Nanomaterials in the Environment

Designed to have very specific properties, engineered nanomaterials (NMs) are tailor made through chemical processes, physical processes, or both, and may be released into the environment primarily through industrial and environmental applications or during improper handling. Because of their nanoscale size, NMs may possess unique chemical, biological, and physical properties as compared with larger particles of the same material, which gives them an edge in diverse applications. This chapter discusses the fundamental properties of NMs and some of the phenomena that determine their fate, transport, and behavior in the environment. For example, processes such as agglomeration can drastically change the surface behavior of NMs. In addition, surface adsorption of different organic or inorganic entities may have substantial influence on the fate of NMs.

To assess the risks associated with manufactured nanomaterials (NMs), understanding their mobility, bioavailability, interaction with other materials, and toxicity is necessary. This chapter reviews current knowledge of the environmental effects NMs, including environmental assessments, environmental fate and behavior of NMs, and test methods for environmental nanomaterial monitoring. It presents the main groups of nanomaterials and summarizes the major routes of input of manufactured nanoparticles to the environment for different sectors and applications. The main engineering NMs can be classified into five groups: carbon NMs, metal-oxide NMs, zero-valence metal NMs, quantum dots, and dendrimers. Although significant progress in the development of characterization methods has been accomplished in recent years, reliable methods are not yet available to determine NMs’ identity, concentrations, and physicochemical characteristics in complex environmental matrices, such as water, soil, air, sediment, etc.

This chapter briefly describes characterization methods for nanomaterials (NMs), along with examples based on the authors’ experience for illustrative purposes. Spectroscopy methods, including ultraviolet/visible spectroscopy, infrared spectroscopy, surface-enhanced Raman spectroscopy, nano-Raman spectroscopy, and resonance Raman spectroscopy, are reviewed with emphasis on their principle of operation and spectral interpretation. The various microscopy methods, including transmission electron microscopy, scanning electron microscopy, scanning tunneling microscopy, and atomic force microscopy, are also described in terms of the wave-particle duality property of electrons. The chapter then describes inductively coupled plasma-based methods in terms of the analytical capability provided by the use of high-density plasmas coupled to one or more complementary techniques. Finally, the chapter focuses on two of the most useful nondestructive techniques used to characterize solid NMs: dynamic light scattering and X-rays.

This chapter describes the main microscopy techniques for nanomaterial (NM) and nanoparticle (NP) characterization with special emphasis on their use in the assessment of NPs and their possible transformation products under real, complex environmental scenarios. These techniques include transmission electron microscopy (TEM), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), environmental scanning electron microscopy (ESEM), scanning tunneling microscopy (STM), and atomic force microscopy (AFM). These techniques allow the visualization and characterization of different properties of NPs and NMs in environmental samples, including the state of aggregation, dispersion, sorption, size, structure, and shape, with TEM, SEM, and AFM being the most popular techniques. Spectroscopic techniques can be coupled to electron microscopy to obtain elemental composition information. The chapter also tabulates some examples of application of microscopy to environmental characterization and describes sample preparation techniques that lead to sample alteration and dehydration artefacts.

This chapter reviews the main techniques currently used to size nanoparticles (NPs) in environmental matrices, which are classified according to the physical principle on which they are based (microscopy, light scattering, and light spectroscopy, among others). Hyphenated techniques based on chromatography or electrophoresis, size-separation of colloidal suspensions, are also reviewed. The inherent characteristics, advantages, and limitations are presented and discussed. To size each kind of sample, the user should adopt a specific strategy depending on the matrix, the type of nanomaterials, and the desired additional information. A transmission electron microscopy + nanoparticle tracking analysis combination is proposed as a robust and balanced combination that may be sufficient to acquire the size distribution population of most of the NP suspensions and to obtain morphological, quantitative, and Z-potential parameters.

