A14C-01
Introduction and Overview of the AMazonian Aerosol characteriZation Experiment (AMAZE-08)
The main objectives of AMAZE-08 were to understand the sources and regulators of organic particle mass in
a pristine continental environment and the connections between particle chemistry and particle optical and
hygroscopic properties. The AMAZE-08 tower measurements were conducted between February 7 and
March 14, 2008 during the wet reason. The site was 60 km NNW of Manaus and located within a mostly
pristine rainforest. The winds were predominantly from the ENE across 1600 km of mostly undeveloped
forest. The site was mostly free of anthropogenic influences and allowed the study of pristine biological
aerosol particles, although there were several episodes of long-range transport from Europe and Africa and
more infrequent regional transport from Manaus and northerly biomass burning. Particle instrumentation
included two high-resolution aerosol mass spectrometers (HR-ToF-AMS) with thermodenuder, two cloud
condensation nuclei counters (CCNC), a continuous flow diffusion chamber (CFDC) for ice nuclei
measurements, three optical particle counters (OPC), an ultraviolet aerodynamic particle sizer (UV-APS) for
measurement of biologically active particles, two tapered element oscillating microbalances (TEOM), two
scanning mobility particle sizers (SMPS), two multiwavelength nephelometers, three condensation particle
counters (CPC), a multi-angle absorption photometer (MAAP), an athelometer, coarse- and fine-mode filters
for elemental and ion analysis as well as particle imaging, an AERONET sun photometer including
photosynthetically active radiation (PAR), and LIDAR system. Gas instrumentation included a proton-transfer
mass spectrometer (PTR-MS), gas adsorption cartridge for off-line chromatographic analysis, and
measurement of O3, CO, CO2, NO, and NOx. This talk will present an overview of AMAZE-08 and will
highlight selected results.
http://www.seas.harvard.edu/AMAZE-08
A14C-02 INVITED
The Nature of the Atmospheric Aerosol over the Amazon Basin: Microchemical Observations and Cloud Nucleation Ability
We investigated the microchemical and cloud-nucleating properties of the atmospheric aerosol over the central Amazon Basin near Manaus during the wet season in February and March 2008. The measurements were conducted as part of the AMAZE-08 (Amazonian Aerosol Characterization Experiment) campaign. A newly developed electron microscopic technique revealed the presence of liquid organic material in aerosol particles, which we interpret as secondary organic aerosol (SOA). In the fine fraction of the Amazonian aerosol, these SOA particles are the most abundant particle type. They occur often, but not always in internal mixture with very small seasalt particles. SOA particles with carbonaceous or mineral dust cores are less frequent. In the coarse fraction, mineral dust particles from transatlantic origin were common, and were occasionally also coated with SOA. Primary biogenic aerosols in the supermicron size range could be identified by their morphological characteristics. They were quite abundant, and were also frequently coated with SOA. The CCN activity of the aerosol was consistent with these microscopic observations. The smallest particles had low hygroscopicities (kappa values of ca. 0.1) consistent with nearly pure SOA. With increasing size, and increasing abundance of inorganic components in the particles, their hygroscopicity and CCN activity increased towards values similar to those typically found in continental aerosols.
A14C-03
Biogenic Aerosols Over the Amazon Basin: Optical Properties and Relationship With Elemental and Ionic Composition
We investigated the optical properties of natural biogenic aerosol particles over the central Amazon Basin
near Manaus during the wet season in February and March 2008. The measurements were conducted as
part of the AMAZE-08 (Amazonian Aerosol Characterization Experiment) sampling campaign. Light absorption
was determined with the use of an Aethalometer and an MAAP (Multi Angle Absorption Photometer). Light
scattering was measured with a 3 wavelength TSI nephelometer and an Ecotech nephelometer. The
elemental composition was measured trough PIXE and IC. Single scattering albedo shows relatively low
values varying from 0.86 to 0.95. Very low fine mode aerosol mass was measured, and coarse mode
particles are responsible for a significant fraction of scattering and absorption. Sulfur was observed in very
low concentrations, and most of the aerosol mass was organic. Long range transport of soil dust from Sahara
were observed and reflected in the light scattering coefficient. Wavelength dependence of absorption
indicates the strong influence of coarse mode aerosol. Aerosol optical thickness shows low values, but with
significant single scattering albedo values, showing strong absorption properties of these biogenic aerosols.
