RAIN WATER VS OCEAN WATER

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RAIN WATER VS OCEAN WATER RAIN WATER is
naturally acid due to the solubility of CO2 in
water. (also O2 N2) CO2(g) H2O(l) ??
H2CO3(ag)
Carbonic Acid PH 5.6 (normal range 5 to
7 pH) The natural acidity of rain water
promotes the erosion of land, the formation of
underground caves, and maintenance of the
nitrogen cycle.
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Rain Water vs. Ocean Water OCEAN WATER also
contains carbonic acid but instead of reverting
back into CO2 H2O, it is neutralized by
dissolved alkaline substances into CaCO3. pH
8.2 The products of neutralization end up on
the ocean floor as insoluble solids. H2CO3
CaCO3 ? Ca (HCO3)2 ? The ocean acts as a sink and
does not allow CO2 to be released back into the
atmosphere.
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ACID RAIN Natural rain contains some dissolved
CO2 gas from the atmosphere, making rain slightly
acidic 5.6 pH. Acid rain refers to rain that
has a pH lower than natural rain. pH ? 5.6 In
the US, Acid rain has a pH ? 4 due to dissolved
SOX and NOX gases. Different regions of the U.S.
experience different acid rain.
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Where is it a problem?

• Acid rain is a problem in eastern America
  because many of the water and soil systems in
  this region lack natural alkalinity - such as a
  lime base - and therefore cannot neutralize acid
  naturally.

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What exactly is acid rain?

• "Acid rain" is a broad term used to describe
  several ways that acids fall out of the
  atmosphere. A more precise term is acid
  deposition, which has two parts wet and dry.

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Wet deposition

• Wet deposition refers to acidic rain, fog, and
  snow. As this acidic water flows over and through
  the ground, it affects a variety of plants and
  animals. The strength of the effects depend on
  many factors, including how acidic the water is,
  the chemistry and buffering capacity of the soils
  involved, and the types of fish, trees, and other
  living things that rely on the water.

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Dry Deposition

• Dry deposition refers to acidic gases and
  particles. About half of the acidity in the
  atmosphere falls back to earth through dry
  deposition. The wind blows these acidic particles
  and gases onto buildings, cars, homes, and trees.
  Dry deposited gases and particles can also be
  washed from trees and other surfaces by
  rainstorms. When that happens, the runoff water
  adds those acids to the acid rain, making the
  combination more acidic than the falling rain
  alone.

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How does Acid Rain happen?

• Acid rain occurs when these gases react in the
  atmosphere with water, oxygen, and other
  chemicals to form various acidic compounds.
  Sunlight increases the rate of most of these
  reactions. The result is a mild solution of
  sulfuric acid and nitric acid.

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ACID RAIN pH lt 5 - created by airborne
pollutants (SOx, NOx,

particulates,
etc.) absorbed by atmospheric moisture. 2SO2(g)
O2(g) ? 2SO3(g) SO3(g) H2O(l) ? H2SO4(ag) -
sulfuric acid is much stronger than carbonic
acid - sulfuric acid eventually corrodes
metals, paints and other exposed substances
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SOx AS AIR POLLUTANT
S O2 ? SO2 or 2H2S 3O2 ? 2SO2
2H2O SO2 1/2O2 ? SO3 SO3 H2O ? H2SO4
(acid rain)
Produces Aerosols which are suspensions of tiny
droplets of liquid in a gas. A suspension of
solid in a liquid is called a colloid. General
Information about H2SO4 - dissociates into H,
HSO4- SO42- a strong acid and a weak acid -
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SOX Toxicity SO2 toxic to plants 0.3 ppm for 8
hr causes severe damage to plants (choking
effect) 1 hr - 5ppm - severe construction of
brochial tubes H2SO4 - acid is dangerous
buildings, art, and statues CaCO 3 (marble)
H2SO4 ? CaSO4 CO2 H2O, Fe H2SO4 ? FeSO4
H2 CaCO3 - limestone SiO2 Al2O3 clay
cement CaSO4 2 H2O H2SO4 - dangerous to
plants, animals, oceans, forests and crops
Acid rain changes the pH of lakes. This acid has
a strong affinity for H2O that is, it removes
H2O from organic materials or dehydrates.

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SOx
NATURAL SOURCES - geothermal emission -
biological processes (marine anaerobic
bacteria) - volcano eruptions HUMAN SOURCES -
combustion of fossil fuels (autos, electricity,
power plants, space heating, industry) - non
combustion sources metal ore smelting
plants HgS O2 ? Hg SO2 (CuS,
Ag2S, ZnS, PbS) industrial plants (81,000
tons per day of SO2) wine industry
(compounds used to kill fungi in barrels)
preservatives in fruit juices bleaching
agents paper production coal
industry 4FeS2(s) 1102 ? 2Fe2O3(s) 8SO2
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H2SO4 AS A WATER POLLUTANT Acid Mine
drain Pyrite (FeS2) occurs along with coal,
after mining operations, pyrite is exposed to
moist O2 (weather) 4 FeS2 2 H2O 15 O2 ?
Fe2(SO4)3 2H2SO4 Unless controlled, acid
drainage from coal mines can pollute streams,
killing fish and other wildlife. In North East
US 62 is H2SO4 32 HNO3
6 HCl
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NOx
NATURAL SOURCES - 80 air is composed of N2 so
actions like lightning storms produce Nox -
bacterial action HUMAN SOURCES - incomplete
combustion of air - production of plastics,
nylon, fertilizers and explosives.
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NOx AS AIR POLLUTANT
Heat N2 O2 ? 2 NO (radical) NO
1/2 O2 ? NO2 3NO2 H2O ? 2 HNO3 NO
Acid rain
NO2 is a brown toxic gas, affects respiratory
system, chokes damages lung tissue. Nitric
Acid is a problem due to the abundance of N2 in
air. It readily reacts with metals to produce
NO2 which continues the cycle. Fe 6HNO3
? Fe (NO3)3 3NO2 3H20 3NO2
H2O ? 2HNO3 NO
cyclic
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Table 6.1 Estimated Global Emissions of Sulfur
and Nitrogen Oxides (in millions of metric tons
per year) Source SO2 Nox
Natural Oceans 22 1 Soil and plants
2 43 Volcanoes 19 Lightning __
15 Subtotals 43 59 Anthropogenic Fossi
l Fuels combustion 142 55 Industry (mainly
ore smelting) 13 Biomass burning 5
30 Subtotals 160 85 TOTALS 203
144 Sources Data from Spiro, et al.
Global inventory of sulfur emissions with 1º X
1º resolution in Journal of Geophysical
Research, 97, No. D5, 6023, 1992. United States
Environmental Protection Agency, Air Quality
Criteria for Oxides of Nitrogen,
EPA/600/8-91/04aA.
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What are acid rain effects?

• damage to forests and soils, fish and other
  living things, materials, and human health
• reduces how far and how clearly we can see
  through the air
• Acid rain does not only effect organisms on
  land, but also effect organisms in aquatic
  biomes.  Most lakes and streams have a pH level
  between six and eight.  Some lakes are naturally
  acidic even without the effects of acid rain.

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Effects on human

• causes toxic metals to break loose from their
  natural chemical compounds
• toxic metals that might be absorbed by the
  drinking water, crops, or animals that human need