Chapter 17: Pollution of Soil, Air, and Water

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Chapter 17 Pollution of Soil, Air, and Water
Homework See handout
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• Preview
• Soils act both as filters (chemical, physical,
  biological) and sometimes as pollutants
  (sediment, P, Se)
• Definition of pollution "Something added to air,
  soil, water making it less desirable for people's
  use or less able to maintain nature's balance."
• The first part is a very honest definition the
  second part is people-oriented, also.
• Protection of wilderness areas is not for the
  wilderness areas, but also because people want
  it.
• All revolves around people, whether they admit it
  or not.

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• Threats to the environment
• Loss of biodiversity somewhat controversial.
  (Who cares?)
• Landscape modification
• Overexploitation - too much logging, farming
• Introduction of alien species - major increasing
  problem. Cheatgrass and white top examples
  locally
• Cumulative changes in biogeochemical cycles
  Ozone, global CO2, acid rain, Hg
• Pollution of fresh water has long been a
  problem, Tahoe is a local example.
• Also, salt water pollution from land sources is
  occurring in the Baltic and in North Carolina
  esturaries
• Salinization

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• Plant nutrients
• N and P are the major culprits
• N mostly as NO3- (mobile) P mostly attached to
  sediments (erosion) in nature.
• P most frequently limiting for primary
  productivity in surface waters because of its
  immobility in soils.

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• Plant nutrients
• Eutrophication overabundance of nutrients in
  water, causing increased primary productivity and
  loss of clarity.
• Usually caused by P inputs via wastewaters
  (sewage, detergents) and/or erosion
• Tahoe example.
• For non-point source pollution, this is a big
  problem in terms of measuring inputs and who to
  blame.

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• Nitrogen in groundwater
• Recall that 1) inorganic N does not accumulate in
  soils, and 2) NO3- is highly mobile.
• Thus, nitrification and NO3- leaching can be
  major environmental problems
• Methemoglobinemia
• NO3- converts to NO2- in digestive tract
• NO2- goes into bloodstream and oxidizes
  oxyhemoglobin (the O2 carrier) to methamoglobin
  (which cannot carry O2)
• Blue babies
• When 70 oxyhemoglobin is used ? death
• Drinking water standard 10 mg L-1 (ppm) NO3- -N
  (atomic wt 14) 45 mg L-1 (ppm) NO3- (atomic
  wt 62)

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• Book gives these N sources for USA
• Soil humus 37
• Human and animal manures 22
• N2 fixation 18
• Rainfall 9
• Fertilizer 13
• Humus rarely releases its N unless plowed or
  plant uptake is precluded by harvesting/herbicide
• Rainfall should include dry dep and can be a big
  source to natural systems
• N2 fixation can be a major source locally

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• Tahoe pollution
• Secchi depth has been declining since the 1960s
• Shift from N to P limitation in last few years
• Potential causes of Tahoe decline
• Development homes, ski areas, erosion
• Air pollution (long and short range)
• Leaky sewer lines
• Riparian N2 fixers (Mt. Alder, Ceanothus?)

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Table 16-2
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• Organic Wastes
• COD (chemical oxygen demand) measure of
  decomposable material and other O2 consumers in
  water
• BOD O2 by biology
• Wastewaters, sludges
• Used to be dumped directly into natural waters
  (fresh and salt) high COD and BOD
• Ban on ocean dumping in 1992 plants located near
  water had a logistical problem
• Now treated and/or applied to land, providing
  nutrients to plants (N, P) and using soil as
  filter. "Biosolids"

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• Organic Wastes
• Biosolids contain good nutrients (Table 17-2)
• However, the problem still is NO3- leaching and
  also heavy metal bioaccumulation (especially Cd)
• Cd standards (Table 17-3)
• 0.5 kg ha-1 yr-1
• 5 kg ha-1 total
• 5 mmolc kg in soil (wow!!)

