a column filled with alluvial sediment significantly increases the retardation coefficient (R_d). This may be a consequence of simultaneous adsorption on the organic matter of the alluvial sediment, on carbon-based materials and results of biosorption. The biodegradation (λ) of the investigated compounds in a column filled with the addition of inoculated adsorbents was in range (λ=0.4-4.5) and was lower compared to the column without the addition of chars. A higher retardation coefficient (R_d) in column experiments with the addition of inoculated chars was observed for biochar than for hydrochars, which is directly correlated with the higher specific surface area (SSA) of the investigated biochar. Generally, the addition of inoculated carbon-based materials to contaminated sediments has the potential as a remediation technique to inhibit the leaching of pollutants to groundwaters and affect their immobilization.

Keywords: transport, biochar, hydrochar, chlorpyrifos, chlorpyrifos-methyl, sugar beet shreds

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 European Research Executive Agency (REA). Neither the European Union nor the granting authority can be held responsible for them. Grant agreement No. 101059546