Environmental occurrences, behavior, fate, and ecological effects of nanomaterials: an introduction to the special series

The release of engineered nanomaterials (ENMs) into the biosphere will increase as industries find new and useful ways to utilize these materials. Scientists and engineers are beginning to assess the material properties that determine the fate, transport, and effects of ENMs; however, the potential impacts of released ENMs on organisms, ecosystems, and human health remain largely unknown. This special collection of four review papers and four technical papers identifies many key and emerging knowledge gaps regarding the interactions between nanomaterials and ecosystems. These critical knowledge gaps include the form, route, and mass of nanomaterials entering the environment; the transformations and ultimate fate of nanomaterials in the environment; the transport, distribution, and bioavailability of nanomaterials in environmental media; and the organismal responses to nanomaterial exposure and effects of nanomaterial inputs, on ecological communities and biogeochemical processes at relevant environmental concentrations and forms. This introductory section summarizes the state of knowledge and emerging areas of research needs identified within the special collection. Despite recent progress in understanding the transport, transformations, and fate of ENMs in model environments and organisms, there remains a large need for fundamental information regarding releases, distribution, transformations and persistence, and bioavailability of nanomaterials. Moreover, fate, transport, bioaccumulation, and ecological impacts research is needed using environmentally relevant concentrations and forms of ENMs in real field materials and with a broader range of organisms.     

The role of atmospheric transformations in determining environmental impacts of carbonaceous nanoparticles

In studies that have explored the potential environmental impacts of manufactured nanomaterials, the atmosphere has largely been viewed as an inert setting that acts merely as a route for inhalation exposure. Manufactured nanomaterials will enter the atmosphere during production, use, and disposal, and rather than simply being transported, airborne nanoparticles are in fact subject to physical and chemical transformations that could modify their fate, transport, bioavailability, and toxicity once they deposit to aqueous and terrestrial ecosystems. The objective of this paper is to review the factors affecting carbonaceous nanomaterials' behavior in the environment and to show that atmospheric transformations, often overlooked, have the potential to alter nanoparticles' physical and chemical properties and thus influence their environmental fate and impact. Atmospheric processing of naturally occurring and incidental nanoparticles takes place through coagulation, condensation, and oxidation; these phenomena are expected to affect manufactured nanoparticles as well. It is likely that carbonaceous nanomaterials in the atmosphere will be oxidized, effectively functionalizing them. By influencing size, shape, and surface chemistry, atmospheric transformations have the potential to affect a variety of nanoparticle-environment interactions, including solubility, interaction with natural surfactants, deposition to porous media, and ecotoxicity. Potential directions for future research are suggested to address the current lack of information surrounding atmospheric transformations of engineered nanomaterials.     

Mobility of acid-treated carbon nanotubes in water-saturated porous media

The production, use, and disposal of nanomaterials may inevitably lead to their appearance in water. With the development of new industries around nanomaterials, it seems necessary to be concerned about the transport of nanomaterials in the environment. In this paper, the transport of acid-treated carbon nanotubes (CNTs) in porous media was investigated. Before the mobility investigation, the stability of acid-treated CNT dispersions was studied using ultraviolet-visible spectra and it was indicated that, under the chemical conditions employed in this work, there was no apparent aggregation. The mobility investigation showed that transport of acid-treated CNTs increased with treatment time due to increase in particle zeta potential. Carbon nanotubes treated with nitric acid for 2, 6, and 12 h possessed measured zeta potentials of -30.0, -43.0, and -48.5 mV, respectively. Utilizing clean-bed filtration theory, we showed that acid-treated CNTs have the potential to migrate 3.28, 5.67, and 7.69 m in saturated glass beads, respectively. We showed that solution ionic strength and pH have important effects on the mobility of acid-treated CNTs. Increasing the pH from 6.0 to 7.9 resulted in an increase in migration potential from 2.96 to 10.86 m. Increasing the ionic strength from 0.005 to 0.020 M resulted in a decrease in CNT migration potential from 5.67 to 1.42 m.     

