Structured Ethical Review for Wastewater-Based Testing in Support of Public Health.

Wastewater-based testing (WBT) for SARS-CoV-2 has rapidly expanded over the past three years due to its ability to provide a comprehensive measurement of disease prevalence independent of clinical testing. The development and simultaneous application of WBT measured biomarkers for research activities and for the pursuit of public health goals, both areas with well-established ethical frameworks. Currently, WBT practitioners do not employ a standardized ethical review process, introducing the potential for adverse outcomes for WBT professionals and community members. To address this deficiency, an interdisciplinary workshop developed a framework for a structured ethical review of WBT. The workshop employed a consensus approach to create this framework as a set of 11 questions derived from primarily public health guidance. This study retrospectively applied these questions to SARS-CoV-2 monitoring programs covering the emergent phase of the pandemic (3/2020-2/2022 (n = 53)). Of note, 43% of answers highlight a lack of reported information to assess. Therefore, a systematic framework would at a minimum structure the communication of ethical considerations for applications of WBT. Consistent application of an ethical review will also assist in developing a practice of updating approaches and techniques to reflect the concerns held by both those practicing and those being monitored by WBT supported programs.

Structured Ethical Review for Wastewater-Based Testing.

Wastewater-based testing (WBT) for SARS-CoV-2 has rapidly expanded over the past three years due to its ability to provide a comprehensive measurement of disease prevalence independent of clinical testing. The development and simultaneous application of the field blurred the boundary between measuring biomarkers for research activities and for pursuit of public health goals, both areas with well-established ethical frameworks. Currently, WBT practitioners do not employ a standardized ethical review process (or associated data management safeguards), introducing the potential for adverse outcomes for WBT professionals and community members. To address this deficiency, an interdisciplinary group developed a framework for a structured ethical review of WBT. The workshop employed a consensus approach to create this framework as a set of 11-questions derived from primarily public health guidance because of the common exemption of wastewater samples to human subject research considerations. This study retrospectively applied the set of questions to peer- reviewed published reports on SARS-CoV-2 monitoring campaigns covering the emergent phase of the pandemic from March 2020 to February 2022 (n=53). Overall, 43% of the responses to the questions were unable to be assessed because of lack of reported information. It is therefore hypothesized that a systematic framework would at a minimum improve the communication of key ethical considerations for the application of WBT. Consistent application of a standardized ethical review will also assist in developing an engaged practice of critically applying and updating approaches and techniques to reflect the concerns held by both those practicing and being monitored by WBT supported campaigns. Synopsis: Development of a structured ethical review facilitates retrospective analysis of published studies and drafted scenarios in the context of wastewater-based testing.

Air quality impacts in the vicinity of a chemical herder mediated in-situ burn for Arctic oil spill response.

Chemical herder augmented in-situ burning (ISB) is one of the most viable oil spill response techniques in partially ice-covered waters. Herein we report on the impacts of herder-mediated ISB tests on ambient air quality by making atmospheric measurements during ISB field tests in partially ice-covered waters in Fairbanks, Alaska. Concentrations of PM2.5, six combustion gases (CO, CO2, NO, NO2, NOx, SO2), volatile organic compounds (VOCs), and herding agent (OP-40) in the airborne plume (6-12 m downwind) were measured during three ISB events. PM2.5 concentrations significantly (p-value = 0.8014) exceeded NAAQS (24 h) exposure limits, while the remaining pollutants were found significantly (p-value <0.05) below the established exposure limits. OP-40 herder was not detected in the collected aerosol samples. To our knowledge, this is the first study on atmospheric emissions in the vicinity of a field-scale herder-augmented oil-spill ISB study in a high-latitude Arctic environment and provides information that is helpful to ensure the safety and well-being of on-site response personnel.

Review of chemical pretreatment of lignocellulosic biomass using low-liquid and low-chemical catalysts for effective bioconversion.

