Interactions of 15N-Sulfadiazine and Soil Components As Evidenced by 15N-CPMAS NMR

Effect of Cu2+ on the Laccase-Inducted Formation of Non-Extractable Residues of Tetrabromobisphenol A in Humic Acids

We used ¹⁴ C-radiolabelling to study the non-extractable residues (NERs) formation of tetrabromobisphenol A (TBBPA) in a humic acid (HA) suspension under catalysis of laccase in the presence of copper. When entering the suspension after TBBPA adsorbing to HA supramolecular associates, Cu²⁺ at low concentrations (even without toxicity to laccase) significantly reduced the amount and first-order kinetic constant of the NER formation, while Cu²⁺ had no significant effect on the formation after it was complexed with HA. The inhibition effect of Cu²⁺ on the NER formation is explained to be attributed to the prevention of laccase-induced oxidation of TBBPA in the voids of HA associates by complexation of Cu²⁺ with periphery molecules of the associates. The results provide insights into varying effects of heavy metals on the environmental fate of organic contaminants and suggest that co-existing heavy metals could increase their environmental risk by reducing their NER formation.

Interaction of Antibiotics and Humic Substances: Environmental Consequences and Remediation Prospects

The occurrence and distribution of antibiotics in the environment has received increasing attention due to their potential adverse effects on human health and ecosystems. Humic substances (HS) influence the mobility, reactivity, and bioavailability of antibiotics in the environment significantly due to their interaction. As a result, HS can affect the dissemination of antibiotic-resistance genes, which is one of the main problems arising from contamination with antibiotics. The review provides quantitative data on the binding of HS with fluoroquinolones, macrolides, sulfonamides, and tetracyclines and reports the proposed mechanisms of their interaction. The main issues of the quantification of antibiotic-HS interaction are discussed, which are a development of standard approaches and the accumulation of a dataset using a standard methodology. This would allow the implementation of a meta-analysis of data to reveal the patterns of the binding of antibiotics to HS. Examples of successful development of humic-based sorbents for fluoroquinolone and tetracycline removal from environmental water systems or polluted wastewaters were given. Data on the various effects of HS on the dissemination of antibiotic-resistance genes (ARGs) were summarized. The detailed characterization of HS properties as a key point of assessing the environmental consequences of the formation of antibiotic-HS complexes, such as the dissemination of antibiotic resistance, was proposed.

Formation and nature of non-extractable residues of emerging organic contaminants in humic acids catalyzed by laccase

Formation of non-extractable residues (NERs) is the major fate of most environmental organic contaminants in soil, however, there is no direct evidence yet to support the assumed physical entrapment of NERs (i.e., type I NERs) inside soil humic substances. Here, we used ¹⁴C-radiotracer and silylation techniques to analyze NERs of six emerging and traditional organic contaminants formed in a suspension of humic acids (HA) under catalysis of the oxidative enzyme laccase. Laccase induced formation of both type I and covalently bound NERs (i.e., type II NERs) of bisphenol A, bisphenol F, and tetrabromobisphenol A to a large extent, and of bisphenol S (BPS) and sulfamethoxazole (SMX) to a less extent, while no induction for phenanthrene. The type I NERs were formed supposedly owing to laccase-induced alteration of primary (active groups) and secondary (conformation) structure of humic supramolecules, contributing surprisingly to large extents (23.5%-65.7%) to the total NERs, particularly for BPS and SMX, which both were otherwise not transformed by laccase catalysis. Electron-withdrawing sulfonyl group and bromine substitution significantly decreased amount and kinetics of NER formation, respectively. This study provides the first direct evidence for the formation of type I NERs in humic substances and implies a "Trojan horse" effect of such NERs in the environment.

Synthesis of typical sulfonamide antibiotics with [14C]- and [13C]-labeling on the phenyl ring for use in environmental studies

BACKGROUND

Due to their widespread use, sulfonamide antibiotics (SAs) have become ubiquitous environmental contaminants and thus a cause of public concern. However, a complete understanding of the behavior of these pollutants in complex environmental systems has been hampered by the unavailability and high cost of isotopically labeled SAs.

RESULTS

Using commercially available uniformly [¹⁴C]- and [¹³C]-labeled aniline as starting materials, we synthesized [phenyl-ring-¹⁴C]- and [phenyl-ring-¹³C]-labeled sulfamethoxazole (SMX), sulfamonomethoxine (SMM), and sulfadiazine (SDZ) in four-step (via the condensation of labeled N-acetylsulfanilyl chloride and aminoheterocycles) or five-step (via the condensation of labeled N-acetylsulfonamide and chloroheterocycles) reactions, with good yields (5.0-22.5% and 28.1-54.1% for [¹⁴C]- and [¹³C]-labeled SAs, respectively) and high purities (> 98.0%).

CONCLUSION

The synthesis of [¹⁴C]-labeled SAs in milligram amounts enables the preparation of labeled SAs with high specific radioactivity. The efficient and feasible methods described herein can be applied to the production of a variety of [¹⁴C]- or [¹³C]-labeled SAs for studies on their environmental behavior, including the fate, transformation, and bioaccumulation of these antibiotics in soils and aqueous systems.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s12302-022-00598-z.

