Sorption and desorption of sulfadimethoxine, sulfaquinoxaline and sulfamethazine antimicrobials in Brazilian soils

Insight into the sorption and desorption pattern of pyrrolizidine alkaloids and their N-oxides in acidic tea (Camellia sinensis) plantation soils

Pyrrolizidine alkaloids (PAs) and their N-oxides (PANOs) are phytotoxins produced by various plant species and have been emerged as environmental pollutants. The sorption/desorption behaviors of PAs/PANOs in soil are crucial due to the horizontal transfer of these natural products from PA-producing plants to soil and subsequently absorbed by plant roots. This study firstly investigated the sorption/desorption behaviors of PAs/PANOs in tea plantation soils with distinct characteristics. Sorption amounts for seneciphylline (Sp) and seneciphylline-N-oxide (SpNO) in three acidic soils ranged from 2.9 to 5.9 µg/g and 1.7 to 2.8 µg/g, respectively. Desorption percentages for Sp and SpNO were from 22.2% to 30.5% and 36.1% to 43.9%. In the mixed PAs/PANOs systems, stronger sorption of PAs over PANOs was occurred in tested soils. Additionally, the Freundlich models more precisely described the sorption/desorption isotherms. Cation exchange capacity, sand content and total nitrogen were identified as major influencing factors by linear regression models. Overall, the soils exhibiting higher sorption capacities for compounds with greater hydrophobicity. PANOs were more likely to migrate within soils and be absorbed by tea plants. It contributes to the understanding of environmental fate of PAs/PANOs in tea plantations and provides basic data and clues for the development of PAs/PANOs reduction technology.

The effects of co-existing acridine on adsorption-desorption behavior of carbazole in soils: Co-sorption and mechanism insight

Carbazole (CBZ) and acridine (ACR) are polycyclic aromatic nitrogen heterocycles (PANHs) widely found in combined contaminated soils, while investigations on organic-organic interactions have been very limited. In this study, batch experiments were carried out on five soils with different properties, taking CBZ as a representative of PANHs and ACR as a co-existing contaminant. The adsorption isotherms of CBZ (50-1000 μg/L) were nonlinear. Soil organic matter (SOM) and cation exchange capacity (CEC) showed positive correlations with CBZ adsorption-desorption coefficients. The adsorption mechanisms of CBZ involved hydrogen bonding, π-π interaction, and cation-π bonding. Different concentrations of ACR had varying effects on CBZ. The adsorption of CBZ was inhibited with 250 μg/L ACR. The cooperative adsorption was observed on three soils with increasing ACR concentration (1000 μg/L) and led to more pronounced nonlinear isotherms. The S-shaped isotherms of ACR indicated that ACR was adsorbed to the soil surface in a perpendicular configuration. New adsorption sites were created allowing for increased CBZ adsorption through π-π interaction with ACR. Therefore, variations in soil properties and potential impacts of co-existing contaminants should be well considered when assessing the combined pollution of site soil. This will contribute to a more accurate estimation of environmental and health risks.

Experimental data and modeling of sulfadiazine adsorption onto raw and modified clays from Tunisia

In recent years, the increasing detection of emerging pollutants (particularly antibiotics, such as sulfonamides) in agricultural soils and water bodies has raised growing concern about related environmental and health problems. In the current research, sulfadiazine (SDZ) adsorption was studied for three raw and chemically modified clays. The experiments were carried out for increasing doses of the antibiotic (0, 1, 5, 10, 20, and 40 μmol L-1) at ambient temperature and natural pH with a contact time of 24 h. The eventual fitting to Freundlich, Langmuir and Linear adsorption models, as well as residual concentrations of antibiotics after adsorption, was assessed. The results obtained showed that one of the clays (HJ1) adsorbed more SDZ (reaching 99.9 % when 40 μmol L-1 of SDZ were added) than the other clay materials, followed by the acid-activated AM clay (which reached 99.4 % for the same SDZ concentration added). The adsorption of SDZ followed a linear adsorption isotherm, suggesting that hydrophobic interactions, rather than cation exchange, played a significant role in SDZ retention. Concerning the adsorption data, the best adjustment corresponded to the Freundlich model. The highest Freundlich KF scores were obtained for the AM acid-treated and raw HJ1 clays (606.051 and 312.969 Ln μmol1-n kg-1, respectively). The Freundlich n parameter ranged between 0.047 and 1.506. Regarding desorption, the highest value corresponded to the AM clay, being generally <10 % for raw clays, <8 % for base-activated clays, and <6 % for acid-activated clays. Chemical modifications contributed to improve the adsorption capacity of the AM clay, especially when the highest concentrations of the antibiotic were added. The results of this research can be considered relevant as regard environmental and public health assessment since they estimate the feasibility of three Tunisian clays in SDZ removal from aqueous solutions.

Transport of sulfanilamide in saturated porous media under different solution chemistry conditions: role of physicochemical characteristics of soils

Identification of the transport of sulfonamide antibiotics in soils facilitates a better understanding of the environmental fate and behaviors of these ubiquitous contaminants. In this study, the mobility properties of sulfanilamide (SNM, a typical sulfonamide antibiotic) through saturated soils with different physicochemical characteristics were investigated. The results showed that the physicochemical characteristics controlled SNM mobility. Generally, the mobility of SNM was positively correlated with CEC values and soil organic matter content, which was mainly related to the interactions between the organic matter in soils and SNM molecules via π-π stacking, H-bonding, ligand exchange, and hydrophobic interaction. Furthermore, higher clay mineral content and lower sand content were beneficial for restraining SNM transport in the soils. Unlike Na+, Cu2+ ions could act as bridging agents between the soil grains and SNM molecules, contributing to the relatively weak transport of SNM. Furthermore, the trend of SNM mobility in different soil columns was unaffected by solution pH (5.0-9.0). Meanwhile, for a given soil, the SNM mobility was promoted as the solution pH values increased, which was caused by the enhanced electrostatic repulsion between SNM- species and soil particles as well as the declined hydrophobic interaction between SNM and soil organic matter. The obtained results provide helpful information for the contribution of soil physicochemical characteristics to the transport behaviors of sulfonamide antibiotics in soil-water systems.

Seasonal variation and dissolved organic matter influence on the distribution, transformation, and environmental risk of pharmaceuticals and personal care products in coastal zone: A case study of Tianjin, China

Pharmaceuticals and personal care products (PPCPs) are emerging contaminants that have raised urgent environmental issues. The dissolved organic matter (DOM) plays a pivotal role on PPCPs' migration and transformation. To obtain a comprehensive understanding of the occurrence and distribution of PPCPs, a seasonal sampling focused on the riverine system in coastal zone, Tianjin, Bohai Rim was conducted. The distribution and transformation of thirty-three PPCPs and their interaction with DOM were investigated, and their sources and ecological risks were further evaluated. The total concentration of PPCPs ranges from 0.01 to 197.20 μg/L, and such value is affected by regional temperature, DOM and land use types. PPCPs migration at soil-water interface is controlled by temperature, sunlight, water flow and DOM. PPCPs have a high affinity to the protein-like DOM, while the humus-like DOM plays a negative influence and facilitates PPCPs' degradation. It is also found that protein-like DOM can represent point source pollution, while humus-like substances indicate non-point source (NPS) emission. Specific PPCPs can be used as markers to trace the source of domestic discharge. Additionally, daily use PPCPs such as ketoprofen, caffeine and iopromide are estimated to be the main risk substances, and their ecological risk varies on space, season and river hydraulic condition.

