Estimation of adsorption/desorption Freundlich's affinity coefficients for oxytetracycline and chlortetracycline from soil properties: Experimental data and pedotransfer functions

Research on environmental aspects of retention/release of pollutants in soils and sorbents. What should be next?

Although studies dealing with adsorption/desorption (and/or retention/release) of pollutants present in environmental compartments is a classical field of research, recent papers are focusing on some weak points of investigations and publications within the area. In addition, an increasing number of works are being published related to new possibilities and alternatives in this kind of research works, many of them in relation to the use of artificial intelligence (AI). Considering the existence of eventual controversies, eventual mistakes, and the convenience of suggesting alternatives to go ahead in the future, in this work, after taking into account some relevant publications in the previous literature, a simple workflow is proposed as a kind of protocol to revise successive steps that could guide the direction to follow when programing research dealing with the retention/release of pollutants in soils and sorbent materials.

Migration of nanocolloid-carrying antibiotics in paddy red soil during the organic fertilization process

Soil nanocolloids are highly mobile and can act as carriers for the transport of antibiotics to a wider and deeper range of soils; however, the inherent behavior and mechanism of nanocolloid-carrying antibiotics in soil remain unclear. In this study, we conducted a comprehensive investigation of the migration of antibiotics in paddy red soil during the organic fertilization process using four common soil nanocolloids: kaolin (KL), montmorillonite (MT), hematite (HT), and humic acid (HA). The results showed that nanocolloid carriers promoted the intra-medium (from soil surface to the bottom) and inter-medium transfer (from organic fertilizers to soil) of antibiotics. The migration mechanisms of antibiotics carried by the nanocolloids differed: the phenolic hydroxyl and carboxyl groups of HA esterified with the carboxyl groups of quinolones and phenolic hydroxyl groups of tetracyclines, respectively, while the oxygen atoms of HT formed stabilizing complexes with the soil, which could further adsorb antibiotics using their functional group-rich complexes. Smaller antibiotic compounds were adsorbed in the metal oxide interlayer of MT via cation exchange, whereas KL adsorbed antibiotics on its metal oxide surface layer in the same way but were susceptible to desorption. Additionally, nanocolloids changed the adsorption capacity of soil for antibiotics and influenced the enrichment of dominant/functional bacteria (e.g., Burkholderiaceae) and thus varied the vertical distribution of antibiotics in soil. These findings enhance our understanding of the migration behavior and mechanism of nanocolloid-carrying antibiotics in red paddy soil and provide a theoretical foundation for preventing and controlling antibiotic pollution in arable systems.

Sorption and desorption of naphthenic acids on reclamation materials: Mechanisms and selectivity of naphthenic acids from oil sands process water

This study investigated the application of materials peat-mineral mix (PT) and Pleistocene fluvial sands from different location (PF-1 and PF-2) obtained from surface mining of oil sands as sorbents of naphthenic acids (NAs) from oil sands process water (OSPW). To understand the sorption properties and mechanisms of NAs in the materials, sorption and desorption studies were performed using decanoic acid (DA) and 5-phenylvaleric acid (PVA). Additionally, the removal efficiency was evaluated using real OSPW to understand the effect of NA structure on sorption. Equilibrium of DA and PVA was reached at 2 days for PT, and 3 and 6 days for PF materials, respectively. Langmuir isotherm best fitted the equilibrium data. Maximum sorption capacities for DA and PVA were, respectively, 16.8 × 10³ and 10⁴ mg/kg for PT, 142.9 and 81.3 mg/kg for PF-1, and 600 and 476.2 mg/kg for PF-2. Hydrophobic interactions, hydrogen bonding, and π-π interaction were the main sorption mechanisms. Desorption of model compounds from post-sorption materials was not observed for 14 days. The removal of NAs from real OSPW ranged from 20 to 54%. PT is the most promising sorbent of NAs from OSPW because it partially removed NAs with a wide range of molecular weights and structures at very low dosage. Sorption of NAs was affected by the total organic carbon of the materials, emphasizing the hydrophobic interaction as an important sorption mechanism. The results suggest that some mobility of NAs is expected to take place if the reclamation materials come in contact with OSPW, which might occur in an oil sands reclamation landscape.

