Urban environments are the primary contributors to global anthropogenic carbon emissions. Because much of the growth in CO 2 emissions will originate from cities, there is a need to develop, assess, and improve measurement and modeling strategies for quantifying and monitoring greenhouse gas emissions from large urban centers. In this study the uncertainties in an aircraft-based mass balance approach for quantifying carbon dioxide and methane emissions from an urban environment, focusing on Indianapolis, IN, USA, are described. The relatively level terrain of Indianapolis facilitated the application of mean wind fields in the mass balance approach. We investigate the uncertainties in our aircraft-based mass balance approach by (1) assessing the sensitivity of the measured flux to important measurement and analysis parameters including wind speed, background CO 2 and CH 4 , boundary layer depth, and interpolation technique, and (2) determining the flux at two or more downwind distances from a point or area source (with relatively large source strengths such as solid waste facilities and a power generating station) in rapid succession, assuming that the emission flux is constant. When we quantify the precision in the approach by comparing the estimated emis-sions derived from measurements at two or more downwind distances from an area or point source, we find that the minimum and maximum repeatability were 12 and 52 %, with an average of 31 %. We suggest that improvements in the experimental design can be achieved by careful determination of the background concentration, monitoring the evolution of the boundary layer through the measurement period, and increasing the number of downwind horizontal transect measurements at multiple altitudes within the boundary layer.

We report the CH 4 emission flux from the city of Indianapolis, IN, the site of the Indianapolis Flux Experiment (INFLUX) project for developing, assessing, and improving top-down and bottom-up approaches for quantifying urban greenhouse gas emissions. Using an aircraft-based mass balance approach, we find that the average CH 4 emission rate from five flight experiments in 2011 is 135 ± 58 (1σ) moles s-1 (7800 ± 3300 kg hr-1). The effective per capita CH 4 emission rate for Indianapolis is 77 kg CH 4 person-1 yr-1 , a figure that is less than the national anthropogenic CH 4 emission (∼91 kg CH 4 person-1 yr-1) but considerably larger than the global figure (∼48 kg CH 4 person-1 yr-1). We consistently observed elevated CH 4 concentrations at specific coordinates along our flight transects downwind of the city. Inflight investigations as well as back trajectories using measured wind directions showed that the elevated concentrations originated from the southwest side of the city where a landfill and a natural gas transmission regulating station (TRS) are located. Street level mobile measurements downwind of the landfill and the TRS supported the results of aircraft-based data, and were used to quantify the relative contributions from the two sources. We find that the CH 4 emission from the TRS was negligible relative to the landfill, which was responsible for 33 ± 10% of the citywide emission flux. A regression of propane versus methane from aircraft flask samples suggests that the remaining citywide CH 4 emissions (∼67%) derive from the natural gas distribution system. We discuss the combination of surface mobile observations and aircraft city-wide flux measurements to determine the total flux and apportionment to important sources.

Urban environments are the primary contributors to global anthropogenic carbon emissions. Because much of the growth in CO 2 emissions will originate from cities, there is a need to develop, assess, and improve measurement and modeling strategies for quantifying and monitoring greenhouse gas emissions from large urban centers. In this study the uncertainties in an aircraft-based mass balance approach for quantifying carbon dioxide and methane emissions from an urban environment, focusing on Indianapolis, IN, USA, are described. The relatively level terrain of Indianapolis facilitated the application of mean wind fields in the mass balance approach. We investigate the uncertainties in our aircraft-based mass balance approach by (1) assessing the sensitivity of the measured flux to important measurement and analysis parameters including wind speed, background CO 2 and CH 4 , boundary layer depth, and interpolation technique, and (2) determining the flux at two or more downwind distances from a point or area source (with relatively large source strengths such as solid waste facilities and a power generating station) in rapid succession, assuming that the emission flux is constant. When we quantify the precision in the approach by comparing the estimated emis-sions derived from measurements at two or more downwind distances from an area or point source, we find that the minimum and maximum repeatability were 12 and 52 %, with an average of 31 %. We suggest that improvements in the experimental design can be achieved by careful determination of the background concentration, monitoring the evolution of the boundary layer through the measurement period, and increasing the number of downwind horizontal transect measurements at multiple altitudes within the boundary layer.

for assistance and advice concerning the impingement sampler. Thanks are also extended to General Public Utilities Corporation and Jersey Central Power and Light Company for support of this work.

Root regeneration of tulip tree (Liriodendron tulipifera L.) was greater when seedlings were transplanted in the spring than in the fall. Indolebutyric acid–potassium salt (IBA) applied to the roots increased root regeneration with the greatest response at 1000 to 3000 mg liter−1 in the spring and 3000 mg liter−1 in the fall. Root regeneration and shoot growth increased as time of chilling at 2°C prior to transplanting increased from 0 to 1680 hours; 1008 hours satisfied the chilling requirement. Photoperiod did not directly influence root regeneration during either season. Root regeneration and shoot growth of shoot-pruned plants interacted with season, IBA treatment, and level of stem pruning. Decreasing sunlight intensity by 20%, 47%, or 74% reduced root regeneration and shoot growth. IBA improved root initiation over untreated plants at all light intensities tested, but subsequent growth of these roots decreased with decreased light.

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Royal Horticulture Society Colour Chart cards were used to compare the Linotype-Hell Saphir color flatbed scanner, the Minolta CR-200 chromameter and the HunterLab Labscan XE colorimeter in the Commission Internationale de l'Eclairage L*a*b* three-dimensional color space. Regression analysis revealed that these instruments measure color in a similar manner with most R2 values greater than 0.97 and slopes near unity for comparison of each of the three color space parameters (L*, a*, b*). Standard errors were also found to be within a narrow range for each parameter, L* (2.19 to 3.97), a* (5.97 to 12.01), b* (4.10 to 6.71). The Linotype-Hell Saphir color flatbed scanner and the Minolta CR-200 chromameter were also compared for samples with surface curvature using redtwig dogwood (Cornus serecia 'Baileyi') and yellowtwig dogwood (Cornus serecia `Flaviramea') stems but no significant difference was found.