In response to the decline in natural water sources, treated wastewater (TWW) has been introduced into the water cycle as a new water source for irrigation. However, this practice exposes the agricultural environment to various contaminants of emerging concern (CECs). To better understand their fate in the soil and to effectively predict their bioavailability for plant uptake, there is a need to quantify their concentrations in soil solutions. In this study, we examined the concentration of TWW-derived CECs in soil solution under three scenarios: (1) shifting from irrigation with freshwater (FW) to TWW (FW→TWW), (2) long-term continuous irrigation with TWW (TWW→TWW), and (3) prolonged irrigation with TWW followed by FW (TWW→FW). Carbamazepine, 1H-benzotriazole, lamotrigine, venlafaxine, and thiabendazole were ubiquitous in the TWW (mean concentrations of 125, 945, 180, 3630, and 90 ng/L, respectively) and irrigated soils. Interestingly, their concentrations in the soil solutions were not similar (higher or lower) to the corresponding concentrations in the irrigation water. In both the FW→TWW and TWW→FW irrigation scenarios, lower CECs concentrations were observed in soil solutions compared to the TWW→TWW scenario, indicating that a steady-state condition was not achieved after a single irrigation season (FW→TWW). For example, the concentrations of 1H-benzotriazole in Nir Oz soil solutions were 638, 310, and 1577 ng/L for the three irrigation scenarios (FW→TWW, TWW→FW, and TWW→TWW), respectively. Moreover, CECs concentrations in soil solutions were slightly lower in the TWW→FW irrigation scenario compared to the TWW→TWW scenario. This suggests that rain-fed crops are also exposed to TWW-derived CECs released from the adsorbed phase into the soil solution. The readily available CEC concentration in soil solutions depends on the soil irrigation history and the CEC concentration in the irrigation water, the soil characteristics, and the physicochemical properties of the CEC.

The anticonvulsant drug lamotrigine is a recalcitrant environmental pollutant. It was detected in drinking water, surface water, reclaimed wastewater, arable soils, and even in edible crops. In this work, we studied the mechanisms of lamotrigine transformation by a common redox soil mineral, birnessite, in a single-solute system and in bisolute systems with vanillic acid or o-methoxyphenol. In the single-solute system, 28% of lamotrigine was transformed and 14 transformation products (TPs) were identified. Based on a detailed analysis of the TPs, we suggested that lamotrigine is transformed mainly by oxidation, addition, and dechlorination reactions. In the bisolute systems, the redox-active phenolic compounds enhanced the elimination and transformation of lamotrigine. Vanillic acid was more efficient, generating 92% transformation of lamotrigine (58 TPs were identified), whereas o-methoxyphenol induced 48% transformation (35 TPs were identified). In the bisolute system with phenolic compounds, lamotrigine has possibly been transformed mainly via addition reactions with phenolic compounds and their oxidation products (protocatechuic acid, quinone, and oligomers). Thus, masses of the formed TPs were elevated as compared to the parent compound. The current study demonstrates the important role of redox-active minerals and naturally occurring phenolic compounds in abiotic removal and transformation of a recalcitrant environmental pollutant.

A facile technique for preparing the stable Ag nanoparticles (NPs) of 5-19 nm average size, anchored onto the heat-treated melamine-oxalic acid supramolecular complex is demonstrated. The synthesized material is tested for its catalytic efficiency towards reduction of aqueous 2-CH3-p-nitrophenol to aminophenol using NaBH4 as reducing agent at 28 degrees C. The reaction followed the pseudo first-order kinetics with respect to the nitrophenol concentrations, and the reaction rate constant was determined to be greater than the reported literature values. The superior catalytic activity of the catalyst was attributed to the combined roles of the Ag NPs and carbon substrate enriched with nitrogen functional groups. Notably, the prepared catalyst sustained its reactivity even after eight consecutive test runs without leaching of the metal NPs in the reaction mixture. The results clearly indicate the organic complex precursor-based carbon supported Ag NPs to be an efficient catalyst for removal of recalcitrant organic compounds from wastewater by reduction. (C) 2020 Elsevier B.V. All rights reserved.

