23 Subsidence Solubility pH

23 Subsidence Solubility pH - Determinants of Water Quality...

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Unformatted text preview: Determinants of Water Quality Continued Major Determinants of Water Quality and the Impact or Availability of Water Pollutants Organisms Solubility Oxygen pH Photoautotrophs – Plants, Algae, Cyanobacteria Produce complex organic compounds from carbon dioxide using energy from light. Primary producers – base of the food chain light 6CO2 + 6H O simple inorganic molecule 2 C6H12O6 + 6O2 complex organic compound Heterotrophs Derive energy from consumption of complex organic compounds produced by autotrophs Autotrophs store energy from the sun in carbon compounds (C6H12O6) Heterotrophs consume these complex carbon compounds for energy C6H12O6 + 6O2 → 6CO2 + 6H2O Heterotrophic Organisms Two Basic Types Related to Oxygen Status Anaerobic low-oxygen environments Anaerobic heterotrophs Aerobic high oxygen environments Aerobic heterotrophs Autotrophs Store energy from the sun in carbon compounds (C6H12O6) Heterotrophs Consume these complex carbon compounds for energy Aerobic heterotrophs High oxygen environments Fast, efficient consumers Rapid decomposition of organic materials Anaerobic heterotrophs low oxygen environments Slow, inefficient consumers Slow decomposition of organic materials Implications for Florida Crops: Everglades Agricultural Area EAA 700,000 ac Alteration of Flow EAA 1940’s thousands of acres converted to agricultural production 1959 1960s Cuban exiles established sugar plantations Sugar production increased 4-fold Today, sugarcane production contributes two-thirds of the economic production of Everglades agriculture, and uses nearly 80% of the crop land in the EAA Sugar 382,000 acres 46% U.S. Palm Beach, Glades, Hendry Florida to Buy Out Sugar Land for Everglades Restoration WTVJ NBC 6 June 25, 2008: WEST PALM BEACH, Florida -- The largest U.S. producer of cane sugar, U.S. Sugar Corp., would close up shop in a $1.34 billion deal to sell its 292 square miles of land to Florida for Everglades restoration, the company president and Florida Governor Charlie Crist said Tuesday. The deal, announced at a news conference at the Arthur R. Marshall Loxahatchee National Wildlife Refuge, allows the state to buy U.S. Sugar's holdings in the Everglades south of Lake Okeechobee, the heart of the wetland ecosystem. 186,000 acres Organic soils possessing high natural fertility Historically flooded Water restricts the movement of oxygen The diffusion of oxygen through water is about 10,000 times slower than diffusion through air Flooded Marsh Under flooded conditions, oxygen levels tend to be low Organisms? Aquatic Plants Die Heterotrophic microorganisms decompose tissues Aerobic heterotrophic organisms use oxygen Oxygen becomes depleted in water; it cannot diffuse fast enough to support aerobic heterotrophs Anaerobic heterotrophs become dominant Anaerobic Heterotrophic Organisms Can use energy stored in complex carbon compounds in the absence of free oxygen The energy is obtained by exchanging electrons with elements other than oxygen. Nitrogen (nitrate) Sulfur (sulfate) Iron (Fe ) 3+ Anaerobic respiration is less efficient and produces less energy. C H O + 6O2 → 6CO + 6H O 2880 kJ 6 2 2 C H 12 6 3NO3- + 3H O = 6HCO + 3NH O+ C6H12O6 + 3SO42- + 3H = 6HCO 3- + 3HS 4+ 2 6 12 6 + 3- 1796 kJ 453 kJ Therefore, anaerobic decomposition is much slower than aerobic decomposition. Flooded Soils anaerobic decomposition of organic matter is much slower than aerobic decomposition. Organic matter is added to the soil faster than it can be decomposed by microorganisms additions Losses (CO2) Organic matter limestone Accumulation of organic matter at the soil surface Buildup of Organic soils Organic matter decomposes slowly when submerged in water. (anaerobic decomposition) Soils throughout the glades historically have been submerged. (anaerobic conditions) Led to vast amounts of organic matter accumulation, sometimes >10 ft. thick. Organic matter continues to accumulate as long as flooded conditions persist. Drainage Drainage exposes soils to oxygen and decomposition by aerobic heterotrophic organisms which can more efficiently decompose organic matter EAA Drainage additions Losses (CO2) Conversion from anaerobic to Aerobic decomposition (much more efficient) C6H12O6 + 6O2 → 6CO2 + 6H2O Losses of organic matter by decomposition exceed new additions – soils disappear Subsidence of Organic soils Greater than 10 feet 1912 to 2000 Florida to Buy Out Sugar Land for Everglades Restoration Good Idea? Extra Credit 1. The # crop grown in the EAA is ____________ 2. Subsidence of organic soils is due to the activity of Aerobic or Anaerobic organisms? 