Adsorption-desorption of Atrazine with 9 Agricultural Soils in China

In this work, the characteristics and mechanisms for atrazine adsorption-desorption with 9 types of soils were investigated with batch equilibrium studies, elemental analyses, infrared spectroscopy, and UV‒visible spectroscopy. The atrazine sorption data for the 9 soils showed better fits with the Freundlich model than the Langmuir model, except with Red earth in Jiangxi (REJ) The results showed that the adsorption capacity was positively correlated with the organic matter (OM) content and negatively correlated with cation-exchange capacity (CEC) and pH. UV‒visible spectroscopy showed that dissolved organic matter (DOM) in the soil enhanced atrazine adsorption, but the adsorption on different DOM fractions was quite different. In addition, the infrared spectra revealed differences in the functional groups of soils and these functional groups may drive the adsorption process via hydrogen bonding and coordination with the -NH2 groups in atrazine.

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.

DGT method for the in situ measurement of triazines and the desorption kinetics of atrazine in soil

Triazines are frequently detected in nature water and agricultural soils worldwide. They are considered harmful to plants, animals, and the human health. In this study, diffusive gradients in thin films (DGT) method was developed for the assessment of several triazines. DGT device was used for the in situ measurement of atrazine in a pesticide factory and obtained reliable data. The atrazine concentrations measured by DGT, and solvent extraction method was in a constant ratio. The DIFS model was coupled with DGT technique to study the desorption kinetics of atrazine in four kinds of different soils. The yellow-brown soil was more inclined to adsorb atrazine than other three soils. 2_D DIFS model was used to obtain the partition coefficient for labile atrazine (K_dl), the values of the response time (T_c), and desorption/adsorption rates (k₁ and k_-1). The yellow-brown soil has a larger labile pool size, and a faster resupply speed of atrazine. The 1_D DIFS model was used to simulate the profiles of atrazine concentrations in soil solution and solid phase. The results show that the desorption of atrazine in soil was limited by kinetic limitation at short time, and was limited by the solid phase reservoir at long time.

A review of the influence of soil minerals and organic matter on the migration and transformation of sulfonamides

Sulfonamides (SAs) are common antibiotics that are widely present in the environment and can easily migrate in the environment, so they pose an environmental risk. Minerals and organic matter influence the antibiotic migration and transformation in sewage treatment plants, activated sludge, surface water, and soil environment. In the present paper, the influence of the process and mechanism of minerals and organic matter on the adsorption, degradation, and plant uptake of SAs in soil were summarized. In the impact process of mineral and organic matter on the SAs migration and transformation, the pH value is undoubtedly the most important factor because it determines the ionic state of SAs. In terms of influence mechanisms, the minerals absorb SAs well via cation exchange, complexation, H-bonding, and cation bridging. Mineral photodegradation is also one of the primary removal methods for SAs. Soil organic matter (SOM) can significantly increase the SAs adsorption. The adsorption forces of SAs and SOM or dissolved organic matter (DOM) were very similar, but SOM decreased SAs mobility in the environment, while DOM increased SAs availability. DOM generated active substances and aided in the photodegradation of SAs. This review describes the effects of minerals and organic matter on the fate of SAs in soil, which is useful in controlling the migration and transformation of SAs in the soil environment.

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).

Microbial degradation of antibiotic: future possibility of mitigating antibiotic pollution

Antibiotics are the major pharmaceutical wastes that are being exposed to the environment from the pharmaceutical industries and for the anthropogenic activities. The use of antibiotics for disease prevention and treatment in humans has been surpassed by the amount used in agriculture, particularly on livestock. It is stipulated that the overuse of antibiotics is the single largest reason behind the rise of bacterial anti-microbial resistance (AMR). The development of alternative therapy, like gene therapy, immunotherapy, use of natural products, and various nanoparticles, to control bacterial pathogens might be an alternative of antibiotics for mankind but the remediation of already exposed antibiotics from the lithosphere and hydrosphere needs to be envisioned with priority. The ever-increasing release of antibiotics in the environment makes it one of the major emerging contaminants (ECs). Decomposition of such antibiotic contaminants is a great challenge to get a cleaner environment. There are reports describing the degradation of antibiotics by photolysis, hydrolysis, using cathode and metal salts, or by degradation via microbes. Antimicrobials like sulfonamides are recalcitrant to natural biodegradation, exhibiting high thermal stability. There are recent reports on microbial degradation of a few common antibiotics and their derivatives but their applications in waste management are scanty. It could however be a major concern to the scientists whether to use the antibiotic degradation traits of a microbe for the removal of antibiotic wastes. The complexity of the genetic clusters of a microbe that are responsible for degradation is crucial, as a small genetic cluster might have higher chance of horizontal transfer into sensitive species of the normal microbial flora that in turn triggers the rise of antimicrobial resistance.

Understanding flow patterns from the field - Controlled laboratory experiments on the transport behavior of veterinary antibiotics in the presence of liquid manure

The main entry path of veterinary antibiotics to the environment is the application of liquid manure on agricultural land. Along with the manure, they can infiltrate into soils and leach into groundwater. As the environmental behavior of veterinary antibiotics is strongly affected by the process of sorption, the comprehensive knowledge regarding their sorption behavior is key to a reliable risk assessment. However, the flow patterns in field experiments are influenced by several factors that can hardly be distinguished, while most of the sorption studies on veterinary antibiotics were designed without manure or as batch experiments, which means that the effects of manure on the transport behavior of the antibiotic substances remained unaccounted for. In order to understand the results from a previous field experiment and concurrently fill the identified knowledge gap, a column experiment was performed to investigate the effects of manure on the transport of sulfamethazine, sulfadiazine, tetracycline, and lincomycin in soil. Results show that sulfamethazine and sulfadiazine were highly mobile in both the presence and absence of manure, while tetracycline did not appear at the outlet of any column. Despite their high mobility, in the presence of manure the sulfonamides were slightly delayed compared to the conservative tracer as was also seen during the previous field experiment. Lincomycin transport was already delayed in the absence of manure. Furthermore, in the presence of manure, lincomycin was delayed by 4.5 times relative to the tracer, which clearly underlined the influence of manure on the transport of lincomycin and offers an explanation why lincomycin has barely been detected in the long-term field experiment. However, in contrast to the results obtained in the field experiment, the recovery rates were the same in presence and absence of manure for both sulfonamides and lincomycin, probably due to reduced degradation at the applied concentration level.

The adsorption-desorption characteristics and degradation kinetics of ceftiofur in different agricultural soils

Cephalosporins are one of the most widely used antibiotics. When cephalosporins are discharged into the environment, they not only induce the production of antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARBs) but also cause toxic effects on animals and plants. Due to their complicated environmental behavior and lack of relevant data, the environmental behavior remains unclear. In this study, the adsorption-desorption and degradation characteristics of the third-generation cephalosporin drug ceftiofur (CEF) were investigated in three agricultural soils (sandy loam, loam and clay). According to the relevant parameters of the Freundlich adsorption isotherm (the K_f range was 57.63-122.44 μg^1-1/n L^1/n kg^-1), CEF was adsorbed moderately in the soils and had the potential to migrate into groundwater. CEF exhibited low persistence in the soils and faster degradation than other antibiotics, such as tetracyclines and fluoroquinolones. The degradation half-lives (DT50) of CEF in soils ranged from 0.76 days to 4.31 days. Adding feces, increasing the water content, providing light and increasing the temperature significantly accelerated the degradation of CEF in soils. The DT50 values of CEF in soils were significantly prolonged when the soils were sterilized, indicating that both physical degradation and biodegradation played important roles in the degradation of CEF in soils. The DT50 values of CEF in soils were significantly prolonged at high concentrations, indicating that the degradability of CEF in soils was affected by the initial concentration. No significant differences were observed in the DT50 values for the different soil types (p > 0.05). This study provides useful information about the environmental behavior of CEF and improves the environmental risk assessment of CEF.

