Pseudomonas fluorescens with Nitrogen-Fixing Function Facilitates Nitrogen Recovery in Reclaimed Coal Mining Soils.

Coal mining has caused significant soil nitrogen loss in mining areas, limiting reclamation and reuse in agriculture. This article studies the effects of organic fertilizer, inorganic fertilizer, and the combined application of Pseudomonas fluorescens with the ability of nitrogen fixation on soil nitrogen accumulation and composition in the reclamation area of the Tunlan Coal Mine from 2016 to 2022 under the conditions of equal nitrogen application, providing a scientific basis for microbial fertilization and the rapid increase in nitrogen content in the reclaimed soil of mining areas. The results showed that as the reclamation time increased, the nitrogen content and the composition and structure of the soil treated with fertilization rapidly evolved toward normal farmland soil. The soil nitrogen content increased most rapidly in the presence of added P. fluorescens + organic fertilizer (MB). Compared to other treatments (inorganic fertilizer (CF), organic fertilizer (M), and P. fluorescens + inorganic fertilizer (CFB)), MB increased total nitrogen (TN) to normal farmland soil levels 1-3 years earlier. The comprehensive scores of MB and CFB on the two principal components increased by 1.58 and 0.79 compared to those of M and CF treatments, respectively. This indicates that the combination of P. fluorescens and organic fertilizer improves soil nitrogen accumulation more effectively than the combination of P. fluorescens and inorganic fertilizer. In addition, the application of P. fluorescens increases the content of unknown nitrogen (UN) in acid-hydrolysable nitrogen (AHN) and decreases the content of amino acid nitrogen (AAN) and ammonia nitrogen (AN). However, there was no significant effect on the content of ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3--N) in soil-mineralized nitrogen (SMN). When combined with inorganic fertilizer, the contribution of SMN to TN increased by 14.78%, while when combined with organic fertilizer, the contribution of AHN to TN increased by 44.77%. In summary, the use of P. fluorescens is beneficial for nitrogen recovery in the reclaimed soil of coal-mining areas. The optimal fertilization method under the experimental conditions is the combination of P. fluorescens and organic fertilizer.

Response of Soil Bacterial Diversity, Predicted Functions and Co-Occurrence Patterns to Nanoceria and Ionic Cerium Exposure.

Release of nanoceria (nCeO2) into the environment has caused much concern about its potential toxicity, which still remains poorly understood for soil microorganisms. In this study, nanoceria and cerium (III) nitrate at different doses (10, 100 and 500 mg/kg) were applied to bok choy (Brassica rapa subsp. chinensis), grown in potting soil, to investigate the responses of soil bacterial communities to nanoceria (NC) and ionic cerium (IC) applications. The results showed that bacterial richness was slightly increased in all cerium treatments relative to the negative control without cerium amendment (CK), but a significant increase was only found in IC500. The patterns of bacterial community composition, predicted functions and phenotypes of all NC treatments were significantly differentiated from IC and CK treatments, which was correlated with the contents of cerium, available potassium and phosphorus in soil. The co-occurrence network of bacterial taxa was more complex after exposure to ionic cerium than to nanoceria. The keystone taxa of the two networks were entirely different. Predicted functions analysis found that anaerobic and Gram-negative bacteria were enriched under nanoceria exposure. Our study implies that Proteobacteria and nitrifying bacteria were significantly enriched after exposure to nanoceria and could be potential biomarkers of soil environmental perturbation from nanoceria exposure.

Contribution, Composition, and Structure of EPS by In Vivo Exposure to Elucidate the Mechanisms of Nanoparticle-Enhanced Bioremediation to Metals.

