For seawater about 10ppb.
Seawater is neither a compound nor an element but a mixture including much dissolved solid and usually microorganisms as well.
Salinity
Chemical weathering and out gassing
Because seawater is made up of many elements that can be seperated.
oxygen \
Dissolved salts are transported by the rivers.
The most negatively charged ion dissolved in seawater is chloride. In fact, Cl- makes up 55 percent of the seawater's salinity.
Desalination.
Concentration range of seawater acidity
5 grams
For seawater about 10ppb.
sodium and chlorine
It is dissolved salts, gases, and nutrients that are presented in seawater.
Steel is corroded by the oxygen that is dissolved in water, and in the case of seawater, the process is catalysed by the salt in the water.
yes
outgassing of elements from Earth's interior.