Advancing Simultaneous Extraction and Sequential Single-Particle ICP-MS Analysis for Metallic Nanoparticle Mixtures in Plant Tissues.

Engineered nanoparticles (ENPs) have been increasingly used in agricultural operations, leading to an urgent need for robust methods to analyze co-occurring ENPs in plant tissues. In response, this study advanced the simultaneous extraction of coexisting silver, cerium oxide, and copper oxide ENPs in lettuce shoots and roots using macerozyme R-10 and analyzed them by single-particle inductively coupled plasma-mass spectrometry (ICP-MS). Additionally, the standard stock suspensions of the ENPs were stabilized with citrate, and the long-term stability (up to 5 months) was examined for the first time. The method performance results displayed satisfactory accuracies and precisions and achieved low particle concentration and particle size detection limits. Significantly, the oven drying process was proved not to impact the properties of the ENPs; therefore, oven-dried lettuce tissues were used in this study, which markedly expanded the applicability of this method. This robust methodology provides a timely approach to characterize and quantify multiple coexisting ENPs in plants.

Mutual Effects and Uptake of Organic Contaminants and Nanoplastics by Lettuce in Co-Exposure.

Organic contaminants, such as pesticides and pharmaceuticals, are commonly found in agricultural systems. With the growing use of plastic products, micro- and nanoplastics (MNPs) are increasingly detected in these agricultural systems, necessitating research into their interactions and joint effects to truly understand their impact. Unfortunately, while there has been a long history of research into the uptake of organic pollutants by plants, similar research with MNPs is only beginning, and studies on their mutual effects and plant uptake are extremely rare. In this study, we examined the effects of three agriculturally relevant organic pollutants with distinctive hydrophobicity as measured by log KOW (trimethoprim: 0.91, atrazine: 2.61, and ibuprofen: 3.97) and 500 nm polystyrene nanoplastics on their uptake and accumulation by lettuce at two different salinity levels. Our results showed that nanoplastics increased the shoot concentration of ibuprofen by 77.4 and 309% in nonsaline and saline conditions, respectively. Alternatively, organic co-contaminants slightly lowered the PS NPs uptake in lettuce with a more pronounced decrease in saline water. These results underscore the impactful interactions of hydrophobic organic pollutants and increasing MNPs on a dynamic global environment.

Quantifying the Chemical Composition and Real-Time Mass Loading of Nanoplastic Particles in the Atmosphere Using Aerosol Mass Spectrometry.

Plastic debris, including nanoplastic particles (NPPs), has emerged as an important global environmental issue due to its detrimental effects on human health, ecosystems, and climate. Atmospheric processes play an important role in the transportation and fate of plastic particles in the environment. In this study, a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was employed to establish the first online approach for identification and quantification of airborne submicrometer polystyrene (PS) NPPs from laboratory-generated and ambient aerosols. The fragmentation ion C8H8+ is identified as the major tracer ion for PS nanoplastic particles, achieving an 1-h detection limit of 4.96 ng/m3. Ambient PS NPPs measured at an urban location in Texas are quantified to be 30 ± 20 ng/m3 by applying the AMS data with a constrained positive matrix factorization (PMF) method using the multilinear engine (ME-2). Careful analysis of ambient data reveals that atmospheric PS NPPs were enhanced as air mass passed through a waste incinerator plant, suggesting that incineration of waste may serve as a source of ambient NPPs. The online quantification of NPPs achieved through this study can significantly improve our understanding of the source, transport, fate, and climate effects of atmospheric NPPs to mitigate this emerging global environmental issue.

AI-assisted systematic review on remediation of contaminated soils with PAHs and heavy metals.

