Determination and source apportionment of major and trace elements in atmospheric bulk deposition in a Caribbean rural area

Atmospheric deposition is considered to be the major pathway by which substances from the atmosphere enter to the terrestrial and aquatic ecosystems. This study constitutes the first exhaustive report on trace metal deposition in Cuba and is aimed to determine the monthly atmospheric flux of 47 major and trace elements in a Caribbean coastal site and investigate the main sources contributing to deposition. Bulk deposition (average of 46 018 mu g m(-2) day(-1)) and fluxes of studied elements showed a high variability and no seasonality with the dry and wet periods, results that we attributed to the fluctuations of the emissions from their main sources rather than to meteorological factors controlling the deposition processes. However, stronger correlations were found between typical crustal elements, which showed a marked seasonality with the presence of African cloud dust in the Caribbean. Lanthanoids element (Eu anomalies and La-N/Lu-N ratios) helped us to confirm the seasonal influence of African dust in the geochemical composition of bulk deposition in Cienfuegos. Most of the analysed elements were found in the range of variation of those reported in rural environments around the world but, the elements V, Ni, As and Sb reached higher levels, typically found in urban and industrial areas. The elements Sb, Pb, W, Sn, S, Cu, Mo, Nb and P were moderately enriched (10 < EF < 100) and Zn was highly enriched (EF > 100), indicating they were mainly derived from anthropogenic sources. The La/V ratios were found to be exclusively lower than 0.06 suggesting a strong influence of anthropogenic V emissions from industries with oil and/or petroleum-coke combustion processes. However, we found that V have a predominantly natural origin in the studied region which appear to be related with deposition processes dominated by large particles. Finally, Principal Component, Multilinear Regression and Cluster analyses led the identification of 5 main sources contributing to the bulk deposition: crustal matter (39.5%), marine aerosol (38.2%), combustions including the wastes incineration, wood and fossil fuel burning (6.7%), industries (8.7%) and road traffic (1.4%).