The missing link between carbon nanotubes, dissolved organic matter and organic pollutants
. Advances in Colloid and Interface Science 2019
. Publisher's VersionAbstract
Ternary interactions between carbon nanotubes (CNTs), dissolved organic matter (DOM) and small organic molecules (namely low molecular mass organic pollutants) are of great importance since they can affect the reactivity and fate of all involved compartments in the environment. This review thoroughly assesses existing knowledge on the adsorption of DOM and small organic molecules by CNTs, while giving special attention to (i) the complex nature of DOM, (ii) the ternary rather than binary interactions between CNTs, DOM and the small organic molecules and (iii) the DOM-organic molecule interactions. We discuss in detail the main factors influencing DOM adsorption by CNTs and attempt to differentiate between the role of DOM composition and conformation. We then outline how the presence of DOM influences the adsorption of small organic molecules by CNTs, considering the introduction stage of DOM and the impact of the organic molecule's properties. DOM adsorption by CNTs is highly dependent on its composition and is governed by the size, hydrophobicity and aromaticity of DOM. DOM adsorption was found to alter the assembly of the CNTs, resulting in changes in the distribution of adsorption sites. Small organic molecules may adsorb to residual surface area on the CNTs, to DOM-coating the CNTs or remain in solution, possibly complexed with DOM. This results in their suppressed or enhanced adsorption in comparison to DOM-free media. The physicochemical properties of the organic molecules (hydrophobicity, size, structure and charge) also play a major role in this process. We present knowledge gaps that need clarification such as the extent of DOM desorption from CNTs, the amount of co-adsorbed DOM during competition with small organic molecules for adsorption sites on the CNTs and the behavior of CNTs under realistic conditions. More data generated from experiments using natural DOM rather than dissolved humic substances are required to improve our understanding of the interactions between CNTs and small organic molecules in realistic environmental scenarios. This review provides conclusions and research directions needed to evaluate the nature of interactions between CNTs, DOM and organic pollutants in aquatic systems affected by anthropogenic activities. © 2019 Elsevier B.V.
The pH and concentration dependent interfacial interaction and heteroaggregation between nanoparticulate zero-valent iron and clay mineral particles
. Environmental Science: Nano 2019
2129-2140. Publisher's VersionAbstract
Heteroaggregation with clay mineral particles (CMPs) is significant to the environmental application and fate of increasingly produced nanoparticulate zero-valent iron (nZVI). Co-settling, kinetic aggregation, calculation of the classical Derjaguin-Landau-Verwey-Overbeek interaction energy, and electron microscopic observation were carried out to investigate the interaction between nZVIs (three naked nZVIs of different sizes and one carboxymethyl cellulose (CMC) coated nZVI) and CMPs (kaolinite and montmorillonite). Under pH 6.5 and 9.5 conditions, Lewis acid-base interaction contributed to the attachment between nZVIs and CMPs, while electrostatic attraction was involved in nZVI-CMP attachment under pH 3.5. Compared with the heteroaggregates formed by nZVIs attaching to CMP edges and faces under pH 6.5 and 3.5 conditions, the heteroaggregates were smaller with nZVIs mainly connecting to CMP edges under pH 9.5. Small nZVI homoaggregates were bound to CMP edges at low nZVI concentrations (nZVI/CMP mass ratio at 0.015) with CMP concentrations of 330 mg L-1 and large nZVI-CMP heteroaggregates formed by nZVI bridging with increasing nZVI concentrations. The smallest nZVI exhibited the strongest heteroaggregation with CMPs; the CMC coating inhibited the interfacial interaction and heteroaggregation between nZVIs and CMPs; kaolinite had higher potential to interact with nZVIs under neutral conditions. These findings are helpful for understanding the interaction between nZVIs and minerals and of significance to environmental remediation using nZVIs. © 2019 The Royal Society of Chemistry.
Pharmaceutical and Personal Care Products: From Wastewater Treatment into Agro-Food Systems
. Environmental Science and Technology 2019
. Publisher's VersionAbstract
Irrigation with treated wastewater (TWW) and application of biosolids introduce numerous pharmaceutical and personal care products (PPCPs) into agro-food systems. While the use of TWW and biosolids has many societal benefits, introduction of PPCPs in production agriculture poses potential food safety and human health risks. A comprehensive risk assessment and management scheme of PPCPs in agro-food systems is limited by multiple factors, not least the sheer number of investigated compounds and their diverse structures. Here we follow the fate of PPCPs in the water-soil-produce continuum by considering processes and variables that influence PPCP transfer and accumulation. By analyzing the steps in the soil-plant-human diet nexus, we propose a tiered framework as a path forward to prioritize PPCPs that could have a high potential for plant accumulation and thus pose greatest risk. This article examines research progress to date and current research challenges, highlighting the potential value of leveraging existing knowledge from decades of research on other chemicals such as pesticides. A process-driven scheme is outlined to derive a short list that may be used to refocus our future research efforts on PPCPs and other analogous emerging contaminants in agro-food systems. © 2019 American Chemical Society.
