A Framework to Predict Uptake of Trace Organic Compounds by Plants

Uptake, accumulation and toxicity of short chain chlorinated paraffins to wheat (Triticum aestivum L.)

Short chain chlorinated paraffins (SCCPs) are ubiquitous persistent organic pollutants. They have been widely detected in plant-based foods and might cause adverse impacts on humans. Nevertheless, uptake and accumulation mechanisms of SCCPs in plants remain unclear. In this study, the soil culture data indicated that SCCPs were strongly absorbed by roots (root concentration factor, RCF>1) yet limited translocated to shoots (translocation factor<1). The uptake mechanism was explored by hydroponic exposure, showing that hydrophobicity and molecular size influenced the root uptake and translocation of SCCPs. RCFs were significantly correlated with logKow values and molecular weights in a parabolic curve relationship. Besides, it was extremely difficult for SCCPs to translocate from shoots back to roots via phloem. An active energy-dependent process was proposed to be involved in the root uptake of SCCPs, which was supported by the uptake inhibition by the low temperature and metabolic inhibitor. Though SCCPs at environmentally relevant concentrations had no negative impacts on root morphology and chlorophyll contents, it caused obvious changes in cellular ultrastructure of root tip cells and induced a significant increase in superoxide dismutase activity. This information may be beneficial to moderate crop contamination by SCCPs, and to remedy soils polluted by SCCPs with plants.

Uptake of Pharmaceuticals by Crops: A Systematic Review and Meta-analysis

Studies on the uptake of pharmaceuticals from soils into crops were first conducted in the 2000s. Since then a wealth of such data has been generated, but to the best of our knowledge, these studies have not been systematically reviewed. We present a quantitative, systematic review of empirical data on the uptake of pharmaceuticals into crops. We developed a custom-made relational database on plant uptake of pharmaceuticals that contained details of the experimental design and associated results from 150 articles, spanning 173 pharmaceuticals, 78 study crops, and 8048 unique measurements. Analysis of the data in the database showed clear trends in experimental design, with lettuce being the most studied crop and carbamazepine and sulfamethoxazole being the most studied pharmaceuticals. Pharmaceutical properties were found to create the greatest range in uptake concentrations of any single variable studied. Uptake concentrations were also found to vary between crops, with relatively high uptake concentrations identified in cress, lettuce, rice, and courgette crops. An understanding of the influence of soil properties on pharmaceutical uptake was limited by a lack of information on key soil properties across the published literature. The data comparisons were inhibited by differences in quality of the different studies. Moving forward, a framework for best practice in this field is needed to maximize the value and further applications of the data produced. Environ Toxicol Chem 2023;42:2091-2104. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Uptake, translocation and metabolism of acetamiprid and cyromazine by cowpea (Vigna unguiculata L.)

Acetamiprid (ACE) and cyromazine (CYR) are the two pesticides that are used relatively frequently and in large quantities in cowpea growing areas in Hainan. The uptake, translocation and metabolic patterns and subcellular distribution of these two pesticides in cowpea are important factors affecting pesticide residues in cowpea and assessing the dietary safety of cowpea. In this study, we investigated the uptake, translocation, subcellular distribution, and metabolic pathway of ACE and CYR in cowpea under laboratory hydroponic conditions. The distribution trends of both ACE and CYR in cowpea plants were leaves > stems > roots. The distribution of both pesticides in subcellular tissues of cowpea was cell soluble fraction > cell wall > cell organelle, and both transport modes were passive. A multiplicity of metabolic reactions of both pesticides occurred in cowpea, including dealkylation, hydroxylation and methylation. The results of the dietary risk assessment indicate that ACE is safe for use in cowpeas, but CYR poses an acute dietary risk to infants and young children. This study provided a basis for insights into the transport and distribution of ACE and CYR in vegetables and contributes to the assessment of whether pesticide residues in vegetables could pose a potential threat to human health at high concentrations of pesticides in the environment.

Uptake, Translocation, and Distribution of Cyantraniliprole in a Wheat Planting System

Cyantraniliprole uptake, translocation, and distribution in wheat plants grown in hydroponics and soil conditions were investigated. The hydroponics experiment indicated that cyantraniliprole was prone to be absorbed by wheat roots mainly through the apoplastic pathway and predominately distributed in the cell-soluble fraction (81.4-83.6%) and ultimately transferred upward to leaves (TF_leave/stem = 4.84 > TF_stem/root = 0.67). In wheat-soil systems, the uptake of cyantraniliprole was similar to that in hydroponics. The accumulation of cyantraniliprole in wheat tissues was mainly affected by the content of soil organic matter and clay, resulting in the increased adsorption of cyantraniliprole onto soils (R² > 0.991, P < 0.01), and was positively related to the concentration of cyantraniliprole in soil pore water (R² > 0.991, P < 0.001). Besides, the absorption of cyantraniliprole by wheat was predicted well by the partition-limited model. These results increased our understanding of the absorption and accumulation of cyantraniliprole in wheat and were also helpful for guiding the practical application and risk evaluation of cyantraniliprole.

