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At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Microwave-Assisted Syngas Cleanup: Catalytic Reforming of Gasifier Tar Using a Low-Cost Iron Catalyst

The microwave-assisted gasification of plastic wastes to produce hydrogen-rich syngas is an attractive energy-saving plastic upcycling route, and the addition of biomass could improve the quality of the syngas produced; however, it could also increase the tar yield, which is an undesired, secondary product in this process. The presence of tars could result in downstream lines blockage, reactor down time and costly maintenance. Therefore, reducing or removing tar is desired. Due to its chemical complexity, toluene, which is one of the main tar constituents, could be used as a model tar compound. In this work, the microwave-assisted catalytic dry reforming of toluene was studied using Fe/Al2O3 as a catalyst, under CO2 at different reaction temperatures. The toluene reforming reaction was conducted using microwave and conventional thermal reactors. The results showed that under microwave irradiation, higher CO2 and toluene conversions, as well as better hydrogen yield can be observed compared to conventional toluene reforming at the same reaction temperature. The catalyst stability test was also investigated. Three reaction pathways were observed during microwave reaction.

Bai, Xinwei↗
NASA NTRS1998

A recirculating hydroponic system for studying peanut (Arachis hypogaea L.)

Peanut (Arachis hypogaea L.) plants were grown hydroponically, using continuously recirculating nutrient solution. Two culture tray designs were tested; one tray design used only nutrient solution, while the other used a sphagnum-filled pod development compartment just beneath the cover and above the nutrient solution. Both trays were fitted with slotted covers to allow developing gynophores to reach the root zone. Peanut seed yields averaged 350 gm-2 dry mass, regardless of tray design, suggesting that substrate is not required for hydroponic peanut production.

NASA Center KSC↗
NASA NTRS2022

Plasma Activated Water for Crewed Transit and Planetary Habitation: A Study of Gas Type, Electrode Material, and Power Supply Selection and the Impact on the Final Frontier - FY21 CIF

An in-depth study of plasma activated water (PAW) generation was conducted to link changes in power supply, electrode material, input gas, and treatment time to the resulting reaction chemistry. These changes in chemistry can help tailor PAW for different space applications. An AC, DC, and nanosecond (ns) pulsed power supply were each used to generate PAW with stainless steel, copper, tungsten, or platinum (Pt) electrodes while utilizing air, nitrogen (N2), carbon dioxide (CO2), helium (He), or argon (Ar) as the feed gas. Tap or deionized (DI) water was treated for 1 to 15 minutes, and the generated PAW was tested for changes in pH, conductivity, oxidation reduction potential, nitrates (NO3-), ammonium (NH4+), and peroxide. Calculations showed that the production of reactive nitrogen species was the leading cause of pH and conductivity changes. The DC generated air plasma was able to reduce the pH of DI water and generate NO3‑. The pulsed supply, operating at 20% of the input power of the DC supply, lowered the pH generated NO3‑. When a simulated Martian gas mixture of 95% CO2 and 5% N2 was used as the feed gas, NO3‑ was generated with the DC and pulsed supplies, respectively. Mixing PAW with plasma generated ash from inedible biomass allowed pH control, thus enhancing PAW’s potential use for sanitation applications. The large shift in pH was used to study sanitation effects of Escherichia coli (E. coli) reduction and Staphylococcus aureus (S. aureus), in which log reductions were found to be negligible. Additionally, the plasma generated ash in combination with PAW was also implemented in 10-day microgreen growth trials, in which PAW and ash resulted in quicker emergence of the microgreens compared to the standard growth conditions and comparable dry masses to Hoagland’s nutrient solution treated samples.

plasma activated water (PAW)↗
DOE OSTI2021

A Novel Platform for Algal Biomass Production Using Cellulosic Mixotrophy (CeMix) (Final Technical Report)