Bacterial extracellular polymeric substances (EPS) have been recently found to contribute most for metal removal in nanoenhanced bioremediation. However, the mechanism by which NPs affect EPS-metal interactions is not fully known. Here, Halomonas sp. was employed to explore the role of EPS after in vivo exposure to Cd/Pb and polyvinylpyrrolidone (PVP) coated iron oxide nanoparticles (IONPs, 20 mg L-1) for 72 h. Cd-IONPs produced the highest concentrations of EPS proteins (136.3 mg L-1), while Cd induced the most production of polysaccharides (241.0 mg L-1). IONPs increased protein/polysaccharides ratio from 0.2 (Cd) to 1.2 (Cd-IONPs). The increased protein favors the formation of protein coronas on IONPs surface, which would promote Cd adsorption during NP-metal-EPS interaction. FTIR analysis indicated that the coexistence of Cd and IONPs interacted with proteins more strongly than with polysaccharides. Glycosyl monomer analyses suggested mannose and glucose as target sugars for EPS complexation with metals, and IONPs reduced metal-induced changes in monosaccharide profiles. Protein secondary structures changed in all treatments, but we could not distinguish stresses induced by metals from those by IONPs. These findings provide greater understanding of the role of EPS in NP-metal-EPS interaction, providing a better underpinning knowledge for the application of NP-enhanced bioremediation.

Use of single particle ICP-MS to estimate silver nanoparticle penetration through baby porcine mucosa.

Children are potentially exposed to products that contain nanoparticles (NPs). In particular, silver NPs are commonly present both in products used by and around children, primarily due to their antibacterial properties. However, very few data are available regarding the ability of silver NPs to penetrate through the oral mucosa in children. In the present work, we used baby porcine buccal mucosa mounted on vertical Franz diffusion cells, as an in vitro model to investigate penetration of silver NPs (19 ± 5 nm). Permeability experiments were performed using pristine physiologically-relevant saline solution in the receiver chamber and known concentrations of NPs or ions in the donor chamber; conditions mimicked the in vivo physiological pH conditions. After physicochemical characterization of silver nanoparticles dispersed in physiological solution, we evaluated the passage of ions and NPs through the mucosa, using single particle inductively coupled plasma mass spectrometry. A flux of 4.1 ± 1.7 ng cm-2 min-1 and a lag time of 159 ± 17 min were observed through mucosa exposed to silver nanoparticles. The latter suggests nanoparticle penetration through the baby porcine mucosa and release Ag+ ions in the receptor fluid, as confirmed by computational model. Due to physiological similarity between human and pig membranes it is reasonable to assume that a trans-oral mucosa penetration could occur in children upon contact with silver nanoparticles.

Characterization, bio-uptake and toxicity of polymer-coated silver nanoparticles and their interaction with human peripheral blood mononuclear cells.

Silver nanoparticles (AgNPs) are widely used in medical applications due to their antibacterial and antiviral properties. Despite the extensive study of AgNPs, their toxicity and their effect on human health is poorly understood, as a result of issues such as poor control of NP properties and lack of proper characterization. The aim of this study was to investigate the combined characterization, bio-uptake, and toxicity of well-characterized polyvinylpyrrolidone (PVP)-coated AgNPs in exposure media during exposure time using primary human cells (peripheral blood mononuclear cells (PBMCs)). AgNPs were synthesized in-house and characterized using a multimethod approach. Results indicated the transformation of NPs in RPMI medium with a change in size and polydispersity over 24 h of exposure due to dissolution and reprecipitation. No aggregation of NPs was observed in the RPMI medium over the exposure time (24 h). A dose-dependent relationship between PBMC uptake and Ag concentration was detected for both AgNP and AgNO3 treatment. There was approximately a two-fold increase in cellular Ag uptake in the AgNO3 vs the NP treatment. Cytotoxicity, using LDH and MTS assays and based on exposure concentrations was not significantly different when comparing NPs and Ag ions. Based on differential uptake, AgNPs were more toxic after normalizing toxicity to the amount of cellular Ag uptake. Our data highlights the importance of correct synthesis, characterization, and study of transformations to obtain a better understanding of NP uptake and toxicity. Statistical analysis indicated that there might be an individual variability in response to NPs, although more research is required.

How Do African-American Community Members' Perceptions About Environmental Risks of Breast Cancer Compare with the Current State of the Science?

