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This study aimed to determine the tolerance of Chromobacterium violaceum ATCC 12472 to diesel. The growth of the strain was evaluated through exposure to various diesel concentrations (1, 2.5, 5, 7.5, and 10% v/v), with continuous monitoring of growth via optical density measurements until the death phase was reached. Employing a logistic model, we analyzed the growth kinetics of C. violaceum and compared them with five other models to comprehend substrate utilization dynamics. Our results indicate that optimal bacterial growth occurred at 2.5% (v/v) or 18,125 mg/L diesel, while both higher and lower concentrations manifested inhibitory and increasingly stressful effects. The Aiba model emerged as the most fitting representation of substrate utilization by C. violaceum. In addition, our findings underscore the remarkable diesel tolerance of C. violaceum ATCC 12472, despite the inherently stressful nature of the medium. This study contributes to the understanding of microbial responses to environmental stressors and highlights the pivotal role of the substrate concentration in influencing microbial growth. These insights have implications for bioremediation strategies and enhance our understanding of bacterial ecological resilience in the presence of hydrocarbon pollutants.

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Commuters are often exposed to higher concentrations of air pollutants due to its proximity to mobile sources. Despite recent trends in urban transport toward zero- and low-tailpipe emission alternatives, the assessments of the impact of these transformations on commuter exposure are limited by the low frequency of such studies. In this work, we use a unique data set of personal exposure concentration measurements collected over the span of 5 years to analyze changes due to the introduction of a new fleet for Bogotá's Bus Rapid Transit System. In that system, over a thousand Euro-II and -III diesel-powered buses were replaced with Euro-VI compressed natural gas and filter-equipped Euro-V diesel buses. We measured personal exposure concentrations of equivalent black carbon (eBC), fine particulate (PM2.5), and ultra fine particles (UFP) during and after the retirement of old buses and the introduction of new ones. Observations collected prior to the fleet renewal were used as baseline and later compared to data collected over two follow-up campaigns in 2019 and 2020. Significant reductions in the concentration of PM2.5 and eBC were observed during the 2019 campaign, with a 48% decrease for mean in-bus eBC (89.9 to 46.4 µg m-3) and PM2.5 (180.7 to 95.4 µg m-3) concentrations. Further reductions were observed during the 2020 follow-up, when the fleet renovation was completed, with mean in-bus eBC decreasing to 17.7 µg m-3 and PM2.5 to 42.3 µg m-3. These observations imply nearly a 5-fold reduction in eBC exposure and a 4-fold decrease in PM2.5. There was a much smaller reduction of in-bus UFP concentration between 2019 and 2020, indicating a persistent presence of high particle number concentrations in the near-road environment despite the fleet renovation process. In-bus UFP concentrations ranged between 65 000 and 104 500 cm-3 during the follow-up campaigns. The results in this work illustrate the immediate benefits of reducing personal exposure through the adoption of vehicles with more stringent emission standards.

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One of the largest rail yard facilities in the Southeastern US, the Inman and Tilford yards, is located in the northwestern section of Atlanta, Georgia alongside other industries, schools, businesses, and dwellings. It is a significant source of fine particulate (PM2.5) and black carbon (BC) (Galvis, Bergin, & Russell, 2013). We calculate 2011 PM2.5 and BC emissions from the rail yards and primary industrial and on-road mobile sources in the area and determine their impact on local air quality using Gaussian dispersion modeling. We determine the change in PM2.5 and BC concentrations that could be accomplished by upgrading traditional switcher locomotives used in these rail yards to a lower emitting technology and evaluate the health benefits for comparison with upgrade costs. Emissions from the rail yards were estimated using reported fuel consumption data (GAEPD, 2012b) and emission factors previously measured in the rail yards (Galvis et al., 2013). Model evaluation against 2011 monitoring data found agreement between measured and simulated concentrations. Model outputs indicate that the line-haul and switcher activities are responsible for increments in annual average concentrations of approximately 0.5±0.03 µg/m(3) (39%) and 0.7±0.04 µg/m(3) (56%) of BC, and for 1.0±0.1 µg/m(3) (7%) and 1.6±0.2 µg/m(3) (14%) of PM2.5 at two monitoring sites located north and south of the rail yards respectively. Upgrading the switcher locomotives at the yards with a lower emitting technology in this case "mother slug" units could decrease PM2.5 and BC emissions by about 9 and 3 t/year respectively. This will lower annual average PM2.5 concentrations between 0.3±0.1 µg/m(3) and 0.6±0.1 µg/m(3) and BC concentrations between 0.1±0.02 µg/m(3) and 0.2±0.03 µg/m(3) at monitoring sites north and south of the rail yards respectively, and would facilitate PM2.5 NAAQS attainment in the area. We estimate that health benefits of approximately 20 million dollars per year could be gained.

