Chemical and Physical Properties of Water and Water Pollution

1. Chemical and Physical Properties of Water and Water Pollution

2. Physical Properties of Water Polar Molecule: Hydrogen bonding gives water unique properties

3. Properties of Water Cohesion Adhesion Water is capable of performing capillary action • The process of water moving up a narrow tube against the force of gravity • This uses adhesive and cohesive properties as water molecules stick to each other and the sides of a tube • Allows the transport of water in plants

4. Properties of Water Cohesion Adhesion Water has a very high surface tension • The attraction between water molecules creates a strong film • This allows water to hold up substances heavier and denser than itself

5. Properties of Water Specific Heat • Specific heat - Water can absorb a great amount of heat with a relatively small increase in temperature • This property moderates the Earth’s climate and helps organisms regulate body temperature

6. Properties of Water Solvent • Water is a universal solvent due to its polarity • About half of the elements on earth can dissolve in water • Most substances required for life are found dissolved in water • Nutrients, minerals • Pure water has a neutral pH

7. Properties of Water: Phases • Water is the only natural substance on Earth that exists in all three phases

8. Physical Properties: Density • Water density increases to 4 degrees C then density decreases • Water in its solid form is less dense than the liquid state • Allows ice to float on the water surface, trapping warmer water underneath • Prevents water from freezing from bottom up. • Ice forms on the surface first—the freezing of the water releases heat to the water below creating insulation. • Makes transition between season less abrupt.

9. Physical Properties: Temperature oC Corals 28-30 Chinook salmon 10-14 Tilapia 28-30 Pacific shrimp 26-32 • Each species has a characteristic growth curve with an optimum range. • Also have upper and lower temperature limits (lower lethal limit, upper lethal limit). • Outside tolerable temperature range, disease and stress become more prevalent.

10. Lentic (Lake) Systems • Lentic systems are characterized lower oxygen and light levels and • Stratification– layers of water with different temperatures separated by density. • Water temperature/density leads to thermal stratification • Niche differences

11. STRATIFICATION in Lakes

12. The “-Limnions” • The epilimnion, also known as the “photic zone” the top layer of water and where most life is located. • Below this, the metalimnion is dark and cold. This layer experiences a thermocline. • At the bottom, the hypolimnion is very cold and has high nutrient and low oxygen levels thanks to all of the decomposing bacteria and protists.

13. Thermoclineis a layer of water in which a rapid temperature change can be measured as depth increases. Haloclineis a layer of water in which salinity changes rapidly with changes in depth. Pycnoclineis a layer of water in which density changes rapidly with changes in depth. The “-Clines”

14. Turnover in Lakes • In fall, colder days and the wind cool surface water • These denser, cooler waters sink, carrying oxygen down to the depths • This pushes up warmer water (and nutrients) from the lake bed. • These warmer waters cool when they reach the surface start the cycle again. • Good for redistributing oxygen • Bad for redistributing hypolimnion toxins

15. Chemical Properties: Dissolved Oxygen (DO) • Along with temperature, dissolved oxygen (DO), is important in metabolic regulation. • Dissolved oxygenconcentration and temp both determine the environmental niche aquaculture organisms occupy. • Acclimation is slow with D.O. (hours, weeks) • Oxygen depletion is the most important cause of aquatic organism death

16. Chemical Variables: dissolved oxygen (DO) • Although oxygen is rather abundant in the atm (21%), it is only slightly soluble in water (6 mg/L is not much) • Implications to aquatic organisms? • Metabolic rates of communities can effect rapid changes in [D.O.] • this effect increases with temp • Solubilitydecreases withincreasedtemp

17. Chemical Properties: Dissolved Oxygen (DO) • O2 dissolves into water from two sources: • Atmosphere (air water interface) • Aquatic plants and algae (photosynthesis) • Generally organisms need >5ppm DO but that is species dependent • Trout >10ppm Carp 1-2 ppm • O2 is the most important limiting factor in aquatic life

18. Chemical Properties: Dissolved Oxygen (DO) • Amount of DO depends on: • Temperature • Photosynthesis (algae & macrophyte) • Light penetration • Turbulence, air/water mixing • Organic decomposition

19. Chemical Variable: Carbon Dioxide • Normal component of all natural waters. • Sources: atmospheric diffusion, respiration of species, biological oxidation of organic compounds. • CO2 is not particularly toxic to fish or invertebrates, if sufficient D.O. is available. • Maximum tolerance level about 50 mg/L for most species.

