scholarly journals Intermediate-scale horizontal isoprene concentrations in the near-canopy forest atmosphere and implications for emission heterogeneity

2019 ◽  
Vol 116 (39) ◽  
pp. 19318-19323 ◽  
Author(s):  
Carla E. Batista ◽  
Jianhuai Ye ◽  
Igor O. Ribeiro ◽  
Patricia C. Guimarães ◽  
Adan S. S. Medeiros ◽  
...  
Keyword(s):  
Landscape Heterogeneity ◽  
Transport Model ◽  
Wet Season ◽  
Quality Models ◽  
Early Afternoon ◽  
Canopy Access ◽  
Central Amazonia ◽  
Volatile Organic ◽  
Aerial Vehicle ◽  
Horizontal Heterogeneity

The emissions, deposition, and chemistry of volatile organic compounds (VOCs) are thought to be influenced by underlying landscape heterogeneity at intermediate horizontal scales of several hundred meters across different forest subtypes within a tropical forest. Quantitative observations and scientific understanding at these scales, however, remain lacking, in large part due to a historical absence of canopy access and suitable observational approaches. Herein, horizontal heterogeneity in VOC concentrations in the near-canopy atmosphere was examined by sampling from an unmanned aerial vehicle (UAV) flown horizontally several hundred meters over the plateau and slope forests in central Amazonia during the morning and early afternoon periods of the wet season of 2018. Unlike terpene concentrations, the isoprene concentrations in the near-canopy atmosphere over the plateau forest were 60% greater than those over the slope forest. A gradient transport model constrained by the data suggests that isoprene emissions differed by 220 to 330% from these forest subtypes, which is in contrast to a 0% difference implemented in most present-day biosphere emissions models (i.e., homogeneous emissions). Quantifying VOC concentrations, emissions, and other processes at intermediate horizontal scales is essential for understanding the ecological and Earth system roles of VOCs and representing them in climate and air quality models.

scholarly journals A sampler for atmospheric volatile organic compounds by copter unmanned aerial vehicles

2018 ◽  
Author(s):  
Karena A. McKinney ◽  
Daniel Wang ◽  
Jianhuai Ye ◽  
Jean-Baptiste de Fouchier ◽  
Patricia C. Guimarães ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Unmanned Aerial Vehicles ◽  
Organic Compounds ◽  
Sample Volume ◽  
Battery Capacity ◽  
Central Amazonia ◽  
Volatile Organic ◽  
Aerial Vehicle ◽  
Offline Analysis ◽  
Design Challenges

Abstract. A sampler for volatile organic compounds (VOCs) was developed for deployment on a copter-technology unmanned aerial vehicle (UAV). The sampler was designed to collect VOCs on up to five commercially available VOC-adsorbent cartridges for subsequent offline analysis by thermal-desorption gas chromatography. The sampler had a mass of 0.90 kg and dimensions of 19 cm × 20 cm × 5 cm. Power consumption was <3 Wh in a typical 30 min flight, representing <3 % of the total UAV battery capacity. Autonomous sampler operation and data collection in flight were accomplished with a microcontroller. Sampling flows of 100 to 400 sccm were possible, and a typical flow of 150 sccm was used to balance VOC capture efficiency with sample volume. The overall minimum detection limit for the sampling volumes and the analytical method was close to 2 ppt for isoprene and monoterpenes. The sampler was mounted to a commercially available UAV and flown in August 2017 over tropical forest in central Amazonia. Samples were collected sequentially for 10 min each at several different altitude-latitude-longitude collection points. The species identified, their concentrations, and their uncertainties are presented and discussed in the context of the sampler design and capabilities. Finally, design challenges and possibilities for next-generation samplers are addressed.

scholarly journals A sampler for atmospheric volatile organic compounds by copter unmanned aerial vehicles

2019 ◽  
Vol 12 (6) ◽  
pp. 3123-3135 ◽  
Author(s):  
Karena A. McKinney ◽  
Daniel Wang ◽  
Jianhuai Ye ◽  
Jean-Baptiste de Fouchier ◽  
Patricia C. Guimarães ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Unmanned Aerial Vehicles ◽  
Organic Compounds ◽  
Sample Volume ◽  
Battery Capacity ◽  
Central Amazonia ◽  
Volatile Organic ◽  
Aerial Vehicle ◽  
Offline Analysis ◽  
Design Challenges

