A framework for assessing the retardation of organic molecules in groundwater: Implications of the species distribution for the sorption-influenced transport

Assessment of potential mobility of selected micropollutants in agricultural soils of the Czech Republic using their sorption predicted from soil properties

The sorption of organic contaminants in soils and sediment is a crucial factor affecting their mobility in the vadose zone environment. The Freundlich sorption isotherms were evaluated for eleven micropollutants and eight soils. The highest Freundlich sorption coefficients, K_F, were obtained for triclosan (324 ± 153 cm^3/nμg^1-1/ng^-1) followed by sertraline (120 ± 74), venlafaxine (74.3 ± 41.2), telmisartan (33.3 ± 13.6), atorvastatin (8.66 ± 4.78), bisphenol S (8.03 ± 4.87), lamotrigine (6.92 ± 3.02), 2-phenylbenzimidazole-5-sulfonic acid (3.77 ± 2.25), memantine (3.42 ± 1.64), 1-methyl-1H-benzotriazole (2.05 ± 0.99), and valsartan (0.88 ± 0.89). The K_F values for the individual compounds were correlated with soil properties. Multiple linear regressions were used to derive equations for predicting the K_F values using the soil properties. The first set of equations contained mainly properties with the strongest correlations with the K_F values, e.g., a base cation saturation for positively charged compounds or a hydrolytic acidity for negatively charged compounds. The second set of equations contained properties included in the map of agricultural soils of the Czech Republic. These equations always indicated positive correlations with oxidizable organic carbon and clay content. They also included either a negative or positive correlation with pH_KCl. A positive correlation with pH_KCl was obtained for venlafaxine, memantine, and sertraline, which were mostly positively charged. A negative correlation with pH_KCl was obtained for the remaining compounds. The second set of equations, the soil map, and the database of soil properties were used to predict the K_F value distributions within the Czech agricultural soils. It resulted in similar K_F distributions' patterns for valsartan, lamotrigine, atorvastatin, and telmisartan (with a positive correlation between K_F and hydrolytic acidity), which considerably differed from the K_F patterns for the other compounds. These maps were used to delineate areas with a leaching potential of the compounds toward groundwater that will serve as a tool for assessing a potential groundwater vulnerability.

Primary and ultimate degradation of benzophenone-type UV filters under different environmental conditions and the underlying structure-biodegradability relationships

Ten common benzophenone-based UV filters (BPs), sharing the same basic structure and differing only in their substituents, were investigated with respect to their primary and ultimate biodegradability. This study was carried out in order to gain deeper insights into the relationship between structure and biodegradability. The primary biodegradation of the selected BPs was studied in river water at environmentally relevant concentrations (1 µg/L) while varying specific, crucial environmental conditions (aerobic, suboxic, supplementation of nutrients). For this purpose, both batch and column degradation tests were performed, which allowed a systematic study of the effects. Subsequently, the ultimate biodegradation, i.e. the potential to achieve full mineralization of BPs, was examined according to OECD guideline 301 F. The results indicate that mineralization is limited to derivatives in which both aromatic rings contain substituents. This hypothesis was supported by docking simulations showing systematic differences in the orientation of BPs within the active site of the cytochrome P450 enzyme. These differences in orientation correspond to the substitution pattern of the BPs. This study provides valuable insights for assessing the environmental hazards of this class of trace organic compounds.

Antibiotics, antibiotic resistance and associated risk in natural springs from an agroecosystem environment

This study investigates the occurrence, transport, and risks associated to antibiotic residues, antibiotic resistance genes (ARGs) and antibiotic resistant Escherichia coli (AR-E. coli) in eleven natural springs in an agroecosystem environment with intense livestock production, where groundwater nitrate concentration usually sets above 50 mg L^-1. Out of 23 multiple-class antibiotics monitored, tetracycline and sulfonamide residues were the most ubiquitous, and they were detected at concentrations ranging from ng L^-1 to μg L^-1. Five ARGs were monitored, conferring resistance to the antibiotic classes of major use in livestock production. Thus, genes conferring resistance to sulfonamides (sul1 and sul2) and tetracyclines (tetW) as well as a gene proxy for anthropogenic pollution (intI1) were present in most springs. sul1 was the most abundant, with absolute concentrations ranging from 4 × 10² to 5.6 × 10⁶ gene copies L^-1 water. AR-E. coli showing resistance to sulfonamides and tetracyclines was also detected, with a prevalence up to approximately 40 % in some sites but with poor correlations with the concentration of antibiotic residues and ARGs. The occurrence of antibiotics, ARGs and AR-E. coli was characterized by large seasonal variations which were mostly associated to both hydrological factors and reactive transport processes. Finally, a risk assessment approach pointed out towards low risk for both the groundwater environment and human health, when spring water is used for direct human consumption, associated with the occurrence of antibiotics, ARGs and AR-E. coli. However, long-term effects cannot be neglected, and proper actions must be taken to preserve groundwater quality.

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.

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.

Analytical method to monitor contaminants of emerging concern in water and soil samples from a non-conventional wastewater treatment system

Nonconventional wastewater treatments, such as vegetation filters (VFs), are propitious systems to attenuate contaminants of emerging concern (CECs) in small municipalities. The development of standardised multiresidue and multimatrix methods suitable for measuring a reliable number of CEC in environmental samples is crucial for monitoring infiltrating concentrations and for ensuring these systems' treatment capacity. The objective of this study is to develop and validate an analytical method for the simultaneous determination of CECs, including transformation products (TPs), with diverse physico-chemical properties, in environmental samples. The optimised method is based on sample clean-up and preconcentration by solid-phase extraction (SPE), followed by liquid chromatography electrospray ionization tandem mass spectrometry (LC-MS/MS). The method is able to detect and quantify 40 target CECs, including pharmaceuticals of different classes (analgesics, antibiotics, antihypertensives, lipid regulators, anticonvulsants, antidepressants, antiarrhythmics, beta-blockers, amongst others), hormones and lifestyle products with good reproducibility (variations below 23%), in different water matrices, and 28 CECs, in soil samples. Acceptable recoveries (65-120%) were obtained for most of the CECs in all the matrices. However in the soil samples, as complexity required a prior extraction treatment, the recovery of some analytes was affected, which reduced the number of target CECs. The achieved methodological quantification limits (0.05-5 ng/L and 0.04-1.1 ng/g levels for the water and the soil matrices, respectively) were reasonably low for most CECs. The proposed method was successfully applied to monitor CECs in a VF. The CECs detected at higher concentrations are some of the world's most widely used products (e.g. acetaminophen or caffeine and its main TP, paraxanthine). The results showed an almost 70% reduction in CEC concentrations during infiltration. The groundwater data indicated that the VF treatment operation did not affect the underlying aquifer (Cmax found in GW <1 µg/L).