The effects of biochar/compost for adsorption behaviors of sulfamethoxazole in amended wetland soil

Biochar and compost were two common amendments for the polluted soil. However, few studies were conducted to study the sorption of organic pollutants on combined biochar-compost and the relative adsorption mechanisms in mixed soil. The work had studied the adsorption and desorption behaviors of sulfamethoxazole (SMX) onto wetland soil after amended with biochar and/or compost. Moreover, the physicochemical and morphology properties of biochar/compost and amended soils were analyzed to discuss the relative adsorption mechanisms. Studies showed that the adsorption capacity of amended soils increased with the total amount of biochar or/and compost added, which was positively related to SOM, CEC, and EC of amended soils, but had nothing to do with the type of additives. Compared with the compost-treated treatments, the biochar-treated treatments generally achieved lower desorption rates, which also had demonstrated both different adsorption mechanisms. Pore filling and hydrophobic partitioning were the main adsorption mechanisms for biochar and compost, respectively. Though biochar owned developed pore structure, however, pore-filling of biochar was overwhelmingly weakened due to pore-blocking in mixed soils. Hence, in soil environment, compost is a kind of a more desirable amendment than biochar in absorbing and degrading organic pollutants.

Sorption of sulfadiazine and flow modeling in an alluvial deposit of a dry riverbed in the Brazilian semiarid

The Brazilian semiarid region is subjected to irregular rainfall, prolonged droughts, and high temperatures, hampering the surface water accumulation. The water access is restricted to the alluvium in the valleys, which are used for cattle and poultry livestock development. These activities trigger the excessive use of veterinary antibiotics. As a consequence, antibiotics reach sediment surfaces and promote deterioration of groundwater quality. This work aims to evaluate the sorption potential of Sulfadiazine (SDZ) and to understand the dynamics of water transfer and solute transport processes in a typical alluvial deposit of the Capibaribe River, in the Agreste of Pernambuco. The sedimentological characterization was performed by Miall's Code, defining four lithofacies (Scm, Scm,b, Gcm,o, Scm,o). Kinetics and isotherms experiments allowed the analyses of SDZ sorption. Kinetics sorption showed an equilibrium tendency after 40 h and was better described by a second-order model, while isotherm sorption data were better fitted by the Freundlich model. According to the particle size distribution curve, Scm had the highest number of fine particles and organic matter, affecting interaction of SDZ in sediments. Consequently, SDZ sorption was slightly higher in this lithofacies. However, overall, SDZ sorption was low, thereby offering a real risk of groundwater contamination. For further investigation the dynamics of water transfer and solute transport in a heterogeneous alluvial deposit were simulated with the HYDRUS-2D. The structural heterogeneity influenced the spatial distribution of water storage under unsaturated conditions and provided the emergence of preferential flows. The solute dynamic follow a similar behavior of the water flow, due to the low retention of SDZ in the soil. Considering a condition near to saturation, the contrast of hydraulic and transport properties influences simultaneously in the processes of water transfer and solute transport.

Microplastics aged in various environmental media exhibited strong sorption to heavy metals in seawater

To date, the degradation of microplastics (MPs; <5 mm) in different environments, particularly their adsorption characteristics for coexisted metal pollutants remains to be elucidated. Thus, this study investigated the effects of aging MPs, including polyamide (mPA), polyethylene terephthalate (mPET), polystyrene (mPS), and polyvinyl chloride (mPVC) for 3 months under UVA irradiation in four environmental media (air, seawater, sand, and soil) and adsorption of heavy metals (Cu, Cd) onto seawater-aged mPS and mPVC. The results showed that surface morphological changes, including cracks, oxidized particles, and wrinkles, appeared on aged MPs. The heavy metal adsorption capacity decreased in the order aged mPVC > aged mPS > unaged mPS > unaged mPVC, and the Cu²⁺ and Cd²⁺ ions competed for active adsorption sites on the MPs surfaces. Overall, the aging environment affected the physical and chemical properties of MPs and the aging of MPs enhanced their adsorption of coexisting metals tested.

Removal of extracellular antibiotic resistance genes using magnetic biochar/quaternary phosphonium salt in aquatic environments: A mechanistic study

The proliferation and spread of antibiotic resistance genes (ARGs) is becoming a worldwide crisis. Extracellular DNA encoding ARGs (eARGs) in aquatic environment plays a critical role in the dispersion of antimicrobial resistance genes. Strategies to control the dissemination of eARGs are urgently required for ecological safety and human health. Towards this goal, magnetic biochar/quaternary phosphonium salt (MBQ), was used to investigate the efficiency and removal mechanism for eARGs. Magnetic biochar modified by quaternary phosphonium salt enhanced the adsorption capacity of extracellular DNA to approximately 9 folds, compared to that of the unmodified. DNA adsorption by MBQ was mainly dominated by chemisorption in heterogeneous systems and was promoted in acidic and low-salt environment. The generation of •OH and MBQ colloid jointly cleaved DNA into fragments, facilitating the adsorption of the phosphate backbone of DNA onto MBQ through electrostatic force as well as the conformational transition of DNA. Furthermore, quantification of extracellular DNA after MBQ was applied in water demonstrated that over 92.7% of resistance genes were removed, indicating a significantly reduced risk of propagation of antimicrobial resistance in aquatic environments. These findings have a practical significance in the application of MBQ in mitigating the spread of ARGs in aquatic environment.

Critical review of effluent dissolved organic nitrogen removal by soil/aquifer-based treatment systems

Soil/aquifer-based treatment systems improve wastewater effluent quality by removing trace contaminants in the soil and/or aquifer during groundwater recharge. This paper critically reviews these systems with a focus on removing nitrogen, particularly low levels of dissolved organic nitrogen (DON) present in the wastewater effluent. DON in wastewater effluent is a concern because of its contribution to nitrogen concentration in surface or groundwater and its role as a precursor of nitrogenous disinfection by-products, which are harmful to human health. Biodegradation and sorption are the main DON removal mechanisms in the subsurface environment where most of the removal happens in the vadose zone. Different factors such as temperature, redox conditions, retention time, indigenous microbial community, and soil type affect DON removal in soil/aquifer-based treatment systems. Lack of sufficient current knowledge underlines the need for designing lab/field scale systems for further determination of the relative contribution of biodegradation and sorption, optimal hydraulic loading rate, and the relationship between DON characteristics such as functional groups and physiochemical processes and its removal. Future research needs for DON removal in soil/aquifer-based treatment systems are identified.

