United States Environmental Protection Agency

About: United States Environmental Protection Agency is a government organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Population & Environmental exposure. The organization has 13873 authors who have published 26902 publications receiving 1191729 citations. The organization is also known as: EPA & Environmental Protection Agency.

Survey of Culturable Airborne Bacteria at Four Diverse Locations in Oregon: Urban, Rural, Forest, and Coastal

Abstract: To determine the risks of microbial air pollution from microorganisms used for pesticides and bioremediation, or emanating from composting, fermentation tanks, or other agricultural and urban sources, airborne microbial levels must be evaluated. This study surveyed the atmospheric load of culturable bacteria at four locations in Oregon: a city street, a rye grass field, a Douglas fir forest, and a bluff on the Pacific coast. Samples (20–60 min each) were taken using slit and six-stage cascade samplers. Samples were taken over two 10- or 24-h periods, depending on the site. Meteorological measurements were made at each location. The quantity and type of bacteria found varied by location and time. The highest average number of bacteria during daylight hours was exhibited at the urban site (609 cfu/m3), followed by the forest site (522 cfu/m3), then the rural site (242 cfu/m3), with the lowest concentration found at the coastal site (103 cfu/m3). During the 24-h sampling periods at the rural site, bacterial concentration, in general, tended to increase at sunrise, decrease during the solar noon hours, gradually increase until sunset, then decrease into the evening, with the lowest concentrations occurring between 2100 and 0500 hours. Pigmented bacteria represented between 21 and 62% of the total bacteria sampled; the highest percentage of pigmented bacteria was found at the rural site, and the lowest percentage at the forest site. Bacillus was found to be the most abundant single genus represented at all locations (12–45%). The majority of bacteria found were associated with particles greater than 3 μm aerodynamic diameter. Information gathered from this survey combined with data from the literature and future surveys will contribute to the detection and description of microbial air pollution.

Key ecological responses to nitrogen are altered by climate change

Abstract: In this Review the cumulative effects of anthropogenic nitrogen and climate change are considered. Including how climate alters nitrogen cycling and availability, and the impact of nitrogen addition on carbon cycling, acidification and biodiversity.

Physical Disintegration of Biochar: An Overlooked Process

Abstract: Data collected from both artificially and field (naturally) weathered biochar suggest that a potentially significant pathway of biochar disappearance is through physical breakdown of the biochar structure. Via scanning electron microscopy, we characterized this physical weathering that increased the number of structural fractures and yielded higher numbers of liberated biochar fragments. This was hypothesized to be due to the graphitic sheet expansion accompanying water sorption coupled with comminution. These fragments can be on the microscale and the nanoscale but are still carbon-rich particles with no detectable alteration in the oxygen:carbon ratio from that of the original biochar. However, these particles are now easily dissolved and could be moved by infiltration. There is a need to understand how to produce biochars that are resistant to physical degradation to maximize long-term biochar C sequestration potential within soil systems.

Guidance to improve the scientific value of zeta-potential measurements in nanoEHS

Abstract: Nanoparticle zeta-potentials are relatively easy to measure, and have consistently been proposed in guidance documents as a particle property that must be included for complete nanoparticle characterization. There is also an increasing interest in integrating data collected on nanomaterial properties and behavior measured in different systems (e.g. in vitro assays, surface water, soil) to identify the properties controlling nanomaterial fate and effects, to be able to integrate and reuse datasets beyond their original intent, and ultimately to predict behaviors of new nanomaterials based on their measured properties (i.e. read across), including zeta-potential. Several confounding factors pose difficulty in taking, integrating and interpreting this measurement consistently. Zeta-potential is a modeled quantity determined from measurements of the electrophoretic mobility in a suspension, and its value depends on the nanomaterial properties, the solution conditions, and the theoretical model applied. The ability to use zeta-potential as an explanatory variable for measured behaviors in different systems (or potentially to predict specific behaviors) therefore requires robust reporting with relevant meta-data for the measurement conditions and the model used to convert mobility measurements to zeta-potentials. However, there is currently no such standardization for reporting in the nanoEHS literature. The objective of this tutorial review is to familiarize the nanoEHS research community with the zeta-potential concept and the factors that influence its calculated value and interpretation, including the effects of adsorbed macromolecules. We also provide practical guidance on the precision of measurement, interpretation of zeta-potential as an explanatory variable for processes of interest (e.g. toxicity, environmental fate), and provide advice for addressing common challenges associated with making meaningful zeta-potential measurements using commercial instruments. Finally, we provide specific guidance on the parameters that need to be reported with zeta-potential measurements to maximize interpretability and to support scientific synthesis across data sets.