3. anaerobic decomposition is much faster or slower than aerobic decomposition 4. ________ organisms can use energy stored in complex carbon compounds in the absence of oxygen Major Determinants of Water Quality and the Impact or Availability of Water Pollutants Organisms Solubility Oxygen pH Solubility The ease with which substances dissolve in water Sodium Chloride is extremely soluble in water NaCl Na+ + Cl- The solubility of other ionic salts varies KCl CaCO3 HgCl2 PbCO3 FePO4 soluble somewhat soluble soluble poorly soluble poorly soluble The degree to which contaminants impact water quality is often determined by their solubility Solubility also can be influenced strongly by factors such as pH and oxygen content Many toxic organic pollutants including pesticides, and industrial products are extremely insoluble in water. DDT Dioxins PCBs Ironically their insolubility in water is partly responsible for their persistence in the environment. Oxygen is also water Soluble In natural systems, oxygen diffusing from the atmosphere and from plant photosynthesis dissolves in water Oxygen Slow diffusion In the atmosphere, about one out of 5 molecules is oxygen; in water, about one out of every 100,000 molecules is oxygen Temperature and Oxygen The solubility of oxygen in water is highly temperature dependent. Saturated Oxygen Content 10.1 mg/L 15oC 8.3 mg/L 25oC Affects species diversity Example: Fish Species Minimum Oxygen Tolerances Cold water species: 5-6 mg/L Cool water species: 4 mg/L Warm water species: 2-3 mg/L Trout Pike Bass, Catfish, Bluegill Heat also increases Biological activity Slow diffusion of oxygen Warm Water High biotic activity High demand on oxygen Decreased oxygen content Oxygen contents can affect the form, solubility, or toxicity of important contaminants Oxygen Oxygen is water soluble, but its solubility is temperature-dependent. In the atmosphere, about one out of 5 molecules is oxygen; in water, about one out of every 100,000 molecules is oxygen. Oxygen enters the water body from the atmosphere (slowly) and from photosynthesis near the surface Higher temperatures decrease the ability of water to hold or contain O2. Oxygen leaves the water column principally by organism respiration. Higher temperatures can increase biotic activity, decreasing oxygen Oxygen status affects microbial populations and other species diversity as well as the availability or toxicity of important water contaminants. pH pH (hydrogen) H+ ion Elements have equal numbers of protons (+) and electrons (-) Ions are stable forms of elements that result from gaining or losing electrons in chemical reactions Cations have lost electrons and are positively charged Anions have gained electrons and are negatively charged H+, Na , K , Ca , NH , Mg Cl , F , NO , 2+ CO , 4SO + + + +2 pH is based on the abundance of hydrogen ions in water When elemental hydrogen loses its electron it becomes a positively charged ion. 1 Electron (-) Nucleus 1 Proton (+) Hydrogen ions participate in enormous numbers of environmental reactions Common Acids Hydrochloric Acid Sulfuric Acid Nitric Acid Carbonic Acid Acetic Acid Ammonium HCl H2SO4 HNO3 H2CO3 HC2H3O2 NH4+ Dissociation of acids HCl HNO3 H2SO4 H + + Cl - H + + N O 3H+ + HSO4- pH A measure of the amount of Hydrogen ions in water - Log (H ) + Low pH = High amount of Hydrogen ions in water High pH = Low amount of Hydrogen ions in water Low pH: acidic pH (hydrogen) Natural rainfall has a pH of 5.6 H+ Acid: any substance which increases the hydrogen ion concentration in water. - Log (H ) Low pH = High H+ pH 4 = 0.0001 g H / L pH 2 = 0.01 g H / L + There is 100 times more H+ in water at pH 2 compared to pH 4 Availability and Form of Nutrients NH4+ Low pH High H+ conc. NH3 High pH low H+ conc. CaHPO + H = Ca Solid (unavailable) 4 + 2+ + H PO Dissolved (available) 2 4- Availability and Form of Metals PbCO + H Solid (unavailable) 3 + Pb dissolved (available) 2+ + HCO 3- Dissolution of metals increases their mobility Mine Tailings There are approximately 420,000 abandoned mines in the states of California, Arizona and Nevada Cd, Pb, Zn, Cr, Cu, Al oxygen water FeS 2 2H SO 2 4 2H+ + SO42Pb2+ + HCO3soluble PbCO3 + H+ solid Direct toxicity plus dissolution of associated metal contaminants such as arsenic, lead, and cadmium pH and Acid Rainfall Natural rainfall is acidic: pH 5.6 CO + H O = H CO H CO => H + HCO 2 2 2 3 2 3 + 3- Acid Pollution by sulfur dioxide and nitrogen oxides contributes additional acidity to rainfall. SO2 + H2O → H2SO4 National Surface Water Survey (EPA) Investigated the effects of acidic deposition in over 1,000 lakes Acid rain caused acidity in 75 percent of the acidic lakes and about 50 percent of the acidic streams Most lakes and streams have a pH between 6 and 8. In the Northeast U.S. many lakes have pH less than 5. Adirondacks and Catskill Mountains mid-Appalachian highlands Little Echo Pond has a pH of 4.2. The Canadian government has estimated that 14,000 lakes in eastern Canada are acidic. Low pH can be directly toxic to fish and other species As acid rain flows through soils in a watershed, aluminum is released Low pH and increased aluminum levels cause chronic stress that may not kill individual fish, but leads to lower body weight and smaller size and makes fish less able to compete for food and habitat. Acid tolerances food Increasing acidity At pH 5, most fish eggs cannot hatch ...
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This note was uploaded on 02/24/2011 for the course SWS 2007 taught by Professor bonczek during the Fall '09 term at University of Florida.

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