Sorption of diethyl phthalate and cadmium by pig carcass and green waste-derived biochars under single and binary systems

Potentially toxic elements (PTEs) and phthalic acid esters (PAEs) often coexist in contaminated soils. Their co-existence may affect the mutual sorption behavior, and thereby influence their bioavailability and fate in soils. To our best knowledge, the impacts of plant-and animal-derived biochar on the competitive sorption-desorption of PTEs and PAEs in soils with different organic carbon content have not been studied up to date. Therefore, in this study, batch sorption-desorption experiments were conducted to investigate the influence of biochars derived from pig carcass and Platanus orientalis branches on the mono- and competitive sorption of cadmium (Cd²⁺) and diethyl phthalate (DEP) in soils with high (HS) and low (LS) organic carbon content. The DEP sorption was well described by Freundlich isotherm model, while Cd²⁺ sorption fitted better with the Langmuir isotherm model. Application of both biochars enhanced soil sorption of DEP, which increased as the application doses increased. The HS showed a stronger affinity to both DEP and Cd²⁺ than the LS. In the LS, the pig carcass biochar (PB) addition was more effective to increase the sorption capacity of Cd²⁺ and DEP and to reduce their desorption than woody biochar (WB) treatments. Moreover, the co-existing of Cd²⁺ could reduce the sorption of DEP, especially in the LS. The presence of DEP enhanced Cd²⁺ sorption in LS treated by both biochars, but the sorption of Cd²⁺ was suppressed with DEP addition in the PB-amended HS. In conclusion, the soil sorption capacity of DEP and Cd²⁺ was affected by biochar type, application dose and soil organic carbon content. The reciprocal effect between DEP and Cd²⁺ was also a crucial factor influencing their sorption/desorption by biochar. Therefore, PB and WB, especially PB, can be used for metal/DEP immobilization due to enhanced sorption. This approach is applicable for future remediation of soils contaminated by PTEs and PAEs.

Dissipation and sorption-desorption of benzisothiazolinone in agricultural soils and identification of its metabolites

Benzisothiazolinone has been widely used to control bacterial and fungal diseases in various agricultural crops by destroying the nuclear structure and interfering with the metabolism of microbial cells. In this study, the dissipation, transformation and sorption-desorption of benzisothiazolinone (BIT) in five soils were investigated to evaluate its environmental fate. Results showed that the degradation of BIT in all the tested soils fitted the first order kinetics and increased with soil organic matter (OM) content. Degradation differences between unsterilized natural and sterilized soils (t 1/2 = 0.09-26.66 and 6.80-86.64 d) suggested that BIT degradation is primarily driven by biological processes and assisted by abiotic degradation. Additionally, BIT dissipated fastest in flooded soils (t 1/2 = 0.20-4.53 d), indicating that anaerobic microorganisms are more likely to degrade BIT compared to aerobic microbes. Also, during the soil degradation process, two metabolites were monitored and identified for the first time. BIT sorption was a spontaneous physical process with no desorption hysteresis effect, which fit the Freundlich model. BIT causes relatively strong sorption (log K OC = 3.76-4.19) and low persistence in soils, thus exhibiting a low potential risk for groundwater contamination.

Occurrence and human health risk assessment of antibiotics and their metabolites in vegetables grown in field-scale agricultural systems

The occurrence of antibiotics (ABs) in four types of commercially grown vegetables (lettuce leaves, tomato fruits, cauliflower inflorescences, and broad bean seeds) was analyzed to assess the human exposure and health risks associated with different agronomical practices. Out of 16 targeted AB residues, seven ABs belonging to three groups (i.e., benzyl pyrimidines, fluoroquinolones, and sulfonamides) were above the method detection limit in vegetable samples ranging from 0.09 ng g^-1 to 3.61 ng g^-1 fresh weight. Data analysis (quantile regression models, principal component and hierarchical cluster analysis) showed manure application, irrigation with river water (indirect wastewater reuse), and vegetable type to be the most significant factors for AB occurrence in the targeted crops. Metabolites were detected in 70 of the 80 vegetable samples analyzed, and their occurrence was both plant- and compound-specific. In 73 % of the total samples, the concentration of AB metabolites was higher than the concentration of their parent compound. Finally, the potential human health risk estimated using the hazard quotient approach, based on the acceptable daily intake and the estimated daily intake, showed a negligible risk for human health from vegetable consumption. However, canonical-correspondence analysis showed that detected ABs explained 54 % of the total variation in AB resistance genes abundance in the vegetable samples. Thus, further studies are needed to assess the risks of antibiotic resistance promotion in vegetables and the significance of the occurrence of their metabolites.

Physiochemical assessment of environmental behaviors of herbicide atrazine in soils associated with its degradation and bioavailability to weeds

Atrazine residue in soil is one of the serious environmental problems and continues to risk ecosystem and human health. To address the environmental behaviors and dissipation of atrazine and better manage the application of atrazine in reality, we comprehensively investigated the adsorption and desorption, migration ability, and vanishing of atrazine in three distinct soils in China including Jiangxi (JX, pH 5.45, TOC 0.54%), Nanjing (NJ, pH 6.15, TOC 2.13%), and Yancheng (YC, pH 8.60, TOC 0.58%) soils. The atrazine adsorptive capacity to the soils was arranged in the order of NJ > YC > JX. The leaching assay with profiles of the soils showed strong migration, suggesting it had a high bioavailability to weeds and potential for underground water contamination. We further investigated the effects of environmental factors such as soil moisture, microbial activity and photolysis on atrazine degradation and showed that the degradation of atrazine in the soil mainly underwent the abiotic process, most likely through hydrolysis and photolysis-mediated mechanisms, and to less extend through soil microbial catabolism. Using HRLC-Q-TOF-MS/MS and by comparing the measured and theoretical m/z values and fragmentation data, ten metabolites comprising eight degraded products and two conjugates were characterized. Atrazine existing in the soils and sprayed coordinately blocked the growth of three common weeds, which prompted us to use the minimal atrazine in practice to control the waste of the pesticide and its impact on the environment. Overall, our work provided an insight into the mechanisms for the degradation of atrazine residues in the soils and contributed to the environmental risk assessment of the pesticide and management in its application control in the crop rotation and safe production.

Comparison of the toxicity of waters containing initially sulfaquinoxaline after photocatalytic treatment by TiO2 and polyaniline/TiO2

This paper addresses the residual toxicity of waters after photocatalysis treatments. The initial waters contain 7 mg L^-1 of sulfaquinoxaline (SQX) which is a sulfonamide antibiotic generally recorded inside the water. The contaminated waters are treated by photocatalytic degradation process with bare titania and titania covered with polyaniline (PANI) conducting polymer. The degradation of SQX is conducted at different pH in order to find the optimal condition to obtain SQX concentration relatively equal to zero in the shortest amount of time. This occurs for PANI/TiO₂ at pH 12 and TiO₂ at pH 4. Toxicity assays (concentration of biomass, pigmentation tests, and cells counting) are undertaken on the microalgae Chlorella vulgaris in order to evaluate the residual toxicity of the 2 treated waters. The toxicity results highlight that the water treated by PANI/TiO₂ at pH 12 is the less toxic towards the algae cells. The water processed by bare titania at acidic pH displays unneglectable toxicity towards the algae cells which are larger than the toxicity of the original SQX solution.

