Water Pollution:
An Introduction
Outline of Topics
• The Hydrosphere
– Water Reservoirs
– Water Usage in the US
– The Hydrologic Cycle
• Composition of the Hydrosphere
– The Dissolution Process
– Composition of Seawater
– Composition of Rivers
• Water Pollution
–
–
–
–
Changes in River Composition
Westhampton Lake
Water Pollution Overview: Sources, Pollutants
US Water Quality
The Hydrosphere
• Lecture Question
– List the major water reservoirs on Earth – ie, the components of the
hydrosphere – in order of volume (largest to smallest).
Reservoir
Oceans
Cryosphere
Groundwater/Permafrost
Lakes/Rivers
Soil Moisture
Atmosphere
Biomass
Volume, km 3
1.34E+09
96.54%
2.41E+07
1.74%
2.37E+07
1.71%
1.90E+05
0.01%
1.65E+04
0.0012%
1.29E+04
0.0009%
1.12E+03
0.0001%
Avg Turnover Time
2640 yr
8900 yr
515 yr
4.3 yr
52 d
8.2 d
5.6 d
US Freshwater
Usage
Sources of freshwater
• approx 75% surface water
• approx 25% ground water
Uses of freshwater
• agriculture (41%)
• hydro power (39%)
• drinking/washing/etc (12%)
• almost half (48%) supplied
by ground water
• industrial/mining (8%)
Largest Consumption
• agriculture, by far (85%)
The Hydrologic Cycle
• Questions
– What is the hydrologic cycle?
• The hydrologic cycle is the movement of water between its
reservoirs, on either a local or global scale.
– What are the processes by which water circulates between its
reservoirs?
•
•
•
•
Precipitation
Condensation
Evaporation
Transpiration
– Uptake from soil by plants, release as vapor from stomata
• Overland flow
– Surface runoff
– Channel flow
• Groundwater flow
– Baseflow recharges surface water (rivers, lakes, etc)
• Infiltration into the soil
– Mechanism of groundwater recharge
The Hydrologic Cycle
Global Water Balance and Circulation
Volumes: km3
Fluxes: km3/yr
Global Water Balance and Circulation
• Globally: a giant distillation
– There is a net global movement of water
• ocean  atmosphere  land  oceans
– This process concentrates solutes in oceans that were picked during
flow over/through the land
• What happens to water that falls (as precipitation) on the land?
– Can be intercepted by foliage
• Most of this evaporates back into the air
– Can run off over land into a nearby river/lake
– Can penetrate into the ground (infiltration/recharge)
• Soil water: some of this is taken up by roots and transpired back into the air;
some is evaporated (evapotranspiration)
• Ground water: flows underground towards nearby rivers/lakes (base flow)
– Runoff vs infiltration/recharge
• Depends on the vegetation/landscape and the rate of precipitation
Fate of Atmospheric Precipitation
Dissolution of Solids
• Question
– What is a solution? How is it formed?
– Electrolytes vs nonelectrolytes
– Dissolution of solids
• Molecular compounds
• Ionic compounds
Composition of the Hydrosphere
• Lecture Question
– What are the most concentrated solutes in the hydrosphere?
– Cations: Na+, K+, Ca2+, Mg2+
– Anions: Cl-, SO42-, H2CO3/HCO3-/CO32– Neutral: Si(OH)4
Dissolved Solutes in Seawater
-
Br , 0.19%
-
HCO3 , 0.30%
2-
SO4 , 7.72%
typical values
pH: 8.1
TDS (salinity): 35 g/kg
• Proportions are by
mass fraction
• Proportions remain
fairly constant, even
as salinity changes
• Ranges of salinity:
33 – 37 g/kg
+
Na , 30.67%
Mg2+, 3.65%
-
Cl , 55.05%
Ca2+, 1.17%
K+, 1.14%
Dissolved Solutes in Seawater
Na+
Mg2+
Ca2+
K+
Sr2+
Cl
g/kg
10.7838
1.2837
0.4121
0.3991
0.0079
19.3529
g/L
mass fraction
11.0534
30.67%
1.315793
3.65%
0.422403
1.17%
0.409078
1.14%
0.008098
0.02%
19.83672
55.05%
SO4
2.7124
2.78021
7.72%
HCO3
0.107
0.109675
0.30%
Br
CO3
0.0672
0.0161
0.06888
0.016503
0.19%
0.05%
F
B(OH)3
0.0068
0.0045
0.00697
0.004613
0.02%
0.01%
Si(OH)4
0.002
TDS
35.1555
density
1.025
pH
8.1
salinity (g/kg) 33-37
0.00205
36.03439
0.01%
100%
Dissolved Solutes in Rivers
Si(OH)4
Cl
Ca2+
typical values
pH: 7.38.1
TDS (salinity): 70200
9%
13%
Na+
8%
7%
SO4
2+
Mg
10%
+
K
48%
Values from 1980
HCO3
3%
1%
Dissolved Solutes in Rivers
Ca2+
Na+
Mg2+
K+
HCO3
Africa
conc, mg/L
fraction
5.7
9.4%
4.4
7.2%
2.2
3.6%
1.4
2.3%
26.9
44.2%
Asia
conc, mg/L fraction
17.8
13.3%
8.7
6.5%
4.6
3.4%
1.7
1.3%
67.1
50.0%
S. America
conc, mg/L fraction
6.3
11.5%
3.3
6.0%
1.4
2.6%
1.0
1.8%
24.4
44.7%
