Structures and mechanisms in clay nanopore trapping of structurally-different fluoroquinolone antimicrobials

Assessing sorption of fluoroquinolone antibiotics in soils from a Kd compilation based on pure organic and mineral components

The presence of fluoroquinolone (FQ) antibiotics in soils may cause a threat to human health due to overexposure and the generation of antibiotic resistance genes. Understanding their sorption behavior in soils is important to predict subsequent FQ (bio) availability. Here, FQ sorption in pure soil organic (i.e., humic substances) and mineral (i.e., metal oxides; phyllosilicates) components is evaluated through a solid-liquid distribution coefficient (Kd (FQ)) dataset consisting of 243 entries originated from 80 different studies, to elucidate their respective contribution to the overall Kd (FQ) in bulk soils. First, different factors affecting FQ sorption and desorption in each of these soil phases are critically discussed. The strong role of pH in Kd (FQ), due to the simultaneous effect on both FQ speciation and surface charge changes, encouraged the derivation of normalized sorption coefficients for the cationic, zwitterionic and anionic FQ species in humic substances and in different phyllosilicates. Kd (FQ) in metal oxides revealed a key role of metal nature and material specific surface area due to complexation sorption mechanisms at neutral pH. Cumulative distribution functions (CDF) were applied to each dataset to establish a sorption affinity range for each phase and to derive best estimate Kd (FQ) values for those materials where normalized sorption coefficients to FQ species were unavailable. The data analysis conducted in the different soil phases set the basis for a Kd (FQ) prediction model, which combined the respective sorption affinity of each phase for FQ and phase abundance in soil to estimate Kd (FQ) in bulk soils. The model was subsequently validated with sorption data in well characterized soils compiled from the literature.

Adsorption of Ciprofloxacin on Clay Minerals in Argentinian Santa Rosa-Corrientes Soils

The presence of antibiotics in soils is increasing drastically in last decades due to the intensive farming industry and excessive human consumption. Clay minerals are one of the soil components with great adsorption capacity for organic pollutants. The study of interactions between antibiotics and mineral surfaces will give us scientific knowledge of these pollutants through soils. In this work, we study the adsorption of the antibiotic ciprofloxacin in the clay mineral fraction of soils from the Argentinian zone of Santa Rosa (Corrientes), in a collaborative research of experiments and atomistic modelling calculations of the intercalation of ciprofloxacin in the interlayer space of montmorillonite. Adsorption and desorption isotherms were performed and compared with different isotherm models. Additionally, enthalpy, entropy, and free energy were determined from equilibrium constants at a function of temperature. All these experiments and calculations lead to the conclusions that two adsorption types of ciprofloxacin are found on clay minerals: one weakly sorbed that is released during the desorption experiments, and other one strongly joined that remains in the soil.

A comprehensive and global evaluation of residual antibiotics in agricultural soils: Accumulation, potential ecological risks, and attenuation strategies

The occurrence of antibiotics in agricultural soils has raised concerns due to their potential risks to ecosystems and human health. However, a comprehensive understanding of antibiotic accumulation, distribution, and potential risks to terrestrial ecosystems on a global scale is still limited. Therefore, in this study, we evaluated the accumulation of antibiotics and their potential risks to soil microorganisms and plants, and highlighted the driving factors of antibiotic accumulation in agricultural soils based on 134 peer-reviewed studies (between 2000 and 2022). The results indicated that 56 types of antibiotics were detected at least once in agricultural soils with concentrations ranging from undetectable to over 7000 µg/kg. Doxycycline, tylosin, sulfamethoxazole, and enrofloxacin, belonging to the tetracyclines, macrolides, sulfonamides, and fluoroquinolones, respectively, were the most accumulated antibiotics in agricultural soil. The accumulation of TCs, SAs, and FQs was found to pose greater risks to soil microorganisms (average at 29.3%, 15.4%, and 21.8%) and plants (42.4%, 26.0%, and 38.7%) than other antibiotics. East China was identified as a hot spot for antibiotic contamination due to high levels of antibiotic concentration and ecological risk to soil microorganisms and plants. Antibiotic accumulation was found to be higher in vegetable fields (245.5 µg/kg) and orchards (212.4 µg/kg) compared to croplands (137.2 µg/kg). Furthermore, direct land application of manure resulted in a greater accumulation of TCs, SAs, and FQs accumulation in soils than compost fertilization. The level of antibiotics decreased with increasing soil pH and organic matter content, attributed to decreasing adsorption and enhancing degradation of antibiotics. In conclusion, this study highlights the need for further research on the impacts of antibiotics on soil ecological function in agricultural fields and their interaction mechanisms. Additionally, a whole-chain approach, consisting of antibiotic consumption reduction, manure management strategies, and remediation technology for soil contaminated with antibiotics, is needed to eliminate the potential environmental risks of antibiotics for sustainable and green agriculture.

