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Adriana Gioda1,
Carlos J. Valle‐Diaz2,
Olga L. Mayol‐Bracero2
1Pontifical University Catholic, Rio de Janeiro, Brazil2Institute for Tropical Ecosystem Studies, University of Puerto Rico, San Juan, PR, USA
The study of chemical composition of clouds is very important to identify local and long‐distance transport of pollutants.
Species present in cloud water can be an essential source of nutrients to the ecosystems.
Measurements in background environments is crucial to understand anthropogenic influences.
Few studies have been done in marine remote areas.
Introduction
PR is located in the tropics. Weather dominated by north‐easterly trade winds minimizing the effects of anthropogenic sources. background aerosols, mineral dust
High frequency of clouds providing a region where the interaction of aerosols with clouds can be studied. Ex. Pico Este
Why Puerto Rico is attractive for cloud and aerosol studies?
Objectives
To identify the origin of air masses sampled.
To determine the impact of African dust on the chemical composition of cloud water collected at Pico Este, PR.
Sampling SitePico Este, Puerto Rico (18o 16' N, 65o 45' W)
Rainforest (El Yunque National Forest) ~ 1050 m aslEcological reserveClouds are present 70% of the yearPeriod: 2004‐2010Experiments:-RICO (Rain In Cumulus over the Ocean Experiment)- PRACS (Puerto Rico Aerosol and Cloud Study)‐PRADACS (Puerto Rico African Dust and Clouds Study)
Rainforest (El Yunque National Forest) ~ 1050 m aslEcological reserveClouds are present 70% of the yearPeriod: 2004‐2010Experiments:-RICO (Rain In Cumulus over the Ocean Experiment)- PRACS (Puerto Rico Aerosol and Cloud Study)‐PRADACS (Puerto Rico African Dust and Clouds Study)
CASCC2: Caltech Active Strand Cloud Water Collector ‐ equipment used to collect cloud water samples.
Sampling
Chemical Analyses
pH, Conductivity,TOC/TN
DOCICICP
ScanningElectronMicroscopy-EnergyDispersiveSpectroscopy(SEM-EDS)
Withoutfiltration
Filtration(quartz filter) Filtration (0.45 µm)
Cloud water
Origin of the Air Masses
Air Mass Backward Trajectories Runs were based on the NOAA ARL HYSPLIT model (HYbrid Single‐Particle Lagrangian Integrated Trajectory (http://ready.arl.noaa.gov/HYSPLIT.php)
Daily AOT Satellite Images Daily satellite images from NOAA / NESDIS (http://www.nrlmry.navy.mil/aerosol/satellite/noaa‐aer/noaa‐daily‐images)
ResultsClean and African Dust Periods
African Dust
CleanN = 25
N = 18
Examples of AOT satellite images and HYSPLIT trajectories
ResultspH and Conductivity in Cloud Water
ResultsOrganic and Nitrogen Concentrations for Cloud Water Samples
ResultsDOC/TOC and ON/TN Ratios
ResultsWater‐soluble Ions and Metals in Cloud Water
Sea salt (Na+, Cl-) - 77%Soil (nss-Ca2+, Fe, Al) - 3%Anthropogenic species - 4%
Sea salt (Na+, Cl-) - 55%Soil (nss-Ca2+, Fe, Al) - 21%Anthropogenic species - 10%
Filtered cloud water
SEM image
The EDS analyses showed that the predominant species (Si, Al, and Fe) were of crustal origin.
Energy Dispersive Spectrometer (EDS)
ResultsChemical Characterization of Insoluble Particles Suspended in Cloud Water – African Dust Period
ResultsAfrican Dust/Clean Concentration Ratios
Conclusions Back trajectories and AOT satellite images provided information in terms of the possible origin of the air masses sampled.
Average pH was higher during African dust (6.3) than clean (5.8) periods probably due to higher concentrations of Ca2+.
The levels of Ca2+, Fe and Al were 5 to 10 times higher during African dust periods.
Organic and nitrogen concentrations were 2 to 4 times higher during African dust periods than in clean.
African dust represent an essential source of cations and nitrogen to Puerto Rican ecosystems.
Thank you for your attention!
Acknowledgments‐ El Yunque National Forest and Conservation Trust of Puerto Rico‐ National Science Foundation for the financial support (Grants ATM
0342548 and DEB 0620910)‐ Dr. Jeff Collett, from Colorado State University, Fort Collins, USA‐ Partners from the Atmospheric Chemistry Laboratory at UPR‐RP‐ IGAC for the travel grant