Contaminants of emerging concern (CECs) in Zea mays: Uptake, translocation and distribution tissue patterns over the time and its relation with physicochemical properties and plant transpiration rate

Comparative uptake, translocation and metabolism of phenamacril in crops under hydroponic and soil cultivation conditions

Many studies investigate the plant uptake and metabolism of xenobiotics by hydroponic experiments, however, plants grown in different conditions (hydroponic vs. soil) may result in different behaviors. To explore the potential differences, a comparative study on the uptake, translocation and metabolism of the fungicide phenamacril in crops (wheat/rice) under hydroponic and soil cultivation conditions was conducted. During 7-14 days of exposure, the translocation factors (TFs) of phenamacril were greatly overestimated in hydroponic-wheat (3.6-5.2) than those in soil-wheat systems (1.1-2.0), with up to 3.3 times of difference between the two cultivation systems, implying it should be cautious to extrapolate the results obtained from hydroponic to field conditions. M-144 was formed in soil pore water (19.1-29.9 μg/L) in soil-wheat systems but not in the hydroponic solution in hydroponics; M-232 was only formed in wheat shoots (89.7-103.0 μg/kg) under soil cultivation conditions, however, it was detected in hydroponic solution (20.1-21.2 μg/L), wheat roots (146.8-166.0 μg/kg), and shoots (239.2-348.1 μg/kg) under hydroponic conditions. The root concentration factors (RCFs) and TFs of phenamacril in rice were up to 2.4 and 3.6 times higher than that in wheat for 28 days of the hydroponic exposure, respectively. These results highlighted that cultivation conditions and plant species could influence the fate of pesticides in crops, which should be considered to better assess the potential accumulation and transformation of pesticides in crops.

Uptake and translocation of pharmaceutically active compounds by olive tree (Olea europaea L.) irrigated with treated municipal wastewater

Introduction

The use of treated municipal wastewater (TWW) represents a relevant opportunity for irrigation of agricultural crops in semi-arid regions to counter the increasing water scarcity. Pharmaceutically active compounds (PhACs) are often detected in treated wastewater, posing a risk to humans and the environment. PhACs can accumulate in soils and translocate into different plant tissues, reaching, in some cases, edible organs and entering the food chain.

Methods

This study evaluated the uptake and translocation processes of 10 PhACs by olive trees irrigated with TWW, investigating their accumulation in different plant organs. The experiment was conducted in southern Italy, in 2-year-old plants irrigated with three different types of water: freshwater (FW), TWW spiked with 10 PhACs at a concentration of 200 µg L-1 (1× TWW), and at a triple dose (3× TWW), from July to October 2021. The concentration of PhACs in soil and plant organs was assessed, collecting samples of root, stem, shoot, leaf, fruit, and kernel at 0 (T0), 50 (T1), and 107 (T2) days of irrigation. PhACs extraction from soil and plant organs was carried out using the QuEChERS method, and their concentrations were determined by high-resolution mass spectrometry coupled with liquid chromatography.

Results

Results of uptake factors (UF) showed a different behavior between compounds according to their physicochemical properties, highlighting PhACs accumulation and translocation in different plant organs (also edible part) in 1× TWW and 3× TWW compared to FW. Two PhACs, carbamazepine and fluconazole, showed interactions with the soil-plant system, translocating also in the aerial part of the plant, with a translocation factor (TF) greater than 1, which indicates high root-to-leaf translocation.

Discussion

Findings highlight that only few PhACs among the selected compounds can be uptaken by woody plants and accumulated in edible parts at low concentration. No effects of PhACs exposure on plant growth have been detected. Despite the attention to be paid to the few compounds that translocate into edible organs, these results are promising for adapting wastewater irrigation in crops. Increasing knowledge about PhACs behavior in woody plants can be important for developing optimized wastewater irrigation and soil management strategies to reduce PhACs accumulation and translocation in plants.