Effects of tall fescue biochar on the adsorption and desorption of atrazine in different types of soil

The excessive application of atrazine in agriculture has resulted in serious environmental contamination. The addition of biochar could reduce the bioavailability and mobility of atrazine in soil through adsorption-desorption processes. In this study, tall fescue biochar was prepared at 500 °C, and its effect on the adsorption-desorption behavior of atrazine in red soil, brown soil, and black soil was investigated. The tall fescue biochar with the pH value of 9.64 had a developed porous structure and large specific area that contained abundant surface functional groups. The element composition of the tall fescue biochar was C (50.46%), O (15.01%), N (4.54%), H (2.56%), and S (1.47%). The adsorption process of atrazine in the three soil types with and without biochar addition was divided into a fast stage, slow stage, and equilibrium stage. A pseudo second-order kinetic model was suitable for fitting the adsorption process of atrazine, and the determination coefficient (R²) ranged from 0.985 to 0.999. The adsorption-desorption processes of atrazine were described accurately by the Freundlich model (R² of 0.967-0.999). The adsorption capacity of the three soil types for atrazine increased significantly with the addition of biochar, whereby the equilibrium adsorption amount increased from an initial range of 3.968 to 5.902 μg g^-1 to a final range of 21.397 to 21.968 μg g^-1. The desorption of atrazine was also inhibited as the hysteresis coefficient (HI) increased from an initial range of 0.451 to 0.586 to a final range of 0.916 to 0.941. The adsorption capacity of the red soil improved more than did the brown soil or black soil. Moreover, spontaneous adsorption of atrazine by the biochar-soil system occurred more easily at 35 °C than at 15 °C and 25 °C. Overall, tall fescue biochar was a prospective soil amendment material.

Fate and risk assessment of sulfonamides and metabolites in urban groundwater

Antibiotics, such as sulfonamides (SAs), have recently raised concern as wastewater treatment plants (WWTPs) partly remove them, and thus, SAs continuously enter the aquifers. In this context, the aims of this work are to (1) investigate the temporal evolution of SAs and metabolites in an urban aquifer recharged by a polluted river; (2) identify the potential geochemical processes that might affect SAs in the river-groundwater interface and (3) evaluate the ecological and human health risk assessment of SAs. To this end, 14 SAs and 4 metabolites were analyzed in river and urban groundwater from the metropolitan area of Barcelona (NE, Spain) in three different sampling campaigns. These substances had a distinct behavior when river water, which is the main recharge source, infiltrates the aquifer. Mixing of the river water recharge into the aquifer drives several redox reactions such as aerobic respiration and denitrification. This reducing character of the aquifer seemed to favor the natural attenuation of some SAs as sulfamethoxazole, sulfapyridine, and sulfamethizole. However, most of the SAs detected were not likely to undergo degradation and adsorption because their concentrations were constant along groundwater flow path. In fact, the intensity of SAs adsorption is low as the retardation factors are close to 1 at average groundwater pH of 7.2 for most SAs. Finally, risk quotients (RQs) are used to evaluate the ecological and human health risks posed by single and mixture of SAs in river water and groundwater, respectively. Life-stage RQs of the SAs detected in groundwater for the 8 age intervals were low, indicating that SAs and their mixture do not pose any risk to human beings. Concerning the environmental risk assessment, SAs do not pose any risk for algae, fish and crustaceans as the RQs evaluated are further lower than 0.1.

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.

Sorption-desorption of dimethoate in urban soils and potential environmental impacts

The environmental fate and impact of dimethoate application in the urban environment were assessed in nine selected soils. The pseudo-second-order kinetics model described the kinetics of dimethoate sorption very well in the urban soils exhibiting two distinct phases, an initial partitioning into clay surfaces and soil organic matter, and eventual diffusion into soil micropores. Dimethoate sorption in the urban soils followed the Freundlich model with an R² value of 0.94-0.99, suggesting a multi-layered sorption on the heterogeneous surfaces. Sorption of dimethoate in the soils was influenced by clay, silt, organic matter, carboxyl and alkyl groups, and Al and Fe oxides. The undecomposed or incompletely decomposed organic matter present in the soils greatly reduced the sorption and enhanced desorption. The calculated lower values for Freundlich constant (K_F) indicate the high mobility of dimethoate in the selected soils. Also, the values of groundwater ubiquity score (GUS), leachability index (LIX), hysteresis index (HI), and coefficient of distribution (K_d) for dimethoate in the soils clearly suggest that the insecticide is prone to leaching out significantly from the soil surface to groundwater. Moreover, the surface runoff from impervious places in the urban environment can be considered as a direct source of groundwater contamination, thereby affecting the quality of potable water besides posing a threat to non-target organisms of ecological importance and food safety. Thus, the present novel study suggests that the application of dimethoate in the urban environment having impervious surfaces must be judicious in order to minimize the potential human and ecological health risks.

Competitive and synergic sorption of carbamazepine, citalopram, clindamycin, fexofenadine, irbesartan and sulfamethoxazole in seven soils

Sorption of pharmaceuticals, which can occur in soils, may differ when present in a soil solution as a single compound or in a solution with other pharmaceuticals. Therefore, the sorption isotherms described by the Freundlich equations were evaluated for 6 compounds, which were applied in solutions of a single pharmaceutical, two pharmaceuticals or all pharmaceuticals to seven soils. Study mainly focused on a behavior of fexofenadine and irbesartan that occurred in soils in 3 forms (cationic, zwitter-ionic or neutral, anionic). Sorption of both compounds slightly increased (in some soils) when applied together, largely increased when applied with carbamazepine (neutral), and extremely increased when applied in solutions with citalopram (strongly sorbed cation), which could be explained by a cooperative multilayer sorption on soil constituents. On the other hand, sorption of both compounds moderately decreased when applied with clindamycin (cation and neutral) or sulfamethoxazole (neutral or anion). The magnitude of an increase or decrease in the Freundlich sorption coefficient (K_F) for a particular compound depended on soil conditions, a form of compound's molecule and its interaction with molecules of other compounds. Despite sorption being influenced by other compound(s) in solution, the K_F coefficients evaluated for a particular compound under the different conditions were mostly correlated with the same soil properties: K_F,CAR with an organic carbon content, K_F,CIT and K_F,CLI with a base cation saturation, K_F,SUL with hydrolytic acidity, and K_F,FEX and K_F,IRB with sorption complex saturation.

Tracing veterinary antibiotics in the subsurface - A long-term field experiment with spiked manure

The purpose of this long-term experiment was on gaining more insights into the environmental behaviour of veterinary antibiotics in the subsurface after application with manure. Therefore, manure spiked with a bromide tracer and eight antibiotics (enrofloxacin, lincomycin, sulfadiazine, sulfamethazine, tetracycline, tiamulin, tilmicosin and tylosin) in concentrations of milligrams per litre were applied at an experimental field site. Their pathway was tracked by continuous extraction of soil pore water at different depths and systematic sampling of groundwater for a period of two years. Seven target compounds were detected in soil pore water of which four leached into groundwater. Concentrations of the detected target compounds were, with few exceptions, in the range of nanograms per litre. It was concluded that a large fraction of the investigated antibiotics sorbed or degraded already within the first meter of the soil. Further, it was inferred from the data that long and warm dry periods cause attenuation of the target compounds through increased degradation or sorption occurring in the soil. In addition, the comprehensive data-set allowed to estimate a retardation factor between 1.1 and 2.0 for sulfamethazine in a Plaggic Anthrosol soil, and to classify the individual compounds by environmental relevance based on transport behaviour and persistence. According to the distribution of resistant genes in the environment, sulfamethazine was found to be the most mobile and persistent substance.