This novel project, branded CeMIX for cellulosic mixotrophy, targets solutions for several technological barriers limiting the deployment of algae cultivation in sunny, arid regions (specifically the southwest United States). Opening up the region for algae cultivation could increase DOE’s resource assessments and biofuel potential for the U.S. Mixotrophic metabolism in support of liquid fuel production is completely dependent on the availability of waste organic carbon in order to avoid diversion of food resources for fuel production. The use of cellulosic sugar hydrolysate (CSH) produced via the NREL process provided a standardized carbon source for study of the underlying biochemistry and metabolic adjustments to mixotrophy. Mixotrophic metabolism uses both photosynthetic CO 2 fixation and sugar oxidation to improve biomass productivity and harvest yield. The project was high-risk, high-reward in the sense that adding organic carbon to algal cultivation is an invitation for rapid-growth, heterotrophic contaminants to overtake the culture and consume mineral nutrients needed for algal growth. To help evade this outcome the project focused on acidophilic red algae that require low pH conditions with 40-48°C optimal temperature profiles that define them as low-range thermophiles. This is the only project in the BETO portfolio to utilize extreme conditions of low pH and high operating temperatures to control pathogens and competitors in mass culture. The project yielded five major outcomes. 1) Harvest densities of 5-10 g ash-free dry weight are easily achieved, providing a 10-fold reduction in water required and dewatering demand. 2) Catabolic repression of photosynthesis in G. sulphuraria is conditionally repressed by low oxygen. 3) Mixotrophic growth on cellulosic hydrolysate consumes all C6 and C5 sugars concomitant with increases in floridean starch with little change in lipid content. Protein content can be manipulated between 35 and 54 wt% by varying the C:N molar ratio from 10:1 to 20:1, respectively. 4) Mixotrophic cultures with up to 50 mM total sugar are remarkably stable at pH 2.5 and daily average reactor temperatures of 40°C. 5) Capital costs for glass tubular photobioreactors are prohibitive for liquid fuel production using a hydrothermal liquefaction processing pathway. The economic outlook for covered raceway ponds is better with a project minimum fuel selling price at $3.32 dm 3 GE -1 .

09 BIOMASS FUELS↗
NASA NTRS2003

Method for the control of NOx emissions in long-range space travel

The wheat straw, an inedible biomass that can be continuously produced in a space vehicle has been used to produce activated carbon for effective control of NOx emissions from the incineration of wastes. The optimal carbonization temperature of wheat straw was found to be around 600 degrees C when a burnoff of 67% was observed. The BET surface area of the activated carbon produced from the wheat straw reached as high as 300 m2/g. The presence of oxygen in flue gas is essential for effective adsorption of NO by activated carbon. On the contrary, water vapor inhibits the adsorption efficiency of NO. Consequently, water vapor in flue gas should be removed by drying agents before adsorption to ensure high NO adsorption efficiency. All of the NO in the flue gas was removed for more than 2 h by the activated carbons when 10% oxygen was present and the ratio of carbon weight to the flue gas flow rate (W/F) was 30 g min/L, with a contact time of 10.2 s. All of NO was reduced to N2 by the activated carbon at 450 degrees C with a W/F ratio of 15 g min/L and a contact time of 5.1 s. Reduction of the adsorbed NO also regenerated the activated carbon, and the regenerated activated carbon exhibited an improved NO adsorption efficiency. However, the reduction of the adsorbed NO resulted in a loss of carbon which was determined to be about 0.99% of the activated carbon per cycle of regeneration. The sufficiency of the amount of wheat straw in providing the activated carbon based on a six-person crew, such as the mission planned for Mars, has been determined. This novel approach for the control of NOx emissions is sustainable in a closed system such as the case in space travel. It is simple to operate and is functional under microgravity environment.

NASA Discipline Life Support Systems↗
NASA NTRS2016

Impacts of Snow Darkening by Absorbing Aerosols on Eurasian Climate

The deposition of absorbing aerosols on snow surfaces reduces snow-albedo and allows snowpack to absorb more sunlight. This so-called snow darkening effect (SDE) accelerates snow melting and leads to surface warming in spring. To examine the impact of SDE on weather and climate during late spring and early summer, two sets of NASA GEOS-5 model simulations with and without SDE are conducted. Results show that SDE-induced surface heating is particularly pronounced in Eurasian regions where significant depositions of dust transported from the North African deserts, and black carbon from biomass burning from Asia and Europe occur. In these regions, the surface heating due to SDE increases surface skin temperature by 3-6 degrees Kelvin near the snowline in spring. Surface energy budget analysis indicates that SDE-induced excess heating is associated with a large increase in surface evaporation, subsequently leading to a significant reduction in soil moisture, and increased risks of drought and heat waves in late spring to early summer. Overall, we find that rainfall deficit combined with SDE-induced dry soil in spring provide favorable condition for summertime heat waves over large regions of Eurasia. Increased frequency of summer heat waves with SDE and the region of maximum increase in heat-wave frequency are found along the snow line, providing evidence that early snowmelt by SDE may increase the risks of extreme summer heat wave. Our results suggest that climate models that do not include SDE may significantly underestimate the effect of global warming over extra-tropical continental regions.

