17 research outputs found
Heterogeneous Photocatalysis of Amoxicillin under Natural Conditions and High-Intensity Light: Fate, Transformation, and Mineralogical Impacts
The β-Lactam antibiotic amoxicillin is among the most widely used antibiotics in human and veterinary medicine. Consequently, amoxicillin is abundant in natural waters and can undergo diverse abiotic reactions to form degradation compounds under environmental conditions. Yet, little is known about these decay pathways and mineralogical impacts on environmental amoxicillin degradation. The current study focuses on understanding the mineralogical influences of amoxicillin degradation under ecological conditions. We studied the role of anatase and kaolinite on amoxicillin degradation under irradiated and non-irradiated conditions. Anatase increases amoxicillin degradation by 4.5-fold in the presence of light compared to just being exposed to sunlight. Interestingly, anatase also showed a higher degradation rate under dark than light controls. Conversely, kaolinite diminishes the amoxicillin degradation under irradiation. The formation of degradation compounds was mineralogy-controlled, while no mineralization was observed. Further, we irradiated amoxicillin with a high-intensity light to evaluate its removal from wastewater. The formation of varying amoxicillin degradation products with high-intensity light will limit its removal from wastewater. Our study emphasizes that the mineralogical impact on amoxicillin degradation is diverse, and the role of anatase is significant. Consequently, the increased addition of manufactured titanium nanoparticles to the environment can further enhance these effects
Atmospheric Processing and Iron Mobilization of Ilmenite: Iron-Containing Ternary Oxide in Mineral Dust Aerosol
Over the last several
decades, iron has been identified as a limiting
nutrient in about half of the worldâs oceans. Its most significant
source is identified as deposited iron-containing mineral dust that
has been processed during atmospheric transportation. The current
work focuses on chemical and photochemical processing of iron-containing
mineral dust particles in the presence of nitric acid, and an organic
pollutant dimethyl sulfide under atmospherically relevant conditions.
More importantly, ilmenite (FeTiO<sub>3</sub>) is evaluated as a proxy
for the iron-containing mineral dust. The presence of titanium in
its lattice structure provides higher complexity to mimic mineral
dust, yet it is simple enough to study reaction pathways and mechanisms.
Here, spectroscopic methods are combined with dissolution measurements
to investigate atmospheric processing of iron in mineral dust, with
specific focus on particle mineralogy, particle size, and their environmental
conditions (i.e., pH and solar flux). Our results indicate that the
presence of titanium elemental composition enhances iron dissolution
from mineral dust, at least by 2-fold comparison with its nontitanium-containing
counterparts. The extent of iron dissolution and speciation is further
influenced by the above factors. Thus, our work highlights these important,
yet unconsidered, factors in the atmospheric processing of iron-containing
mineral dust aerosol
Heterogeneous Uptake and Adsorption of Gas-Phase Formic Acid on Oxide and Clay Particle Surfaces: The Roles of Surface Hydroxyl Groups and Adsorbed Water in Formic Acid Adsorption and the Impact of Formic Acid Adsorption on Water Uptake
Organic
acids in the atmosphere are ubiquitous and are often correlated
with mineral dust aerosol. Heterogeneous chemistry and the uptake
of organic acids on mineral dust particles can potentially alter the
properties of the particle. In this study, heterogeneous uptake and
reaction of formic acid, HCOOH, the most abundant carboxylic acid
present in the atmosphere, on oxide and clays of the most abundant
elements, Si and Al, present in the Earthâs crust are investigated
under dry and humid conditions. In particular, quantitative adsorption
measurements using a Quartz Crystal Microbalance (QCM) coupled with
spectroscopic studies using Attenuated Total Reflection Fourier Transform
Infrared (ATR-FTIR) spectroscopy are combined to allow for both quantification
of the amount of uptake and identification of distinct adsorbed species
formed on silica, alumina, and kaolinite particle surfaces at 298
K. These oxides and clay particles show significant differences in
the extent and speciation of adsorbed HCOOH due to inherent differences
in surface âOH group reactivity. Adsorbed water, controlled
by relative humidity, can increase the irreversible uptake of formic
acid. Interestingly, the resulting layer of adsorbed formate on the
particle surface decreases the particle hydrophilicity thereby decreasing
the amount of water taken up by the surface as measured by QCM. Atmospheric
implications of this study are discussed
Heterogeneous Atmospheric Chemistry of Lead Oxide Particles with Nitrogen Dioxide Increases Lead Solubility: Environmental and Health Implications
Heterogeneous chemistry of nitrogen dioxide with lead-containing
particles is investigated to better understand lead metal mobilization
in the environment. In particular, PbO particles, a model lead-containing
compound due to its widespread presence as a component of lead paint
and as naturally occurring minerals, massicot, and litharge, are exposed
to nitrogen dioxide at different relative humidity. X-ray photoelectron
spectroscopy (XPS) shows that upon exposure to nitrogen dioxide the
surface of PbO particles reacts to form adsorbed nitrates and lead
nitrate thin films with the extent of nitrate formation relative humidity
dependent. NO<sub>2</sub>-exposed PbO particles are found to have
an increase in the amount of lead that dissolves in aqueous suspensions
at circumneutral pH compared to particles not exposed. These results
point to the potential importance and impact that heterogeneous chemistry
with trace atmospheric gases can have on increasing solubility and
therefore the mobilization of heavy metals, such as lead, in the environment.