An ecological perspective on nanomaterial impacts in the environment

Growing concerns over the potential for unintended, adverse consequences of engineered nanoparticles (ENPs) in the environment have generated new research initiatives focused on understanding the ecological effects of ENPs. Almost nothing is currently known about the fate and transport of ENPs in environmental waters, soils, and sediments or about the biological impacts of ENPs in natural environments, and the bulk of modern nanotoxicogical research is focused on highly controlled laboratory studies with single species in simple media. In this paper, we provide an ecological perspective on the current state of knowledge regarding the likely environmental impacts of nanomaterials and propose a strategy for making rapid progress in new research in ecological nanoscience.     

Fate and transport of engineered nanomaterials in the environment

With the fast development of nanotechnology, engineered nanomaterials (ENMs) will inevitably be introduced into the various environment. Increasing studies showed the toxiccity of various ENMs, which raises concerns over their fate and transport in the environment. This review focuses on advances in the research on environmental transport and fate of ENMs. Aggregation and suspension behaviors of ENMs determining their fate and transport in aqueous environment are discussed, with emphasis on the influencing factors, including natural colloids, natural organic matter, pH, and ionic strength. Studies on the transport of ENMs in porous media and its influencing factors are reviewed, and transformation and organismcleansing, as two fate routes of ENMs in the environment, are addressed. Future research directions and outlook in the environmental transport and fate of ENMs are also presented.     

A comprehensive review of the energy efficiency on nano coated fin and tube condenser

The condenser is a piece of equipment used to effectively transfer heat from water to the environment. The fin and tube condenser is the most commonly used in commercial applications. The improved performance of heat transfer in the fin and tube condenser is a significant area of study all over the world because optimizing the efficiency of heat transfer in the condenser will contribute to enhancing the effectiveness of system performance. The vapor deposition, plasma spray, and thermal spray techniques are being used, and it is determined that a heat transfer enhancing coating improves condenser performance. This review discusses the nanomaterial coating over the fin and tube condenser in detail. The various nanomaterial coatings with various propositions and coating methods had been discussed with the evidence of previous researchers. At a 50-degree inclination angle on the condensate plate, the condensate over the coating surface increases by more than 30%. The thermal properties of the working fluid are improved over the condenser, and the overall effectiveness of the condenser is increased by approximately 40% over the non-coated condenser. A 1% volumetric concentration of Nanoparticles in the coated material achieves a maximum efficiency increase of 78.7%.     

Transport and retention of Cryptosporidium parvum oocysts in sandy soils

A series of miscible-displacement experiments was conducted to examine the retention and transport behavior of oocysts in natural porous media. Three soils and a model sand were used that differed in physical and geochemical properties. Transport behavior was examined under various treatment conditions to help evaluate retention mechanisms. Significant retention of oocysts was observed for all media despite the fact that conditions were unfavorable for physicochemical interactions with respect to DLVO theory. The magnitude of retention was not influenced significantly by alterations in solution chemistry (reduction in ionic strength) or soil surface properties (removal of soil organic matter and metal oxides). On the basis of the observed results, it appears that retention by secondary energy minima or geochemical microdomains was minimal for these systems. The porous media used for the experiments exhibited large magnitudes of surface roughness, and it is suggested that this surface roughness contributed significantly to oocyst retention.     

