21 research outputs found
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Patterns of CO2 and radiocarbon across high northern latitudes during International Polar Year 2008
High-resolution in situ CO2 measurements were conducted aboard the NASA DC-8 aircraft during the ARCTAS/POLARCAT field campaign, a component of the wider 2007-2008 International Polar Year activities. Data were recorded during large-scale surveys spanning the North American sub-Arctic to the North Pole from 0.04 to 12 km altitude in spring and summer of 2008. Influences on the observed CO2 concentrations were investigated using coincident CO, black carbon, CH3CN, HCN, O3, C2Cl4, and Δ14CO2 data, and the FLEXPART model. In spring, the CO2 spatial distribution from 55̊N to 90̊N was largely determined by the long-range transport of air masses laden with Asian anthropogenic pollution intermingled with Eurasian fire emissions evidenced by the greater variability in the mid-to-upper troposphere. At the receptor site, the enhancement ratios of CO2 to CO in pollution plumes ranged from 27 to 80 ppmv ppmv-1 with the highest anthropogenic content registered in plumes sampled poleward of 80̊N. In summer, the CO2 signal largely reflected emissions from lightning-ignited wildfires within the boreal forests of northern Saskatchewan juxtaposed with uptake by the terrestrial biosphere. Measurements within fresh fire plumes yielded CO2 to CO emission ratios of 4 to 16 ppmv ppmv-1 and a mean CO2 emission factor of 1698 ± 280 g kg-1 dry matter. From the 14C in CO2 content of 48 whole air samples, mean spring (46.6 ± 4.4%) and summer (51.5 ± 5%) D14CO2 values indicate a 5%seasonal difference. Although the northern midlatitudes were identified as the emissions source regions for the majority of the spring samples, depleted Δ14CO2 values were observed in <1% of the data set. Rather, ARCTAS Δ14CO2 observations (54%) revealed predominately a pattern of positive disequilibrium (1-7%) with respect to background regardless of season owing to both heterotrophic respiration and fire-induced combustion of biomass. Anomalously enriched Δ14CO2 values (101-262%) measured in emissions from Lake Athabasca and Eurasian fires speak to biomass burning as an increasingly important contributor to the mass excess in Δ14CO2 observations in a warming Arctic, representing an additional source of uncertainty in the quantification of fossil fuel CO2
Deserdados sociais: condições de vida e saúde dos presos do estado do Rio de Janeiro. Rio de Janeiro
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Chemical composition of tropospheric air masses encountered during high altitude flights (11.5 km) during the 2009 fall Operation Ice Bridge field campaign
[1] As part of the 2009 Operation Ice Bridge campaign, the NASA DC-8 aircraft was used to fill the data-time gap in laser observation of the changes in ice sheets, glaciers and sea ice between ICESat-I (Ice, Cloud, and land Elevation Satellite) and ICESat-II. Complementing the cryospheric instrument payload were four in situ atmospheric sampling instruments integrated onboard to measure trace gas concentrations of CO2, CO, N2O, CH 4, water vapor and various VOCs (Volatile Organic Compounds). This paper examines two plumes encountered at high altitude (12 km) during the campaign; one during a southbound transit flight (13°S) and the other at 86°S over Antarctica. The data presented are especially significant as the Southern Hemisphere is heavily under-sampled during the austral spring, with few if any high-resolution airborne observations of atmospheric gases made over Antarctica. Strong enhancements of CO, CH4, N2O, CHCl 3, OCS, C2H6, C2H2 and C3H8 were observed in the two intercepted air masses that exhibited variations in VOC composition suggesting different sources. The transport model FLEXPART showed that the 13°S plume contained predominately biomass burning emissions originating from Southeast Asia and South Africa, while both anthropogenic and biomass burning emissions were observed at 86° S with South America and South Africa as indicated source regions. The data presented here show evidence that boundary layer pollution is transported from lower latitudes toward the upper troposphere above the South Pole, which may not have been observed in the past. © 2012. American Geophysical Union. All Rights Reserved
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Patterns of CO2 and radiocarbon across high northern latitudes during International Polar Year 2008
High-resolution in situ CO2 measurements were conducted aboard the NASA DC-8 aircraft during the ARCTAS/POLARCAT field campaign, a component of the wider 2007-2008 International Polar Year activities. Data were recorded during large-scale surveys spanning the North American sub-Arctic to the North Pole from 0.04 to 12 km altitude in spring and summer of 2008. Influences on the observed CO2 concentrations were investigated using coincident CO, black carbon, CH3CN, HCN, O3, C2Cl4, and Δ14CO2 data, and the FLEXPART model. In spring, the CO2 spatial distribution from 55̊N to 90̊N was largely determined by the long-range transport of air masses laden with Asian anthropogenic pollution intermingled with Eurasian fire emissions evidenced by the greater variability in the mid-to-upper troposphere. At the receptor site, the enhancement ratios of CO2 to CO in pollution plumes ranged from 27 to 80 ppmv ppmv-1 with the highest anthropogenic