Uptake, accumulation and metabolism of UV-320 in vegetables and its impact on growth and quality

UV-320 is classified as a Substance of Very High Concern (SVHC) by the European Chemicals Agency and has attracted significant attention due to its presence in the environment. Understanding the uptake, translocation and metabolic patterns of UV-320 in vegetables is essential for assessing their ability to bioaccumulate and potential risks to human health. In this study, we investigated the uptake and translocation of UV-320 in lettuce and radish by hydroponic experiments. The results showed that the root concentration factors (Croot/Csolution, RCF) of lettuce and radish were in the range of 47.9 to 464 mL/g and 194 to 787 mL/g, respectively. The transfer factors (Cshoot/Croot, TF) were observed to be 0.001-0.012 for lettuce and 0.02-0.05 for radish. Additionally, non-targeted screening identified twelve phase I and one phase II metabolites of UV-320 in vegetables, which were confirmed based on their molecular formulas and structures. The metabolic pathways involving oxidation, ketonylation and deamination were proposed in vegetables. Also, we have observed that UV-320 inhibits the growth of vegetables. Meanwhile, we evaluated the health risk of UV-320 in lettuce and radish and found that the consumption of lettuce is relatively safe, while the consumption of radish has a risk of HQ >1 for both adults and children, which should be seriously considered. This study provides valuable insights into the behavior and ecological risks of UV-320 in the environment.

Effects of charged polystyrene microplastics on the bioavailability of dufulin in tomato plant

Microplastics (MPs) and pesticides commonly exist in the environment, yet the interactions between them and their subsequent impacts on plants remain poorly understood. Thus, this study aimed to investigate the impacts of differently charged polystyrene (PS) MPs, including PS-COO-, PS and PS-NH3+ MPs, on the fate of 14C-labelled new antiviral pesticide Dufulin (DFL) in a hydroponic tomato system. The results showed that MPs greatly reduced the growth of tomato plants, with suppression of 18.4-30.2%. Compared to the control group, PS-COO-, PS and PS-NH3+ MPs also reduced the bioaccumulation of DFL in whole tomato plants by 40.3%, 34.5%, and 26.1%, respectively. Furthermore, MPs influenced the translocation of DFL in plant tissues, and the values decreased at the rates of 38.7%, 26.5% and 15.7% for PS-COO-, PS and PS-NH3+, respectively. Interestingly, compared to the control group, PS-COO- exhibited a profound inhibitory effect on DFL concentrations in tomatoes, potentially resulting in a lower dietary risk in the hydroponic tomato system. This may be due to the strong adsorption between PS-COO- and DFL, and PS-COO- may also inhibit the growth of tomato plants. Overall, our study could provide valuable insights into the risk assessment of DFL in the presence of MPs in plant systems.

l-Cysteine and barium titanate co-modified enteromorpha biochar as effective peroxymonosulfate activator for atrazine treatment

In this study, pyrolysis and hydrothermal methods were used for Enteromorpha biochar that was co-modified with l-cysteine and barium titanate (LBCBa). It has great environmental tolerance and can remove 93.0 % of atrazine (ATZ, 10 mg·L-1) within 60 mins of ultrasonic treatment. The enhanced hydrophilicity, electron-donating capability, and piezoelectricity of LBCBa are considered to induce excellent performance. The apparent reaction rate of the LBCBa-2/PMS/ATZ system with ultrasonic was 2.87 times that without ultrasonic. The density functional theory points out that, introducing l-cysteine to carbon edges improves the adsorption of ATZ and peroxymonosulfate (PMS), making PMS easier to activate. This work offered unique insights for fabricating effective catalysts and demonstrated the combination of hydrophilic functional groups and piezoelectricity in improving catalytic performance and stability.

Personal care products in soil-plant and hydroponic systems: Uptake, translocation, and accumulation

Personal care products (PCPs) are organic compounds that are incorporated in several daily life products, such as shampoos, lotions, perfumes, cleaning products, air fresheners, etc. Due to their massive and continuous use and because they are not routinely monitored in the environment, these compounds are considered emerging contaminants. In fact, residues of PCPs are being discharged into the sewage system, reaching wastewater treatment plants (WWTPs), where most of these compounds are not completely degraded, being partially released into the environment via the final effluents and/or accumulating in the sewage sludges. Environmental sustainability is nowadays one of the main pillars of society and the application of circular economy models, promoting the waste valorisation, is increasingly encouraged. Therefore, irrigation with reclaimed wastewater or soil fertilization with sewage sludge/biosolids are interesting solutions. However, these practices raise concerns due to the potential risks associated to the presence of hazardous compounds, including PCPs. When applied to agricultural soils, PCPs present in these matrices can contaminate the soil or be taken up by crops. Crops can therefore become a route of exposure for humans and pose a risk to public health. However, the extent to which PCPs are taken up and bioaccumulated in crops is highly dependent on the physicochemical properties of the compounds, environmental variables, and the plant species. This issue has attracted the attention of scientists in recent years and the number of publications on this topic has rapidly increased, but a systematic review of these studies is lacking. Therefore, the present paper reviews the uptake, accumulation, and translocation of different classes of PCPs (biocides, parabens, synthetic musks, phthalates, UV-filters) following application of sewage sludge or reclaimed water under field and greenhouse conditions, but also in hydroponic systems. The factors influencing the uptake mechanism in plants were also discussed.