A proof of concept study demonstrating that environmental levels of carbamazepine impair early stages of chick embryonic development
. Environment International 2019
, 583-594. Publisher's VersionAbstract
Carbamazepine (CBZ)is an anticonvulsant drug used for epilepsy and other disorders. Prescription of CBZ during pregnancy increases the risk for congenital malformations. CBZ is ubiquitous in effluents and persistent during wastewater treatment. Thus, it is re-introduced into agricultural ecosystems upon irrigation with reclaimed wastewater. People consuming produce irrigated with reclaimed wastewater were found to be exposed to CBZ. However, environmental concentrations of CBZ (μg L−1)are magnitudes lower than its therapeutic levels (μg ml−1), raising the question of whether and how environmental levels of CBZ affect embryonic development. The chick embryo is a powerful and highly sensitive amniotic model system that enables to assess environmental contaminants in the living organism. Since the chick embryonic development is highly similar to mammalians, yet, it develops in an egg, toxic effects can be directly analyzed in a well-controlled system without maternal influences. This research utilized the chick embryo to test whether CBZ is embryo-toxic by using morphological, cellular, molecular and imaging strategies. Three key embryonic stages were monitored: after blastulation (st.1HH), gastrulation/neurulation (st.8HH)and organogenesis (st.15HH). Here we demonstrate that environmental relevant concentrations of CBZ impair morphogenesis in a dose- and stage- dependent manner. Effects on gastrulation, neural tube closure, differentiation and proliferation were exhibited in early stages by exposing embryos to CBZ dose as low as 0.1 μg L−1. Quantification of developmental progression revealed a significant difference in the total score obtained by CBZ-treated embryos compared to controls (up to 5-fold difference, p < 0.05). Yet, defects were unnoticed as embryos passed gastrulation/neurulation. This study provides the first evidence for teratogenic effect of environmental-relevant concentrations of CBZ in amniotic embryos that impair early but not late stages of development. These findings call for in-depth risk analysis to ensure that the environmental presence of CBZ and other drugs is not causing irreversible ecological and public-health damages. © 2019
Transformation of Ag ions into Ag nanoparticle-loaded AgCl microcubes in the plant root zone
. Environmental Science: Nano 2019
1099-1110. Publisher's VersionAbstract
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.
Transformation of lamotrigine by white-rot fungus Pleurotus ostreatus
. Environmental Pollution 2019
, 546-553. Publisher's VersionAbstract
One of the most persistent pharmaceutical compounds commonly found in treated wastewater is lamotrigine (LTG). It has also been detected in soils and crops irrigated with treated wastewater. Here we focused on the ability of the white-rot edible mushroom Pleurotus ostreatus to remove and transform LTG in liquid cultures. At concentrations of environmental relevance (1 and 10 μg L−1) LTG was almost completely removed from the culture medium within 20 days. To elucidate the mechanism of LTG removal and transformation, we applied a physiological-based approach using inhibitors and a competing agent. These experiments were conducted at a higher concentration for metabolites detection. Based on identification of sulfur-containing metabolites and LTG N2-oxide and the effect of specific inhibitors, cytochrome P450 oxidation is suggested as one of the reaction mechanisms leading to LTG transformation. The variety and number of transformation products (i.e., conjugates) found in the current study were larger than reported in mammals. Moreover, known conjugates with glucuronide, glutathione, or cysteine/glycine, were not found in our system. Since the majority of the identified transformation products were conjugates of LTG, this study highlights the persistence of LTG as an organic pollutant in ecosystems exposed to wastewater. © 2019 Elsevier Ltd
Interactions of organic dye with Ag- and Ce-nano-assemblies: Influence of dissolved organic matter
. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2019
, 683 - 694. Publisher's VersionAbstract
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.
Maize (Zea mays L.) root exudates modify the surface chemistry of CuO nanoparticles: Altered aggregation, dissolution and toxicity
. Science of The Total Environment 2019
, 502 - 510. Publisher's VersionAbstract
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.
