Laura A. Schifman

Fourier transform infrared spectroscopy to assess molecular-level changes in microorganisms exposed to nanoparticles

Fourier transform infrared (FTIR) is a spectroscopy method that can identify variations in the total composition of microorganisms through the determination of changes in functional groups in biomolecules. FTIR measures the vibration and rotation of molecules influenced by infrared radiation at a specific wavelength. This technique allows the identification of structural changes in the molecular binding between microorganisms and metal atoms, which can provide information about the nature of their interactions. In this review article, we will describe the state of the art in current uses of FTIR for the elucidation of bacteria–nanoparticle interactions. We will describe advantages for the application of FTIR in the field of nanotoxicology, including higher signal-to-noise ratio, high energy throughput, as well as high accuracy and stability which are applicable to solid phase samples but not recommended for assays in the liquid phase. Limitations such as multiple background scans and post-processing analysis are not deniable. Comparison of FTIR with other commonly used tools such as Raman spectroscopy, mass spectrometry, nuclear magnetic resonance spectroscopy, and X-ray photoelectron spectroscopy is also discussed. Finally, we present an application of FTIR for the assessment of bacterial changes in response to the exposure to silver nanoparticles (AgNPs). The results showed that the AgNPs-induced structural changes in the peptide and amino acids region may lead to alterations of conformation and/or composition of Amid B and Amid III. These results showed that bacteria developed resistance toward AgNPs and resulted in changes in the genotype and expression in the phenotype. Here, ATR–FTIR provided the evidence of the AgNPs cytotoxicity-induced intracellular level alterations in bacteria.

New Antimicrobially Amended Media for Improved Nonpoint Source Bacterial Pollution Treatment

Nonpoint source pollution (NPS) such as stormwater runoff may introduce high loads of bacteria, impairing surface water bodies. The existing filter materials in stormwater best management practices (BMP) are typically not designed to inactivate bacteria. Herein, novel filtration media were extensively tested for microbial load reduction in stormwater runoff. Red cedar wood chips (RC) were amended with different loadings of either 3-(trihydroxysilyl) propyldimethyloctadecyl ammonium chloride (TPA) or silver nanoparticles (AgNP). Under batch conditions at 25 °C, log10 removal values (LRV) up to 3.71 ± 0.38 (mean ± standard error) for TPA-RC and 2.25 ± 1.00 for AgNP-RC were achieved for Escherichia coli (E. coli), whereas unmodified RC achieved less than 0.5 LRV. Similar trends were observed at 17.5 °C, however at low temperature (10 °C) no statistically significant difference in E. coli inactivation between modified and unmodified RC was detected. Inactivation kinetic studies show that TPA-RC has higher inactivation rate constants compared to AgNP-RC. Under dynamic flow conditions a mass balance approach indicates that even after remobilization up to 99.8% of E. coli removal using 9 mg/g TPA-RC compared to 64.8% for unmodified RC. This study demonstrates that RC wood chips amended with antimicrobial compounds show promising applications as filtration material for the reduction of microbiological contamination load in stormwater runoff.

Managing Uncertainty in Runoff Estimation with the U.S. Environmental Protection Agency National Stormwater Calculator

The U.S. Environmental Protection Agency National Stormwater Calculator (NSWC) simplifies the task of estimating runoff through a straightforward simulation process based on the EPA Stormwater Management Model. The NSWC accesses localized climate and soil hydrology data, and options to experiment with low-impact development (LID) features for parcels up to 5 ha in size. We discuss how the NSWC treats the urban hydrologic cycle and focus on the estimation uncertainty in soil hydrology and its impact on runoff simulation by comparing field-measured soil hydrologic data from 12 cities to corresponding NSWC estimates in three case studies. The default NSWC hydraulic conductivity is 10.1 mm/h, which underestimates conductivity measurements for New Orleans, Louisiana (95 ± 27 mm/h) and overestimates that for Omaha, Nebraska (3.0 ± 1.0 mm/h). Across all cities, the NSWC prediction, on average, underestimated hydraulic conductivity by 10.5 mm/h compared to corresponding measured values. In evaluating how LID interact with soil hydrology and runoff response, we found direct hydrologic interaction with pre-existing soil shows high sensitivity in runoff prediction, whereas LID isolated from soils show less impact. Simulations with LID on higher permeability soils indicate that nearly all of pre-LID runoff is treated; while features interacting with less-permeable soils treat only 50%. We highlight the NSWC as a screening-level tool for site runoff dynamics and its suitability in stormwater management.

