Fate and Reactivity of Natural and Manufactured Nanoparticles in Soil/Water Environments

Nanoparticles (NPs), \u3c 100 nm in diameter, make up the smallest component of solid material. This small size often causes increased reactivity in soil/water environments, which is true for both natural NPs, such as very fine clay particles, and for manufactured nanoparticles, such as silver nanoparticles (AgNPs). As the importance of these particles is more widely recognized, and as manufactured nanoparticles, especially AgNPs, are increasing in production, it is essential to consider their effect on terrestrial and aquatic environments. The studies presented in this dissertation show that both the physicochemical characteristics of the NPs (e.g., particle size, surface coating, elemental composition), as well as soil-water interfacial chemistry (e.g., ionic strength, ligand concentration, pH), are instrumental in predicting environmental fate and reactivity. Ligand type and concentration were especially important in NP reactivity and bioavailability. Using the hard/soft acid/base concept, the effect of phosphate ligand (hard base) on Fe/Al (hard acid) oxyhydroxide natural NPs was investigated in Chapters 2 and 3. Adding phosphate to soil NPs and reference nano-minerals (Fe-(oxyhydr)oxides and kaolinite) caused coagulation or dispersion, changing the particle size of the NPs, as well as affecting the amount of phosphate in its bioavailable (i.e., dissolved) form. A review of the literature in Chapters 1 and 3 revealed that changes in the soil conditions, and therefore, soil colloids/NPs (e.g., increasing organic matter via amendments), also has a direct impact on the soil NP-facilitated phosphate transport processes. Silver, a soft acid, reacts readily with thiol functional groups, soft bases, in humic substances prevalent in soil environments. The effect of soil constituents on AgNP reactivity and phase transformation was investigated in Chapters 4 and 5. The presence of solid surfaces facilitated sorption and phase transformation in all AgNPs studied over the course of 30 days, especially when compared to the same AgNPs aged in aqueous environments in the absence of soil. When the bioavailability of Ag (as ionic and NPs), a known antimicrobial agent, was assessed via denitrification experiments in Chapter 5, the AgNPs exhibited much less toxicity than expected, perhaps due to their strong sorption onto soil particles, as observed in the adsorption isotherm experiments conducted in Chapter 4. A more in-depth study of Ag(I) and AgNPs, and their interactions with cysteine, an amino acid with a thiol functional group, at the goethite-water interface in Chapter 6 revealed that, while cysteine enhanced the sorption of Ag(I) on goethite surfaces by forming inner-sphere ternary surface complexes, AgNP sorption to goethite was largely unaffected by cysteine. The behavior suggests hydrophobic interactions of AgNPs on goethite surfaces, revealing the effects of a soft ligand on Ag are via species specific (Ag(I) or AgNPs) mineral interactions, and are important in predicting AgNP fate in soil systems. This dissertation provides a novel viewpoint of natural and manufactured NP interactions in soil environments. These interactions are dictated by both particle-specific characteristics and environmental conditions. When environmental conditions, especially the presence of reactive ligands (based on the hard/soft acid/base theory), are altered by anthropogenic or indigenous means, the reactivity of certain NPs changes dramatically, impacting the bioavailability of contaminants such as phosphate, Ag(I), or AgNPs

Introduction to Environmental Science: 2nd Edition

2nd Edition: Revised by Kalina Manoylov, Allison Rick VandeVoort, Christine Mutiti, Samuel Mutiti and Donna Bennett in 2017. Authors\u27 Description: This course uses the basic principles of biology and earth science as a context for understanding environmental policies and resource management practices. Our planet is facing unprecedented environmental challenges, from oil spills to global climate change. In ENSC 1000, you will learn about the science behind these problems; preparing you to make an informed, invaluable contribution to Earth’s future. I hope that each of you is engaged by the material presented and participates fully in the search for, acquisition of, and sharing of information within our class. Environmental Science Laboratory (ENSC 1000L) is a separate class and you will receive a separate grade for that course. Course Objectives Upon completion of this course, you will be able to: Evaluate the diverse responses of peoples, groups, and cultures to environmental issues, themes and topics. Use critical observation and analysis to predict outcomes associated with environmental modifications. Demonstrate knowledge of the causes & consequences of climate change. Apply quantitative skills to solve environmental science problems. Demonstrate knowledge of environmental law and policy. Design and critically evaluate experiments. Interpret data in figures and graphs. This open textbook for Introduction to Environmental Science was created under a Round Two ALG Textbook Transformation Grant. Accessible files with optical character recognition (OCR) and auto-tagging provided by the Center for Inclusive Design and Innovation.https://oer.galileo.usg.edu/biology-textbooks/1003/thumbnail.jp

