Determinants of Water Quality

1
Determinants of Water Quality
2
Basic Types of Pollution
1) Biological 2) Physical 3) Chemical
3
Biological Water Pollution
Develops from microorganisms and their
activities.
4
Physical Pollutants
Heat
Sediment
½ of water withdrawn in the U.S.
Turbidity limits light penetration Particles
carry contaminants
Thermal Shock to organisms Reduction in O2
content.
5
Chemical Pollutants
Nutrients Pesticides Metals Salts Synthetic
Organics
6
Two Basic Avenues of Water Pollution
Non-point source pollution
Diffuse sources Difficult to trace,
regulate Agriculture, Urban Runoff
Point source pollution
Specific entry point Industrial discharges Sewage
treatment plants Landfills
7
Example
Point and Non-Point Pollution
8
Superior
Huron
Ontario
Michigan
Erie
9
Shallowest of the Great Lakes
average depth 62 feet
Buffalo
agriculture
Detroit
Cleveland
Largest population density of Great Lakes
10
Point and Non-Point Source Pollution
Industrial Chemicals
Heavy Metals
Petroleum
Nutrients Pesticides
11
Non-point Source Pollution
Nitrogen and Phosphorus
Blue-green algae phytoplankton
Stimulation of Primary Productivity
Agriculture, Wastewater Discharge, Urban Runoff
12
Point Sources
lip papillomas
Petroleum Organic Chemicals Heavy
Metals Pesticides
13
Petrochemicals
Cuyahoga River Fire (1969)
14
Clean Water Act 1972
15
Determining Water Quality
16
Major Determinants of Water Quality and the
Impact or Availability of Water Pollutants
Organisms Solubility Oxygen pH
17
Determinants of Water Quality
Microorganisms
Pathogenic harmful Non-pathogenic - benign
18
The Earliest Organisms
Autotrophic produce complex organic compounds
from simple inorganic molecules and an
external source of energy.
Organic Carbon-containing
Chemoautotrophs, Cyanobacteria, Plants
19
Autotrophs Plants, Algae, Cyanobacteria
Produce complex organic compounds from carbon
dioxide using energy from light.
energy
light
6CO2 6H2O C6H12O6 6O2
complex organic compound
simple inorganic molecule
Primary producers base of the food chain
20
Heterotrophic Organisms
21
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
autotrophs
Heterotrophs
carbon compounds (C6H12O6)
Consumers
Producers
22
Heterotrophic Organisms
Two Basic Types Related to Oxygen Status
Aerobic
Anaerobic
high oxygen environments
low-oxygen environments
Anaerobic heterotrophs
Aerobic heterotrophs
23
Summary
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
24
Extra Credit
1. Organisms that live in high oxygen
environments are ____
2. ________consume complex carbon compounds for
energy
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
______________________________
25
Heterotrophic Organisms
Aerobic Heterotrophs and Anaerobic Heterotrophs
26
Aerobic Heterotrophic Organisms
27
Aerobic Heterotrophs
Live in high-oxygen environments Consume organic
compounds for energy
Obtain the energy stored in complex
organic compounds by combining them with oxygen
C6H12O6 Oxygen energy
28
Aerobic Respiration
C6H12O6 6O2 ? 6CO2 6H2O
energy
organisms
29
The energy is obtained by exchanging electrons
between carbon and oxygen.
