Because the world's forests play a major role in regulating nutrient and carbon cycles, there is much interest in estimating their biomass. Estimates of aboveground biomass based on well-established ...methods are relatively abundant; estimates of root biomass based on standard methods are much less common. The goal of this work was to determine if a reliable method to estimate root biomass density for forests could be developed based on existing data from the literature. The forestry literature containing root biomass measurements was reviewed and summarized and relationships between both root biomass density (Mg ha-1) and root:shoot ratios (R/S) as dependent variables and various edaphic and climatic independent variables, singly and in combination, were statistically tested. None of the tested independent variables of aboveground biomass density, latitude, temperature, precipitation, temperature:precipitation ratios, tree type, soil texture, and age had important explanatory value for R/S. However, linear regression analysis showed that aboveground biomass density, age, and latitudinal category were the most important predictors of root biomass density, and together explained 84% of the variation. A comparison of root biomass density estimates based on our equations with those based on use of generalized R/S ratios for forests in the United States indicated that our method tended to produce estimates that were about 20% higher.
Frameworks for limiting ecosystem exposure to excess nutrients and acidity require accurate and complete deposition budgets of reactive nitrogen (Nr). While much progress has been made in developing ...total Nr deposition budgets for the U.S., current budgets remain limited by key data and knowledge gaps. Analysis of National Atmospheric Deposition Program Total Deposition (NADP/TDep) data illustrates several aspects of current Nr deposition that motivate additional research. Averaged across the continental U.S., dry deposition contributes slightly more (55%) to total deposition than wet deposition and is the dominant process (>90%) over broad areas of the Southwest and other arid regions of the West. Lack of dry deposition measurements imposes a reliance on models, resulting in a much higher degree of uncertainty relative to wet deposition which is routinely measured. As nitrogen oxide (NOx) emissions continue to decline, reduced forms of inorganic nitrogen (NHx = NH3 + NH4+) now contribute >50% of total Nr deposition over large areas of the U.S. Expanded monitoring and additional process-level research are needed to better understand NHx deposition, its contribution to total Nr deposition budgets, and the processes by which reduced N deposits to ecosystems. Urban and suburban areas are hotspots where routine monitoring of oxidized and reduced Nr deposition is needed. Finally, deposition budgets have incomplete information about the speciation of atmospheric nitrogen; monitoring networks do not capture important forms of Nr such as organic nitrogen. Building on these themes, we detail the state of the science of Nr deposition budgets in the U.S. and highlight research priorities to improve deposition budgets in terms of monitoring and flux measurements, leaf- to regional-scale modeling, source apportionment, and characterization of deposition trends and patterns.
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•Deposition budgets for inorganic nitrogen have improved over the last decade in the U.S.•Important data and knowledge gaps in monitoring and modeling of total nitrogen deposition remain.•Expanded monitoring of deposition in agricultural and urban areas is needed.•Monitoring of organic N deposition and improvement of organic N in atmospheric models is needed.•Land use specific modeled deposition estimates are needed for critical load assessments.
On 4 June 2011, the volcanic complex Puyehue-Cordon Caulle located in the Chilean Andes erupted, producing a plume of gases and particles that eventually circled the Southern Hemisphere, disrupting ...air travel and depositing ash in large quantities. On eight occasions, the plume passed over the city of Buenos Aires, Argentina, leading local authorities to close the two international airports. The eruption occurred during an on-going field campaign when measurements of the properties of atmospheric aerosol particles were being made in Buenos Aires as part of a year-long study of the concentration and optical properties of aerosol at one site in the city. The suite of instruments deployed in Buenos Aires were not tailored to measurements of volcanic ash, but were designed to characterize urban conditions. Nevertheless, these measurements were analysed for periods when vertical profiles of aerosol backscatter, made with a ceilometer, clearly showed the presence of the volcano plume over the research site and resulted in airport closure. Aerosol optical thickness derived from AERONET, MODIS and a ceilometer at our research site, all show enhanced values clearly indicating that the three platforms identified the volcanic plume simultaneously. However, a quantitative comparison of the different estimates proves difficult, suggesting large spatial and temporal variability of the plume. Our results indicate that the number concentration of condensation nuclei (CN), the mass concentration of particle-bound polycyclic aromatic hydrocarbons (PPAH) and the light absorption coefficient exceeded the average background values by more than one standard deviation during the events of volcanic plume. The anomalous concentrations of CN suggest new particle formation, presumably from the conversion of SO sub(2), while the anomalous concentrations of PPAH may come from the uptake of PAHs on the plume particles or from chemical reactions on the surface of plume particles. The anomalous absorption coefficients indicate that plume particles may contain certain compounds that can absorb radiation at 550 nm. Another possible explanation consistent with the observations is the scavenging of black carbon from urban sources as the plume descends through the boundary layer to the surface. In addition, the volcanic plume influenced the local meteorology resulting in a decrease of the temperature when compared to the average temperature during days with no plume present.
