Soluble trace metals in aerosols over the tropical south-east Pacific offshore of Peru

Abstract

Abstract. Bulk aerosol samples collected during cruise M91 of FS Meteor off the coast of Peru in December 2012 were analysed for their soluble trace metal (Fe, Al, Mn, Ti, Zn, V, Ni, Cu, Co, Cd, Pb, Th) and major ion (including NO − 3 and NH + 4 ) content. These data are among the first recorded for trace metals in this relatively poorly studied region of the global marine atmosphere. To the north of ∼ 13 • S, the concentrations of several elements (Fe, Ti, Zn, V, Ni, Pb) appear to be related to distance from the coast. At the south of the transect (∼ 15-16 • S), elevated concentrations of Fe, Cu, Co, and Ni were observed, and we calculated dry deposition fluxes of soluble Cu approximately an order of magnitude higher than a recent model-based estimate of total Cu deposition to the region. The model did not take account of emissions from the large smelting facilities in the south of Peru and northern Chile, and our results may indicate that these facilities constitute an important source of trace metals to the region. Calculated dry deposition fluxes (3370-17800 and 16-107 nmol m −2 d −1 for inorganic nitrogen and soluble Fe respectively) indicated that atmospheric input to the waters of the Peru upwelling system contains an excess of Fe over N, with respect to phytoplankton requirements. This may be significant as primary production in these waters has been reported to be limited by Fe availability, but atmospheric deposition is unlikely to be the dominant source of Fe to the system.

Atmospheric transport of trace elements and nutrients to the oceans

“…This approach has been used to provide a global model of atmospheric copper inputs to the ocean [63] which does illustrate that for this trace element both anthropogenic and dust sources are important, consistent with an observed average enrichment of copper globally [64]. In general, anthropogenic trace element emissions will be from highly populated and industrialized regions and hence the deposition patterns for such emissions is likely to be more similar to that of nitrogen than dust, but there are additional important source regions for some trace elements associated with regions of major mining and smelting activity, such as in the coastal regions of Peru and northern Chile [65]. Figure 5 shows the distribution of some trace elements sampled along the track of the D361 cruise and the average concentrations in different air masses are reported in table 4.…”

N<sub>2</sub> fixation in eddies of the eastern tropical South Pacific Ocean

“…Therefore, the availability of reduced carbon compounds may essentially control N 2 fixation in mode water eddies. Assuming that organic-matter export is limiting for N loss as previously suggested (Babbin et al, 2014;Ogawa et al, 2001;Bianchi et al, 2014) and that deep-water N 2 fixation is a non-cyanobacterial (i.e., heterotrophic) process as shown by the diversity of the diazotrophs and the stimulation of N 2 fixation rates after glucose addition, the interplay between both may be even closer than previously thought.…”

Water column biogeochemistry of oxygen minimum zones in the eastern tropical North Atlantic and eastern tropical South Pacific oceans

“…Several studies have highlighted the importance of atmospheric Fe supply to the ETNA (Voss et al, 2004; as a major factor of primary production. However, a comparable atmospheric Fe source is missing in the ETSP (Baker et al, 2016). Previous studies (Scholz et al, 2014) have identified the ETSP Fe supply as benthic; however, the question of how much Fe is transported from the sediments to the sea surface has not yet been fully clarified.…”