Programme - PTDC/AMB/66198/2006
Execution dates - 2008-01-01 - 2011-06-30 (42 Months)
Funding Entity - FCT; COMPETE
Funding for CESAM - 59478 €
Total Funding - 85758 €
Proponent Institution - Universidade de Aveiro
Universidade dos Açores
Suspended particles in the atmosphere contain a significant fraction of carbonaceous matter, which is generally classified in two major components: black carbon (BC) and organic carbon (OC). BC is essentially a primary pollutant, produced by the incomplete burning of fossil fuels and biomass, and is emitted directly into the atmosphere in particulate form. For this reason it is a good tracer for carbonaceous aerosol of combustion origin. OC has both a primary and a secondary origin. While primary OC is emitted in particulate form, secondary OC is formed in the atmosphere through volatile organic compound gas-to-particle conversion processes.
It is now recognized that increasing concentrations of carbonaceous aerosols in the atmosphere could have significant climatic impacts. In addition to the high light-absorption of black carbon aerosols, an important effect of all the carbonaceous particles could lie in their scattering of incoming radiation as well as the possibility of them being involved in cloud nucleation processes. Despite the potential importance of the presence of carbonaceous particles in the atmosphere, little attention has been paid to the main tropospheric sink for such particles: their scavenging by wet deposition processes. Therefore, this project aims to perform long term measurements of particulate carbon concentrations in rain samples collected simultaneously in a remote marine site (Terceira Island, Azores Archipelago) and a coastal site (Aveiro, west coast of mainland Portugal), in order to: obtain a data base of particulate carbon wet deposition that would be representative of the Northeast Atlantic atmosphere; improve understanding of the processes by which carbonaceous particles are removed from the atmosphere; assess differences in the carbon content of rain as a function of air mass origin and define the relative contributions of natural versus anthropogenic sources of carbonaceous matter; and assess spatial differences in the carbon content of rain between the two sites (a remote pristine and a coastal polluted) for the evaluation of the extent of human impacts on the troposphere.
The research project will be based on two years of daily rain water sampling at both sites, using wet only collectors, and subsequent analysis for the particulate OC/BC content with a thermal-optical method. Sampling at Terceira will take advantage of the excellent facilities that are now available at the Serreta Experimental Observatory, which belongs to the University of the Azores, located on the western shore of the island, in an area isolated from local pollution sources. Sampling at Aveiro will be performed in a site as close as possible to the shoreline in order to minimize the risk of local or regional contamination of samples associated with air mass transport over the Atlantic Ocean. This project as a whole will provide new findings about the environmental consequences of human activity on the atmosphere over the Northeast Atlantic Ocean. Particularly, the information to be gathered from this study will improve the still limited database of particulate carbon wet deposition fluxes from the global atmosphere, which could be used to test regional and global climate models and thus produce more accurate assessments of the climatic effect of carbon particles.