African-American (AA) women experience higher mortality from breast cancer than any other racial group. Understanding community-held perceptions of environmental contaminants as risk factors for breast cancer can inform the development of tailored prevention and education efforts for improve health outcomes. Six focus groups were conducted with AA participants in two counties in South Carolina, and themes were identified using open and axial coding. Perceived environmental risks for breast cancer most frequently discussed by participants were compared to findings from published systematic reviews. Frequently discussed environmental risk factors by participants were deodorants containing aluminum, plastics, pesticides, and air and water pollution. While perceptions of aluminum and air pollution as risk factors did not align with the state of the science, perceived risk factors of chemicals in plastics and pesticides were found to be in alignment. There is some congruence between perceived environmental risks for breast cancer within the AA community and the current state of the science; however, there is a need to communicate information that reflects current science regarding commonly held misconceptions. Development of evidence-based, clear, and culturally appropriate messaging that reflects the current state of the science is warranted.

"Talk About Cancer and Build Healthy Communities": How Visuals Are Starting the Conversation About Breast Cancer Within African-American Communities.

African-American (AA) women are at higher risk of breast cancer mortality than women of other races. Factors influencing breast cancer risk, including exogenous environmental exposures, and debate around timing of exposure and dose-response relationship, can cause misunderstanding. Collaboration with priority populations encourages culturally relevant health messaging that imparts source reliability, influences message adoption, and improves understanding. Through six focus groups with AA individuals in rural and urban counties in the southeastern United States, this study used a community-engaged participatory approach to design an innovative visual tool for disseminating breast cancer information. Results demonstrated that participants were generally aware of environmental breast cancer risks and were willing to share new knowledge with families and community members. Recommended communication channels included pastors, healthcare providers, social media, and the Internet. Participants agreed that a collaboratively designed visual tool serves as a tangible, focused "conversation starter" to promote community prevention and education efforts.

Health impacts of environmental contamination of micro- and nanoplastics: a review.

Plastics are extensively used in our daily life. However, a significant amount of plastic waste is discharged to the environment directly or via improper reuse or recycling. Degradation of plastic waste generates micro- or nano-sized plastic particles that are defined as micro- or nanoplastics (MNPs). Microplastics (MPs) are plastic particles with a diameter less than 5 mm, while nanoplastics (NPs) range in diameter from 1 to 100 or 1000 nm. In the current review, we first briefly summarized the environmental contamination of MNPs and then discussed their health impacts based on existing MNP research. Our review indicates that MNPs can be detected in both marine and terrestrial ecosystems worldwide and be ingested and accumulated by animals along the food chain. Evidence has suggested the harmful health impacts of MNPs on marine and freshwater animals. Recent studies found MPs in human stool samples, suggesting that humans are exposed to MPs through food and/or drinking water. However, the effect of MNPs on human health is scarcely researched. In addition to the MNPs themselves, these tiny plastic particles can release plastic additives and/or adsorb other environmental chemicals, many of which have been shown to exhibit endocrine disrupting and other toxic effects. In summary, we conclude that more studies are necessary to provide a comprehensive understanding of MNP pollution hazards and also provide a basis for the subsequent pollution management and control.

Meconium identifies high levels of metals in newborns from a mining community in the U.S.

BACKGROUND: This pilot study was conducted to determine if we could identify intrauterine exposure to metals in meconium, as a measure of exposure for mother-child pairs living in proximity to a mining operation. OBJECTIVES: We used meconium as a means to measure metal exposure in utero. We set out to quantify the exposure to selected metals that are currently being mined and also are found in the Superfund site in Butte, Montana, and to compare it to that of Columbia, South Carolina, US, where mining is not occurring. METHODS: This cross-sectional study was conducted between May and November 2018. We received Institutional Review Board approval and we consented women following the birth of their newborns, and collected meconium within 24 h of birth, without any identifiers. Each laboratory used the same protocol for collection, transport, and storage; and the same laboratory protocol was used for the analysis of all samples. Samples were digested using standard acid/peroxide digestion methods and measured by inductively coupled plasma mass spectroscopy. RESULTS: We collected meconium specimens from 17 infants in Columbia, South Carolina and 15 infants in Butte, Montana. The concentrations found in Columbia were in the low µg kg-1 range (or less) and were similar to the low levels that have been identified in other studies of meconium. The magnitude of the differences in concentrations found in Butte compared to Columbia was 1792 times higher for Cu, 1650 times higher for Mn, and 1883 times higher for Zn. CONCLUSION: Using meconium to measure exposure of newborns has implications for risk assessment in a mining-exposed population. This approach was inexpensive and thorough. The magnitude of the differences in the metal levels identified from the two study sites suggests there is an urgent need for further research to learn if there are health consequences to these highly exposed infants.