Chemical pretreatment of lignocellulosic biomass (LCB) is essential for effective biological conversion in subsequent steps to produce biofuels or biochemicals. For effective pretreatment, high lignin content and its recalcitrant nature of LCB are major factors influencing bioconversion, especially lignin is known to be effectively solubilized by alkaline, organic, and deep eutectic solvents, ionic liquids, while hemicellulose is effectively dissolved by various acid catalysts and organic solvents. Depending on the pretreatment method/catalyst used, different pretreatment process scheme should be applied with different amounts of catalyst and water inputs to achieve a satisfactory effect. In addition, the amount of processing water required in the following processes such as washing, catalyst recovery, and conditioning after pretreatment is critical factor for scale-up (commercialization). In this review, the amount of catalyst and/or water used, and the effect of pretreatment, properties of the products, and recovery of liquid are also discussed.

Monkeypox outbreak: Wastewater and environmental surveillance perspective.

Monkeypox disease (MPXD), a viral disease caused by the monkeypox virus (MPXV), is an emerging zoonotic disease endemic in some countries of Central and Western Africa but seldom reported outside the affected region. Since May 2022, MPXD has been reported at least in 74 countries globally, prompting the World Health Organization to declare the MPXD outbreak a Public Health Emergency of International Concern. As of July 24, 2022; 92 % (68/74) of the countries with reported MPXD cases had no historical MPXD case reports. From the One Health perspective, the spread of MPXV in the environment poses a risk not only to humans but also to small mammals and may, ultimately, spread to potent novel host populations. Wastewater-based surveillance (WBS) has been extensively utilized to monitor communicable diseases, particularly during the ongoing COVID-19 pandemic. It helped in monitoring infectious disease caseloads as well as specific viral variants circulating in communities. The detection of MPXV DNA in lesion materials (e.g. skin, vesicle fluid, crusts), skin rashes, and various body fluids, including respiratory and nasal secretions, saliva, urine, feces, and semen of infected individuals, supports the possibility of using WBS as an early proxy for the detection of MPXV infections. WBS of MPXV DNA can be used to monitor MPXV activity/trends in sewerage network areas even before detecting laboratory-confirmed clinical cases within a community. However, several factors affect the detection of MPXV in wastewater including, but not limited to, routes and duration time of virus shedding by infected individuals, infection rates in the relevant affected population, environmental persistence, the processes and analytical sensitivity of the used methods. Further research is needed to identify the key factors that impact the detection of MPXV biomarkers in wastewater and improve the utility of WBS of MPXV as an early warning and monitoring tool for safeguarding human health. In this review, we shortly summarize aspects of the MPXV outbreak relevant to wastewater monitoring and discuss the challenges associated with WBS.

In Situ Burning for Oil Spill Response in the Arctic: Recovery and Quantification of Chemical Herding Agent OP-40 from Burned Oil Residues.

In situ burning (ISB) aided by OP-40 is one of the best suited and effective oil spill response techniques for Arctic conditions. However, the fate of OP-40 in the environment after an ISB event is not fully understood, especially the amount of OP-40 remaining within the burned oil residues. Previous studies reported partial accumulation of OP-40 in water, and no OP-40 was measured in the air emissions following the burn. Accumulation of OP-40 in burned oil residues is not appropriately quantified as it is challenging to process and analyze burned oil samples in the laboratory, and there exists no standard method in the literature to measure and quantify OP-40 in burned residues. In this work, we report on the development of an analytical method for the quantification of OP-40 in burned oil residues using column chromatography, followed by gas chromatography-mass spectrometry analysis which was successfully employed to measure more than 90% of the applied OP-40 in the burned residues for controlled bench-scale burns. Additionally, the robustness of the developed method was further tested by measuring OP-40 in burn residues from ISBs conducted at different oil-water emulsion ratios (60-100% oil) and water temperatures (4-35 °C), wherein known amounts of OP-40 were added to the residues. Results indicate that the method is equally effective for different oil-water emulsions, but the OP-40 recoveries (89.2-115.6%) are significantly higher at warmer temperatures than the OP-40 recoveries (87.0-103.3%) at colder temperatures. Overall, the method developed in this work could assist in the understanding of the fate of OP-40 in a potentially important environmental matrix of burned oil residues that are left behind sometimes long (weeks to years) after an ISB event.