Selective accumulation of pharmaceutical residues from 6 different soils by plants: a comparative study on onion, radish, and spinach

The accumulation of six pharmaceuticals of different therapeutic uses has been thoroughly investigated and compared between onion, spinach, and radish plants grown in six soil types. While neutral molecules (e.g., carbamazepine (CAR) and some of its metabolites) were efficiently accumulated and easily translocated to the plant leaves (onion > radish > spinach), the same for ionic (both anionic and cationic) molecules seems to be minor to moderate. The maximum accumulation of CAR crosses 38,000 (onion), 42,000 (radish), and 7000 (spinach) ng g-1 (dry weight) respectively, in which the most majority of them happened within the plant leaves. Among the metabolites, the accumulation of carbamazepine 10,11-epoxide (EPC - a primary CAR metabolite) was approximately 19,000 (onion), 7000 (radish), and 6000 (spinach) ng g-1 (dry weight) respectively. This trend was considerably similar even when all these pharmaceuticals applied together. The accumulation of most other molecules (e.g., citalopram, clindamycin, clindamycin sulfoxide, fexofenadine, irbesartan, and sulfamethoxazole) was restricted to plant roots, except for certain cases (e.g., clindamycin and clindamycin sulfoxide in onion leaves). Our results clearly demonstrated the potential role of this accumulation process on the entrance of pharmaceuticals/metabolites into the food chain, which eventually becomes a threat to associated living biota.

Uptake of different pharmaceuticals in soil and mycorrhizal artichokes from wastewater

The irrigation with treated wastewater is among the main anthropogenic sources for the release of pharmaceuticals (PhACs) into the soils and their translocation into crops, with possible toxic and adverse effects on humans. The arbuscular mycorrhizal fungi (AMF) can be employed for the reduction of organic soil pollutants, even if their efficiency depends on the mycorrhizal fungi, the plant colonized, and the type and concentration of the contaminant. This study aimed to evaluate the uptake of PhACs from wastewaters of different qualities used for the irrigation of mycorrhizal artichoke plants, the presence in their edible parts and the role of the arbuscular mycorrhizal fungi. The research was carried out on artichoke plants not inoculated and inoculated with two different AMF and irrigated with treated wastewater (TW), groundwater (GW) or GW spiked with different and selected PhACs (SGW). The inocula were a crude inoculum of Septoglomus viscosum (MSE) and a commercial inoculum of Glomus intraradices and Glomus mosseae (MSY). The results of the present study showed that carbamazepine and fluconazole were found in the artichoke only with SGW irrigation. The mycorrhizal plants showed a reduction of the pharmaceutical's uptake, and within the AMF, MSE was more effective in preventing their absorption and translocation.

Case study on antiretroviral drugs uptake from soil irrigated with contaminated water: Bio-accumulation and bio-translocation to roots, stem, leaves, and fruits

This study aimed to evaluate the potential of uptake of the commonly used antiretroviral drugs (ARVDs) in South Africa (abacavir, nevirapine, and efavirenz) by vegetable plants (beetroot, spinach, and tomato) from contaminated soil culture. The study results showed that all the studied vegetables have the potential to take up abacavir, nevirapine, and efavirenz from contaminated soil, be absorbed by the root, and translocate them to the aerial part of the plants. The total percentage of ARVDs found in the individual plant was mainly attributed to abacavir which contributed 53% in beetroot and 48% in spinach, while efavirenz (42%) was the main contributor in tomato. Abacavir was found at high concentrations to a maximum of 40.21 μg/kg in the spinach root, 18.43 μg/kg in the spinach stem, and 6.77 μg/kg in the spinach soil, while efavirenz was the highest concentrations, up to 35.44 μg/kg in tomato leaves and 8.86 μg/kg in tomato fruits. Spinach roots accumulated more ARVDs than beetroot and tomato however, the concentrations were not statistically different. Hydrophobicity was the main effect on the linearity, accumulation, and translocation of ARVDs. This study advances knowledge on the fate of ARVDs in agroecosystems, particularly in plant root - ARVD interaction and the resulting potentially toxic effects on plants. These results suggest that the quality of water used for crop irrigation needs to be assessed prior to irrigation to avoid vegetable plant pollution as contaminated water results in the contaminants uptake by plants. This may lead to the transfer of pollutants to the edible crops parts of and thus be unintentionally consumed by humans. More studies need to be continuously conducted to evaluate ARVDs bioaccumulation and their mechanism of uptake by other vegetables. The use of the pot-plant system can be recommended because it closely relates to the agricultural world.