Contaminants of emerging concerns in recycled water: Fate and risks in agroecosystems

Recycled water (RW) has been increasingly recognized as a valuable source of water for alleviating the global water crisis. When RW is used for agricultural irrigation, many contaminants of emerging concern (CECs) are introduced into the agroecosystem. The ubiquity of CECs in field soil, combined with the toxic, carcinogenic, or endocrine-disrupting nature of some CECs, raises significant concerns over their potential risks to the environment and human health. Understanding such risks and delineating the fate processes of CECs in the water-soil-plant continuum contributes to the safe reuse of RW in agriculture. This review summarizes recent findings and provides an overview of CECs in the water-soil-plant continuum, including their occurrence in RW and irrigated soil, fate processes in agricultural soil, offsite transport including runoff and leaching, and plant uptake, metabolism, and accumulation. The potential ecological and human health risks of CECs are also discussed. Studies to date have shown limited accumulation of CECs in irrigated soils and plants, which may be attributed to multiple attenuation processes in the rhizosphere and plant, suggesting minimal health risks from RW-fed food crops. However, our collective understanding of CECs is rather limited and knowledge of their offsite movement and plant accumulation is particularly scarce for field conditions. Given a large number of CECs and their occurrence at trace levels, it is urgent to develop strategies to prioritize CECs so that future research efforts are focused on CECs with elevated risks for offsite contamination or plant accumulation. Irrigating specific crops such as feed crops and fruit trees may be a viable option to further minimize potential plant accumulation under field conditions. To promote the beneficial reuse of RW in agriculture, it is essential to understand the human health and ecological risks imposed by CEC mixtures and metabolites.

Assessment of the occurrence of 455 pharmaceutical compounds in sludge according to their physical and chemical properties: A review

Sludge agronomical reuse is of major interest due to the beneficial contribution of nutrients. However, it implies the introduction of unregulated pharmaceuticals into amended-soils and creates a controversial issue about sludge management. To limit their dissemination, it is essential to identify the compounds of interest and understand their attenuation mechanisms through the sludge processes. This paper summarizes the knowledge on 455 investigated pharmaceuticals among 32 therapeutical categories in amendable sludge matrices. It contributes to enlarging the list of commonly quantified compounds to 305 residues including 84 additional compounds compared to previous reviews. It highlights that sorption appears as the main mechanism controlling the occurrence of pharmaceuticals in sludge matrices and shows the considerable residual levels of pharmaceuticals reaching several mg/kg in dry weight. Antibiotics, stimulants, and antidepressants show the highest concentrations up to 232 mg/kg, while diuretics, anti-anxieties or anticoagulants present the lowest concentrations reaching up to 686 µg/kg. Collected data show the increase in investigated compounds as antifungals or antihistamines, and underline emerging categories like antidiabetics, antivirals, or antiarrhythmics. The in-depth analysis of the substantial database guides onto the pharmaceuticals that are the most likely to occur in these amendable matrices to assist future research.

A novel multiscale biophysical model to predict the fate of ionizable compounds in the soil-plant continuum

Soil pollution from emerging contaminants poses a significant threat to water resources management and food production. The development of numerical models to describe the reactive transport of chemicals in both soil and plant is of paramount importance to elaborate mitigation strategies. To this aim, in the present study, a multiscale biophysical model is developed to predict the fate of ionizable compound in the soil-plant continuum. The modeling framework connects a multi-organelles model to describe processes at the cell level with a semi-mechanistic soil-plant model, which includes the widely used Richards-based solver, HYDRUS. A Bayesian probabilistic framework is used to calibrate and assess the capability of the model in reproducing the observations from an experiment on the translocation of five pharmaceuticals in green pea plants. Results show satisfactory fitting performance and limited predictive uncertainty. The subsequent validation with the cell model indicates that the estimated soil-plant parameters preserve a physically realistic meaning, and their calibrated values are comparable with the existing literature values, thus confirming the overall reliability of the analysis. Model results further suggest that pH conditions in both soil and xylem play a crucial role in the uptake and translocation of ionizable compounds.

Seasonal and spatial dynamics of selected pesticides and nutrients in a small lake catchment - Implications for agile monitoring strategies

Intensive anthropogenic pressure such as high inputs of nutrients and pesticides severely threaten most European water bodies. Small catchments ≤10 km² are not monitored under the Water Framework Directive but play an important role in freshwater ecosystems. The high complexity in seasonal and spatial dynamics require more than a one-size-fits-all approach in water quality monitoring. Often located in rural areas with a high agricultural activity, small catchments often carry high amounts of nutrients, pesticides and their transformation products affecting drinking water resources. With a low-cost approach of a monthly sampling campaign over the course of one year combined with meaningful indicators for potential pollution sources within the catchment this study could elucidate catchment dynamics and two hotspots for pesticides and nutrients. Two different groups of pesticides were observed (I) pesticides on long-term use which were applied in high amounts over the last decades (e.g., chloridazon and its transformation products) and (II) pesticides on short-term use, newly introduced into the market. Especially transformation products of pesticides from group (I) together with nitrate showed a steady release from two fields into the receiving water bodies over the year, probably being stored in the soil layers over the years of application slowly leaching out. Pesticides from group (II) showed a strong seasonality, released from another hotspot area probably due to run-off shortly after application. Streamlining this knowledge into targeted measures and an agile monitoring strategy for the respective catchments may allow a sustainable improvement of water quality and a better ecosystem protection.

Use of a large dataset to develop new models for estimating the sorption of active pharmaceutical ingredients in soils and sediments

Information on the sorption of active pharmaceutical ingredients (APIs) in soils and sediments is needed for assessing the environmental risks of these substances yet these data are unavailable for many APIs in use. Predictive models for estimating sorption could provide a solution. The performance of existing models is, however, often poor and most models do not account for the effects of soil/sediment properties which are known to significantly affect API sorption. Therefore, here, we use a high-quality dataset on the sorption behavior of 54 APIs in 13 soils and sediments to develop new models for estimating sorption coefficients for APIs in soils and sediments using three machine learning approaches (artificial neural network, random forest and support vector machine) and linear regression. A random forest-based model, with chemical and solid descriptors as the input, was the best performing model. Evaluation of this model using an independent sorption dataset from the literature showed that the model was able to predict sorption coefficients of 90% of the test set to within a factor of 10 of the experimental values. This new model could be invaluable in assessing the sorption behavior of molecules that have yet to be tested and in landscape-level risk assessments.

Occurrence, effects and behaviour of the antibiotic lincomycin in the agricultural and aquatic environment - A review

Lincomycin, an antibiotic commonly used in veterinary medicine, is frequently detected within the agricultural environment. The active compound enters the aquatic environment after manure application via infiltration or surface run-off, where it may negatively affect non-target organisms and contribute to the development and spread of resistant genes. However, a review on the fate of lincomycin within the agricultural and aquatic environment is lacking. Hence, to provide an overview, the main part of this paper summarizes the current literature on the occurrence, effects and behaviour of lincomycin in all relevant environmental compartments, including manure, soil, surface water and groundwater. Lincomycin was regularly detected in all environmental compartments and even in the food chain, appeared to sorb temporarily and mainly in its cationic microspecies, and dissipated after time periods that could cover days, months, or years, depending on the compartment and conditions. As noticed during the literature research conducted, information on the attenuation of lincomycin in terms of biological degradation in the aquatic environment is widely lacking, although it seems that biodegradation is the major removal mechanism. Therefore, a laboratory study, implemented by means of batch experiments, was carried out in order to evaluate the biological degradation of lincomycin in the aquatic environment. First order degradation started after a start-up phase of 10-14 days with a degradation rate constant of 0.55 d^-1 and a half-life time of 30 h. Further, the degradation rate constant was found to be independent of initial concentrations as long as concentrations did not exceed a concentration level at which the bacteria were inhibited, as it was the case in this study at a concentration of 10 mg L^-1. Biodegradation was confirmed as an important degradation pathway for LIN in the aquatic environment.