Long-term monitoring of sulfonamides and tetracyclines in manure amended soils and leachate samples - A follow-up study

Antibiotics can be detected in manure and digestate samples worldwide. As manure is a frequently used fertilizer, antibiotics are found in soil and leachate samples. Only little is known about the long-term fate of antibiotics in the soil environment. One shortcut is the lack of appropriate monitoring studies. Here we present the results of an unequalled soil monitoring study over 18 years from an agricultural field site in Lower Saxony (Germany). Sulfonamides and tetracycline are mainly fixed in the upper soil layer. Contents showed a sharp decrease below sampling depth of 30 cm (plough depth). Sulfaguanidine and sulfamethazine (SMZ) were detected down to 90 cm. Water samples taken below the field site revealed the transfer of sulfonamides into leachate. High variances were observed between sampling points emphasizing the need for sampling strategies for environmental studies. In addition, field lysimeters with defined input of sulfonamides enabled a long-term monitoring and mass balance of antibiotic transfer into leachate over 10 years. SMZ showed the highest mobility with concentrations up to 65 ng L-1. Less than 0.5% of the applied SMZ was transferred into the leachate. Data of lysimeter and field water samples support the theory of a steady state process with a continuous input of sulfonamides such as SMZ into leachate. Soils contaminated with antibiotics can be a long-term source for the input of antibiotic active compounds into deeper soil layers and groundwater.

Sorption and desorption of seven steroidal synthetic progestins in five agricultural soil-water systems

Manure fertilization and wastewater irrigation can introduce the biologically potent synthetic progestins into agricultural soils, causing endocrine disruption in organisms of nearby surface waters. Therefore, this study investigated the sorption and desorption potential of etonogestrel, medroxyprogesterone, gestodene, norgestrel, cyproterone acetate, levonorgestrel, and dienogest in five agricultural soil-water systems. Sorption data were well-described by the linear sorption model. In most batch systems, cyproterone acetate exhibited the highest affinities for soils, followed by etonogestrel, medroxyprogesterone, levonorgestrel, gestodene, norgestrel, and dienogest. The sorption magnitudes (logK_oc or logK_d) were significantly correlated with the progestin hydrophobicities (R² = 0.72-0.86, p < 0.05). The K_d values of the progestins were also significantly correlated with organic carbon content and pore volumes of the soils (R² = 0.68-0.98, p < 0.05). In addition, 0.5 M urea resulted in 3-19% decreases in K_d values of the progestins. Taken together, these data indicated that hydrophobic partitioning interaction, hydrogen bonding interaction, and pore filling were the sorption mechanisms for the progestins in soil-water systems. No significant desorption hysteresis was observed for the progestins, indicating that they can be readily desorbed under rainfall or irrigation events. Based on the sorption and desorption data, we estimated the dynamic transport of the progestins in conventional agricultural management systems, and predicted the concentrations of the progestins as a function of soil-sorbed concentration, water-soil ratio, and dilution factor of receiving waters. This study will improve the understanding of the risks posed by the progestins under field-scale hydrological conditions.

Movement and Fate of 2,4-D in Urban Soils: A Potential Environmental Health Concern

The fate and movement of 2,4-dichlorophenoxyacetic acid (2,4-D), in terms of sorption-desorption and leaching potential, were evaluated in urban soils following the batch experimental method. The sorption kinetics of 2,4-D in soils followed both "fast" and "slow" sorption processes that could be well described by a pseudo-second-order kinetics model, suggesting that 2,4-D was partitioned into soil organic matter and clay surfaces, and eventually diffused into soil micropores. The sorption isotherms were linear, following both Langmuir and Freundlich models. Partially decomposed or undecomposed organic matter present in urban soils decreased sorption and increased desorption of 2,4-D. Also, sorption of 2,4-D increased with an increase in the contents of clay and Al and Fe oxides, whereas sand and alkaline pH increased the desorption process. The lower calculated K _d values suggest that 2,4-D is highly mobile in urban soils than in agricultural soils. The calculated values of groundwater ubiquity score, leachability index, and hysteresis index indicated that the herbicide is highly prone to leach out from surface soil to groundwater which might affect the quality of potable water. The present study clearly suggests that 2,4-D must be judiciously applied in the urban areas in order to minimize the potential health and environmental risks.

Influence of mussel shell, oak ash and pine bark on the adsorption and desorption of sulfonamides in agricultural soils

Taking into account the high mobility and environmental risks due to sulfonamide antibiotics as emerging pollutants, batch-type experiments were performed to study adsorption/desorption of three sulfonamides (sulfadiazine -SDZ-, sulfamethazine -SMT- and sulfachloropyridazine -SCP-) in three agricultural soils. The study was carried out both for un-amended and amended soil samples, using different doses (0, 12, 24 and 48 Mg ha^-1) of three different by-products (mussel shell, oak ash and pine bark). Adsorption on un-amended soils was rather low, with percentages between 11 and 45% for SDZ, 20-64% for SMT, and 19-65% for SCP. Both the Linear and Freundlich models fitted well to adsorption curves. In the case of un-amended soils, and regarding the Linear model, the values of the coefficient of distribution (K_d, expressed in L kg^-1) were between 0.6 and 1.3 for SDZ, between 0.7 and 1.1 for SMT, and between 0.6 and 2.6 for SCP. As regards the Freundlich model, the values of the adsorption constant (K_F, expressed in L^1/n μmol^1-1/n kg^-1), were in the range 0.4-1.9 for SDZ, 0.9-2.9 for SMT, and 1.2-3.8 for SCP. Simultaneously, desorption percentages were high, reaching 13.7-47.7% for SDZ, 12.6-35.1% for SMT, and 13.7-34.3% for SCP, when the highest initial antibiotic concentration (50 μmol L^-1) was added, thus indicating low retention and high mobility for these compounds in soils. Mussel shell and oak ash amendments did not increase retention of any of the three sulfonamides. However, the incorporation of pine bark resulted in an increase in the adsorption and decrease in desorption for all three antibiotics. Specifically, for soils amended with pine bark at 48 Mg ha^-1, K_d values (expressed in L kg^-1) were between 2.1 and 2.9 for SDZ, between 3.4 and 3.6 for SMT, and between 2.5 and 8.2 for SCP. Regarding K_F (expressed in L^1/n μmol^1-1/n kg^-1), its values ranged from 5.6 to 6.3 for SDZ, 6.2-8.8 for SMT, and 5.3-7.1 for SCP. These scores were clearly higher than those of un-amended soils, and pine bark amendment also resulted in lower desorption percentages, ranging 8.7-11.4% for SDZ, 4.0-10.7% for SMT, and 6.5-16.9% for SCP. This positive effect on the retention of sulfonamides due to pine bark can be attributed to its high organic carbon content (48.6%), as well as to its acidic pH_w (4.0). Therefore, pine bark amendment can be considered an effective alternative to increase the retention of sulfonamides in soils, thus reducing their bioavailability and transport to other environmental compartments, and subsequent risks of negative impacts on human and environmental health.

New insight into the substituents affecting the peroxydisulfate nonradical oxidation of sulfonamides in water

The large consumption and discharge of sulfonamides (SAs) have potentially induced antibiotic resistance genes, posing inestimable threats to humans and ecosystems. In the present study, five SAs with different substituents were regarded as target compounds to be degraded using the nonradical dominated peroxydisulfate (PDS) activation process by the combination of ¹O₂ oxidation and direct electron transfer. The degradation rates, toxicities and pathways of SAs largely varied with their substituents. For instance, sulfathiazole with five-membered substituent had the highest degradation rate of 0.19 min^-1, which was 3.8 times as the rate of sulfanilamide (0.05 min^-1) without substituent. Then the theoretical calculation was adopted to further confirm that different substituents on the SAs could influence the molecular orbital distribution and their stability, thus resulting in the different removal rate of SAs. Finally, the products of different SAs were concisely deduced to take insight into the effects of different substituents on SAs degradation pathways. It was demonstrated that the geometrical differences among various SAs caused by the different substituents contributed to the different degradation pathways of SAs. Representatively, the special Smiles-type rearrangement pathway was occurred in the six-membered SAs instead of in the five-membered SAs, which inversely resulted in the slower degradation rate of six-membered SAs than the five-membered SAs. Thus, the present study provides a valuable insight into the effects of substituents on the degradation rate and transformation pathways of SAs in the nonradical PDS activation process.