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• Animal wastes
• Becoming an increasing problem in southeast
  (chickens, pigs)
• Estuary pollution in NC eats skin off fish from
  algal toxin stimulated by high N in runoff

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• Pesticides
• DDT a magic substance
• Invented in the 1880's not used as a pesticide
  until 1938
• Low toxicity to humans and animals
• Inexpensive, long-lasting
• Nobel prize to Müller in 1948 for it millions
  saved from malaria and typhus
• Problems
• Half life too long (10-25 yr)
• Accumulates in animal fat
• Biomagnified up the food chain killed some birds

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• Pesticides
• No observable effect level (NOEL) Fig 17-7
• Set to 0.001 for carcinogens
• Set to 0.01 for non-carcinogens
• Pesticides today have these characteristics
• Short half life (no biomagnification)
• Not carcinogenic, teratogenic
• Effective but can be safely handled

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• Pesticide problems and extent of pollution
• Resistance must constantly change to meet this
  challenge
• Groundwater pollution groundwater, but still an issue
• Many previous applications of long half life
  pesticides may be on their way to groundwater now
• Thus, groundwater pollution is a major problem
  even if we have cleaned up our act.

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• Alternatives to pesticides
• Book has good point about societal costs and
  benefits of pesticides
• Some still argue for DDT (malaria, typhus)
• Should be a matter of judgment but in fact is
  usually a matter of PR
• Biological control
• Parasites on pests (Bacillus thuringensis is a
  good example)
• Cultural control
• Burning, residue management, crop rotation.
• This is the only way to treat bark beetles

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• Alternatives to pesticides
• Breeding - very slow
• Male sterilization - very slow
• Natural chemicals (pheromones - Blomquist at UNR
  is exploring this)
• Integrated pest management all or some
  combination of the above

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• Toxic elements in soils
• Even pure distilled water will leach toxic
  elements from arid soils
• Se problem caused by this also Mo and B
• Se has a narrow sufficiency threshold
• Too little leads to cancer and heart disease
• Too much to acute toxicity
• Selenate anion (SeO42-) easily leaches from soils
  and accumulates in arid lowland areas like San
  Juaquin Valley and waters like Salton Sea in CA
• Bird kill in Salton Sea in 1992 linked to Se
• Lahotan/Carson sink also have Se problems

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• Toxic elements in soils
• Book discusses the effects of too much Se M.L.
  Jackson has been studying the deficiencies
• Plants do not require Se but do take it up
  (that's how we get it)
• Plants will continue to grow nicely when Se is
  depleted in soils
• In China, areas of low Se correlate well with
  cancer and heart trouble
• In US, our food travels more and we have less Se
  deficiency

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• Toxic elements in soils
• Mo excesses occur naturally
• Inhibit Cu uptake and growth
• Fig 17-11

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• Radionuclides
• Isotopes (extra neutrons) which are unstable and
  emit radiation in the form of neutrons alpha
  (He), beta (electron) and gamma (x-ray)
• Not all isotopes are radioactive (for example,
  15N)
• Isotopes are responsible for the deviation from
  integers on atomic weight (e.g., K 39.1)
• Half life time for half radiation to decay.
  Examples, on p. 20

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• Radionuclides
• Atomic bomb testing covered the earth with
  radionuclides, 14C is used today as a tracer and
  is about 118 of normal now.
• Nevada leukemia 2.4 X normal from Nevada Test
  site, according to the book Chernobyl had 18 X
  thyroid cancers from 131I.
• ?Radioactive wastes are very difficult to
  impossible to clean up if half life is short,
  wait. If not, tough luck
• ?Radon gas decay daughter of radium. Naturally
  occurring in some soils

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• Soluble Salts Read it alluded to in previous
  lectures
• Sediments as pollutants
• ?We discussed earlier
• ?Tahoe Example P is largely attached to
  sediments.
• This is the main way in which P enters surface
  waters because it does not leach.
• Also the main reason P is usually limiting to
  surface waters.

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• Acid Rain
• Sulfuric (mainly coal source) and nitric (mainly
  auto source)
• Much overblown issue in the past book still
  regurgitates what was being said 10-15 years ago
• Truth was much less problem than that, although
  there were cases especially locally
• Acidification of soil solution and surface waters
  - two mechanisms
• Pass mobile anion through acid soil
• Acidify soil

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Acidifying the soil (moving from left to right)

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Mineral acid anion through an acid soil (moving
from left to right)
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• Acid Rain
• In either case, mobilized Al accumulates on the
  gills of fish and kills them and/or is toxic to
  roots of some trees
• Mitigation strategies for the two effects differ
• If the former case (acidifying the soil), you
  must lime the soil or wait a very long time. Even
  then, it may never happen
• In the latter case (mobile anion through already
  acid soil), recovery is very rapid once the anion
  is removed