Molecular Dynamics Simulation Prediction of the Partitioning Constants (KH, Kiw, Kia) of 82 Legacy and Emerging Organic Contaminants at the Water-Air Interface

The tendency of organic contaminants (OCs) to partition between different phases is a key set of properties that underlie their human and ecological health impacts and the success of remediation efforts. A significant challenge associated with these efforts is the need for accurate partitioning data for an ever-expanding list of OCs and breakdown products. All-atom molecular dynamics (MD) simulations have the potential to help generate these data, but existing studies have applied these techniques only to a limited variety of OCs. Here, we use established MD simulation approaches to examine the partitioning of 82 OCs, including many compounds of critical concern, at the water-air interface. Our predictions of the Henry's law constant (K_H) and interfacial adsorption coefficients (K_iw, K_ia) correlate strongly with experimental results, indicating that MD simulations can be used to predict K_H, K_iw, and K_ia values with mean absolute deviations of 1.1, 0.3, and 0.3 logarithmic units after correcting for systematic bias, respectively. A library of MD simulation input files for the examined OCs is provided to facilitate future investigations of the partitioning of these compounds in the presence of other phases.

Sorption of pharmaceuticals and personal care products on soil and soil components: Influencing factors and mechanisms

The sorption of pharmaceuticals and personal care products (PPCPs) on soil and soil components makes an important contribution to the fate, migration and bioavailability of PPCPs. Previous reviews have mostly focused on the sorption of PPCPs on single soil components (e.g., minerals and soil organic matter). However, the sorption of PPCPs within the whole soil system has not been systematically analyzed. This paper reviews the recent progress on PPCP sorption on soil and soil components. We have evaluated the sorption of a wide range of PPCPs in research fields that are usually considered in isolation (e.g., humic acids (HAs), montmorillonite, kaolinite, and goethite), and established a bridge between PPCPs and sorbent. The sorption mechanisms of PPCPs, e.g., cation exchange, surface complexation, electrostatic interaction and hydrogen bonding, are discussed and critically evaluated. We also assessed the influence of environmental factors (pH, ionic strength, organic matter and temperature) on sorption. This review summarizes the knowledge of PPCPs sorption on soil gained in recent years, which can provide new strategies for solving the problem of antibiotic pollution.

Glyphosate adsorption onto kaolinite and kaolinite-humic acid composites: Experimental and molecular dynamics studies

Glyphosate (PMG) has been the most widely used herbicide in the world, and its environmental mobility and fate are mainly controlled by interactions with mineral surfaces. In soil systems, kaolinite is typically associated with humic acids (HAs) in the form of mineral-HA complexes, and hence it is crucial to characterize the molecular-scale interactions that occur between PMG and kaolinite and kaolinite-HA complexes. Batch experiments, Fourier transform infrared spectrum (FTIR) and X-ray photoelectron spectroscopy (XPS), isothermal titration calorimetry (ITC), and molecular dynamics (MD) simulations were performed to decipher the molecular interactions between PMG and kaolinite and kaolinite-HA composites. Our results reveal that kaolinite-HA composites adsorb higher concentrations of PMG than does kaolinite alone, likely due to more adsorption sites existed on kaolinite-HA than on kaolinite. FTIR and XPS analysis reveal that the carboxyl, phosphonyl and amino groups of PMG interacted with kaolinite and kaolinite-humic acid via Hydrogen bonds. The ITC results and interaction energy calculations indicate that the adsorption of PMG onto the kaolinite-HA is more energetically favorable relative to that onto kaolinite. MD simulations suggest that the PMG molecule adsorbs parallel to the surface of kaolinite and the composites through hydrogen bonding. Humic acid increases the adsorption of PMG through the creation of H-bond networks between PMG, the kaolinite surface, and humic acid. The results from this study improve our molecular-level understanding of the interactions between PMG and two important components of soil systems, and hence yield valuable information for characterizing the fate and behavior of PMG in soil environments.