Three-layered silver nanoparticles to trace dissolution and association to a green alga.

Core-shell silver nanoparticles (NPs) consisting of an inner Ag core and successive layers of Au and Ag (Ag@Au@Ag) were used to measure the simultaneous association of Ag NPs and ionic Ag by the green alga Chlamydomonas (C.) reinhardtii. Dissolution of the inner Ag core was prevented by a gold (Au) layer, while the outer Ag layer was free to dissolve. In short-term experiments, we exposed C. reinhardtii to a range of environmentally realistic Ag concentrations added as AgNO3 or as NPs. Results provide three lines of evidence for the greater cell-association of NPs compared to dissolved Ag over the concentration range tested, assuming that cell-association comprises both uptake and adsorption. First, the cell-association rate constants (kuw) for total Ag (AgNP+D), NPs (AgNP) and AuNP were similar and 2.2-fold higher than the one from AgD exposure, suggesting predominant association of the particles over the dissolved form. Second, model calculations based on Ag fluxes suggested that only 6-33% of algal burden was from AgD. Third, the significantly lower AgNP/Au ratio measured with the algae after exposure (2.1 ± 0.1) compared to the AgNP/Au ratio of the NPs in the media (2.47 ± 0.05) suggests cell-association of NPs depleted in Ag. Core-shell NPs provide an innovative tool to understand NP behavior and to directly delineate Ag accumulation from ion and NPs in aquatic systems.

Size and coating of engineered silver nanoparticles determine their ability to growth-independently inhibit aflatoxin biosynthesis in Aspergillus parasiticus.

Recent studies from our laboratory indicate that engineered silver nanoparticles can inhibit aflatoxin biosynthesis even at concentrations at which they do not demonstrate antifungal activities on the aflatoxin-producing fungus. Whether such inhibition can be modified by altering the nanoparticles' physical properties remains unclear. In this study, we demonstrate that three differently sized citrated-coated silver nanoparticles denoted here as NP1, NP2, and NP3 (where, sizes of NP1 < NP2 < NP3) inhibit aflatoxin biosynthesis at different effective doses in Aspergillus parasiticus, the plant pathogenic filamentous fungus. Recapping NP2 with polyvinylpyrrolidone coating (denoted here as NP2p) also altered its ability to inhibit aflatoxin production. Dose-response experiments with NP concentrations ranging from 10 to 100 ng mL-1 indicated a non-monotonic relationship between aflatoxin inhibition and NP concentration. The maximum inhibitory concentrations differed between the NP types. NP1 demonstrated maximum inhibition at 25 ng mL-1. Both NP2 and NP3 showed maximum inhibition at 50 ng mL-1, although NP2 resulted in a significantly higher inhibition than NP3. While both NP2 and NP2p demonstrated greater aflatoxin inhibition than NP1 and NP3, NP2p inhibited aflatoxin over a significantly wider concentration range as compared to NP2. Our results, therefore, suggest that nano-fungal interactions can be regulated by altering certain NP physical properties. This concept can be used to design NPs for mycotoxin prevention optimally.

A Comparison between the Oil Removal Capacity of Polymer-Coated Magnetic Nanoparticles in Natural and Synthetic Environmental Samples.

