Presentation on theme: "CHEMICAL OCEANOGRAPHY"— Presentation transcript:
1 CHEMICAL OCEANOGRAPHY Aquatic Science*** The ocean is the largest repository of organisms on the planet, with representatives from all phylums.*** Seawater surrounds all marine organisms, composes the greater bulk of their bodies, and is the medium by which various chemical reactions take place, both inside and outside their bodies.
2 seawater: pure water (solvent) plus dissolved solids and gases ((96 seawater: pure water (solvent) plus dissolved solids and gases ((96.5% H2O and 3.5% solute)Dissolved solids come from the weathering processes of continental rockGases come from the atmosphere97.2% of all water on Earth is ocean water (over 285 million cubic miles of water)salts: the solid compound substances in sea water made up of positive and negative ionssalinity: the total amount of solid substances (solute) in the water in ppt (34 to 37 ppt), or ~3.5% salt.
3 Chemical composition of the ocean is divided into four parts: Dissolved Inorganic Matter (chlorine, sodium, magnesium, sulfur)- concentrations of elements can vary with location, time or season, and biological activity- inorganic salts compose most of the solid matter (99.28%) with chloride at ~55% and sodium at ~31%, and includes 11 additional and necessary salts (required for photosynthesis, shell construction, etc)salinity in ppt. = ( )(chlorinity in ppt) because the proportion of chlorinity to salinity is constant
4 2. Dissolved Gas (48% nitrogen, 36% oxygen,15% CO2) - the solubility of the gas depends on temperature of the gas and solution (seasonal), atmospheric pressure of the gas, and salt content of the solution.- oxygen concentrations decrease with depth- two sources of oxygen (atmosphere and ocean plants)- anaerobic organisms live in depths with no oxygen- pH decreases with depth (decrease in plants to remove CO2 which keeps pH stable
5 3. Dissolved Organic Matter (small and variable amounts) 4. Particulate Matter (organic and non-organic materials, including fine-grained minerals)***There are between 100 and bacteria cells per cubic centimeter in just one spoonful of ocean water***
6 Factors that control or influence the chemical composition of the ocean: exchange with the atmospheresolubility of different compoundsreduction by anaerobic bacteriaprecipitation and exchange with the ocean bottominflow of fresh water (also bringing in salts)freezing and melting of sea icechemical reactions that control or influence the concentrations of different elementsbiological processes (including decomposition)temperature (evaporation)
7 Three unique properties of water: dissolving power : makes ocean water nature’s “rich soup”- Water is a MOLECULE (2 hydrogen atoms and one oxygen)A. the hydrogen atoms bond to the oxygen atom by SHARING electrons(COVALENT BONDING). This makes water a stable molecule.B. Water is a POLAR MOLECULE: (contains both charges)The electrical charges of the atoms do not completely cancel each other out.The bigger oxygen atom draws the electrons from the hydrogen closer to itsnucleus, making the oxygen slightly negative and the hydrogen end slightly positive.
8 C. As a result of POLARITY, water molecules cluster (cohesion) as the hydrogen (positive) end of one molecule is attracted to the oxygen (negative) end of another and weak HYDROGEN BONDS are formed between molecules.D. Due to its POLARITY, water is the UNIVERSAL SOLVENT.Any particles that have charges on them (metals +/non-metals ) will be attracted to the oppositely charged ends of the water molecules (adhesion), dissolving.
9 2. surface tension (surface “skin”): Due to COHESION of water molecules water is very DENSE (800X the density of air). This allows organisms to float along effortlessly and lightweight insects to skim across the surface.
10 3. colligative properties (slow but large capacity for absorbing heat): - these properties vary because of the amount of elements in solution and not because of the TYPE of element.Examples:boiling point elevation or heat capacity: a rise in salt levels decreases the amount of heat necessary to raise temperature 1 degreefreezing point depression: a rise in salt levels lowers the freezing point of watervapor pressure lowering: ocean water evaporates more slowly than water without saltsD. osmotic pressure: a rise in salt levels increases osmotic pressure to equalize salinity inside and outside a cell membrane
11 Important People in the Study of Ocean Water Chemistry: Robert Boyle: attributed with the first scientific study of ocean waterLavoisier: discovered that water is a compound of hydrogen and oxygen3. Forchhammer: Principle of Constant ProportionsA. The RATIO of major dissolved components in ocean water is constant.B. Steady State Condition: the amount of an element introduced into the ocean per unit time equals the amount deposited out as sediment per unit time on the ocean floor.C. Residence Time: the amount of an element present divided by the rate the element is added (average length of time an element spends in the ocean)
12 4. Dittmar Challenger Expedition: 3 important findings A. The quantity of one major component in seawater can be used to determine the salinity of seawaterB. Oxygen content decreased with water depthC. Carbon dioxide levels are lower at the surface than in deeper waters.
13 Focuses of Chemical Oceanographers: Increased presence of pollutants in oceanAcid rainEffects of animals and plants on the composition of ocean waterThe effects of increased amounts of carbon dioxide released into the atmosphere and ocean5. Mineral deposits on the ocean floor (manganese nodules, etc)