Molecular dynamics simulation of the adsorption of per- and polyfluoroalkyl substances (PFASs) on smectite clay

Molecular dynamics (MD) simulations are used to predict the partitioning of per- and polyfluoroalkyl substances (PFASs) to smectite clay, a high surface area adsorbent ubiquitous in temperate soils. Simulated systems model a stack of flexible smectite lamellae in contact with a bulk aqueous reservoir containing PFAS molecules. Perfluorobutanesulfonic acid (PFBS), perfluorohexanesulfonic acid (PFHxS), and perfluorooctanesulfonic acid (PFOS) are simulated at various aqueous chemistry conditions to examine the effect of PFAS size, salinity, and coordinating cation type (K⁺, Na⁺, and Ca²⁺) on adsorption. The metadynamics technique is employed to facilitate the exploration of the simulation cell and to reconstruct the underlying free energy landscape. Adsorption is favorable on the hydrophobic domains of the external basal surfaces with the fluorinated chain adopting a flat orientation on the surface. Analysis of the adsorption energetics reveals large favorable entropic contributions to adsorption. The enthalpy of adsorption is unfavorable, though much less so in the presence of Ca²⁺ due to stabilizing 'lateral cation bridging' interactions between divalent cations and PFAS sulfonate head groups. Overall, this research advances the mechanistic understanding of PFAS-smectite interactions and provides new insights that could help inform fate and transport models and the development of adsorbents and remediation techniques.

Competitive adsorption of tetracycline, oxytetracycline and chlortetracycline on soils with different pH value and organic matter content

Antibiotics spread into the environment can cause soil and water degradation. Specifically, tetracycline antibiotics (TCs) are among those most consumed in veterinary medicine, and near 90% of the doses administered to animals are excreted as original compounds, due to poor absorption. In this study we investigated competitive soil adsorption/desorption for three tetracycline antibiotics (tetracycline: TC, oxytetracycline: OTC, and chlortetracycline: CTC), usually spread on soils by slurry fertilization, affecting to soil degradation due to chemical pollution. The study was carried out on six soils selected according to their pH values (4.49-7.06), and organic matter contents (1.07-10.92%). The competitive experiments were performed in ternary systems (adding all three TCs simultaneously, using five equal and increasing concentrations, from 17 to 200 μmol L^-1). The results were compared with those obtained in simple systems (adding individual antibiotics separately), for the same final concentration (in this case, 200 μmol L^-1) and for different concentrations (200 μmol L^-1 in the simple systems, versus 600 μmol L^-1 in the ternary systems, resulting from the sum of 200 μmol L^-1 of each of the three antibiotics). In all cases, batch-type adsorption/desorption experiments were carried out, with 24 h as contact time. Those soils with higher organic matter content adsorbed 100% of the TCs, with desorption being always lower than 3%. In soils with less organic matter, adsorption decreased as the dose of added antibiotic increased, due to competition for adsorption sites. CTC was the most retained among the three TCs (up to 20% more than the other when high doses of antibiotic were added). In the simple systems, percentage adsorption was always high (>85%) for the three TCs; however, percentage adsorption decreased in the ternary systems, reaching just 65% and 40% (for equal and different ionic strength, respectively) in soils with low organic matter contents. These results show the environmental and public health relevance of competition among the three TCs. In fact, the highest risk of entering the food chain takes place when these antibiotics are spread together on soils with low organic matter content, especially in the case of TC and CTC, which are the least adsorbed and the most desorbed molecules.

Cation-group interaction as the predominant force for adsorption of substituted dinitrobenzenes by smectite clays

Elucidation of the interaction between NACs and smectites is important to the understanding of the potential for transport of nitroaromatic compounds (NACs) in soils and to implementation of NAC-contaminated soil remediation. The adsorption of dinitrotoluene isomers (DNTs) and substituted dinitrobenzenes (SDNBs) by smectite was determined by batch equilibration and characterized by FTIR and XPS, along with molecular dynamics simulations. The adsorption of DNTs differed substantially among the isomers, attributed to the overall degree of nitro deflection relative to the aromatic ring plane. The substituents in SDNBs strengthened the electrostatic interaction between smectite K⁺ and nitro groups, facilitating SDNB adsorption to smectite. The competition between 2,4-DNT and 1,3-DNB, as well as the inclusion complexation of K⁺ by crown ether 18c6e, both reduced 2,4-DNT adsorption to smectite by weakening the K⁺-nitro interaction. All the results demonstrated that the electrostatic interaction between smectite K⁺ and nitro of NACs was the predominant force in mediating their adsorption. This was supported by FTIR spectra that the N-O bands shifted due to the weakening of N-O bonds and strengthening of C-N bonds via the electron transfer to cations. The XPS of smectite further manifested the cation-nitro interactions that the binding energies of K 2p 1/2, K 2p 3/2, and Si 2p shifted higher with 1,3-DNB adsorbed. Molecular dynamics simulations indicated the aromatic planes of 2,4-DNP and 2,4-DNAs were parallel to the basal plane of smectite and the oxygens of nitro groups in the molecules were directly coordinated with smectite K⁺.