This chapter discusses the difficulties in analyzing nanoparticles (NPs) in the environment. The figures and tables in the first part of the chapter show the size, application, behavior, and fate of manufactured NPs in the environment. The second part of the chapter presents different electronic microscopic techniques such as transmission electron microscopy, dynamic light scattering, scanning electron microscopy, etc., that are applied to characterize NPs. Some NPs are characterized by shape and size; they have low solubility under normal conditions and are hydrophobic. The effects of other NPs and natural organic matter, the presence of anthropogenic compounds, and the low mass concentration in analyses of NPs are also discussed, leading to the conclusion that quantification and analyses of NPs cannot be achieved with these methods alone. This can contribute to the development of selective and sensitive analytical methods to be used in complex matrices.

Manufactured or engineered nanoparticles (NPs) can be classified by different means, but most materials fall into four different categories based on their chemical compositions: carbon based, metal based, aluminosilicates, and nanoscale polymers. Additional details regarding the major NPs in each category are presented with emphasis on materials used in commercial products and manufacturing facilities. The chapter also provides a broad overview of the different classifications of naturally occurring NPs; their occurrence in atmospheric, geologic, and aqueous environments; and the important geochemical processes that nanoscale particles influence. Naturally occurring NPs can be classified into inorganic and organic components, and the inorganic component can be further classified into nanominerals, mineral NPs, and amorphous materials. The chapter also briefly touches upon the consequences of anthropogenic NPs that are unintentionally produced during human activities and highlights the knowledge gaps regarding occurrence of NPs in natural environments.

This chapter presents an overview of the fate, transport, and behavior of nanomaterials (NMs) in the environment, explaining that most releases of manufactured NMs or engineered NMs originate from point or nonpoint sources. A few well-known properties are likely to be helpful in predicting the transport and separation among environmental media based on past research on contaminants (e.g., PCBs). The chapter provides examples of known chemical properties of nanoparticles in different environmental media. It then represents NM transformation in the environment with respect to NM release into air and its reaction and deposition, which leads to toxicity. NM transformation in other environment compartments may occur differently. Finally, the chapter discusses some cases of bioaccumulation in different types of organisms and overviews the current state of knowledge in this field.

This chapter reviews the behavior and fate of some nanomaterials (NMs) in the aquatic environment. Although many attractive and beneficial applications of NMs in water and wastewater treatment exist, uncertainties over health impacts and environmental fate of these NMs need to be addressed before widespread application. The sorption of inorganic and organic matter on NMs largely depends on their partitioning behavior to nanoparticles (NPs) and colloids. Fate and behavior of NMs not only depends on the physicochemical properties of NPs, but also on the characteristics of the receiving environment. The chapter presents the most commonly used NM applications and behavior in the water environment. Stable and dispersible NMs are bioavailable, which leads to accumulation in aquatic ecosystems and toxicity where unstable (aggregate) NMs accumulate in sediments. Therefore, surface-modified NPs have been synthesized to increase the stability and prevent homo and hetero aggregation and sedimentation.

This chapter focuses on typical properties of engineered nanomaterials (NMs) and their classification, sources, and environmental effects. It also discusses their fate and behavior in atmosphere, persistence and removal mechanisms, size distribution, effects on weather, and urban NMs. This information will help advance knowledge of the local- and global-scale impacts of NMs on weather and their role in climate change. Most NMs originate from manufactured sources, while some are engineered. A few natural sources also contribute to atmospheric NMs but not in significant amounts. While natural sources, such as volcanoes, forest fires, and chemical weathering of rocks, release a low-level of atmospheric NMs, more than 36% of all particles in the atmosphere are “incidental” manmade NMs. Three important parameters of NMs are generally of most interest to researchers and therefore directly or indirectly measured: surface characteristics, number concentration, and size distribution.

This chapter focuses on fate, transport, and behavior of natural nanomaterials (NMs) and engineered nanomaterials (ENMs) in soils. Special attention is paid to 1) transport of NMs in soil; 2) interactions between NMs and soil components; 3) persistence, toxicity, and safety of NMs in soil; and 4) removal of ENMs and engineered nanoparticles from soil. Before investigating the fate and behavior of NMs, identifying the source and form of NMs in which they are released into the soil is important. Attachment of NMs to themselves (aggregation and agglomeration), to inorganic or organic matter, or to organisms will affect transport of NMs. The chapter also discusses three main challenges related to NMs in the soil environment: removal of NMs from soils, analytical tools and methods, and regulations.