N. America
conc, mg/L fraction
21.2
14.9%
8.4
5.9%
4.9
3.4%
1.5
1.1%
72.3
50.7%
SO4
4.2
6.9%
13.3
9.9%
3.8
7.0%
18.0
12.6%
Cl
Si(OH)4
TDS
4.1
12.0
60.9
6.7%
19.7%
10.0
11.0
134.2
7.5%
8.2%
4.1
10.3
54.6
7.5%
18.9%
9.2
7.2
142.7
6.4%
5.0%
Ca2+
Na+
Mg2+
K+
HCO3
SO4

Cl
Si(OH)4
TDS
Europe
conc, mg/L
fraction
31.7
15.5%
16.5
8.0%
6.7
3.3%
1.8
0.9%
86.0
42.0%
Oceania
conc, mg/L fraction
15.2
12.2%
7.6
6.1%
3.8
3.1%
1.1
0.9%
65.6
52.9%
35.5
17.3%
7.7
6.2%
20.0
6.8
205.0
9.8%
3.3%
6.8
16.3
124.1
5.5%
13.1%
World Average
conc, mg/L fraction
14.7
13.3%
7.2
6.5% • Concs can be quite
variable.
3.7
3.4%
1.4
1.3% • 98% of all rivers have
Ca2+ and HCO3- as
53.0
48.1%
the principal ions.
11.5
10.4%
8.3
10.4
110.2
7.5%
9.4%
Change in Average River Water Composition (Major Ions)
•
Increases in concentrations of major ions in freshwater due to pollution:
–
–
–
–
–
–
–
•
Ca: +9%
Mg: +8%
Na: +28%
K: +7%
Cl: +30%
SO4: +50% (approx)
HCO3: +2%
Why?
– Irrigation
• Mimics “distillation” process (which causes oceans to be salty) on a local scale
• Water – often from underground – with dissolved solutes is applied to crops. Some
evaporates, concentrating the salts in the soil. These (especially the more mobile ions,
such as Na+ and Cl-) make their way back into local rivers.
– Atmospheric acid deposition
• SO2 emissions will be oxidized in the atmosphere and deposit as sulfate PM.
Water Pollution
• What is wrong with Westhampton Lake?
– Pathogens
• High counts of fecal coliform (human, animal)
– Cultural eutrophication
• Due to nutrient pollution
– Nitrogen: nitrate, ammonium
– Phosphorus: phosphate
• Harmful effects
–
–
–
–
–
Oxygen depletion
Siltation
Decreased light penetration
Increased mobility of toxic metals
Increased production of methane, hydrogen sulfide, other noxious
gases
Classification of Water Pollution
• Biological pollution
– Pathogens (poor sanitation)
– Others: invasive species, eutrophication, etc
• Physical pollution
– Thermal pollution (water used as coolant)
– Siltation (increased TSS), eg due to increased erosion
• Chemical pollution
– Change in chemical composition and toxicity
Water Pollution Overview
• Worst Water Pollution Problems
– Pathogens
• Due to poor sanitation
• Can be a serious problem in developing countries
• WMO estimate: 3.5 million die a year from water-born disease,
mostly children under 2 years old
– Nutrient pollution
• Causes cultural eutrophication, algae blooms, oxygen depletion
– High BOD waste
• Causes oxygen depletion
– Toxic metals
• Sometimes called “heavy” metals
• Lead, mercury, arsenic are the worst offenders
– Toxic organics
• Pesticides, petroleum by-products, solvents, industrial waste, etc
Major Activities that Pollute the Hydrosphere
•
Industrial discharges
– eg, paper and pulp mills, chemical manufacturers, steel plants, textile
manufacturers, food processing plants
•
Sewage discharges
– Discharges of treated sewage from treatment plants; combined sewer overflows
(CSOs)
•
Urban runoff
– Runoff from impervious surfaces (streets, etc)
•
Agricultural operations
– Crop production, livestock operations (esp cafos)
•
Silvicultural operations
– Forest management, tree harvesting, logging road construction
•
Resource extraction
– Mining, petroleum drilling, runoff from mine tailing sites
•
Waste disposal
– Landfill leachate, underground injection, incineration (followed by atmospheric
deposition of pollutants)
•
Hydrologic modification
– Channelization, dredging, dam construction, removal of riparian vegetation,
streambank modification, drainage/filling of wetlands
Water Pollution Summary
Degradation
Major Chemical Pollutants
Major Source Activities
harmful algae blooms
(‘red tides’)
nutrients (inorganic N and P)
domestic and agricultural use of chemical fertilizers;
activities that generate acid rain; discharge of untreated
sewage; large-scale livestock operations
oxygen depletion
nutrients; high-BOD (ie,
biodegradable) pollution; thermal
pollution
chemical fertilizers; acid rain generation; sewage
discharges; livestock operations; power plants
cultural eutrophication nutrients
see above
acidification
SO2, NOx, FeS2
generation of acid rain; drainage of mine waste
increase in salinity