Nanofiller Presence Enhances Polycyclic Aromatic Hydrocarbon (PAH) Profile on Nanoparticles Released during Thermal Decomposition of Nano-enabled Thermoplastics: Potential Environmental Health Implications

Nano-enabled products are ultimately destined to reach end-of-life with an important fraction undergoing thermal degradation through waste incineration or accidental fires. Although previous studies have investigated the physicochemical properties of released lifecycle particulate matter (called LCPM) from thermal decomposition of nano-enabled thermoplastics, critical questions about the effect of nanofiller on the chemical composition of LCPM still persist. Here, we investigate the potential nanofiller effects on the profiles of 16 Environmental Protection Agency (EPA)-priority polycyclic aromatic hydrocarbons (PAHs) adsorbed on LCPM from thermal decomposition of nano-enabled thermoplastics. We found that nanofiller presence in thermoplastics significantly enhances not only the total PAH concentration in LCPM but most importantly also the high molecular weight (HMW, 4-6 ring) PAHs that are considerably more toxic than the low molecular weight (LMW, 2-3 ring) PAHs. This nano-specific effect was also confirmed during in vitro cellular toxicological evaluation of LCPM for the case of polyurethane thermoplastic enabled with carbon nanotubes (PU-CNT). LCPM from PU-CNT shows significantly higher cytotoxicity compared to PU which could be attributed to its higher HMW PAH concentration. These findings are crucial and make the case that nanofiller presence in thermoplastics can significantly affect the physicochemical and toxicological properties of LCPM released during thermal decomposition.

Sleuthing Through the Rock Cycle: An Online Guided Inquiry Tool for Middle and High School Geoscience Education

ABSTRACT The rock cycle is a key component of geoscience education at all levels. In this paper, we report on a new guided inquiry curricular module, Sleuthing Through the Rock Cycle, which has a blended online/offline constructivist design with comprehensive teaching notes and has been successful in pilot use in Rhode Island middle and high school classrooms over the past 3 y. The module consists of two overarching activities: (1) SherRock Holmes and the Case of the Mystery Rock Samples, and (2) Cracking the Case of the Changing Rocks. The module encourages hands-on activities, peer collaboration, and real-time teacher review of embedded textual and reflection components. Overall, Rhode Island teachers report that the module is an outstanding teaching tool and that the associated professional development is empowering.

Widespread loss of intermediate soil horizons in urban landscapes

Significance As societies move toward nature-based infrastructure to provide ecosystem services for sustainable urban environmental management, knowledge of urban soils remains a critical gap. An 11-city comparison of urban to reference preurban soil profiles revealed how urbanization modifies the presence and ordering of soil layers and its properties. Urban soils had fewer horizons than their preurban counterparts, with a predominant absence of intermediate B horizons. The loss of B horizons, which are not easily replaced, as they form over decades to millennia, can affect ecosystem functions, with potentially wide-ranging consequences for ecosystem services in cities. Soils support terrestrial ecosystem function and therefore are critical urban infrastructure for generating ecosystem services. Urbanization processes modify ecosystem function by changing the layers of soils identified as soil horizons. Soil horizons are integrative proxies for suites of soil properties and as such can be used as an observable unit to track modifications within soil profiles. Here, in an analysis of 11 cities representing 10 of the 12 soil orders, we show that urban soils have ∼50% fewer soil horizons than preurban soils. Specifically, B horizons were much less common in urban soils and were replaced by a deepening of A horizons and a shallowing of C horizons. This shift is likely due to two processes: (i) local management, i.e., soil removal, mixing, and fill additions, and (ii) soil development timelines, i.e., urbanized soils are young and have had short time periods for soil horizon development since urbanization (decades to centuries) relative to soil formation before urbanization (centuries to millennia). Urban soils also deviated from the standard A-B-C horizon ordering at a much greater frequency than preurban soils. Overall, our finding of common shifts in urban soil profiles across soil orders and cities suggests that urban soils may function differently from their preurban antecedents. This work introduces a basis for improving our understanding of soil modifications by urbanization and its potential effects on ecosystem functioning and thereby has implications for ecosystem services derived from urban landscapes.

Synergistic effects of engineered nanoparticles and organics released from laser printers using nano-enabled toners: potential health implications from exposures to the emitted organic aerosol

Recent studies have shown that engineered nanoparticles (ENPs) are incorporated into toner powder used in printing equipment and released during their use. Thus, understanding the functional and structural composition and potential synergistic effects of this complex aerosol and released gaseous co-pollutants is critical in assessing their potential toxicological implications and risks. In this study, toner powder and PEPs were thoroughly examined for functional and molecular composition of the organic fraction and the concentration profile of 16 Environmental Protection Agency (EPA)-priority polycyclic aromatic hydrocarbons (PAH) using state of the art analytical methods. Results show significant differences in abundance of non-exchangeable organic hydrogen of toner powder and PEPs, with a stronger aromatic spectral signature in PEPs. Changes in structural composition of PEPs are indicative of radical additions and free-radical polymerization favored by catalytic reactions, resulting in formation of functionalized organic species. Particularly, accumulation of aromatic carbons with strong styrene-like molecular signatures on PEPs is associated with formation of semivolatile heavier aromatic species (i.e., PAHs). Further, the transformation of low molecular weight PAHs in the toner powder to high molecular weight PAHs in PEPs was documented and quantified. This may be a result of synergistic effects from catalytic metal/metal oxide ENPs incorporated into the toner and the presence/release of semi-volatile organic species (SVOCs). The presence of known carcinogenic PAHs on PEPs raises public health concerns and warrants further toxicological assessment.