Chapter 15: Pollution of Soil, Air, and Water

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Chapter 15 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
• 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 of ag soils

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• Plant nutrients that are also pollutants
• 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
• Sometimes N is limiting in pristine lakes and
  streams
• Tahoe example formerly N limited, now N and P.
• For non-point source pollution, this is a big
  problem in terms of measuring inputs and who to
  blame.

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15-2
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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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• Eutrophic, or dead zone in the Gulf of Mexico
• From the Mississippi delta to Texas coast,
  nutrient-rich waters from the river periodically
  create O2 starvation and kill fish.
• Pollutant sources
• Over-fertilization
• Sewage
• Manure

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15-3
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15-4
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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 15-1)
• However, the problem still is NO3- leaching and
  also heavy metal bioaccumulation (especially Cd)
  (Table 15-2)

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Douglas fir growth response to biosolid
application
dnr.metrokc.gov/wtd/biosolids/Forest.htm
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Table 15-1
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Table 15-2
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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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• Other wastes
• Municipal garbage recycling on the increase
• Food processing waste compost, biodiesel?
• Industrial some nasty things like PCBs

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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 15-9
• 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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15-9
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• Pesticide problems and extent of pollution
• Resistance must constantly change to meet this
  challenge
• Groundwater pollution lt5 usually lost to
  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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• Heavy metals, toxics 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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Hg pollution a global problem guest lecture by
Mae Gustin
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• Natural toxins grazing animals
• Locoweed
• Halogeton
• Larkspur

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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)
• A huge issue in the 1970s and 1980s
  transboundary pollution from Europe to
  Scandinavia, US to Canada
• Truth was much less problem than that, although
  there were cases especially locally

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SO2 1/2O2 ? SO3 H2O ? H2SO4 ? 2H SO42-
www.maltaweather.info/acid.jpg
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• Acid Rain
• Acidification of soil solution and surface waters
  - two mechanisms
• Pass mobile anion through acid soil (naturally
  acid or not does not matter)
• Acidify soil

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Acidifying the soil Occurs very slowly
BC any base cation
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Mineral acid anion through an acid soil Occurs
very rapidly
C any cation, base or acid A- mineral acid
anion such as SO42- or NO3-
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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 one the mobile
  of 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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Fraser fir mortality due to aphids in S.
Appalachians was linked to weakened trees from
acid rain (a weak link at best) http//green.n
ationalgeographic.com/environment/enlarge/mitchell
acidtrees.html
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• Forest Decline in Europe? Not really.
• In 1992, Kauppi et al reviewed mensurational data
  for forests in Europe.
• On average, forest growth was increasing, not
  decreasing, between 1970 and 1990, when all the
  hand wringing about acid rain and forest decline
  was going on
• That trend continues today
• Possible causes
• Better silviculture
• Nitrogen deposition
• Elevated CO2

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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
• There is much more to this issue that pertains to
  soils than is given in the book!
• 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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Long wave radiation - absorbed by GHG's and
reflects back to earth
Sun
Short wave radiation -penetrates atmosphere
Earth
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• The global carbon budget
• Note that fossil fuel emissions are less than
  accumulation in the atmosphere
• Implies a sink for CO2 on earth land, ocean, or
  both
• Dissolved CO2 in the ocean?
• Biological uptake in the ocean?
• Reforestation of eastern North America?
• But what will increasing fire do to this trend?

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Partition of Anthropogenic Carbon Emissions into
Sinks
2000-2006
45 of all CO2 emissions accumulated in the
atmosphere
Atmosphere
The Airborne Fraction
The fraction of the annual anthropogenic
emissions that remains in the atmosphere
55 were removed by natural sinks
Land removes _ 30
Ocean removes _ 24
Canadell et al. 2007, PNAS
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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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Perturbation of Global Carbon Budget (1850-2006)
2000-2006
fossil fuel emissions
7.6
Source
deforestation
1.5
CO2 flux (Pg C y-1)
atmospheric CO2
4.1
Sink
land
2.8
ocean
2.2
Time (y)
Le Quéré, unpublished Canadell et al. 2007, PNAS
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• Soils and the global carbon budget Histosols
  and Gelisols
• Peat soils (Histosols and Gelisols?) are
  thought to contain at least 400 to 600 Gt carbon
  of the 1500 total.
• What will warming do to these soils? What does it
  imply for feebacks on global C cycling and
  climate change?
• Arctic soils thought to contain much more C than
  previously known
• http//www.sciencedaily.com/releases/2005/12/05120
  5162830.htm

(Jonathan Adams, Environmental Sciences
Division, Oak Ridge National Laboratory, TN
37831, USA http//www.esd.ornl.gov/projects/qen/c
arbon2.html).
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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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Warming effects on arctic soils Increased
vegetation growth does not offset soil C loss in
some experiments http//www.scienceagogo.com/news
/20040912202826data_trunc_sys.shtml
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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
92
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
• 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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• Soil C changes are linked to N!!
• The focus on soil C has lead those unfamiliar
  with soil science to neglect the fact that
  changes in soil C must be accompanied by changes
  in soil N!
• Nitrate leaching or denitrification for loss
• Atmospheric deposition or N fixation for gain
• Soil CN ratios typically range at from 10 to 40
  thus, a 1000 kg ha-1 change in soil C must be
  accompanied by a 25 to 100 kg ha-1 change in N to
  stay within normal, observed ranges.
• Not trivial!