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.

Adsorption/desorption and transport of sulfadiazine, sulfachloropyridazine, and sulfamethazine, in acid agricultural soils

Batch-type experiments were used to study adsorption-desorption of three sulfonamides: sulfadiazine (SDZ) sulfachloropyridazine (SCP), and sulfamethazine (SMT), in five crop soils, whereas laboratory soil column experiments were employed to obtain data on transport processes. Adsorption results were satisfactorily adjusted to Linear and Feundlich equations, with R² values above 0.95. Adsorption followed the sequence SDZ < SMT < SCP, showing higher values for soils with higher levels of organic carbon (OC) content. Conversely, desorption was higher in soils with less OC, and lower in soils with higher OC contents. The temporal moment analysis method gave values for the transport parameters τ and R which were significantly correlated with soil parameters related to organic matter, specifically OC and N concentrations. The higher retention of the three sulfonamides in soils with high organic matter content is a relevant fact, with value when programming management practices in agricultural soils, and specifically in relation to the spreading of animal manures, slurries, or waste containing these emerging pollutants.

Nitrofurantoin in sediments and soils: Sorption, isotherms and kinetics

Nitrofurantoin is nitrofuran antibacterial drug that is most used as a veterinary pharmaceutic compound. This compound, as well as other pharmaceuticals can greatly affect the environment, the soil and organisms in it and pollute aquatic ecosystems. Since it has been used for only a few decades, knowledge of their fate and behaviour in the environment is still limited. Because of that, the aim of this study was to experimentally determine the K_d values of nitrofurantoin in seven different natural soil and seven different sediment samples with different physico-chemical properties. Sorption phenomena were described with Linear, Freundlich and Dubinin-Radushkevich sorption isotherms. Obtained sorption coefficients (K_d) ranged from 3.967 to 5.121 mLg^-1 for sediment samples and 3.634-43.06 mL g^-1 for soil samples. The influence of ionic strength and pH of the nitrofurantoin solution and kinetics of the sorption and desorption process were also investigated. Results show that an increase in ionic strength and pH reduces the values of sorption coefficient while the mechanism of nitrofurantoin sorption is the best described with the kinetic model of pseudo-second order.

Sorption and leaching behavior of bithionol and levamisole in soils

The batch experiments were conducted to understand sorption process of bithionol (BIT) in yellow soil (YS) and red soil (RS), while column leaching experiments were performed to evaluate the leaching behavior of BIT and levamisole (LEV) in the tested soils. The adsorption and desorption data fitted well with the Freundlich isotherms (R² ≥ 0.94). The distribution coefficient of BIT in the YS and RS were 104 and 98.3 L/kg, respectively. Hysteresis was observed for bithionol desorption in the YS and RS, with hysteresis coefficient of 0.917 and 0.928, respectively. Dissolved organic matter (DOM) addition and acid condition enhanced the adsorption of BIT in the soil. Both BIT and LEV showed poor leaching potential in the tested soils. More than 80% of BIT and LEV remained in the surface soil layer and the amount of the two target compounds in the leachates accounted for less than 1% of overall recovery. DOM showed little influence on the concentration of BIT and LEV in the leachates collected at different time. The results could fill the gap on the behavior of BIT and LEV in soil under laboratory conditions.

Sorption and degradation of contaminants of emerging concern in soils under aerobic and anaerobic conditions

Large quantities of contaminants of emerging concern (CECs) are susceptible of entering the terrestrial environments through the application of recycled wastewater, manures, and biosolids, resulting in their progressive contamination and possible long-term effects over terrestrial species. Many studies on the environmental fate of CECs focus on aquatic environments and/or wastewater treatment plants, but little is still known about their behavior at environmentally relevant concentrations in agricultural soils. In this study, we evaluated the adsorption and degradation of nine different pharmaceuticals (nadolol, sulfamethizole, sulfamethoxazole, sulfamethopyridazone, carbamazepine, ibuprofen, diclofenac, hydrochlorothiazide, and gemfibrozil) and four artificial sweeteners (acesulfame, saccharin, cyclamate, and sucralose) in two soils under aerobic and anaerobic conditions. The sorption of target compounds in soils fitted well to a Freundlich isotherm model and was relatively low (K_f < 200 L kg^-1). Sorption was highest for cyclamate (K_f = 162 L kg^-1) and acesulfame (K_f = 156 L kg^-1), while lowest sorption coefficients were measured for ibuprofen (K_f = 1-7 L kg^-1). All target compounds (except for carbamazepine) were susceptible to microbial degradation under aerobic conditions, with half-lives ranging from 1 to 18 days. Degradation occurred at a higher rate under aerobic conditions for most contaminants, but they were relatively persistent under anaerobic conditions. For instance, over 90% of the initial amount of spiked nadolol was degraded in aerobic soils after 4 days of incubation, while only 18-24% was lost in absence of oxygen after 1 month, resulting in t_1/2 values between 95 and 103 days. The degradation behavior of the target compounds varied in relation to soil and compound physicochemical properties as well as the microbial activities (e.g., 220 ppm of CH₄ were produced in anaerobic experiments) and aeration of the tested soils. Overall, the poor adsorption and relative persistence of sucralose and carbamazepine suggests that both may be used as potential tracers for soil and groundwater contamination.

Effect of cation type in mixed Ca-Na systems on transport of sulfonamide antibiotics in saturated limestone porous media

Retention and transport of sulfonamides (SAs) in subsurface can strongly affect groundwater quality. In this work, a range of laboratory batch sorption and column transport experiments were conducted to determine the effect of cation type in mixed Ca-Na systems on the retention and transport of two typical SAs, sulfadimethoxine (SDM) and sulfacetamide (SCA), in saturated limestone porous media. Column experimental data showed divalent cation Ca²⁺ played a more important role than monovalent cation Na⁺ in decreasing the transport of only SDM in co-cation systems in the saturated limestone media. Further, in the single-cation (i.e., including either Ca²⁺ or Na⁺) system, increasing ionic strength (IS) of either NaCl or CaCl₂ had little effect on SCA transport; however, increasing of IS of CaCl₂ promoted the retention of SDM in the saturated limestone porous media. This is mainly due to the cation bridging effect of Ca²⁺ on SDM and limestone. Overall, SDM showed much higher retention in the limestone columns than SCA, which can be attributed to the two SAs' different physicochemical properties. Moreover, limestone showed stronger ability to retain the two SAs than quartz sand. Findings in this study suggest that cation type and the concentration of certain electrolyte (e.g., CaCl₂) as well as medium type play an important role in controlling the environmental fate and transport of antibiotics.

