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As anemerging contaminant,the antimicrobial agent silver nanoparticles (AgNPs) havebeen receiving considerable attention to determine theirpotential effects to aquatic ecosystems. However, estimates of aquatic consumer survivorship and other toxicological endpoints vary considerably amongexperiments, largely due to the environment in which the test takes place. Throughout this thesis I aim to understand whichnatural environmental variables impact toxicity to the common aquatic consumer Daphnia. I focus on the effectsof particulate matter as it mayplay a role in animal nutrition as well as interact with AgNPs. I exploreparticulate matter?seffect on survival in the complex matrices including other natural variables that could impact toxicity. I conduct a series of complimentary field and laboratorystudies to understand how particles impact AgNP toxicity and how those interactions vary within whole lake ecosystems. Using laboratory studies, I establish that algal particles mitigatethe toxic effects of AgNPs on Daphniasurvival through removing Ag from the water column and that phosphorusincreases this effect. Using wild Daphniaand lake water, I demonstratethe ability of particulate matterto mitigate toxicity in complex natural settings. It was also one of the major predictors of AgNP toxicity to Daphniaalong with dissolved organic carbon and daphnid seasonal health. Finally,usinga whole lake AgNP addition experiment, Idemonstrate that particles and AgNPs interact variably inthe lake. Silver from AgNPs binds to particles and is removed to the sediments through the actions of settling particleswithout impacting the dynamics of living communities. Overall,I amable to demonstrate that the natural components of lake ecosystems, especially particulate matter, are able to mitigate the effects of AgNPs in lake ecosystems to a point where they likely will be never pose a threat to the survivorship of aquatic consumers such as Daphnia. Keywords: Silver nanoparticles, Daphnia, ecotoxicity, whole lake experiment, phytoplankton communities, particulate matter, sedimentation.
The potential release of nanoparticles into aquatic environments is raising global concerns. As antimicrobials, silver nanoparticles (AgNPs) are among the most prominent form in use. Despite this, their fate, long-term toxicity, and ecological relevance have yet to be investigated largely under natural settings with seasonality and environmental complexity. To better understand the environmental significance, we released AgNPs into Lake 222 at the Experimental Lakes Area over two years. AgNPs remained suspended in the water column and were detected throughout the lake and in the lower food web. Total Ag concentrations ranged from below 0.07 to 18.9 ?g L-1 in lake water, and were highly dynamic seasonally both in the epilimnion and hypolimnion depending on the physical, chemical and biological conditions of the lake. Approximately 60% of the measured Ag mass in October was present in the sediment in 2014 and 50% in 2015 demonstrating relatively high sedimentation and removal from the water column. During winter months, Ag was largely absent in the water column under the ice. After ice melt and before summer stratification, Ag concentrations increased in the lake suggesting AgNPs may not be tightly bound to the sediment and are able re-enter the water column during spring mixing events. Despite temporal variation, total Ag was highly synchronous across spatial locations for both years, indicating rapid dispersal upon lake entry. When investigating AgNP sizes using spICPMS, size distributions were similar across spatial locations, with the 40-60 nm size class constituting approximately 60% of all particles iii identified. Large aggregates (>100 nm) and dissolved Ag were infrequently detected within the lake. Ag accumulated in the lower food web ranging from 0.27-16.82 ?g Ag mg C-1 in the bacterioplankton and 0.17-6.45 ?g Ag mg C-1 in algae (particulate fraction). Partial least squares models revealed the highest predictors of Ag accumulation were dissolved nutrients including DOC, TDN, TDP in bacterioplankton. Major predictors for particulate Ag included temperature, dissolved oxygen, and sampling date. The diversity of predictors among biological compartments emphasizes the importance of understanding the role of environmental complexity within the lower food web. Despite Ag accumulation we did not detect strong negative effects on the lake food web. An increase in particulate and bacterioplankton chlorophyll-a occurred after addition in contrast to reference lakes, which may indicate a hormetic response to low dose AgNP concentrations. Our findings provide the first whole-lake perspective regarding Ag fate and toxicity, suggesting small scale experiments may overestimate environmental responses. Keywords: Silver nanoparticles, ecotoxicity, whole-lake experiment, lower food web fate.
