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

Heat½ of water withdrawn in the U.S.

Thermal Shock to organismsReduction in O2 content.

Sediment

Turbidity limits light penetrationParticles carry contaminants

Chemical Pollutants

NutrientsPesticides

MetalsSalts

Synthetic Organics

Two Basic Avenues of Water Pollution

Point source pollution Specific entry pointIndustrial dischargesSewage treatment plantsLandfills

Non-point source pollution

Diffuse sourcesDifficult to trace, regulateAgriculture, Urban Runoff

Point and Non-Point Pollution

Example

Superior

Michigan

Erie

OntarioHuron

Shallowest of the Great Lakesaverage 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 algaephytoplankton

Nitrogen and Phosphorus

Agriculture, Wastewater Discharge, Urban Runoff

Stimulation of Primary Productivity

Point Sources

lip papillomas

PetroleumOrganic ChemicalsHeavy MetalsPesticides

Cuyahoga River Fire (1969)

Petrochemicals

Clean Water Act: 1972

Determining Water Quality

Major Determinants of Water Qualityand the Impact or Availability of Water Pollutants

OrganismsSolubilityOxygen

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 fromcarbon dioxide using energy from light.

6CO2 + 6H2O C6H12O6 + 6O2

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 (C6H12O6)

Heterotrophs consume these complex carbon compounds for energy

carbon compounds (C6H12O6)

autotrophs Heterotrophs

ConsumersProducers

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

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 organiccompounds by combining them with oxygen

C6H12O6 + Oxygen = energy

Live in high-oxygen environmentsConsume organic compounds for energy

C6H12O6 + 6O2 → 6CO2 + 6H2O

Aerobic Respiration

+ energy

organisms

C6H12O6 + 6O2 → 6CO2 + 6H2O

Electron poor

Electron rich Electron poor

Electron rich

The energy is obtained by exchanging electrons between carbon and oxygen.

2880 kJ of energy is produced

Aerobic respiration is very efficient, yielding high amounts of energy

Anaerobic Heterotrophic Organisms

Anaerobic Heterotrophic Organisms

Can use energy stored in complex carbon compounds in the absence of free oxygen

The energy is obtained by exchangingelectrons with elements other than oxygen.

Nitrogen (NO3-)

Sulfur (SO42-)

Iron (Fe3+)

Live in low-oxygen environmentsConsume organic compounds for energy

C6H12O6 + 3NO3- + 3H2O = 6HCO3

- + 3NH4+

Anaerobic respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O

Electron poor

Electron rich Electron poor

Electron rich

Aerobic Respiration

Electron rich

Electron poor

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: 0.043 g/L(20oC)

Oxygen is Water Soluble

O2

O2

Diffusion of O2 through the water andfrom the atmosphere into water is generally slow

Oxygen enters water from the atmosphereand from aquatic photosynthetic organisms

Oxygen

Diffusion of O2 in water is generally slow

Heterotrophic organisms together with inputs of organic materials (food sources) control the oxygen status of waters.

C6H12O6 + 6O2 → 6CO2 + 6H2O

Accelerated metabolic activity of aerobic heterotrophsdue to an abundance of organic materials (food source)can significantly reduce the amount of dissolved oxygen

Lower dissolved oxygen levels impact species diversityincluding a shift to a dominance of anaerobic microorganisms

Reduced Oxygen Levels

Oxygen is being used by aerobic heterotrophsat rate faster than it can be replaced

Oxygen

Slow diffusion

SO4-2 HS-

O2

NO3-

SO4-2

Respiration and Still Ponds

C6H12O6 + 3SO42- + 3H+ = 6HCO3

- + 3HS-

Heterotrophic Organisms

oxygen

Aerobic heterotrophsconsume oxygen

Anaerobic heterotrophsUse nitrate instead of O2

Anaerobic heterotrophsUse sulfate instead of O2

C6H12O6 + 3NO3- + 3H2O = 6HCO3

- + 3NH4+ 1796 kJ

C6H12O6 + 3SO42- + 3H+ = 6HCO3

- + 3HS- 453 kJ

C6H12O6 + 6O2 → 6CO2 + 6H2O 2880 kJ

Anaerobic respiration also is less efficient andproduces 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, andproduces less energy than aerobic respiration

anaerobic

End of lecture 22

Solubility

The ease with which substances dissolve in water

NaCl Na+ + Cl-Na+

Sodium Chloride is extremely soluble in water

The solubility of other ionic salts varies

KCl solubleCaCO3 somewhat solubleHgCl2 solublePbCO3 poorly solubleFePO4 poorly soluble

The degree to which contaminants can existin 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 includingpesticides, and industrial productsare extremely insoluble in water.

DDTDioxinsPCBs

Ironically their insolubility in water is partly responsibleFor their persistence in the environment.

Oxygen is also water SolubleIn natural systems, oxygen diffusing from the atmosphere

and from plant photosynthesis dissolves in water

Diffusion of O2 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

15oC 25oC

Affects species diversity

Cold water species: 5-6 mg/L TroutCool water species: 4 mg/L PikeWarm water species: 2-3 mg/L Bass, Catfish, Bluegill

Fish Species

Minimum Oxygen Tolerances

Warm WaterHigh biotic activityHigh demand on oxygenDecreased 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 O2.

Oxygen status affects microbial populations and other species diversityas 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+, Ca2+, NH4+, Mg+2

Cl-, F-, NO3-, CO3

2-, SO42-

Elements have equal numbers of protons (+) and electrons (-)

pH is based on the abundance of hydrogen ions in water

When elemental hydrogen loses its electronit becomes a positively charged ion.

Nucleus1 Proton (+)

1 Electron (-)

Hydrogen ions participate in enormousnumbers of environmental reactions

Common Acids

Hydrochloric Acid HClSulfuric Acid H2SO4

Nitric Acid HNO3

Carbonic Acid H2CO3

Acetic Acid HC2H3O2

Ammonium NH4+

HCl H+ + Cl-

HNO3 H+ + NO3-

H2SO4 H+ + HSO4-

Dissociation of acids

pH

A measure of the amount of Hydrogen ions in water

- Log (H+)

Low pH = High amount of Hydrogen ions in waterHigh pH = Low amount of Hydrogen ions in water

Low pH: acidic

pH (hydrogen)

Low pH = High H+

H+

pH 2 = 0.01 g H+/ LpH 4 = 0.0001 g H+/ L

Acid: any substance whichincreases the hydrogen ionconcentration 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

CaHPO4 + H+ = Ca2+ + H2PO4-

Availability and Form of Nutrients

NH4+ NH3

Low pH High pHHigh H+ conc. low H+ conc.

Solid(unavailable)

Dissolved (available)

Solid(unavailable)

dissolved(available)

Availability and Form of Metals

Dissolution of metals increases their mobility

PbCO3 + H+ Pb2+ + HCO3-

There are approximately 420,000 abandoned mines in the states of California, Arizona and Nevada

Mine Tailings

FeS2 2H2SO4

oxygen

water

Direct toxicity plus dissolution of associated metal contaminants such as arsenic, lead, and cadmium

Cd, Pb, Zn,Cr, Cu, Al

PbCO3 + H+ Pb2+ + HCO3-

solid soluble

2H+ + SO42-

pH and Acid Rainfall

Natural rainfall is acidic: pH 5.6

CO2 + H2O = H2CO3

H2CO3 => H+ + HCO3-

Acid

Pollution by sulfur dioxide and nitrogen oxidescontributes additional acidity to rainfall.

SO2 + H2O → H2SO4

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 acidiclakes 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 acidityfood

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 thatmay 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