Mobility of organic compounds in a soft clay-rich rock (Tégulines clay, France)

The migration of organic compounds in soils is a major concern in several environmental issues. Contaminants display distinct behaviours as regards to their specific affinities towards soils constituents. The retention mechanism of hydrophobic compounds by natural organic matter is well known. The retention of ionizable compounds is mainly related to oxides and clay minerals, even if less documented in reductive media. In this work, we investigated the migration of organic compounds in a soft clay-rich sedimentary rock (Tégulines clay, France). The aim was to determine the relative contributions of natural sorbents on retention, and eventual correlations with solutes properties. Both hydrophobic compounds (toluene, benzene, naphthalene) and hydrophilic species (adipate, oxalate, ortho-phthalate, benzoate) were investigated, using batch and diffusion experiments. The retention of neutral aromatic compounds correlates with their lipophilicity (log P_OW), confirming that absorption mechanism prevails, despite a low content of natural organic matter (≤0.5%). A low retention of ionizable compounds was quantified on Tégulines clay. The eventual discrepancies between data acquired on crushed rock and solid samples are discussed. Low effective diffusion coefficients are quantified. These values hint on the relative contributions of steric and electrostatic exclusion, despite a large pore size in such "soft" clay-rock. Overall, the dataset illustrates a general scheme for assessing the migration over a wide variety of organic compounds. This approach may be useful for predictive modelling of the fate of organic compounds in environmental media.

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

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

How microbial community composition, sorption and simultaneous application of six pharmaceuticals affect their dissipation in soils

Pharmaceuticals may enter soils due to the application of treated wastewater or biosolids. Their leakage from soils towards the groundwater, and their uptake by plants is largely controlled by sorption and degradation of those compounds in soils. Standard laboratory batch degradation and sorption experiments were performed using soil samples obtained from the top horizons of seven different soil types and 6 pharmaceuticals (carbamazepine, irbesartan, fexofenadine, clindamycin and sulfamethoxazole), which were applied either as single-solute solutions or as mixtures (not for sorption). The highest dissipation half-lives were observed for citalopram (average DT_50,S for a single compound of 152 ± 53.5 days) followed by carbamazepine (106.0 ± 17.5 days), irbesartan (24.4 ± 3.5 days), fexofenadine (23.5 ± 20.9 days), clindamycin (10.8 ± 4.2 days) and sulfamethoxazole (9.6 ± 2.0 days). The simultaneous application of all compounds increased the half-lives (DT_50,M) of all compounds (particularly carbamazepine, citalopram, fexofenadine and irbesartan), which is likely explained by the negative impact of antibiotics (sulfamethoxazole and clindamycin) on soil microbial community. However, this trend was not consistent in all soils. In several cases, the DT_50,S values were even higher than the DT_50,M values. Principal component analyses showed that while knowledge of basic soil properties determines grouping of soils according sorption behavior, knowledge of the microbial community structure could be used to group soils according to the dissipation behavior of tested compounds in these soils. The derived multiple linear regression models for estimating dissipation half-lives (DT_50,S) for citalopram, clindamycin, fexofenadine, irbesartan and sulfamethoxazole always included at least one microbial factor (either amount of phosphorus in microbial biomass or microbial biomarkers derived from phospholipid fatty acids) that deceased half-lives (i.e., enhanced dissipations). Equations for citalopram, clindamycin, fexofenadine and sulfamethoxazole included the Freundlich sorption coefficient, which likely increased half-lives (i.e., prolonged dissipations).

Trace organic contaminants in field-scale cultivated alfalfa, soil, and pore water after 10 years of irrigation with reclaimed wastewater

Several studies have assessed the presence of trace organic contaminants (TrOCs) in reclaimed wastewater and their uptake into crops but there are limited data from field-scale studies. In this research, we studied the fate of 12 TrOCs in wastewater samples, 11 in plants and in soil pore water, and 10 in soil at an agricultural research farm, which was irrigated with reclaimed wastewater for more than 10 years. First, we examined the presence of the compounds in the primary, secondary, and treated effluent of a regional water reclamation facility which provides the irrigation water. The agricultural field produced alfalfa, and we measured the contaminants in the alfalfa, soil, and pore water. Reclaimed wastewater contained 11 of 12 TrOCs, with concentrations ranging from 26 ± 9 ng/L (DEET) to 1539 ± 1899 ng/L (trimethoprim). Atrazine was not detected. Pore water collected during non-irrigating periods contained all analyzed TrOCs, from 3 ± 0.1 ng/L (diphenhydramine) to 343 ± 360 ng/L (primidone). TrOCs measured in pore water samples indicated that they may leach to shallow groundwater even when fields are not being irrigated. Soils from 0 to 60 cm contained nine TrOCs from below the reporting limit (fluoxetine) to 329 ng/g (carbamazepine). Atrazine was not detected. TrOC concentrations decreased with increasing soil depth, except carbamazepine, which was more recalcitrant. Nine TrOCs were present in the shoots and leaves of alfalfa grown in the reclaimed wastewater irrigated plots, at concentrations ranging from <1 ng/g (diphenhydramine and fluoxetine) to 49 ng/g dry weight (carbamazepine). Atrazine and caffeine were not detected. We estimated that a maximum of 14% of DEET from the reclaimed wastewater was accumulated in alfalfa. Overall, despite some accumulation of TrOCs in the soil, alfalfa uptake was limited, which results in low exposure to foraging animals.

Screening and Distribution of Contaminants of Emerging Concern and Regulated Organic Pollutants in the Heavily Modified Guadalhorce River Basin, Southern Spain

Emerging pollutants have aroused an increasing concern due to their ubiquitous presence in the environment and harmful potential. Both emerging (e.g., pharmaceuticals and personal care products) and regulated organic pollutants pose a serious threat to water quality and their presence and spatial distribution are complicated to address as they can derive from several factors: distribution of point and diffuse sources, environmental conditions, hydrogeological features of the region and inherent properties of the considered contaminants. In this study, a ground and surface water monitoring campaign was conducted in the three main detritic groundwater bodies of an extensive and heavily modified river basin in order to draft an initial description of the occurrence and distribution of a wide range of organic contaminants. In total, 63 out of 185 target pollutants were detected. An attempt to understand the importance of different factors governing the distribution of some of the most frequently found pollutants was made. Antibiotics spatial distribution is potentially influenced by the hydrogeological functioning of the basin modified by hydraulic infrastructures (reflected by hydrochemistry and environmental tracers δ2H and δ18O), not directly related to the distribution of potential sources. The presence of other organic pollutants does not reflect an evident correlation with flow pathways. Differences in contaminant occurrence are potentially attributed to the way pollutants are released into the environment as well as physico-chemical properties.

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.

Well-defined poly(ethylene glycol) polymers as non-conventional reactive tracers of colloidal transport in porous media

HYPOTHESIS

A prominent fraction of mobile organic matter in natural aqueous soil solutions is formed by molecules in sizes that seamlessly exceed the lower end of what is defined as a colloid. The hydrodynamics and the functional diversity of these molecules result in a transport behavior that is fundamentally different from smaller compounds. However, there is a lack of "reactive tracers" that allow for the study of colloidal transport phenomena appropriately. We hypothesize that tailor-made and well-defined synthetic polymers can overcome this limitation.

EXPERIMENTS

We prepared and characterized the hydrodynamic properties of water-soluble poly(ethylene glycol)s (PEG) and studied their adsorption to mixtures of quartz, illite, and goethite in batch and column experiments.

FINDINGS

We used this information to independently predict the transport of PEG with striking agreement to the observed mean breakthrough times in all porous media. As PEG transport can be comprehensively and quantitatively reconstructed, we conclude that functionalized PEGs are promising candidates to be used as tailorable and non-toxic tracers available in the size range of natural organic (macro-)molecules.