Oil spills can have dramatic impacts on the environment. The limitations of current oil remediation techniques have inspired researchers to study the application of nanotechnology for oil cleanup. Previously, we reported essentially 100% removal of a reference MC252 oil using polyvinylpyrrolidone (PVP)-coated iron oxide nanoparticles (NPs) from oil-water mixtures under a wide range of environmentally relevant conditions. Our previous results showed that in the synthetic water samples, the concentration of cations and natural organic macromolecules (NOM) can significantly affect the oil removal efficiency of NPs. Here, we studied the application of these NPs for oil removal from natural freshwater samples and compared the results with the synthetic water samples with the same concentrations of major ions and NOM. For both natural and synthetic samples, concentrations of NOM, calcium, and magnesium were positively correlated with oil removal ( p-value <0.05). NPs show an average of 30% higher oil removal efficiency from natural samples compared to the synthetic samples. Using up to 50 ppm of NP, essentially 100% oil removal was observed under most conditions specially hardwater samples (initial 0.15 g L-1 oil concentration). Results show that these NPs are a facile and reliable technique for removing oil under realistic conditions.

"For lack of knowledge, our people will perish": Using focus group methodology to explore African-American communities' perceptions of breast cancer and the environment.

Among women living in the United States, breast cancer is the second leading cause of cancer death. Disproportionate racial disparities in breast cancer exist, with African American (AA) women consistently having the highest rates of breast cancer related mortality despite lower incidence. This study attends to the Institute of Medicine's (IOM) call to action recommending the identification of effective strategies for communicating accurate and reliable breast cancer risk information to diverse audiences. Using focus group methodology, this study explores how AAs perceive and decipher information related to breast cancer and its relationship to their environment. Six focus groups were conducted. The sample (n = 50) was African American, 98% female, with an average age of 50.1 years. The focus group protocol consisted of open-ended questions designed to elicit information about participants' perceptions of their environment and its link to breast cancer. Focus groups were audio recorded and professionally transcribed. Analysis of the focus group transcripts revealed themes pertaining to these categories: (1) general knowledge and beliefs about breast cancer, (2) perceived environmental risks factors for breast cancer, (3) importance of seeking knowledge about breast cancer and the environment, and (4) recommended communication strategies. The emergent themes reflect the knowledge participants possessed about breast cancer and environmental risk factors, in addition to concerns about the importance of possessing accurate information, and how culturally appropriate health communication strategies can be used to disseminate breast cancer knowledge in the community. Findings from this study can be used for culturally appropriate communication about breast cancer and the environment with AA communities.

A Comprehensive Analysis of How Environmental Risks of Breast Cancer are Portrayed on the Internet.

BACKGROUND: Effective online communication about the environmental risk factors of breast cancer is essential because of the multitude of environmental exposures and debate regarding the conclusiveness of scientific evidence. PURPOSE: The aim of this study was to assess the content, readability, and cultural sensitivity of online resources focused on the environmental risks factors of breast cancer. METHODS: A purposive sample of webpages focused on environmental risk factors of breast cancer was obtained through a Google search using 17 search terms. Using nonparametric statistics, we assessed the content, readability, and cultural appropriateness of 235 webpages. RESULTS: Eighty-two percent of webpages referred to research studies in their content. For the majority of sites, readability was at a high-school reading grade level. Webpages were not explicitly intended for specific racial/ethnic groups. DISCUSSION: Technical language and non-culturally specific messages may hinder users' attention to and comprehension of online breast cancer information. Additional research is needed to examine in-depth the accuracy of this online content. TRANSLATION TO HEALTH EDUCATION PRACTICE: Findings suggest that collaborations between scientists, health educators, website designers/media professionals, and the community will be critical to the delivery of accurate, up-to-date, plain-language, and culturally sensitive information about breast cancer and the environment.

Nanomaterials in the environment: Behavior, fate, bioavailability, and effects-An updated review.