Uptake kinetics and subcellular distribution of three classes of typical pesticides in rice plants

Food safety problems caused by pesticide residues have always been a concern for many people. In this study, we investigated the uptake, translocation and subcellular distribution of neonicotinoid insecticides, triazole fungicides, and sulfonylurea herbicides in rice plants (Oryza sativa L.). The time-dependent uptake kinetics of the three categories of pesticides with different molecular structures fit a first-order one-compartment kinetic model. The neonicotinoids (log K_ow -0.66-0.8) were mainly concentrated in the leaves, and the triazoles (log K_ow 3.72-4.4) were mainly concentrated in the roots. Neonicotinoid pesticides in the roots were preferentially transported across the membrane through the symplastic pathway; triazole pesticides except for triadimefon and myclobutanil preferentially passed through the symplastic pathway; and sulfonylurea pesticides (log K_ow 0.034-2.89) were first transported upward through the apoplastic pathway. In the roots, neonicotinoids, triazoles, and sulfonylurea herbicides were mainly concentrated in the soluble fractions, cell wall and apoplast fractions, respectively. In addition, there was a high positive correlation between the subcellular distribution of pesticides in the roots, stems and leaves. Molecular weight and log K_ow jointly affected the enrichment of triazole pesticides in the roots, stems and leaves and the transfer from stems to leaves, while water solubility and log K_ow commonly affected neonicotinoids. There was a correlation between pesticide absorption and the molecular structures of pesticides. To develop pesticides with strong uptake and transport capabilities, it is necessary to consider that the electronegativity of some atoms is stronger, the sum of the topological indices of heteroatoms can be large, and the van der Waals volume increases accordingly.

Insight into the uptake and translocation of per- and polyfluoroalkyl substances in hydroponically grown lettuce

The prevalence of per- and polyfluoroalkyl substances (PFASs) in agricultural soils has raised concerns regarding the health risks associated with the consumption of PFAS-contaminated agricultural products. The present study investigated the uptake and translocation of nine PFASs in lettuce using a hydroponic setting. During the uptake experiments, long-chain PFASs (≥ C8) exhibited greater accumulations in lettuce roots, while short-chain PFASs (≤ C7) manifested preferential transport to the shoots. The average root concentration factors of PFASs were positively correlated with their log Kow values. A significantly negative relationship was found between the average translocation factors of PFASs and their molecular volume. Sorption of long-chain PFASs by lettuce roots was enhanced after heating the roots to increase the cell membrane permeability. The accumulation of perfluorododecanoic acid increased significantly in shoots of lettuce plants without roots as compared to whole lettuce plants. Results of the present study indicate that sorption to root surface tissues and efficiency in passing through the root Casparian strip are two important factors that affect the uptake and distribution of PFASs within plants.

Insight into the uptake and metabolism of a new insecticide cyetpyrafen in plants

As new agrochemicals are continuously introduced into agricultural systems, it is essential to investigate their uptake and metabolism by plants to better evaluate their fate and accumulation in crops and the subsequent risks to human exposure. In this study, the uptake and elimination kinetics and transformation of a novel insecticide, cyetpyrafen, in two model crops (lettuce and rice) were first evaluated by hydroponic experiments. Cyetpyrafen was rapidly taken up by plant roots and reached a steady state within 24 h, and it was preferentially accumulated in root parts with root concentration factors up to 2670 mL/g. An uptake mechanism study suggested that root uptake of cyetpyrafen was likely to be dominated by passive diffusion and was difficult to transport via xylem and phloem. Ten phase I and three phase II metabolites of cyetpyrafen were tentatively identified in the hydroponic-plant system through a nontarget screening strategy. The structures of two main metabolites (M-309 and M-391) were confirmed by synthesized standards. The metabolic pathways were proposed including hydroxylation, hydrolysis, dehydrogenation, dehydration and conjugation, which were assumed to be regulated by cytochrome P450, carboxylesterase, glycosyltransferase, glutathione S-transferases and peroxidase. Cyetpyrafen and its main metabolites (M-409, M-309 and M-391) were estimated to be harmful/toxic toward nontarget organisms by theoretical calculation. The high bioaccumulation and extensive transformation of cyetpyrafen highlighted the necessity for systematically assessing the crop uptake and metabolism of new agrochemicals.

