Allison Rick VandeVoort

Effects of Silver Nanoparticle on Soil-Nitrification Processes

The release of silver (Ag) nanoparticles (NPs) from the use of consumer products to the environment has raised concern about the risk to ecosystems because of its unpredictable toxicological impact to microorganisms in terrestrial environment. In this study, the impact of Ag chemical speciation (Ag+ and Ag-NPs [50-nm uncoated and 15-nm polyvinylpyrrolidone (PVP)-coated Ag-NPs]) to soil nitrification kinetics was investigated using a batch soil-slurry nitrification method along with sorption isotherm and dissolution experiments. The results of nitrification potential (i.e., kinetic rate) suggest that Ag+/Ag-NPs, which strongly sorb in soils, suppressed the nitrification processes. Among each chemical species, the degree of suppression increased with increasing [Ag]total. Although ionic Ag (Ag+) species is known to exhibit greater antimicrobial effects than the solid state Ag species, such as Ag-NPs, in most studies, PVP-coated 15-nm Ag-NPs, however, more effectively suppressed the soil nitrification process than did Ag+ under the same dose. Although several physicochemical-based toxicity mechanisms of dispersed Ag-NPs were discussed in pure culture and aquatic systems, it is not clearly understood how PVP-coated Ag-NPs could exhibit greater toxicity to nitrifying bacteria than Ag+ in soils. In assessing the impact of Ag-NPs to microbial mediated processes (e.g., N cycles) in the terrestrial environment, it might be critical to understand the interactions and reactivity of Ag-NPs at the soil–water interface.

Environmental Chemistry of Silver in Soils: Current and Historic Perspective

Abstract Silver, Ag, is a metallic element that has been valued for its use in currency, jewelry, photoprocessing, electronics, and in the medical field. In the past decade, there have been many advances in the field of nanotechnology, including the use of silver and other metal nanoparticles. Silver nanoparticles are currently one of the most common metal nanoparticles found in consumer products. Because of the strong bactericidal properties of Ag(I) and Ag nanoparticles, their unpredictable fate of silver in soil–water environments has become a serious concern. Regulatory agencies now face difficulties revising/developing proper risk assessment methods to protect agroecosystems and human health. This chapter focuses on historical data of Ag interactions in soil environments, including geochemical occurrence, sorption/desorption processes, and mineral dissolution. Where research is sparse, a review of soft and borderline metal (e.g., Cd(II), Hg(II), Tl(I), Cu(II), Zn(II), Pb(II)) soil interactions is included, as analogs to Ag(I) reactivity. In addition, newer data focusing on emerging Ag nanoparticle technology and its activity in soil environments are included.

Environmental Chemistry of Silver in Soils

Abstract Silver, Ag, is a metallic element that has been valued for its use in currency, jewelry, photoprocessing, electronics, and in the medical field. In the past decade, there have been many advances in the field of nanotechnology, including the use of silver and other metal nanoparticles. Silver nanoparticles are currently one of the most common metal nanoparticles found in consumer products. Because of the strong bactericidal properties of Ag(I) and Ag nanoparticles, their unpredictable fate of silver in soil–water environments has become a serious concern. Regulatory agencies now face difficulties revising/developing proper risk assessment methods to protect agroecosystems and human health. This chapter focuses on historical data of Ag interactions in soil environments, including geochemical occurrence, sorption/desorption processes, and mineral dissolution. Where research is sparse, a review of soft and borderline metal (e.g., Cd(II), Hg(II), Tl(I), Cu(II), Zn(II), Pb(II)) soil interactions is included, as analogs to Ag(I) reactivity. In addition, newer data focusing on emerging Ag nanoparticle technology and its activity in soil environments are included.

Macroscopic assessment of nanosilver toxicity to soil denitrification kinetics.

A large increase in commercial and home use of silver nanoparticle (AgNP) products and technologies has raised concerns about their impact on environmental health. While several sources cite soils and sediments as the predominant sink for AgNPs in natural environments, few studies contribute to risk assessment of AgNPs in terrestrial environments. In this study, the effect of AgNPs ([Ag]: 1-100 mg/kg, 15-50 nm with 0-90% polyvinylpyrrolidone [PVP] capping agent) on soil denitrification processes was investigated with batch kinetic experiments using well-characterized AgNPs. Although the effects on denitrification kinetics and equilibrium end-points were variable among the AgNPs, denitrification kinetics were limited under certain conditions (e.g., PVP-coated AgNPs ≥ 10 mg/kg). In assessing the impact of AgNPs on ecosystem processes, it is important to consider the interactions of AgNPs with soils and sediments in addition to the physicochemical properties (size, coating agents, sedimentation rate, solubility, surface charge properties, dispersibility) of AgNPs.

Applying the process of backward design in revising an environmental science program

The purpose of this article is to share our model of a successful curriculum reform process and provide an overview so that it can be replicated by other programs. The process of backward design is commonly used for course design, and here we apply this framework to a program-level revision of student learning outcomes, curriculum, and assessment. Graduates from our Environmental Science program are expected to demonstrate an understanding of the appropriate academic content, to be able to conduct research and develop professional behaviors and dispositions. Our revised program now has clear, assessable student learning outcomes, a set of coursework that is well aligned with these outcomes, and planned assessment that will allow us to evaluate our students and our program. This program revision has been a long, time-consuming process that has been facilitated by the cooperative nature and dedication of the individuals on the Environmental Science committee and by support structures at our institution. We will discuss the methods used by our program to bring about these changes and also the challenges we faced.