Atmospheric transport of trace elements and nutrients to the oceans

Abstract

This paper reviews atmospheric inputs of trace elements and nutrients to the oceans in the context of the GEOTRACES programme and provides new data from two Atlantic GEOTRACES cruises. We consider the deposition of nitrogen to the oceans, which is now dominated by anthropogenic emissions, the deposition of mineral dust and related trace elements, and the deposition of other trace elements which have a mixture of anthropogenic and dust sources. We then consider the solubility (as a surrogate for bioavailability) of the various elements. We consider briefly the sources, atmospheric transport and transformations of these elements and how this results in strong spatial deposition gradients. Solubility of the trace elements also varies systematically between elements, reflecting their sources and cycling, and for some trace elements there are also systematic gradients in solubility related to dust loading. Together, these effects create strong spatial gradients in the inputs of bioavailable trace elements to the oceans, and we are only just beginning to understand how these affect ocean biogeochemistry.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

Atmospheric Inputs of Iron and Manganese to Coastal Waters of the Southern California Current System: Seasonality, Santa Ana Winds, and Biogeochemical Implications

“…Although in the literature there are recent estimates of trace metals solubility from dust (e.g., Chance et al, ; López‐García et al, ; Mackey et al, ; Ravelo‐Pérez et al, ; Winton et al, ), solubility percentages are usually as variable as reported values of atmospheric dust deposition in the ocean. The reasons for such variability include the origin, load, and geochemical characteristics of dust (Baker et al, ; Jickells et al, ; Sholkovitz et al, ) as well as a lack of consensus among the methodologies used for its estimation (Meskhidze et al, ; Raiswell et al, ; Schulz et al, ). Thus, to calculate the atmospheric supply of soluble metals from the total fluxes of Fe and Mn, we selected as the most representative for our study, Fe and Mn solubility percentages reported for soils from the nearest semiarid region and dust samples from the coastal portion of the CCS.…”

The Cd isotope composition of atmospheric aerosols from the Tropical Atlantic Ocean

“…The Cd and Pb contents of the leachates were subsequently determined by inductively coupled plasma–mass spectrometry (ICP‐MS) (Text S2). Results for the size‐fractionated sample SF7 were reported previously [ Jickells et al , ].…”

Regional trends in the fractional solubility of Fe and other metals from North Atlantic aerosols (GEOTRACES cruises GA01 and GA03) following a two-stage leach

“…Fe solubility estimates range from 0.001 to 90 % (Aguilar-Islas et al, 2010;Baker et al, 2016). The fractional solubility (herein referred to as "solubility") of aerosol TEs is defined in terms of the amount of a TE in solution from any given leach that passes through a filter (usually < 0.45 or 0.2 µm), expressed as a percentage of the total (Baker and Croot, 2010;Baker et al, 2016;Jickells et al, 2016). While this operational definition accounts for some of the variability in published values, it does not account for all of it.…”

“…More recently, the GEOTRACES programme has produced a number of aerosol datasets, which has stimulated further discussion on the use of these data to look for trends that link TE solubility and aerosol source (e.g. Baker et al, 2016;Jickells et al, 2016). Elemental ratios, enrichment factors, and air mass back trajectory (AMBT) simulations have long been used as a first approximation of aerosol source, and there are many studies that employ multivariate statistical analyses for aerosol source apportionment (e.g.…”