BIOGEOCHEMICAL CYCLES

Presented by Dr. Edilberto G. Tripoli

FEU – Institute of Technology

/Evapotranspiration

/Percolation

NITROGEN CYCLE

PHOSPHOROUS CYCLE

SULFUR CYCLE

Steps in Oxygen Cycle

Surface 1. Photosynthesis 2. Respiration

Subsurface 3. Weathering 4. Burial

Glucose breakdown without oxygen (anaerobically) to produce methane and carbon dioxide

C6H12O6 3CH4 + 3CO2

Combustion/Metabolism Reaction

• During combustion/metabolism oxygen is used and carbon dioxide is a product. The whole purpose of both processes is to convert chemical energy into other forms of energy such as heat.

Transformation of nitrogen compound in the soil

Nitrification

a) 2NH4+ + 3O2 2NO2

- + 2H2O + 4H+ (by Nitrosomas)

b) 2NO2- + O2 2NO3

- (by Nitrobacter)

Denitrification

4NO3- + C6H12O6 2N2 + 6H2O

• Reaction of phosphorus with air: White phosphorus glows in the dark when exposed to damp air in a process known as chemuluminescence. White phosphorus must be handled with great care. It spontaneously ignites in air at about room tetraphosphorus decaoxide.

P4 (s)+502 (g) P4010(s)

Reaction of phosphorus with the halogens: white phosphorus, P4, reacts vigorously with all the halogens at room temperature to form phosphorus trihalides. So, it reacts with fluorine, chlorine, bromine, and iodine, to form respectively phosphorus (III) fluoride, phosphorus (III) chloride, phosphorus (III) bromide, and phosphorus (III) iodide. P4(s) + 6F2(g) 4PF3(g) P4(s) + 6Cl2(g) 4PCl3(I) P4(s) + 6Br2(g) 4PBr3(I) P4(s) + 6I2(g) 4PI3(g)

Sulfur dioxide dissolves in water, like carbon dioxide, hydrolyses in a series of equilibrium reaction

SO2 (g) + H2O SO2 · H2O

SO2 · H2O H+ + HSO3-

HSO3- H+ + SO3

2-