Environmental fate and microbial effects of monensin, lincomycin, and sulfamethazine residues in soil

The impact of commonly-used livestock antibiotics on soil nitrogen transformations under varying redox conditions is largely unknown. Soil column incubations were conducted using three livestock antibiotics (monensin, lincomycin and sulfamethazine) to better understand the fate of the antibiotics, their effect on nitrogen transformation, and their impact on soil microbial communities under aerobic, anoxic, and denitrifying conditions. While monensin was not recovered in the effluent, lincomycin and sulfamethazine concentrations decreased slightly during transport through the columns. Sorption, and to a limited extent degradation, are likely to be the primary processes leading to antibiotic attenuation during leaching. Antibiotics also affected microbial respiration and clearly impacted nitrogen transformation. The occurrence of the three antibiotics as a mixture, as well as the occurrence of lincomycin alone affected, by inhibiting any nitrite reduction, the denitrification process. Discontinuing antibiotics additions restored microbial denitrification. Metagenomic analysis indicated that Proteobacteria, Bacteroidetes, Actinobacteria, and Chloroflexi were the predominant phyla observed throughout the study. Results suggested that episodic occurrence of antibiotics led to a temporal change in microbial community composition in the upper portion of the columns while only transient changes occurred in the lower portion. Thus, the occurrence of high concentrations of veterinary antibiotic residues could impact nitrogen cycling in soils receiving wastewater runoff or manure applications with potential longer-term microbial community changes possible at higher antibiotic concentrations.

Fluoroquinolones in agricultural soils: Multi-temporal variation and risks in Rio de Janeiro upland region

Our main goal was to investigate the potential accumulation of fluoroquinolones (FQs) in agricultural soils over extended periods of land use, predicting leaching and estimating risk quotients for soil microorganisms. Short to long-term of poultry litter fertilization (<1-30 years) were evaluated for enrofloxacin (ENR) and ciprofloxacin (CIP) input, in addition to the emergence of plasmid-mediated quinolone resistance (PMQR) genes. High FQs concentration (range 0.56-100 mg kg^-1) were measured in poultry litter samples. In soils, FQs occurrence and risks have changed over the years. An accumulation trend was observed between short and medium-term fertilized soils (ST and MT soils), reaching a range of 330-6138 μg kg^-1 ENR and 170-960 μg kg^-1 CIP in MT soil, followed by decreased concentrations in long-term fertilized soils (LT soils). The environmental risk assessment showed a high ENR risk quotient (RQ ≥ 1) in ST and MT soils ranging (7-226) and high CIP risk (9-53) in LT soils. The detection of qnrS genes in the area with the lowest FQs concentration emphasizes the importance of a broader approach to environmental assessment, in which not only target compounds are considered. FQs soil-water migration model pointed out a high leaching risk in ST soil. To reduce risks, management measures to decrease antibiotic environmental load should be taken before poultry litter application. In addition, the high weathering of tropical soils contributing to possible fate of antibiotics to water resources through drainage basins should be considered.

Sorption behaviors of antimicrobial and antiparasitic veterinary drugs on subtropical soils

Brazil is one of the world's largest producers of animal protein, requiring the large-scale use of veterinary drugs. The administration of antimicrobials and antiparasitics is a common practice. However, there is a lack of information on how these drugs impact the environment. Antimicrobials are capable of altering the soil microbial population and are responsible for the development of multidrug-resistant microbial strains. Therefore, it is important to evaluate the fate and transport of these compounds in the environment, and one parameter used for this purpose is the soil-water partition coefficient. In this work, an assessment was made of the soil sorption behaviors of 18 drugs from seven different families, including antimicrobials (sulfonamides, fluoroquinolones, amphenicols, and macrolides) and antiparasitic drugs (milbemycin, avermectins, and benzimidazoles). Seven subtropical soils of different textural classes were tested. The Freundlich sorption coefficients, expressed as μg^1-1/n (cm³)^1/n g^-1, were in the following ranges: 0.45 to 19 (sulfonamides), 72 to 2410 (fluoroquinolones), 9 to 58 (thiabendazole), 0.03 to 0.48 (florfenicol), 105 to 424 (moxidectin), 14 to 184 (avermectins), and 1.5 to 74 (macrolides). The results showed that the drugs belonging to the same family, with chemical structures in common, presented similar behaviors regarding sorption and desorption, for the different soils tested and are generally in agreement with soils from temperate regions. The data set obtained in this work give an overview of the fate of the veterinary drugs in Brazilian subtropical soils with different textures and composition and can be very helpful for exposure risk assessments.

Transport of Potential Manure Hormone and Pharmaceutical Contaminants through Intact Soil Columns

Although adding manure to agricultural soils is a commonly practiced disposal method and a means to enhance soil productivity, potential environmental contamination by any associated chemicals of emerging concern (CECs) such as hormones and pharmaceuticals is not well understood. Our objective was to provide field-relevant predictions of soil transport and attenuation of 19 potential manure CECs using undisturbed soil columns irrigated under unsaturated conditions. The CEC concentrations in leached water were monitored for 13 wk using high performance liquid chromatography-time of flight-mass spectrometry (HPLC-TOF-MS), after which time soil in the cores was removed and sampled for extractable CECs. Compounds quantified in column leachate included all four of the added sulfonamide antibiotics and the nonsteroidal, anti-inflammatory drug flunixin. Only trace amounts of several of the seven hormones, five remaining antibiotics, and two antimicrobials leached from the columns from exogenous soil additions. Soil residues of all 19 compounds were detected, with highest extractable amounts for 17α-hydroxyprogesterone > triclosan (antimicrobial) > flunixin > oxytetracycline. Those CECs with the highest recoveries as calculated by summing leached and extractable amounts were flunixin (14.5%), 17α-hydroxyprogesterone (5.3%), triclosan (4.6%), and sulfadimethoxine (4.8%). Manure management to prevent CEC contamination should consider the potential environmental problems caused by negatively charged compounds with the greatest mobility (flunixin and sulfadimethoxine) and those that have long residence times in soil (triclosan, 17α-hydroxyprogesterone, flunixin, and oxytetracycline). Flunixin is particularly important given its mobility and long residence time in soil.

Occurrence of seventeen veterinary antibiotics and resistant bacterias in manure-fertilized vegetable farm soil in four provinces of China

This study focused on the occurrence of seventeen veterinary antibiotics and six resistant bacterias in soils from the vegetable farms fertilized with animal manure in China. Seventeen veterinary antibiotics, including sulfonamides, quinolones, tetracyclines, macrolides and amphenicols, were detected by high performance liquid chromatography/tandem mass spectrometer in all the 53 soil samples collected in four provinces during August 2016. The concentrations of target antibiotics in the soil samples ranged from not detectable to 415.00 μg/kg dry weight with the mean residual levels of the five classes followed order: tetracyclines (82.75 μg/kg) > quinolones (12.78 μg/kg) > macrolides (12.24 μg/kg) > sulfonamides (2.61 μg/kg) > amphenicols (0.06 μg/kg). Moreover, the highest antibiotic levels were found mainly in soil from organic vegetable farms. Risk assessment by using the methods of risk quotient, suggested that oxytetracycline, chlortetracycline, enrofloxacin and ciprofloxacin could pose severe ecological risk in sampled soils. Resistant strains were isolated in 30 samples, with Escherichia coli and Klebsiella pneumonia found the dominant bacterial hosts with resistance genes. Antibiotic resistance genes, including tetA, tetB, qnrS, oqxA, sul1, sul2, ermA and floR, were detected in the strains resistant to: tetracyclines, quinolones, sulfonamides, macrolides and amphenicols resistance, respectively. Overall, there was a correlation between the results of antibiotic risk assessment with the detection of resistance genes from isolated strains in the soils.