Abiotic phosphorus recycling from adsorbed ribonucleotides on a ferrihydrite-type mineral: Probing solution and surface species

Iron (Fe) (oxyhydr)oxide minerals, which are amongst most reactive minerals in soils and sediments, are known to exhibit strong adsorption of inorganic phosphate (P_i) and organophosphate (P_o) compounds. Beyond synthetic P_o compounds, much still remains unknown about the reactivity of these minerals to transform naturally-occurring P_o compounds to P_i, particularly with respect to solution versus surface speciation of P_o hydrolysis. To investigate this reactivity with a ferrihydrite-type mineral and ribonucleotides, we employed high-resolution liquid chromatography-mass spectrometry (LC-MS), X-ray absorption near-edge structure (XANES), Fourier-transform infrared (FTIR) spectroscopy, and molecular modeling. Kinetic experiments were conducted with the mineral (1 g L^-1) reacted with adenosine monophosphate, diphosphate, or triphosphate (respectively AMP, ADP, ATP; 50 µM). Analysis of solution organic species by LC-MS implied that only adsorption occurred with AMP and ADP but both adsorption and dephosphorylation of ATP were evident. Maximum adsorption capacities per gram of mineral were 40.6 ± 0.8 µmol AMP, 35.7 ± 1.6 µmol ADP, and 10.9 ± 1.0 µmol ATP; solution dephosphorylated by-products accounted for 15% of initial ATP. Subsequent XANES analysis of the surface species revealed that 16% of adsorbed AMP and 30% of adsorbed ATP were subjected to dephosphorylation, which was not fully quantifiable from the solution measurements. Molecular simulations predicted that ADP and ATP were complexed mainly via the phosphate groups whereas AMP binding also involved multiple hydrogen bonds with the adenosine moiety; our FTIR data confirmed these binding confirmations. Our findings thus imply that specific adsorption mechanisms dictate the recycling and subsequent trapping of P_i from ribonucleotide-like biomolecules reacted with Fe (oxyhydr)oxide minerals.

Antibiotics bioremediation: Perspectives on its ecotoxicity and resistance

Antibiotic is one of the most significant discoveries and have brought a revolution in the field of medicine for human therapy. In addition to the medical uses, antibiotics have broad applications in agriculture and animal husbandry. In developing nations, antibiotics use have helped to increase the life expectancy by lowering the deaths due to bacterial infections, but the risks associated with antibiotics pollution is largely affecting people. Since antibiotics are released partially degraded and undegraded into environment creating antibiotic pollution, and its bioremediation is a challenging task. In the present review, we have discussed the primary antibiotic sources like hospitals, dairy, and agriculture causing antibiotic pollution and their innovative detection methods. The strong commitment towards the resistance prevention and participation, nations through strict policies and their implementations now come to fight against the antibiotic resistance under WHO. The review also deciphers the bacterial evolution based strategies to overcome the effects of antibiotics, so the antibiotic degradation and elimination from the environment and its health benefits. The present review focuses on the environmental sources of antibiotics, it's possible degradation mechanisms, health effects, and bacterial antibiotics resistance mechanisms.

Adsorption characteristics of oxytetracycline by different fractions of organic matter in sedimentary soil

Sedimentary soil was selected as the original sample (SOS). The adsorption fractions were obtained by the removal of dissolved organic matter (SRDOM), removal of minerals (SRM), removal of free fat (SRLF), and removal of nonhydrolyzable organic carbon (SNHC) respectively to investigate the adsorption characteristic of oxytetracycline (OTC) by different fractions of organic matter in sedimentary soil. The adsorption mechanism was investigated by elemental analysis, infrared spectra, and UV-visible spectroscopy. The results showed that the DOM in the sedimentary soil inhibited the adsorption of OTC, but the adsorption of different fractions of organic matter was quite different. The sorption kinetics of OTC were fitted to the pseudo-second-order model and the adsorption capacity of each fraction was: SNHC≈SRDOM > SOS > SRLF> SRM. The adsorption processes of OTC by different fractions were spontaneous. Alkaline pH condition had an effect on the adsorption of four fractions except for SNHC, while neutral and acidic pH affects SOS and SRDOM more obviously, the SNHC fraction was almost free from pH varies. Mechanism analysis showed that the main factors determining the adsorption capacity were the aromaticity and polarity of organic matter fractions. For the organic matter-based fractions (SRM, SRLF, and SNHC), the adsorption coefficient was positively correlated with the aromaticity. Furthermore, for SOS and SRDOM based on inorganic minerals, it was not only related to aromaticity, but also the content and composition of inorganic minerals.