This systematic review addresses soil contamination by crude oil, a pressing global environmental issue, by exploring effective treatment strategies for sites co-contaminated with heavy metals and polycyclic aromatic hydrocarbons (PAHs). Our study aims to answer pivotal research questions: (1) What are the interaction mechanisms between heavy metals and PAHs in contaminated soils, and how do these affect the efficacy of different remediation methods? (2) What are the challenges and limitations of combined remediation techniques for co-contaminated soils compared to single-treatment methods in terms of efficiency, stability, and specificity? (3) How do various factors influence the effectiveness of biological, chemical, and physical remediation methods, both individually and combined, in co-contaminated soils, and what role do specific agents play in the degradation, immobilization, or removal of heavy metals and PAHs under diverse environmental conditions? (4) Do AI-powered search tools offer a superior alternative to conventional search methodologies for executing an exhaustive systematic review? Utilizing big-data analytics and AI tools such as Litmaps.co, ResearchRabbit, and MAXQDA, this study conducts a thorough analysis of remediation techniques for soils co-contaminated with heavy metals and PAHs. It emphasizes the significance of cation-π interactions and soil composition in dictating the solubility and behavior of these pollutants. The study pays particular attention to the interplay between heavy metals and PAH solubility, as well as the impact of soil properties like clay type and organic matter on heavy metal adsorption, which results in nonlinear sorption patterns. The research identifies a growing trend towards employing combined remediation techniques, especially biological strategies like biostimulation-bioaugmentation, noting their effectiveness in laboratory settings, albeit with potentially higher costs in field applications. Plants such as Medicago sativa L. and Solanum nigrum L. are highlighted for their effectiveness in phytoremediation, working synergistically with beneficial microbes to decompose contaminants. Furthermore, the study illustrates that the incorporation of biochar and surfactants, along with chelating agents like EDTA, can significantly enhance treatment efficiency. However, the research acknowledges that varying environmental conditions necessitate site-specific adaptations in remediation strategies. Life Cycle Assessment (LCA) findings indicate that while high-energy methods like Steam Enhanced Extraction and Thermal Resistivity - ERH are effective, they also entail substantial environmental and financial costs. Conversely, Natural Attenuation, despite being a low-impact and cost-effective option, may require prolonged monitoring. The study advocates for an integrative approach to soil remediation, one that harmoniously balances environmental sustainability, cost-effectiveness, and the specific requirements of contaminated sites. It underscores the necessity of a holistic strategy that combines various remediation methods, tailored to meet both regulatory compliance and the long-term sustainability of decontamination efforts.

Fate and distribution of orally-ingested CeO2-nanoparticles based on a mouse model: Implication for human health.

The use of nanoparticles in agrichemical formula and food products as additives has increased their chances of accumulation in humans via oral intake. Due to their potential toxicity, it is critical to understand their fate and distribution following oral intake. Cerium oxide nanoparticle (CeO2NP) is commonly used in agriculture and is highly stable in the environment. As such, it has been used as a model chemical to investigate nanoparticle's distribution and clearance. Based on their estimated human exposure levels, 0.15-0.75 mg/kg body weight/day of CeO2NPs with different sizes and surface charges (30-50 nm with negative charge and <25 nm with positive charge) were gavaged into C57BL/6 female mice daily. After 10-d, 50% of mice in each treatment were terminated, with the remaining being gavaged with 0.2 mL of deionized water daily for 7-d. Mouse organ tissues, blood, feces, and urine were collected at termination. At the tested levels, CeO2NPs displayed minimal overt toxicity to the mice, with their accumulation in various organs being negligible. Fecal discharge as the predominant clearance pathway took less than 7-d regardless of charges. Single particle inductively coupled plasma mass spectrometry analysis demonstrated minimal aggregation of CeO2NPs in the gastrointestinal tract. These findings suggest that nanoparticle additives >25 nm are unlikely to accumulate in mouse organ after oral intake, indicating limited impacts on human health.

Single atom catalyst-mediated generation of reactive species in water treatment.