Enrichment of psychrophilic and acidophilic sulfate-reducing bacterial consortia - a solution toward acid mine drainage treatment in cold regions.

Failure of sulfate-reducing bacteria (SRB)-mediated treatment of acid mine drainage (AMD) in cold regions due to inhibition of bacteria by acidic pH and low temperature can be overcome by enriching psychrophilic and acidophilic microbial consortia from local metal-rich sediments. In this study, we enriched microbial consortia from Arctic mine sediments at varying pH (3-7) and temperatures (15-37 °C) under anaerobic conditions with repeated sub-culturing in three successive stages, and analyzed the microbial community using 16S rRNA gene sequencing. The enriched SRB genera resulted in high sulfate reduction (85-88%), and significant metal removal (49-99.9%) during the initial stages (stage 1 and 2). Subsequently, sub-culturing the inoculum at pH 3-4.5 resulted in lower sulfate reduction (9-34%) due to the inhibition of SRB by accumulated acetic acid (0.3-9 mM). The microbial metabolic interactions for successful sulfate and metal removal involved initial glycerol co-fermentation to acetic acid at acidic pH (by Desulfosporosinus, Desulfotomaculum, Desulfurospora, and fermentative bacteria including Cellulomonas and Anaerovorax), followed by acetic acid oxidation to CO2 and H2 (by Desulfitobacterium) at neutral pH, and subsequent H2 utilization (by Desulfosporosinus). The results, including the structural and functional properties of enriched microbial consortia, can inform the development of effective biological treatment strategies for AMD in cold regions.

Adsorptive Removal of Se(IV) by Citrus Peels: Effect of Adsorbent Entrapment in Calcium Alginate Beads.

Selenium (Se) contamination in natural waters impacted by anthropogenic activities is becoming a prevalent and widespread problem. Investigation of novel, low-cost, and sustainable food-waste-sourced adsorbents for Se removal has largely been unexplored. Here, we report on the Se(IV) biosorption from a liquid solution using three waste-derived/low-cost biosorbents, namely citrus peels (bare), Ca-alginate gel beads, and Ca-alginate-citrus peels composite beads (Ca-alginate@citrus). The entrapment of citrus peels by Ca-alginate not only provided a structural framework for the citrus peel particles but also preserved the high-efficiency Se(IV) removal property of the citrus peels. From the modeling results, it was established that Se(IV) biosorption followed the fixed-film diffusion model, along with pseudo-second-order kinetics. Investigation of pH impacts along with initial dosing of sorbent/sorbate demonstrated that all of the three biosorbents exhibited optimum biosorption of Se(IV) at pH 6-8, 50-75 mg·L-1 of Se(IV), and 1-5 mg·L-1 of biosorbent. Overall, the maximum Se(IV) biosorption capacities were measured to be 116.2, 72.1, and 111.9 mg·g-1 for citrus peels, Ca-alginate, and Ca-alginate@citrus, respectively, with citrus peels (bare and immobilized) showing among the highest reported values in the literature for Se(IV) adsorption. This work provides a platform for the future development of an efficient filtration system using Ca-alginate@citrus as an inexpensive, novel, and sustainable biosorbent to treat Se(IV) contaminated water.

Rapid immobilization of viable Bacillus pseudomycoides in polyvinyl alcohol/glutaraldehyde hydrogel for biological treatment of municipal wastewater.

