1. Major Determinants of Water Quality

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

3. Solubility The ease with which substances dissolve in water
Salts dissolve to produce ions in solution

4. Ions Ions are stable forms of elements that acquire
an electrical charge by gaining or losing electrons
Sodium ion (Na+)
11 protons (+), 10 electrons (-)
Chloride ion (Cl-)
17 protons (+), 18 electrons (-)
By losing an electron, sodium has more protons than
electrons and becomes positively charged.
By gaining an electron, chlorine has more electrons than
protons and becomes negatively charged.

5. Dissolution and Solubility
Cl- Cl Cl Na Cl Cl
NaCl Solid
Na+

6. Ionic Contaminants Pb2+ Hg2+ AsO4- PO4-3 NH4+ NO3- Weathering of Rock
Cd2+
Natural and anthropogenic sources
Weathering of Rock
Industrial Processes
Agriculture
Solubility depends on the ion to which it is bonded

7. Forms and Solubility Pb2+ Hg2+ AsO4- PO4-3 NH4+ NO3- Cd2+
HgCl2 soluble
PbCO3 poorly soluble
FePO4 poorly soluble
AlPO4 poorly soluble
KH2PO4 soluble
CdCO3 poorly soluble
CdCl2 soluble
carbonates, hydroxides, chlorides or sulphates
The degree to which contaminants impact
water quality is often determined by their solubility

8. Toxic organic pollutants including pesticides, and industrial products generally are not ionic and are not particularly soluble in water.
DDT
Dioxins
PCBs
Dioxin
DDT
PCB

9. Oxygen is also Water Soluble
Solubility: g/L
(20oC)
The diffusion of oxygen is often of great importance in relation to water, particularly in lakes and rivers. Oxygen contents dictate in many ways the life limits of aquatic organisms. We will explore in some detail the factors controlling oxygen contents in water particularly in relation to temperature. The solubility of oxygen is greater in colder water than in warm water.
In water, about one out of every 100,000 molecules is oxygen 9

10. Temperature and Oxygen
The solubility of oxygen in water is
highly temperature dependent.
Saturated Oxygen Content
10.1 mg/L
8.3 mg/L
Temperature is also important because of its influence on water chemistry. The rate of chemical reactions generally increases at higher temperature, which in turn affects biological activity. An important example of the effects of temperature on water chemistry is its impact on oxygen. Warm water holds less oxygen that cool water, so it may be saturated with oxygen but still not contain enough for survival of aquatic life. Some compounds are also more toxic to aquatic life at higher temperatures. Temperature is reported in degrees on the Celsius temperature scale (C).
15oC
25oC

11. Oxygen and Heat Add heat
The diffusion of oxygen is often of great importance in relation to water, particularly in lakes and rivers. Oxygen contents dictate in many ways the life limits of aquatic organisms. We will explore in some detail the factors controlling oxygen contents in water particularly in relation to temperature. The solubility of oxygen is greater in colder water than in warm water.
Add heat 11

12. Activity of Aerobic Heterotrophs
Factors that Control O2 Content in Water
Photosynthesis
Agitation of Water
Temperature
Activity of Aerobic Heterotrophs

13. pH

14. pH is a Measure of H+ Concentration in Water
H+ ion
Responsible for Acidity
Acid: any substance which increases the H+ concentration in water
The greater the number of H+ ions, the greater the acidity
Low pH = High amount of Hydrogen ions in water
High pH = Low amount of Hydrogen ions in water

15. Dissociation of acids
HCl H Cl-
HNO3 H NO3-
H2SO4 H HSO4-

16. * H+ pH (hydrogen) Low pH = High H+ Each unit decrease
in pH represents a
10-fold increase in
H+ concentration *
The pH of a sample of water is a measure of the concentration of hydrogen ions. The term pH was derived from the manner in which the hydrogen ion concentration is calculated - it is the negative logarithm of the hydrogen ion (H+) concentration. What this means to those of us who are not mathematicians is that at higher pH, there are fewer free hydrogen ions, and that a change of one pH unit reflects a tenfold change in the concentrations of the hydrogen ion. For example, there are 10 times as many hydrogen ions available at a pH of 7 than at a pH of 8.
The pH of water determines the solubility (amount that can be dissolved in the water) and biological availability (amount that can be utilized by aquatic life) of chemical constituents such as nutrients (phosphorus, nitrogen, and carbon) and heavy metals (lead, copper, cadmium, etc.). For example, in addition to affecting how much and what form of phosphorus is most abundant in the water, pH may also determine whether aquatic life can use it. In the case of heavy metals, the degree to which they are soluble determines their toxicity. Metals tend to be more toxic at lower pH because they are more soluble.
pH 4 = g H+/ L
pH 3 = g H+/ L
There is 10 times more H+ in water at pH 3 compared to pH 4