Anthropogenic particulate matter is an emerging form of environmental contaminate encompassing nanomaterials and microplastics. These human-made materials have renewed interest in colloid science and toxicology with the goal of answering two questions. (1) What processes affect the distribution of anthropogenic particulate matter in the environment? (2) Could anthropogenic particulate matter harm humans and/or the environment? It is difficult to answer these questions because the study of anthropogenic particulate matter exists between classical physics and chemistry, and concepts from both must be invoked to understand the processes that govern the fate and effects of these particles. As an example, I examined what unit is best used to express nanoparticle toxicity. Researchers typically express the dose of nanoparticles delivered to an organism as grams per liter, while the biochemically appropriate unit is moles. The use of the ‘gram per liter’ unit implies that 1 mole of a nanoparticles is equivalent to 1 mole of the dissolved particle material, rather than the number of particles or the active surface area of the particles, which may be appropriate measures of a mole of nanoparticles depending on mode of action. To determine which dosing unit is most appropriate, I performed the meta- analysis described in Chapter 2, which has been peer-reviewed and published in the journal NanoImpact. Through this work I discovered that units of surface area better reduced the heterogeneity of data for dissolvable particles, namely silver and zinc oxide tested on crustaceans, indicating that toxicity in these cases is dependent on surface reactions. However, no conclusion could be reached for non-dissolvable particles due to limited available data. The bigger takeaway from this work is that researchers have not been reporting sufficient meta-data to build a proper dataset, and more careful primary research is required. Research into the processes that govern the fate of anthropogenic particulate matter has shown that aggregation in aquatic systems and deposition in porous media are two of the driving factors of anthropogenic matter’s fate. Chapter 3 describes my effort to gain insight into aggregation. This chapter has been peer-reviewed and published in the journal ACS Earth and Space Chemistry. Briefly, I built a model to describe particle aggregation and disaggregation using statistical thermodynamics. This model describes the steady-state distribution of any two-particle system. I discovered that despite large concentration differences between anthropogenic particulate matter and natural particulate matter, anthropogenic particulate matter will not always be aggregated. In Chapter 4, I investigated deposition of particles using atomic force microscopy (AFM) and compared this to traditional column experiments. I used AFM to measure the probability a microplastic will deposit onto a surface if it contacts that surface. I found that the AFM method has a degree of variability due to choices made by the experimenter, but it can still be useful to probe deposition of microplastics on environmental surfaces as it allows qualitative comparisons which can inform hypotheses of the types of minerals that will matter to the transport of microplastics in the subsurface.
This comprehensive book covers the environmental issues concerning silver nanoparticles (AgNPs). Following an introduction to the history, properties and applications, the environmental concerns of AgNPs is discussed. In the second chapter, the separation, characterization and quantification of AgNPs in environment samples are described in detail. In the remaining parts of the book, the authors focus on the environmental processes and effects of AgNPs, with chapters on the pathway into environment, fate and transport, toxicological effects and mechanisms, as well as the environmental bioeffects and safety-assessment of AgNPs in the environment. This book is designed to describe current understanding of the environmental aspects of AgNPs. It provides a valuable resource to students and researchers in environmental science and technology, nanotechnology, toxicology, materials science and ecology; as well as to professionals involved in the production and consumption of AgNPs in various areas including catalysis, food products, textiles/fabrics, and medical products and devices. Jingfu Liu and Guibin Jiang are professors at State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences.
