Atmospheric fluxes of soluble nutrients and Fe: More than three years of wet and dry deposition measurements at Gran Canaria (Canary Islands)

Abstract

Dust inputs to the oligotrophic waters of the subtropical North Atlantic are of significant importance to the biogeochemistry of the region. In this work, we present fluxes of particles, soluble elements (H+, major ions, Fe and organic ions) in dry deposition (DD) and wet deposition (WD) samples collected between September 2012 and April 2016. Positive Matrix Factorization Model (PMF) indicated four dominant factors influencing the elemental concentrations: marine, crustal and two anthropogenic. Soluble Fe fluxes appear to be affected predominantly by aerosol particle type, with higher values observed at lower dust loading. Although WD fluxes made up only a small fraction of total particle fluxes (12%), they represented an important input of soluble Fe and other nutrients such as nitrate (more than 50% of total amount deposited). This significant contribution to total deposition fluxes may have important consequences for primary production in the surface ocean. Mineral dust is the primary source of soluble atmospheric P to the north Atlantic, which is a region that is already P stressed. Our data show that DD dominates the total flux of soluble P to this area (∼87% of the total flux) and it may have a bigger impact in the diazotroph communities during the summer months when the water column is more stratified and nutrient inputs from deeper water are restricted.