Emerging investigator series: towards a framework for establishing the impacts of pharmaceuticals in wastewater irrigation systems on agro-ecosystems and human health
. Environmental Science: Processes & Impacts 2019
, 605 - 622. Publisher's VersionAbstract
Use of reclaimed wastewater for agricultural irrigation is seen as an attractive option to meet agricultural water demands of a growing number of countries suffering from water scarcity. However, reclaimed wastewater contains pollutants which are introduced to the agro-environment during the irrigation process. While water reuse guidelines do consider selected classes of pollutants, they do not account for the presence of pollutants of emerging concern such as pharmaceuticals and the potential risks these may pose. Here we use source–pathway–receptor analysis (S–P–R) to develop a holistic framework for evaluating the impacts of pharmaceuticals, present in wastewater used for agricultural irrigation, on human and ecosystem health and evaluate the data availability for the framework components. The developed framework comprised of 34 processes and compartments but a good level of knowledge was available for only five of these suggesting that currently it is not possible to fully establish the impacts of pharmaceuticals in wastewater irrigation systems. To address this, work is urgently needed to understand the fate and transport of pharmaceuticals in arable soil systems and the effects of chronic low-level exposure to these substances on microbes, invertebrates, plants, wildlife and humans. In addition, research pertaining to the fate, uptake and effects of pharmaceutical mixtures and metabolites is lacking as well as data on bio-accessibility of pharmaceuticals after ingestion. Scientific advancements in the five areas prioritised in terms of future research are needed before we are able to fully quantify the agricultural and human health risks associated with reclaimed wastewater use.
Pharmacokinetics in Plants: Carbamazepine and Its Interactions with Lamotrigine
. Environmental Science & Technology 2018
, 6957 - 6964. Publisher's VersionAbstract
Carbamazepine and lamotrigine prescribed antiepileptic drugs are highly persistent in the environment and were detected in crops irrigated with reclaimed wastewater. This study reports pharmacokinetics of the two drugs and their metabolites in cucumber plants under hydroponic culture, testing their uptake, translocation, and transformation over 96 h in single and bisolute systems at varying pH. Ruling out root adsorption and transformations in the nutrient solution, we demonstrate that carbamazepine root uptake is largely affected by the concentration gradient across the membrane. Unlike carbamazepine, lamotrigine is adsorbed to the root and undergoes ion trapping in root cells thus its translocation to the shoots is limited. On the basis of that, carbamazepine uptake was not affected by the presence of lamotrigine, while lamotrigine uptake was enhanced in the presence of carbamazepine. Transformation of carbamazepine in the roots was slightly reduced in the presence of lamotrigine. Carbamazepine metabolism was far more pronounced in the shoots than in the roots, indicating that most of the metabolism occurs in the leaves, probably due to higher concentration and longer residence time. This study indicates that the uptake of small nonionic pharmaceuticals is passive and governed by diffusion across the root membrane.Carbamazepine and lamotrigine prescribed antiepileptic drugs are highly persistent in the environment and were detected in crops irrigated with reclaimed wastewater. This study reports pharmacokinetics of the two drugs and their metabolites in cucumber plants under hydroponic culture, testing their uptake, translocation, and transformation over 96 h in single and bisolute systems at varying pH. Ruling out root adsorption and transformations in the nutrient solution, we demonstrate that carbamazepine root uptake is largely affected by the concentration gradient across the membrane. Unlike carbamazepine, lamotrigine is adsorbed to the root and undergoes ion trapping in root cells thus its translocation to the shoots is limited. On the basis of that, carbamazepine uptake was not affected by the presence of lamotrigine, while lamotrigine uptake was enhanced in the presence of carbamazepine. Transformation of carbamazepine in the roots was slightly reduced in the presence of lamotrigine. Carbamazepine metabolism was far more pronounced in the shoots than in the roots, indicating that most of the metabolism occurs in the leaves, probably due to higher concentration and longer residence time. This study indicates that the uptake of small nonionic pharmaceuticals is passive and governed by diffusion across the root membrane.
Composition-Dependent Sorptive Fractionation of Anthropogenic Dissolved Organic Matter by Fe(III)-Montmorillonite
. Soil Systems 2018
. Publisher's VersionAbstract
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.
Bacterial inactivation by a carbon nanotube–iron oxide nanocomposite: a mechanistic study using E. coli mutants
. Environmental Science: Nano 2018
372 - 380. Publisher's VersionAbstract
Waterborne pathogens are a major health threat and must be eliminated to guarantee safe usage of water for potable purposes. For this purpose, a new carbon-based nanomaterial composed of single-walled carbon nanotubes (SWCNTs) and iron oxides was constructed for bacterial inactivation. Owing to its magnetic properties, the SWCNT–iron oxide nanocomposite may serve as a reusable antimicrobial agent. The nanocomposite material exhibited high antimicrobial activity against Escherichia coli. Successful reuse of the nanocomposite material was achieved by washing with calcium chloride and distilled water, which restored its performance for several successive cycles. To investigate the cytotoxicity mechanisms of the nanocomposite material, we exposed it to single-gene knockout mutant strains of E. coli. Mutants bearing shorter lipopolysaccharide (LPS) layers in the outer membrane (ΔrfaC and ΔrfaG) demonstrated an increased sensitivity in comparison to the wildtype strain, exemplified in enhanced removal by the nanocomposite material. This finding suggests that the LPS acts as a protective shield against the nanocomposite material. Inactivation of mutants impaired in specific oxidative stress defense mechanisms (ΔsodA, ΔkatG and ΔsoxS) emphasized that oxidative stress plays a significant role in the inactivation mechanism of the nanocomposite. This study sheds light on the mechanisms of bacterial inactivation by carbon-based nanomaterials and advances their potential implementation for water disinfection.