A new approach for easy synthesis of Bacillus pseudomycoides immobilized polyvinyl alcohol (PVA)/glutaraldehyde (GA) hydrogel for application in a wastewater treatment system is reported. Optimization studies revealed that GA/PVA mass ratio of 0.03 and acidic pH of 2 were required for hydrogel synthesis and eventually for bacterial cell immobilization. The synthesized crosslinked matrix possessed a pore size suitable for microbial cell entrapment while maintaining cell accessibility to external environment for bioremediation. Possible crosslinking and bacterial cell immobilization in the hydrogel were evidenced by FTIR, XRD, and SEM studies, respectively. Further, the extent of crosslinking of GA with PVA was investigated and confirmed by transmittance and permeability experiments. The viability and proliferation of hydrogel embedded cells (after 25 days) was confirmed by confocal fluorescence microscopy which also indicated that acidic pH of polymer solution did not affect the immobilized live cells. B. pseudomycoides immobilized hydrogel were demonstrated to be effective for treatment of municipal wastewater and reduced biochemical oxygen demand (BOD), chemical oxygen demand (COD), and protein content below the recommended levels. Overall, the results from this bench-scale work show that employing bacteria-embedded PVA/GA hydrogel for the treatment of municipal wastewater yield promising results which should be further explored in pilot/field-scale studies.

Water quality and associated microbial ecology in selected Alaska Native communities: Challenges in off-the-grid water supplies.

The availability of safe water for potable purposes in Alaska Native communities is limited due to naturally occurring metals and contaminants released from anthropogenic activities, such as drilling and mining. The impacts of climate change are magnified in the arctic and sub-arctic regions and thus have the potential to mobilize contaminants and exacerbate the water contamination problem. Alaska Native communities are vulnerable to such changes in their water quality because of their remote location and limited access to resources. This study initiates an assessment of water quality, including its microbial ecology, in off-the-grid Alaskan water supplies (i.e., primarily groundwater wells). In particular, water quality data were collected from nine communities (22 ground water wells). Water quality analyses included basic water quality parameters, a suite of metals relevant to human health, and microbial community composition. Results revealed location-specific elevated arsenic concentrations based on the underlying geological formation, particularly in the areas located in the geological formation of the McHugh Complex. Diverse microbial communities were observed, and the grouping appeared to be based on elevation. These findings present evidence of compromised water quality in an understudied area in the United States. The results from this study should be considered as a snapshot in time, which highlight the importance for further systematic studies in similar off-the-grid communities.

MicroFEWs: A Food-Energy-Water Systems Approach to Renewable Energy Decisions in Islanded Microgrid Communities in Rural Alaska.

In recent years, there has been increased recognition of the importance of a nexus approach to optimize food, energy, and water (FEW) security at regional and global scales. Remote communities in the Arctic and Subarctic regions in Alaska provide unique examples of closed and isolated systems, wherein the FEW nexus not only needs to be examined to lend resilience to these vulnerable communities but that could also serve as small-scale test beds for a wider and systematic understanding of the FEW nexus. In this short communication, looking at the FEW nexus in Cordova, Alaska, through an energy lens, we introduce an approach (referred to as the "MicroFEWs approach") that may assist remote communities in Alaska in making informed decisions regarding the use of renewable energy to increase FEW security. Our example uses the MicroFEWs approach to assess the impacts of increased renewable energy generation on FEW security in the community, more specifically to food security through potential changes to the community's fish processing industry. This approach can serve as a basis for investigating the FEW nexus in varying contexts and locales.

In-situ burning with chemical herders for Arctic oil spill response: Meta-analysis and review.

With increased oil exploration and marine activity in the warming Arctic, there is an increased risk of future oil spills in the Arctic region. In-situ burning (ISB), along with the use of chemical herders (to thicken the slick of spilled oil) has emerged as a potentially viable oil-spill response technique for various Arctic scenarios. The purpose of this research review is to document the field use, research, and analysis regarding the use of ISB to address an offshore oil spill response in the Arctic, with a specific focus on the use of chemical herders to aid ISB in Arctic waters. The compilation of this work involved a systematic review of available experimental data, studies on actual spill-response events, and resulting recommendations on this topic. Both peer-reviewed and available gray literature from the early 1970s through 2018 were evaluated. Selection criteria centered on herders for use with ISBs, Arctic conditions as they relate to ISB, and operational windows of opportunity and environmental risk for this type of oil spill response. From the available literature, more than a hundred articles are referenced herein, and annotated summaries provided. There is general agreement that ISB should be classified as a viable response option for the Arctic offshore to be implemented as part of a multi-layered approach (ASTM 2014; Fritt-Rasmussen et al. 2017; NRC 2014; Rolandsen 2018). In addition, there continue to be gaps noted concerning the availability of monitoring/surveillance personnel and equipment, and logistical/safety considerations for working in the Arctic, as well as specific information on the fate and potential impact of herders and burn residue on Arctic receptors (NRC 2014; Nuka 2016; US-DOI and USGS 2011). This review provides background information for researchers, responders, decision-makers, communities, and is a resource when developing and approving an oil spill response plan or planning future research which includes the use of ISB and herders.