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.

Methylation and Demethylation of Emerging Contaminants in Plants

Many contaminants of emerging concern (CECs) have reactive functional groups and may readily undergo biotransformations, such as methylation and demethylation. These transformations have been reported to occur during human metabolism and wastewater treatment, leading to the propagation of CECs. When treated wastewater and biosolids are used in agriculture, CECs and their transformation products (TPs) are introduced into soil-plant systems. However, little is known about whether transformation cycles, such as methylation and demethylation, take place in higher plants and hence affect the fate of CECs in terrestrial ecosystems. In this study, we explored the interconversion between four common CECs (acetaminophen, diazepam, methylparaben, and naproxen) and their methylated or demethylated TPs in Arabidopsis thaliana cells and whole wheat seedlings. The methylation-demethylation cycle occurred in both plant models with demethylation generally taking place at a greater degree than methylation. The transformation rate of demethylation or methylation was dependent on the bond strength of R-CH3, with demethylation of methylparaben or methylation of acetaminophen being more pronounced. Although not explored in this study, these interconversions may exert influences on the behavior and biological activity of CECs, particularly in terrestrial ecosystems. The study findings demonstrated the prevalence of transformation cycles between CECs and their methylated or demethylated TPs in higher plants, contributing to a more complete understanding of risks of CECs in the human-wastewater-soil-plant continuum.

Influence of exposure time, physicochemical properties, and plant transpiration on the uptake dynamics and translocation of pharmaceutical and personal care products in the aquatic macrophyte Typha latifolia

Typha latifolia is widely used as a phytoremediation model plant for organic compounds. However, the dynamic uptake and translocation of pharmaceutical and personal care products (PPCPs) and their relationship with physicochemical properties, such as lipophilicity (LogKow), ionization behavior (pKa), pH-dependent lipophilicity (LogDow), exposure time and transpiration, are scarcely studied. In the current study, hydroponically grown T. latifolia was exposed to carbamazepine, fluoxetine, gemfibrozil, and triclosan at environmentally relevant concentrations (20 μg/L each). Eighteen out of thirty-six plants were exposed to the PPCPs and the other eighteen were untreated. Plants were harvested at 7, 14, 21, 28, 35, and 42 days and separated into root, rhizome, sprouts, stem, and lower, middle, and upper leaf sections. Dry tissue biomass was determined. PPCP tissue concentrations were analyzed by LC-MS/MS. PPCP mass per tissue type was calculated for each individual compound and for the sum of all compounds during each exposure time. Carbamazepine, fluoxetine, and triclosan were detected in all tissues, while gemfibrozil was detected only in roots and rhizomes. In roots, triclosan and gemfibrozil mass surpassed 80% of the PPCP mass, while in leaf carbamazepine and fluoxetine mass represented 90%. Fluoxetine accumulated mainly in the stem and the lower and middle leaf, while carbamazepine accumulated in the upper leaf. The PPCP mass in roots and rhizome was strongly positively correlated with LogDow, while in leaf it was correlated with water transpired and pKa. PPCP uptake and translocation in T. latifolia is a dynamic process determined by the properties of contaminants and plants.