纳米材料在环境保护中的应用与发展

综述了纳米材料的环保功能以及其在环境保护中的应用，并列举了近年出现的纳米环保产品，提出了纳米材料在环保应用中存在的问题。     

抗生素在沉积物中的吸附机制及其影响因素

抗生素作为医疗业和农业使用量最大的药物之一,由于其本身的特性,很容易进入沉积物一水环境中。抗生素在沉积物中的吸附过程是影响抗生素的反应活性、可移动性、持久性及生物可利用性的关键过程。本文选择四环素类、喹诺酮类、磺胺类和大环内酯类4类常用抗生素,在总结了这4类抗生素在湖泊沉积物中污染状况的基础上,分析了抗生素在沉积物中的吸附机制,并归纳论述了pH值、盐度、重金属离子、表面活性剂以及水动力条件对其在沉积物上吸附的影响机制。     

纳米材料特性及其在环境保护领域的应用

纳米材料是指晶粒尺寸为纳米级(10-9米)的超细材料。纳米技术作为一种最具有市场应用潜力的新兴科学技术,它将成为众多技术的创新动力。本文概述了纳米材料的形态、特殊性质以及纳米材料的应用,以使大家更清楚地认识纳米材料,并了解其在环保领域的应用现状与前景。     

Virus retention and transport as influenced by different forms of soil organic matter

Organic materials are widespread in natural soil and aquatic environments. Their effect on virus transport is very important in assessing the risk for contamination of ground water by viruses. This study aimed to determine how different forms (mineral-associated and dissolved) of natural organic matter influence the retention and transport of two bacteriophages (MS-2 and phiX174) in two porous media (a sand and a soil). We found that mineral-associated organic matter significantly promoted the transport of one virus (MS-2) but not the other (phiX174) in a phosphate-buffered saline solution. Similarly, MS-2 was retained less in sand columns with increasing concentrations of dissolved humic acid, while little effect was observed for phiX174 under the same conditions. The two viruses have different surface properties and thus exhibited different reactivity to the metal oxides present on sand particles and were affected differently by organic matter. Because the organic matter used in the study was negatively charged and hydrophilic, blocking of virus sorption sites and increasing of virus-medium electrostatic repulsion arising from modification of the sand and virus surface by organic matter are probably responsible for the facilitated transport. For dissolved humic acid, its competition for sorption sites with viruses was an additional mechanism involved. This study suggests that the effect of organic matter varied depending on the organic material properties and the type of viruses involved. As a general trend, the effect of organic matter was dominated by electrostatic rather than hydrophobic interactions.     

Transport and retention of fullerene nanoparticles in natural soils

Commercial production and use of fullerene (C60) nanomaterials will inevitably lead to their release into the environment, where knowledge of C60 fate and transport is limited. In this study, a series of one-dimensional column experiments was conducted to assess the transport and retention of nanoscale fullerene aggregates (nC60) in water-saturated soils. Under the experimental conditions, complete retention of nC60 was observed in columns (2.5 cm inside diameter x 11 cm length) packed with Appling or Webster soil, which contain 0.75 and 3.33% organic carbon by weight, respectively. When the volume of aqueous nC60 suspension (approximately 4.5 mg L(-1)) applied to Appling soil was increased from 5 to 65 pore volumes, the travel distance increased from 3 to 8 cm, and the retention capacity approached a limiting value of 130 microg g(-1), although nC60 was not detected in the column effluent. The addition of 20 mg C L(-1) Suwannee River humic acid to the influent suspension increased the nC60 transport in Appling soil but did not resul in breakthrough. Attempts to simulate the experimental data using clean-bed filtration theory were not satisfactory, yielding retention profiles that failed to match observed data. Subsequent incorporation of a limiting retention capacity expression into the mathematical model resulted in accurate predictions of the measured nC60 retention profiles and transport behavior. The sizable retention capacities observed in this study suggest that transport of nC60 is limited in relatively fine-textured soils containing appreciable amounts of clay minerals and organic matter, with substantial accumulation of nC60 aggregates near the point of release.     