Removal of Arsenic(III) from Aqueous Solution Using Metal Organic Framework-Graphene Oxide Nanocomposite.

MIL-53(Al)-graphene oxide (GO) nanocomposites of different GO to MIL-53(Al) mass ratios (1% to 25% GO) were synthesized and tested for removal of arsenite (As(III)), which is a well-known groundwater contaminant. The properties of MIL-53(Al)-GO nanocomposites were characterized using X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) Spectroscopy, Brunauer-Emmett-Teller (BET) surface area measurements, and Scanning Electron Microscopy (SEM). Batch experiments were performed on MIL-53(Al)-GO nanocomposites for As(III) adsorption in aqueous solutions to investigate adsorption kinetics and isotherm behavior under varying environmental conditions. The effects of solution pH (2 to 11), initial As(III) concentrations (10⁻110 mg/L), adsorbent dosage (0.2⁻3.0 g/L), and temperature (298⁻318 K) on As(III) adsorption were investigated. MIL-53(Al)-GO nanocomposites showed higher adsorption of As(III) than pristine MIL-53(Al) and GO individually. As (III) removal was optimized at a ratio of 3% GO in the MIL-53(Al)-GO nanocomposite, with an adsorption capacity of 65 mg/g. The adsorption kinetics and isotherms followed pseudo-second-order and Langmuir isotherm models, respectively. Overall, these results suggest that MIL-53(Al)-GO nanocomposite holds a significant promise for use in the remediation of As (III) from groundwater and other aqueous solutions.

Effects of Chloramine and Coupon Material on Biofilm Abundance and Community Composition in Bench-Scale Simulated Water Distribution Systems and Comparison with Full-Scale Water Mains.

The vast majority of bacteria in drinking water distribution systems (DWDSs) reside in biofilms on the interior walls of water mains. Little is known about how water quality conditions affect water-main biofilms because of the inherent limitations in experimenting with drinking water supplies and accessing the water mains for sampling. Bench-scale reactors permit experimentation and ease of biofilm sampling, yet questions remain as to how well biofilms in laboratory reactors represent those on water mains. In this study, the effects of DWDS pipe materials and chloramine residual on biofilms were investigated by cultivating biofilms on cement, polyvinyl chloride, and high density polyethylene coupons in CDC reactors for up to 28 months in the presence of chloraminated or dechlorinated tap water. The bench-scale biofilm microbiomes were then compared with the microbiome on a water main from the full-scale system that supplied the water to the reactors. The presence of a chloramine residual (1.74 ± 0.21 mg/L) suppressed biofilm accumulation and selected for Mycobacterium-like and Sphingopyxis-like operational taxonomic units (OTUs) while the destruction of the chloramine residual resulted in a significant increase in biomass quantity and a shift toward a more diverse community dominated by Nitrospira-like OTUs, which, our results suggest, may be complete ammonia oxidizers (comammox). Coupon material, however, had a relatively minor effect on the abundance and community composition of the biofilm bacteria. Although biofilm communities from the chloraminated water reactor and the water mains shared some dominant populations (namely, Mycobacterium- and Nitrosomonas-like OTUs), the communities were significantly different. This manuscript provides novel insights into the effects of dechlorination and pipe material on biofilm community composition. Furthermore, to our knowledge, it is the first study to compare biofilm in a tap water-fed, bench-scale simulated distribution system to biofilm on water mains from the full-scale system supplying the tap water.

