8.7: Airborne Sources of Salts
- Page ID
- 31643
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Other processes can also contribute elements to the ocean. Transport of aeolian dust, wind-suspended particles of silt, clay, and microorganisms, contributes a small but significant percentage of the substances found in the ocean. These inputs prove especially important to biogeochemical and sedimentary processes in the open ocean, where terrestrial influences are minimal.
British naturalist Charles Darwin (1809–1882) was among the first to publish observations of dust while aboard ship off North Africa. He was also the first to note the presence of microorganisms—“infusoria”—in the material (Darwin 1846):
From the several recorded accounts it appears that the quantity of dust which falls on vessels in the open Atlantic is considerable . . . Lieut. Arlett found the water so discolored that the track left by his ship was visible for a long time. . . . Professor Eherenberg . . . finds that it is in considerable part composed of Infusoria, including no less than sixty-seven different forms.
With the advent of Earth-observing satellites, we now know that billions of tons of dust take to the sky from the major deserts of the world, especially the Sahara Desert in Africa, the Gobi Desert in Mongolia and China, and the Chihuahan Desert in Mexico (e.g., Goudie and Middleton 2006; Rivera Rivera et al. 2009; Ginoux et al. 2012; Wu et al. 2020). Emissions from automobiles, industrial activities, wildfires, and fallout from nuclear testing also contribute contaminants and radioactive particles to the atmosphere, where they may ride with the wind before settling into the ocean.
Dust from the Sahara can influence the development of hurricanes (e.g., Dunion and Velden 2004; Shu and Wu 2009) Iron in Saharan dust may fertilize the Amazon rain forest (e.g., Bristow et al. 2010). Clouds of Saharan dust may even cause regional climate variability (e.g., Evan et al. 2016). Some studies suggest that aeolian iron may contribute to increased productivity of phytoplankton in iron-poor, low-latitude regions of the ocean (e.g., Conway and John 2014). We’re just beginning to understand the ways in which aeolian dust affects processes in the Earth system (e.g., Tagliabue et al. 2017; Liu et al. 2022; Adebiyi et al. 2023).