GEOS-5↗
DOE OSTI2022

Co-Hydrotreating of Catalytic Fast Pyrolysis Oils with Straight-Run Diesel

Catalytic Fast Pyrolysis (CFP) of biomass provides an opportunity for producing stabilized bio-oils (CFP oils) that can be further processed into hydrocarbon transportation fuels via hydroprocessing. Standalone hydrotreating of CFP oils has been pursued and has been shown to be able to produce hydrocarbon products with low oxygen contents of <1wt%, but the process is costly due to the high requirements of hydrogen and high capital costs. The costs can be reduced by co-processing in refineries, which takes advantage of the existing refinery infrastructure and the economies of the larger scale of petroleum processing operations. In this contribution, we evaluated co-hydrotreating of CFP oil with straight-run diesel in a laboratory continuous hydrotreating reactor. The CFP oil had been produced over a bi-functional metal-acid catalyst (Pt/TiO2) and contained 17 wt% oxygen on dry basis, and it was fed to the reactor together with straight-run diesel in the proportion of 20 vol%:80 vol%. The co-hydrotreated diesel products had acceptable cetane numbers (>40), and the calculated carbon efficiencies were high (~95%) for the CFP portion of the feed mixtures. Biogenic carbon incorporation in the product was confirmed by C-14 analysis. Sulfided NiMo catalyst gave better performance with respect to the diesel product quality than CoMo did due to the higher hydrogenation activity of NiMo. A comparison of standalone hydrotreating of the CFP oil and the straight-run diesel to co-hydrotreating showed good correspondence. Major challenges and risks associated with co-hydrotreating are discussed in this presentation.

biomass↗
DOE OSTI2020

Investigating drivers of microbial activity and respiration in a forested bog

Northern peatlands store nearly one-third of terrestrial carbon (C) stocks while covering only 3% of the global landmass; nevertheless, the drivers of C cycling in these often-waterlogged ecosystems are different from those that control C dynamics in upland forested soils. To explore how multiple abiotic and biotic characteristics of bogs interact to shape microbial activity in a northern, forested bog, we added a labile C tracer ( 13 C-labeled starch) to in situ peat mesocosms and correlated heterotrophic respiration with natural variation in several microbial predictor variables, such as enzyme activity and microbial biomass, as well as with a suite of abiotic variables and proximity to vascular plants aboveground. We found that peat moisture content was positively correlated with respiration and microbial activity, even when moisture levels exceeded total saturation, suggesting that access to organic matter substrates in drier environments may be limiting for microbial activity. Proximity to black spruce trees decreased total and labile heterotrophic respiration. This negative relationship may reflect the influence of tree evapotranspiration and peat shading effects; i.e., microbial activity may decline as peat dries and cools near trees. Here, we isolated the response of heterotrophic respiration to explore the variation in, and interactions among, multiple abiotic and biotic drivers that influence microbial activity. This approach allowed us to reveal the relative influence of individual drivers on C respiration in these globally important C sinks.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Biogas Reforming to Syngas: A Review

Interest in novel uses of biogas has increased recently due to concerns about climate change and greater emphasis on renewable energy sources. Although biogas is frequently used in low-value applications such as heating and fuel in engines or even just flared, reforming is an emerging strategy for converting biogas to syngas, which could then be used to obtain high-value-added liquid fuels and chemicals. Interest also exists due to the role of dry, bi-, and tri-reforming in the capture and utilization of CO 2 . New research efforts have explored efficient and effective reforming catalysts, as specifically applied to biogas. In this paper, we review recent developments in dry, bi-, and tri-reforming, where the CO 2 in biogas is used as an oxidant/partial oxidant. The synthesis, characterization, lifetime, deactivation, and regeneration of candidate reforming catalysts are discussed in detail. The thermodynamic limitation and techno-economics of biogas conversion are also discussed.