C6H12O6 6O2 ? 6CO2 6H2O
2880 kJ of energy is produced
Aerobic respiration is very efficient, yielding
high amounts of energy
30
Anaerobic Heterotrophic Organisms
31
Anaerobic Heterotrophic Organisms
Live in low-oxygen environments Consume organic
compounds for energy
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 (NO3-) Sulfur (SO42-) Iron (Fe3)
32
Aerobic Respiration
C6H12O6 6O2 ? 6CO2 6H2O
Anaerobic respiration
C6H12O6 3NO3- 3H2O 6HCO3- 3NH4
33
Becoming Anaerobic
34
The oxygen status of water determines and
is determined by the type of organisms
aerobic or anaerobic
Low-oxygen
High-oxygen
Oxygen status also impacts availability and
toxicity of some pollutants
35
Oxygen is Water Soluble
Solubility 0.043 g/L
O2
(20oC)
O2
36
Oxygen enters water from the atmosphere and from
aquatic photosynthetic organisms
Oxygen
Diffusion of O2 through the water and from the
atmosphere into water is generally slow
37
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
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
38
Reduced Oxygen Levels
Oxygen
Slow diffusion
Oxygen is being used by aerobic heterotrophs at
rate faster than it can be replaced
39
Respiration and Still Ponds
O2
Aerobic heterotrophs consume oxygen
Heterotrophic Organisms
NO3-
Anaerobic heterotrophs Use nitrate instead of O2
oxygen
SO4-2
Anaerobic heterotrophs Use sulfate instead of O2
SO4-2 HS-
C6H12O6 3SO42- 3H 6HCO3- 3HS-
40
Anaerobic respiration also is less efficient
and produces less energy than aerobic respiration
C6H12O6 6O2 ? 6CO2 6H2O
2880 kJ
C6H12O6 3NO3- 3H2O 6HCO3- 3NH4
1796 kJ
C6H12O6 3SO42- 3H 6HCO3- 3HS-
453 kJ
41
Carboniferous Period
About 350 million years ago
First land plants 480 mya.
anaerobic
Primitive bark-bearing trees (lignin)
Anaerobic respiration is less efficient, slower,
and produces less energy than aerobic respiration
42
End of lecture 22
43
Solubility
The ease with which substances dissolve in water
44
Sodium Chloride is extremely soluble in water
NaCl Na Cl-
Na
45
The solubility of other ionic salts varies
KCl soluble CaCO3 somewhat soluble HgCl2 soluble
PbCO3 poorly soluble FePO4 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
46
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.
47
Oxygen is also water Soluble
In natural systems, oxygen diffusing from the
atmosphere and from plant photosynthesis
dissolves in water
Oxygen
Slow diffusion
Diffusion of O2 from the atmosphere is generally
slow
48
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
49
Fish Species
Minimum Oxygen Tolerances
Cold water species 5-6 mg/L Trout Cool water
species 4 mg/L Pike Warm water species 2-3
mg/L Bass, Catfish, Bluegill
50
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
51
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 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.
52
pH
53
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, Ca2, NH4, Mg2
Cl-, F-, NO3-, CO32-, SO42-
54
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
55
Common Acids
Hydrochloric Acid HCl Sulfuric Acid H2SO4 Nitric
Acid HNO3 Carbonic Acid H2CO3 Acetic
Acid HC2H3O2 Ammonium NH4
56
Dissociation of acids
57
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
58
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
59
Availability and Form of Nutrients
NH4 NH3
High pH
Low pH
low H conc.
High H conc.
CaHPO4 H Ca2 H2PO4-
Solid (unavailable)
Dissolved (available)
60
Availability and Form of Metals
PbCO3 H Pb2 HCO3-
Solid (unavailable)
dissolved (available)
Dissolution of metals increases their mobility
61
Mine Tailings
There are approximately 420,000 abandoned mines
in the states of California, Arizona and Nevada
Cd, Pb, Zn, Cr, Cu, Al
2H SO42-
PbCO3 H Pb2 HCO3-
soluble
solid
Direct toxicity plus dissolution of associated
metal contaminants such as arsenic, lead, and
cadmium
62
pH and Acid Rainfall
63
Natural rainfall is acidic pH 5.6
CO2 H2O H2CO3
H2CO3 gt H HCO3-
Acid
Pollution by sulfur dioxide and nitrogen
oxides contributes additional acidity to rainfall.
SO2 H2O ? H2SO4
64
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.
65
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