Many potential questions regarding the risks associated with the development and use of wide-ranging technologies enabled through engineered nanomaterials. For example, with over 600 consumer products available globally, what information exists that describes their risk to human health and the environment? What en- neering or use controls can be deployed to minimize the potential environmental health and safety impacts of nanomaterials throughout the manufacturing and product lifecycles? How can the potential environmental and health benefits of nanotechnology be realized and maximized? The idea for this book was conceived at the NATO Advanced Research Workshop (ARW) on “Nanomaterials: Environmental Risks and Benefits and Emerging Consumer Products. ” This meeting – held in Algarve, Portugal, in April 2008 – started with building a foundation to harmonize risks and benefits associated with nanomaterials to develop risk management approaches and policies. More than 70 experts, from 19 countries, in the fields of risk assessment, decision-analysis, and security discussed the current state-of-knowledge with regard to nanomaterial risk and benefits. The discussion focused on the adequacy of available risk assessment tools to guide nanomaterial applications in industry and risk governance. The workshop had five primary purposes: Describe the potential benefits of nanotechnology enabled commercial products. Identify and describe what is known about environmental and human health risks of nanomaterials and approaches to assess their safety. Assess the suitability of multicriteria decision analysis for reconciling the benefits and risks of nanotechnology.
This book is open access under a CC BY 4.0 license. This volume focuses on microscopic plastic debris, also referred to as microplastics, which have been detected in aquatic environments around the globe and have accordingly raised serious concerns. The book explores whether microplastics represent emerging contaminants in freshwater systems, an area that remains underrepresented to date. Given the complexity of the issue, the book covers the current state-of-research on microplastics in rivers and lakes, including analytical aspects, environmental concentrations and sources, modelling approaches, interactions with biota, and ecological implications. To provide a broader perspective, the book also discusses lessons learned from nanomaterials and the implications of plastic debris for regulation, politics, economy, and society. In a research field that is rapidly evolving, it offers a solid overview for environmental chemists, engineers, and toxicologists, as well as water managers and policy-makers.
This book focuses on successful application of microbial biotechnology in areas such as medicine, agriculture, environment and human health.
Silver nanoparticles are the subject of immense interest because of their distinct chemical and physical properties that are different from their bulk counterpart. This makes these nanoparticles very important in many fields including antimicrobial applications, biosensor materials, composite fibers, cryogenic superconducting materials, cosmetic products, and electronic components. This book aims to provide in-depth study and analysis of various fabrication, characterization, and application techniques of silver nanoparticles that lead these nanoparticles very important in the recent technology. This book presents deep understanding of the new techniques from basic to the advanced level. This book addresses scientists, engineers, doctoral and postdoctoral fellows, and technical professionals working in specialized fields.
This book brings together reviews from international experts who are exploring the biological activities of nanomaterials for medical applications or to better understand nanotoxicity. Topics include but are not limited to the following: 1) mechanistic understanding of nanostructure-bioactivity relationships; 2) the regulation of nanoparticles’ bioactivity by means of chemical modification; 3) the new methodologies and standard methods used to assess nanoparticles’ bioactivity; 4) the mechanisms involved in nanoparticle-biomolecule interactions and nanoparticle-cell interactions; and 5) biomedical applications of nanotechnology. The book will be a valuable resource for a broad readership in various subfields of chemical science, engineering, biology, environment, and medicine.
Green Synthesis of Silver Nanomaterials illustrates how to biologically scale up silver nanoparticle synthesis. This book covers green synthesis of silver nanomaterials, via plants, agricultural waste, fungi, and microorganisms. Sections cover the synthesis and characterization of chemical and green synthesis, various types of silver nanomaterialism, the ability of different fungal species, such as filamentous fungi, to produce silver nanoparticles, the microbial synthesis of silver NMs, biosynthesis mechanisms, toxicity, fate and commercialization. As examples, greener pathways and mechanisms, toxicity of silver nanoparticles in aquatic life and in natural eco-systems, and strategies for the scaling up of green-synthesized nanomaterials are discussed. With the extended work in enhancing nanomaterials synthesis performance, and discovering their biomedical, environmental, and agricultural applications, it is hoped that the execution of these methods on a large scale and their industrial applications in different fields will take place in the near future. - Assesses the impact of a large variety of silver-based nanostructures in the biomedical, environmental and agri-food sectors - Discusses the major synthesis methods used for effectively processing plant-based silver nanoparticles - Outlines the potential and major challenges for adopting green synthesis methods on a mass scale