The use of nanotechnology to suppress crop diseases is gaining increasing interest in agriculture. Copper sulfide nanoparticles (CuS NPs) were synthesized at 1 : 1 and 1 : 4 ratios of Cu and S and their respective antifungal efficacy was evaluated against the pathogenic activity ofGibberella fujikuroi(bakanae disease) in rice (Oryza sativaL.). In a 2 din vitrostudy, CuS (1 : 1) and CuS (1 : 4) NPs at 50 mg L(-1)decreasedG. fujikuroicolony-forming units (CFU) by 35.7 and 33%, respectively, compared to controls; commercial CuO NPs caused an 18.7% inhibition. In a greenhouse study, treating with both types of CuS NPs at 50 mg L(-1)at the seed stage significantly decreased disease incidence on rice by 35.1 and 45.9%, respectively. Comparatively, CuO NPs achieved only 8.1% disease reduction, and the commercial Cu-based pesticide Kocide 3000 had no impact on disease. Foliar-applied CuO NPs and CuS (1 : 1) NPs decreased disease incidence by 30.0 and 32.5%, respectively, which outperformed CuS (1 : 4) NPs (15%) and Kocide 3000 (12.5%). Notably, CuS (1 : 4) NPs also modulated the shoot salicylic acid (SA) and jasmonic acid (JA) production to enhance the plant defense mechanisms againstG. fujikuroiinfection. These findings provide useful information for improving the delivery efficiency of agrichemicalsvianano-enabled strategies while minimizing their environmental impact, and advance our understanding of the defense mechanisms triggered by the NPs presence in plants.

Natural formation of metal nanoparticles is an important pathway that will modify the fate, behavior, and biological availability of heavy metal ions in the environment. Most work has focused on the ability of natural organic matter (NOM) and extracellular polymeric substances (EPS) to convert metal ions into nanoparticles. However, plant roots, ubiquitous in soil and aquatic environments, may have a significant role in the formation of naturally occurring metal nanoparticles. This work demonstrates the importance of plant roots and associated exudates in mediating the transformation of Ag+ in the presence of sunlight. Using Ag+ as the starting material, transformation took place in three steps: 1) formation of AgCl microcubes (μAgCl) through complexation of Ag+ by plant-released chloride ions in root exudates; 2) stabilization of μAgCl by biomolecules in root exudates; 3) partial photoreduction of μAgCl to Ag(0) nanoparticles (nAg) facilitated by exudate biomolecules. Morphological and compositional changes were observed by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) on the particles from 0-24 h: Cubic AgCl microcrystals were converted into cauliflower-shaped core-shell structures with nAg clusters as the shell and μAgCl as the core. The quantification of Ag+, μAgCl and nAg species over time demonstrates that the transformation kinetics fit (R2 = 0.99) a second-order reaction (k = 1.11 mM-1 h-1). The discovery of plant root exudate-mediated phototransformation of Ag+ adds new knowledge to our understanding of Ag transformation in the plant root zone and will guide the assessment of both exposure and risk in the environment. © 2019 The Royal Society of Chemistry.

Rapid industrialization leads to the introduction of dyes and nanoparticles (NPs) into the environment posing threats to water quality and aquatic organisms. The highly reactive NPs are known to interact with dyes to form stable NPs-dye complexes. Herein, we report the adsorptive interactions of two inorganic NPs, Ag-Ag2S and CeO2 with cationic methylene blue. Experiments were also performed with NPs coated with 2 types of dissolved organic matter. The maximal adsorption capacities for methylene blue with Ag-Ag2S and CeO2 were calculated to be 16.64 and 5.35 mg g−1, respectively. The obtained adsorption capacities are attributed to electrostatic interactions (attractive/repulsive) between the NPs and the dyes and also the van der Waals force of interaction between the dye molecules. DOM coatings on the NPs significantly reduced the adsorption of dyes (maximum adsorption capacities for methylene blue with DOM coated Ag-Ag2S and CeO2 were reduced by ˜40% and ˜61%, respectively; the more hydrophobic DOM coating on the NPs resulted in reduction of adsorption capacity by ˜54 and ˜70%, respectively). Our results suggest that the DOM coatings alter the arrangements of the NPs in the dye solution, creating the active surface sites less accessible for adsorption. Furthermore, the reduction of the adsorption efficiency for the NPs toward dyes with simultaneously addition of DOM is probably due to blockage of the active surface sites by the DOM molecules and the competition between the dye and the DOM.