Factors impacting the interactions of engineered nanoparticles with bacterial cells and biofilms: Mechanistic insights and state of knowledge.

Since their advent a few decades ago, engineered nanoparticles (ENPs) have been extensively used in consumer products and industrial applications and their use is expected to continue at the rate of thousands of tons per year in the next decade. The widespread use of ENPs poses a potential risk of large scale environmental proliferation of ENPs which can impact and endanger environmental health and safety. Recent studies have shown that microbial biofilms can serve as an important biotic component for partitioning and perhaps storage of ENPs released into aqueous systems. Considering that biofilms can be one of the major sinks for ENPs in the environment, and that the field of biofilms itself is only three to four decades old, there is a recent and growing body of literature investigating the ENP-biofilm interactions. While looking at biofilms, it is imperative to consider the interactions of ENPs with the planktonic microbial cells inhabiting the bulk systems in the vicinity of surface-attached biofilms. In this review article, we attempt to establish the state of current knowledge regarding the interactions of ENPs with bacterial cells and biofilms, identifying key governing factors and interaction mechanisms, as well as prominent knowledge gaps. Since the context of ENP-biofilm interactions can be multifarious-ranging from ecological systems to water and wastewater treatment to dental/medically relevant biofilms- and includes devising novel strategies for biofilm control, we believe this review will serve an interdisciplinary audience. Finally, the article also touches upon the future directions that the research in the ENP-microbial cells/biofilm interactions could take. Continued research in this area is important to not only enhance our scientific knowledge and arsenal for biofilm control, but to also support environmental health while reaping the benefits of the 'nanomaterial revolution'.

Scale-up considerations for surface collecting agent assisted in-situ burn crude oil spill response experiments in the Arctic: Laboratory to field-scale investigations.

In the event of a marine oil spill in the Arctic, government agencies, industry, and the public have a stake in the successful implementation of oil spill response. Because large spills are rare events, oil spill response techniques are often evaluated with laboratory and meso-scale experiments. The experiments must yield scalable information sufficient to understand the operability and effectiveness of a response technique under actual field conditions. Since in-situ burning augmented with surface collecting agents ("herders") is one of the few viable response options in ice infested waters, a series of oil spill response experiments were conducted in Fairbanks, Alaska, in 2014 and 2015 to evaluate the use of herders to assist in-situ burning and the role of experimental scale. This study compares burn efficiency and herder application for three experimental designs for in-situ burning of Alaska North Slope crude oil in cold, fresh waters with ∼10% ice cover. The experiments were conducted in three project-specific constructed venues with varying scales (surface areas of approximately 0.09 square meters, 9 square meters and 8100 square meters). The results from the herder assisted in-situ burn experiments performed at these three different scales showed good experimental scale correlation and no negative impact due to the presence of ice cover on burn efficiency. Experimental conclusions are predominantly associated with application of the herder material and usability for a given experiment scale to make response decisions.

Feasibility of using a particle counter or flow-cytometer for bacterial enumeration in the assimilable organic carbon (AOC) analysis method.

Assimilable organic carbon (AOC) is one of the major determinants of microbial growth and stability in drinking water distribution systems. Nevertheless, AOC measurements are rarely conducted in practice owing, in part, to the tedious and time-consuming nature of the bioassay. Herein, we compared three alternative cell count approaches [flow cytometry with staining (FC-S), flow cytometry without staining (FC-NS), and particle counting (Coulter counter; CC)] for bacterial enumeration as a means to expedite the AOC bioassay. Our results suggest that of the three methods only FC-S provides a suitable alternative to plate counting for rapid and accurate enumeration of both P17 and NOX in the AOC bioassay. While the cell counts obtained by FC-NS were linearly correlated with those obtained using the traditional heterotrophic plate count (HPC) method (FC-NS: R(2) = 0.89-0.96), the AOC values obtained by FC-NS were overestimated by 18-57 %. The CC approach was unsuccessful in enumerating Spirillum strain NOX cells because of the relatively small size of that organism. The CC counts were linearly correlated with HPC for Pseudomonas fluorescens strain P-17 (P17) cells (R(2) = 0.83) but like FC-NS, the CC approach also overestimated the AOC values (for P-17). The advantage of the FC-S method over the other two is improved sensitivity and the ability to specifically enumerate whole cells (and likely viable) as opposed to non-viable cells, cell debris, and other contaminating particles introduced by the test water itself or sample handling.