Despite a large body of evidence describing care processes known to reduce the incidence of surgical site infections, many are underutilized in practice.
Fifty-six hospitals volunteered to redesign ...their systems as part of the National Surgical Infection Prevention Collaborative, a 1-year demonstration project sponsored by the Centers for Medicare & Medicaid Services. Each facility selected quality improvement objectives for a select group of surgical procedures and reported monthly clinical process measure data.
Forty-four hospitals reported data on 35,543 surgical cases. Hospitals improved in measures related to appropriate antimicrobial agent selection, timing, and duration; normothermia; oxygenation; euglycemia; and appropriate hair removal. The infection rate decreased 27%, from 2.3% to 1.7% in the first versus last 3 months.
The Collaborative demonstrated improvement in processes known to be associated with reduced risk of surgical site infections. Quality improvement organizations can be effective resources for quality improvement in the surgical arena.
The eruption in June 2011 of the Puyehue-Cordón Caulle Volcanic Complex in Chile impacted air traffic around the Southern Hemisphere for several months after the initial ash emissions. The ash ...deposited in vast areas of the Patagonian Steppe was subjected to the strong wind conditions prevalent during the austral winter and spring experiencing resuspension over various regions of Argentina. In this study we analyze the meteorological conditions that led to the episode of volcanic ash resuspension which impacted the city of Buenos Aires and resulted in the closure of the two main airports in Buenos Aires area (Ezeiza and Aeroparque) on 16 October 2011. A relevant result is that resuspended material (volcanic ash plus dust) imprints a distinguishable feature within the atmospheric thermodynamic vertical profiles. The thermodynamic soundings show the signature of "pulses of drying" in layers associated with the presence of hygroscopic ash in the atmosphere that has already been reported in similar episodes after volcanic eruptions in other parts of the world. This particular footprint can be used to detect the probable existence of volcanic ash layers. This study also illustrates the utility of ceilometers to detect not only cloud base at airports but also volcanic ash plumes at the boundary layer and up to 7 km altitude. Aerosol properties measured in the city during the resuspension episode indicate the presence of enhanced concentrations of aerosol particles in the boundary layer along with spectral signatures in the measurements at the Buenos Aires AERONET site typical of ash plus dust advected towards the city. The mandatory aviation reports from the National Weather Service about airborne and deposited volcanic ash at the airport near the measurement site (Aeroparque) correlate in time with the enhanced concentrations. The presence of the resuspended material was detected by the CALIOP lidar overpassing the region. Since the dynamics of ash resuspension and recirculation are similar to the dynamics of dust storms, we use the HYSPLIT model with the dust storm module to simulate the episode that affected Buenos Aires. The results of the modeling agree qualitatively with satellite lidar measurements.
Density functional calculations for the binding energy of oleic acid-based ligands on Pb-rich {100} and {111} facets of PbSe nanocrystals determine the surface energies as a function of ligand ...coverage. Oleic acid is expected to bind to the nanocrystal surface in the form of lead oleate. The Wulff construction predicts the thermodynamic equilibrium shape of the PbSe nanocrystals. The equilibrium shape is a function of the ligand surface coverage, which can be controlled by changing the concentration of oleic acid during synthesis. The different binding energy of the ligand on the {100} and {111} facets results in different equilibrium ligand coverages on the facets, and a transition in the equilibrium shape from octahedral to cubic is predicted when increasing the ligand concentration during synthesis.
A single-particle soot photometer (SP2) was flown on a NASA WB-57F high-altitude research aircraft in November 2004 from Houston, Texas. The SP2 uses laser-induced incandescence to detect individual ...black carbon (BC) particles in an air sample in the mass range of approx.3-300 fg (approx.0.15-0.7 microns volume equivalent diameter). Scattered light is used to size the remaining non-BC aerosols in the range of approx.0.17-0.7 microns diameter. We present profiles of both aerosol types from the boundary layer to the lower stratosphere from two midlatitude flights. Results for total aerosol amounts in the size range detected by the SP2 are in good agreement with typical particle spectrometer measurements in the same region. All ambient incandescing particles were identified as BC because their incandescence properties matched those of laboratory-generated BC aerosol. Approximately 40% of these BC particles showed evidence of internal mixing (e.g., coating). Throughout profiles between 5 and 18.7 km, BC particles were less than a few percent of total aerosol number, and black carbon aerosol (BCA) mass mixing ratio showed a constant gradient with altitude above 5 km. SP2 data was compared to results from the ECHAM4/MADE and LmDzT-INCA global aerosol models. The comparison will help resolve the important systematic differences in model aerosol processes that determine BCA loadings. Further intercomparisons of models and measurements as presented here will improve the accuracy of the radiative forcing contribution from BCA.