Abstract. A sampler for volatile organic compounds (VOCs) was developed for deployment on a multicopter unmanned aerial vehicle (UAV). The sampler was designed to collect gas- and aerosol-phase VOCs on up to four commercially available VOC-adsorbent cartridges for subsequent offline analysis by thermal-desorption gas chromatography. The sampler had a mass of 0.90 kg and dimensions of 19 cm ×20 cm ×5 cm. Power consumption was < 10 kJ in a typical 30 min flight, representing < 3 % of the total UAV battery capacity. Autonomous sampler operation and data collection in flight were accomplished with a microcontroller. Sampling flows of 100 to 400 sccm were possible, and a typical flow of 150 sccm was used to balance VOC capture efficiency with sample volume. The overall minimum detection limit of the analytical method for a 10 min sample was 3 ppt and the uncertainty was larger than 3 ppt or 20 % for isoprene and monoterpenes. The sampler was mounted to a commercially available UAV and flown in August 2017 over tropical forest in central Amazonia. Samples were collected sequentially for 10 min each at several different altitude–latitude–longitude collection points. The species identified, their concentrations, their uncertainties, and the possible effects of the UAV platform on the results are presented and discussed in the context of the sampler design and capabilities. Finally, design challenges and possibilities for next-generation samplers are addressed.

Atmospheric impact of sesquiterpenes in the Amazon rainforest

2020 ◽  
Author(s):  
Nora Zannoni ◽  
Stefan Wolff ◽  
Anywhere Tsokankunku ◽  
Matthias Soergel ◽  
Marta Sa ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Forest Canopy ◽  
Dry Season ◽  
Amazon Rainforest ◽  
Wet Season ◽  
Organic Species ◽  
Central Amazonia ◽  
Volatile Organic ◽  
Chromatographic Peaks ◽  
Ozone Reactivity

&lt;p&gt;Sesquiterpenes (C&lt;sub&gt;15&lt;/sub&gt;H&lt;sub&gt;24&lt;/sub&gt;) are highly reactive biogenic volatile organic compounds playing an important role in atmospheric chemistry. Once emitted from the Earth&amp;#8217;s surface, primarily by vegetation, they are rapidly oxidized to semivolatile oxygenated organic species that can lead to secondary organic aerosols (SOA) that influence climate. In the pristine Amazon rainforest environment oxidation of sesquiterpenes is initiated by OH and ozone.&lt;/p&gt;&lt;p&gt;We measured sesquiterpenes in March 2018 (wet season) and November 2018 (dry season) from central Amazonia, at the remote field site ATTO (Amazonian Tall Tower Observatory), Brazil. Samples were collected on adsorbent filled tubes equipped with ozone scrubbers at different heights above the forest canopy&amp;#160;;&amp;#160;every three hours for two weeks at 80m and 150m (wet season) and every hour for three days at 80m, 150m and 320m (dry season). Samples were then analysed in the&amp;#160;laboratory with a TD-GC-TOF-MS (Thermodesorption-Gas Chromatographer-Time Of Flight-Mass Spectrometer, Markes International). Simultaneous measurements of ozone and meteorological parameters were made at the nearby INSTANT tower. Identification of the chromatographic peaks was achieved by injection of standard molecules and by matching literature mass spectra. Quantification of the chemical compounds was achieved by injection of a standard mixture containing terpenes.The most abundant sesquiterpene measured at ATTO is (-)-&amp;#945;-copaene. Its diel profile varies with photosynthetically active radiation (PAR) and temperature, suggesting the canopy to be the main emission source. Interestingly, other identified sesquiterpenes show a consistent mirrored cycle, with their concentration being higher by night than by day. These varied mostly with RH suggesting the soil to be the main source of the emissions. Air samples taken at the ground are qualitatively and quantitatively different to those collected at different altitudes from the tower. Sesquiterpenes show a common maximum at sunrise (5&amp;#160;:00-7&amp;#160;:00 local time, UTC-4h) coincident with a strong decrease in ozone concentration (&gt;50% decrease on average during the dry season). The strongest effect is registered during the dry season, when sesquiterpenes and ozone concentrations are highest and ozone loss is largest. The atmospheric impact of the measured sesquiterpenes will be discussed including ozone reactivity contributions and OH generation.&lt;/p&gt;