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• Acid Rain
• Since 1990, S emissions in North America and
  Europe have declined substantially
• Lakes in Adirondacks have now started to show
  recovery
• But Asia is on the upswing

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Driscoll, C.T., K.M. Driscoll, K.M. Roy, and M.J.
Mitchell. 2003. Chemical response of lakes in the
Adirondack region of New York to declines in
acidic deposition. Env. Sci. Tech. 37 2036-2042.
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• Acid Rain
• Forest decline
• Major forest decline noticed in Germany in 1980's
  and in red spruce in the NE US at the same time
• Acid rain was in style and was blamed
• We now know that forests in Europe were growing
  faster, despite their appearance, than ever
  before - probably due to N and CO2 (Kauppi et al,
  1992 and more)

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• Acid Rain
• Forest decline
• Decline that did occur in local areas in Europe
  was linked to Mg and K deficiencies and frost
  shock in some cases
• Mg and K deficiencies due to years of land use -
  litter raking, etc.
• Symptoms disappeared in mid 90's - probably
  weather triggered.

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• Acid Rain
• Forest decline
• Red spruce decline in the NE US was finally
  attributed to climate
• Soil acidification has been noted here and there
  and in some cases attributed in part to acid rain
• However, uptake by trees is also a major factor

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• Soil C and global climate change
• The book totally ignores the role of soils in
  this!!!
• Buildup of greenhouse gases (GHG's) (CO2, N2O,
  CH4) have increased over last 100 years
• Gases allow short wave radiation through and
  absorb and re-emit long wave - like greenhouse
• CO2 is the major culprit
• Atmospheric CO2 levels have been increasing since
  the mid 1800's

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Keeling and Whorf, 2004 (http//cdiac.esd.ornl.go
v/trends/co2/sio-mlo.htm)
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www.des.state.nh.us/ard/climatechange/science.htm
Source U.S. Global Climate Change Research
Program (2000)
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Long wave radiation - absorbed by GHG's and
reflects back to earth
Sun
Short wave radiation -penetrates atmosphere
Earth
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• Soils and the global carbon budget
• Note that soils are a very large C pool
• Small changes in soils could have very large
  effects
• Note very large numbers for photosynthesis,
  litterfall, and decomposition compared to fossil
  fuels
• Are they really in balance?
• Reasons for CO2 increase
• Fossil fuel combustion is considered the major
  cause
• Loss of C from soils due to agricultural
  settlement
• Fire?
• Reduction in forest cover
• Still going on in tropics
• This has reversed in North America since 1900

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• Soils and climate change- speculation on mesic
  soils
• Warming mesic soils can cause changes in several
  interacting processes
• Increased decomposition of soil organic matter
• Greater CO2 release worsening global C problem
• Short-term increases in N availability because of
  1., which can in turn cause more C in vegetation,
  mitigating against global C problem
• Which process will have the greatest effect?

CO2
CO2
Warming

• Lower soil C content
• Greater vegetation
• C content

Increased decomposition and N mineralization
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The Global Carbon Cycle Warming
Effects? Gigatons, or 1015 g
Fossil Fuels 6-7
Atmosphere 750 Annual Increase 3.2
Fire 2-5
Respiration 60
Photosynthesis 120
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90
90
Decomposition 60
Litter 60
Soil and Litter 1500
Terrestrial Biota 610
Oceans 38,000
Net veg destruction 0.9
Burial 0.1
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• Soils and climate change speculation on arid
  soils
• Warming arid soils can cause changes in several
  other interacting processes
• Increased water stress
• Reduced decomposition reduced soil CO2 releas
• Reduced N mineralization
• Reduced plant growth
• But changes in precipitation in arid soils is
  more important and much less predictable!

CO2
CO2
CO2
CO2
Warming

• Lower soil C content
• Lower vegetation
• C content

Increased water stress, reduced decomposition and
N mineralization
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Effects of land management on soil C
Cultivation nearly always results in a loss of
soil C
From Johnson, 1992
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Effects of land management on soil C
Forest harvesting followed by replanting has
little effect on soil C (from Johnson and
Curtis, 2001)
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• Global C budget the bottom line
• Soils are a very large pool, greater than
  vegetation and atmosphere.
• Soils have the potential to either exacerbate or
  help the problem.

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• The End
• Final exam 18 Dec, 730 930
• Either second exam(100 points) or Comprehensive
  final (200 points)
• Review Session Wednesday 13 Dec, 800