The roles of Fe oxyhydroxide coating and chemical aging in pyrogenic carbon nanoparticle transport in unsaturated porous media

Pyrogenic carbon (PyC) nanoparticles are widespread in the environment, which is important to global carbon cycle. PyC can exist for millions of years and undergo various environmental aging processes. To better understand the roles of Fe oxyhydroxides and water content on the pristine and aged PyC transport, adsorption and column experiments were conducted under three saturations (100%, 70%, and 40%) and three pH (5, 7, and 9) in both clean and Fe oxyhydroxide-coated sand. At high water saturations (100% and 70%), the mobility of both the pristine and aged PyC was enhanced at high pH due to strong electrostatic repulsion, and the aged PyC showed higher mobility than the pristine PyC because of its more negative charge and hydrophilic surface. The coating of Fe oxyhydroxides on sand decreased the mobility of both the pristine and aged PyC due to weak electrostatic repulsion, large specific surface area, and high roughness. At low saturation (40%), solution pH showed little effect on both the pristine and aged PyC mobility, and water saturation became the main factor affecting PyC mobility. Almost no pristine or aged PyC transported out from the Fe oxyhydroxide-coated sand column because Fe oxide increased the roughness of the sand surface, which led to a sharp increase in the air-water-solid interface and retention sites. This study demonstrates that water content, environmental aging, and Fe oxyhydroxides are significant in the fate and transport of PyC nanoparticles in environments, which provides a good fundamental understanding for the assessment of pyrogenic carbon application in environmental protection and carbon sequestration.

New Models for Estimating the Sorption of Sulfonamide and Tetracycline Antibiotics in Soils

Sulfonamides (SAs) and tetracyclines (TCs) are two classes of widely used antibiotics. There is a lack of easy models for estimating the parameters of antibiotic sorption in soils. In this work, a dataset of affinity coefficients (Kf and Kd) of seven SA/TC antibiotics (i.e., sulfachlorpyridazine, sulfamethazine, sulfadiazine, sulfamethoxazole, oxytetracycline, tetracycline, and chlortetracycline) and associated soil properties was generated. Correlation analysis of these data showed that the affinity coefficients of the SAs were predominantly affected by soil organic matter and cation exchange capacity, while those of the TCs were largely affected by soil organic matter and pH. Pedotransfer functions for estimating Kf and Kd were built by multiple linear regression analysis and were satisfactorily validated. Their performances would be better for soils having higher organic matter content and lower pH. These pedotransfer functions can be used to aid environmental risk assessment, prioritization of antibiotics and identification of vulnerable soils.

Individual and combined contamination of oxytetracycline and cadmium inhibited nitrification by inhibiting ammonia oxidizers

INTRODUCTION

The large-scale development of animal husbandry and industrialization lead to more and more serious co-contamination from heavy metals and antibiotics in soils. Ecotoxic effects of residues from antibiotics and heavy metals are of increasing concern.

MATERIALS AND METHODS

In this study, oxytetracycline (OTC) and cadmium (Cd) were selected as target pollutants to evaluate the individual and combined effects on nitrification process using four different soil types sampled from North to South China through a 56-day incubation experiment.

RESULTS AND DISCUSSION

The results demonstrated that the contaminations of OTC and Cd, especially combined pollution had significant inhibitory effects on net nitrification rates (NNRs) as well as on AOA and AOB abundance. The toxic effects of contaminants were greatly enhanced with increasing OTC concentration. AOB was more sensitive than AOA to exogenous contaminants. And the interaction effects of OTC and Cd on ammonia oxidizers were mainly antagonistic. Furthermore, Cd contaminant (with or without OTC) had indirect effects on nitrification activity via inhibiting mineral N and AOA/AOB, while OTC alone indirectly inhibited nitrification activity by inhibiting ammonia oxidizers. The results could provide theoretical foundation for exploring the eco-environmental risks of antibiotics and heavy metals, as well as their toxic effects on nitrification processes.

Translating wastewater reuse for irrigation from OECD Guidelines: Tramadol sorption and desorption in soil-water matrices