Biofilm Cohesive Strength as a Basis for Biofilm Recalcitrance: Are Bacterial Biofilms Overdesigned?

Bacterial biofilms are highly resistant to common antibacterial treatments, and several physiological explanations have been offered to explain the recalcitrant nature of bacterial biofilms. Herein, a biophysical aspect of biofilm recalcitrance is being reported on. While engineering structures are often overdesigned with a factor of safety (FOS) usually under 10, experimental measurements of biofilm cohesive strength suggest that the FOS is on the order of thousands. In other words, bacterial biofilms appear to be designed to withstand extreme forces rather than typical or average loads. In scenarios requiring the removal or control of unwanted biofilms, this emphasizes the importance of considering strategies for structurally weakening the biofilms in conjunction with bacterial inactivation.

Effect of strain rate on the mechanical properties of Staphylococcus epidermidis biofilms.

The quantification of biofilm mechanical properties can serve as a basis for understanding biofilm resilience and for developing biofilm control strategies. One aspect of tensile testing that is likely to be important for a viscoelastic material such as bacterial biofilm, but unfortunately is often overlooked (i.e., not controlled or reported), is the strain rate used during testing. Thus, we performed tensile testing on intact S. epidermidis biofilms using the microcantilever method at 12 strain rate values ranging over approximately 3 orders of magnitude (0.013-9.07 s(-1)). Ultimate or cohesive strength, elastic modulus, and toughness increased with increasing strain rate and approached a plateau at approximately 1.3 s(-1). Failure strain, on the other hand, did not exhibit any trend with strain rate. Given that the mean values of some parameters increased by as much as 1 order of magnitude over the strain rate range used in this work, we suggest that the strain rate during tensile testing should be carefully controlled and reported to facilitate comparisons among different studies. Furthermore, the quantitative expressions developed in this work that relate mechanical property values with strain rate may be useful for modeling the deformation of bacterial biofilms under applied loads.

Real-time prediction of size-resolved ultrafine particulate matter on freeways.

Ultrafine particulate matter (UFP; diameter <0.1 µm) concentrations are relatively high on the freeway, and time spent on freeways can contribute a significant fraction of total daily UFP exposure. We model real-time size-resolved UFP concentrations in summer time on-freeway air. Particle concentrations (32 bins, 5.5 to 600 nm) were measured on Minnesota freeways during summer 2006 and 2007 ( Johnson, J. P.; Kittelson, D. B.; Watts, W. F. Environ. Sci. Technol. 2009 , 43 , 5358 - 5364 ). Here, we develop and apply two-way stratified multilinear regressions, using an approach analogous to mobile-monitoring land-use regression but using real-time meteorological and traffic data. Our models offer the strongest predictions in the 10-100 nm size range (adj-R(2): 0.79-0.89, average adj-R(2): 0.85) and acceptable but weaker predictions in the 130-200 nm range (adj-R(2): 0.41-0.62, average adj-R(2): 0.52). The aggregate model for total particle counts performs well (adj-R(2) = 0.77). Bootstrap resampling (n = 1000) indicates that the proposed models are robust to minor perturbations in input data. The proposed models are based on readily available real-time information (traffic and meteorological parameters) and can thus be exploited to offer spatiotemporally resolved prediction of UFPs on freeways within similar geographic and meteorological environments. The approach developed here provides an important step toward modeling population exposure to UFP.