Effects of clay colloids on ciprofloxacin transport in saturated quartz sand porous media under different solution chemistry conditions

Antibiotics, a highly prevalent class of environmental organic pollutants, are becoming a matter of global concern. Clay minerals that are ubiquitous in subsurface environments may play an important role in the fate and transport of antibiotics. Taking ciprofloxacin (CIP) as a model antibiotic, this work explored the role of clay colloids (kaolinite and montmorillonite) on the adsorption and transport of CIP under different chemical solution conditions. The adsorption isotherms showed that montmorillonite colloids had a larger CIP sorption capacity than kaolinite colloids. The results of transport experiments indicated that montmorillonite colloids could promote CIP transport in saturated sand columns, but the addition of kaolinite colloids affected CIP mobility to a much smaller extent. The much stronger transport-enhancement effect of montmorillonite colloids was due to CIP adsorbed strongly to the colloids and desorption hysteresis of colloid-adsorbed CIP, likely stemming from the intercalation of this antibiotic in the interlayer of montmorillonite. Interestingly, transport of clay colloids increased with the increasing pH from 5.0 to 9.0; however, CIP transport decreased with the increasing pH in the presence of clay colloids. The observations were likely attributable to pH-dependent ciprofloxacin adsorption/desorption to clay minerals. Increasing the concentrations of NaCl and CaCl₂ generally decreased the contaminant-mobilizing ability of montmorillonite colloids, mainly by increasing the aggregation of colloids and thus, decreasing the transport of colloid-adsorbed CIP. Moreover, under the test conditions (1 mM NaCl and pH 7.0), the presence of CIP inhibited the transport of clay colloids due to the increase in aggregate size of clay colloids with the addition of CIP. Overall, these findings suggest that clay colloids with high adsorption abilities for antibiotics in the subsurface environment may act as a carrier for certain antibiotic compounds.

An analysis of the versatility and effectiveness of composts for sequestering heavy metal ions, dyes and xenobiotics from soils and aqueous milieus

The persistence and bioaccumulation of environmental pollutants in water bodies, soils and living tissues remain alarmingly related to environmental protection and ecosystem restoration. Adsorption-based techniques appear highly competent in sequestering several environmental pollutants. In this review, the recent research findings reported on the assessments of composts and compost-amended soils as adsorbents of heavy metal ions, dye molecules and xenobiotics have been appraised. This review demonstrates clearly the high adsorption capacities of composts for umpteen environmental pollutants at the lab-scale. The main inferences from this review are that utilization of composts for the removal of heavy metal ions, dye molecules and xenobiotics from aqueous environments and soils is particularly worthwhile and efficient at the laboratory scale, and the adsorption behaviors and effectiveness of compost-type adsorbents for agrochemicals (e.g. herbicides and insecticides) vary considerably because of variabilities in structure, topology, bond connectivity, distribution of functional groups and interactions of xenobiotics with the active humic substances in composts. Compost-based field-scale remediation of environmental pollutants is still sparse and arguably much challenging to implement if, furthermore, real-world soil and water contamination issues are to be addressed effectively. Hence, significant research and process development efforts should be promptly geared and intensified in this direction by extrapolating the lab-scale findings in a cost-effective manner.

Modeling carbamazepine transport in wastewater-irrigated soil under different land uses

The pharmaceutical compound carbamazepine (CBZ) is a contaminant of emerging concern. Wastewater irrigation can be a long-term, frequent source of CBZ; therefore, understanding the fate and transport of CBZ as a result of wastewater reuse practices has important environmental implications. The objective of this study was to estimate long-term soil transport of CBZ originating from treated wastewater irrigation on plots under different land uses. Field data from a previous study comparing CBZ concentrations in soil under different land uses were used in numerical modeling with HYDRUS-2D for the estimation of CBZ soil transport during 20 yr of irrigation with treated wastewater. This study showed high CBZ retention in soil under all investigated land uses. Adequate modeling results were obtained by using soil organic carbon-water partitioning coefficient (K_oc ) for the CBZ linear sorption coefficient (K_d ) estimation, yet an underestimation of CBZ concentration in soil was still noted. Thus, results suggest that, although highly important, organic carbon content is probably not the only soil property governing CBZ sorption at this site, indicating the potential research perspective. Modeling results showed wastewater irrigation containing CBZ for 20 yr increased the CBZ concentration in the soil profile and its vertical movement, with the slowest vertical transport rate occurring on the forested plots. Overall results suggest that a beneficial management practice could be to increase soil organic carbon (e.g., compost addition) when using treated wastewater for irrigation in order to retain CBZ in the surface soil and thus limit its leaching through the soil profile.

Solute Reactive Tracers for Hydrogeological Applications: A Short Review and Future Prospects

Tracer testing is a mature technology used for characterizing aquatic flow systems. To gain more insights from tracer tests a combination of conservative (non-reactive) tracers together with at least one reactive tracer is commonly applied. The reactive tracers can provide unique information about physical, chemical, and/or biological properties of aquatic systems. Although, previous review papers provide a wide coverage on conservative tracer compounds there is no systematic review on reactive tracers yet, despite their extensive development during the past decades. This review paper summarizes the recent development in compounds and compound classes that are exploitable and/or have been used as reactive tracers, including their systematization based on the underlying process types to be investigated. Reactive tracers can generally be categorized into three groups: (1) partitioning tracers, (2) kinetic tracers, and (3) reactive tracers for partitioning. The work also highlights the potential for future research directions. The recent advances from the development of new tailor-made tracers might overcome existing limitations.

Sorption of ionic and neutral species of pharmaceuticals to loessial soil amended with biochars

To clarify the impact of biochar amendment on soil sorption for coexisting pharmaceuticals, wheat straw-derived biochars pyrolyzed at 300 and 700 °C (labeled as WS300 and WS700, respectively) were prepared. Batch experiments on ketoprofen (KTP), atenolol (ATL) and carbamazepine (CBZ) sorption to biochars, loessial soil and biochar-amended soils were conducted. The results indicated that sorption affinity of different species of pharmaceuticals to WS300 and WS700 was in the order of cationic ATL > neutral CBZ > anionic KTP. Cationic ATL had the highest sorption to biochars due to electrostatic attraction. Coexisting ATL, CBZ and KTP competed for the shared adsorption sites on carbonized phase of biochars, and π-π interactions were proposed to be the main sorption mechanism. Sorption coefficients (K_d) and nonlinearity of ATL, CBZ and KTP to soil increased when biochar was added (5% by weight), especially for WS700 with higher specific surface area. K_d values of the three pharmaceuticals to WS700-amended soil in either single solute or bisolute system were one to two orders of magnitude higher than those to soil, indicating the promoting role of WS700 in sorption of coexisting pharmaceuticals in soil. The study demonstrated the enhanced and competitive sorption of ionic and neutral species of pharmaceuticals to soil amended with biochars, which is helpful in designing biochar as effective sorbents for immobilization of pharmaceuticals in soil remediation.