Biochemical and physiological changes in Zea mays L. after exposure to the environmental pharmaceutical pollutant carbamazepine

The presence of pharmaceuticals in the environment is a matter of great concern. They are consistently found in the environment, raising concerns regarding human exposure through dietary intake. In this study, we observed the effect of the application of carbamazepine at 0.1, 1, 10, and 1000 μg per kg of soil contamination levels to assess stress metabolism in Zea mays L. cv. Ronaldinio at the 4th leaf, tasselling, and dent phenological stages. The transfer of carbamazepine to the aboveground and root biomass was assessed, and uptake increased dose-dependently. No direct effect on biomass production was observed, but multiple physiological and chemical changes were observed. Major effects were consistently observed at the 4th leaf phenological stage for all contamination levels, including reduced photosynthetic rate, reduced maximal and potential activity of photosystem II, decreased water potential, decreased carbohydrates (glucose and fructose) and γ-aminobutyric acid in roots, and increased maleic acid and phenylpropanoids (chlorogenic acid and its isomer, 5-O-caffeoylquinic acid) in aboveground biomass. A reduction in net photosynthesis was observed for the older phenological stages, whereas no other relevant and consistent physiological and metabolic changes related to contamination exposure were detected. Our results indicate that Z. mays can overcome the environmental stress caused by the accumulation of carbamazepine with notable metabolic changes at the early phenological stage; however, older plants adapted and only exhibited minor effects in the presence of the contaminant. The potential implications for agricultural practice could be associated with the plant's response to simultaneous stresses due to metabolite changes associated with oxidative stress.

Transport and removal mechanism of benzene by Tradescantia zebrina Bosse and Epipremnum aureum (Linden ex André) G.S. Bunting in air-plant-solution system

Phytoremediation is considered an effective method for indoor air pollution control. The removal rate and mechanism of benzene in air by two plants, Tradescantia zebrina Bosse and Epipremnum aureum (Linden ex André) G. S. Bunting, were investigated through fumigation experiments under the condition of plant hydroponics culturing. Results showed that the plant removal rates increased with increase in benzene concentration in air. When the benzene concentration in air was set at 432.25-1314.75 mg·m^-3, the removal rates of T. zebrina and E. aureum ranged from 23.05 ± 3.07 to 57.42 ± 8.28 mg·kg^-1·h^-1 FW and from 18.82 ± 3.73 to 101.58 ± 21.20 mg·kg^-1·h^-1 FW, respectively. The removal capacity was positively related to the transpiration rate of plants, indicating that gas exchange rate could be a key factor for the evaluation of removal capacity. There existed fast reversible transport of benzene on air-shoot interface and root-solution interface. After shoot exposure to benzene for 1 h, downward transport was the dominant mechanism in the removal of benzene in air by T. zebrina, while in vivo fixation was the dominant mechanism at exposure time of 3 and 8 h. Within 1-8 h of shoot exposure time, in vivo fixation capacity was always the key factor affecting the removal rate of benzene in the air by E. aureum. Contribution ratio of in vivo fixation in the total benzene removal rate increased from 6.29 to 92.29% for T. zebrina and from 73.22 to 98.42% for E. aureum in the experimental conditions. Reactive oxygen species (ROS) burst induced by benzene exposure was responsible for the contribution ratio change of different mechanisms in the total removal rate, which also was verified by the change of activities of antioxidant enzymes (CAT, POD, and SOD). Transpiration rate and antioxidant enzyme activity could be considered parameters to evaluate the plant removal ability to benzene and to screen plants for establishment of plant-microbe combination technology.

Influence of methylation and demethylation on plant uptake of emerging contaminants

Contaminants of emerging concern (CECs) as well as their transformation products (TPs) are often found in treated wastewater and biosolids, raising concerns about their environmental risks. Small changes in chemical structure, such as the addition or loss of a methyl group, as the result of methylation or demethylation reaction, may significantly alter a chemical's physicochemical properties. In this study, we evaluated the difference in accumulation and translocation between four CECs and their respective methylated or demethylated derivatives in plant models. Suspended Arabidopsis thaliana cell culture and wheat seedlings were cultivated in nutrient solutions containing individual compounds at 1 mg/L. The methylated counterparts were generally more hydrophobic and showed comparative or greater accumulation in both plant models. For example, after 1 h incubation, methylparaben was found in A. thaliana cells at levels two orders of magnitude greater than demethylated methylparaben. In contrast, the demethylated counterparts, especially those with the addition of a hydroxyl group after demethylation, showed decreased plant uptake and limited translocation. For example, acetaminophen and demethylated naproxen were not detected in the shoots of wheat seedlings after hydroponic exposure. Results from this study suggest that common transformations such as methylation and demethylation may affect the environmental fate of CECs, and should be considered to obtain a more comprehensive understanding of risks of CECs in the environment.