Uptake, Accumulation, and translocation of azoxystrobin by Vegetable plants in soils: influence of soil characteristics and plant species

Although azoxystrobin has been widely applied on various crops, little is known about the bioavailability of azoxystrobin in the soil-vegetable system. In this study, the uptake, accumulation and translocation of azoxystrobin as affected by soil characteristics and plant species were respectively investigated. The accumulation amount of azoxystrobin in pakchoi increased as soil adsorption decreased and was positively associated with its concentration in pore water (C_pw), which was mainly affected by soil organic matter content. Therefore, C_pw could be a candidate for the estimation of azoxystrobin accumulation in pakchoi. In all the tested vegetables, azoxystrobin was mainly accumulated in roots, and its upward translocation was limited. Root lipid content was a major factor affecting the uptake and translocation of azoxystrobin in different vegetables.

Uptake and transport of steroid estrogens in soil-plant systems and their dissipation in rhizosphere: Influence factors and mechanisms

Residual steroid estrogens (SEs) in soil may be absorbed by plants, and subsequently threaten human health via food chains. However, the environmental behavior of SEs in soil-plant systems remains unclear. In this study, a wheat pot experiment using rhizosphere bags was performed to investigate the uptake and dissipation of target SEs (17 beta-estradiol (E2) and estrone (E1)) in different soils. The results indicated that soils with higher organic matter and silt and clay reduced the plant uptake of estrogens. Compared with E1, E2 was less accumulated in plants, which was mainly correlated with its higher hydrophobicity and shorter half-life. Estrogens tended to concentrate in the plant roots instead of translocating to the shoots. In addition, plant cultivation enhanced estrogen dissipation in the rhizosphere with an improvement of 10-21%. This improvement mainly resulted from stimulating the activities of estrogen-degrading enzymes, increasing the total bacterial populations, and promoting the development of estrogen degraders. Furthermore, this promotion effect will increase with plant growth. These findings will help us understand the characteristics of SEs taken up by plants and the role of the rhizosphere in SEs elimination, and provide theoretical insights into reducing the pollution risk of SEs in agricultural soils.

Removal of tramadol from water using Typha angustifolia and Hordeum vulgare as biological models: Possible interaction with other pollutants in short-term uptake experiments

Tramadol (TRD) is widely detected in aquatic ecosystems as a result of massive abuse and insufficient removal from wastewater facilities. As a result, TRD can contaminate groundwater sources and/or agricultural soils. While TRD toxicity has been reported from aquatic biota, data about TRD detection in plants are scarce. Moreover, information regarding plant capability for TRD removal is lacking. To understand the fate of this opioid, we have investigated the uptake, translocation and removal capacity of TRD by plants, addressing short-term and long-term uptake. The uptake rates of TRD, in excised barley and cattail roots, were 5.18 and 5.79 μg g^-1 root fresh weight day^-1, respectively. However, TRD uptake was strongly inhibited after co-exposing these roots either with the drug venlafaxine (similar molecular structure as TRD) or with quinidine (an inhibitor of cellular organic cation transporters). When barley seedlings were exposed to TRD in a hydroponic experiment a removal efficiency up to 90% (within 15 days) was obtained, with bioconcentration and translocation factors close to 9 and 1, respectively. The combination of results from both plants and the inhibition observed after treatment with quinidine revealed that organic cation transporters may be involved in the uptake of TRD by plants.

Uptake and translocation of triadimefon by wheat (Triticum aestivum L.) grown in hydroponics and soil conditions

Residual pesticides in soil may be taken in by plants and thus have a risk for plant growth and food safety. In this study, uptake of triadimefon and its subsequent translocation and accumulation were investigated with wheat as model plants. The results from hydroponics indicated that triadimefon was absorbed by wheat roots mainly through apoplastic pathway and predominantly distributed into the water soluble fractions (66.7-76.0%). After being uptaken by roots, triadimefon was easily translocated upward to wheat shoots and leaves. Interestingly, triadimefon in leaves was mainly distributed in the soluble fraction by 52.5% at the beginning, and gradually transferred into the cell wall by 47.2% at equilibrium. The uptake of triadimefon from soils by wheat plants was similar to that in hydroponics. Its accumulation were mainly governed by adsorption of the fungicide onto soils, and positively correlated with its concentration in in situ pore water (C_IPW). Thus, C_IPW can be suitable for predicting the uptake of triadimefon by wheat from soils. Accordingly, uptake of triadimefon by wheat was predicted well by using the partition-limited model. Our study provides valuable information for guiding the practical application and safety evaluation of triadimefon.