Soil influences on uptake and transfer of pharmaceuticals from sewage sludge amended soils to spinach

Sewage sludge from wastewater treatment plants, which may contain various contaminants including pharmaceuticals, is often used as a soil amendment. These contaminants may subsequently be taken up by plants. In the present study we examined uptake of select pharmaceuticals from sewage sludge applied to soils by spinach plants. Seven soils were amended with sewage sludge from two wastewater treatment plants (A and B). Concentrations of compounds in plant tissues (roots and leaves) of spinach planted 45 days in these soils under greenhouse conditions were evaluated after harvest. The largest bioaccumulation in the roots and leaves was observed for sertraline (bioaccumulation factors (BAF) of 3.3-37.9 and 1-13.4, respectively), tramadol (1.3-10.0 and 4.8-30.0), and carbamazepine (2.2-17.2 and 6.1-48.8) and its metabolite carbamazepine 10,11-epoxide (not-quantified to 7.3 and 9.3-96.7). Elevated bioaccumulation in spinach roots was also identified for telmisartan (3.0-20.3) and miconazole (4.3-15.1), and leaves for metoprolol acid (not-quantified to 24.3). BAF values resulting from application of sludge B were similar to or moderately higher than BAFs from sludge A. The BAF values of carbamazepine and carbamazepine 10,11-epoxide in all tissues were negatively correlated with soil cation exchange capacity (CEC). This negative correlation between BAF and CEC was also observed for tramadol (A-roots and B-leaves), citalopram (B-roots), and telmisartan (B-roots) or between BAF and clay content for metoprolol acid (A-leaves and B-roots), tramadol (B-roots and A-leaves) and venlafaxine (B-roots). However, in the case of some other compounds (i.e. sertraline, amitriptyline, mirtazapine, metoprolol), uptake and the subsequent translocation and transformation from 3 soils of a higher pH and base cation saturation (Stagnic Chernozem Siltic, Haplic Chernozem and Greyic Phaeozem) significantly differed from 4 soils with a lower pH and base cation saturation (Haplic Luvisol, Haplic Cambisol, Dystric Cambisol and Arenosol Epieutric). Such observations proved strong compound dependent influences of soil conditions on various compounds bioaccumulations in plants and necessity of studying these processes always in diverse soils.

Influence of agroforestry plant species on the infiltration of S-Metolachlor in buffer soils

Agroforestry practices have been acknowledged for reducing pesticide losses while maintaining land productivity. Pesticide removal from overland flow results from great infiltration capacities of the buffer soils. This can in turn threaten the quality of groundwater in case of poor pesticide sorption and degradation in the root-influenced zone. These mechanisms and their balance are likely to be influenced by plant species. However, little is known about the role of agroforestry species in the infiltration of herbicides. The aim of this study was thereby to evaluate how popular agroforestry species modulate the infiltration of water and of a widely used herbicide. We established large buffer microcosms by planting Brome grass, Black walnut, Pin oak and Poplar trees in repacked soil columns. After a growth season of 4 months, we performed ponded infiltration experiments with bromide and S-Metolachlor. We used then the HYDRUS 1D model to compare the hydrodynamic properties and S-Metolachlor transport patterns between the microcosms. In addition, we compared the sorption properties of the rhizosphere and bulk soils. We found that the tree species increased the sorption of S-Metolachlor in soil with Kd being 3 times greater than in the un-vegetated and Brome grass microcosms. Poplar trees increased the hydraulic conductivity (Ksat) compared to the control and was associated to a low retardation of S-metolachlor, which increases the risk of groundwater contamination. With slightly reduced Ksat and retardation factor in the root zone, 1.6 to 1.8 times greater than in the control treatment, Black walnut appears as an optimal species for mitigating S-Metolachlor. The Brome grass and oak microcosms had the lowest Ksat of all treatments and S-Metolachlor retardation factors were equal and slightly increased compared to the control, respectively. These results show that agroforestry buffer's efficiency can be optimized by selecting appropriate species.

Sorption properties and behaviour at laboratory scale of selected pharmaceuticals using batch experiments

Despite the increasing public concern about the frequent occurrence of pharmaceuticals in the water bodies, their transport and fate are not yet well known; in particular in groundwater. In this laboratory study, batch experiments were conducted to investigate the sorption behaviour of selected pharmaceuticals. The choice of compounds was motivated by their chemical properties as well as by their occurrence at the relevant field sites. It included: antipyrine, atenolol, caffeine, carbamazepine, ciprofloxacin, diclofenac, ketoprofen, ofloxacin, and sulfamethoxazole. Sorption behaviour has already been investigated for some of these compounds (e.g. carbamazepine), but for the others (e.g. antipyrine, ketoprofen), extensive studies are missing so far. For the experiments, artificial and actual aquifer materials from complementary field sites were selected: technical coarse quartz sand and sediments from alluvial Vistrenque Aquifer, France (sandy loam), and fluvio-deltaic Baix Fluvià Aquifer, Spain (sandy clay loam, clay, and medium sand). In these field sites occurrence of pharmaceuticals in groundwater was previously stated, and the presented laboratory experiments were complementary to the field investigations. Five concentration steps for determining the sorption isotherms were investigated. Correlation analysis showed dependencies of K-coefficients of individual compounds and sediment properties; however, no clear, universal patterns for all compounds were found. Batch experiments suggest that sorption behaviour was governed by compound-specific properties rather than by sediment properties. These results contribute to the understanding sorption behaviour of pharmaceuticals in heterogeneous sediments, although some inconsistencies were revealed between laboratory scale results and field scale observations.

Assessment of trace metals in an aquifer with river-groundwater interaction: The influence of colloidal redistribution and porous matrix change on the migration of metals

An aquifer where receives steady lateral recharge from an AMD-polluted river, was chosen to understand the profound influence of the "solid-liquid phase" evolution on the mobility of trace metals. The results showed that the accumulation of trace metals in groundwater was observed near the riparian zone. Zn and Cd almost remained in the "truly dissolved" phase (<3 kDa), whereas Cu and Pb were mainly in the coarse colloid (0.22 μm-30 kDa) and shifted from the coarse colloid to the "truly dissolved" phase along the flow path. The evolution of relatively high dispersive colloids to low dispersive colloids indicated that the Al-rich mineral colloids as the dominance migrated with the groundwater flow path, and flocculated gradually so that the porous matrix was coated by gibbsite. The coating of gibbsite dissociates OH^- in acidic environment, resulting in the decreasing negative charge in porous matrix. Thus, the mobility of Cu and Pb was shifted from the colloid-facilitated transport to the co-precipitation with colloids, whereas the mobility of Zn and Cd was changed from the high electrostatic binding to the low electrostatic binding. Numerical simulation also confirmed the varying retardation factor and the total penetration time followed an order of Pb > Cu > Zn > Cd. Therefore, the changes in "two phases" in the aquifer-not only in water phase but also in colloid phase and porous matrix-have a profound influence on metal migration that take place in shallow groundwater where there are close hydraulic connection between river and groundwater.

Root uptake of atenolol, sulfamethoxazole and carbamazepine, and their transformation in three soils and four plants

Soils can be contaminated by pharmaceuticals. The aim of this study was to evaluate the impact of soil conditions (influencing sorption and persistence of pharmaceuticals in soils) and plant type on the root uptake of selected pharmaceuticals and their transformation in plant-soil systems. Four plants (lamb's lettuce, spinach, arugula, radish) planted in 3 soils were irrigated for 20 days (26) with water contaminated by one of 3 pharmaceuticals (carbamazepine, atenolol, sulfamethoxazole) or their mixture. The concentrations of pharmaceuticals and their metabolites in soils and plant tissues were evaluated after the harvest. Sulfamethoxazole and atenolol dissipated rapidly from soils. The larger concentrations of both compounds and an atenolol metabolite were found in roots than in leaves. Sulfamethoxazole metabolites were below the limits of quantifications. Carbamazepine was stable in soils, easily uptaken, accumulated, and metabolized in plant leaves. The efficiency of radish and arugula (both family Brassicaceae) in metabolizing was very low contrary to the high and moderate efficiencies of lamb's lettuce and spinach, respectively. Compounds' transformations mostly masked the soil impact on their accumulation in plant tissues. The negative relationships were found between the carbamazepine sorption coefficients and its concentrations in roots of radish, lamb's lettuce, and spinach.