The present review covers developments in studies of nanomaterials (NMs) in the environment since our much cited review in 2008. We discuss novel insights into fate and behavior, metrology, transformations, bioavailability, toxicity mechanisms, and environmental impacts, with a focus on terrestrial and aquatic systems. Overall, the findings were that: 1) despite substantial developments, critical gaps remain, in large part due to the lack of analytical, modeling, and field capabilities, and also due to the breadth and complexity of the area; 2) a key knowledge gap is the lack of data on environmental concentrations and dosimetry generally; 3) substantial evidence shows that there are nanospecific effects (different from the effects of both ions and larger particles) on the environment in terms of fate, bioavailability, and toxicity, but this is not consistent for all NMs, species, and relevant processes; 4) a paradigm is emerging that NMs are less toxic than equivalent dissolved materials but more toxic than the corresponding bulk materials; and 5) translation of incompletely understood science into regulation and policy continues to be challenging. There is a developing consensus that NMs may pose a relatively low environmental risk, but because of uncertainty and lack of data in many areas, definitive conclusions cannot be drawn. In addition, this emerging consensus will likely change rapidly with qualitative changes in the technology and increased future discharges. Environ Toxicol Chem 2018;37:2029-2063. © 2018 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

A rapid approach for measuring silver nanoparticle concentration and dissolution in seawater by UV-Vis.

Detection and quantification of engineered nanoparticles (NPs) in environmental systems is challenging and requires sophisticated analytical equipment. Furthermore, dissolution is an important environmental transformation process for silver nanoparticles (AgNPs) which affects the size, speciation and concentration of AgNPs in natural water systems. Herein, we present a simple approach for the detection, quantification and measurement of dissolution of PVP-coated AgNPs (PVP-AgNPs) based on monitoring their optical properties (extinction spectra) using UV-vis spectroscopy. The dependence of PVP-AgNPs extinction coefficient (ɛ) and maximum absorbance wavelength (λmax) on NP size was experimentally determined. The concentration, size, and extinction spectra of PVP-AgNPs were characterized during dissolution in 30ppt synthetic seawater. AgNPs concentration was determined as the difference between the total and dissolved Ag concentrations measured by inductively coupled plasma-mass spectroscopy (ICP-MS); extinction spectra of PVP-AgNPs were monitored by UV-vis; and size evolution was monitored by atomic force microscopy (AFM) over a period of 96h. Empirical equations for the dependence of maximum absorbance wavelength (λmax) and extinction coefficient (ɛ) on NP size were derived. These empirical formulas were then used to calculate the size and concentration of PVP-AgNPs, and dissolved Ag concentration released from PVP-AgNPs in synthetic seawater at variable particle concentrations (i.e. 25-1500µgL-1) and in natural seawater at particle concentration of 100µgL-1. These results suggest that UV-vis can be used as an easy and quick approach for detection and quantification (size and concentration) of sterically stabilized PVP-AgNPs from their extinction spectra. This approach can also be used to monitor the release of Ag from PVP-AgNPs and the concurrent NP size change. Finally, in seawater, AgNPs dissolve faster and to a higher extent with the decrease in NP concentration toward environmentally relevant concentrations.

Seasonal variability of natural water chemistry affects the fate and behaviour of silver nanoparticles.

Understanding the environmental behaviour of nanoparticles (NPs) after release into aquatic systems is essential to predict the environmental implications of nanotechnology. Silver nanoparticles (AgNPs) represent a major class of engineered NPs with a significant potential for environmental impact. Therefore, investigating their transformations in natural waters will help predict their long term environmental fate and behaviour. AgNPs were characterized in natural lake water collected seasonally from the same freshwater source, using column microcosms to assess their behaviour and transport at different depths. Building on our previous work using similar systems with synthetic waters, the influence of water chemistry and NP surface modifications on colloidal stability and dissolution in natural lake water over time was investigated. A simple sedimentation-diffusion model parameterized by the particle properties and total Ag concentration was successfully used to understand AgNPs transport behaviour. PVP coated AgNPs remained colloidally stable, with their transport in the water column dominated by diffusion, and exhibited no significant or substantial changes in data or model parameters for different seasons. Citrate coated AgNPs were susceptible to rapid aggregation, sedimentation, dissolution and reprecipitation; their transport in the water column was determined by both diffusion and sedimentation.

Citrate-Coated Silver Nanoparticles Growth-Independently Inhibit Aflatoxin Synthesis in Aspergillus parasiticus.