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Dysfunctional pulmonary homeostasis and repair, including diseases such as pulmonary fibrosis (PF), chronic obstructive pulmonary disease (COPD), and tumorigenesis have been increasing over the past decade, a fact that heavily implicates environmental influences. Several investigations have suggested that in response to increased transforming growth factor--beta (TGFß) signaling, the alveolar type II (ATII) epithelial cell undergoes phenotypic changes that may contribute to the complex pathobiology of PF. We have previously demonstrated that increased tissue stiffness associated with PF is a potent extracellular matrix (ECM) signal for epithelial cell activation of TGFß. The work reported here explores the relationship between tissue stiffness and exposure to environmental stimuli in the activation of TGFß. We hypothesized that exposure of ATII cells to fine particulate matter (PM2.5) will result in enhanced cell contractility, TGFß activation, and subsequent changes to ATII cell phenotype. ATII cells were cultured on increasingly stiff substrates with or without addition of PM2.5. Exposure to PM2.5 resulted in increased activation of TGFß, increased cell contractility, and elongation of ATII cells. Most notably, on 8 kPa substrates, a stiffness greater than normal but less than established fibrotic lung, addition of PM2.5 resulted in increased cortical cell stiffness, enhanced actin staining and cell elongation; a result not seen in the absence of PM2.5. Our work suggests that PM2.5 exposure additionally enhances the existing interaction between ECM stiffness and TGFß that has been previously reported. Furthermore, we show that this additional enhancement is likely a consequence of intracellular reactive oxygen species (ROS) leading to increased TGFß signaling events. These results highlight the importance of both the micromechanical and biochemical environment in lung disease initiation and suggest that individuals in early stages of lung remodeling during fibrosis may be more susceptible than healthy individuals when exposed to environmental injury adjuvants.

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Railyards have the potential to influence localfine particulate matter (aerodynamic diameter < or = 2.5 microm; PM2.5) concentrations through emissions from diesel locomotives and supporting activities. This is of concern in urban regions where railyards are in proximity to residential areas. Northwest of Atlanta, Georgia, Inman and Tilford railyards are located beside residential neighborhoods, industries, and schools. The PM2.5 concentrations near the railyards is the highest measured amongst the state-run monitoring sites (Georgia Environmental Protection Division, 2012; http://www.georgiaair.org/amp/report.php). The authors estimated fuel-based black carbon (BC) and PM2.5 emission factors for these railyards in order to help determine the impact of railyard activities on PM2.5 concentrations, and for assessing the potential benefits of replacing current locomotive engines with cleaner technologies. High-time-resolution measurements of BC, PM2.5, CO2, and wind speed and direction were made at two locations, north and south of the railyards. Emissions factors (i.e., the mass of BC or PM2.5 per gallon of fuel burned) were estimated by using the downwind/upwind difference in concentrations, wavelet analysis, and an event-based approach. By the authors' estimates, diesel-electric engines used in the railyards have average emission factors of 2.8 +/- 0.2 g of BC and 6.0 +/- 0.5 g of PM2.5 per gallon of diesel fuel burned. A broader mix of railyard supporting activities appear to lead to average emission factors of 0.7 +/- 0.03 g of BC and 1.5 +/- 0.1 g of PM2.5 per gallon of diesel fuel burned. Railyard emissions appear to lead to average enhancements of approximately 1.7 +/- 0.1 microg/m3 of PM2.5 and approximately 0.8 +/- 0.01 microg/m3 of BC in neighboring areas on an annual average basis. Uncertainty not quantified in these results could arise mainly from variability in downwind/upwind differences, differences in emissions of the diverse zones within the railyards, and the influence of on-road mobile source emissions.

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