Efficient Catalytic Oxidation of Ethylene at 0 °C on an in Situ Carbon Modified Pt Catalyst Supported on SBA-15.

The design of efficient catalysts for catalytic ethylene (C2H4) oxidation is of crucial importance for extending the shelf life of fruits and vegetables. Herein, a carbon modified SBA-15 supported Pt catalyst (Pt/CSBA-15) was prepared in situ by a facile solid phase grinding-infiltration-inert atmosphere calcination method. Characterization results reveal that in the Pt/CSBA-15 catalysts thin carbon layers are successfully formed in the hexagonal pores of SBA-15. Additionally, Pt particles are well dispersed in the channels of SBA-15, and Pt/CSBA-15 has a smaller Pt particle size than the catalyst without carbon modification (i.e., Pt/SBA-15). O2 is more feasibly adsorbed and activated on small-sized Pt particles, and in situ formed carbon species enhance the hydrophobicity of catalysts. As a result, both 3Pt/CSBA-15 and 5Pt/CSBA-15 are able to maintain 100% conversion of 50 ppm of C2H4 for more than 7 h at 0 °C. 3Pt/CSBA-15 even achieves 81.5% C2H4 conversion and 71.6% CO2 yield after 20 h, exhibiting much more prominent catalytic performances than 3Pt/SBA-15. DFT calculations and in situ FTIR measurements confirm that small-sized Pt particles possess strong O2 affinity to promote O2 adsorption, and in situ formed hydrophobic carbon layers efficiently suppress competitive H2O adsorption. Such a unique one-step catalyst preparation method for regulating the size of metal particles and the hydrophobicity of catalysts can be perfectly utilized to develop simple and efficient hydrophobic catalysts applied in low-temperature oxidation of C2H4.

Pharmacokinetics of the Recalcitrant Drug Lamotrigine: Identification and Distribution of Metabolites in Cucumber Plants.

Treated wastewater is an important source of water for irrigation. As a result, irrigated crops are chronically exposed to wastewater-derived pharmaceuticals, such as the anticonvulsant drug lamotrigine. Lamotrigine is known to be taken up by plants, but its plant-derived metabolites and their distribution in different plant organs are unknown. This study aimed to detect and identify metabolites of lamotrigine in cucumber plants grown for 35 days in a hydroponic solution by using LC-MS/MS (Orbitrap) analysis. Our data showed that 96% of the lamotrigine taken up was metabolized. Sixteen metabolites possessing a lamotrigine core structure were detected. Reference standards confirmed two; five were tentatively identified, and nine molecular formulas were assigned. The data suggest that lamotrigine is metabolized via N-carbamylation, N-glucosidation, N-alkylation, N-formylation, N-oxidation, and amidine hydrolysis. The metabolites LTG-N2-oxide, M284, M312, and M370 were most likely produced in the roots and were translocated to the leaves. Metabolites M272, M312, M314, M354, M368, M370, and M418 were dominant in leaves. Only a few metabolites were detected in the fruits. With an increasing exposure time, lamotrigine leaf concentrations decreased because of continuous metabolism. Our data showed that the metabolism of lamotrigine in a plant is fast and that a majority of metabolites are concentrated in the roots and leaves.

Sorption and Mobility of Charged Organic Compounds: How to Confront and Overcome Limitations in Their Assessment.

Permanently charged and ionizable organic compounds (IOC) are a large and diverse group of compounds belonging to many contaminant classes, including pharmaceuticals, pesticides, industrial chemicals, and natural toxins. Sorption and mobility of IOCs are distinctively different from those of neutral compounds. Due to electrostatic interactions with natural sorbents, existing concepts for describing neutral organic contaminant sorption, and by extension mobility, are inadequate for IOC. Predictive models developed for neutral compounds are based on octanol-water partitioning of compounds (Kow) and organic-carbon content of soil/sediment, which is used to normalize sorption measurements (KOC). We revisit those concepts and their translation to IOC (Dow and DOC) and discuss compound and soil properties determining sorption of IOC under water saturated conditions. Highlighting possible complementary and/or alternative approaches to better assess IOC mobility, we discuss implications on their regulation and risk assessment. The development of better models for IOC mobility needs consistent and reliable sorption measurements at well-defined chemical conditions in natural porewater, better IOC-, as well as sorbent characterization. Such models should be complemented by monitoring data from the natural environment. The state of knowledge presented here may guide urgently needed future investigations in this field for researchers, engineers, and regulators.

Abiotic Transformation of Lamotrigine by Redox-Active Mineral and Phenolic Compounds.

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.

Ecological Risk Dynamics of Pharmaceuticals in Micro-Estuary Environments.

Micro-estuarine ecosystems have a surface area <1 km2 and are abundant in Mediterranean regions. As a result of their small size, these systems are particularly vulnerable to the effects of chemical pollution. Due to the fluctuating flow conditions of base flow dominated by treated wastewater effluents and flood events transporting rural and urban non-point-source pollution, micro-estuaries are under a dynamic risk regime, consequently struggling to provide ecological services. This 2 year study explored the occurrence and risks of pharmaceutical contamination in the Alexander micro-estuary in Israel. Pharmaceuticals were detected in all samples (n = 280) at as high as 18 µg L-1 in flood events and 14 µg L-1 in base flow. The pharmaceutical mixture composition was affected by flow conditions with carbamazepine dominating the base flow and caffeine dominating flood events. The median annual risk quotients for fish, crustaceans, and algae were 19.6, 5.2, and 4.5, respectively, indicating that pharmaceuticals pose a high risk to the ecosystem. Ibuprofen, carbamazepine, and caffeine contributed most to the risk quotients. The current work highlights that micro-estuary ecosystems, like the Alexander estuary, are continuously exposed to pharmaceuticals and most likely to other pollutants, placing these ecologically important systems under an elevated risk in comparison to the more frequently studied large estuarine systems.

Pharmaceutical and Personal Care Products: From Wastewater Treatment into Agro-Food Systems.

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.

Pharmacokinetics in Plants: Carbamazepine and Its Interactions with Lamotrigine.

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.

Transformation and Speciation Analysis of Silver Nanoparticles of Dietary Supplement in Simulated Human Gastrointestinal Tract.

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.

Human Exposure to Wastewater-Derived Pharmaceuticals in Fresh Produce: A Randomized Controlled Trial Focusing on Carbamazepine.

Fresh water scarcity has led to increased use of reclaimed wastewater as an alternative and reliable source for crop irrigation. Beyond microbiological safety, concerns have been raised regarding contamination of reclaimed wastewater by xenobiotics including pharmaceuticals. This study focuses on carbamazepine, an anticonvulsant drug which is ubiquitously detected in reclaimed wastewater, highly persistent in soil, and taken up by crops. In a randomized controlled trial we demonstrate that healthy individuals consuming reclaimed wastewater-irrigated produce excreted carbamazepine and its metabolites in their urine, while subjects consuming fresh water-irrigated produce excreted undetectable or significantly lower levels of carbamazepine. We also report that the carbamazepine metabolite pattern at this low exposure level differed from that observed at therapeutic doses. This "proof of concept" study demonstrates that human exposure to xenobiotics occurs through ingestion of reclaimed wastewater-irrigated produce, providing real world data which could guide risk assessments and policy designed to ensure the safe use of wastewater for crop irrigation.