20. Chemical Variable: Carbon Dioxide • CO2 dissolves into water and forms carbonic acid: CO2 + H2O H2CO3 • Carbonic acid is a weak acid which dissociates in two steps: • H2CO3 H+ + HCO3- • HCO3- H+ + CO3-2

21. Chemical Variable: Carbon Dioxide • Carbonate ions (CO3-2) interact with cations to precipitate Mg and Ca • Surface water often becomes acidic because atmospheric CO2 dissolves in it. This acidic water can dissolve limestone • Dissolved oxygen and dissolved carbon dioxide are inversely related

22. Carbon Dioxide Sources • Free: CO2 and H2CO3 • Combined: CO3-2 & HCO3- • Free CO2 is corrosive at levels above 25ppm

23. Carbon Dioxide can change the pH of water • This is how it works: • Carbon dioxide dissolves slightly in water to form a weak acid called carbonic acid, H2CO3: CO2 + H2O  H2CO3 • Then, carbonic acid reacts slightly and reversibly in water to form a hydronium cation, H3O+, and the bicarbonate ion, HCO3-: • H2CO3 + H2O  HCO3- + H3O+ • This chemical behaviour explains why water, which normally has a neutral pH of 7 has an acidic pH of approximately 5.5 when it has been exposed to air.

24. CO2 can buffer the pH of watersheds • Rainfall collects dissolved CO2. As rain hits land it moves through soil and saturates with more CO2 in soil creating concentrated carbonic acid • CO2+ H2O  H2CO3 • Carbonic acid comes in contact with calcium rich rock like limestone creating calcium bicarbonate : • CaCO3+ H2CO3Ca(HCO3)2

25. CO2 can buffer the pH of watersheds • Calcium bicarbonate decomposes into calcium carbonate CaCO3, H2O and CO2 • Ca(HCO3)2  CaCO3 + H2O + CO2 • The calcium carbonate CaCO3 precipitates as limestone; H2O and CO2 enter the watershed forming carbonic acid • CO2+ H2O  H2CO3 • Carbonic acid combines with water to form the strong buffer HCO3-. • H2CO3 + H2O  HCO3- + H3O+

26. Lake Nyos

27. Carbon Dioxide Lake Nyos • Cameroon, volcanic lake, sits over active geothermal area • CO2 accumulates in water creating super saturated lake, heat causes violent eruption of CO2 • 1986 eruption of CO2 gas killed 1700 people • Yellowstone?

28. Carbon Dioxide and Blood Chemistry • As pCO2 increases in blood (CO2 concentration) the pH of blood drops = slow respiration rate drops pH • Decreasing pH leads to cellular death

29. Chemical Variables: pH • pH: the level or intensity of a substance’s acidic or basic character. • pH: the negative log of the hydrogen ion concentration (activity) of a substance. • pH of water is stable due to carbonate buffering system unless other forces intervene

30. Chemical Variables: pH • 4. Sources of pH change: • a. Decay of organic matter. • b. Oxidation of compounds in bottom sediments. • c. Depletion of CO2 by phytoplankton on diel basis. • d. Oxidation of sulfide containing minerals in bottom soils

31. Chemical Variables: pH • 5. Fish populations require pH 6.5 – 8.5 few species can tolerate extremes • 6. The pH of water determines the solubility and biological availability of chemical nutrients (P, N, C) and heavy metals (Pb, Cu, Cd). • 7. Metals tend to be more toxic at lower pH because they are more soluble.

32. Chemical Variables: pH • For example, in addition to affecting how much and what form of phosphorus is most abundant in the water, pH also determines whether aquatic life can use it. In the case of heavy metals, the degree to which they are soluble determines their toxicity. • As water bodies age their pH changes due to accumulation of decomposing organic material

33. Chemical Variables: Total Alkalinity • Total Alkalinity: the ability of water to neutralize an acid • “Alkalinity” is primarily composed of the following ions: CO3-, HCO3-, hydroxides, ammonium, borates, silicates, phosphates. • Units are ppm of CaCO3 • Alkalinity in ponds is determined by both the quality of the water and bottom muds. • Thus, a total alkalinity determination of 200 mg/L would indicate good buffering capacity of a water source.