Copper oxide nanoparticles (CuO NPs), as an antimicrobial nanomaterial, have found many applications in agriculture. Ubiquitous and complex root exudates (RE) in the plant root zone motivates the determination of how specific components of RE interact with CuO NPs. This work aims to reveal the role of maize (Zea mays L.)-derived RE and their components on the aggregation and dissolution of CuO NPs in the rhizosphere. We observed that RE significantly inhibited the aggregation of CuO NPs regardless of ionic strength and electrolyte type. In the presence of RE, the CCC of CuO NPs in NaCl shifted from 30 to 125 mM and the value in CaCl2 shifted from 4 to 20 mM. Furthermore, this inhibition was correlated with molecular weight (MW) of RE fractions. Higher MW fraction (>10 kDa) reduced the aggregation most. We also discovered that RE significantly promoted the dissolution of CuO NPs and lower MW fraction (<3 kDa) RE mainly contributed to this process. Additionally, phytotoxicity of CuO NPs in the presence of RE and different fractions of RE was evaluated. The addition of 20 mg/L RE reduced the seedlings growth rate to 1.89% after 7 days exposure to 25 mg/L CuO NPs, which were significantly lower than the control group (4.82%). Notably, Cu accumulation in plant root tissues was significantly enhanced by 20 mg/L RE. This study provides useful insights into the interactions between RE and CuO NPs, which is of significance for the safe use of CuO NPs-based antimicrobial products in agricultural production.

Water transports organic matter through soils, where mineral-organic associations form to retain dissolved organic matter (“DOM”), influencing terrestrial carbon cycling, nutrient availability for plant growth, and other soil organic matter functions. We combined Fourier transform ion cyclotron resonance mass spectrometry with novel data analysis techniques to examine the role of sorptive fractionation in the associations between Fe(III)-montmorillonite and DOM from composted biosolids (“anthropogenic DOM”). To examine the influence of DOM composition on sorption and sorptive fractionation, we used resin-based separation to produce DOM subsamples with different molecular compositions and chemical properties. A large proportion (45 to 64%) of the initial carbon in every DOM solution sorbed to the Fe(III)-montmorillonite. However, when the compositions of the initial solutions were compared to the sorbed organic matter, the computed changes in composition were lower (10 to 32%). In fact, non-selective sorption was more important than selective sorption in every sample, except for the hydrophilic neutral (HiN) fraction, where high nitrogen content and acidic conditions appeared to enhance sorptive fractionation. The results from this study demonstrate that the importance of sorptive fractionation varies with DOM composition and other factors, and that non-selective sorption can contribute substantially to the formation of mineral-organic associations.

Knowledge of the physicochemical properties of ingestible silver nanoparticles (AgNPs) in the human gastrointestinal tract (GIT) is essential for assessing their bioavailability, bioactivity, and potential health risks. The gastrointestinal fate of AgNPs and silver ions from a commercial dietary supplement was therefore investigated using a simulated human GIT. In the mouth, no dissolution or aggregation of AgNPs occurred, which was attributed to the neutral pH and the formation of biomolecular corona, while the silver ions formed complexes with biomolecules (Ag-biomolecule). In the stomach, aggregation of AgNPs did not occur, but extensive dissolution was observed due to the low pH and the presence of Cl–. In the fed state (after meal), 72% AgNPs (by mass) dissolved, with 74% silver ions forming Ag-biomolecule and 26% forming AgCl. In the fasted state (before meal), 76% AgNPs dissolved, with 82% silver ions forming Ag-biomolecule and 18% forming AgCl. A biomolecular corona around AgNPs, comprised of mucin with multiple sulfhydryl groups, inhibited aggregation and dissolution of AgNPs. In the small intestine, no further dissolution or aggregation of AgNPs occurred, while the silver ions existed only as Ag-biomolecule. These results provide useful information for assessing the bioavailability of ingestible AgNPs and their subsequently potential health risks, and for the safe design and utilization of AgNPs in biomedical applications.Knowledge of the physicochemical properties of ingestible silver nanoparticles (AgNPs) in the human gastrointestinal tract (GIT) is essential for assessing their bioavailability, bioactivity, and potential health risks. The gastrointestinal fate of AgNPs and silver ions from a commercial dietary supplement was therefore investigated using a simulated human GIT. In the mouth, no dissolution or aggregation of AgNPs occurred, which was attributed to the neutral pH and the formation of biomolecular corona, while the silver ions formed complexes with biomolecules (Ag-biomolecule). In the stomach, aggregation of AgNPs did not occur, but extensive dissolution was observed due to the low pH and the presence of Cl–. In the fed state (after meal), 72% AgNPs (by mass) dissolved, with 74% silver ions forming Ag-biomolecule and 26% forming AgCl. In the fasted state (before meal), 76% AgNPs dissolved, with 82% silver ions forming Ag-biomolecule and 18% forming AgCl. A biomolecular corona around AgNPs, comprised of mucin with multiple sulfhydryl groups, inhibited aggregation and dissolution of AgNPs. In the small intestine, no further dissolution or aggregation of AgNPs occurred, while the silver ions existed only as Ag-biomolecule. These results provide useful information for assessing the bioavailability of ingestible AgNPs and their subsequently potential health risks, and for the safe design and utilization of AgNPs in biomedical applications.