Phytoextraction of ciprofloxacin and sulfamethoxaxole by cattail and switchgrass

Cattail (Typha latifolia L.) and switchgrass (Panicum virgatum L.) can effectively remove inorganic contaminants from soils and biosolids, but their role in the attenuation of organic contaminants, such as antimicrobials, is currently poorly understood. Uptake by plants is one of several mechanisms by which plant-assisted attenuation of antimicrobials can be achieved. The objectives of this growth room study were to evaluate the plant uptake of ciprofloxacin (CIP) and sulfamethoxazole (SMX) and examine their partitioning between plant roots and aboveground biomass (AGB). Plant uptake of the two ¹⁴C labeled antimicrobials was studied at two environmentally relevant concentrations (5 and 10 μg L^-1). Plants were destructively sampled every 3-4 d during the 21-d growth period. Accumulation of CIP and SMX in both plant species was greater in the roots than in the AGB. The percentage uptake values of the two antimicrobials were significantly greater for cattail (34% for CIP, 20% for SMX) than for switchgrass (10% for both CIP and SMX). Translocation factors of the two antimicrobials were <1 for both plants, indicating slow movement of the antimicrobials from the roots to the shoots. For cattail roots, the BCF for CIP (1.58 L g^-1) was significantly greater than that for SMX (0.8 L g^-1). By comparison, BCFs for switchgrass roots did not differ significantly between CIP (0.88 L g^-1) and SMX (1.13 L g^-1). These results indicate greater potential for cattail to phytoextract CIP and SMX and significantly contribute to the attenuation of these antimicrobials in systems designed for the phytoremediation of contaminated wastewater.

Uptake, accumulation and impact of antiretroviral and antiviral pharmaceutical compounds in lettuce

While the contamination of agroecosystems with pharmaceutical compounds has been reported, the fate of these compounds, particularly uptake into plants remains unclear. This lack of environmental fate data is evident for a critical class of pharmaceuticals, the antivirals and antiretrovirals (ARVDs). Thus, this study evaluated the root uptake of the antiretroviral compounds nevirapine, lamivudine and efavirenz, and the antiviral compound oseltamivir in lettuce. The lettuce was hydroponically grown in a nutrient solution containing the four ARVD pharmaceutical mixture in the 1-100 μg L-1 concentration range. The measured bioaccumulation showed that efavirenz and lamivudine accumulated to the highest and lowest degree, at concentrations of 3463 ng g-1 and 691 ng g-1 respectively. The translocation factor between the root and leaf for nevirapine was greater than 1. The highest concentration of the pharmaceutical mixture had a physiological impact on the lettuce. Potential toxicity was evidenced by a statistically significant 34% (p = 0.04) mean reduction in root and leaf biomass in the 100 μg L-1 ARVD mix exposed lettuce, compared with the controls. This study advances knowledge of the fate of ARVDs in agroecosystems, in particular, plant root - ARVD interaction and the resulting potentially toxic effects on plants.

Uptake kinetics and accumulation of pesticides in wheat (Triticum aestivum L.): Impact of chemical and plant properties

Plant uptake is an important process in determining the transfer of pesticides through a food chain. Understanding how crops take up and translocate pesticides is critical in developing powerful models to predict pesticide accumulation in agricultural produce and potential human exposure. Herein, wheat was selected as a model plant species to investigate the uptake and distribution of eleven widely used pesticides in a hydroponic system as a function of time for 144 h. The time-dependent uptake kinetics of these pesticides were fitted with a first-order 1-compartment kinetic model. During 144 h, flusilazole and difenoconazole, with relative high log K_ow (3.87 and 4.36, respectively), displayed higher root uptake rate constants (k). To clarify the role of root lipid content (f_lip) in plant accumulation of pesticides, we conducted a lipid normalization meta-analysis using data from this and previous studies, and found that the f_lip value was an important factor in predicting the root concentration factor (RCF) of pesticides. An improved correlation was observed between log RCF and log f_lipK_ow (R² = 0.748, N = 26, P < 0.001), compared with the correlation between log RCF and log K_ow (R² = 0.686, N = 26, P < 0.001). Furthermore, the hydrophilic pesticides (e.g. log K_ow < 2) were found to reach partition equilibrium faster than lipophilic pesticides (e.g. log K_ow > 3) during the uptake process. The quasi-equilibrium factor (α_pt) was inversely related to log K_ow (R² = 0.773, N = 11, P < 0.001) suggesting a hydrophobicity-regulated uptake equilibrium. Findings from this study could facilitate crop-uptake model optimization.