Size distribution measurements shows consistence with the scattering coefficients measured, if the coarse
mode particles are taken into account.
http://www.seas.harvard.edu/AMAZE-08
A14C-04 INVITED
Biogenic VOC emissions from African, American, and Asian tropical forests
Tropical landscapes have the most dynamic and yet most poorly understood biogeochemistry on earth. Biogenic Volatile Organic Compound (BVOC) emission models (e.g., Guenther et al. 1995) estimate that the tropics, which contain about 40% of the global land mass and account for about 60% of the global annual net primary productivity (NPP), contribute about 80% of the total global flux of isoprene and are a major source of other important biogenic VOC. These biogenic emissions are driven by the high productivity and strong solar radiation inputs in the tropics which also drive the dynamical processes which allow tropical BVOC emissions to impact the global atmosphere. Understanding tropical BVOC emissions is necessary for characterizing global atmospheric chemistry but is particularly challenging due to the extreme biological diversity and the difficult logistical requirements associated with most tropical regions. Biogenic VOC emission models from the past decade (e.g. Guenther et al. (1995), which are still widely used today, have tropical forest emission estimates that are based on a single study in the Amazon. More recent BVOC emission models (e.g. Guenther et al. 2006) incorporate a larger number of measurements but recognize that these data are still insufficient to accurately quantify seasonal and spatial variations in the tropics. Recent studies in the Amazon (AMAZE-08, TROFFEE), West Africa (AMMA), and Asian (OP3) tropics are providing new insights into BVOC emissions from tropical landscapes. Biogenic VOC emissions from African, American and Asian tropics are compared and contrasted in this presentation and their potential role in atmospheric chemistry in each region is discussed. Potential BVOC emission changes associated with land-use and climate change are considered and the major research needs are outlined.
A14C-05
A Coupled Programme of Aerosol Research Within the OP3 and ACES Projects
The oxidation of organic compounds in the troposphere plays a central role in the generation of ozone, and leads to the formation of secondary organic aerosol (SOA) and other secondary pollutants. Approximately 90% of organic material emitted globally is estimated to originate from biogenic sources, with almost half of all reactive biogenic volatile organic compounds (BVOC) being emitted from tropical and sub-tropical forests. It is becoming increasingly clear from observational studies that biogenic SOA (BSOA) is the dominant source of aerosol organic carbon concentrations in remote environments. This provides part of the motivation for the OP3 project. Ground-based aerosol measurements at the Global Atmosphere Watch (GAW) site in Danum Valley Conservation Area in OP3 were provided by a suite of instrumentation for full composition and physical property characterisation (size distribution, hygroscopicity and CCN activation). To further enhance our understanding of aerosol processes in the Borneo rainforest, additional capability was assembled within the UK NERC funded "Aerosol Coupling in the Earth System" (ACES) programme. Field component enhancements to the OP3 aerosol payload by ACES included a deployment of aerosol and precursor flux measurements within the forest canopy to characterise primary bioaerosol sources and in-canopy chemistry leading to formation of secondary aerosol components. In addition, measurements of VOCs and aerosol composition were made above an oil palm plantation to assess the impact of land-use change on aerosol processes. ACES is a coupled programme of field, chamber, mechanism development and modelling investigations aiming to reduce uncertainties in our fundamental understanding of BSOA formation and the subsequent impact on atmospheric composition. In addition to summarising aerosol field measurements within ACES / OP3, we will present an overview of the status of the ACES chamber and modelling results with the overall aim to: i) improve quantitative descriptions of fundamental emission processes from plant surfaces, particularly for native and commercial tropical species, ii) provide quantitative descriptions of key biogenic flux processes between organic aerosols and their precursor gases, iii) develop evaluated mechanisms for degradation of biogenic VOCs to produce SOA precursors iv) assess the impact of such processes on regional aerosol burden and v) assess the impact of land-use changes on aerosol emission / formation and deposition and develop predictive capability.