Water is one of the most essential components in the sustainable development goals (SDGs) of the United Nations. With worsening global water scarcity, especially in some developing countries, water reuse is gaining increasing acceptance. A key challenge in water treatment by conventional treatment processes is the difficulty of treating low concentrations of pollutants (micromolar to nanomolar) in the presence of much higher levels of inorganic ions and natural organic matter (NOM) in water (or real water matrices). Advanced oxidation processes (AOPs) have emerged as an attractive treatment technology that generates reactive species with high redox potentials (E0) (e.g., hydroxyl radical (HO˙), singlet oxygen (1O2), sulfate radical (SO4˙-), and high-valent metals like iron(IV) (Fe(IV)), copper(III) (Cu(III)), and cobalt(IV) (Co(IV))). The use of single atom catalysts (SACs) in AOPs and water treatment technologies has appeared only recently. This review introduces the application of SACs in the activation of hydrogen peroxide and persulfate to produce reactive species in treatment processes. A significant part of the review is devoted to the mechanistic aspects of traditional AOPs and their comparison with those triggered by SACs. The radical species, SO4˙- and HO˙, which are produced in both traditional and SACs-activated AOPs, have higher redox potentials than non-radical species, 1O2 and high-valent metal species. However, SO4˙- and HO˙ radicals are non-selective and easily affected by components of water while non-radicals resist the impact of such constituents in water. Significantly, SACs with varying coordination environments and structures can be tuned to exclusively generate non-radical species to treat water with a complex matrix. Almost no influence of chloride, carbonate, phosphate, and NOM was observed on the performance of SACs in treating pollutants in water when nonradical species dominate. Therefore, the appropriately designed SACs represent game-changers in purifying water vs. AOPs with high efficiency and minimal interference from constituents of polluted water to meet the goals of water sustainability.

Enhanced Oxidation of Antibiotics by Ferrate Mediated with Natural Organic Matter: Role of Phenolic Moieties.

The increasing presence of antibiotics in water sources threatens public health and ecosystems. Various treatments have been previously applied to degrade antibiotics, yet their efficiency is commonly hindered by the presence of natural organic matter (NOM) in water. On the contrary, we show here that nine types of NOM and NOM model compounds improved the removal of trimethoprim and sulfamethoxazole by ferrate(VI) (FeVIO42-, Fe(VI)) under mild alkaline conditions. This is probably associated with the presence of phenolic moieties in NOMs, as suggested by first-order kinetics using NOM, phenol, and hydroquinone. Electron paramagnetic resonance reveals that NOM radicals are generated within milliseconds in the Fe(VI)-NOM system via single-electron transfer from NOM to Fe(VI) with the formation of Fe(V). The dominance of the Fe(V) reaction with antibiotics resulted in their enhanced removal despite concurrent reactions between Fe(V) and NOM moieties, the radicals, and water. Kinetic modeling considering Fe(V) explains the enhanced kinetics of antibiotics abatement at low phenol concentrations. Experiments with humic and fulvic acids of lake and river waters show similar results, thus supporting the enhanced abatement of antibiotics in real water situations.

Mobilization of Colloid- and Nanoparticle-Bound Arsenic in Contaminated Paddy Soils during Reduction and Reoxidation.

The association of arsenic (As) with colloidal particles could facilitate its transport to adjacent water systems or alter its availability in soil-rice systems. However, little is known about the size distribution and composition of particle-bound As in paddy soils, particularly under changing redox conditions. Here, we incubated four As-contaminated paddy soils with distinctive geochemical properties to study the mobilization of particle-bound As during soil reduction and subsequent reoxidation. Using transmission electron microscopy-energy dispersive spectroscopy and asymmetric flow field-flow fractionation, we identified organic matter (OM)-stabilized colloidal Fe, most likely in the form of (oxy)hydroxide-clay composite, as the main arsenic carriers. Specifically, colloidal As was mainly associated with two size fractions of 0.3-40 and >130 kDa. Soil reduction facilitated the release of As from both fractions, whereas reoxidation caused their rapid sedimentation, coinciding with solution Fe variations. Further quantitative analysis demonstrated that As concentrations positively correlated with both Fe and OM concentrations at nanometric scales (0.3-40 kDa) in all studied soils during reduction and reoxidation, yet the correlations are pH-dependent. This study provides a quantitative and size-resolved understanding of particle-bound As in paddy soils, highlighting the importance of nanometric Fe-OM-As interactions in paddy As geochemical cycling.