09 BIOMASS FUELS↗
NASA NTRS1983

Nitrogen oxides in the troposphere - Global and regional budgets

The cycle of nitrogen oxides in the troposphere is discussed from both global and regional perspectives. Global sources for NO(x) are estimated to be of magnitude 50 (+ or - 25) x 10 to the 12th gm N/yr. Nitrogen oxides are derived from combustion of fossil fuels (40 percent) and biomass burning (25 percent) with the balance from lightning and microbial activity in soils. Estimates for the rate of removal of NOx based on recent atmospheric and precipitation chemistry data are consistent with global source strengths derived here. Industrial and agricultural activities provide approximately two thirds of the global source for NOx. In North America, sources from combustion of fossil fuels exceed natural sources by a factor of 3-13. Wet deposition removes about one third of the combustion source of NOx over North America, while dry deposition removes a similar amount. The balance is exported from the continent. Deposition of nitrate in precipitation over eastern Canada and the western Atlantic is clearly influenced by sources of NOx in the eastern United States.

Logan, J. A.↗
NASA NTRS1996

Nutrient management effects on sweetpotato genotypes under controlled environment

Sweetpotato is one of several crops recommended by National Aeronautics and Space Administration (NASA) for bioregenerative life support studies. One of the objectives of the Tuskegee University NASA Center is to optimize growth conditions for adaptability of sweetpotatoes for closed bioregenerative systems. The role of nutrient solution management as it impacts yield has been one of the major thrusts in these studies. Nutrient solution management protocol currently used consists of a modified half Hoagland solution that is changed at 14-day intervals. Reservoirs are refilled with deionized water if the volume of the nutrient solution was reduced to 8 liters or less before the time of solution change. There is the need to recycle and replenish nutrient solution during crop growth, rather than discard at 14 day intervals as previously done, in order to reduce waste. Experiments were conducted in an environmental growth room to examine the effects of container size on the growth of several sweetpotato genotypes grown under a nutrient replenishment protocol. Plants were grown from vine cuttings of 15cm length and were planted in 0.15 x 0.15 x 1.2m growth channels using a closed nutrient film technique system. Nutrient was supplied in a modified half strength Hoagland's solution with a 1:2.4 N:K ratio. Nutrient replenishment protocol consisted of daily water replenishment to a constant volume of 30.4 liters in the small containers and 273.6 liters in the large container. Nutrients were replenished as needed when the EC of the nutrient solution fell below 1200 mhos/cm. The experimental design used was a split-plot with the main plot being container size and genotypes as the subplot. Nine sweetpotato genotypes were evaluated. Results showed no effect of nutrient solution container size on storage root yield, foliage fresh and dry mass, leaf area or vine length. However, plants grown using the large nutrient solution container accumulated more storage root dry mass than those with the small containers. Although plants grown with the smaller containers showed greater water uptake, plant nutrient uptake was lower than with the larger container. All genotypes evaluated showed variation in their responses to all parameters measured.

Solanaceae/genetics/growth & development↗
DOE OSTI2023

Processes and systems for reforming of methane and light hydrocarbons to liquid hydrocarbon fuels

Processes for converting methane and/or other hydrocarbons to synthesis gas (i.e., a gaseous mixture comprising H 2 and CO) are disclosed, in which at least a portion of the hydrocarbon(s) is reacted with CO 2 . At least a second portion of the methane may be reacted with H 2 O (steam), thereby improving overall thermodynamics of the process, in terms of reducing endothermicity (ΔH) and the required energy input, compared to “pure” dry reforming in which no H 2 O is present. Such dry reforming (reaction with CO 2 only) or CO 2 -steam reforming (reaction with both CO 2 and steam) processes are advantageously integrated with Fischer-Tropsch synthesis to yield liquid hydrocarbon fuels. Further integration may involve the use of a downstream finishing stage involving hydroisomerization to remove FT wax. Yet other integration options involve the use of combined CO 2 -steam reforming and FT synthesis stages (optionally with finishing) for producing liquid fuels from gas streams generated in a number of possible processes, including the hydropyrolysis of biomass.

