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BUFFERS

BUFFERS. The neutralization of acid deposition by bases, such as calcium carbonate—whether present in the soil, bedrock, or lake water—prevents the accumulation of hydronium ions . An increase in the concentration of hydronium ions makes a solution more acidic and lowers the solution’s pH.

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BUFFERS

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  1. BUFFERS

  2. The neutralization of acid deposition by bases, such as calcium carbonate—whether present in the soil, bedrock, or lake water—prevents the accumulation of hydronium ions. • An increase in the concentration of hydronium ions makes a solution more acidic and lowers the solution’s pH. • As you will soon see, pH is an important factor that contributes to the viability of ecosystems; and changes in pH can have drastic effects on the survival of many organisms.

  3. Buffers • A buffer is any compound that resists a change in pH of a solution. • Specifically, buffers are weak acids that prevent significant pH changes when small amounts of strong acids or bases are added.

  4. They play an important role in chemical processes where it is essential that a fairly constant pH is maintained. • In many industrial and physiological processes, specific reactions occur at some optimum pH value. • When the pH varies to any extent from the optimum value, undesirable reactions and effects may occur.

  5. Drinking one glass of orange juice has enough acid to lower your blood pH to about 3. You would quickly die if your blood could not neutralize this acid addition.

  6. Examples • For example, the pH of your blood lies at about 7.35-7.45. • If this value drops below 7.0 (acidosis) the results are fatal. • Also if it rises above 7.7 (alkalosis) the results are as well fatal. • Fortunately our blood contains a buffering system which maintains the acidity at the proper level. • If it were not for the protection of the buffering system, we could not eat and adsorb many of the acidic fruit juices and foods in ourdiet.

  7. Student Hand Out

  8. Some areas exposed to acid rain for longer periods of time eventually develop soil or surface water with lower pH values. • In these situations, the accumulation of hydronium ions is due to an absence of basic substances within the soil or water. • Buffering capacity is a measure of the amount of acid that can be neutralized by soil or surface water.

  9. If you look back at “The Potential of Soils and Bedrock to Reduce the Acidity of Atmospheric Deposition” map, can you predict which regions have higher, moderate, and lower buffering capacities?

  10. Response of Plants to pH

  11. Biogeochemical Cycles. • a diagram representing the movement of elements and compounds between living (BIOTIC)and non-living (ABIOTIC) components of an ecosystem. • Carbon, Nitrogen, Oxygen & Water

  12. Reactions involving other elements are of equal importance to environmental scientists. Calcium ions, Ca +2 (aq), are one of the required nutrients for plant growth. • The reaction of CaCO3(s) that neutralizes acids present in rainfall is one manner in which calcium ions—

  13. See page 195 of text for other nutrients present in soil

  14. Plants have an optimal pH for growth. • Many plants also have specific nutrient requirements. • Acid deposition can present another problem that complicates the ability to grow plants or crops. • Nutrients must be in a form that allows them to be absorbed through the roots of plants. • i.e - nitrogen

  15. Problem • A change in soil pH can result in the formation of insoluble forms of these nutrients, making them unattainable by roots.

  16. Leaching of Metals • Extracting a substance from a solid by dissolving it in a liquid; the removal of metal ions from topsoil that allows for their movement into lower levels of soil or into surface water

  17. Leaching of Al +3& Hg +2 Ions • Prolonged acid deposition can cause other compounds to react. • Al(OH)3 – not very soluble • Exposed to acids – Al ions will dissociate in the soil • Thus, accumulate over time

  18. Problem with Increase Al +3Ions in the soil • decreasing the growth of roots • preventing the absorption of calcium • reducing the population of soil bacteria involved in the decomposition of dead plant matter

  19. Higher concentrations of aluminum ions in lakes and streams are toxic to fish. • Exposure to aluminum ions has been known to damage the gills of older fish and increase the number of deaths of young fish.

  20. Mercury II Ions - Hg2+ • Mercury has no real function in living things and cannot be excreted. • Since it is not removed, mercury tends to accumulate within cells and tissues of exposed organisms over their lifetime, often to levels that can be toxic to the organism itself and to any other organism that consumes it.

  21. Acid deposition can cause other metals to have toxic effects on an ecosystem through leaching. • These metals include; • lead, • Zinc • Copper • Cadmium • Chromium • Manganese • vanadium.

  22. Biomagnification • the tendency of a pollutant to appear at higher concentrations at higher levels in a food chain

  23. Homework • Page 198 • Practice Problems #37-40

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