Treated and untreated wastewater is often used for agricultural irrigation and, despite the many benefits of this practice, it poses the risk of biologically active chemical pollutants (such as pharmaceuticals, like tramadol) entering the environment. The partitioning of tramadol between soil/water at environmentally relevant concentrations is important to understand its environmental toxicity. Kinetics and isotherm sorption studies based on the Organisation for Economic Cooperation and Development (OECD) 106 Guideline were undertaken, ensuring comparability to previous studies. Studies were undertaken in three soils of different characteristics using aqueous concentrations of tramadol from 500 ng L^-1 (environmentally relevant) to 100 μg L^-1 (comparable to previous studies). Two of the soils presented a significantly (p < 0.05) higher sorption at a lower initial tramadol concentration (5000 ng L^-1), compared to 20,000 ng L^-1. Hysteresis was observed in all studied soils, indicating the accumulation of tramadol. Higher sorption to soils correlated with higher clay content, with soil/water partitioning coefficients (K_d) of 5.5 ± 13.3, 2.5 ± 3.8 and 0.9 ± 3.0 L kg¹ for soils with clay contents of 41.9%, 24.5% and 7.4%, respectively. Cation exchange was proposed as the main sorption mechanism for tramadol to soils when the pH was below tramadol's pK_a values (9.41 and 13.08). A comparative kinetics study between tramadol in soil/calcium chloride buffer and soil/wastewater effluent demonstrated significantly higher (p < 0.05) tramadol sorption to soil from wastewater effluent. This has the environmental implication that clay soils will be able to retain tramadol from irrigation water, despite the organic content of the irrigation water. Therefore, our studies show that tramadol soil sorption is likely to be higher in agricultural environments reusing wastewater than that predicted from experiments using the OECD 106 Guideline calcium chloride buffer.

Meta-analysis and machine learning to explore soil-water partitioning of common pharmaceuticals

The first meta-analysis and modelling from batch-sorption literature studies of the soil/water partitioning of pharmaceuticals is presented. Analysis of the experimental conditions reported in the literature demonstrated that though batch-sorption studies have value, they are limited in evaluating partitioning under environmentally-relevant conditions. Recommendations are made to utilise environmental relevant pharmaceutical concentrations, perform batch-sorption studies at temperatures other than 4, 20 and 25 °C to better reflect climate diversity, and utilise the Guideline 106 methodology as a benchmark to enable comparison between future studies (and support modelling and prediction). The meta-dataset comprised 82 data points, which were modelled using multivariate analysis; where K_d (soil/water partitioning coefficient) was the independent variable. The dependent variables fit into three categories: 1) pharmaceutical studied (including physical-chemical properties), 2) soil characteristics and 3) experimental conditions. The pharmaceutical solubility, the soil/liquid equilibration time (prior to adding the pharmaceutical), the soil organic carbon, the soil sterilisation method and the liquid phase were found to be significantly important variables for predicting K_d.

Research status and development of microbial induced calcium carbonate mineralization technology

In nature, biomineralization is a common phenomenon, which can be further divided into authigenic and artificially induced mineralization. In recent years, artificially induced mineralization technology has been gradually extended to major engineering fields. Therefore, by elaborating the reaction mechanism and bacteria of mineralization process, and summarized various molecular dynamics equations involved in the mineralization process, including microbial and nutrient transport equations, microbial adsorption equations, growth equations, urea hydrolysis equations, and precipitation equations. Because of the environmental adaptation stage of microorganisms in sandy soil, their reaction rate in sandy soil environment is slower than that in solution environment, the influencing factors are more different, in general, including substrate concentration, temperature, pH, particle size and grouting method. Based on the characteristics of microbial mineralization such as strong cementation ability, fast, efficient, and easy to control, there are good prospects for application in sandy soil curing, building improvement, heavy metal fixation, oil reservoir dissection, and CO₂ capture. Finally, it is discussed and summarized the problems and future development directions on the road of commercialization of microbial induced calcium carbonate precipitation technology from laboratory to field application.

Ciprofloxacin and Trimethoprim Adsorption/Desorption in Agricultural Soils

The current research focuses on the adsorption/desorption characteristics of the antibiotics ciprofloxacin (CIP) and trimethoprim (TRI) taking place in 17 agricultural soils, which are studied by means of batch-type experiments. The results show that adsorption was higher for CIP, with Freundlich K_F values ranging between 1150 and 5086 Lⁿ µmol¹⁻ⁿ kg⁻¹, while they were between 29 and 110 Lⁿ µmol¹⁻ⁿ kg⁻¹ in the case of TRI. Other parameters, such as the Langmuir maximum adsorption capacity (q_m(ads)), as well as the K_d parameter in the linear model and also the adsorption percentages, follow the same trend as K_F. Desorption was lower for CIP (with K_F(des) values in the range 1089–6234 Lⁿ µmol¹⁻ⁿ kg⁻¹) than for TRI (with K_F(des) ranging between 26 and 138 Lⁿ µmol¹⁻ⁿ kg⁻¹). The higher irreversibility of CIP adsorption was also confirmed by its lower n_F(des)/n_F(ads) ratios, compared to TRI. Regarding soil characteristics, it was evidenced that nitrogen and carbon contents, as well as mineral fractions, had the highest influence on the adsorption/desorption process. These results can be considered relevant as regards the fate of both antibiotics when they reach the environment as pollutants and therefore could be considered in assessment procedures focused on environmental and public health aspects.