The presence of pharmaceuticals in the environment due to human use – present knowledge and future challenges

Intensive research on pharmaceuticals in the environment started about 15 years ago. Since then a vast amount of literature has been published. The input and presence of active pharmaceutical ingredients (APIs) and their fate in the environment were and is still of high interest. As it has been extensively demonstrated that the active compounds are present in the environment some of the research interest has moved from analysis of the compounds, which is still undertaken, to effect studies in the lab and in field trials. It has been found that environmental concentrations can cause effects in wildlife if proper tools are applied for effect assessment. The question of mixture toxicity has gained more and more attention. It has been learned that classical tests may underestimate effects and risks. Work has been done in the field of risk assessment and risk management. As for risk management strategies to eliminate pharmaceuticals from wastewater or from the effluent of sewage treatment plants have been proposed and investigated. A tremendous amount of literature can now be found describing technical management measures such as oxidative or photolytic effluent treatment, filtering techniques, and application of charcoal. It has been learned however, that each of these approaches has its specific shortcomings. Therefore, additional approaches such as including people handling and using the compounds, and focusing on the properties of the compounds (“green pharmacy”) came into focus. Accordingly, this review gives an overview of the present state of knowledge presenting typical results and lines of discussion. This review makes no claim to give a complete overview including the full detailed body of knowledge of pharmaceuticals in the environment. Rather, it addresses important and typical topics to stimulate discussion.     

New perspectives in ecotoxicology

The task of regulating potentially harmful chemicals in the environment is presently hindered by the lack of appropriate concepts and methods for evaluating the effects of anthropogenic chemicals on ecosystems. Toxicity tests at the molecular and physiological levels have been used successfully as indicators of adverse effects on test organisms and have been extrapolated to humans to establish a basis for risk assessment. However, laboratory measurements of effects upon individuals do not translate readily into potential effects upon natural populations, in part because natural populations interact with other populations and with the physical environment. Even more difficult to assess are the deleterious impacts of anthropogenic chemicals on ecosystems, because of effects on species interactions, diversity, nutrient cycling, productivity, climatic changes, and other processes.Effects on ecosystems resulting from chemical stresses are outside the realm of classical toxicology, and an ecosystem-level perspective is essential for the consideration of such effects; but the science that deals with ecosystem-level effects,ecotoxicology, is still developing. This article synthesizes the topics discussed at a workshop on ecotoxicology held by the Ecosystems Research Center at Cornell University. Topics covered include: the regulatory framework in which ecotoxicological research must be applied; ecosystem modification of toxicant fate and transport; how ecosystem composition, structure, and function are influenced by chemicals; methods currently available for predicting the effects of chemicals at the ecosystem level; and recommendations on research needs to enhance the state of the science of ecotoxicology.     

Zerovalent iron nanoparticles for treatment of ground water contaminated by hexachlorocyclohexanes

Ground water and aquifer samples from a site contaminated by hexachlorocyclohexanes (HCHs; C(6)H(6)Cl(6)) were exposed to nanoscale iron particles to evaluate the technology as a potential remediation method. The summed concentration of the HCH isomers in ground water was approximately 5.16 micromol L(-1) (1500 microg L(-1)). Batch experiments with 2.2 to 27.0 g L(-1) iron nanoparticles showed that more than 95% of the HCHs were removed from solution within 48 h. Using a pseudo first-order kinetics model, the HCH isomers were removed in accordance with the trend gamma congruent with alpha > beta > delta. This seems to be correlated with the orientation (axial vs. equatorial) of the chlorine atoms lost in the dihaloelimination steps. Although the reactivity of the HCH isomers has been investigated in the classical organic chemistry literature, the present study was the first in the environmental remediation arena. The rate of removal is directly correlated to the number of axial chlorines. The observed rate constant varied from 0.04 to 0.65 h(-1), and the rate constant normalized to the iron surface area concentration ranged from 5.4 x 10(-4) to 8.8 x 10(-4) L m(-2) h(-1). Post-test extractions of the reactor contents detected little HCH remaining in solution or on the iron surfaces, reinforcing the contention that reaction rather than sorption was the operative mechanism for the HCH removal. Together with previously published work on a wide variety of chlorinated organic solvents, this work further demonstrates the potential of zerovalent iron nanoparticles for treatment and remediation of persistent organic pollutants.     