Reaction of FeaqII with Peroxymonosulfate and Peroxydisulfate in the Presence of Bicarbonate: Formation of FeaqIV and Carbonate Radical Anions.

Many advanced oxidation processes (AOPs) use Fenton-like reactions to degrade organic pollutants by activating peroxymonosulfate (HSO5-, PMS) or peroxydisulfate (S2O82-, PDS) with Fe(H2O)62+ (FeaqII). This paper presents results on the kinetics and mechanisms of reactions between FeaqII and PMS or PDS in the absence and presence of bicarbonate (HCO3-) at different pH. In the absence of HCO3-, FeaqIV, rather than the commonly assumed SO4•-, is the dominant oxidizing species. Multianalytical methods verified the selective conversion of dimethyl sulfoxide (DMSO) and phenyl methyl sulfoxide (PMSO) to dimethyl sulfone (DMSO2) and phenyl methyl sulfone (PMSO2), respectively, confirming the generation of FeaqIV by the FeaqII-PMS/PDS systems without HCO3-. Significantly, in the presence of environmentally relevant concentrations of HCO3-, a carbonate radical anion (CO3•-) becomes the dominant reactive species as confirmed by the electron paramagnetic resonance (EPR) analysis. The new findings suggest that the mechanisms of the persulfate-based Fenton-like reactions in natural environments might differ remarkably from those obtained in ideal conditions. Using sulfonamide antibiotics (sulfamethoxazole (SMX) and sulfadimethoxine (SDM)) as model contaminants, our study further demonstrated the different reactivities of FeaqIV and CO3•- in the FeaqII-PMS/PDS systems. The results shed significant light on advancing the persulfate-based AOPs to oxidize pollutants in natural water.

Iron-based nanomaterials reduce cadmium toxicity in rice (Oryza sativa L.) by modulating phytohormones, phytochelatin, cadmium transport genes and iron plaque formation.

Rice is known to accumulate cadmium (Cd) in its grains, causing a severe threat to billions of people worldwide. The possible phytotoxicity and mechanism of 50-200 mg/L hydroxyapatite NPs (nHA), iron oxide NPs (nFe2O3) or nano zero valent iron (nZVI) co-exposed with Cd (100 µM) in rice seedlings were investigated. Three types of nanoparticles significantly reduced the bioaccumulation of Cd in rice shoots by 16-63%, with nZVI showing the greatest effect, followed by nHA and nFe2O3. A decrease in Cd content in the roots was observed only in the nZVI treatment, with values ranging from 8 to 19%. Correspondingly, nZVI showed the best results in promoting plant growth, increasing rice plant height, shoot and root biomass by 13%, 29% and 42%. In vitro studies showed that nZVI reduced the content of Cd in the solution by 20-52% through adsorption, which might have contributed to the immobilization of Cd in root. Importantly, the nZVI treatment resulted in 267% more iron plaques on the root surface, which acted as a barrier to hinder the entry of Cd. Moreover, all three nanoparticles significantly reduced the oxidative stress induced by Cd by regulating phytohormones, phytochelatin, inorganic homeostasis and the expression of genes associated with Cd uptake and transport. Overall, this study elucidates for the first time the multiple complementing mechanisms for some nanoparticles to reduce Cd uptake and transport in rice and provides theoretical basis for applying nanoparticles for reducing Cd accumulation in edible plants.

Bioavailability, phytotoxicity and plant uptake of per-and polyfluoroalkyl substances (PFAS): A review.