On the Use of Mechanistic Soil-Plant Uptake Models: A Comprehensive Experimental and Numerical Analysis on the Translocation of Carbamazepine in Green Pea Plants

Food contamination is a major worldwide risk for human health. Dynamic plant uptake of pollutants from contaminated environments is the preferred pathway into the human and animal food chain. Mechanistic models represent a fundamental tool for risk assessment and the development of mitigation strategies. However, difficulty in obtaining comprehensive observations in the soil-plant continuum hinders their calibration, undermining their generalizability and raising doubts about their widespread applicability. To address these issues, a Bayesian probabilistic framework is used, for the first time, to calibrate and assess the predictive uncertainty of a mechanistic soil-plant model against comprehensive observations from an experiment on the translocation of carbamazepine in green pea plants. Results demonstrate that the model can reproduce the dynamics of water flow and solute reactive transport in the soil-plant domain accurately and with limited uncertainty. The role of different physicochemical processes in bioaccumulation of carbamazepine in fruits is investigated through Global Sensitivity Analysis, which shows how soil hydraulic properties and soil solute sorption regulate transpiration streams and bioavailability of carbamazepine. Overall, the analysis demonstrates the usefulness of mechanistic models and proposes a comprehensive numerical framework for their assessment and use.

Ageing effect on conazole fungicide bioaccumulation in arable soils

Widely used conazole fungicides (CFs) belong to the most frequently detected pesticides in Central European arable soils. However, data on their environmental behaviour and bioavailability to soil organisms are surprisingly scarce. In the present laboratory microcosm study prochloraz, tebuconazole, epoxiconazole and flusilazole were applied to 12 different agricultural soils at background levels. Bioaccumulation to earthworm E. andrei and lettuce L. sativa roots and leaves was evaluated in non-aged (biota exposure after addition of pesticides) and aged (exposure started three months later) systems. In contrast with expectations from ageing effect (decrease of bioavailability), bioaccumulation in E. andrei was both reduced and enhanced after ageing depending on soil properties. The reduction of bioaccumulation correlated positively to the percentage of clay but negatively to soil organic matter. The affinity of compost worm E. andrei towards organic matter where hydrophobic pesticide molecules are sorbed is discussed as a possible explanation. An apparent effect of ageing (reduction of bioavailability) was particularly observed in lettuce roots, where bioaccumulation was significantly reduced in time. However, bioaccumulation in leaves changed ambiguously in aged variants among CFs, possibly as a combined result of bioconcentration, dilution by plant growth and metabolism. This study brings first insights into how the bioaccumulation of conazole fungicides is affected by sequestration in agricultural soils. The results indicate that in complex systems, the ageing is not necessarily connected with decrease of bioaccumulation.

Uptake of cephalexin by lettuce, celery, and radish from water

The introduction of pharmaceuticals into agricultural lands from the application of biosolids and animal manure, and irrigation with treated wastewater has led to concern for animal and human health after the ingestion of pharmaceutical-tainted agricultural products. In this study, the uptake and accumulation of cephalexin, a commonly prescribed antibiotic, was compared in three common vegetables (lettuce, celery, and radish) grown in nutrient solution for 144 h. During the uptake experiments, cephalexin concentration in the nutrient solution decreased in the order of radish > celery > lettuce, while the accumulation of cephalexin in vegetable roots followed the rank of lettuce > celery > radish. The accumulation of cephalexin was below the limit of detection in radish roots. No accumulation of cephalexin was observed in the shoots of all three vegetables. The behaviors of cephalexin in vivo were further elucidated using in vitro measurements of cephalexin sorption by vegetable roots and transformation in plant enzyme extracts. The affinity of cephalexin to lettuce > celery > radish roots, and the respective sorption coefficients of 687, 303, and 161 mL g-1, coupled to the transformation of cephalexin in root enzyme extracts with estimated reaction rate constants of 0.020, 0.027 and 0.024 hr-1 for lettuce, celery and radish, could help elucidate the accumulation observed in the in vivo experiments. Overall, sorption by plant roots (affinity) and reaction with plant enzymes could collectively influence the uptake and accumulation of cephalexin in vegetables.

