The role of soil components in the sorption of tetracycline and heavy metals in soils

The role of magnesium ion in the interactions between humic acid and tetracycline in solution

Coexisting tetracycline (TC), dissolved organic matter (DOM), and metal cations in aqueous environments might form complexes and consequently affect the environmental fate of TC. In this study, the interactions among coexisting humic acid (HA), TC, and Mg(II) in solutions were investigated by equilibrium dialysis batch experiments and nuclear magnetic resonance hydrogen spectroscopy (1H NMR) characterization. In the binary systems, the dimethylamine (4Me2NH+) functional group on the A-ring of TC bound to the oxygen-containing functional groups of HA via hydrogen bond. The solution pH affected the agglomeration morphology and dissociation of the oxygen-containing functional groups of HA as well as protonation and spatial conformation of TC, which in turn affected the HA-TC interactions. The complexation sites and ratio of Mg(II) on TC affect the binding mode in the ternary system. When the TC-Mg(II) complexation ratio is 1:1, the B, C, and D rings of TC preferentially complex with Mg(II), resulting in the change of TC from an extended to a twisted conformation. At this time, Mg(II) had a weaker inhibitory effect on binding affinity between HA and TC. When the complexation ratio was 1:2, the second Mg(II) complexation deactivated the 4Me2NH + on the A ring and further stabilized TC twisted conformation, resulting in a stronger inhibitory effect on the binding of TC to HA. Under acidic conditions, the solution pH mainly caused the difficulty in forming TC-Mg(II) complexes. The inhibitory effect of Mg(II) on the binding between HA and TC is weaker than that under alkaline conditions.

Ecotoxicological effects of antibiotic adsorption behavior of microplastics and its management measures

Microplastics adsorb heavy metals and organic pollutants to produce combined pollution. Recently, the adsorption behavior of antibiotics on microplastics has received increasing attention. Exploring the sorption behavior of pollutants on microplastics is an important reference in understanding their ecological and environmental risk studies. In this paper, by reviewing the academic literature in recent years, we clarified the current status of research on the adsorption behavior of antibiotics on microplastics, discussed its potential hazards to ecological environment and human health, and summarized the influence of factors on the adsorption mechanisms. The results show that the adsorption behavior of antibiotics on microplastics is controlled by the physical and chemical properties of antibiotics, microplastics, and water environment. Antibiotics are adsorbed on microplastics through physical and chemical interactions, which include hydrophobic interaction, partitioning, electrostatic interaction, and other non-covalent interactions. Intensity of adsorption between them is mainly determined by their physicochemical properties. The basic physicochemical properties of the aqueous environment (e.g., pH, salinity, ionic strength, soluble organic matter content, and temperature) will affect the physicochemical properties of microplastics and antibiotics (e.g., particle size, state of dispersibility, and morphology), leading to differences in the type and strength of their interactions. This paper work is expected to provide a meaningful perspective for better understanding the potential impacts of antibiotic adsorption behavior of microplastics on aquatic ecology and human health. In the meantime, some indications for future related research are provided.

The Source and Distribution of Tetracycline Antibiotics in China: A Review

In recent years, antibiotics have been listed as a new class of environmental pollutants. Tetracycline antibiotics (TCs) used in human medical treatment, animal husbandry and agricultural production are the most widely used antibiotics. Due to their wide range of activities and low cost, their annual consumption is increasing. TCs cannot be completely metabolized by humans and animals. They can be abused or overused, causing the continuous accumulation of TCs in the ecological environment and potential negative effects on non-target organisms. These TCs may spread into the food chain and pose a serious threat to human health and the ecology. Based on the Chinese environment, the residues of TCs in feces, sewage, sludge, soil and water were comprehensively summarized, as well as the potential transmission capacity of air. This paper collected the concentrations of TCs in different media in the Chinese environment, contributing to the collection of a TC pollutant database in China, and facilitating the monitoring and treatment of pollutants in the future.

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.

Sorption of cefdinir, memantine, praziquantel and trimethoprim in sediment and soil samples

The everyday use of various pharmaceuticals to treat humans or animals means that they are increasingly found in the environment. Contamination of the soil can cause the active ingredients to be strongly sorbed to the soil or sediment. In the worst case, they can also be expected to occur in the aquatic environment due to their different polarity. In this study, four drugs from different therapeutic classes (trimetoprim, memantine, cefdinir, praziquantel) were used in dissolved form in two sediment and three soil samples to obtain data that can describe their fate and behavior in the environment. The sorption affinities of the pharmaceuticals were described using linear, Freundlich and Dubinin-Radushkevich sorption isotherms. The highest K_d values were obtained for cefdinir, while memantine and praziquantel tended to be present in water due to their very low sorption coefficients. The studied influence of pH showed a negative trend for memantine and trimetoprim, while an increase in ionic strength resulted in higher K_d values for all drugs. The sorption mechanism for all tested samples was best described by the pseudo-secondary kinetic model (R² > 0.9999).

