The Hydrosphere Like air, water is essential to life as we know it - PDF document

The Hydrosphere • Like air, water is essential to life as we know it • Aesthetic appearance of Environmental Chemistry water often an indicator of quality of the environment environment • ~ 73% of the surface is APCH 211 covered by water (3x greater than land mass) Hydrosphere • All of Earth’s water can be collectively termed as the hydrosphere Layers of the Ocean The Oceans • The epipelagic zone: Surface ‐ down to 200 meters , brightest zone (1 0f 2 with significant amount of light). Zone where most of the familiar creatures of • 97% of earths water is in the sea are found e.g. fish, sharks, squid, plankton, Element PPM etc & find coral reefs. The name "epipelagic" roughly the oceans means "top zone of the ocean.“ Na 10,800 • Most elements can be • The mesopelagic zone: Extends 200 m down to Cl 19,400 around 1,000 m. Also known as the twilight zone. The found in sea water Mg 1,290 name roughly means "middle of the ocean". Less – E.g. Au ~ 0.000011 ppm marine life than the epipelagic zone above because S 904 of lower light penetration. Collectively, the epipelagic g p y, p p g and top of the mesopelagic zones are known as the K 392 photic zone, since light gets to them. Semi ‐ deep sea Ca 411 creatures such as the Swordfish and Wolf Eels live here. Br 67.3 • The bathypelagic zone extends: 1,000 m ‐ 4,000 m. Sr 8 Very little light reaches this depth, & therefore no living plants. Deep sea animals which live here are B 4 adapted to consuming the snow of organic detritus F 1 that continually falls from above. Giant and Colossal Squid can be found here, as well as sperm whales. Most of the animals that live at these depths are black or red in color due to the lack of light. Layers of the Ocean Fresh Water • Abyssopelagic Zone: ‐ The abyssal zone or the abyss. 4000 ‐ 6000 meters. The name comes from a Greek word meaning "no bottom". Water temperature is near freezing, and there is no light at all. Very few creatures can be found at these crushing depths. Most of these are invertebrates such as basket stars and tiny squids. Three ‐ quarters of the ocean and tiny squids. Three quarters of the ocean floor lies within this zone. The deepest fish ever discovered was found in the Puerto Rico Trench at a depth of 27,460 feet (8,372 meters). • Hadalpelagic Zone: Usually deep ocean trenches. 6000 meters to the bottom. The deepest point in the ocean is located in the Mariana Trench off the coast of Japan at 35,797 feet (10,911 meters). The temperature of the water is just above freezing, and the pressure ~ 8 tons per http://ga.water.usgs.gov/edu/waterdistribution.html square inch. Still find life, starfish and tube worms 1

Note on Hydrological Cycle Physical Chemical Properties of Water  – • Polar Molecule • Model that summarizes • Hydrogen Bonding: movement and residence of water in the atmosphere, – Liquid at ambient conditions lithosphere, biosphere, hydrosphere, and anthrosphere – Boiling point higher than expected • Reservoirs include atmosphere, – High specific heat capacity & a oceans, lakes, rivers, soils, High heat of vaporization glaciers, snowfields, and   +   + (regulates earths climate, Oceans (regulates earths climate Oceans groundwater groundwater. absorb over 70% of the heat • Movement from reservoir to reservoir via processes such as generated by atmosphere, sun, evaporation, condensation, etc) heat heat of precipitation, deposition, runoff, Temp. Temp. capacity vaporization infiltration, sublimation, – Strong cohesion and adhesive (°C) (°C) ((J/g K) (kJ/mol) transpiration, melting, and forces (lot of work to dehydrate groundwater flow. 0 45.054 0 4.2176 systems, and dew formation) • Replacement of water in some of 25 43.99 10 4.1921 – Capillary action (helps trees & these reservoirs can take 100’s – 60 42.482 100, 000’s of years! 20 4.1818 plants in general to grow!) 100 40.657 • Human Beings are using these Trenberth et al. Estimates of the Global Water Budget and Its Annual 30 4.1784 – Strong surface tension resources at far greater rates 200 34.962 Cycle Using Observational and Model Data. Journal of 40 4.1785 than the replenishment times Hydrometeorology. 2007, Vol 8, 758 – 769 HEAVY 300 25.3 FIG! Physical Chemical Properties of Water  ice = 0.92 g/cm 3 •  water = 1.0 g/cm 3 • • Density of H2O changes with Temp. • So Ice Floats! – Lakes – Plays a role in circulation of nutrients as seasons change (& Pollutants?) g ( ) H 2 O (s) : each molecule is H 2 O (l) : each molecule is hydrogen bonded to ~4 hydrogen bonded to ~ 3.4 other molecules, more open other molecules Annual circulation patterns in a dimictic (circulates 2x/yr) lake. The typical dimictic lake undergoes & regular ice structure stratification in the summer and complete overturn in the autumn and spring. During winter, surface ice results in greater volume prevents further mixing by the wind. Small differences in density and temperature exist, with cooler occupied by ice & lower water (0° C) staying near the surface and warmer, more dense water (4° C) extending to the bottom. density Ref: circulation: annual patterns of dimictic lakes. Art. Encyclopædia Britannica Online. Web. 25 Mar. 2011. <http://www.britannica.com/EBchecked/media/36/Annual ‐ circulation ‐ patterns ‐ in ‐ a ‐ dimictic ‐ lake>. http://www.grow.arizona.edu/water/density/temperature.shtml Solvent Properties Acid Base Properties • Large dipole moment – Liquid water, molecules are constantly breaking and forming • Amphiprotic (Br ǿ nsted acid or base ) new H – bonds – Able to easily surround ionic or – pH < 7 can be due to organic acids from decaying polar substances organic matter – Process in which water molecules surround a solute involves the – (COOH) 2 + H 2 O ↔ H 3 O + (aq) + COOHCOO – formation of new bonds between (aq) water molecules & solute K a = 5.6 x10 ‐ 2 K a 5.6 x10 – Overall the free energy change is – pH > 7 can be due to soluble carbonate species from negative, favors formation of a hydrated species rocks, etc • “Universal Solvent” • Auto dissociates Hydrophilic – “ Water Water Lov Loving ” i.e. • easily dissolve in water – 2H 2 O ↔ H 3 O + (aq) + OH – Hydrophobic – “ Wate Water Fear Fearing ” i.e. (aq) • K w = 1.01 x10 ‐ 14 @ 25 °C ~ do not dissolve in water • Neutral water has a pH = 7.0 Factors that determine the mechanism via which hydration occurs is still an intense area of R&D, as evidenced by a recent article in the journal Science ( Cooperativity in Ion Hydration. K.J. Tielrooij, N. Garcia ‐ Araez, M. Bonn and H.J. Bakker, Science, 21 May 2010) 2