content registered in plumes sampled poleward of 80̊N. In summer, the CO2 signal largely reflected emissions from lightning-ignited wildfires within the boreal forests of northern Saskatchewan juxtaposed with uptake by the terrestrial biosphere. Measurements within fresh fire plumes yielded CO2 to CO emission ratios of 4 to 16 ppmv ppmv-1 and a mean CO2 emission factor of 1698 ± 280 g kg-1 dry matter. From the 14C in CO2 content of 48 whole air samples, mean spring (46.6 ± 4.4%) and summer (51.5 ± 5%) D14CO2 values indicate a 5%seasonal difference. Although the northern midlatitudes were identified as the emissions source regions for the majority of the spring samples, depleted Δ14CO2 values were observed in <1% of the data set. Rather, ARCTAS Δ14CO2 observations (54%) revealed predominately a pattern of positive disequilibrium (1-7%) with respect to background regardless of season owing to both heterotrophic respiration and fire-induced combustion of biomass. Anomalously enriched Δ14CO2 values (101-262%) measured in emissions from Lake Athabasca and Eurasian fires speak to biomass burning as an increasingly important contributor to the mass excess in Δ14CO2 observations in a warming Arctic, representing an additional source of uncertainty in the quantification of fossil fuel CO2
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Characteristics of the atmospheric CO2 signal as observed over the conterminous United States during INTEX-NA
High resolution in situ measurements of atmospheric CO2 were made from the NASA DC-8 aircraft during the Intercontinental Chemical Transport Experiment - North America (INTEX-NA) campaign, part of the wider International Consortium for Atmospheric Research on Transport and Transformation (ICARTT). During the summer of 2004, eighteen flights comprising 160h of measurements were conducted within a region bounded by 27 to 53°N and 36 to 139°W over an altitude range of 0.15 to 12 km. These large-scale surveys provided the opportunity to examine the characteristics of the atmospheric CO2 signal over sparsely sampled areas of North America and adjacent ocean basins. The observations showed a high degree of variability (≤ 18%) due to the myriad source and sink processes influencing the air masses intercepted over the INTEX-NA sampling domain. Surface fluxes had strong effects on continental scale concentration gradients. Clear signatures of CO2 uptake were seen east of the Mississippi River, notably a persistent CO2 deficit in the lowest 2-3 km. When combining the airborne CO2 measurements with LANDSAT and MODIS data products, the lowest CO2 mixing ratios observed during the campaign (337 ppm) were tied to mid-continental agricultural fields planted in corn and soybeans. We used simultaneous measurements of CO, O3, C2Cl4, C2H6, C2H2 and other unique chemical tracers to differentiate air mass types. Coupling these distinct air mass chemical signatures with transport history permitted identification of convection, stratosphere-troposphere exchange, long-range transport from Eastern Asia, boreal wildfires, and continental outflow as competing processes at multiple scales influencing the observed concentrations. Our results suggest these are important factors contributing to the large-scale distribution in CO2 Mixing ratios thus these observations offer new constraints in the computation of the North American carbon budget. Copyright 2008 by the American Geophysical Union
Physiological alterations in pepper during wilt induced by Phytophthora capsici and soil water deficit
Rational method in the repetitive calcium oscillation measurement in wild type human epithelial kidney cells
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Nitrogen oxides and PAN in plumes from boreal fires during ARCTAS-B and their impact on ozone: An integrated analysis of aircraft and satellite observations
We determine enhancement ratios for NOx, PAN, and other NO y species from boreal biomass burning using aircraft data obtained during the ARCTAS-B campaign and examine the impact of these emissions on tropospheric ozone in the Arctic. We find an initial emission factor for NO x of 1.06 g NO per kg dry matter (DM) burned, much lower than previous observations of boreal plumes, and also one third the value recommended for extratropical fires. Our analysis provides the first observational confirmation of rapid PAN formation in a boreal smoke plume, with 40% of the initial NOx emissions being converted to PAN in the first few hours after emission. We find little clear evidence for ozone formation in the boreal smoke plumes during ARCTAS-B in either aircraft or satellite observations, or in model simulations. Only a third of the smoke plumes observed by the NASA DC8 showed a correlation between ozone and CO, and ozone was depleted in the plumes as often as it was enhanced. Special observations from the Tropospheric Emission Spectrometer (TES) also show little evidence for enhanced ozone in boreal smoke plumes between 15 June and 15 July 2008. Of the 22 plumes observed by TES, only 4 showed ozone increasing within the smoke plumes, and even in those cases it was unclear that the increase was caused by fire emissions. Using the GEOS-Chem atmospheric chemistry model, we show that boreal fires during ARCTAS-B had little impact on the median ozone profile measured over Canada, and had little impact on ozone within the smoke plumes observed by TES. © 2010 Author(s)