Groundwater antibiotic pollution and its relationship with dissolved organic matter: Identification and environmental implications

The occurrence of veterinary antibiotics and hydro-chemical parameters in eleven natural springs in a livestock production area is evaluated, jointly with the characterization of their DOM fingerprint by Orbitrap HRMS. Tetracycline and sulfonamide antibiotics were ubiquitous in all sites, and they were detected at low ng L^-1 concentrations, except for doxycycline, that was present at μg L^-1 in one location. DOM analysis revealed that most molecular formulas were CHO compounds (49 %-68 %), with a remarkable percentage containing nitrogen and sulphur (16 %-23 % and 11 %-24 %, respectively). Major DOM components were phenolic and highly unsaturated compounds (~90 %), typical for soil-derived organic matter, while approximately 11 % were unsaturated aliphatic, suggesting that springs may be susceptible to anthropogenic contamination sources. Comparing the DOM fingerprint among sites, the spring showing the most different profile was the one with surface water interaction and characterized by having lower CHO and higher CHOS formulas and aliphatic compounds. Correlations between antibiotics and DOM showed that tetracyclines positively correlate with unsaturated oxygen-rich substances, while sulfonamides relate with aliphatic and unsaturated oxygen-poor compounds. This indicates that the fate of different antibiotics will be controlled by the type of DOM present in groundwater.

Tetracyclines in the environment: An overview on the occurrence, fate, toxicity, detection, removal methods, and sludge management

Tetracyclines (TCs) are a group of broad-spectrum antibiotics having vast human, veterinary, and aquaculture applications. The continuous release of TCs residues into the environment and the inadequate removal through the conventional treatment systems result in its prevalent occurrence in soil, surface water, groundwater, and even in drinking water. As aqueous TCs contamination is the tip of the iceberg, and TCs possess good sorption capacity towards soil, sediments, sludge, and manure, it is insufficient to rely on the sorptive removal in the conventional water treatment plants. The severity of the TCs contamination is evident from the emergence of TCs resistance in a wide variety of microorganisms. This paper reviews the recent research on the TCs occurrence in the environmental matrices, fate in natural systems, toxic effects, and the removal methods. The high performance liquid chromatography (HPLC) determination of TCs in environmental samples and the associated technology developments are analyzed. The benefits and limitations of biochemical and physicochemical removal processes are also discussed. This work draws attention to the inevitability of proper TC sludge management. This paper also gives insight into the limitations of TCs related research and the future scope of research in environmental contamination by TCs residues.

Factors affecting sorption behaviors of tetracycline to soils: Importance of soil organic carbon, pH and Cd contamination

The abuse of tetracycline arises the risk of antibiotic resistance genes and has been paid much attention. To understand the potential bioavailability of tetracycline (TC) in soil environments, this study explored the behaviors of TC adsorbing to six types of soils sampled from different regions of China. Moreover, the solution pH and existence of Cd²⁺ effect on TC sorption to soils were investigated to understand the influential factors affecting TC sorption. The results showed that the soil properties and sorption capacity of TC varied significantly with different soils. The sorption capacity of TC to soils might be largely affected by cation exchange capacity (CEC) and soil organic carbon (SOC), while the sorption rate, interaction strength and equilibrium sorption binding might be affected by soil pH, pH_PZC, soil inorganic carbon (SIC) and H content. The result of solution pH effect suggested that the predominant sorption mechanism for acid soils might be hydrophobic interactions between soils and H²TC⁰, and the cation exchange was possibly proposed as the primary mechanism for TC sorption to alkaline soils. Furthermore, the presence of Cd²⁺ might increase TC sorption to acid soil, while reduce TC sorption to alkaline soil. It is expected that this study may provide important information for predicting the potential fate of TC (or similar antibiotics) in different soils, and thus helping to assess the bioavailability of TC in soils.

Interfacial interaction between diverse microplastics and tetracycline by adsorption in an aqueous solution

The accumulation of microplastics in offshore aquaculture waters has gradually become a threat to the survival of marine life, and the combined pollution of microplastics and other pollutants is attracting widespread attention. In this paper, tetracycline (TC) was selected as a typical antibiotic, and its adsorption behavior on the surface of diverse type and different sizes of microplastics was studied to explore their combined pollution in an aqueous solution. The results of isotherm fitting showed that the maximum adsorption capacity and coefficient of polyethylene (PE) were the largest, and the adsorption capacity of PE was the strongest among the three microplastics: polyethylene (PE), polystyrene (PS) and polyvinyl chloride (PVC). With increasing PE particle size, the maximum adsorption capacity and adsorption coefficient of TC showed a significant decreasing trend, with a slight fluctuation in the middle. The presence of Pb²⁺, Cr³⁺, Cd²⁺, and Zn²⁺ markedly enhanced the adsorption of TC to PE, and Cu²⁺ could reduce the adsorption of TC to PE. The presence of chloride ions did not affect the adsorption process, which indicated that the adsorption mechanism between TC and microplastics is mainly an ion exchange mechanism. These results showed that the surface properties of microplastics and the chemical properties of the aqueous solution played an important role in the adsorption of TC. This study provides important scientific guidance and a theoretical basis for the study of the interfacial behavior, migration and transformation of marine microplastics.