34. Chemical Variables: Total Hardness 1. Total Hardness: total concentration of metal ions expressed in ppm CaCO3. 2. Primary ions are Ca2+ and Mg2+, also Fe and Mn 3. Total Hardness approximates total alkalinity. 4. Geology dependent 5. Calcium is used for bone and exoskeleton formation and absorbed across gills. 6. Soft water = molt problems for crustaceans, bone deformities.

35. Nitrogen • 3 reservoirs in nitrogen cycle: a. Atmosphere b. Inorganic compounds c. Organic compounds (urea, proteins) • Few organisms can use atmospheric nitrogen N2 • Plants use nitrate (NO3-) so N2 must be “fixed” before use • N2 fixed by lightning: N2 + O2 NO2 +H2O HNO3 NO3-

36. Nitrogen

37. Nitrogen • Nitrates absorbed by plants for use in making proteins • Herbivores eat plants and convert to animal protein • Decomposers convert dead plant and animals to ammonia forms of nitrogen: NH3 and NH4+ • Bacteria convert ammonia to nitrate NO3- and nitrite NO2-

38. Nitrogen ammonia NH3 NH4+ • By product of decay • Can indicate sewage pollution • Reacts with chlorine to reduce effectiveness of chorine treatment in waste water facility

39. Nitrogen nitrites NO2- • Formed when bacteria convert ammonia to nitrates • An intermediate compound • Large amounts indicate industrial pollution • Used in large tanks to prevent corrosion • Can cause methemoglobinemia

40. Nitrogen nitrates NO3- • Formed by electrical storms, nitrogen fixing bacteria and break down of ammonia by bacteria Large component of fertilizers • Product of decay • Non-point source pollutant • Nitrates are plant nutrients and with phosphorus cause eutrophication • Can contaminate farm wells: very toxic

41. Phosphorus • 3 forms in aquatic ecosystems: • Phosphates: inorganic PO4-3 • Organic, in tissues of organisms • In dissolved organic molecules • Dissolved phosphorus absorbed by plants and used to make ATP, returned to water when plants die by action of decomposers

42. Phosphorus

43. Phosphorus • Enhances the nitrogen fixing abilities of algae • Key limiting factor • Enters water sheds from sewage, industry, agriculture, animal waste, decaying plants and animals • Removed from detergents but still in household cleaners

44. Total Suspended Solids • Reflects productivity of a water body • Consists of living and dead phytoplankton and zooplankton, silt, human sewage, animal excrement, parts of decaying plants and animals, industrial wastes • Definition: amount by weight of suspended (not dissolved) matter in a given volume of water • Indirectly measured by measuring turbidity (clarity)

45. Total Dissolved Solids • A general assessment of water health • Determines the total concentration of solids dissolved in water • Examples: phosphates, nitrates, alkalis, sulfates, iron, magnesium, acids • Measured by evaporating water sample and weighing remaining solids • Affects water clarity with TSS

46. Temperature • Determines solubility of compounds: gases • Species have narrow thermal preferences and are stressed above and below optimal temperatures • Increased temperatures kill organisms by increasing metabolic rates and removing oxygen from solution • Stratification via temperature of a lake creates unique niches

47. Biological Oxygen Demand • A measurement of the amount of oxygen used in a given water sample over five days • Results are expressed in ppm • Used in wastewater treatment plants and field testing of water bodies • Reflects the amount of decay and bacterial decomposition of plant and animal matter

48. Chemical Oxygen Demand • An indirect measurement of the amount of the decomposition of organic compounds • Standard method for indirect measurement of the amount of pollution that cannot be oxidized biologically, in a water sample • Reflects the amount of decay and bacterial decomposition of plant and animal matter

49. Biological Aspects of Pollution • Indicator species are the first ones to exhibit effects of pollution • Indicator species differ by water body