Biogeochemical Cycles Sulfur What is Sulfur n Sulfur

Biogeochemical Cycles Sulfur

What is Sulfur? n Sulfur – Naturally found in earth – At room temp. , it is a solid – Present in proteins, amino acids, vitamins, and enzymes, necessary for plants and animals – Often reacts with hydrogen creating hydrogen sulfide § Can dissolve in water § With metals in water, forms metal sulfides; sulfates in air Sulfur

Sulfur Cycle In ground: – most found in rocks, salt in earth, or as sediment at bottom of ocean – Found as SO 4 -2 (sulfates) n In atmosphere: – sulfur dioxide (SO 2) comes from volcanoes – hydrogen sulfide (H 2 S) comes from volcanoes and anaerobic decomposers in bogs and swamps – Ammonium sulfate (NH 4)2 SO 4 enters the ground and plants absorb it, or is left by acid deposition (fog or precipitation) n

Sulfur Cycle n Sulfur is transferred into biosphere then back into ground, or from ground to atmosphere – Microorganisms turn it into H 2 S (gas) – Oxidized in atmosphere to SO 2, and then to H 2 SO 4 (an acid) with water contact

Driving Force n Driven by: – constant addition of sulfur to environment by earths interior (geosphere) – Human disturbance, addition of sulfur to atmosphere, (also dug up from environment) – Natural processes (biological, hydrological, due to sun’s energy) – Plant uptake, microbes (Desulfovibrio sp. or Desulfotomaculum sp. ) (“A Black Smoker”)

Percentages of Sulfur n Most sulfur in particulate form – Therefore it is a sedimentary cycle – Very short residence time in atmosphere (1 -2 days) – Even in atmosphere, found as aerosols (<1 micrometer), not gas usually – In atmosphere, way less than 1% – Its around. 000314 percent – 90 -95% SO 2 from power plants and factories

Human Effect When mine ores, sulfur/sulfides released into soil (“Arial”) n Combustion of fossil fuels n – Release of(“Sulfur SO 2, Mining”) causes acid rain, increases amount already present – 28% of sulfur in rivers from pollution, mining, erosion, etc. – Help move cycle but also upset balance- too much S means acid rain – Hydrodesulphurization (refine hydrocarbons)- surplus of S in Alberta Canada