Veterinary pharmaceutical residues from natural water to tap water: Sales, occurrence and fate

Veterinary pharmaceuticals (VPs) increasingly used in animal husbandry have led to their presence in aquatic environments -surface water (SW) or groundwater (GW) - and even in tap water. This review focuses on studies from 2007 to 2017. Sixty-eight different veterinary pharmaceutical residues (VPRs) have been quantified worldwide in natural waters at concentrations ranging from nanograms per liter (ng L^-1) to several micrograms per liter (μg L^-1). An extensive up-to-date on sales and tonnages of VPs worldwide has been performed. Tetracyclines (TCs) antibiotics are the most sold veterinary pharmaceuticals worldwide. An overview of VPRs degradation pathways in natural waters is provided. VPRs can be degraded or transformed by biodegradation, hydrolysis or photolysis. Photo-degradation appears to be the major degradation pathway in SW. This review then reports occurrences of VPRs found in tap water, and presents data on VPRs removal in drinking water treatment plants (DWTPs) at each step of the process. VPRs have been quantified in tap water at ng L^-1 concentration levels in four studies of the eleven studies dealing with VPRs occurrence in tap water. Overall removals of VPRs in DWTPs generally exceed 90% and advanced treatment processes (oxidation processes, adsorption on activated carbon, membrane filtration) greatly contribute to these removals. However, studies performed on full-scale DWTPs are scarce. A large majority of fate studies in DWTPs have been conducted under laboratory at environmentally irrelevant conditions (high concentration of VPRs (mg L^-1), use of deionized water instead of natural water, high concentration of oxidant, high contact time etc.). Also, studies on VPRs occurrence and fate in tap water focus on antibiotics. There is a scientific gap on the occurrence and fate of antiparatic drugs in tap waters.

Sorption of cationic organic substances onto synthetic oxides: Evaluation of sorbent parameters as possible predictors

Knowledge on the sorption behavior of cationic organic substances in aquatic systems is vital for their risk assessment due to the increasing detection of such chemicals in the hydrosphere. Their sorption behavior is strongly influenced by sorption processes onto mineral surfaces (e.g., oxides, clays). To contribute to the development of prediction tools, the impact of sorbent characteristics on the sorption strength was studied in a highly-idealized model system. In addition to the properties of the solid phase, the concentration of other ions in direct competition for sorption sites and the molecular structure of the sorbate were changed to separate ion exchange and non-ion exchange processes. The study includes in total 120 systematic column experiments using five extensively characterized synthetic oxides (three silica gels, two aluminum oxides), three probe molecules (two structurally related cationic substances, one neutral compound), and four distinctively different NaCl concentrations. The results show that the concentration of OH groups on the sorbent surface is a meaningful descriptor for the observed variations in sorption capacity onto different oxides. Compound-specific linear correlations were obtained, enabling the prediction of sorption coefficients. In addition, a more complex sorption behavior of organic cations compared to uncharged molecules were observed as demonstrated by the sorption results at different electrolyte concentrations. Thus, the study provides an important step towards a better principal mechanistic understanding of organic cation sorption. However, further work using other sorbents including natural ones and other probe molecules is needed to verify the identified relationships within the scope of developing reliable prediction models for cation sorption.

Diffusion of organic anions in clay-rich media: Retardation and effect of anion exclusion

The transport of emerging organic contaminants through the geosphere is often an environmental issue. The sorption of organic compounds slows their transport in soils and porous rocks and retardation is often assessed by extrapolation of batch experiments. However, transport experiments are preferable to strengthen migration data and modelling. In this context, we evaluated the adsorption of various organic acids by means of through-diffusion experiments in a sedimentary clay-rich rock (Callovo-Oxfordian, East of Paris Basin, France). A low diffusivity of organic anions was quantified with effective diffusion coefficients, D_e, ranged between 0.5 and 7 10^-12 m² s^-1. These values indicated an organic anion exclusion. As for chloride, the porosity accessible to organic anions was lower than that of water: ε_a(organic anions) < ε(water). The partial exclusion of organic anions from rock porosity was linked to both charge and size effects. A significant retardation was observed for organic anions such as oxalate, citrate or α-isosaccharinate. Yet, retardation measured by diffusion experiments was significantly lower than expected from batch experiments on crushed samples. An empirical correction factor is proposed to account for a possible decrease of retardation with accessible porosity of diffusing solute. This feature has significant implications for the estimation of migration parameters of organic compounds in the environment.

Effect of adjuvant on pendimethalin and dimethenamid-P behaviour in soil

Adjuvants are used to improve pesticides' performance. It is expected that adjuvants should increase sorption and persistence, as well as decrease mobility of pesticides in soils. Impact of the "Grounded" brand adjuvant on the behaviour of two herbicides, pendimethalin and dimethenamid-P, was investigated in a Haplic Chernozem. Both herbicides were tested in a laboratory batch sorption experiment with and without adjuvant. The sorption experiment showed that adjuvant negligibly increased dimethenamid-P sorption (K_F = 2.12 and 2.15 cm^3/n μg^1 - 1/n g^-1) but significantly increased pendimethalin sorption (K_F = 270.1 and 3096.4 cm^3/n μg^1 - 1/n g^-1). In field conditions, both herbicides were retained mainly in the topsoil layer (0-5 cm). The pendimethalin dissipation half-lives were similar for all treatments (ranging from 43.0 to 44.6 days) and were not influenced by either irrigation (p = 0.86) or adjuvant (p = 0.9). The dimethenamid-P dissipation half-lives ranged from 8.8 days for irrigated treatment without adjuvant to 12.9 days for non-irrigated treatment with adjuvant. Dimethenamid-P dissipation half-life in treatments with adjuvant was significantly longer (p = 0.049) than was half-life in a treatment without adjuvant. Significantly longer dissipation half-life was observed also in non-irrigated treatments than in irrigated treatments (p = 0.044).

Monitoring the occurrence of pharmaceuticals in soils irrigated with reclaimed wastewater

The use of reclaimed wastewater for irrigation is foreseen as a possible strategy to mitigate the pressure on water resources in dry regions. However, there is the risk of potential accumulation of contaminants of emerging concern (CECs) in the edaphic environment, their percolation and consequently contamination of aquifers. In the present study, we measured the levels of a wide range of commonly used pharmaceutically active compounds (PhACs) in sewage from a local wastewater treatment plant (WWTP) and in soils irrigated with treated wastewater. Analysis of target compounds showed total concentrations between 73 and 372 μg L^-1 in WWTP influents, and from 3 to 41 μg L^-1 in effluents. The total concentrations of PhACs detected in surface soil samples were in the range of 2 and 15 ng g^-1, with predominance of analgesics and anti-inflammatories (maximum concentration = 10.05 ng g^-1), followed by antibiotics and psychiatric drugs (maximum concentration = 5.45 ng g^-1 and 3.78 ng g^-1, respectively). Both effluent samples and irrigated soils shared similar compositional patterns, with compounds such as hydrochlorothiazide and diclofenac being predominant. Additionally, PhACs were also detected in soil samples at a depth of 150 cm, indicating that these chemical undergo leaching associated with heavy-rain episodes. Their occurrence in soils was affected by temperature too, as maximum concentrations were measured in colder months (up to 14 ng g^-1), indicating higher persistence at lower temperatures. Finally, the ecotoxicological risk of PhACs in soil was evaluated by calculating their risk quotients (RQs). The risk was very low as RQ values ranged between <0.01 and 0.07. However, this initial assessment could be improved by future works on toxicity using specific terrestrial organisms.

