Group 5

Rey D. Abelita

William Arcilla

Jesher Arsenio

Emma Fernandez

Issa Maslog

SULFUR CYCLE

AN INTRODUCTION – WHAT SULFUR IS

• Sulfur (Sulphur in UK) is a member of Group VIA-> same as oxygen. Its name was derived from soufre, an Old French word which means “to burn”.

• Antoine Lavoisier-> Helped convinced the Scientific Comm. That Sulfur = an element not a compound.

• Oxygen unlike Sulfur, is in the second period, hence, no d orbitals.

• The d orbitals allows additional electrons to be accommodated = six bonds instead of Oxygen’s two bonds.

AN INTRODUCTION – SULFUR AND ITS IMPORTANCE• In humanity, it is produced most specially in industries where it is used as

solvent, catalyst and reactant to produce different organic compounds. (H2SO4)

• In ecosystems as a whole, no matter what form (SO2, H2SO4, H2S), Sulfur in its soluble form ===>plants ==>series of metabolic processes. ( starts photosynthesis) ---> Sulfur-bearing amino acids.

• Sulfur -> Helps retain cellular structure; provides chemical links that creates collagen and keratin; Activator of minerals and vit.;

• Sulfur (in protein assembly and structure) bonds-> known as disulfide bonds-> plays an important role.

• Sulfur is also an important component of diff. enzymes such as coenzyme A, and of standard amino acids such as Cysteine.

• Producers -------> Consumers [Sulfur in Amino Acids]

Cysteine Coenzyme A

THE SULFUR CYCLE

• The sulfur cycle gaseous and sedimentary phases.

• As an introductory note -> The long term sedimentary phase, Sulfur is tied up in organic and inorganic deposits, released by weathering and decomposition.

• The gaseous phase permits the circulation on a global scale. [to be expound later]

• Their main difference is in their exchange sites/ sites of occurrence. Sedimentary phase is mainly on the Earth’s surface (i.e rocks, sediments, etc.) while the gaseous form is on the atmosphere.

• Reservoir: Oceans (aerosol/SO4) ===> (CH3)2S, Atmosphere (Sulfur Dioxide, Hydrogen Sulfide and Sulfates) , Organic and Inorganic Deposits (Sedimentary Rocks, Igneous Rocks such as pyrite or FeS2.)

• Exchange Pools: Hot Springs, Geysers, Surfaces of the Ocean,, Fossil Fuel Combustion, Volcanoes, Decomposing Matter

SEDIMENTARY AND GASEOUS

• Sedimentary cycle

• Weathering of rock and leaching of its minerals, transport, deposition and burial.

• Gaseous Cycle

• A biogeochemical cycle with the main reservoir or pool of nutrients in the atmosphere and ocean

SULFUR ENTERS THE BIOSPHERE THROUGH

• Natural Activity

Weathering of rocks and decomposition

Carried through terrestrial environments

in salt solution.

PlantsConsumers

SULFUR ENTERS THE ATMOSPHERE THROUGH

• Natural ActivityVolcanic eruptions, gases released by

decomposition

• Human ActivityBurning of fossil fuels, acidic drainage from

mines

Enters atmosphere as H2S and reacts with oxygen to form SO2

SO2 is soluble in H2O

Acid rain (H2SO4)

plantsconsumers

Death of consumers

Sulfur to the atmosphere

soilPonds, lakes, seas and oceans

Different kinds of bacteria process this

sulfur

Non-photosynthetic photosynthetic

Colorless sulfur bacteria

Purple bacteria

Green bacteria

Sulfur

Iron

Ferrous sulfide (FeS2)

Sulfur from the oceans

Released in the atmosphere as Dimethyl sulfide

((CH3)2S )

Go back to the atmosphere by bacteria fixation, or sea

sprays

GLOBAL SULFUR CYCLE

Gaseous phase of sulfur cycle circulates on a global scale.

