Determinants of Water Quality

1) Biological 2) Physical 3) Chemical Basic Types of Pollution

Develops from microorganisms and their activities. Biological Water Pollution

Physical Pollutants Heat ½ of water withdrawn in the U.S. Thermal Shock to organisms Reduction in O 2 content. Sediment Turbidity limits light penetration Particles carry contaminants

Chemical Pollutants Nutrients Pesticides Metals Salts Synthetic Organics

Two Basic Avenues of Water Pollution Point source pollution Specific entry point Industrial discharges Sewage treatment plants Landfills Non-point source pollution Diffuse sources Difficult to trace, regulate Agriculture, Urban Runoff

Point and Non-Point Pollution Example

Superior Michigan Erie Ontario Huron

Shallowest of the Great Lakes average depth = 62 feet agriculture Largest population density of Great Lakes Detroit Cleveland Buffalo

Heavy Metals Point and Non-Point Source Pollution Industrial Chemicals Petroleum Nutrients Pesticides

Non-point Source Pollution Blue-green algae phytoplankton Nitrogen and Phosphorus Agriculture, Wastewater Discharge, Urban Runoff Stimulation of Primary Productivity

Point Sources lip papillomas Petroleum Organic Chemicals Heavy Metals Pesticides

Cuyahoga River Fire (1969) Petrochemicals

Clean Water Act: 1972

Determining Water Quality

Major Determinants of Water Quality and the Impact or Availability of Water Pollutants Organisms Solubility Oxygen pH

Microorganisms Pathogenic – harmful Non-pathogenic - benign Determinants of Water Quality

Autotrophic: produce complex organic compounds from simple inorganic molecules and an external source of energy. The Earliest Organisms Chemoautotrophs, Cyanobacteria, Plants Organic = Carbon-containing

Autotrophs – Plants, Algae, Cyanobacteria Produce complex organic compounds from carbon dioxide using energy from light. 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 light simple inorganic molecule complex organic compound energy Primary producers – base of the food chain

Heterotrophic Organisms

Heterotrophs Derive energy from consumption of complex organic compounds produced by autotrophs Autotrophs store energy from the sun in carbon compounds (C 6 H 12 O 6 ) Heterotrophs consume these complex carbon compounds for energy carbon compounds (C 6 H 12 O 6 ) autotrophs Heterotrophs Consumers Producers

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 (C 6 H 12 O 6 ) Heterotrophs consume these complex carbon compounds for energy There are two types of heterotrophic organisms: aerobic and anaerobic Aerobic: high oxygen environments, Anaerobic: low oxygen environments Summary

Extra Credit: 2. ________consume complex carbon compounds for energy 1. Organisms that live in high oxygen environments are ____ 3. Organisms that are directly harmful to health are called ___ 4. Organisms that produce complex organic compounds from simple inorganic molecules and an external source of energy are called ______________________________

Aerobic Heterotrophs and Anaerobic Heterotrophs Heterotrophic Organisms

Aerobic Heterotrophic Organisms

Aerobic Heterotrophs Obtain the energy stored in complex organic compounds by combining them with oxygen C 6 H 12 O 6 + Oxygen = energy Live in high-oxygen environments Consume organic compounds for energy

C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O Aerobic Respiration + energy organisms

C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O Electron poor Electron richElectron poor Electron rich The energy is obtained by exchanging electrons between carbon and oxygen kJ of energy is produced Aerobic respiration is very efficient, yielding high amounts of energy

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 (NO 3 - ) Sulfur (SO 4 2- ) Iron (Fe 3+ ) Live in low-oxygen environments Consume organic compounds for energy

C 6 H 12 O 6 + 3NO H 2 O = 6HCO NH 4 + Anaerobic respiration C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O Electron poor Electron richElectron poor Electron rich Aerobic Respiration Electron rich Electron poor Electron rich

Becoming Anaerobic

The oxygen status of water determines and is determined by the type of organisms aerobic or anaerobic High-oxygen Low-oxygen Oxygen status also impacts availability and toxicity of some pollutants

Solubility: g/L (20 o C) Oxygen is Water Soluble O2O2 O2O2

Diffusion of O 2 through the water and from the atmosphere into water is generally slow Oxygen enters water from the atmosphere and from aquatic photosynthetic organisms Oxygen

Diffusion of O 2 in water is generally slow Heterotrophic organisms together with inputs of organic materials (food sources) control the oxygen status of waters. C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O Accelerated metabolic activity of aerobic heterotrophs due to an abundance of organic materials (food source) can significantly reduce the amount of dissolved oxygen Lower dissolved oxygen levels impact species diversity including a shift to a dominance of anaerobic microorganisms

Reduced Oxygen Levels Oxygen is being used by aerobic heterotrophs at rate faster than it can be replaced Oxygen Slow diffusion