Uptake, translocation and accumulation of the fungicide benzene kresoxim-methyl in Chinese flowering cabbage (Brassica campastris var. parachinensis) and water spinach (Ipomoea aquatica)

Benzene kresoxim-methyl (BKM) is an important methoxyacrylate-based strobilurin fungicide widely used against various phytopathogenic fungi in crops. Uptake, translocation and accumulation of BKM in vegetables remain unknown. This study was designed to investigate uptake, translocation, and accumulation of ¹⁴C-BKM and/or its potential metabolites in Chinese flowering cabbage and water spinach. ¹⁴C-BKM can be gradually taken up to reach a maximum of 44.4% of the applied amount by Chinese flowering cabbage and 34.6% by water spinach at 32 d after application. The ¹⁴CO₂ fractions released from the hydroponic plant system reached 37.8% for cabbage and 45.8% for water spinach, respectively. Concentrations of ¹⁴C in leaves, stems and roots all gradually increased as vegetables growing, with relative 44.9% (cabbage) and 26.8% (water spinach) of translocated from roots to edible leaves. In addition, ¹⁴C in leaves was mainly accumulated in the bottom leaves, which was visualized by quantitative radioautographic imaging. The bioconcentration factor of ¹⁴C ranged from 7.1 to 38.2 mL g^-1 for the cabbage and from 8.6 to 24.6 mL g^-1 for the water spinach. The translocation factor of BKM ranged from 0.10 to 2.04 for the cabbage and 0.10-0.46 for the water spinach throughout the whole cultivation period, indicating that the cabbage is easier to translocate BKM from roots to leaves and stems than water spinach. In addition, the daily human exposure values of BKM in both vegetables were much lower than the limited dose of 0.15 mg day^-1. The results help assess potential accumulation of BMK in vegetables and potential risk.

Uptake and dissipation of metalaxyl-M, fludioxonil, cyantraniliprole and thiamethoxam in greenhouse chrysanthemum

Production of chrysanthemum (Dendranthema grandiflora) in greenhouses often requires intensive pesticide use, which raises serious concerns over food safety and human health. This study investigated uptake, translocation and residue dissipation of typical fungicides (metalaxyl-M and fludioxonil) and insecticides (cyantraniliprole and thiamethoxam) in greenhouse chrysanthemum when applied in soils. Chrysanthemum plants could absorb these pesticides from soils via roots to various degrees, and bioconcentration factors (BCF_LS) were positively correlated with lipophilicity (log K_ow) of pesticides. Highly lipophilic fludioxonil (log K_ow = 4.12) had the greatest BCF_LS (2.96 ± 0.41 g g^-1), whereas hydrophilic thiamethoxam (log K_ow = -0.13) had the lowest (0.09 ± 0.03 g g^-1). Translocation factors (TF) from roots to shoots followed the order of TF_leaf > TF_stem > TF_flower. Metalaxyl-M and cyantraniliprole with medium lipophilicity (log K_ow of 1.71 and 2.02, respectively) and hydrophilic thiamethoxam showed relatively strong translocation potentials with TF values in the range of 0.29-0.81, 0.36-2.74 and 0.30-1.03, respectively. Dissipation kinetics in chrysanthemum flowers followed the first-order with a half-life of 21.7, 5.5, 10.0 or 8.2 days for metalaxyl-M, fludioxonil, cyantraniliprole and thiamethoxam, respectively. Final residues of these four pesticides, including clothianidin (a primary toxic metabolite of thiamethoxam), in all chrysanthemum flower samples were below the maximum residue limit (MRL) values 21 days after two soil applications each at the recommended dose (i.e., 3.2, 2.1, 4.3 and 4.3 kg ha^-1, respectively). However, when doubling the recommended dose, the metabolite clothianidin remained at concentrations greater than the MRL, despite that thiamethoxam concentration was lower than the MRL value. This study provided valuable insights on the uptake and residues of metalaxyl-M, fludioxonil, cyantraniliprole and thiamethoxam (including its metabolite clothianidin) in greenhouse chrysanthemum production, and could help better assess food safety risks of chrysanthemum contamination by parent pesticides and their metabolites.

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.