This chapter discusses the behavior and fate of natural and engineered nanomaterials in sediments, beginning with a discussion of the origin and nature of the sediments. Nanoparticles (NPs) are persistent in sediments. They have low solubility under normal conditions, are hydrophobic, tend to form aggregates, and are not biodegradable as they accumulate in aquatic biota. In addition to persistence, the chapter presents a general picture of the mechanisms of NP transport from water to sediment. Aggregation seems to be the main route for sedimentation and can occur as homoaggregation (between NPs) or heteroaggregation (with other particles). Understanding the fate of NPs in sediments would shed light on a large range of nanotechnology-related problems.

This chapter reviews aspects of engineered nanomaterials (ENMs) concerning their intentional application in nanoremediation and unintentional release to the environment. Because of their many benefits, nanomaterials are intentionally added into wastewater or effluent to remove or degrade specific pollutants before their discharge to the receiving water. However, nanoparticles (NPs) applied for water and wastewater remediation purposes represent an undesired pollutant, and thus nanoremediation has imposed the challenging task of removing added and water-carried NPs from the wastewater before release into the environment. In wastewater treatment plants, most of the ENMs are removed from suspension in primary and/or secondary sedimentation basins, where they are settled, wasted, and dewatered to form biosolids.

This chapter focuses on the impact of nanotechnology and engineered nanoparticles on the environment and various hazard and risk assessment methods employed to tackle the potential hazards that nanoparticles can pose to the environment, ecosystems, and human health. Steps in risk assessment are recognizing and characterizing the hazards, establishing the link between dose and response for various endpoints, and predicting the probability of exposure. Further, more detailed risk assessments based on precise models of environmental exposure routes may be reserved for engineered nanomaterials found to be both persistent and toxic, or for high-exposure scenarios. Finally, finding answers to present challenges and using new and upcoming technologies/systems/methods would help to elucidate the toxicities of various nanomaterials and be beneficial to nanotechnology.

More than a decade has passed since the UK Royal Society’s report (RS RAE 2004) spurred research and discussions on the potential health and environmental impacts of engineered nanomaterials (ENMs). Scientists, regulators, and other decision makers are still developing and establishing sound risk assessment (RA) approaches for ENMs. This chapter provides a detailed overview of RA methods and tools for ENMs. It specifically focuses on approaches that apply to ENM risk management despite the paucity of physiochemical and (eco) toxicological data and exposure models. In particular, it focuses on the recommendation to use different methods for different risk-based decision contexts. The chapter first presents select RA methodologies developed for ENM comparative assessment, screening, and management, and then overviews life-cycle analysis for ENMs. The chapter also presents RA frameworks that combine assessments to support decision making. Finally, it describes data needs for ENM RA.

Nano-ecotoxicology refers to the toxic effects nanomaterials (NMs) can have on animals, humans, plants, fungi, and microbes once NMs are released into the environment. The risks that natural nanoparticles (NPs) and engineered NPs impose because of their use in commercial products with environmental applications needs to be better understood. The chapter explains the most important pathways and processes of NP release and exposure in the environment and effects on animals and humans. Humans and animals are exposed to NPs in many ways either through air, contaminated ground water, or consumption of plants or animals that have accumulated NPs.

This chapter focuses on the nano-ecotoxicology of natural and engineered nanomaterials (NMs) in relation to microorganisms. Starting with mobility, bioavailability, and degradability of NMs in the environment, the chapter moves on to discuss general considerations of NM toxicity and ecotoxicity. The chapter then focuses on comet and micronucleus assays, including the K micronuclei and Ames tests and high-throughput screening and current status in related areas. Many reports indicate that NMs induce the formation of reactive oxygen species in cells and consequent inflammatory, mutagenic, or cellular death can occur. The physiological pathways of nanometals are poorly understood, and developments in this area are delayed by a lack of methods for measuring nanoparticles in natural conditions. The assays and results presented in the chapter highlight the need to investigate possible scenarios of interaction between NMs and the surrounding microenvironment.