Experimental Data and Modeling the Adsorption-Desorption and Mobility Behavior of Ciprofloxacin in Sandy Silt Soil

The improved understanding of the behavior of antibiotics in soil is of great importance due to their environmental hazard and frequent detection. In this work, the adsorption-desorption and mobility behaviors of ciprofloxacin in sandy silt soil, affecting the fate of ciprofloxacin in the environment, were studied by a series of batch tests and column tests. In batch tests, the effects of contact time, initial ciprofloxacin concentration, sandy silt soil dosage, solution pH, and ionic strength on ciprofloxacin adsorption and desorption in sandy silt soil were considered. Adsorption results were satisfactorily modeled, with good fittings to the pseudo-second-order model (R2 > 0.999) and Langmuir model (R2 > 0.991), with the value for Langmuir’s maximum adsorption capacity (qm) 5.50 mg g−1. Ciprofloxacin adsorption decreased sharply by increasing the pH from 7.0 to 10.0 and the ionic strength from 0.01 to 0.2 mol L−1 CaCl2. Comparatively, ciprofloxacin was more readily desorbed from sandy silt soil at alkaline and high ionic strength conditions. Breakthrough curves of ciprofloxacin obtained from the column experiments were described by the two-site model, Thomas model, and Yan mode. Of these models, the two-site model was the most suitable to describe the mobility of ciprofloxacin. The retardation factor (R) obtained in the two-site model was 345, suggesting strong adsorption affinity with ciprofloxacin on the sandy silt soil surface. The results from the Thomas model suggested the extremely small external and internal diffusion resistances. The Yan model was not suitable. Cation exchange interaction, electrostatic interaction, mechanical resistance, entrapment between porous media, and gravity sedimentation were proposed to be the important adsorption mechanisms.

Adsorption Properties and Mechanism of Attapulgite to Graphene Oxide in Aqueous Solution

In order to remove toxic graphene oxide (GO) from aqueous solution, attapulgite (ATP) was used as adsorbent to recycle it by adsorption. In this paper, the effects of different pH, adsorbent mass, GO concentration, time and temperature on the adsorption of GO by attapulgite were studied, and the adsorption performance and mechanism were further explored by XRD, AFM, XPS, FTIR, TEM and SEM tests. The results show that when T = 303 K, pH = 3, and the GO concentration is 100 mg/L in 50 mL of aqueous solution, the removal rate of GO by 40 mg of attapulgite reaches 92.83%, and the partition coefficient K_d reaches 16.31. The adsorption kinetics results showed that the adsorption equilibrium was reached at 2160 min, and the adsorption process could be described by the pseudo-second-order adsorption equation, indicating that the adsorption process was accompanied by chemical adsorption and physical adsorption. The isotherm and thermodynamic parameters show that the adsorption of GO by attapulgite is more consistent with the Langmuir isotherm model, and the reaction is a spontaneous endothermic process. The analysis shows that attapulgite is a good material for removing GO, which can provide a reference for the removal of GO in an aqueous environment.

Cotransport of micro- and nano-plastics with chlortetracycline hydrochloride in saturated porous media: Effects of physicochemical heterogeneities and ionic strength

Global production and use of plastics have resulted in the wide dissemination of micro- and nano-plastics (MNPs) to the natural environment. Potentially acting as a vector, the role of MNPs on the fate and transport of environmental pollutants (e.g., antibiotics such as chlortetracycline hydrochloride; CTC) has garnered global concern recently. Herein, the cotransport of MNPs and CTC in columns packed with uncoated sand or soil colloid-coated sand (SCCS) under different degrees of physicochemical heterogeneity and ionic strength was systematically explored. Our results show that MNPs and CTC inhibit the transport of each other when they coexist. The adsorption of CTC onto sand grains, soil colloids, and MNPs, as well as the aggregation of MNPs in the presence of CTC could be the major contributors to the enhanced retention of CTC and MNPs. In SCCS with different degrees of soil colloid coating, the adsorption of CTC on soil colloids is critical to influence the transport of CTC, and the nonlinear retention of MNPs to soil colloids is mainly attributed to the alteration of collector surface roughness by soil colloids. High ionic strength slightly facilitates CTC transport due to the competition for adsorption sites and the formation of CTC macromolecules, but significantly inhibits MNPs transport by suppressing the electrostatic double layers based on colloid stability theory. Consequently, the cotransport of MNPs and CTC is governed by the coupled interplay of collector surface roughness and chemical heterogeneity, due to the soil colloid coatings and the adsorbed CTC on the surfaces associated with solution chemistries such as ionic strength. Increased cotransport of MNPs and CTC occurred under a higher concentration of MNPs due to a larger number of adsorption sites for CTC. Our findings advance the current understanding of the complex cotransport of MNPs and antibiotics in the environment. This information is valuable for understanding contaminant fate and formulating strategies for environmental remediation due to the contamination of MNPs and co-occurring contaminants.

