Microbially inoculated chars strongly reduce the mobility of alachlor and pentachlorobenzene in an alluvial sediment

The objective of this study was to investigate the transport behavior of two organic and persistent contaminants (alachlor and pentachlorobenzene) on Danube alluvial sediment in the absence and in the presence of microbially inoculated biochar produced at 400 degrees C and three hydrochars produced at 180, 200, and 220 degrees C. Stainless steel columns were used for the sorption experiments in nonequilibrium conditions. Obtained results were modeled using the advective-dispersive equation under nonequilibrium conditions. Transport of these compounds through the alluvial sediment column showed that the retention time increased with increasing molecular hydrophobicity. Inoculated biochar increases the retardation of both compounds: twofold for pentachlorobenzene compared with alachlor as a consequence of a higher hydrophobicity. Obtained results indicate that the highest biodegradation coefficient was observed for pentachlorobenzene (lambda = 10) in alluvial sediment with addition of an inoculated hydrochar, which is assumed to be a consequence of biosorption. Moreover, all experiments on the columns indicate that the addition of inoculated chars yields a significantly higher R-d coefficient for pentachlorobenzene than for alachlor. Bacterial counts increased in all of the column experiments, which indicates the successful adaptation of microorganisms to experimental conditions and their potential for the removal of a large number of organic pollutants. Thus, addition of inoculated chars to contaminated sediments has the potential as a remediation technique to inhibit the leaching of pollutants to groundwaters. Integr Environ Assess Manag 2022;00:1-10. (c) 2022 SETAC

Automated summary

The objective of this study was to investigate the transport behavior of two organic and persistent contaminants on alluvial sediment and the potential of microbially inoculated biochar and hydrochar as remediation techniques. The results showed that the retention time of the contaminants increased with increasing hydrophobicity, and the inoculated biochar increased the retardation of the compounds. Additionally, the bacterial counts increased in all experiments, indicating the potential for the removal of organic pollutants. Therefore, the addition of inoculated chars to contaminated sediments has the potential to inhibit the leaching of pollutants to groundwaters.