With the revolution of nanotechnology-based industries, engineered nanoparticles (ENPs) have emerged and been incorporated into the environment at increasing rates, which is why ENP-related risks are of increasing concern. Nano-ecotoxicology and nano-genotoxicology in particular should push public authorities to evaluate the global impact of nanomaterial technologies and develop adequate regulation to manage environmental health and safety issues. This chapter briefly describes the occurrence of nanoparticles (NPs) in the environment and their interaction with plants at different levels: morphology, physiology, and genotoxicity. Assessing both positive and negative impacts of NPs used in commercial products and environmental applications requires a better understanding of their mobility, bioavailability, and toxicity. The chapter describes some of the most relevant studies on NP toxicity in plants.

This chapter discusses the ecotoxicology of nanomaterials (NMs), including that of engineered nanomaterials (ENMs) and engineered nanoparticles (ENPs), and the impact of nanotechnology on different ecosystems. Ecotoxicology is a multidisciplinary field that integrates toxicology and ecology and studies the effects of toxic chemicals on biological organisms. This approach predicts the effects of NMs on organisms to identify the most efficient and effective action to prevent or remediate any detrimental effect. The chapter describes some important recent research outcomes on the ecotoxic effects of some ENPs. Current understanding about the mechanisms of genotoxicity of nanoparticles is predominantly based on genotoxicity investigations performed with the particulate carcinogen quartz and poorly soluble particles of low toxicity such as carbon black and titanium dioxide. The chapter also describes common tests used in current genotoxic study of ENPs.

This chapter describes the tools and techniques available to assess nanoparticles (NPs) in the environment for NP-associated metabolomics studies. Starting with classification of NPs, the chapter then presents considerations and challenges associated with metabolomics of NPs; the protocols designed for sample preparation, extraction, separation, and detection; and nanoinformatics (computational approaches in nanotechnology). These approaches are designed to avoid compromising the reliability and quality of the analytical results in understanding the chemistry of NPs in environmental matrices. As no single detection technique is without potential artefacts, correct interpretation of NP characterization must be based upon many observations using a combination of techniques. Analytical methods must be able to differentiate between naturally occurring nanoparticles and engineered nanoparticles (ENPs) and size differentiate and separate the ENPs from everything else present in complex environmental matrices.

The development of nanotechnology has led to changes in industry, materials development, and health. Government commissions, organizations, enterprises, and all stakeholders involved in the use of nanomaterials should be questioned about which ethical principles (and moral consequences) regulations of nanotechnologies are based on. Immediacy of economic results or responsibility to the community must govern nanotechnology applications. The sense of community is and will be a source of responsibility and solidarity, leading to the notion of “ecology of action.” Any action increasingly escapes from the will and true intention of its author, as far as action interplays with the environment.

This chapter presents three different approaches to responsible nanotechnology. These approaches involve nanomaterials (NMs) in manufacturing, NMs for environmental remediation, and a sociotechnical integration of creativity and responsibility in the use of NMs. The chapter presents some examples of recent research and developments, including inorganic materials, organic materials, and composite materials. The chapter pays special attention to NMs produced by thermal plasma technology based on the author’s experience. It then describes recent information about self-replicating NMs. Some of the most common NMs used for the environmental detection of contaminants are described and classified in four categories: carbon-based materials, metallic nanoparticles (NPs), silicon-based NPs, and semiconductor NPs. Nanotechnology-based products have evolved quickly and their use in composite materials, solar cells, energy storage units, fuel cells, clothes, environmental remediation, etc., is imminent.

With growing awareness of the need for environmental sustainability, the importance of manufacturing and applying green nanomaterials (GNMs) has gained significant recognition. This chapter applies 12 principles of green chemistry in nanotechnology, precisely defining green nanotechnology and navigating the design of new technologies for joint economic, social, and health/environmental benefit. It then discusses in detail various emerging GNMs and the possibilities of designing unexplored ones. The chemical methods of metallic nanoparticle (MNPs) synthesis, although efficient, productive, and reproducible, do not give biocompatibility to MNPs. In such procedures, traces of unreacted reagents or unwanted byproducts remain in the colloidal solution, rendering the MNPs inappropriate for biological application. Researchers realized that the synthesis procedures rather than the product imparted the toxic property to the MNPs.