Manufactured silver nanoparticles (Ag NPs) have long been used as antimicrobials. However, little is known about how these NPs affect fungal cell functions. While multiple previous studies reveal that Ag NPs inhibit secondary metabolite syntheses in several mycotoxin producing filamentous fungi, these effects are associated with growth repression and hence need sublethal to lethal NP doses, which besides stopping fungal growth, can potentially accumulate in the environment. Here we demonstrate that citrate-coated Ag NPs of size 20 nm, when applied at a selected nonlethal dose, can result in a >2 fold inhibition of biosynthesis of the carcinogenic mycotoxin and secondary metabolite, aflatoxin B1 in the filamentous fungus and an important plant pathogen, Aspergillus parasiticus, without inhibiting fungal growth. We also show that the observed inhibition was not due to Ag ions, but was specifically associated with the mycelial uptake of Ag NPs. The NP exposure resulted in a significant decrease in transcript levels of five aflatoxin genes and at least two key global regulators of secondary metabolism, laeA and veA, with a concomitant reduction of total reactive oxygen species (ROS). Finally, the depletion of Ag NPs in the growth medium allowed the fungus to regain completely its ability of aflatoxin biosynthesis. Our results therefore demonstrate the feasibility of Ag NPs to inhibit fungal secondary metabolism at nonlethal concentrations, hence providing a novel starting point for discovery of custom designed engineered nanoparticles that can efficiently prevent mycotoxins with minimal risk to health and environment.

A High Resolution Study of Dynamic Changes of Ce2O3 and CeO2 Nanoparticles in Complex Environmental Media.

Ceria nanoparticles (NPs) rapidly and easily cycle between Ce(III) and Ce(IV) oxidation states, making them prime candidates for commercial and other applications. Increased commercial use has resulted in increased discharge to the environment and increased associated risk. Once in complex media such as environmental waters or toxicology exposure media, the same redox transformations can occur, causing altered behavior and effects compared to the pristine NPs. This study used high resolution scanning transmission electron microscopy and electron energy loss spectroscopy to investigate changes in structure and oxidation state of small, polymer-coated ceria suspensions in complex media. NPs initially in either the III or IV oxidation states, but otherwise identical, were used. Ce(IV) NPs were changed to mixed (III, IV) NPs at high ionic strengths, while the presence of natural organic macromolecules (NOM) stabilized the oxidation state and increased crystallinity. The Ce(III) NPs remained as Ce(III) at high ionic strengths, but were modified by the presence of NOM, causing reduced crystallinity and degradation of the NPs. Subtle changes to NP properties upon addition to environmental or ecotoxicology media suggest that there may be small but important effects on fate and effects of NPs compared to their pristine form.

Nanosilver inhibits nitrification and reduces ammonia-oxidising bacterial but not archaeal amoA gene abundance in estuarine sediments.

Silver nanoparticles (AgNPs) enter estuaries via wastewater treatment effluents, where they can inhibit microorganisms, because of their antimicrobial properties. Ammonia-oxidising bacteria (AOB) and archaea (AOA) are involved in the first step of nitrification and are important to ecosystem function, especially where effluent discharge results in high nitrogen inputs. Here, we investigated the effect of a pulse addition of AgNPs on AOB and AOA ammonia monooxygenase (amoA) gene abundances and benthic nitrification potential rates (NPR) in low-salinity and mesohaline estuarine sediments. Whilst exposure to 0.5 mg L-1 AgNPs had no significant effect on amoA gene abundances or NPR, 50 mg L-1 AgNPs significantly decreased AOB amoA gene abundance (up to 76% over 14 days), and significantly decreased NPR by 20-fold in low-salinity sediments and by twofold in mesohaline sediments, after one day. AgNP behaviour differed between sites, whereby greater aggregation occurred in mesohaline waters (possibly due to higher salinity), which may have reduced toxicity. In conclusion, AgNPs have the potential to reduce ammonia oxidation in estuarine sediments, particularly where AgNPs accumulate over time and reach high concentrations. This could lead to long-term risks to nitrification, especially in polyhaline estuaries where ammonia-oxidation is largely driven by AOB.