scholarly journals Carbon monoxide (CO) and ethane (C<sub>2</sub>H<sub>6</sub>) trends from ground-based solar FTIR measurements at six European stations, comparison and sensitivity analysis with the EMEP model

2011 ◽  
Vol 11 (17) ◽  
pp. 9253-9269 ◽  
Author(s):  
J. Angelbratt ◽  
J. Mellqvist ◽  
D. Simpson ◽  
J. E. Jonson ◽  
T. Blumenstock ◽  
...  
Keyword(s):  
Transport Model ◽  
Global Scale ◽  
Global Model ◽  
Scale Model ◽  
Chemical Transport Model ◽  
Suitable Alternative ◽  
European Model ◽  
Time Period ◽  
Volatile Organic ◽  
Made In

Abstract. Trends in the CO andC2H6 partial columns ~0–15 km) have been estimated from four European ground-based solar FTIR (Fourier Transform InfraRed) stations for the 1996–2006 time period. The CO trends from the four stations Jungfraujoch, Zugspitze, Harestua and Kiruna have been estimated to −0.45 ± 0.16% yr−1, −1.00 ± 0.24% yr−1, −0.62 ± 0.19 % yr−1 and −0.61 ± 0.16% yr−1, respectively. The corresponding trends for C2H6 are −1.51 ± 0.23% yr−1, −2.11 ± 0.30% yr−1, −1.09 ± 0.25% yr−1 and −1.14 ± 0.18% yr−1. All trends are presented with their 2-σ confidence intervals. To find possible reasons for the CO trends, the global-scale EMEP MSC-W chemical transport model has been used in a series of sensitivity scenarios. It is shown that the trends are consistent with the combination of a 20% decrease in the anthropogenic CO emissions seen in Europe and North America during the 1996–2006 period and a 20% increase in the anthropogenic CO emissions in East Asia, during the same time period. The possible impacts of CH4 and biogenic volatile organic compounds (BVOCs) are also considered. The European and global-scale EMEP models have been evaluated against the measured CO and C2H6 partial columns from Jungfraujoch, Zugspitze, Bremen, Harestua, Kiruna and Ny-Ålesund. The European model reproduces, on average the measurements at the different sites fairly well and within 10–22% deviation for CO and 14–31% deviation for C2H6. Their seasonal amplitude is captured within 6–35% and 9–124% for CO and C2H6, respectively. However, 61–98% of the CO and C2H6 partial columns in the European model are shown to arise from the boundary conditions, making the global-scale model a more suitable alternative when modeling these two species. In the evaluation of the global model the average partial columns for 2006 are shown to be within 1–9% and 37–50% of the measurements for CO and C2H6, respectively. The global model sensitivity for assumptions made in this paper is also analyzed.

scholarly journals Observing atmospheric formaldehyde (HCHO) from space: validation and intercomparison of six retrievals from four satellites (OMI, GOME2A, GOME2B, OMPS) with SEAC<sup>4</sup>RS aircraft observations over the Southeast US

2016 ◽  
Author(s):  
Lei Zhu ◽  
Daniel J. Jacob ◽  
Patrick S. Kim ◽  
Jenny A. Fisher ◽  
Karen Yu ◽  
...  
Keyword(s):  
Transport Model ◽  
Research Groups ◽  
Chemical Transport Model ◽  
Shape Factors ◽  
Aircraft Observations ◽  
Volatile Organic ◽  
Satellite Retrievals ◽  
Mass Factor ◽  
The Mean ◽  
Southeast Us