Carbon-based nanomaterials have remarkable chemical and biological features. The introduction of supporting magnetic materials onto carbon-based nanoparticles has gained interest owing to their easy separation from heterogeneous systems. Herein, we report the synthesis of a novel composite comprised of single-walled carbon nanotubes, Fe3O4 and Ag nanoparticles with an aim to develop a bifunctional composite for water purification that maintains both high catalytic and antibacterial activities. The composite facilitated decomposition of nitrophenols and methyl orange in the presence of NaBH4 as the reducing agent – maintaining high activity (>90%) following three regeneration cycles. The composite’s catalytic activity was unaffected by the presence of dissolved organic matter (DOM) at an environmentally relevant concentration of 5 mg C L−1. DOM concentration of 50 mg C L−1 slightly decreased the reduction of p-nitrophenol, 2-methyl-p-nitrophenol, and methyl orange (by ∼14%, ∼11%, and ∼10% respectively) but significantly decreased that of o-nitrophenol (by 38%). The composite exhibited high antibacterial activity towards gram-negative and gram-positive bacteria even in the presence of DOM at an environmentally relevant concentration. However, the composite’s efficiency decreased with increase in DOM concentration. This study demonstrates dual catalytic and antibacterial activity of a novel Ag-Fe3O4-single walled carbon nanotube composite material in the absence and presence of DOM, and considers its potential implementation in water/wastewater treatment applications.

Abiotic mechanisms of oxytetracycline degradation by redox-active minerals, Fe(III)-saturated montmorillonite (Fe-SWy) and birnessite (δ-MnO2), were studied to better understand the environmental behavior of tetracycline antibiotics in aqueous systems. Kinetics of dissipation (adsorption, oxidation and formation of transformation products (TPs)), was investigated up to 7 days, and reaction mechanisms were elucidated based on identification of TPs by liquid chromatography mass spectrometry. Oxytetracycline was completely removed from solution by both minerals, however kinetics, TPs and mechanisms were distinct for each mineral. Oxytetracycline oxidation by δ-MnO2 occurred within minutes; 54 identified TPs were detected only in solution, most of them exhibited decreasing levels with time. In contrast, oxytetracycline was completely adsorbed by Fe-SWy, its degradation was slower, only 29 TPs were identified, among them 13 were surface-bound, and most of the TPs accumulated in the system with time. Oxytetracycline transformation by δ-MnO2 involved radicals, as was proven by electrochemical degradation. Reductive dissolution was observed for both minerals. X-ray photoelectron spectroscopy demonstrated accumulation of Fe(II) on Fe-SWy surface, whereas Mn(II) was primarily released from δ-MnO2 surface. Highly oxidized carbon species (i.e., newly formed TPs) were observed on the surface of both minerals interacting with oxytetracycline. This study demonstrates the impact of structure and reactivity of redox-active minerals on removal and decomposition of tetracycline antibiotics in aqueous systems.