Airborne observations of fluorescent aerosol were made aboard an airship during CloudLab, a series of flights that took place in September and October of 2013 and covered a wideband of longitude ...across the continental U.S. between Florida and California and between 28 and 37 N latitudes. Sampling occurred from near the surface to 1000 m above the ground. A Wideband Integrated Bioaerosol Sensor (WIBS‐4) measured average concentrations of supermicron fluorescent particles aloft (1 µm to 10 µm), revealing number concentrations ranging from 2.1 ± 0.8 to 8.7 ± 2.2 × 104 particles m−3 and representing up to 24% of total supermicron particle number. We observed distinct variations in size distributions and fluorescent characteristics in different regions, and attribute these to geographically diverse bioaerosol. Fluorescent aerosol detected in the east is largely consistent with mold spores observed in a laboratory setting, while a shift to larger sizes associated with different fluorescent patterns is observed in the west. Fluorescent bioaerosol loadings in the desert west were as high as those near the Gulf of Mexico, suggesting that bioaerosol is a substantial component of supermicron aerosol both in humid and arid environments. The observations are compared to model fungal and bacterial loading predictions, and good agreement in both particle size and concentrations is observed in the east. In the west, the model underestimated observed concentrations by a factor between 2 and 4 and the prescribed particle sizes are smaller than the observed fluorescent aerosol. A classification scheme for use with WIBS data is also presented.
Key Points
Fluorescent supermicron aerosol loads are reported across the southern U.S.
Regional variations in fluorescent behavior and particle size are observed
Comparison to modeled emissions shows an underestimate in the west
The Mexico City metropolitan area (MCMA) is a region that continues to grow in population and vehicular traffic as well as being the largest source of short-lived climate pollutants (SLCP) in Latin ...America. The local city government has made significant progress in controlling some of these pollutants, i.e., ozone (O3) and carbon monoxide (CO), but particulate matter (PM2.5 and PM10) and black carbon (BC) have shown a less positive response to mitigation strategies that have been in place for almost 3 decades. For the first time, extended measurements of equivalent black carbon (eBC), derived from light absorption measurements, have been made using a Photoacoustic Extinctiometer (PAX) over a 13 month period from March 2013 through March 2014. The daily trends in workdays (Monday through Saturday) and Sunday eBC, PM2.5 and the co-pollutants CO, O3 and NOx are evaluated with respect to the three primary seasons in the MCMA: rainy, cold and dry and warm and dry. The maximum values in all of the particle and gas concentrations were significantly larger (Student's t test, P < 0.05) during the dry periods than in the rainy season. The changes from rainy to dry seasons for eBC, PM2.5, CO, O3 and NOx were 8.8 to 13.1 mu g m-3 (40 %), 49 to 73 mu g m-3 (40 %), 2.5 to 3.8 ppm (40 %), 73 to 100 ppb (30 %) and 144 to 252 ppb (53 %), respectively. The primary factors that lead to these large changes between the wet and dry seasons are the accelerated vertical mixing of boundary layer and free tropospheric air by the formation of clouds that dilutes the concentration of the SLCPs, the decreased actinic flux that reduces the production of ozone by photochemical reactions and the heavy, almost daily rain that removes particulate matter. A significant "weekend effect" was also identified, particularly the decrease in BC due to fewer large transport vehicles that are fueled by diesel, which produces a large fraction of the BC. The other co-pollutant concentrations are also significantly less on weekends except for O3 that shows no change in maximum values from workdays to Sundays. This lack of change is a result of the balancing effects of lower precursor gases, i.e., VOCs, offset by lower concentrations of NOx, that is an O3 inhibitor. A comparison of the average maximum value of eBC measured during the 1 year period of the current study, with maximum values measured in shorter field campaigns in 2000 and 2006, shows no significant change in the eBC emissions over a 14 year period. This suggests that new methods may need to be developed that can decrease potentially toxic levels of this particulate pollutant.
Researchers display confirmation bias when they persevere by revising procedures until obtaining a theory-predicted result. This strategy produces findings that are overgeneralized in avoidable ways, ...and this in turn hinders successful applications. (The 40-year history of an attitude-change phenomenon, the sleeper effect, stands as a case in point.) Confirmation bias is an expectable product of theory-centered research strategies, including both the puzzle-solving activity of T. S. Kuhn's "normal science" and, more surprisingly, K. R. Popper's recommended method of falsification seeking. The alternative strategies of condition seeking (identifying limiting conditions for a known finding) and design (discovering conditions that can produce a previously unobtained result) are result centered; they are directed at producing specified patterns of data rather than at the logically impossible goals of establishing either the truth or falsity of a theory. Result-centered methods are by no means atheoretical. Rather, they oblige resourcefulness in using existing theory and can stimulate novel development of theory.
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