Per- and polyfluoroalkyl substances (PFAS) are a group of legacy and emerging contaminants containing at least one aliphatic perfluorocarbon moiety. They display rapid and extensive transport in the environment due to their generally high water-solubility and weak adsorption onto soil particles. Because of their widespread presence in the environment and known toxicity, PFAS has become a serious threat to the ecosystem and public health. Plants are an essential component of the ecosystem and their uptake and accumulation of PFAS affect the fate and transport of PFAS in the ecosystem and has strong implications for human health. It is therefore imperative to investigate the interactions of plants with PFAS. This review presents a detailed discussion on the mechanisms of the bioavailability and plant uptake of PFAS, and essential factors affecting these processes. The phytotoxic effects of PFAS at physiological, biochemical, and molecular level were also carefully reviewed. At the end, key research gaps were identified, and future research needs were proposed.

Effects of physicochemical properties and co-existing zinc agrochemicals on the uptake and phytotoxicity of PFOA and GenX in lettuce.

Even though the potential toxicity and treatment methods for per- and polyfluoroalkyl substances (PFAS) have attracted extensive attention, the plant uptake and accumulation of PFAS in edible plant tissues as a potential pathway for human exposure received little attention. Our study in a hydroponic system demonstrated that perfluorooctanoic acid (PFOA) and its replacing compound, 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy) propanoic acid (GenX) displayed markedly different patterns of plant uptake and accumulation. For example, the root concentration factor (RCF) of PFOA in lettuce is almost five times of that of GenX while the translocation factor (TF) of GenX is about 66.7% higher than that for PFOA. The co-presence of zinc amendments affected the phyto-effect of these two compounds and their accumulation in plant tissues, and the net effect on their plant accumulation depended on both the properties of Zn amendments and PFAS. Zinc oxide nanoparticles (ZnONPs) at 100 mg/L did not affect the uptake of PFOA in either lettuce roots or shoots; however, Zn2+ at the same concentration significantly increased PFOA accumulation in both tissues. In contrast, both Zn amendments significantly lowered the accumulation of GenX in lettuce roots, but only ZnONPs significantly hindered the GenX accumulation in lettuce shoots. The co-exposure to ZnONPs and PFOA/GenX resulted in lower oxidative stress than the plants exposed to PFOA or GenX alone. However, both zinc agrochemicals with or without PFAS led to lower root dry biomass. The results shed light on the property-dependent plant uptake of PFAS and the potential impact of co-existing nanoagrochemicals and their dissolved ions on plant uptake of PFOA and GenX.

Six complex microbial inoculants for removing ammonia nitrogen from waters.

To determine the effect of microbial inoculants on the removal of ammonia nitrogen (NH4 + -N), six different complex microbial inoculants were studied. In this study, their effectiveness on NH4 + -N removal was compared, and their microbial community composition was determined. High-throughput sequencing results showed that Proteobacteria and Firmicutes were the dominant phyla in six samples. Before the reaction, Bacillus, Cyanobacteria, and Mitochondria genera were the dominant genera. The dominant genera were significantly different after the reaction with the addition of bacterial agents. The six water samples were Massilia, Escherichia-Shigella, Brevibacillus, Mitsuaria, Bacillus, and Ralstonia. Among the six complex microbial inoculants, "Gandu nitrifying bacteria (NR4 )" have the best removal effect on NH4 + -N. In addition, the removal effect of six different bacterial agents on chemical oxygen demand (COD) was compared. The results showed that "Bilaiqing ammonia nitrogen removal bacteria agent (NR5 )" has the best removal effect on COD. Single-factor experiments suggested that the optimal conditions for NR4 bacteria were pH 7, 30°C, 1.0 g/L of bacterial agent dosage and a wide range of NH4 + -N from 30 to 300 mg/L. PRACTITIONER POINTS: The nitrogen removal effects of six different microbial agents were compared. High-throughput sequencing provides important insights into the study of ammonia nitrogen removal by microbial communities. Analysis of six different complex bacterial agents by high-throughput sequencing. The relative abundance of microorganisms is not proportional to the ability to remove NH4 + -N Good application effect in urban landscape water body.

Interaction of peracetic acid with chromium(III): Understanding degradation of coexisting organic pollutants in water.