This study also shows that surface intermediates that form, such as
adsorbed lead nitrates, can yield higher concentrations of lead in
water systems. These water systems can include drinking water, groundwater,
estuaries, and lakes
Surface Chemistry of α-FeOOH Nanorods and Microrods with Gas-Phase Nitric Acid and Water Vapor: Insights into the Role of Particle Size, Surface Structure, and Surface Hydroxyl Groups in the Adsorption and Reactivity of α-FeOOH with Atmospheric Gases
In this study, heterogeneous interactions of H<sub>2</sub>O and
HNO<sub>3</sub> on goethite, α-FeOOH, a component of mineral
dust aerosol, are investigated with simultaneous QCM measurements
and ATR-FTIR spectroscopy. Laboratory synthesized α-FeOOH of
varying sizes (microrods and nanorods) when exposed to gas phase H<sub>2</sub>O and HNO<sub>3</sub> results in the uptake of these gases.
This combined approach of QCM measurements and ATR-FTIR spectroscopy
allows for both quantification of the amount of uptake and spectroscopic
data that provides information on speciation of adsorbed products.
The results show that, in the case of H<sub>2</sub>O, both microrods
and nanorods take up water and that the total amounts of water, when
normalized to surface area, are similar. However, for HNO<sub>3</sub> uptake, the saturation coverage of total and irreversibly bound
HNO<sub>3</sub> on microrods was observed to be higher than that on
nanorods, a size effect which is attributed to surface structural
changes that occur as a function of particle size. Furthermore, an
investigation of the behavior of nitric acid reacted with α-FeOOH
in aqueous media was carried out such as to better understand the
effects of atmospheric processing upon dispersal within the hydrosphere
Fate, Transformation, and Toxicological Impacts of Pharmaceutical and Personal Care Products in Surface Waters
With the growth of the human population, a greater quantity of pharmaceutical and personal care products (PPCPs) have been released into the environment. Although research has addressed the levels and the impact of PPCPs in the environment, the fate of these compounds in surface waters is neither well known nor characterized. In the environment, PPCPs can undergo various transformations that are critically dependent on environmental factors such as solar radiation and the presence of soil particles. Given that the degradation products of PPCPs are poorly characterized, these âsecondary residuesâ can be a significant environmental health hazard due to their drastically different toxicologic effects when compared with the parent compounds. To better understand the fate of PPCPs, we studied the degradation of selected PPCPs, including ibuprofen and clofibric acid, in aqueous solutions that contained kaolinite clay and were irradiated with a solar simulator. The most abundant degradation products were identified and assessed for their toxicologic impact on selected microorganisms. The degraded mixtures showed lower toxicity than the starting compounds; however, as these degradation products are capable of further transformation and interaction with other PPCPs in natural waters, our work highlights the importance of additionally characterizing the PPCP degradation products
Surface Photochemistry of Adsorbed Nitrate: The Role of Adsorbed Water in the Formation of Reduced Nitrogen Species on 뱉Fe<sub>2</sub>O<sub>3</sub> Particle Surfaces
The surface photochemistry of nitrate,
formed from nitric acid
adsorption, on hematite (α-Fe<sub>2</sub>O<sub>3</sub>) particle
surfaces under different environmental conditions is investigated
using X-ray photoelectron spectroscopy (XPS). Following exposure of
α-Fe<sub>2</sub>O<sub>3</sub> particle surfaces to gas-phase
nitric acid, a peak in the N1s region is seen at 407.4 eV; this binding
energy is indicative of adsorbed nitrate. Upon broadband irradiation
with light (λ > 300 nm), the nitrate peak decreases in intensity
as a result of a decrease in adsorbed nitrate on the surface. Concomitant
with this decrease in the nitrate coverage, there is the appearance