Introduction to Environmental Science

This Grants Collection uses the grant-supported open textbook Introduction to Environmental Science from Georgia College and State University: http://oer.galileo.usg.edu/biology-textbooks/4/ This Grants Collection for Introduction to Environmental Science was created under a Round Two ALG Textbook Transformation Grant. Affordable Learning Georgia Grants Collections are intended to provide faculty with the frameworks to quickly implement or revise the same materials as a Textbook Transformation Grants team, along with the aims and lessons learned from project teams during the implementation process. Documents are in .pdf format, with a separate .docx (Word) version available for download. Each collection contains the following materials: Linked Syllabus Initial Proposal Final Reporthttps://oer.galileo.usg.edu/biology-collections/1001/thumbnail.jp

Macroscopic observation of soil nitrification kinetics impacted by copper nanoparticles: Implications for micronutrient nanofertilizer

The potential agricultural use of metal nanoparticles (NPs) for slow-release micronutrient fertilizers is beginning to be investigated by both industry and regulatory agencies. However, the impact of such NPs on soil biogeochemical cycles is not clearly understood. In this study, the impact of commercially-available copper NPs on soil nitrification kinetics was investigated via batch experiments. The X-ray absorption near edge structure spectroscopy analysis showed that the NPs readily oxidized to Cu(II) and were strongly retained in soils with minimum dissolution (\u3c1% of total mass). The Cu2+ (aq) at 1 mg/L showed a beneficial effect on the nitrification similar to the control: an approximately 9% increase in the average rate of nitrification kinetics (Vmax). However Vmax was negatively impacted by ionic Cu at 10 to 100 mg/L and CuNP at 1 to 100 mg/L. The copper toxicity of soil nitrifiers seems to be critical in the soil nitrification processes. In the CuNP treatment, the suppressed nitrification kinetics was observed at 1 to 100 mg/kg and the effect was concentration dependent at ≥10 mg/L. The reaction products as the results of surface oxidation such as the release of ionic Cu seem to play an important role in suppressing the nitrification process. Considering the potential use of copper NPs as a slow-release micronutrient fertilizer, further studies are needed in heterogeneous soil systems

PRELIMINARY ASSESSMENT OF COMPOST QUALITY AND SAFETY AT GEORGIA COLLEGE**

The Georgia College (GC) Green Fee Committee and Sustainability Council initiated a food recovery program with an industrial-grade composter in 2017 to decrease landfilled food waste on campus. Both pre- and post-consumer food waste from GC Dining Services is recovered, combined with untreated wood chips as a carbon source, processed through the in-vessel industrial composter, and then set out in windrows to mature. Our goal is to assess the quality and safety of the final compost product, to expand its applications both on- and off-campus. Understanding the chemical nature of the compost is vital to determining its overall nutrient level, which impacts how confidently we could apply the compost as a soil amendment for landscaping and gardening. During Fall 2020, we began sampling compost in the windrows. From August to October 2020, pH and nitrate levels were tracked weekly and assessed in situ via ion-specific electrodes. Both pH and nitrate concentrations provide reliable indicators of the overall nutrient availability and maturity of the compost. We expected the pH level to stabilize around 6.0-7.0, which is slightly acidic and ideal to ensure that nutrients are in their plant-available state. The nitrate levels were expected to increase as heterotrophic microorganisms respire carbon and nitrifying bacteria act on the available ammonium. To further investigate compost safety, we analyzed previously collected X-ray fluorescence data on total metal concentration, including heavy metals. We expect minimal heavy metal concentration since the compost inputs were obtained from a controlled source. All chemical data were compared using quality standards from the US Composting Council. We hope that continued research on our campus’s compost will help ensure the overall sustainability of the project over time

Macroscopic Observation of Soil Nitrification Kinetics Impacted by Copper Nanoparticles: Implications for Micronutrient Nanofertilizer

The potential agricultural use of metal nanoparticles (NPs) for slow-release micronutrient fertilizers is beginning to be investigated by both industry and regulatory agencies. However, the impact of such NPs on soil biogeochemical cycles is not clearly understood. In this study, the impact of commercially-available copper NPs on soil nitrification kinetics was investigated via batch experiments. The X-ray absorption near edge structure spectroscopy analysis showed that the NPs readily oxidized to Cu(II) and were strongly retained in soils with minimum dissolution (<1% of total mass). The Cu2+ (aq) at 1 mg/L showed a beneficial effect on the nitrification similar to the control: an approximately 9% increase in the average rate of nitrification kinetics (Vmax). However Vmax was negatively impacted by ionic Cu at 10 to 100 mg/L and CuNP at 1 to 100 mg/L. The copper toxicity of soil nitrifiers seems to be critical in the soil nitrification processes. In the CuNP treatment, the suppressed nitrification kinetics was observed at 1 to 100 mg/kg and the effect was concentration dependent at ≥10 mg/L. The reaction products as the results of surface oxidation such as the release of ionic Cu seem to play an important role in suppressing the nitrification process. Considering the potential use of copper NPs as a slow-release micronutrient fertilizer, further studies are needed in heterogeneous soil systems