Marker, Terry↗
DOE OSTI2020

Assessing impacts of selective logging on water, energy, and carbon budgets and ecosystem dynamics in Amazon forests using the Functionally Assembled Terrestrial Ecosystem Simulator

Abstract. Tropical forest degradation from logging, fire, and fragmentation not only alters carbon stocks and carbon fluxes, but also impacts physical land surface properties such as albedo and roughness length. Such impacts are poorly quantified to date due to difficulties in accessing and maintaining observational infrastructures, as well as the lack of proper modeling tools for capturing the interactions among biophysical properties, ecosystem demography, canopy structure, and biogeochemical cycling in tropical forests. As a first step to address these limitations, we implemented a selective logging module into the Functionally Assembled Terrestrial Ecosystem Simulator (FATES) by mimicking the ecological, biophysical, and biogeochemical processes following a logging event. The model can specify the timing and aerial extent of logging events, splitting the logged forest patch into disturbed and intact patches; determine the survivorship of cohorts in the disturbed patch; and modifying the biomass and necromass (total mass of coarse woody debris and litter) pools following logging. We parameterized the logging module to reproduce a selective logging experiment at the Tapajós National Forest in Brazil and benchmarked model outputs against available field measurements. Our results suggest that the model permits the coexistence of early and late successional functional types and realistically characterizes the seasonality of water and carbon fluxes and stocks, the forest structure and composition, and the ecosystem succession following disturbance. However, the current version of FATES overestimates water stress in the dry season and therefore fails to capture seasonal variation in latent and sensible heat fluxes. Moreover, we observed a bias towards low stem density and leaf area when compared to observations, suggesting that improvements are needed in both carbon allocation and establishment of trees. The effects of logging were assessed by different logging scenarios to represent reduced impact and conventional logging practices, both with high and low logging intensities. The model simulations suggest that in comparison to old-growth forests the logged forests rapidly recover water and energy fluxes in 1 to 3 years. In contrast, the recovery times for carbon stocks, forest structure, and composition are more than 30 years depending on logging practices and intensity. This study lays the foundation to simulate land use change and forest degradation in FATES, which will be an effective tool to directly represent forest management practices and regeneration in the context of Earth system models.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Impact of Tree Age and Anatomical Fraction on Forest Residue Pyrolysis and Hydrotreating

Utilization of cost-advantaged biomass and waste resources to produce clean, domestic biofuels will be a key factor in decarbonizing transportation in the United States. This study investigates how the distribution of anatomical fractions (stem wood, bark, needles, branches) from pine forest residues of different ages impacts pyrolysis and hydrotreating processes, including product composition, carbon efficiency, economics, and overall sustainability. Commercially sourced 13- and 23-year-old loblolly pine residues were chosen to represent available resources; whole tree thinnings, and tops and branches from merchantable timber, respectively. Detailed characterization of the residue samples, product distributions, bio-oil, char, and gas characterization data are presented for 13 experiments, including the individual fractions, blends, and air-classified samples to reduce ash content. Pyrolysis mass balances averaged 97 +/- 3%. As expected, bio-oil yields were lower for the bark, needles, and blends with high proportions of these (53-56% dry basis), and highest for the debarked stem wood (67-71% dry basis). Lower yields were attributed to the high ash content of the needles, but also to the high lignin content in the bark (>50%), which is hypothesized to have led to increased char formation during pyrolysis. Higher-oil yield was generally correlated with total volatiles, hydrogen, oxygen, glucan, and mannan; somewhat correlated with xylan and acetyl content; and negatively correlated with total carbon, fixed carbon, nitrogen, sulfur, and extractives. Air classification of the residues was effective in reducing ash content (1.5% to 0.64%), extractives (~7% to 2%), and sulfur (0.04% to 0.02%), resulting in a small increase in yield, a significant increase in the GC-detectable proportion of oil (27% to 34%) and a net economic benefit. These experimental results were used to conduct technoeconomic and life cycle analyses, which are also summarized here.

biofuels↗
NASA NTRS1989

Potato growth in response to relative humidity

Potato plants (Solanum tuberosum L. cvs. Russet Burbank, Norland, and Denali) were grown for 56 days in controlled-environment rooms under continuous light at 20C and 50% or 85% RH. No significant differences in total plant dry weight were measured between the humidity treatments, but plants grown under 85% RH produced higher tuber yields. Leaf areas were greater under 50% RH and leaves tended to be larger and darker green than at 85% RH.