300 x 1012 grams/year

Each flux is shown in units of 1012 grams

S/year

Atmosphere

Sulfur dioxide  (SO2) Hydrogen sulfide (H2S)

Sulfate Particles

Sulfate particles become part of dry deposition. (DRYFALL)

Gaseous forms combines with moisture and are transported in precipitation.(WETFALL)

Oceans Large sources of aerosols that

contain sulfate(SO4) Most are redeposited in oceans

as precipitation and dryfall. Dimethylsulfide((CH3)2S) major

gas emitted from oceans Estimated 16 x1012 grams

S/year is emitted

Freshwater wetlands and anoxic soils Hydrogen sulfide (H2S)

Forest fires 3 x 1012 grams/year

Marine Plants 130 x 1012 grams/year

Volcanic activity 10 x 1012 grams S/year

Eruption of Mt.

Pinatubo (1991)

release on the order of

5 to 10 x 1012 grams

Sulfur

Adding all anaerobic

oxidation of organic matter

200 x 1012 grams/year

HUMAN INTERVENTION IN

THE SULFUR CYCLE

Since the Industrial Revolution, human activities have contributed to the amount of sulfur that enters the atmosphere, primarily through the burning of fossil fuels and the

processing of metals.

What exactly are we doing? Burn sulfur-containing coal and oil to

produce electric power. Refine sulfur-containing petroleum to

make gasoline, heating oil, and other useful products.

Convert sulfur-containing metallic mineral ores into free metals such as copper, lead, and zinc.

Mining erosion (exposure of mineral sulfides)

Emissions from these, along with nitrogen emissions, react with chemicals in the atmosphere

SULFATE SALTS ACID RAIN

Damage the natural environment (affects both plants and animals) as

well as man-made environments weathering/corrosion of buildings

Dry Deposition

Gaseous sulfur dioxide component of the sulfur cycle and the nitrogen oxides of the nitrogen cycle mix in the atmosphere. Some of this mixture returns to the Earth as particulate matter and airborne gases, known as dry deposition

Effects

For humans, it irritates the respiratory tract, from the nose then moves into the lungs and attacks sensitive tissues.

High concentrations have caused a number of air-pollution disasters characterized by higher than expected death rates and increased incidences of bronchial asthma.

Wet deposition Major portion of D.D. is transported away from the source in a

direction influenced by the atmospheric circulation. During their transport, sulfur dioxide and nitrogen dioxide and their oxidative products participate in complex reactions involving hydrogen chloride and other compounds, oxygen and water vapor.

These reactions dilute solutions of strong acids (nitric and sulfuric acids). Eventually they come to earth in acidic rain, snow and fog.

Sulfur dioxide combines with atmospheric moisture to form sulfuric acid which falls on land and water and forms

significant part of acid rain

Effects Causes major damage to vegetation in areas

surrounding the source of emission Injures or kills exposed plants Acidic aerosols present during periods of fog, light

rain and high relative humidity together with

moderate temperatures do the injury. External surfaces of the leaves absorb the aerosols. When dry, leaves and needles take up sulfur dioxide through the stomata. In the leaf, the sulfur dioxide rapidly reacts with moisture forming sulfuric acid.

Symptoms to sulfur damage are a bleached look to deciduous

leaves and red-brown needs on conifers, partial defoliation and

reduced growth.

Nutrient deficient soils Acid rain low pH level of soil nutrient

leaching reduce solubility and availability (macronutrients) and high availability of micronutrients (Al, Fe, Manganese toxicity) inhibits fungal and bacterial activity reduce humus production, mineralization and fixation of nutrients

Acid Rain Low pH level of soil

Nutrient leaching

Low: Macro

High: MicroHigh toxicity

Affects activity of

microorganisms

Reduced humus production,

mineralization and nutrient fixation

Nutrient deficient

soils

In water…

Sulfate and nitrogen ions replace bicarbonate ions, pH declines, and the concentration of metallic ions, especially aluminum, increases.

Although adult fish and some aquatic organisms can tolerate high acidity, a combination of high acidity and high level of aluminum can kill them.

Eggs and larvae of frogs and salamanders are sensitive to acidic water. Cause decline in amphibians/increased rate of mortality.

Acidic waters – toxic to invertebrates either killing them directly or interfering with calcium metabolism (causing crustaceans to lose the ability to recalcify their shells after molting)

Corrosive