title: Wet deposition of particulate carbon to the Central North Atlantic Ocean.
abstract: Elemental carbon (EC) and water-insoluble organic carbon (WIOC) concentrations were measured in wet-only precipitation samples collected on Terceira Island (Azores, Portugal) between December 2009 and October 2010, to investigate temporal variations, source regions and wet deposition fluxes. The global volume-weighted average (vwa) concentrations were 134 ± 19 μgC L(-1) for WIOC and 15.0 ± 1.6 μgC L(-1) for EC, which fall within the range of values that have been found in the European background atmosphere. The WIOC concentration exhibited a temporal variation over the study period with a minimum in winter (vwa 88 ± 16 μgC L(-1)) and a maximum in summer (vwa 477 ± 86 μgC L(-1)). This trend was due to the higher dilution effect of winter rains and possibly to an increase of biogenic particulate carbon incorporation during the growing season. A different temporal variation was observed for the EC concentration with a minimum in summer (vwa 4.2 ± 3.3 μgC L(-1)) and a maximum in spring (vwa 17.5 ± 2.2 μgC L(-1)). The observed trend was mainly related to changes in atmospheric circulation patterns over the Azores. A backward trajectory analysis was applied to identify possible source regions of particulate carbon. The highest WIOC and EC concentrations were associated with air masses that persisted for more than four days over the Central North Atlantic Ocean and with air masses arriving from Europe, respectively. Lower concentrations were observed in samples collected under the influence of back-trajectories from North America. Despite the lower abundance of particulate carbon, the wet deposition fluxes were higher for this group of samples, which reflects the higher amount of precipitation that is normally associated with air masses arriving in the Azores from the west and northwest sectors.
authors: Department of Environment & Centre for Environmental and Marine Studies (CESAM), University of Aveiro, 3810-193 Aveiro, Portugal.
authors: Danilo
authors: D
authors: Custódio
authors: Department of Environment & Centre for Environmental and Marine Studies (CESAM), University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: cerqueira@ua.pt.
authors: Mário
authors: M
authors: Cerqueira
authors: Department of Agrarian Sciences, University of the Azores, São Pedro, 9700-042 Angra do Heroísmo, Portugal.
authors: Paulo
authors: P
authors: Fialho
authors: Department of Environment & Centre for Environmental and Marine Studies (CESAM), University of Aveiro, 3810-193 Aveiro, Portugal.
authors: Teresa
authors: T
authors: Nunes
authors: Department of Environment & Centre for Environmental and Marine Studies (CESAM), University of Aveiro, 3810-193 Aveiro, Portugal.
authors: Casimiro
authors: C
authors: Pio
authors: Afonso Chaves Observatory, Portuguese Institute for the Sea and the Atmosphere, 9500-321 Ponta Delgada, Portugal.
authors: Diamantino
authors: D
authors: Henriques
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001267:Atlantic Ocean; D001272:Atmosphere / Q000737:chemistry; D002244:Carbon / Q000032:analysis*; D004784:Environmental Monitoring; D052638:Particulate Matter / Q000032:analysis*; D011891:Rain / Q000737:chemistry*
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D002244:Carbon
keywords: Background atmosphere; Elemental carbon; Organic carbon; Precipitation; Source apportionment; Wet deposition flux