Adsorption of dissolved organic matter (DOM) to mineral surfaces is an important process determining DOM bioavailability and carbon sequestration in soils. However, little is known about preferential adsorption of DOM at the molecular level. In this study, DOM originating from composted biosolids was analyzed in order to elucidate DOM adsorptive fractionation by clay soil. Structural changes in DOM due to adsorption to soil were studied using two complementary approaches: (i) macroscale analysis including resin separation and (ii) molecular characterization using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Both approaches demonstrated consistency regarding the DOM adsorptive fractionation. Resin separation showed preferential adsorption of the hydrophobic acid (HoA) fraction by soil surfaces, with up to 70% of total adsorbed carbon; this fraction was apparently responsible for low DOM desorption. FT-ICR MS data demonstrated preferential adsorption of polyphenols, which are components of the HoA fraction. Adsorption of highly oxidized, saturated “carbohydrate-like” molecules was also observed, which might be a result of adsorption of the hydrophilic neutral (HiN) fraction. DOM exhibited concentration-dependent fractionation: enhanced adsorption of highly oxidized compounds at low DOM concentrations, and selective adsorption of less oxidized components at higher DOM concentrations, suggesting that adsorptive fractionation of DOM depended on the extent of its loading. Our findings suggest that a significant amount of carbon originating from the applied DOM was irreversibly stabilized by mineral surfaces. The study demonstrates that both DOM chemical heterogeneity and DOM concentration need to be considered in order to predict DOM reactivity and carbon stabilization in soils.

Irrigation with reclaimed wastewater may result in the ubiquitous presence of pharmaceutical compounds (PCs) and their metabolites in the agroecosystem. In this study, we focused on two highly persistent anticonvulsant drugs, lamotrigine and carbamazepine and two of its metabolites (EP-CBZ and DiOH-CBZ), aiming to elucidate their behavior in agricultural ecosystem using batch and lysimeter experiments. Sorption of the studied compounds by soils was found to be governed mainly by the soil organic matter level. Sorption affinity of compounds to soils followed the order lamotrigine > carbamazepine > EP-CBZ > DiOH-CBZ. Sorption was reversible, and no competition between sorbates in bi-solute systems was observed. The results of the lysimeter studies were in accordance with batch experiment findings, demonstrating accumulation of lamotrigine and carbamazepine in top soil layers enriched with organic matter. Detection of carbamazepine and one of its metabolites in rain-fed wheat previously irrigated with reclaimed wastewater, indicates reversibility of their sorption, resulting in their potential leaching and their availability for plant uptake. This study demonstrates the long-term implication of introduction of PCs to the agroecosystem.

Humic acid (HA)-clay complexes are well known for their contribution to soil structure and environmental processes. Despite extensive research, the mechanisms governing HA adsorption are yet to be resolved. A systematic study was conducted to characterize the adsorption of a soil-derived HA to seven clay minerals. Clay surfaces affected HA adsorption directly due to structural differences and indirectly by altering solution pH. The following order of HA removal was obtained for the clay minerals at their natural pH: illite >> palygorskite > kaolinite > sepiolite > montmorillonite = hectorite >> talc. Removal of HA (precipitation and adsorption) by kaolinite and illite was attributed to the low pH they induce, resulting in protonation of the clay and HA surfaces. In spite of the low pH, the zeta potential for HA remained negative, which promoted HA adsorption to the protonated clay surfaces by ligand exchange. Ionic strength did not affect HA adsorption to clay minerals with low zeta potentials, indicating that charge screening is not a major mechanism of HA adsorption for these minerals, and supporting the suggestion that ligand exchange is the main adsorption mechanism to pH-dependent sites. The increase in ionic strength did, however, promote HA adsorption to clay minerals with high zeta potentials. At pH 89 the order of HA affinity for clay minerals was: palygorskite > sepiolite > montmorillonite = hectorite > kaolinite > illite > talc, emphasizing strong HA interactions with the fibrous clays. This strong affinity was attributed to their large surface areas and to strong interactions with OH groups on these clay surfaces. Results indicated that HA did not enter the intracrystalline channels of the fibrous clays but suggested that their macro-fiber structure facilitates HA adsorption. The sorption of HA to kaolinite further increased in the presence of Cu2+, and the sorption of Cu2+ increased in the presence of HA, due to a number of synergistic effects. This study emphasizes the diverse effects of clay structure and solution chemistry on HA adsorption.