Abstract. Formaldehyde (HCHO) column data from satellites are widely used as a proxy for emissions of volatile organic compounds (VOCs), but validation of the data has been extremely limited. Here we use highly accurate HCHO aircraft observations from the NASA SEAC4RS campaign over the Southeast US in August–September 2013 to validate and intercompare six operational and research retrievals of HCHO columns from four different satellite instruments (OMI, GOME2A, GOME2B and OMPS) and three different research groups. The GEOS-Chem chemical transport model provides a common intercomparison platform. We find that all retrievals capture the HCHO maximum over Arkansas and Louisiana, reflecting high emissions of biogenic isoprene, and are consistent in their spatial variability over the Southeast US (r = 0.4–0.8 on a 0.5° × 0.5° grid) as well as their day-to-day variability (r = 0.5–0.8). However, all satellite retrievals are biased low in the mean by 20–51 %, which would lead to corresponding bias in estimates of isoprene emissions from the satellite data. The smallest bias is for OMI-BIRA, which has the highest corrected slant columns and the lowest scattering weights in its air mass factor (AMF) calculation. Correcting the assumed HCHO vertical profiles (shape factors) used in the AMF calculation would further reduce the bias in the OMI-BIRA data. We conclude that current satellite HCHO data provide a reliable proxy for isoprene emission variability but with a low mean bias due both to the corrected slant columns and the scattering weights used in the retrievals.

Contributions to the epidemiology of human sleeping sickness in Liberia: bionomics of the vector Glossina palpalis (R.-D.) in a forest habitat

1964 ◽  
Vol 54 (4) ◽  
pp. 727-744 ◽  
Author(s):  
R. Foster
Keyword(s):  
Forest Canopy ◽  
Activity Patterns ◽  
Effective Means ◽  
Climatic Conditions ◽  
Primary Forest ◽  
Wet Season ◽  
North West ◽  
Early Afternoon ◽  
Prolonged Contact ◽  
Glossina Palpalis

Glossina, palpalis (R.-D.) was studied in three localities near Voinjama, in a forest region in north-west Liberia, where human trypanosomiasis persists only as sporadic cases. Sites were chosen with different degrees of contact between man, fly and game, in transitional vegetation on the Zeliba River, and in primary forest on the Lofa and Lawa Rivers. The general features, fauna and climate of these areas are described. Catching by nets was found to be preferable to the use of traps. Trap catches averaged about one-quarter of the corresponding net catches. The theoretical basis of ‘animal’ traps is too uncertain for their use in quantitative studies, and under forest conditions there are practical difficulties in siting them in optimum positions; they failed to catch at all at very low fly densities. Heavy rain and the dry season were unfavourable to the fly, particularly outside the forest canopy. A wet-season resting site on horizontal twigs near to the ground is described. The percentage of females in the total catch differed significantly between different habitats, but apparently was not indicative of the degree of hunger in the population. There were no great differences between the sexes in activity patterns, and activity was greatest during the apparently unfavourable climatic conditions of early afternoon. The willingness of the fly to penetrate unfavourable surroundings suggests that the clearing of forest at potential places of transmission is unlikely to afford an effective means of protection. There is some evidence that breeding was curtailed during the rains. Very few engorged flies were found. Fly numbers and distribution were not affected by normal game movements. There is no evidence that the fly was ever dependent on man for food. Where game was driven away the fly tended to follow it. Occasional human foci did not affect the number or distribution of the fly, and fly activity was not correlated with human activity. Intimate and prolonged contact between man and fly did not occur.

scholarly journals Contributions of biomass-burning, urban, and biogenic emissions to the concentrations and light-absorbing properties of particulate matter in central Amazonia during the dry season

2019 ◽  
Vol 19 (12) ◽  
pp. 7973-8001 ◽  
Author(s):  
Suzane S. de Sá ◽  
Luciana V. Rizzo ◽  
Brett B. Palm ◽  
Pedro Campuzano-Jost ◽  
Douglas A. Day ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Biomass Burning ◽  
Mass Concentration ◽  
Anthropogenic Impacts ◽  
Dry Season ◽  
Primary Study ◽  
Wet Season ◽  
Factor Loadings ◽  
Central Amazonia ◽  
Mass Concentrations