Uptake and metabolism of 14C-triclosan in celery under hydroponic system

As triclosan is used extensively as an antimicrobial agent, it inevitably enters agroecosystems, when sewage and treated wastewater are applied to agricultural fields. As a result, triclosan can be accumulated into crops and vegetables. Currently, limited information is available on the metabolism of triclosan in vegetables. In this study, the fate of ¹⁴C-triclosan in celery under a hydroponic system was investigated in a 30-day laboratory test. Most (97.7 %) of the ¹⁴C-triclosan accumulated in celery. The bioconcentration factors of triclosan were up to 3140 L kg^-1 at day 30. The concentration of ¹⁴C-triclosan in roots (17.8 mg kg^-1) was 57- and 127-fold higher than that in stems (0.31 mg kg^-1) and leaves (0.14 mg kg^-1), respectively, at day 30, suggesting a higher accumulation of triclosan in celery roots and negligible transport to stems and leaves. Moreover, triclosan, as well as its eight metabolites, was detected and identified in celery tissues and the growth medium using ¹⁴C-labelling and LC-Q-TOF-MS analysis methods. Phase I metabolites in the growth medium were from hydroxylation, dechlorination, nitration, and nitrosylation. Phase II metabolism was the major pathway in celery tissues. Monosaccharide, disaccharide, and sulfate conjugates of triclosan were putatively identified. The results represent an important step toward a better evaluation of the behavior of triclosan in vegetables, with notable implications for environmental and human risk assessments of triclosan.

Uptake, translocation, and metabolism of thiamethoxam in soil by leek plants

Thiamethoxam (TMX) is commonly applied on leek plants by root irrigation. It might be taken up by leek plants and thus has lasting dietary risk. In this study, the uptake, translocation, and metabolism of TMX in leek plants were investigated. The results obtained from both the hydroponic and soil experiments indicated that TMX could be easily translocated upward and accumulated in leek shoots after being absorbed by roots. The total absorbed TMX amount (M_total) in leek plants from the tested soils varied greatly with its adsorption governed by soil characteristics. Interestingly, M_total was closely correlated with the concentration of TMX in in situ pore water, indicating that TMX in in situ pore water could be a useful approach to predict uptake of this chemical by leek plants from various soils. Profoundly, clothianidin (CLO) was detected with concentration of 0.07-1.54 mg/kg in roots and 0.27-4.12 mg/kg in shoots at 14 d, respectively, suggesting that TMX is easily converted into CLO in leek plants. The results showed that TMX used in soil is easily absorbed by leek and accumulated in edible parts accompanying with formation of CLO.

Accurate Removal of Toxic Organic Pollutants from Complex Water Matrices

Characteristic emerging pollutants at low concentration have raised much attention for causing a bottleneck in water remediation, especially in complex water matrices where high concentration of interferents coexist. In the future, tailored treatment methods are therefore of increasing significance for accurate removal of target pollutants in different water matrices. This critical review focuses on the overall strategies for accurately removing highly toxic emerging pollutants in the presence of typical interferents. The main difficulties hindering the improvement of selectivity in complex matrices are analyzed, implying that it is difficult to adopt a universal approach for multiple targets and water substrates. Selective methods based on assorted principles are proposed aiming to improve the anti-interference ability. Thus, typical approaches and fundamentals to achieve selectivity are subsequently summarized including their mechanism, superiority and inferior position, application scope, improvement method and the bottlenecks. The results show that different methods may be applicable to certain conditions and target pollutants. To better understand the mechanism of each selective method and further select the appropriate method, advanced methods for qualitative and quantitative characterization of selectivity are presented. The processes of adsorption, interaction, electron transfer, and bond breaking are discussed. Some comparable selective quantitative methods are helpful for promoting the development of related fields. The research framework of selectivity removal and its fundamentals are established. Presently, although continuous advances and remarkable achievements have been attained in the selective removal of characteristic organic pollutants, there are still various substantial challenges and opportunities. It is hopeful to inspire the researches on the new generation of water and wastewater treatment technology, which can selectively and preferentially treat characteristic pollutants, and establish a reliable research framework to lead the direction of environmental science.