SO 4 -2 HS - O2O2 NO 3 - SO 4 -2 Respiration and Still Ponds C 6 H 12 O 6 + 3SO H + = 6HCO HS - Heterotrophic Organisms oxygen Aerobic heterotrophs consume oxygen Anaerobic heterotrophs Use nitrate instead of O 2 Anaerobic heterotrophs Use sulfate instead of O 2

C 6 H 12 O 6 + 3NO H 2 O = 6HCO NH kJ C 6 H 12 O 6 + 3SO H + = 6HCO HS kJ C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O 2880 kJ Anaerobic respiration also is less efficient and produces less energy than aerobic respiration

Carboniferous Period About 350 million years ago First land plants: 480 mya. Primitive bark-bearing trees (lignin) Anaerobic respiration is less efficient, slower, and produces less energy than aerobic respiration anaerobic

End of lecture 22

Solubility The ease with which substances dissolve in water

NaClNa + + Cl - Na + Sodium Chloride is extremely soluble in water

The solubility of other ionic salts varies KClsoluble CaCO 3 somewhat soluble HgCl 2 soluble PbCO 3 poorly soluble FePO 4 poorly soluble The degree to which contaminants can exist in water 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 Diffusion of O 2 from the atmosphere is generally slow Oxygen Slow diffusion

Temperature and Oxygen The solubility of oxygen in water is highly temperature dependent. Saturated Oxygen Content 10.1 mg/L 8.3 mg/L 15 o C 25 o C Affects species diversity

Cold water species: 5-6 mg/LTrout Cool water species: 4 mg/LPike Warm water species: 2-3 mg/LBass, Catfish, Bluegill Fish Species Minimum Oxygen Tolerances

Warm Water High biotic activity High demand on oxygen Decreased oxygen content Slow diffusion of oxygen Oxygen contents can affect the form, solubility, or toxicity of important contaminants Heat also increases Biological activity

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 Oxygen leaves the water column principally by organism respiration. Higher temperatures increase biotic activity, decreasing oxygen Higher temperatures decrease the ability of water to hold or contain O 2. 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 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 2+, NH 4 +, Mg +2 Cl -, F -, NO 3 -, CO 3 2-, SO 4 2- Elements have equal numbers of protons (+) and electrons (-)

pH is based on the abundance of hydrogen ions in water When elemental hydrogen loses its electron it becomes a positively charged ion. Nucleus 1 Proton (+) 1 Electron (-) Hydrogen ions participate in enormous numbers of environmental reactions

Common Acids Hydrochloric AcidHCl Sulfuric AcidH 2 SO 4 Nitric AcidHNO 3 Carbonic AcidH 2 CO 3 Acetic AcidHC 2 H 3 O 2 AmmoniumNH 4 +

HClH + + Cl - HNO 3 H + + NO 3 - H 2 SO 4 H + + HSO 4 - Dissociation of acids

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) Low pH = High H + H+H+ pH 2 = 0.01 g H + / L pH 4 = g H + / L Acid: any substance which increases the hydrogen ion concentration in water. - Log (H + ) Natural rainfall has a pH of 5.6 There is 100 times more H+ in water at pH 2 compared to pH 4

CaHPO 4 + H + = Ca 2+ + H 2 PO 4 - Availability and Form of Nutrients NH 4 + NH 3 Low pH High pH High H + conc. low H + conc. Solid (unavailable) Dissolved (available)

Solid (unavailable) dissolved (available) Availability and Form of Metals Dissolution of metals increases their mobility PbCO 3 + H + Pb 2+ + HCO 3 -

There are approximately 420,000 abandoned mines in the states of California, Arizona and Nevada Mine Tailings FeS 2 2H 2 SO 4 oxygen water Direct toxicity plus dissolution of associated metal contaminants such as arsenic, lead, and cadmium Cd, Pb, Zn, Cr, Cu, Al PbCO 3 + H + Pb 2+ + HCO 3 - solid soluble 2H + + SO 4 2-

pH and Acid Rainfall

Natural rainfall is acidic: pH 5.6 CO 2 + H 2 O = H 2 CO 3 H 2 CO 3 => H + + HCO 3 - Acid Pollution by sulfur dioxide and nitrogen oxides contributes additional acidity to rainfall. SO 2 + H 2 O → H 2 SO4

The Canadian government has estimated that 14,000 lakes in eastern Canada are acidic. 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 Adirondacks and Catskill Mountains mid-Appalachian highlands Little Echo Pond has a pH of 4.2. Most lakes and streams have a pH between 6 and 8. In the Northeast U.S. many lakes have pH less than 5.

Acid tolerances Increasing acidity food As acid rain flows through soils in a watershed, aluminum is released Low pH can be directly toxic to fish and other species 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. At pH 5, most fish eggs cannot hatch