Water Chemistry Notes Mr. Distasio

Carbon Dioxide (CO2)

• Colorless, odorless gas• Source: Respiration• Removal: Photosynthesis• Highest Levels: at night, on cloudy

days and at high temp. • Fish Tolerance: 20 ppm or mg\L

• H2O + CO2 HCO3 (carbonic acid)

Chlorine (Cl)• Greenish- yellow, poisonous gas (Free Cl - short term)

• Dissolves in H20, combines with decaying material to form trihalomethanes - persistent & carcinogenic

• Sources: pools, sewage treatment, textile industry.• 0.5 ppm kills bacteria, .37 ppm max for fish (coats

gills)

• Becomes more poisonous as pH drops• Chlorides are salts containing Cl and metal

(CaCl, MgCl, NaCl)• Tests: Free: only measures Cl dissolved in H2O Total: measures free Cl and combined

Dissolved Oxygen (DO)

• Sources: Rapids, diffusion from atmosphere, photosynthesis

• 75% of the world's O2 comes from phytoplankton

• Reasons for low O2: Algae blooms (fertilizer runoff, sewage)

High temperature

High cloud cover

High bacteria, Aquatic Animals• Desirable: 5-18 ppm : < 3 = All fish die

• Fish use more oxygen when the H2O is warmer

eg. 77`F =300 mg\hr

40`F= 50-60 mg\hr

H2O Hardness • Calcium (Ca) and Magnesium (Mg)• Natural Source: Limestone (CaCO3)• Limestone is dissolved by acidic H2O (Releases CO2)• < 250 ppm to drink • Specific amounts are necessary for exoskeletons & bone development

Soft H2O = 0-60 mg\L = Makes nonmetals (like Ammonia) more toxic = increases rate for heart attacks in humans = Better to wash clothes in

Hard H2O = 121-180 mg/LCarbonates = Act as buffers to neutralize acids

H2SO4 + CaCO3 H2CO3 + Ca

H2O + SO3 H2SO4 (in acid precipitation)

Nitrates and Nitrites (NO4, NO3)

• Inorganic: Ammonia, gaseous N• Organic (contain C): Amino Acids (Recycled plants and animals)

• Source: fertilizer runoff, sewage

• Excessive phytoplankton uses up O2 in decomposition process

• "Brown Blood disease" - in fish with high nitrites

Blue Baby syndrome - humans, cannot transport O2• Nitrates converted to nitrites Intestines ("Toxic Shock")

(dangerous)

Phosphates (PO4)

• Sources: soil, pesticides, rocks, detergents, organic waste

• Increases plankton growth when concentrations are too high.

• .025 mg/L necessary for eutrophication : < 0.1 ppm desirable

pH acidic basic• 0 <------------------------7--------------------------> 14• Potential for Hydrogen ions [H+]• Each unit represents a 10x change in [ ] • 6.5 - 8.2 best for fish• Older lakes are more acidic due to decomposition &

eutrophication• Hg, Pb, Al (metals) become more toxic in an acidic

environment.• Acid precipitation" = PA #1 in USA, H2SO4 and HNO3

(see notes)

Other chemical parameters • Zn = 5.0 max• Cu = 1.0 max• Detergents = <0.5 max• Fe = 0.3max• Pb = 0.05 max• Al = < 0.05 max• Silica = <60 ppm desirable• Cadmium = 0.01 max• NH4 = 0.06 max• Alkalinity (Desirable 110 ppm) - a measure of

the buffering capacity for a water sample

• Synergistic effect - Two or more substances combine to produce greater effects than their sum.

1 + 1 >2

• Eutrophication – aquatic succession

• Titration – a chemical test used to determine the concentration of a given substance found in a solution.