of two lower binding energy peaks in the N1s region at 401.7 and 400.3
eV, due to reduced nitrogen species. The formation as well as the
stability of these reduced nitrogen species, identified as NO<sup>â</sup> and N<sup>â</sup>, are further investigated
as a function of water vapor pressure. Additionally, irradiation of
adsorbed nitrate on α-Fe<sub>2</sub>O<sub>3</sub> generates
three nitrogen gas-phase products including NO<sub>2</sub>, NO, and
N<sub>2</sub>O. As shown here, different environmental conditions
of water vapor pressure and the presence of molecular oxygen greatly
influence the relative photoproduct distribution from nitrate surface
photochemistry. The atmospheric implications of these results are
discussed
Characterization and Toxicity Analysis of Lab-Created Respirable Coal Mine Dust from the Appalachians and Rocky Mountains Regions
Coal mine workers are continuously exposed to respirable coal mine dust (RCMD) in workplaces, causing severe lung diseases. RCMD characteristics and their relations with dust toxicity need further research to understand the adverse exposure effects to RCMD. The geographic clustering of coal workers’ pneumoconiosis (CWP) suggests that RCMD in the Appalachian region may exhibit more toxicity than other geographic regions such as the Rocky Mountains. This study investigates the RCMD characteristics and toxicity based on geographic location. Dissolution experiments in simulated lung fluids (SLFs) and in vitro responses were conducted to determine the toxicity level of samples collected from five mines in the Rocky Mountains and Appalachian regions. Dust characteristics were investigated using Fourier-transform infrared spectroscopy, scanning electron microscopy, the BET method, total microwave digestion, X-ray diffraction, and X-ray photoelectron spectroscopy. Inductively coupled plasma mass spectrometry was conducted to determine the concentration of metals dissolved in the SLFs. Finer particle sizes and higher mineral and elemental contents were found in samples from the Appalachian regions. Si, Al, Fe, Cu, Sr, and Pb were found in dissolution experiments, but no trends were found indicating higher dissolutions in the Appalachian region. In vitro studies indicated a proinflammatory response in epithelial and macrophage cells, suggesting their possible participation in pneumoconiosis and lung diseases development
Characterization and Toxicity Analysis of Lab-Created Respirable Coal Mine Dust from the Appalachians and Rocky Mountains Regions
Coal mine workers are continuously exposed to respirable coal mine dust (RCMD) in workplaces, causing severe lung diseases. RCMD characteristics and their relations with dust toxicity need further research to understand the adverse exposure effects to RCMD. The geographic clustering of coal workersâ pneumoconiosis (CWP) suggests that RCMD in the Appalachian region may exhibit more toxicity than other geographic regions such as the Rocky Mountains. This study investigates the RCMD characteristics and toxicity based on geographic location. Dissolution experiments in simulated lung fluids (SLFs) and in vitro responses were conducted to determine the toxicity level of samples collected from five mines in the Rocky Mountains and Appalachian regions. Dust characteristics were investigated using Fourier-transform infrared spectroscopy, scanning electron microscopy, the BET method, total microwave digestion, X-ray diffraction, and X-ray photoelectron spectroscopy. Inductively coupled plasma mass spectrometry was conducted to determine the concentration of metals dissolved in the SLFs. Finer particle sizes and higher mineral and elemental contents were found in samples from the Appalachian regions. Si, Al, Fe, Cu, Sr, and Pb were found in dissolution experiments, but no trends were found indicating higher dissolutions in the Appalachian region. In vitro studies indicated a proinflammatory response in epithelial and macrophage cells, suggesting their possible participation in pneumoconiosis and lung diseases development