Salts In The Sea PDF

***[Salts in the Sea]*** \- One average 3.5% of seawater is dissolved salt and 96.5% is water \- The salinity of seawater can vary between the ranges of 30-38psu in the ocean (psu = Practical salinity units) \- Used to be determined by evapouration hence the units of: Parts per thousand OR grams...

***[Salts in the Sea]*** \- One average 3.5% of seawater is dissolved salt and 96.5% is water \- The salinity of seawater can vary between the ranges of 30-38psu in the ocean (psu = Practical salinity units) \- Used to be determined by evapouration hence the units of: Parts per thousand OR grams per kilogramme **What is dissolved in sea water:** \- Major constiuents - E.g salt/NaCl \- Minor constiuents - E.g lithium, iodine \- Trace components - generally concentration less than 1 part per billion E.g copper, radionucleotides \- Nutrients (Nitrogen, phosphorus and silicon compounds) \- Gases ( Nitrogen, oxygen, CO2 and inert gases) \- Organics - Not part of salinity - dissolved and particulate material or biological origin E.g discharge and secreation ,Also suspended particulate material may be organic or mineral Alkali metals + Earth metals: Sodium, Magnesium, calcium, potassium and strontium. **Edit - Sodium = 10.76, potassium = 0.39, strontium = 0.008** **Remove borate for boron = 0.004** Halogens: Chloride, bromide, floride \- Sodium Chloride/NaCl = 85% of salts in the sea \- Salts dissociate into cation and anions **See maths book on page 25/10/24** **Minor Constituents and units** \- Lithium - Conc mg/L = 0.18 - Conc ug/L \- Rubidium - **Trace Constituents** \- Heavy metals such as zinc, chromium and copper \- Elements generally form rows 5,6 and 7 of periodic table \- Concentrations of the order of nanomolar (nM) or picomolar (pM) \- Nutrients in a variety of forms E.g for nitrogen \+ Nitrate NO3- \+ Nitrite NO2- \+ Ammonia NH3 \+ Urea \+ Organic Compounds \- Organinc matter - living and dead material made of C, H, O, N, P,S and other non-metals \- Inorganic particles \- Pollutants - Xenobotic compounds and natural compounds in excess **Other Elements:** \- In facts all elements are thought to be pressent in sea water but some at very low concentrations \- These may be elements, complex ions, or molecules. \- The may be dissolved or in particles \- The concentration of some elements in seawater will vary around the globe depending on inputs and outputs - but the major salts remain constant. **How do major salts get into the sea:** -Via riverine inputs - Weathering of earths rocky crust (cations) fluvial inputs \- Vis the atmosphere - Includes volcanic emissions (anions), biogenic, wind blown, cosmogenic materials and may be in rain fall or dry depostitions \- Hydrothermal vents **Composition of earths Crust:** \% by Weight 1\) Si - 28.2% 2\) Al - 8.2% 3\) Fe - 5.6% \- The 3 most abundant elements in the crust do not appear in high concentrstions in the sea, Due to not being very soulable **Insert table of river and seawater comparason** **What happens to river salts:** \- Some are conservative (E.g Na, Mg) these are not changed by biological or chmical processes - These are the key determinants of salinity \- Some are non-conservative (E.g trace materials, NO3-, SO4 2-) and react with chemical or biological processes. Trace metals may precipitate onto particles; nitrate may react to become nitrogen and oxygengases, sulphate may loose oxygen in sediments and become hydrogen sulphate - Bacteria driven reaction. **Residence Time:** \- Firstly assume oceans are at a steady state RT(Years) = Total amount of substance in reservoir (tonnes) / Sum of fluxes into or out of reservoir (tonnes per year) **See Maths book 25/10/24**