17. Extra Credit: ____is a measure of H+ concentration in water
Oxygen is more or less soluble in warm water that cold.
Identify one ionic contaminant.
4. ______are stable forms of elements that acquire
an electrical charge by gaining or losing electrons

18. pH and Availability of Nutrients and Metals

19. pH and Availability and Form of Nutrients
Nitrogen
When organisms decompose organic material
nutrients are released including NH4+
NH4+ NH3
Low pH
High pH
The pH of water determines the solubility (amount that can be dissolved in the water) and biological availability (amount that can be utilized by aquatic life) of chemical constituents such as nutrients (phosphorus, nitrogen, and carbon) and heavy metals (lead, copper, cadmium, etc.). For example, in addition to affecting how much and what form of phosphorus is most abundant in the water, pH may also determine whether aquatic life can use it. In the case of heavy metals, the degree to which they are soluble determines their toxicity. Metals tend to be more toxic at lower pH because they are more soluble.
High H+ conc.
low H+ conc.
soluble
Gas

20. Nitrate and Ammonia NH4+ and NO3- NH4+ dominant at low pH
Forms are controlled by organisms
NH4+ is converted to NO3- by aerobic bacteria
These bacteria, therefore, are controlled by oxygen levels
They also are controlled by pH. They do not function well at low pH.
NH4+ dominant at low pH
NO3- dominant at higher pH

21. Dominant Forms: NH4+ and NO3-
Sources: fertilizers, manures, wastewater discharge
NO3- is more mobile in the environment than NH4+
NH4+ _
Soil particles possess
a negative electrical charge
NO3-
Leaching to ground
or surface water

22. Availability and Form of Nutrients
Phosphorus
dissolved
dissolved
H2PO4-
HPO4-2
Low pH
High pH
High H+ conc.
low H+ conc.
CaHPO4
AlPO4
The pH of water determines the solubility (amount that can be dissolved in the water) and biological availability (amount that can be utilized by aquatic life) of chemical constituents such as nutrients (phosphorus, nitrogen, and carbon) and heavy metals (lead, copper, cadmium, etc.). For example, in addition to affecting how much and what form of phosphorus is most abundant in the water, pH may also determine whether aquatic life can use it. In the case of heavy metals, the degree to which they are soluble determines their toxicity. Metals tend to be more toxic at lower pH because they are more soluble.
Solid
(unavailable)
Solid
(unavailable)
Dissolved
(available)
CaHPO4 + H+ = Ca H2PO4-

23. Acids and Metals

24. Minerals and Erosion Feldspars KAlSi3O8 Al3+ CaAl2Si2O8 NaAlSi3O8
granite
Acid
KAlSi3O8
CaAl2Si2O8
NaAlSi3O8
Al3+
Acid
Dissolved in water
Acid
Aluminum is toxic to plants and some organisms

25. Availability and Form of Metals
PbCO3 + H+ Pb HCO3-
Solid
(unavailable)
dissolved
(available)
CdSO4 + H+ Cd SO4-2
Solid
(unavailable)
dissolved
(available)
The pH of water determines the solubility (amount that can be dissolved in the water) and biological availability (amount that can be utilized by aquatic life) of chemical constituents such as nutrients (phosphorus, nitrogen, and carbon) and heavy metals (lead, copper, cadmium, etc.). For example, in addition to affecting how much and what form of phosphorus is most abundant in the water, pH may also determine whether aquatic life can use it. In the case of heavy metals, the degree to which they are soluble determines their toxicity. Metals tend to be more toxic at lower pH because they are more soluble.
Acid dissolution of metals increases their mobility

26. Mine Tailings There are approximately 420,000 abandoned mines
in the states of California, Arizona and Nevada
Cd, Pb, Zn,
Cr, Cu, Al
FeS2 2H2SO4
oxygen
water
2H+ + SO42-
PbCO3 + H+ Pb HCO3-
solid
soluble
Direct toxicity of H+ plus dissolution of associated metal contaminants such as arsenic, lead, and cadmium

27. pH and Acid Rainfall

28. Natural rainfall is acidic: pH 5.6
CO2 + H2O = H2CO3
H2CO3 => H+ + HCO3-
Acid
Pollution by sulfur dioxide and nitrogen oxides
contributes additional acidity to rainfall.
SO2 + H2O → H2SO4

29. 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
Little Echo is in Franklin NY. pH 6 is 100 times less hydrogen than pH 4.
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.

30. 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

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

32. Next: The History of Sewage