Peracetic acid (PAA, CH3C(O)OOH) has gained significant attention for its use in wastewater disinfection. Wastewater usually contains both metal ions and organic pollutants and understanding reactions after adding PAA to such contaminated water is needed. This paper presents results regarding the effect of interactions between chromium(III) (Cr(III)) and PAA on the degradation of selected pharmaceuticals, mainly trimethoprim (TMP). The degradation of pharmaceuticals by PAA, PAA-Cr(III), and H2O2-Cr(III) under different conditions was examined (pH = 6.0-10.0 and molar ratios of PAA to Cr(III)). The degradation rate of TMP by PAA-Cr(III) was greater than by PAA and H2O2-Cr(III) under alkaline conditions. Degradation studies using quenching agents and probing molecules, and spectroscopic measurements (UV-visible and electron paramagnetic resonance) suggest •OH as the major radical species and Cr(IV)/Cr(V) as additional reactive species. The oxidized products of TMP by PAA-Cr(III) were identified and possible pathways proposed. Degradation of other pharmaceuticals having different molecular structures by PAA-Cr(III) and H2O2-Cr(III) systems were also investigated. Most of the pharmaceuticals degraded at faster rates by PAA-Cr(III) and H2O2-Cr(III) than by PAA alone, suggesting that co-present metal ions may play a significant role in PAA oxidation in water treatment.

Oxidation of micropollutants by visible light active graphitic carbon nitride and ferrate(VI): Delineating the role of surface delocalized electrons.

The treatment of recalcitrant micropollutants in water remains challenging. Ferrate(VI) (FeVIO42-, Fe(VI)) has emerged as a green oxidant to oxidize organic molecules, however, its reactivity with recalcitrant micropollutants are sluggish. Our results demonstrate enhanced oxidation of carbamazepine (CBZ) by three types of visible light-responsive graphitic carbon nitride (g-C3N4) photocatalyst in absence and presence of ferrate(VI) (FeVIO42-, Fe(VI)) under mild alkaline conditions. The g-C3N4 photocatalysts were prepared by thermal process using urea, thiourea, and melamine and were named as CN-U, CN-T, and CN-M, respectively. The degradation efficiency of CBZ, in both visible light-g-C3N4 and visible light-g-C3N4-FeVIO42- systems followed the order of CN-U > CN-T > CN-M. The mechanisms for this trend was elucidated by measuring physiochemical properties of the microstructures with various surface and analytical techniques. Results suggest the dominating role of specific surface area and surface delocalized electrons of microstructures in degrading CBZ. Crystallinity, morphology, and surface functional groups may not directly associate with CBZ degradation. The CN-U has higher specific surface area and surface delocalized electrons than CN-T and CN-M and therefore the highest degradation efficiency of CBZ. The surface electrons likely generated O2●- and 1O2 in the visible light-g-C3N4 system. The additional oxidants, FeV and FeIV in the visible light-g-C3N4- FeVIO42- system led to higher degradation efficiency than the visible light-g-C3N4 system. Results suggest that the surfaces of g-C3N4 may be prepared preferentially with high levels of delocalized electrons at the surface of microstructures to enhance degradation of micropollutants.

Integrated Photocatalytic Reduction and Oxidation of Perfluorooctanoic Acid by Metal-Organic Frameworks: Key Insights into the Degradation Mechanisms.

The high porosity and tunability of metal-organic frameworks (MOFs) have made them an appealing group of materials for environmental applications. However, their potential in the photocatalytic degradation of per- and polyfluoroalkyl substances (PFAS) has been rarely investigated. Hereby, we demonstrate that over 98.9% of perfluorooctanoic acid (PFOA) was degraded by MIL-125-NH2, a titanium-based MOF, in 24 h under Hg-lamp irradiation. The MOF maintained its structural integrity and porosity after three cycles, as indicated by its crystal structure, surface area, and pore size distribution. Based on the experimental results and density functional theory (DFT) calculations, a detailed reaction mechanism of the chain-shortening and H/F exchange pathways in hydrated electron (eaq-)-induced PFOA degradation were revealed. Significantly, we proposed that the coordinated contribution of eaq- and hydroxyl radical (•OH) is vital for chain-shortening, highlighting the importance of an integrated system capable of both reduction and oxidation for efficient PFAS degradation in water. Our results shed light on the development of effective and sustainable technologies for PFAS breakdown in the environment.

