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When I walk on the beach, there appears to be an upper layer of the sand that is 'crusty'.

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This appears to be the opposite of what you see in sand in a dessert setting, where the individual particles are not bound together, and blow to form 'dunes'.

I'm trying to figure out what causes the sand to bind together like this.

To me the crystalline properties of salt could cause this. (Ie the way that salt binds together to form crystals could cause this salt-binding that leads to 'crustiness'.

My question is: Does the salt in the ocean act as a binding agent on sand?

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    $\begingroup$ The saltwater recrystallizing could definetly aid in forming the crust on top of the sand. There would be no true bonding between the SiO2 and the salts present in the water though they are just crystallizing together. $\endgroup$ – Technetium Jan 11 '16 at 4:05
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    $\begingroup$ Sounds plausible to me. Try it at home, both with salted and pure water; then you'll be able to tell for sure. Chemistry is an experimental science, after all. $\endgroup$ – Ivan Neretin Jan 11 '16 at 7:22
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Good observations!

Seawater contains salts in small amounts such as such as $\ce{LiCl}$ and $\ce{MgCl2}$ that are quite hygroscopic, which could keep the sand wet longer.

There is also dissolved organic matter (http://www.eoearth.org/view/article/154471/) in seawater that might act as a hydrating agent or as a wetting agent, helping to hold onto the water and to bond it to the sand.

You might try an experiment comparing the appearance of (washed) sand after being wet with plain water, with $\ce{NaCl}$ salt water of the same concentration as seawater, and with seawater itself to see if there is a difference. Though this seems like a casual test, this could be of significance in cases where it's necessary to drive on a sandy shore.

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