SPATIAL ANALYSIS AND TRANSPORT OF PHOSPHATE AT BABE AND SAGE FARM SOILS**

Eutrophication is one of the most important environmental issues concerning aquatic ecosystems today. Agricultural runoff is one of the primary sources of nutrients contributing to eutrophication. Phosphate, a key component of most fertilizers, is often the limiting nutrient in freshwater ecosystems. By measuring phosphate concentration in soil across a location gradient, it is possible to gain information as to how this nutrient moves through terrestrial systems and into surface water bodies. The location for this study is Babe + Sage Farm in Gordon, GA. Babe + Sage is a small sustainable farm just below the Fall Line in the Georgian coastal plain region. Farmers at this site have been using organic fish-based fertilizers in recent years. Results from previous testing at adjacent cultivated sites indicate high soil phosphate concentration. The purpose of this study is to assess how high soil phosphate from cultivated areas affects the surrounding environment. This study uses a soil desorption technique to quantify plant available phosphate originating from soil particle surfaces in the soils down-flow of the cultivated fields. The desorption tests were used to simulate runoff conditions in the coastal plain of Georgia. A pH of 4.6 was used to approximate the pH of local natural rainwater. Preliminary studies have shown high concentrations of phosphate in soils close to the fields, and, in general, phosphate desorptive capacity decreasing with increased distance from the fields, as expected. After testing overland runoff samples, we found high concentrations of phosphate travelling across the soil surface. The high concentration of phosphate in the overland runoff that was sampled raises our concern and increases the need for further testing. This research group will continue to test phosphate movement via overland flow in this system, and begin to investigate subsurface transport and particle-facilitated transport

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]total: 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

THE EFFECTS OF COMPOSTABLE DISHWARE ON OVERALL COMPOST QUALITY

Georgia College & State University (GCSU) has an active industrial compost system, where pre- and post-consumer waste is diverted from the dining facility. Currently, single-use disposable plastic and polystyrene dishware is used for campus events and to-go food services. The option of compostable dishware such as a Polylactic acid (PLA) hot cups, PLA cold cups, sugarcane portion cups, cardboard trays, and wooden sporks were explored to provide cost-effective options for these needs. This research project focuses on the impacts of compostable dishware on our compost system through weekly measurements of nitrate, pH, carbon: nitrogen ratio, moisture, and qualitative observations during fall semester, 2022. Through this project, we also developed an approach to assessing the impacts of compostable materials. In the preliminary data, the average pH of the in-vessel and ground compost was 7.7, the average nitrate level in these sample sites 1.8 mg/kg. After the implementation of the compostable dishware the pH became more basic with an increase from 5.8 to 6.9. Variation in nitrate levels increased due to anaerobic conditions within the in-vessel. The temperature of the compost decreased after the implementation of the dishware. We estimate that over 85% of the compostable dishware decomposed over the course of 5 weeks. These preliminary results suggest safe and beneficial compost to use on campus and in the community. The benefits of implementing a compostable single-use dishware initiative include cutting costs on waste from dining facilities, decreasing GCSU’s water and carbon footprints, while increasing education and awareness of sustainable practices in the GCSU community

ASSESSING SOIL REDOX CONDITIONS USING IRIS TUBES IN A CENTRAL GEORGIA WETLAND

The process of documenting soil redox potential has become increasingly important for use in wetland delineation studies. Wetlands are characterized by hydric soils, which are formed in saturated conditions, and are typically home to an anaerobic, reducing redox environment. Most established wetland delineation studies document soil redox conditions through Eh measurements via platinum electrodes and/or alpha-alpha-dipyridyl dye. However, these methods are costly, time-intensive, and complex. An alternative method of assessing reduction potential in situ is through the use of Iron Reduction in Soils (IRIS) tubes, which are fabricated from PVC pipes that have been sanded and coated with a synthetic Fe (III) hydroxide paint, then inserted into wetland soils for approximately four weeks. The reducing environment of the wetland soils facilitates reductive dissolution of Fe (III) painted on the tubes to Fe (II), causing a visually notable decrease in paint upon removal. This study aims to explore whether the use of IRIS tubes, in conjunction with measurements of physicochemical soil properties and hydric soils identification procedures, is effective in delineating wetland gradients in Central Georgia. Iron removal from IRIS tubes was assessed using both X-ray fluorescence (XRF) and Geographic Information Systems (GIS) methods. Water-table elevation and Fe extraction data of soil samples were also documented as evidence of reducing soil conditions. Evidence of redoximorphic features such as gley and oxidized root channels were also observed. Initial data from XRF and GIS analysis suggests that the highest Fe removal, reaching as high as 98%, occurred deeper into the soil profile, supporting our expectation of anaerobic soils to assist with reductive dissolution from the tubes. Based on the evidence collected, IRIS tubes showed promise in demonstrating reducing soil conditions and delineating wetlands in Central Georgia, while efficiently managing expenses and time spent in both the field and laboratory