Adsorptive Structure and Mobility on Carbon Nanotube Exteriors Using Benzoic Acid as a Molecular Probe of Amphiphilic Water Contaminants.

Benzoic acid is the simplest aromatic carboxylic acid that is also a common water contaminant. Its structural and amphiphilic properties are shared by many other contaminants of concern. Based on a molecular dynamics study, this work reports the competitive adsorption of benzoic acid with water on the curved exteriors of carbon nanotubes of varying oxygen content. With the help of cylindrically approximated pair correlation functions, carboxyl-carboxyl associations were found to serve as an additional mechanism providing stability to the adsorbed benzoic acid on tube exteriors. These associations are secondary to the main aromatic-aromatic interactions during the adsorption process and therefore were not sufficient to establish the energy hierarchy at the adsorbed state with increase in surface oxygen content. The same mechanism was previously ascribed to the adsorption of the structurally similar but bulkier tannic acid. Both water and benzoic acid were organized into numerous mobility groups and a correspondence was established between species residence time and the average translation time taken to escape the tube vicinity. Vigorous exchange of water molecules among the first adsorption shell, the second adsorption shell, and the immediate vicinity radially outside was estimated to take place within a short time of about 10 ps.

Reactivity of nitrogen species with inorganic and organic compounds in water.

Many studies on the reactive nitrogen species (RNS, ●NO2, ●NO and ●NH2) with pollutants in water have been performed to understand the abatement of inorganic and organic compounds by these species, and the mechanisms of the formation of oxidative transformation products, especially nitrogenous oxidized byproducts. In this review, approaches to generate RNS in aqueous solution is first presented, followed by a summary of their reactivity with a wide range of compounds. The second-order rate constants (k, M-1 s-1) for the reactivity of ●NO2 and ●NO with a wide range of inorganic radical and nonradical species were correlated with thermodynamic one-electron oxidation potentials (E0). The positive correlation between log(k) versus E0 suggests one-electron transfer reactions. The Hammett-type correlations were developed for the reactions of ●NO2 and ●NH2 with organic compounds, using the unsubstituted benzene as a reference molecule (i.e., Σσo,p,m = 0) to calculate Σσo,p,m = σo + σp + σm for each organic molecule. Linear negative correlations of log(k) with Σσo,p,m were obtained for both ●NO2 and ●NH2, suggesting electrophilic substitution mechanism. The correlations presented herein may assist in eliminating organic micropollutants in water treatment and reuse processes.

Zinc Fertilizers Modified the Formation and Properties of Iron Plaque and Arsenic Accumulation in Rice (Oryza sativa L.) in a Life Cycle Study.

This study examined the effect of three forms of zinc fertilizers on arsenic (As) accumulation and speciation in rice tissues over the life cycle of this cereal crop in a paddy soil. The formation and properties of iron plaque on rice roots at the maximum tillering stage and the mature stage were also determined. Elevated As at 5 mg/kg markedly lowered the rice yield by 86%; however, 100 mg/kg Zn fertilizers significantly increased the rice yield by 354-686%, regardless of the Zn form. Interestingly, only Zn2+ significantly lowered the total As in rice grains by 17% to 3.5 mg/kg and As(III) by 64% to around 0.5 mg/kg. Zinc amendments substantially hindered and, in the case of zinc oxide bulk particles (ZnOBPs), fully prevented the crystallization of iron oxides (Fe3O4 and Fe2O3) and silicon oxide (SiO2) and altered the composition of iron plaques on rice roots. SiO2 was first reported to be a significant component of iron plaque. Overall, ZnOBPs, ZnO nanoparticles, and Zn2+ displayed significant yet distinctive effects on the properties of iron plaque and As accumulation in rice grains, providing a fresh perspective on the potentially unintended consequences of different Zn fertilizers on food safety.