Abstract. Urbanization and deforestation have important impacts on atmospheric particulate matter (PM) over Amazonia. This study presents observations and analysis of PM1 concentration, composition, and optical properties in central Amazonia during the dry season, focusing on the anthropogenic impacts. The primary study site was located 70 km downwind of Manaus, a city of over 2 million people in Brazil, as part of the GoAmazon2014/5 experiment. A high-resolution time-of-flight aerosol mass spectrometer (AMS) provided data on PM1 composition, and aethalometer measurements were used to derive the absorption coefficient babs,BrC of brown carbon (BrC) at 370 nm. Non-refractory PM1 mass concentrations averaged 12.2 µg m−3 at the primary study site, dominated by organics (83 %), followed by sulfate (11 %). A decrease in babs,BrC was observed as the mass concentration of nitrogen-containing organic compounds decreased and the organic PM1 O:C ratio increased, suggesting atmospheric bleaching of the BrC components. The organic PM1 was separated into six different classes by positive-matrix factorization (PMF), and the mass absorption efficiency Eabs associated with each factor was estimated through multivariate linear regression of babs,BrC on the factor loadings. The largest Eabs values were associated with urban (2.04±0.14 m2 g−1) and biomass-burning (0.82±0.04 to 1.50±0.07 m2 g−1) sources. Together, these sources contributed at least 80 % of babs,BrC while accounting for 30 % to 40 % of the organic PM1 mass concentration. In addition, a comparison of organic PM1 composition between wet and dry seasons revealed that only part of the 9-fold increase in mass concentration between the seasons can be attributed to biomass burning. Biomass-burning factor loadings increased by 30-fold, elevating its relative contribution to organic PM1 from about 10 % in the wet season to 30 % in the dry season. However, most of the PM1 mass (>60 %) in both seasons was accounted for by biogenic secondary organic sources, which in turn showed an 8-fold seasonal increase in factor loadings. A combination of decreased wet deposition and increased emissions and oxidant concentrations, as well as a positive feedback on larger mass concentrations are thought to play a role in the observed increases. Furthermore, fuzzy c-means clustering identified three clusters, namely “baseline”, “event”, and “urban” to represent different pollution influences during the dry season. The baseline cluster, representing the dry season background, was associated with a mean mass concentration of 9±3 µg m−3. This concentration increased on average by 3 µg m−3 for both the urban and the event clusters. The event cluster, representing an increased influence of biomass burning and long-range transport of African volcanic emissions, was characterized by remarkably high sulfate concentrations. The urban cluster, representing the influence of Manaus emissions on top of the baseline, was characterized by an organic PM1 composition that differed from the other two clusters. The differences discussed suggest a shift in oxidation pathways as well as an accelerated oxidation cycle due to urban emissions, in agreement with findings for the wet season.

scholarly journals Formaldehyde over the eastern Mediterranean during MINOS: Comparison of airborne in-situ measurements with 3D-model results

2003 ◽  
Vol 3 (3) ◽  
pp. 851-861 ◽  
Author(s):  
R. Kormann ◽  
H. Fischer ◽  
M. de Reus ◽  
M. Lawrence ◽  
Ch. Brühl ◽  
...  
Keyword(s):  
Boundary Layer ◽  
3D Model ◽  
Transport Model ◽  
Eastern Mediterranean ◽  
Lower Atmosphere ◽  
Photochemical Degradation ◽  
Chemical Transport Model ◽  
Acetone Concentration ◽  
Volatile Organic ◽  
The Mediterranean