Mechanistic study on uptake and transport of pharmaceuticals in lettuce from water

The dissemination of pharmaceuticals in agroecosystems originating from land application of animal manure/sewage sludge and irrigation with treated wastewater in agricultural production has raised concern about the accumulation of pharmaceuticals in food products. The pathways of pharmaceutical entries via plant roots, transport to upper fractions, and the factors influencing these processes have yet been systematically elucidated, thus impeding the development of effective measures to mitigate pharmaceutical contamination in food crops. In this study, lettuce uptake of thirteen commonly used pharmaceuticals was investigated using a hydroponic experimental setting. Pharmaceutical sorption by lettuce roots was measured in order to evaluate the influence on pharmaceutical transport from roots to shoots. Small-sized pharmaceuticals e.g., caffeine and carbamazepine with molecular weight (MW) <300 g mol-1 and a low affinity to lettuce roots (sorption coefficient Kp < 0.05 L g-1) manifested substantial transport to shoots. Small-sized molecules lamotrigine and trimethoprim had a relatively strong affinity to lettuce roots (Kp > 12.0 L g-1) and demonstrated a reduced transport to shoots. Large-sized pharmaceuticals (e.g. MW >400 g mol-1) including lincomycin, monensin sodium, and tylosin could be excluded from cell membranes, resulting in the predominant accumulation in lettuce roots. Large-sized oxytetracycline existed as zwitterionic species that could slowly enter lettuce roots; however, the relatively strong interaction with lettuce roots limits its transport to shoots. The mass balance analysis revealed that acetaminophen, β-estradiol, carbadox, estrone and triclosan were readily metabolized in lettuce with >90% loss during 144-h exposure period. A scheme was proposed to describe pharmaceutical uptake and transport in plant, which could reasonably elucidate many literature-reported results. Molecular size, reactivity and ionic speciation of pharmaceuticals, as well as plant physiology, collectively determine their uptake, transport and accumulation in plants.

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.

Insight into the distribution of pharmaceuticals in soil-water-plant systems

Pharmaceuticals in agricultural soils originating from irrigation with treated wastewater and land-applied biosolids can enter field crops. However, little is known about the role of pore water in plant uptake of pharmaceuticals from soils. In this study, the fate, uptake and distribution of fifteen commonly used pharmaceuticals in soil-water-radish systems were investigated to examine the relationship between the accumulation and their physicochemical processes in soils. The results indicate that the distribution of pharmaceuticals between soil and pore water, as well as their biodegradation, combined to govern the bioavailability of pharmaceuticals to plant uptake. Fourteen out of 15 pharmaceuticals could enter radish tissues in which the accumulation ranged from 2.1 to 14080 ng/g. Comparison of bioconcentration factors (BCFs) on the basis of pharmaceutical concentration in bulk soil vs. in pore water implies that pharmaceuticals present in soil pore water are the major bioavailable fractions to plant uptake. The pore water-based BCFs exhibited a positive linear relationship with log D_ow for the pharmaceuticals with >90% as neutral species in soil pore water, while such relationship was not observed between bulk soil-based BCFs and log D_ow mainly due to sorption by soil. Other than hydrophobicity, the dissociation of ionizable pharmaceuticals in the soil pore water and (or) root cells may lead to the "ion-trap" effects and thus influence the uptake and translocation process. The large molecular-size pharmaceuticals (e.g., tylosin) manifested a minimum uptake due plausibly to the limited permeability of cell membranes.

Antibiotics in Agroecosystems: Introduction to the Special Section

The presence of antibiotic drug residues, antibiotic resistant bacteria, and antibiotic resistance genes in agroecosystems has become a significant area of research in recent years and is a growing public health concern. While antibiotics are used in both human medicine and agricultural practices, the majority of their use occurs in animal production where historically they have been used for growth promotion, in addition to the prevention and treatment of disease. The widespread use of antibiotics and the application of animal wastes to agricultural lands play major roles in the introduction of antibiotic-related contamination into the environment. Overt toxicity in organisms directly exposed to antibiotics in agroecosystems is typically not a major concern because environmental concentrations are generally lower than therapeutic doses. However, the impacts of introducing antibiotic contaminants into the environment are unknown, and concerns have been raised about the health of humans, animals, and ecosystems. Despite increased research focused on the occurrence and fate of antibiotics and antibiotic resistance over the past decade, standard methods and practices for analyzing environmental samples are limited and future research needs are becoming evident. To highlight and address these issues in detail, this special collection of papers was developed with a framework of five core review papers that address the (i) overall state of science of antibiotics and antibiotic resistance in agroecosystems using a causal model, (ii) chemical analysis of antibiotics found in the environment, (iii) need for background and baseline data for studies of antibiotic resistance in agroecosystems with a decision-making tool to assist in designing research studies, as well as (iv) culture- and (v) molecular-based methods for analyzing antibiotic resistance in the environment. With a focus on the core review papers, this introduction summarizes the current state of science for analyzing antibiotics and antibiotic resistance in agroecosystems, discusses current knowledge gaps, and develops future research priorities. This introduction also contains a glossary of terms used in the core reivew papers of this special section. The purpose of the glossary is to provide a common terminology that clearly characterizes the concepts shared throughout the narratives of each review paper.