A14C-06
The Regional Extent of Biogenic Aerosols in Borneo
The processes that control the composition of aerosols are currently not well understood, as are their effects on regional climate and meteorology. This is particularly true when considering tropical regions; the enhanced plant activity and extensive forestation are responsible for large amounts of VOCs being released into the atmosphere, which are responsible for forming secondary aerosol matter. However, the aerosols in these regions are currently poorly characterised both in terms of their concentration, physiochemical properties and the spatial extent of their influence. During the summer of 2008, an extensive suite of instrumentation was deployed on a number of platforms as part of the Oxidant and Particle Photochemical Processes (OP3) and the Aerosol Coupling in the Earth System (ACES) projects. The principle surface site was the Bukit Atur Global Atmosphere Watch (GAW) site in the Danum Valley Conservation Area. This featured a variety of aerosol instrumentation, designed to characterise the aerosol properties in conjunction with gas phase and meteorological measurements. In addition, many more instruments were also deployed aboard the Facility for Airborne Atmospheric Measurement (FAAM) BAe-S 146 research aircraft. Some of these instruments (including the Aerodyne Aerosol Mass Spectrometer and Droplet Measurement Technologies Cloud Condensation Nuclei counter) were designed to duplicate the ground based measurements, so that the spatial extent of the aerosols could be assessed in addition to the detailed characterisation work. Typical flights included atmospheric profiles and flights within the boundary layer (BL) over the forest to map out the extent of the aerosols and precursors. The non refractory BL aerosols typically contained a mixture of organic matter and sulphate, the latter possibly of oceanic origin. This is in contrast to the free troposphere where consistently low concentrations were recorded. Of particular interest was studying the differences in atmospheric composition when comparing the BL over primary and mature secondary forest with that over palm oil plantations. Changes were noted during the transitions between the two land use types, relating to the different VOC emission profiles of the two vegetation types and the enhanced human activity.
A14C-07
Fluxes and In-Canopy Gradients of Biogenic Volatile Organic Compounds Above Contrasting South East Asian Land Uses
Fluxes of volatile organic compounds were measured above tropical rainforest and oil palm plantation in the Malaysian state of Sabah on the island of Borneo. During April and July 2008 an Ionikon proton transfer reaction mass spectrometer (ptrms) was operated at the 100 m Global Atmospheric Watch (GAW) tower at Bukit Atur, at the edge of the Danum Valley conservation area. An ultrasonic anemometer and air inlet were mounted at 76 m, with the ptrms housed in a laboratory building at the foot of the tower, measuring fluxes over tropical rainforest (selectively logged in 1989) with a typical canopy height of 30 to 40 m. In addition, during the July period, a second ptrms was coupled to a lift system which automatically moved an inlet to sample in-canopy gradients inside the forest canopy, between 2 and 30 m. During May 2008, the ptrms was moved to an oil palm plantation, north of the town of Lahad Datu, were fluxes were measured at a height of 15 m above the 12 m tall canopy, together with concentrations and fluxes of ozone and aerosols. These measurements formed part of two major UK projects: OP3-Danum-2008 (Oxidant and Particle Production Processes above South East Asian Rainforest) was aimed at quantifying biogenic emissions and evaluating their impact on air chemistry and the production of photo-oxidants and biogenic secondary organic aerosol, while ACES (Aerosol Coupling in the Earth System) studies the role of primary biogenic emissions, in-canopy processes and the effect of land-use change on aerosols. Initial results indicate that fluxes of isoprene above forest averaged 1.4 mg m-2 s-1 which is somewhat smaller than previous measurements in Amazonia and than previous estimates derived from leaf- level measurements, reflecting uncertainties in the assumed plant species composition. Concentrations peaked at the top of the canopy during midday. With an average of 5.5 mg m-2s-1, isoprene fluxes above the oil palm plantation were four times larger. Average fluxes of total monoterpenes were 0.15 mg m-2 s-1 at the forest site and 0.85 mg m-2 s-1 above oil palm. Fluxes of isoprene oxidation products (MVK + MACR) were upwards above forest and downward above oil palm, indicating that the high measurement height on the GAW tower provided more time for chemical conversion. Particle number fluxes above forest showed periods of apparent emission during midday indicative of VOC emissions resulting in particle growth.