Abstract. Formaldehyde (HCHO) is an important intermediate product in the photochemical degradation of methane and non-methane volatile organic compounds. In August 2001, airborne formaldehyde measurements based on the Hantzsch reaction technique were performed during the Mediterranean INtensive Oxidant Study, MINOS. The detection limit of the instrument was 42 pptv (1s) at a time resolution of 180 s (10-90%). The overall uncertainty of the HCHO measurements was 30% at a mixing ratio of 300 pptv. In the marine boundary layer over the eastern Mediterranean Sea average HCHO concentrations were of the order of 1500 pptv, in reasonable agreement with results from a three-dimensional global chemical transport model of the lower atmosphere including non-methane volatile organic compound (NMVOC) chemistry. Above the boundary layer HCHO mixing ratios decreased with increasing altitude to a minimum level of 250 pptv at about 7 km. At higher altitudes (above 7 km) HCHO levels showed a strong dependency on the airmass origin. In airmasses from the North Atlantic/North American area HCHO levels were of the order of 300 pptv, a factor of 6 higher than values predicted by the model. Even higher HCHO levels, increasing to values of the order of 600 pptv at 11 km altitude, were observed in easterlies transporting air affected by the Indian monsoon outflow towards the Mediterranean basin. Only a small part (~30 pptv) of the large discrepancy between the model results and the measurements of HCHO in the free troposphere could be explained by a strong underestimation of the upper tropospheric acetone concentration by up to a factor of ten by the 3D-model. Therefore, the measurement-model difference in the upper troposphere remains unresolved, while the observed dependency of HCHO on airmass origin might indicate that unknown, relatively long-lived NMVOCs - or their reaction intermediates - associated with biomass burning are at least partially responsible for the observed discrepancies.

scholarly journals Diurnal, seasonal and long-term variations of global formaldehyde columns inferred from combined OMI and GOME-2 observations

2015 ◽  
Vol 15 (21) ◽  
pp. 12519-12545 ◽  
Author(s):  
I. De Smedt ◽  
T. Stavrakou ◽  
F. Hendrick ◽  
T. Danckaert ◽  
T. Vlemmix ◽  
...  
Keyword(s):  
Transport Model ◽  
A Priori ◽  
Eastern China ◽  
Horizontal Resolution ◽  
Vertical Profiles ◽  
Beijing Area ◽  
Spatially Correlated ◽  
Early Afternoon ◽  
Significant Downward Trend ◽  
Highly Correlated

Abstract. We present the new version (v14) of the BIRA-IASB algorithm for the retrieval of formaldehyde (H2CO) columns from spaceborne UV–visible sensors. Applied to OMI measurements from Aura and to GOME-2 measurements from MetOp-A and MetOp-B, this algorithm is used to produce global distributions of H2CO representative of mid-morning and early afternoon conditions. Its main features include (1) a new iterative DOAS scheme involving three fitting intervals to better account for the O2–O2 absorption, (2) the use of earthshine radiances averaged in the equatorial Pacific as reference spectra, and (3) a destriping correction and background normalisation resolved in the across-swath position. For the air mass factor calculation, a priori vertical profiles calculated by the IMAGES chemistry transport model at 09:30 and 13:30 LT are used. Although the resulting GOME-2 and OMI H2CO vertical columns are found to be highly correlated, some systematic differences are observed. Afternoon columns are generally larger than morning ones, especially in mid-latitude regions. In contrast, over tropical rainforests, morning H2CO columns significantly exceed those observed in the afternoon. These differences are discussed in terms of the H2CO column variation between mid-morning and early afternoon, using ground-based MAX-DOAS measurements available from seven stations in Europe, China and Africa. Validation results confirm the capacity of the combined satellite measurements to resolve diurnal variations in H2CO columns. Furthermore, vertical profiles derived from MAX-DOAS measurements in the Beijing area and in Bujumbura are used for a more detailed validation exercise. In both regions, we find an agreement better than 15 % when MAX-DOAS profiles are used as a priori for the satellite retrievals. Finally, regional trends in H2CO columns are estimated for the 2004–2014 period using SCIAMACHY and GOME-2 data for morning conditions, and OMI for early afternoon conditions. Consistent features are observed, such as an increase of the columns in India and central–eastern China, and a decrease in the eastern US and Europe. We find that the higher horizontal resolution of OMI combined with a better sampling and a more favourable illumination at midday allow for more significant trend estimates, especially over Europe and North America. Importantly, in some parts of the Amazonian forest, we observe with both time series a significant downward trend in H2CO columns, spatially correlated with areas affected by deforestation.

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