Sorption of citalopram, irbesartan and fexofenadine in soils: Estimation of sorption coefficients from soil properties

The sorption of 3 pharmaceuticals, which may exist in 4 different forms depending on the solution pH (irbesartan in cationic, neutral and anionic, fexofenadine in cationic, zwitter-ionic and anionic, and citalopram cationic and neutral), in seven different soils was studied. The measured sorption isotherms were described by Freundlich equations, and the sorption coefficients, K_F (for the fixed n exponent for each compound), were related to the soil properties to derive relationships for estimating the sorption coefficients from the soil properties (i.e., pedotransfer rules). The largest sorption was obtained for citalopram (average K_F value for n = 1 was 1838 cm³ g^-1) followed by fexofenadine (K_F = 35.1 cm^3/n μg^1-1/n g^-1, n = 1.19) and irbesartan (K_F = 3.96 cm^3/n μg^1-1/n g^-1, n = 1.10). The behavior of citalopram (CIT) in soils was different than the behaviors of irbesartan (IRB) and fexofenadine (FEX). Different trends were documented according to the correlation coefficients between the K_F values for different compounds (R_IRB,FEX = 0.895, p-value<0.01; R_IRB,CIT = -0.835, p-value<0.05; R_FEX,CIT = -0.759, p-value<0.05) and by the reverse relationships between the K_F values and soil properties in the pedotransfer functions. While the K_F value for citalopram was positively related to base cation saturation (BCS) or sorption complex saturation (SCS) and negatively correlated to the organic carbon content (Cox), the K_F values of irbesartan and fexofenadine were negatively related to BCS, SCS or the clay content and positively related to Cox. The best estimates were obtained by combining BCS and Cox for citalopram (R² = 93.4), SCS and Cox for irbesartan (R² = 96.3), and clay content and Cox for fexofenadine (R² = 82.9).

Towards the understanding of antibiotic occurrence and transport in groundwater: Findings from the Baix Fluvià alluvial aquifer (NE Catalonia, Spain)

Antibiotics are an increasing focus of interest due to their high detection frequency in the environment. However, their presence in water bodies is not regulated by environmental policies. This field study investigates, for the first time, the occurrence, behavior and fate of a selection of 53 antibiotics, including up to 10 chemical groups, in an alluvial aquifer originated from manure application in an agricultural region using hydrogeological, hydrochemical and isotopic approaches. Up to 11 antibiotics were found in groundwater corresponding to 4 different chemical groups: fluoroquinolones, macrolides, quinolones and sulfonamides. In surface water, only 5 different antibiotics from 2 chemical groups: fluoroquinolones and sulfonamides, were quantified. The most frequent antibiotics were sulfamethoxazole and ciprofloxacin. Concentrations of antibiotics were in the order of ng/L, with maximum concentrations of 300ng/L in groundwater. Hydrochemistry and isotopic data and geostatistics confirmed the spatial trend observed for nitrates, where nitrate concentrations tend to be higher in the margin areas of the study area, and lower concentrations are found nearby the river. On the other hand, no clear continuous spatial concentration trend of antibiotics was observed in the aquifer, supported by the short spatial correlation found in the variograms. This indicates that the physical-chemical properties and processes of each antibiotic (mainly, sorption and degradation), and other environmental issues, such as a patchy diffuse input and the manure antibiotic content itself, play an important role in their spatial distribution in groundwater. A discussion on the estimation of the antibiotic sorption parameter reveals the difficulties of describing such phenomena. Furthermore, retardation factors will extend over several orders of magnitude, which highly affects the movement of individual antibiotics within the aquifer. To summarize, this study points out the difficulties associated with antibiotic research in groundwater in order to define water resources quality management strategies and environmental regulations.

Adsorption of polar organic molecules on sediments: Case-study on Callovian-Oxfordian claystone

The release and transport of anthropogenic organic matter through the geosphere is often an environmental criterion of safety. Sedimentary rocks are widely studied in this context as geological barriers for waste management. It is the case of Callovian-Oxfordian claystone (COx), for which several studies report adsorption of anthropogenic organic molecules. In this study, we evaluated and reviewed adsorption data of polar organic molecules on COx claystone. Experiments were performed on raw claystone, decarbonated and clay fractions. Adsorption isotherms were measured with adsorbates of various polarities: adipate, benzoate, ortho-phthalate, succinate, gluconate, oxalate, EDTA, citrate. A significant adsorption was observed for multidentate polycarboxylic acids as evidenced with phthalate, succinate, oxalate, gluconate, EDTA and citrate (R_d = 1.53, 3.52, 8.4, 8.8, 12.4, 54.7 L kg^-1 respectively). Multiple linear regression were performed as a statistical analysis to determine the predictors from these adsorption data. A linear correlation between adsorption data (R_d) and dipole moment (μ) of adsorbates was evidenced (R² = 0.91). Molecules with a high dipole moment, μ(D) > 2.5, displayed a significant adsorption, R_d≫1 L kg^-1. A qualitative correlation can be easily estimated using the water/octanol partition coefficient, P_ow, of adsorbates (R² = 0.77). In this case, two opposite trends were distinguished for polar and apolar molecules. The use of organic carbon content in sediments is relevant for predicting adsorption of apolar compounds, log (P_ow)>+1. The oxides/clays contents may be relevant regarding polar molecules, log (^apparentP_ow)<-1. The proposed scheme offers a general methodology for investigation of geo-barriers towards heterogeneous organic plumes.

Transport behavior of the pharmaceutical compounds carbamazepine, sulfamethoxazole, gemfibrozil, ibuprofen, and naproxen, and the lifestyle drug caffeine, in saturated laboratory columns

Despite the large number of pharmaceutically active compounds found in natural environments little is known about their transport behavior in groundwater, which is complicated by their wide range of physical and chemical properties. The transport behavior of five widely used and often detected pharmaceutical compounds and one lifestyle drug has therefore been investigated, using a set of three column experiments. The investigated compounds were the anticonvulsant carbamazepine, the lifestyle drug caffeine, the antibiotic sulfamethoxazole, the lipid regulator gemfibrozil, and the nonsteroidal anti-inflammatories ibuprofen and naproxen. The columns were filled with three different types of sand. The substrates consisted of artificially prepared iron-coated sand, artificially prepared organic carbon sand (with 5% leaf compost), and natural aquifer sand from Long Point, Ontario (Canada). The experiments were conducted simultaneously under the same hydraulic conditions and with the same input solution of about 1μg·L^-1 of each compound. The transport behavior of the organic compounds differed significantly between both the different columns and the different compounds. A strong correlation was observed between the retardation factors for carbamazepine, gemfibrozil, and ibuprofen and the organic carbon content of the substrate. While the retardation increased with increasing organic carbon content, no direct relationship was observed between the organic carbon content and the removal of these compounds. In contrast, the retardation factors for sulfamethoxazole and naproxen showed no correlation with the organic carbon content but these compounds were significantly removed in the presence of organic matter. The influence of the Fe³⁺ surfaces in the iron-coated sand was less significant than expected, with all compounds except for sulfamethoxazole having retardation factors <1.8. Caffeine was so strongly removed during transport through those substrates containing organic carbon that no reliable retardation factor could be determined.