SARS-CoV-2 and other main pathogenic microorganisms in the environment: Situation in Galicia and Spain

In the context of the current COVID-19 pandemic, and mostly taking a broad perspective, it is clearly relevant to study environmental factors that could affect eventual future outbreaks due to coronaviruses and/or other pathogenic microorganisms. In view of that, the authors of this manuscript review the situation of SARS-CoV-2 and other main pathogenic microorganisms in the environment, focusing on Galicia and Spain. Overall, in addition to showing local data, it is put in evidence that, summed to all efforts being carried out to treat/control this and any other eventual future epidemic diseases, both at local and global levels, a deep attention should be paid to ecological/environmental aspects that have effects on the planet, its ecosystems and their relations/associations with the probability of spreading of eventual future pandemics.

Environmental relevance of adsorption of doxycycline, enrofloxacin, and sulfamethoxypyridazine before and after the removal of organic matter from soils

In this work batch-type experiments were used to study the adsorption of the antibiotics doxycycline (DC), enrofloxacin (ENR), and sulfamethoxypyridazine (SMP) in cultivation soils, before and after the removal of soil organic matter. Organic matter removal by calcination resulted not only in C and N removal, but also in increased soil pH, exchangeable basic cations and surface area values. The results indicate a very different behavior depending on the type of antibiotic, showing the adsorption sequence DC > ENR > SMP. Specifically, DC adsorption was very high in untreated soil samples (with organic matter), and was still high (although decreased) after the removal of soil organic matter. Furthermore, the adsorption behavior of DC was clearly dependent on the pH of the medium. Regarding ENR, it also showed high adsorption, although to a lesser extent than DC. However, when soil organic matter was removed, ENR adsorption significantly decreased in all soil samples. As regards SMP, it was adsorbed to a much lesser extent, and the removal of soil organic matter caused an additional drastic decrease in adsorption, reaching negligible values in some samples. Desorption followed the reverse sequence of adsorption, specifically in the order DC < ENR < SMP. In the case of DC, desorption was negligible, both in samples with and without organic matter, while for ENR and SMP, desorption clearly increased for soil samples where organic matter was removed. These results may be of relevance as regards environmental quality and public health, especially to facilitate a correct use of soils and organic amendments in areas that receive the application of substances containing the investigated antibiotics.

Tetracycline and Sulfonamide Antibiotics in Soils: Presence, Fate and Environmental Risks

Veterinary antibiotics are widely used worldwide to treat and prevent infectious diseases, as well as (in countries where allowed) to promote growth and improve feeding efficiency of food-producing animals in livestock activities. Among the different antibiotic classes, tetracyclines and sulfonamides are two of the most used for veterinary proposals. Due to the fact that these compounds are poorly absorbed in the gut of animals, a significant proportion (up to ~90%) of them are excreted unchanged, thus reaching the environment mainly through the application of manures and slurries as fertilizers in agricultural fields. Once in the soil, antibiotics are subjected to a series of physicochemical and biological processes, which depend both on the antibiotic nature and soil characteristics. Adsorption/desorption to soil particles and degradation are the main processes that will affect the persistence, bioavailability, and environmental fate of these pollutants, thus determining their potential impacts and risks on human and ecological health. Taking all this into account, a literature review was conducted in order to shed light on the current knowledge about the occurrence of tetracycline and sulfonamide antibiotics in manures/slurries and agricultural soils, as well as on their fate in the environment. For that, the adsorption/desorption and the degradation (both abiotic and biotic) processes of these pollutants in soils were deeply discussed. Finally, the potential risks of deleterious effects on human and ecological health associated with the presence of these antibiotic residues were assessed. This review contributes to a deeper understanding of the lifecycle of tetracycline and sulfonamide antibiotics in the environment, thus facilitating decision-making for the application of preventive and mitigation measures to reduce its negative impacts and risks to public health.