Interaction kinetics and accessibility of sulfadiazine in model clay-humic acid suspension: Electron spin resonance investigations with nitroxide spin label

The characterization of the interaction of sulfonamides with soil is of particular interest in environmental risk and persistence assessment. In the present work electron spin resonance spectroscopy (ESR) was used to investigate the interaction kinetics of spin labelled sulfadiazine (SL-SDZ) with model clay-humic acid suspensions. The ESR spectra showed that SL-SDZ incubated with Leonardite humic acid (LHA) and Ca-hectorite as model clay was immobilized due to covalent binding of its aniline moiety to LHA. From the immobilization kinetics measured over a period of 1200 h a pseudo-first order reaction with a time constant of 82.6 ± 25.0 h of covalent binding was determined. Additionally, SL-SDZ was strongly sorbed by LHA immediately after incubation but not durably sequestered. Compared to incubation without Ca-hectorite the covalent binding kinetics of SL-SDZ as well as its strong sorption were retarded.

NMR spectroscopy of wastewater: A review, case study, and future potential

NMR spectroscopy is arguably the most powerful tool for the study of molecular structures and interactions, and is increasingly being applied to environmental research, such as the study of wastewater. With over 97% of the planet's water being saltwater, and two thirds of freshwater being frozen in the ice caps and glaciers, there is a significant need to maintain and reuse the remaining 1%, which is a precious resource, critical to the sustainability of most life on Earth. Sanitation and reutilization of wastewater is an important method of water conservation, especially in arid regions, making the understanding of wastewater itself, and of its treatment processes, a highly relevant area of environmental research. Here, the benefits, challenges and subtleties of using NMR spectroscopy for the analysis of wastewater are considered. First, the techniques available to overcome the specific challenges arising from the nature of wastewater (which is a complex and dilute matrix), including an examination of sample preparation and NMR techniques (such as solvent suppression), in both the solid and solution states, are discussed. Then, the arsenal of available NMR techniques for both structure elucidation (e.g., heteronuclear, multidimensional NMR, homonuclear scalar coupling-based experiments) and the study of intermolecular interactions (e.g., diffusion, nuclear Overhauser and saturation transfer-based techniques) in wastewater are examined. Examples of wastewater NMR studies from the literature are reviewed and potential areas for future research are identified. Organized by nucleus, this review includes the common heteronuclei (¹³C, ¹⁵N, ¹⁹F, ³¹P, ²⁹Si) as well as other environmentally relevant nuclei and metals such as ²⁷Al, ⁵¹V, ²⁰⁷Pb and ¹¹³Cd, among others. Further, the potential of additional NMR methods such as comprehensive multiphase NMR, NMR microscopy and hyphenated techniques (for example, LC-SPE-NMR-MS) for advancing the current understanding of wastewater are discussed. In addition, a case study that combines natural abundance (i.e. non-concentrated), targeted and non-targeted NMR to characterize wastewater, along with in vivo based NMR to understand its toxicity, is included. The study demonstrates that, when applied comprehensively, NMR can provide unique insights into not just the structure, but also potential impacts, of wastewater and wastewater treatment processes. Finally, low-field NMR, which holds considerable future potential for on-site wastewater monitoring, is briefly discussed. In summary, NMR spectroscopy is one of the most versatile tools in modern science, with abilities to study all phases (gases, liquids, gels and solids), chemical structures, interactions, interfaces, toxicity and much more. The authors hope this review will inspire more scientists to embrace NMR, given its huge potential for both wastewater analysis in particular and environmental research in general.

Applications of solid-state NMR spectroscopy in environmental science

Environmental science is an interdisciplinary field, which integrates chemical, physical, and biological sciences to study environmental problems and human impact on the environment. This article highlights the use of solid-state NMR spectroscopy (SSNMR) in studies of environmental processes and remediation with examples from both laboratory studies and samples collected in the field. The contemporary topics presented include soil chemistry, environmental remediation (e.g., heavy metals and radionuclides removal, carbon dioxide mineralization), and phosphorus recovery. SSNMR is a powerful technique, which provides atomic-level information about speciation in complex environmental samples as well as the interactions between pollutants and minerals/organic matter on different environmental interfaces. The challenges in the application of SSNMR in environmental science (e.g., measurement of paramagnetic nuclei and low-gamma nuclei) are also discussed, and perspectives are provided for the future research efforts.

Pedotransfer functions to estimate the adsorption and desorption of sulfadiazine in agricultural soils

Batch-type experiments were used to study adsorption-desorption of sulfadiazine in 50 crop soils exposed to antibiotic pollution due to the spreading of animal manure or slurry. Adsorption and desorption curves were linear, and were satisfactorily described using the linear and Freundlich equations. The Freundlich adsorption constant (K_F(ad)) showed low values (between 0.4 and 9.0 L^1/n μmol^1-1/n kg^-1), which were similar to those of the adsorption constant for the linear model (K_d(ad), between 0.3 and 12.0 L kg^-1). Furthermore, the desorption constant for the linear model (K_d(des)) showed higher values than those of K_d(ad), ranging between 1.6 and 29.3 L kg^-1, while the values of the Freundlich desorption constant (K_F(des)) ranged from 0.10 to 36.8 L^1/n μmol^1-1/n kg^-1. The percentages of adsorption were very variable, ranging from 10 to 87%. The soil characteristics that most influenced adsorption-desorption were those related to soil organic matter (organic carbon and nitrogen contents), as well as the effective cation exchange capacity, and pH. In addition, statistically robust pedotransfer functions were obtained, allowing prediction of adsorption-desorption behavior for sulfadiazine from readily determinable soil parameters, such as pH or organic carbon content.