Quantification of pH-dependent speciation of organic compounds with spectroscopy and chemometrics

Fluorescence and UV/Vis spectra of aqueous solutions with numerous organic compounds are a superposition of single spectra of the chemical species present. Thus, an isolation of individual spectra with chemometrics is required for their quantification. We investigated UV/Vis spectra and fluorescence excitation-emission matrices of vanillic acid, salicylic acid, phenoxyacetic acid and phthalic acid with positive matrix factorization (PMF) and non-negativity constrained parallel factor analysis (PARAFAC) in combination with the law of mass action. In consideration of the pH-dependent speciation of organic acids, we first reconstructed the pH-specific spectra of each compound. Using these spectra as known components in a constrained algorithm, we could successfully quantify species of multiple compounds and reconstruct the solution pH. In addition, we estimated the uncertainty of reconstructed spectra and concentrations in order to assess the most probable number of components for PMF/PARAFAC. Therefore, we could derive a framework to reconstruct the number of relevant species and their individual concentration present in spectroscopic data of aqueous solutions containing multiple organic compounds.

Simultaneous sorption of four ionizable pharmaceuticals in different horizons of three soil types

Soils may be contaminated by human or veterinary pharmaceuticals. Their behaviour in soil environment is largely controlled by sorption of different compounds in a soil solution onto soil constituents. Here we studied the sorption affinities of 4 pharmaceuticals (atenolol, trimethoprim, carbamazepine and sulfamethoxazole) applied in solute mixtures to soils taken from different horizons of 3 soil types (Greyic Phaeozem on loess, Haplic Luvisol on loess and Haplic Cambisol on gneiss). In the case of the carbamazepine (neutral form) and sulfamethoxazole (partly negatively charged and neutral), sorption affinity of compounds decreased with soil depth, i.e. decreased with soil organic matter content. On the other hand, in the case of atenolol (positively charged) and trimethoprim (partly positively charged and neutral) compound sorption affinity was not depth dependent. Compound sorption affinities in the four-solute systems were compared with those experimentally assessed in topsoils, and were estimated using the pedotransfer rules proposed in our previous study for single-solute systems. While sorption affinities of trimethoprim and carbamazepine in topsoils decreased slightly, sorption affinity of sulfamethoxazole increased. Decreases in sorption of the two compounds could be attributed to their competition between each other and competition with atenolol. Differences between carbamazepine and atenolol behaviour in the one- and four-solute systems could also be explained by the slightly different soil properties in this and our previous study. A great increase of sulfamethoxazole sorption in the Greyic Phaeozem and Haplic Luvisol was observed, which was attributed to elimination of repulsion between negatively charged molecules and particle surfaces due to cation sorption (atenolol and trimethoprim) on soil particles. Thus, our results proved not only an antagonistic but also a synergic affect of differently charged organic molecules on their sorption to soil constituents.

Uptake, translocation and possible biodegradation of the antidiabetic agent metformin by hydroponically grown Typha latifolia

The increasing load of pharmaceutical compounds has raised concerns about their potential residues in aquatic environments and ecotoxicity. Metformin (MET), a widely prescribed antidiabetic II medicine, has been detected in high concentration in sewage and in wastewater treatment effluents. An uptake and translocation study was carried out to assess the ultimate fate of MET in phytoremediation. MET was removed from media by Typha latifolia, and the removal processes followed first order kinetics. After 28 days, the removal efficiencies were in a range of 74.0±4.1-81.1±3.3%. In roots, MET concentration was increasing during the first two weeks of the experiment but thereafter decreasing. In contrast, MET concentration was continuously increasing in rhizomes and leaves. Bioaccumulation of MET in roots was much higher than in leaves and rhizomes. As degradation product of metformin in the plant, methylbiguanide (MBG) was detected whereas guanylurea was undetectable. Moreover, MBG concentration in roots was increasing with exposure time. An enzymatic degradation experiment showed the degradation rate followed the order of MET<MBG<<guanylurea. This may explain the low concentration of MBG in plant. The findings of this study contribute to understand and evaluate the potential for phytoremediation of such kind of contaminants.

An analysis of the dissipation of pharmaceuticals under thirteen different soil conditions

The presence of human and veterinary pharmaceuticals in the environment is recognized as a potential threat. Pharmaceuticals have the potential to contaminate soils and consequently surface and groundwater. Knowledge of contaminant behavior (e.g., sorption onto soil particles and degradation) is essential when assessing contaminant migration in the soil and groundwater environment. We evaluated the dissipation half-lives of 7 pharmaceuticals in 13 soils. The data were evaluated relative to the soil properties and the Freundlich sorption coefficients reported in our previous study. Of the tested pharmaceuticals, carbamazepine had the greatest persistence (which was mostly stable), followed by clarithromycin, trimethoprim, metoprolol, clindamycin, sulfamethoxazole and atenolol. Pharmaceutical persistence in soils was mostly dependent on the soil-type conditions. In general, lower average dissipation half-lives and variability (i.e., trimethoprim, sulfamethoxazole, clindamycin, metoprolol and atenolol) were found in soils of better quality (well-developed structure, high nutrition content etc.), and thus, probably better microbial conditions (i.e., Chernozems), than in lower quality soil (Cambisols). The impact of the compound sorption affinity onto soil particles on their dissipation rate was mostly negligible. Although there was a positive correlation between compound dissipation half-life and Freundlich sorption coefficient for clindamycin (R=0.604, p<0.05) and sulfamethoxazole (R=0.822, p<0.01), the half-life of sulfamethoxazole also decreased under better soil-type conditions. Based on the calculated dissipation and sorption data, carbamazepine would be expected to have the greatest potential to migrate in the soil water environment, followed by sulfamethoxazole, trimethoprim and metoprolol. The transport of clindamycin, clarithromycin and atenolol through the vadose zone seems less probable.

Phytotoxicity of wastewater-born micropollutants--Characterisation of three antimycotics and a cationic surfactant

Sewage sludge applied to soil may be a valuable fertiliser but can also introduce poorly degradable and highly adsorptive wastewater-born residues of pharmaceuticals and personal care products (PPCPs) to the soil, posing a potential risk to the receiving environment. Three azole antimycotics (climbazole, ketoconazole and fluconazole), and one quaternary ammonium compound (benzyldimethyldodecylammonium chloride, BDDA) that are frequently detected in municipal sewage sludge and/or treated wastewater were therefore characterised in their toxicity toward terrestrial (Brassica napus) and aquatic (Lemna minor) plants. Fluconazole and climbazole showed the greatest toxicity to B. napus, while toxicity of ketoconazole and BDDA was by one to two orders of magnitude lower. Sludge amendment to soil at an agriculturally realistic rate of 5 t/ha significantly reduced the bioconcentration of BDDA in B. napus shoots compared to tests without sludge amendment, although not significantly reducing phytotoxicity. Ketoconazole, fluconazole and BDDA proved to be very toxic to L. minor with median effective concentrations ranging from 55.7 μg/L to 969 μg/L. In aquatic as well as terrestrial plants, the investigated azoles exhibited growth-retarding symptoms presumably related to an interference with phytohormone synthesis as known for structurally similar fungicides used in agriculture. While all four substances exhibited considerable phytotoxicity, the effective concentrations were at least one order of magnitude higher than concentrations measured in sewage sludge and effluent. Based on preliminary hazard quotients, BDDA and climbazole appeared to be of greater environmental concern than the two pharmaceuticals fluconazole and ketoconazole.