Enhanced retention of hydrophobic pesticides in subsurface soils using organic amendments.

The rapid global population growth since the early 2000s has significantly increased the demand for agricultural products, leading to widespread pesticide use, particularly organophosphorus pesticides (OPPs). This extensive application poses severe environmental risks by contaminating air, soil, and water resources. To protect groundwater quality, it is crucial to understand the transport and fate of these pesticides in soil and sediment. This study investigates the effects of hydrochars and biochars derived from sugar beet shreds (SBS) and Miscanthus×giganteus (MIS) on the retardation and biodegradation of OPPs in alluvial Danube sandy soil. The research is novel in its approach, isolating native OPP-degrading bacteria from natural alluvial sandy soil, inoculating them onto chars, and reapplying these bioaugmented chars to the same soil to enhance biodegradation and reduce pesticide leaching. The amendment of chars with immobilized Bacillus megaterium BD5 significantly increased bacterial abundance and activity. Metabarcoding of the 16S rRNA gene revealed a dominance of Proteobacteria (48.0-84.8 %) and Firmicutes (8.3-35.6 %). Transport modeling showed retardation coefficients (Rd) for OPPs ranging from 10 to 350, with biodegradation rates varying between 0.05 % and 75 %, indicating a positive correlation between retardation and biodegradation. The detection of biodegradation byproducts, including derivatives of phosphin, pyridine, and pyrazole, in the column leachate confirmed that biodegradation had occurred. Additionally, principal component analysis (PCA) revealed positive correlations among retardation, biodegradation, specific surface area (SSA), aldehyde/ketone groups, and bacterial count. These findings demonstrate the potential of biochar and hydrochar amendments to enhance OPP immobilization in contaminated soils, thereby reducing their leaching into groundwater. This study offers a comprehensive approach to the remediation of pesticide-contaminated soils, advancing both our fundamental understanding and the practical applications of environmental remediation techniques.

Cell viability assessment and ion release profiles of GICs modified with TiO2- and Mg-doped hydroxyapatite nanoparticles.

OBJECTIVES: To assess and compare the cell viability and ion release profiles of two conventional glass ionomer cements (GICs), Fuji IX and Ketac Molar EasyMix, modified with TiO2 and Mg-doped-HAp nanoparticles (NPs). METHODS: TiO2 NPs, synthesized via a sol-gel method, and Mg-doped hydroxyapatite, synthesized via a hydrothermal process, were incorporated into GICs at a concentration of 5 wt.%. The biocompatibility of prepared materials was assessed by evaluating their effects on the viability of dental pulp stem cells (DPSCs), together with monitoring ion release profiles. Statistical analysis was performed using One-way analysis of variance, with significance level p < 0.05. RESULTS: The addition of NPs did not significantly affect the biocompatibility of GICs, as evidenced by comparable decreased levels in cell viability to their original formulations. Distinct variations in cell viability were observed among Fuji IX and Ketac Molar, including their respective modifications. FUJI IX and its modification with TiO2 exhibited moderate decrease in cell viability, while other groups exhibited severe negative effects. While slight differences in ion release profiles were observed among the groups, significant variations compared to original cements were not achieved. Fluoride release exhibited an initial "burst release" within the initial 24 h in all samples, stabilizing over subsequent days. CONCLUSIONS: The addition of NPs did not compromise biocompatibility, nor anticariogenic potential of tested GICs. However, observed differences among FUJI IX and Ketac Molar, including their respective modifications, as well as induced low viability of DPSC by all tested groups, suggest the need for careful consideration of cement composition in their biological assessments. CLINICAL SIGNIFICANCE: The findings contribute to understanding the complex interaction between NPs and GIC matrices. However, the results should be interpreted recognizing the inherent limitations associated with in vitro studies. Further research avenues could explore long-term effects, in vivo performance, and potential clinical applications.

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 °C and three hydrochars produced at 180, 200, and 220 °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 (λ = 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 Rd 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 2023;19:933-942. © 2022 SETAC.