Effect of shape of nanoparticle on heat transfer and entropy generation of nanofluid-jet impingement cooling

ABSTRACT

Al₂O₃/water nanofluid has been numerically examined for the first time with different nanoparticle shapes including, cylindrical, blade, brick, platelet and spherical, on the flat and triangular-corrugated impinging surfaces. The volume fractions of 1.0%, 2.0% and 3.0% nanoparticles have been used. The Reynolds number is between 100–500 depending on the slot diameter. The finite volume method is utilized to determine the governing equations. The study is analyzed to determine how the flow features, heat transfer features and entropy production were affected by the diversity of nanoparticle shape, nanoparticle volume fraction, and shape of impinging surface. Darcy friction factor and Nusselt number are studied in detail for different conditions. The temperature contours are presented in the case of different nanoparticle volume fractions, nanoparticle shapes and both impinging surfaces. The results of the study suggest that the nanoparticle shape of the platelet shows the highest heat transfer development due to the thinner thermal boundary layer. Heat transfer augments with increasing volume fraction of nanoparticles. In addition, the study is consistent with the results of the literature on heat transfer and flow properties.     

EXPERIMENTAL VERIFICATION OF MULTICOMPONENT GROUND WATER CONTAMINATION PREDICTIONS1

ABSTRACT: Recent advances in mass transport modeling have made possible computation of the theoretical consequences of intricate multicomponent species interactions during ground water contamination events. Predictions such as strong chromatographic effects and induced downstream precipitations may have considerable impact on environmental analysis and regulation. Results of laboratory attempts to verify theoretical multicomponent transport predictions are discussed. Evidence presented here indicates that natural variability of soil properties make such verifications difficult. Although species interactions are easily confirmed, dramatic effects often exist only within small mathematical windows in strongly variable coefficient sets. Currently, the ability to generate multicomponent predictions apparently exceeds the ability to quantify the necessary, presumably deterministic, information required for real soils.     

Major factors influencing the efficacy of vegetated buffers on sediment trapping: a review and analysis

Sediment is a major agricultural pollutant threatening water quality. Vegetated buffers, including vegetative filter strips, riparian buffers, and grassed waterways, are best management practices (BMPs) installed in many areas to filter sediments from tailwaters, and deter sediment transport to water bodies. Along with reducing sediment transport, the filters also help trap sediment bound nutrients and pesticides. The objectives of this study were: (i) to review vegetated buffer efficacy on sediment trapping, and (ii) to develop statistical models to investigate the major factors influencing sediment trapping. A range of sediment trapping efficacies was found in a review of over 80 representative BMP experiments. A synthesis of the literature regarding the effects of vegetated buffers on sediment trapping is needed. The meta-analysis results based on the limited data showed that buffer width and slope are two major factors influencing BMPs efficacy of vegetated buffers on sediment trapping. Regardless of the area ratio of buffer to agricultural field, a 10 m buffer and a 9% slope optimized the sediment trapping capability of vegetated buffers.     

农村生活污水与小流域水环境协同治理的规则型构——基于临沂“兰山模式”的实践样本

如何对农村地区的流域水环境进行高效而低成本的治理,是当前农村资源环境治理面临的挑战之一。本文以山东临沂市兰山区柳青河水环境污染治理作为典型案例,从规则型构视角剖析行动规则对"兰山模式"的作用机制。其中,边界规则打破了农村生活污水与小流域水环境资源治理的边界,企业等新行动主体的资金、技术的溢出效应提高了治理效率;身份规则改变了行动主体的参与动机,加强了多方主体间的交互作用;选择规则减少了多方治理主体的责任冲突;聚合规则弥补了农户在环境治理中的缺位。在四项行动规则的共同作用下,"兰山模式"实现了农村生活污水与小流域水环境的协同治理,是农村水环境治理的实践样本。