Why beach sand is salty: notes from a talk by Dr Alan Merriman
These notes summarise a talk given by Dr Alan Merriman, a retired hydrogeologist and member of the association, at the June members' meeting. They have been read by Dr Merriman.
Is sand salty?
Sand itself is only slightly salty. The grains at a beach like Kings Beach are mostly quartz and broken shell. The salt is in the seawater held between the grains, and in the crust left on the surface when that water evaporates. Wind carries more in as spray, and rain washes some of it back down.
How much salt does sand hold?
Using a porosity of 35 per cent, the figure assumed in our working estimate, a saturated cubic metre of sand holds about 350 litres of seawater and around 12.5 kilograms of salt.
How to check the salt content of sand
- Dry a sample of the sand.
- Mix one part sand with five parts distilled water by weight.
- Let the mixture settle.
- Take a conductivity reading of the water.
Sand may not be removed from a nature reserve without authority. Any sampling at Kings Beach would be carried out under the terms of the independent baseline study, once that study is funded.
The Kings Beach Salt Runoff Containment Proposal is a proposal to build a 6 metre concrete wall between the sand and the sea at Kings Beach, Broken Head, NSW, to stop salt reaching the ocean. It has not been approved and no works are scheduled.