Biogeochemical Cycles: Sulfur

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Biogeochemical Cycles Sulfur

• By John Tortella and Larry Choi

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What is a Biogeochemical Cycle?

• The pathways through which minerals cycle
  throughout both the biotic (biosphere) and
  abiotic (lithosphere, atmosphere and hydrosphere)
  ecospheres of the earth.

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What is Sulfur?

• It is element number 16 on the periodic table,
  denoted with the symbol S
• It is a non-metal and at standard temperature
  and pressure (STP), Sulfur is a bright yellow
  crystalline solid.
• It is found in every living cell and two amino
  acids cysteine and methionine, making it an
  essential element for life.
• It's a component of vitamin B1 and biotin, the
  antioxidant glutathione, the anticoagulant
  heparin, and coenzyme A, which drives energy
  production in cells. Sulfur is also a part of the
  biological cement which forms skin, hair, nails,
  and the cartilage that shapes the nose and pads
  in joints.
• It is present in the atmosphere mainly from the
  burning of fossil fuels and volcanic emissions.

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Sulfur Cycle
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Pathway of Movement

• Sulfur is emitted into the atmosphere primarily
  through volcanoes and energy production (through
  the burning of coal and other fossil fuels)
• Through acid rain containing sulfuric acid,
  sulfur enters the ocean (Hydrosphere) and soil
  (Lithosphere).
• From the soil, plants absorb sulfur, in turn, the
  plants are consumed by animals (meaning the
  sulfur returns to the Biosphere).
• When plants and animals die sulfur is returned
  into the soil through decomposition.
• The sulfur eventually makes its way back into
  rocks and the magma erupted by volcanoes or is
  extracted by humans.

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Common Sources of uptake of Sulfur for Humans

• Egg yolks, garlic, cauliflower, cabbage,
  horseradish, meat, fish, and onion.

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Chemical Reactions Involved

• Most of the sulfur emissions in the atmosphere
  come from the burning of coal or other petroleum
  fossil fuels in the form of sulfur dioxide gas
  (SO2). The SO2 reacts with water to form sulfuric
  acid, which falls as acid rain. These
  concentrations are usually greatest in industrial
  areas and are affected by wind and weather
  patterns.
• Incomplete combustion of a Hydrocarbon Fuel
  Air -gt Heat Water Carbon Dioxide Sulfur
  Dioxide
• Chemical processes involving Sulfur in the
  atmosphere can also help to produce hydrogen

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Organic Reservoirs

• Plants
• Soil
• Animals
• Fossil Fuels

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Inorganic Reservoirs

• Freshwater
• Salt Water/Oceans
• Sediment
• Volcanoes

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Impact of Human Intervention

• The burning of coal, natural gas, petroleum and
  other fossil fuels has led to significant
  increases in the amount of sulfur in the
  atmosphere.
• Due to human intervention, sulfur is being
  drilled, pumped and burned at a steadily
  increasing rate, increasing sulfate
  deposition/pollution. Otherwise, without human
  impact, sulfur stays in rocks for millions of
  years until it is extracted by tectonic events,
  eventually becoming released through erosion and
  other weathering processes.

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Effects of the Increased Sulfur in the Atmosphere

• Burning of fossil fuels ultimately leads to acid
  rain which is bad because its low pH (of about 4)
  can cause damage to surfaces on the earths
  surface.
• Benefits are that Sulfur has various great
  medicinal uses and is essential to the health of
  all living things.