inorganic salts
urban runoff, industrial discharges, irrigation
siltation
particulates of any kind (may also
have adsorbed toxic chemicals)
landscape alteration (e.g. deforestation) causing increased
erosion
toxic metals
Hg, Pb, Cd, As, Cr, Se, Tl, Ni, Ag, many industrial and domestic uses; power plant emissions
Mn, Ba, etc
radioactivity
Sr-90, I-129, Ra-226, U-238,
Rn-222, etc
synthetic organic
pesticides
DDT, atrazine, parathion, aldicarb, pest control (agricultural, municipal, and household use)
many others
petroluem products
various hydrocarbons, including
BTEX and PAHs; gasoline
additives such as TEL and MTBE
other toxic organic
pollutants
PCBs, dioxins, furans, many others industrial and combustion by-products, industrial
discharges, etc
medical uses, coal power plants, nuclear fuel cycle
leaks during storage (above and under ground), spills
during transport, urban runoff
US Water Quality
• Classification
– Good
• Water quality is sufficient to meet all designated uses
– Impaired
• Water quality is insufficient to meet at least one designated use
• State obligated to develop “TMDL” rules for impaired water bodies
• Some Designated Uses (varies by state)
– Food supply
• Fish consumption
• Shellfish consumption
– Water supply
• Public drinking water
• Agricultural (irrigation)
– Recreation
• Swimming (primary contact)
• Boating (secondary contact)
– Ecosystem health
• Aquatic life support
• Wildlife support
US Water Quality: Common Causes of Impairment
Leading Pollutant Sources (US EPA, 2000)
Rank
Rivers
Lakes
Estuaries
Groundwater
1
agriculture
agriculture
sewage discharges
leaky USTs
2
hydrologic
modification
hydrologic
modification
urban runoff
septic tanks
3
urban runoff
urban runoff
industrial
landfills
4
forestry
unspecified nonpoint
sources
atmospheric deposition
fertilizer application
5
sewage discharges
atmospheric deposition
agricultural
industrial
Leading Pollutants/Stressors (US EPA, 2000)
Rank
Rivers
Lakes
Estuaries
Groundwater
1
pathogens
nutrients
toxic metals
VOCs
2
siltation
toxic metals
pesticides
petroleum products
3
habitat alterations
siltation
BOD
toxic metals
4
BOD
TDS
pathogens
pesticides
5
nutrients
BOD
toxic organics
nitrate
Water Quality in the US (2000): Rivers and Streams
•
Overall impairment level
–
•
Leading Polluting Sources
1.
2.
3.
4.
5.
•
39% of rivers and streams are
impaired for their designated use
Agriculture
Hydrologic Modification
Urban Runoff
Forestry
Sewage Discharges
Leading Pollutants/Stressors
1.
2.
3.
4.
5.
Pathogens
Siltation
Habitat Alterations
High BOD
Nutrients
Water Quality in the US (2000): Lakes, Reservoirs, Ponds
•
Overall impairment level
–
•
Leading Polluting Sources
1.
2.
3.
4.
5.
•
45% of lakes, reservoirs, and
ponds are impaired for their
designated use
Agriculture
Hydrologic Modification
Urban Runoff
Unspecified Point Sources
Atmospheric Deposition
Leading Pollutants/Stressors
1.
2.
3.
4.
5.
Nutrients
Toxic Metals
Siltation
TDS (ie, high salinity)
High BOD
Water Quality in the US (2000): Estuaries
•
Overall impairment level
–
•
Leading Polluting Sources
1.
2.
3.
4.
5.
•
51% of estuaries are impaired for
their designated use
Sewage Discharges
Urban Runoff
Industrial
Atmospheric Deposition
Agricultural
Leading Pollutants/Stressors
1.
2.
3.
4.
5.
Toxic Metals
Pesticides
High BOD
Pathogens
Toxic Organics
Water Quality in the US (2000): Great Lakes
•
Overall impairment level
–
•
Leading Polluting Sources
1.
2.
3.
4.
5.
•
78% of Great Lakes Shoreline
waters are impaired for their
designated use
Contaminated Sediments
Urban Runoff
Agricultural
Atmospheric Deposition
Habitat Modification
Leading Pollutants/Stressors
1.
2.
3.
4.
5.
Toxic Organics
Nutrients
Pathogens
Siltation
High BOD
Virginia Water Quality
VA Water Quality
•
Leading causes of impairment
– Rivers
•
•
Major: Pathogens (fecal coliform, e coli)
Others (minor): DO, pH, freshwater benthics, PCBs in fish
– Lakes
1. DO
2. PCBs in fish
– Estuaries (Chesapeake)
1. PCBs in fish
2. DO
3. Benthics (more minor)
VA Water Quality Trends
VA Chesapeake Bay: Oxygen Depletion
VA Chesapeake Bay: Submerged Aquatic Vegetation
• SAV goal: 77,463 acres
– 37,640 acres attained
– 38,823 acre shortfall