Non-NASA Center↗
DOE OSTI2021

Realism of Lagrangian Large Eddy Simulations Driven by Reanalysis Meteorology: Tracking a Pocket of Open Cells Under a Biomass Burning Aerosol Layer

An approach to drive Lagrangian large eddy simulation (LES) of boundary layer clouds with reanalysis data is presented and evaluated using satellite (Spinning Enhanced Visible and Infrared Imager, SEVIRI) and aircraft (Cloud-Aerosol-Radiation Interactions and Forcing, CLARIFY) measurements. The simulations follow trajectories of the boundary layer flow. They track the formation and evolution of a pocket of open cells (POC) underneath a biomass burning aerosol layer in the free troposphere. The simulations reproduce the evolution of observed stratocumulus cloud morphology, cloud optical depth, and cloud drop effective radius, and capture the timing of the cloud state transition from closed to open cells seen in the satellite imagery on the three considered trajectories. They reproduce a biomass burning aerosol layer identified by the in-situ aircraft measurements above the inversion of the POC. Entrainment of aerosol from the biomass burning layer into the POC is limited to the extent of having no impact on cloud- or boundary layer properties, in agreement with the CLARIFY observations. The two-moment bin microphysics scheme used in the simulations reproduces the in-situ cloud microphysical properties reasonably well. A two-moment bulk microphysics scheme reproduces the satellite observations in the non-precipitating closed-cell state, but overestimates liquid water path and cloud optical depth in the precipitating open-cell state due to insufficient surface precipitation. A boundary layer cold and dry bias occurring in LES can be counteracted by reducing the grid aspect ratio and by tightening the large scale wind speed nudging towards the surface.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2001

Airborne Sun photometry and Closure Studies in SAFARI-2000 Dry Season Campaign

From August 13 to September 25, the Southern African Regional Science Initiative's (SAFARI 2000) dry-season airborne campaign studied the complex interactions between the region's ecosystems, air pollution, atmospheric circulation, land-atmosphere interactions, and land use change. The field campaign was timed to coincide with the annual winter fire season in Southern Africa. This challenging campaign. which coordinated ground-based measurement teams, multiple research aircraft, and satellite overpasses across nine African nations, was head quartered at the Petersburg International Airport in South Africa's Northern Province. Among many others, unique coordinated observations were made of the evolution of massive, thick haze layers produced by industrial emissions, biomass burning, marine and biogenic sources. The NASA Ames Airborne Tracking 14-channel Sunphotometer (AATS-14) was operated successfully aboard the University of Washington CV-580 during 24 data flights. The AATS-14 instrument measures the transmission of the direct solar beam at 14 discrete wavelengths (3501558 nm) from which we derive spectral aerosol optical depths (AOD), columnar water vapor (CWV) and columnar ozone. Flying at different altitudes over a fixed location allows derivation of layer AOD and CWV. Data taken during feasible vertical profiles allows derivation of aerosol extinction and water vapor density. In the talk, we show comparisons with ground-based AERONET sun/sky photometer results, with ground based MPL-Net lidar data, and with measurements from a lidar aboard the high flying ER-2 aircraft. We will use measurements from the Ames Solar Spectral Flux Radiometer to derive estimates of solar spectral forcing as a function of aerosol thickness. Validations of TOMS and Terra satellite aerosol and water-vapor retrievals will also be discussed.

Schmid, B.↗
NASA NTRS2006

Regional and Global Aspects of Aerosols in Western Africa: From Air Quality to Climate

Western Africa is one of the most important aerosol source regions in the world. Major aerosol sources include dust from the world's largest desert Sahara, biomass burning from the Sahel, pollution aerosols from local sources and long-range transport from Europe, and biogenic sources from vegetation. Because these sources have large seasonal variations, the aerosol composition over the western Africa changes significantly with time. These aerosols exert large influences on local air quality and regional climate. In this study, we use the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model to analyze satellite lidar data from the GLAS instrument on the ICESat and the sunphotometer data from the ground-based network AERONET taken in both the wet (September - October 2003) and dry (February - March 2004) seasons over western Africa. We will quantify the seasonal variations of aerosol sources and compositions and aerosol spatial (horizontal and vertical) distributions over western Africa. We will also assess the climate impact of western African aerosols. Such studies will be applied to support the international project, Africa Monsoon Multidisciplinary Analysis (AMMA) and to analyze the AMMA data.

Chin, Mian↗