Multifunctional carbon nanotubes-iron oxide-Ag composite for water purification
. In EGU General Assembly Conference Abstracts
; EGU General Assembly Conference Abstracts; 2018; Vol. 20, pp. 2434.
Pesticide load dynamics during stormwater flow events in Mediterranean coastal streams: Alexander stream case study
. Science of The Total Environment 2018
, 168 - 177. Publisher's VersionAbstract
Cultivated land is a major source of pesticides, which are transported with the runoff water and eroded soil during rainfall events and pollute riverine and estuarine environments. Common ecotoxicological assessments of riverine systems are mainly based on water sampling and analysis of only the dissolved phase, and address a single pesticide's toxicological impact under laboratory conditions. A clear overview of mixtures of pesticides in the adsorbed and dissolved phases is missing, and therefore the full ecotoxicological impact is not fully addressed. The aim of this study was to characterize and quantify pesticide concentrations in both suspended sediment and dissolved phases, to provide a better understanding of pesticide-load dynamics during storm events in coastal streams in a Mediterranean climate. High-resolution sampling campaigns of seven flood events were conducted during two rainy seasons in Alexander stream, Israel. Samples of suspended sediments were separated from the solution and both media were analyzed separately for 250 pesticides. A total of 63 pesticides were detected; 18 and 16 pesticides were found solely in the suspended sediments and solution, respectively. Significant differences were observed among the pesticide groups: only 7% of herbicide, 20% of fungicide and 42% of insecticide load was transported with the suspended sediments. However, in both dissolved and adsorbed phases, a mix of pesticides was found which were graded from “mobile” to “non-mobile” with varied distribution coefficients. Diuron, and tebuconazole were frequently found in large quantities in both phases. Whereas insecticide and fungicide transport is likely governed by application time and method, the governing factor for herbicide load was the magnitude of the stream discharge. The results show a complex dynamic of pesticide load affected by excessive use of pesticides, which should be taken into consideration when designing projects to monitor riverine and estuarine water quality.
Transformation and Speciation Analysis of Silver Nanoparticles of Dietary Supplement in Simulated Human Gastrointestinal Tract
. Environmental Science & Technology 2018
, 8792 - 8800. Publisher's VersionAbstract
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.
Dual functionality of an Ag-Fe3O4-carbon nanotube composite material: Catalytic reduction and antibacterial activity
. Journal of Environmental Chemical Engineering 2018
4103 - 4113. Publisher's VersionAbstract
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.
Transformation of oxytetracycline by redox-active Fe(III)- and Mn(IV)-containing minerals: Processes and mechanisms
. Water Research 2018
, 136 - 145. Publisher's VersionAbstract
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.
Adsorptive fractionation of dissolved organic matter (DOM) by mineral soil: Macroscale approach and molecular insight
. Organic Geochemistry 2017
, 113 - 124. Publisher's VersionAbstract
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.
An LC-MS/MS method for the determination of 28 polar environmental contaminants and metabolites in vegetables irrigated with treated municipal wastewater
. Anal. Methods 2017
1273-1281. Publisher's VersionAbstract
An analytical method for the simultaneous determination of 28 wastewater-derived contaminants and possible metabolites (e.g. carbamazepine, 10,11-epoxy-carbamazepine, benzotriazole, lamotrigine, and diclofenac) in common plant tissues with high water content (lettuce, cabbage, and tomato) was developed and validated. The developed method combines solid–liquid extraction, without the need for a clean-up step, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) with electrospray ionization in positive and negative modes. This method was compared with the known QuEChERS method and exhibited better analytical performance. Method detection limits of ≤2.0 ng g−1 dry weight and absolute recoveries of >60% with high intra- and inter-day precision (RSD < 10%) could be achieved for 71% of the target analytes in four different matrices (cabbage, lettuce and tomato leaves, and tomato fruits). Compared to the QuEChERS method, the developed method allows the determination of a wide range of compounds with different physical–chemical properties (neutral, acidic, and basic) and considers even possible metabolites of pharmaceuticals in plant materials. The developed method was successfully applied to analyse wastewater-derived contaminants and their metabolites in plants which were grown under greenhouse and real field conditions. It could be shown that this method is suitable for the sensitive determination of environmental contaminants originating from treated wastewater and a range of their metabolites in irrigated plants and their edible parts. Due to its broadness the extraction method should also be suitable for screening of unknown contaminants and metabolites by LC high-resolution mass spectrometry.